Method for preparing 3,4-methylenedioxypropiophenone

Abstract

The present invention relates to a process for the preparation of 1-(1,3-benzodioxol-5-yl)-1-propanone, comprising the step of reacting 3,4-dimethylenedioxybenzene with propionic anhydride in the presence of a bulk or supported catalyst, the catalyst being selected from the group of sulfonated crosslinked divinylbenzene resins, sulfonated crosslinked divinylbenzene resins partially exchanged with iron, zinc or gallium, perfluorinated sulfone resins and perfluorinated sulfone resins partially exchanged with iron, zinc or gallium, the catalyst having an average particle size of 1 μm to 300 μm, preferably 1 μm to 180 μm, more preferably 1 μm to 100 μm, as measured by DLS (Dynamic Light Scattering) or by a granulometer. The process is advantageously carried out in a continuous manner, with stoichiometric ratios between the reagents.

Description

Technical Field

[0001] The present invention relates to a novel and inventive method for preparing 3,4-methylenedioxypiophenone, also known as 1-(1,3-benzodioxol-5-yl)-1-propanone, as represented below.

Chemical Formula

[0002] Such a method is an improved commercially feasible method that functions using a heterogeneous catalyst under solvent-free conditions.

Background Art

[0003] Alkylenedioxybenzene derivatives are very important in the fields of medicine, pesticides, biocides, performers, and food due to their applications as end products or intermediates for desired end products.

[0004] For example, compounds having insecticidal activity containing a benzo[1,3]dioxole group are described in a number of publications. Safrole and isosafrole are used in performary, and specifically, isosafrole is used in the synthesis of piperone (benzo[1,3]dioxole-5-carboxaldehyde) used for manufacturing fragrances and flavorings.

[0005] Among aryl ketones, 3,4-methylenedioxypiophenone, also known as 1-(1,3-benzodioxol-5-yl)-1-propanone, is an important compound and intermediate in the above fields.

[0006] European Patent No. 1140894 describes a method for the preparation of 5-(α-hydroxyalkyl)benzene[1,3]dioxole, which provides a preparation process for acyl derivatives. Specifically, the described method includes a first step a) of preparing benzene[1,3]dioxole by reacting 1,2-dihydroxybenzene and methylene chloride in a suitable solvent, followed by step b) of reacting the thus obtained benzene[1,3]dioxole with propionic anhydride in the presence of perchloric acid as an acylation catalyst. In this specification, the proposed acylation catalysts were ZnO, ZnCl2, FeCl2, FeCl3, FeSO4, Fe2(SO4)3, FeO, Fe2O3, H3PO4 and HClO4.

[0007] The drawbacks associated with this type of catalyst are reported in International Publication No. 2020 / 174271. In this international application, it is emphasized that all of these catalysts are toxic and corrosive, generally producing a large amount of hydrochloric acid in the effluent, resulting in the generation of a large amount of sludge, thus having a high degree of process contamination and being harmful to the environment.

[0008] Therefore, this same document proposes the use of alkylsulfonic acids for the easy separation of unreacted carboxylic acids and unreacted substrates that can be reused.

[0009] In Example 14 of International Publication No. 2020 / 174271, 3,4-methylenedioxypiophenone is prepared by first introducing methanesulfonic acid and propionic anhydride, and then adding 3,4-methylenedioxybenzene after cooling. The reaction is maintained at 0°C to 5°C for 4 hours. After the reaction is completed, the reaction mass is diluted with water, and the obtained 3,4-methylenedioxypiophenone and unreacted 3,4-methylenedioxybenzene are extracted with toluene. The toluene layer is distilled to recover unreacted 3,4-methylenedioxybenzene, and 3,4-methylenedioxypiophenone with a gas purity of 98% is obtained. They also recover 63 g of propionic acid in the aqueous phase.

[0010] The method described therein teaches the use of an excess of homogeneous catalyst that needs to be recovered, namely methanesulfonic acid. In fact, this method provides an extraction in water / toluene in order to recover not only the desired product (in toluene) but also the catalyst. The inventors have studied this method and noted that the prior art method of WO 2020 / 174271 can obtain a higher 3,4-methylenedioxybenzene conversion rate considering the use of an excess of catalyst and very strict reaction conditions (4 hours at 0-5 °C), which occurred in the target product. Furthermore, it is well known that methylsulfonic acid is corrosive to metals and difficult to operate even when used industrially.

[0011] 3,4 which is an aromatic cyclic ether -me Methylenedioxybenzene is also known to be characterized by partial inactivation of the ring due to the bending of the -CH2- group at the bridging position for two oxygen atoms (FT-IR Investigation of Methoxy Substituted Benzenes Adsorbed on Solid Acid Catalysts”. J.Phys.Chem.C 2012, 116, 21308-21317. dx.doi.org / 10.1021 / jp3023056. “Anomeric Effect in 1,3-Dioxole: A Theoretical Study”. J.Am.Chem.Soc. 1996, 118, 9850-9854.). Therefore, strict and drastic conditions for acylation reactions as reported in WO 2020 / 174271 are usually required.

[0012] Furthermore, as reported in paragraph

[0016] of WO 2018 / 150230, the acylation of alkylenedioxybenzene compounds using conventional methods results in the synthesis of the final product with low yields and low purity because the -O-(CH2)m-O- rings of the reactants and products are very susceptible to cleavage under acidic conditions.

[0013] Accordingly, a first object of the present invention is to provide an economical, efficient and environmentally friendly method for preparing 3,4-methylenedioxypiophenone, also known as 1-(1,3-benzodioxol-5-yl)-1-propanone, thereby overcoming the drawbacks of the prior art methods, and secondly, to acylate it in good yield and purity.

Summary of the Invention

[0014] Despite the fact that heterogeneous catalysts, especially those based on sulfonated resins, are known to have very low activity in catalyzing the acylation of substrates, even when the substrate is a ring-opened heterocycle, for example, many difficulties in the acylation of anisole have been reported, as reported in “Perfluorinated nafion-modified SBA-15 material for catalytic acylation of anisole”, Applied Catalyst A: General F. Martinez, G. Morales, A. Martin, R van Grieken, the inventors have found that a heterogeneous catalyst with a specific particle size can not only increase the conversion rate from the starting material, i.e., 3,4 -me methylenedioxybenzene, but also increase its selectivity.

[0015] The inventors have actually found that a specific size of the particles / granules of a specific sulfonated heterogeneous catalyst surprisingly not only increases the active surface of the particles / granules of the heterogeneous catalyst, but also increases the selectivity, which usually decreases, due to the promotion of the consecutive reaction over the target product and the increase in the conversion of the aromatic substrate.

[0016] Accordingly, the applicant has surprisingly found a novel family of heterogeneous catalysts having a specific particle size that can be efficiently used for the acylation of 3,4 -me methylenedioxybenzene. These micronized catalysts not only increased the conversion, but also the substrate 3,4, which is a closed heterocycle -meThe selectivity of the acylation reaction on 1,3-dioxobenzene could also be enhanced.

[0017] Therefore, the present invention relates to a method for preparing 1-(1,3-benzodioxol-5-yl)-1-propanone, which includes a step of reacting with propionic anhydride in the presence of a bulk or supported catalyst, and the catalyst is selected from the group consisting of a sulfonated cross-linked divinylbenzene resin, a sulfonated cross-linked divinylbenzene resin partially exchanged with iron, zinc or gallium, a perfluorinated sulfone resin, and a perfluorinated sulfone resin partially exchanged with iron, zinc or gallium, and the catalyst has an average particle size of 1 μm to 300 μm, preferably 1 μm to 180 μm, more preferably 1 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer.

[0018] When the definition of "particle size" is used in the present invention, it means the average diameter of a single particle / granule of the final catalyst.

[0019] In an advantageous embodiment of the method of the present invention, the catalyst has an average particle size of 40 μm to 100 μm.

[0020] In a preferred embodiment, the catalyst is a supported catalyst supported on an oxide, preferably silica, zirconia, titania or alumina, more preferably silica.

[0021] Therefore, the inventors surprisingly noted that the use of a bulk or supported resin characterized by the presence of a sulfonic acid functional group showed specific catalytic activity in the acylation of 1,3-dioxobenzene with propionic anhydride. Furthermore, the inventors noted that when the catalyst was in powder form and used as both a bulk catalyst and a supported catalyst, the acylation process of 1,3-dioxobenzene was extremely efficient. -me The inventors noted that the use of a bulk or supported resin characterized by the presence of a sulfonic acid functional group showed specific catalytic activity in the acylation of 1,3-dioxobenzene with propionic anhydride. Furthermore, the inventors noted that when the catalyst was in powder form and used as both a bulk catalyst and a supported catalyst, the acylation process of 1,3-dioxobenzene was extremely efficient. -me The inventors noted that the acylation process of 1,3-dioxobenzene was extremely efficient.

[0022] Advantageously, the catalyst of the method of the present invention can be recovered, regenerated and recycled to restart the reaction.

[0023] The catalyst used herein is suitable for application in both batch and continuous flow apparatuses, resulting in the selective formation of 3,4-methylenedioxypropiophenone.

[0024] In an advantageous embodiment, the method for preparing 1-(1,3-benzodioxol-5-yl)-1-propanone is a continuous method.

[0025] From the above, it is clear that the method of the present invention is extremely efficient for the production of 1-(1,3-benzodioxol-5-yl)-1-propanone, which has operating conditions that are not as severe as those of the prior art methods, is not only environmentally friendly, but also has the potential to operate continuously.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0027] Accordingly, the present invention relates to a method for preparing 1-(1,3-benzodioxol-5-yl)-1-propanone, which comprises reacting 3,4 -me methylenedioxybenzene with propionic anhydride in the presence of a bulk or supported catalyst, wherein the catalyst is selected from the group consisting of sulfonated crosslinked divinylbenzene resin, sulfonated crosslinked divinylbenzene resin partially exchanged with iron, zinc or gallium, perfluorinated sulfonic resin, and perfluorinated sulfonic resin partially exchanged with iron, zinc or gallium, and the catalyst has an average particle size of 1 μm to 300 μm, preferably 1 μm to 180 μm, more preferably 1 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer.

[0028] When the definition of "particle size" is used in the present invention, it means the average diameter of a single particle / granule of the final catalyst.

[0029] In an advantageous embodiment of the process of the present invention, the catalyst has an average particle size of 40 μm to 100 μm.

[0030] The present invention relates to the presence of a bulk or supported catalyst selected from the group consisting of sulfonated crosslinked divinylbenzene resin, sulfonated crosslinked divinylbenzene resin partially exchanged with iron, zinc or gallium, perfluorinated sulfone resin, and perfluorinated sulfone resin partially exchanged with iron, zinc or gallium in the acylation reaction of 3,4 -me including the step of acylating 3,4 -dioxydibenzene, and the catalyst has an average particle size of 1 μm to 300 μm, preferably 1 μm to 180 μm, more preferably 1 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer.

[0031] All of these catalysts are defined as heterogeneous catalysts.

[0032] As will become more apparent from the experimental part, the inventors attempted to directly use commercially available heterogeneous catalysts when acylating 3,4 -me -dioxydibenzene, but this attempt resulted in very poor results, especially at low temperatures. The inventors have found that surprisingly, when the catalyst has an average particle size of 1 μm to 300 μm, preferably 1 μm to 180 μm, more preferably 1 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer, the acylation of MDB is possible.

[0033] The catalyst can be used as a bulk or a sulfonated crosslinked polystyrene - divinylbenzene resin supported on silica. Preferably, the sulfonated crosslinked polystyrene - divinylbenzene resin is characterized by an acid loading represented as mmol of group -SO3H per gram of material in the range of 2 to 6, more preferably 2.5 to 5.5, even more preferably about 5.

[0034] The catalyst can be a perfluorinated sulfonic acid resin used as a bulk or supported on silica. Preferably, the perfluorinated sulfonic acid resin is characterized by an acid loading expressed as mmol of group -SO3H per gram of material in the range of 0.2 to 2, more preferably 0.7 to 1.6, and even more preferably the catalyst has an acid loading of about 1.2.

[0035] In a preferred embodiment, the above catalyst is a commercially available catalyst that is subjected to a micronization process to have a particle size in the range of 1 μm to 300 μm, preferably 1 μm to 180 μm, more preferably 1 μm to 100 μm, as measured by DLS (dynamic light scattering) or a particle size analyzer.

[0036] The sulfonated crosslinked polystyrene - divinylbenzene resin can be the product Amberlyst, an ion exchange resin available from Rohm and Haas Company. These resins can be products named as follows. - Amberlyst 15 (https: / / www.sigmaaldrich.com / catalog / product / aldrich / 216399) having an acid loading of - 4.7 (expressed as mmol of group -SO3H per gram of material), - Amberlyst 36 having an acid loading of - 5.4 (expressed as mmol of group -SO3H per gram of material), (Sibao Liu and others, ’Renewable Lubricants with Tailored Molecular Architecture’, Science Advances, 5.2 (2019) (https: / / doi.org / 10.1126 / sciadv.aav5487)) Amberlyst 39 having an acid loading of -5 (expressed as mmol of group -SO3H per gram of material) (Tomasz Komon and others, ’Esterification of Acrylic Acid with 2-Ethylhexan-1-Ol: Thermodynamic and Kinetic Study’, Applied Catalysis A: General, 451 (2013), 127-36 (https: / / doi.org / 10.1016 / j.apcata.2012.11.018)), or Amberlyst 70 having an acid loading of -2.55 (expressed as mmol of group -SO3H per gram of material) (Tomasz Komon and others, ’Esterification of Acrylic Acid with 2-Ethylhexan-1-Ol: Thermodynamic and Kinetic Study’, Applied Catalysis A: General, 451 (2013), 127-36 (https: / / doi.org / 10.1016 / j.apcata.2012.11.018)).

[0037] The perfluorinated sulfonic acid resin can be the product Aquivion, which is a perfluorinated resin having the following structure. [Chemical formula]

[0038] The presence of the terminal -CF2CF2SO3H group makes the perfluorinated resin strongly acidic.

[0039] The resin Aquivion can be a commercially available product named Aquivion® PW79S, which is a crude acidic perfluorinated resin powder based on a short-chain (SSC) copolymer of tetrafluoroethylene and sulfonyl fluoride vinyl ether (SFVE) CF2=CF-O-(CF2)2-SO2F, manufactured by Solvay and having an acid loading of 1.27.

[0040] The resin Aquivion can be a commercially available product named Aquivion® P98-S, which is a perfluorinated pellet in the form of sulfonyl fluoride (-SO2F) with an equivalent weight (EW) of 980 g / eq. This perfluorinated resin is based on a unique short side-chain copolymer CF2=CF-O-(CF2)2-SO2F of tetrafluoroethylene (TFE) and sulfonyl fluoride vinyl ether (SFVE), manufactured by Solvay, and has an acid loading represented as 1.02 mmol of -SO3H groups per gram of the material.

[0041] The resin Aquivion may also be a commercially available product named Aquivion® PW87-S, which is a perfluorinated resin in powder form. This perfluorinated resin is based on a unique short side-chain copolymer CF2=CF-O-(CF2)2-SO2F of tetrafluoroethylene (TFE) and sulfonyl fluoride vinyl ether (SFVE), manufactured by Solvay, and has an acid loading of 1.15 represented as mmol of -SO3H groups per gram of the material.

[0042] The use of other resins Aquivion that are available on the market or like those in this experimental part is contemplated according to the present invention.

[0043] The perfluorinated sulfonic acid resin can be the product Nafion, which is a fully fluorinated resin having the following structure.

Chemical formula

[0044] The unique ionic properties of Nafion are the result of incorporating perfluorovinyl ether groups terminated with sulfonate groups into a tetrafluoroethylene (PTFE) backbone. The resin Nafion can be a commercially available product named Nafion (trademark) NR50, a perfluorosulfonic acid Nafion resin having high thermal stability and chemical resistance in pellet form. This perfluorinated resin is manufactured by DuPont and has an acid loading expressed as 0.8 mmol of the group -SO3H per 1 g of the material.

[0045] The use of commercially available or other Nafion resins such as those in this experimental section is contemplated according to the present invention.

[0046] Thus, the heterogeneous catalyst of the present invention is characterized by the presence of sulfonic acid groups and can also be partially or completely exchanged with iron or zinc or gallium.

[0047] In fact, the catalyst materials (acid resins) reported herein can be modified by exchanging acidic protons with metal ions selected from iron (Fe), zinc (Zn), and gallium (Ga). The procedures used for exchanging hydrogen ions on sulfonated cross-linked polystyrene-divinylbenzene resins or perfluorinated sulfonic acid resins are reported in the literature, for example, Journal of Molecular Catalysis A: Chemical 411 (2016) 257 - 263).

[0048] Surprisingly, the modification of the catalyst in terms of acid site density, strength, and accessibility due to the presence of metal ions Fe, Zn, or Ga strongly affects the reactivity of MDB in terms of conversion and selectivity to the product.

[0049] In the present invention, when the sulfonated resin catalyst is exchanged, it is partially exchanged.

[0050] According to the present invention, partial exchange means a percentage of hydrogen atoms of 5 to 80% with metal ions selected from Fe, Zn and Ga. Preferably, the exchange percentage is 10 to 50%, more preferably about 30%.

[0051] An example of a resin partially exchanged with Fe can be prepared by using Aquivion PW87-S in powder form according to the above literature.

[0052] Thus, the final exchanged sulfonation catalyst is subjected to a micronization process and thus has a particle size in the range of 1 μm to 300 μm, preferably 1 μm to 180 μm, more preferably 1 μm to 100 μm, as measured by DLS (dynamic light scattering) or a particle size analyzer. The above materials can be used as catalysts in the method of the present invention supplied or supported on a suitable inorganic oxide.

[0053] Suitable inorganic oxides can be silica, zirconia, titania and alumina, preferably silica. In particular, the supported material may be a commercially available product or may be prepared as described in the literature, for example, as described in Italian Patent No. 102018000006967.

[0054] Thus, the catalyst can be supported according to general procedures known in the art. A preferred procedure for preparing the supported catalyst according to the present invention is reported in the experimental section by way of example.

[0055] The above-mentioned resins named Amberlyst, Aquivion and Nafion can be supported on a suitable inorganic oxide. For example, Aquivion D79 can be supported on zirconia or silica, and Aquivion PW98-S can be supported on alumina. Nafion supported on silica is also available on the market by Dupont or Merk.

[0056] The resin used as a catalyst in the present invention can be supported on inorganic oxides, preferably silica, alumina, titania and zirconia, in an amount of 1 to 60 weight percent (%) based on the total weight of the supported catalyst, more preferably 5 to 30 weight percent, and even more preferably 10 to 15%.

[0057] The final supported sulfonated catalyst during the synthesis process is shaped so that a particle size in the range of 1 μm to 300 μm, preferably 1 μm to 180 μm, more preferably 1 μm to 100 μm, is obtained when measured by DLS (dynamic light scattering) or a particle size analyzer.

[0058] In a preferred embodiment, the catalyst used in the present invention is - a sulfonated crosslinked divinylbenzene resin partially exchanged with iron, zinc or gallium and supported on an inorganic oxide, or - a perfluorinated sulfonic resin partially exchanged with iron, zinc or gallium and supported on an inorganic oxide.

[0059] The final supported exchange sulfonated catalyst during the synthesis process is shaped so that a particle size in the range of 1 μm to 300 μm, preferably 1 μm to 180 μm, more preferably 1 μm to 100 μm, is obtained when measured by DLS (dynamic light scattering) or a particle size analyzer.

[0060] In one embodiment of the method of the present invention, it is selected from the group consisting of perfluorinated sulfonic resins and perfluorinated sulfonic resins partially exchanged with iron, zinc or gallium, and is either pre-subjected to a micronization process or produced with an exact range of particle sizes according to the present invention (a particle size in the range of 1 μm to 300 μm, preferably 1 μm to 180 μm, more preferably 1 μm to 100 μm, as measured by DLS (dynamic light scattering) or a particle size analyzer). In the presence of a bulk or supported catalyst, 3,4 -me The step of reacting 3,4 -dioxydibenzene with propionic anhydride is carried out in a temperature range of 50 to 200 °C, more preferably 60 to 150 °C, and even more preferably about 80 °C. In this embodiment of the present invention, the reaction time is 5 to 240 minutes, more preferably 5 to 120 minutes, and even more preferably about 60 minutes.

[0061] In one embodiment of the method of the present invention, it is selected from the group of sulfonated crosslinked divinylbenzene resins, sulfonated crosslinked divinylbenzene resins partially exchanged with iron, zinc or gallium, and is either previously subjected to a micronization process or produced within the exact particle size range according to the present invention (measured by DLS (dynamic light scattering) or a particle size analyzer, with a particle size in the range of 1 μm to 300 μm, preferably 1 μm to 180 μm, more preferably 1 μm to 100 μm). In the presence of a bulk or supported catalyst, 3,4 -me The step of reacting 3,4-dioxydibenzene with propionic anhydride is carried out in a temperature range of 50 to 150 °C, more preferably 60 to 130 °C, even more preferably about 80 °C or 120 °C. In this embodiment of the present invention, the reaction time is 5 to 240 minutes, more preferably 5 to 120 minutes, even more preferably about 60 minutes.

[0062] In a preferred embodiment, the method is carried out in a batch reactor, more preferably under solvent-free conditions, by adding a pure catalytic amount of catalyst.

[0063] The amount of catalyst is generally expressed as the molar ratio of H+ or active sites per mole of the limiting reagent 3,4 -me dioxydibenzene.

[0064] In the case of a bulk or supported catalyst selected from the group of perfluorinated sulfonic resins and perfluorinated sulfonic resins partially exchanged with iron, zinc or gallium, the ratio is preferably 0.0001 to 1, more preferably 0.001 to 0.04, even more preferably about 0.007.

[0065] In the case of a bulk or supported catalyst selected from the group of sulfonated crosslinked divinylbenzene resins, the ratio of the sulfonated crosslinked divinylbenzene resin partially exchanged with iron, zinc or gallium is 0.002 to 1, more preferably 0.01 to 0.08, even more preferably about 0.03.

[0066] Advantageously, 3,4 -meThe step of reacting terephthaloyl dichloride with propionic anhydride is preferably carried out at a molar ratio between terephthaloyl dichloride and propionic anhydride in the range of 2 to 1 to 1 to 2, more preferably at a stoichiometric ratio of 1:1. -me The molar ratio between terephthaloyl dichloride and propionic anhydride is more preferably a stoichiometric ratio of 1:1, and thus it is not necessary to consistently overuse one of the two reagents.

[0067] The stoichiometric ratio is more preferred, and therefore it is not necessary to consistently overuse one of the two reagents.

[0068] In an advantageous embodiment, the catalyst of the method can be recovered, regenerated, and recycled.

[0069] In a preferred embodiment, the catalyst can be recovered by filtration from a suspension in a reaction medium and a dilute aqueous acid solution of nitric acid at a concentration preferably in the range of 2 wt% to 60 wt%, more preferably 10 to 40%, and even more preferably 20 wt%.

[0070] In another preferred embodiment, the catalyst can be recovered by filtration from a suspension in a reaction medium and a dilute aqueous acid solution of hydrochloric acid at a concentration preferably in the range of 2 wt% to 30 wt%, more preferably 20 wt%.

[0071] The recovery of the catalyst is preferably carried out at a temperature in the range of room temperature to reflux for a time in the range of several minutes to 4 hours, more preferably 1 hour.

[0072] Therefore, the recovery of the catalyst is a regeneration process. After the regeneration process, the catalyst can be recovered by filtration, washed with water until the neutral pH of the mother liquor is reached, and dried at about 120 °C for about 1 hour. The material thus obtained, i.e., the catalyst of the present invention, can be recycled for another reaction.

[0073] Furthermore, the catalyst materials reported herein are suitable for application in both batch and continuous flow apparatuses, resulting in the selective formation of 3,4 - methylenedioxyphenyl propanone.

[0074] Accordingly, the inventors have surprisingly noted that the use of a bulk or supported resin having particles / granules in a specific size range and characterized by the presence of sulfonic acid functional groups exhibits specific catalytic activity in the acylation of 3,4-methylenedioxybenzene with propionic anhydride. Furthermore, the inventors have noted that the catalyst is used both as a bulk catalyst and a supported catalyst, and when in the form of a powder having a particle size range of 1 μm to 300 μm, preferably 1 μm to 180 μm, more preferably 1 μm to 100 μm, measured by DLS (dynamic light scattering) or a particle size analyzer, even with a very small amount of the reactive starting material as 3,4 -me methylenedioxybenzene, the acylation method of 3,4 -me methylenedioxybenzene was extremely efficient.

[0075] Advantageously, the catalyst of the method of the present invention can be recovered, regenerated and recycled to restart the reaction.

[0076] In an advantageous embodiment, the method for preparing 1-(1,3-benzodioxol-5-yl)-1-propanone is a continuous method.

[0077] From the above, it is clear that the method of the present invention is extremely efficient for the production of 1-(1,3-benzodioxol-5-yl)-1-propanone, which has operating conditions that are not as stringent as those of the prior art solvent-free conditions, is not only environmentally friendly but also has the potential to act continuously. Surprisingly, the method of the present invention does not require one of the two reagents to be consistently in excess and exhibits a short reaction time and a relatively low reaction temperature. This method is further characterized by the easy recovery, regeneration and recycling of the catalyst.

[0078] Without being bound by any theory, the inventors believe that it is basically important to include the possibility of supporting this heterogeneous catalyst on a suitable support having a high pore volume and / or a high surface area.

[0079] The features and advantages of the present invention will also become more clearly apparent from the following non-limiting examples.

[0080] Experimental Section The following acronyms were used to indicate components / products / effects in the experimental section: MBD = 3,4-Methylenedioxybenzene AP = Propionic anhydride MDP1P = 3,4-Methylenedioxypropiophenone X = Conversion rate Y = Yield S = Selectivity

[0081] Example 1 Acylation of MDB using commercially available Aquivion PW87 2.126 grams of 3,4-methylenedioxybenzene (MBD) and 2.2924 grams of propionic anhydride were placed inside a 25 mL two-neck round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.0988 grams of a commercially available catalyst (Aquivion PW87-S, corresponding to a molar ratio between the active acid sites and MDB equal to 0.007) having a particle size in the range of 0.6 mm to 1.1 mm as measured by DLS (dynamic light scattering) or a particle size analyzer was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 80 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted with 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. Analysis of the products at the end of the reaction was performed by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating from 35 °C for 6 minutes and then to 280 °C at a rate of 10.00 °C / min) and a flame ionization detector (FID). The results were as follows: 40% MDB conversion, 64% propionic anhydride conversion, 26% 3,4-methylenedioxypropiophenone yield, and 64% selectivity.

[0082] Example 2 Preparation of 3,4-Methylenedioxypiophenone with Catalyst Aquivion PW87-S at 80 °C for 1 Hour According to the Present Invention 2.126 grams of 3,4-methylenedioxybenzene (MDB) and 2.2924 grams of propionic anhydride were placed inside a 25 mL two-neck round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.0988 grams of the catalyst (Aquivion PW87-S corresponding to a molar ratio between the active acid sites equal to 0.007 and MDB), which had been previously subjected to a micronization process to a particle size in the range of 40 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer, was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 80 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. Analysis of the product at the end of the reaction was performed by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating from 35 °C for 6 minutes and then to 280 °C at a rate of 10.00 °C / min) and a flame ionization detector (FID). The results were as follows: 50% MDB conversion, 77% propionic anhydride conversion, 41% 3,4-methylenedioxypiophenone yield, and 82% selectivity.

[0083] Therefore, the inventors noted that when the catalyst is of a specific granule / particle size of the present invention, it enables not only a higher conversion of the initial product but also a higher selectivity than expected by reducing the particle size of the catalyst.

[0084] Example 3 Effect of Particle Size on the Catalytic Activity of Aquivion PW87 By changing only the particle size of the catalyst, the effect of the particle size of the catalyst on the catalytic activity of the acylation of MDB was investigated as described in Example 2. The results are reported in Table X below.

Table X

[0085] The catalyst particle size plays a fundamental role in the reaction. The decrease in particle size brought about an improvement in the MDB conversion rate that mainly depends on the catalytically active surface (increasing as the particle size decreases). Surprisingly, reducing the catalyst particle size also significantly improved the reaction selectivity towards MDP1P.

[0086] Example 4 Evaluation of the temperature effect in the presence of the catalyst Aquivion PW87-S The other four reactions were carried out as described in Example 2 by changing only the reaction temperature, i.e., 60 °C, 80 °C, 100 °C, and 120 °C. The results are reported in Table 1.

Table 1

[0087] Similar to Example 2, the reaction conditions were as follows: molar ratio between the active acid sites equal to 0.007 and MDB; MDB:AP = 1:1; reaction time 1 hour.

[0088] The increase in reaction temperature brought about an increase in the conversion rate of both reagents (as expected from the acceleration of the reaction kinetics), but the increase in the MDP1P yield was not linear, and thus a slight decrease in selectivity was observed, noting that it promoted the formation of by-products (such as polyalkylation).

[0089] In any case, all temperatures were efficient in having a high yield balanced with the achieved selectivity.

[0090] Example 5 Scale-up test to 40 ml 20.21 grams of MDB and 21.74 grams of propionic anhydride were placed inside a 250 mL three-neck round-bottom flask and stirred to obtain a homogeneous solution. The reagent mixture was heated in an 80 °C oil bath, and then 0.9363 grams of a catalyst (Aquivion PW87-S, corresponding to a molar ratio between the active acid sites equal to 0.007 and MDB) that had been previously subjected to a micronization process to a particle size in the range of 40 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer was inserted inside the flask equipped with two condensers and a thermometer. The reaction was carried out for 1 hour under magnetic stirring (720 rpm). After the reaction, the mixture was rapidly cooled in an ice bath and the reaction mixture was recovered with 500 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted in 10 mL of acetone HPLC grade and 20 μL of octane was used as an internal standard for gas chromatographic quantification. Analysis of the product at the end of the reaction was performed by GC equipped with an HP-5 (Agilent) capillary column and a flame ionization detector (FID). The results were as follows: 53% MDB conversion, 82% propionic anhydride conversion, 43% 3,4-methylenedioxypropiophenone yield and 81% selectivity.

[0091] (Compared with Example 1) An increase in the x10 factor was shown to have no effect on either the conversion or the yield.

[0092] Example 6 Scaled up to 400 mL 202.16 grams of MDB and 217.22 grams of propionic anhydride were placed inside a 1 L jacketed reactor equipped with a mechanical stirrer, a reflux condenser, and a thermometer. The reagent mixture was heated to 80 °C, and then 9.3586 grams of catalyst (Aquivion PW87-S, corresponding to a molar ratio between the active acid sites equal to 0.007 and MDB) that had been previously subjected to a micronization process to a particle size in the range of 40 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer was inserted inside. The reaction was carried out for 1 hour under mechanical stirring (250 rpm). After the reaction, 2 mL of the reaction mixture was sampled and separated from the catalyst by filtration. 50 μL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. The analysis of the product at the end of the reaction was performed by GC equipped with an HP-5 (Agilent) capillary column and a flame ionization detector (FID). The results were as follows: 46% MDB conversion, 71% propionic anhydride conversion, 38% 3,4-methylenedioxypropiophenone yield, and 82% selectivity.

[0093] Example 7 Evaluation of the reaction time effect of PW87-S in the reaction described in Example 6. For the purpose of examining the influence of the reaction time in a larger-scale reactor, the reaction was repeated as described in Example 5. To do so, the reaction mixture was sampled at different times as reported in Example 5. The results are reported in Table 2 below and shown in Figure 1. [Table 2]

[0094] By sampling the reaction mixture at different times, it was possible to confirm that the selectivity towards the desired product did not change during the reaction. The conversion increased with the reaction time as the yield in the desired product. The best compromise between yield and reaction time was 1 h, but it was possible to obtain approximately the same results by stopping the reaction after 30 min. In the latter case, the conversion of MDB and the yield in the product were a few percent lower, but it was possible to double the number of catalyst cycles per day and increase the overall yield. Increasing the reaction time up to 2 h made it possible to increase the conversion and the yield without decreasing the selectivity in order to reduce the amount of reactants that had to be recycled.

[0095] Example 8 Evaluation of Preferred Conditions When Aquivion PW79 Is the Catalyst 2.1305 g of MDB and 2.2879 g of propionic anhydride were placed inside a 25 mL two-necked round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.0900 g of catalyst (Aquivion PW79 corresponding to a molar ratio between the active acid sites equal to 0.007 and MDB) that had been previously subjected to a micronization process to a particle size in the range of 40 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 120 °C and reacted for 1 h under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. The analysis of the products at the end of the reaction was carried out by GC equipped with an HP-5 (Agilent) capillary column and a flame ionization detector (FID). The results were as follows: 64% MDB conversion, 92% propionic anhydride conversion, 47% 3,4-methylenedioxypropiophenone yield, and 73% selectivity.

[0096] Example 9 Acylation of MDB with the commercially available catalyst Aquivion PW98 2.1307 grams of MDB and 2.2879 grams of propionic anhydride were placed inside a 25 mL two-neck round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.1117 grams of the commercially available catalyst (Aquivion PW98, corresponding to a molar ratio between the active acid sites equal to 0.007 and MDB) having a particle size in the range of 1.4 mm to 2.4 mm as measured by a particle size analyzer was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 100 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted with 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. Analysis of the product at the end of the reaction was performed by GC equipped with an HP-5 (Agilent) capillary column and a flame ionization detector (FID). The results were as follows: 11% MDB conversion, 18% propionic anhydride conversion, 7% 3,4-methylenedioxypropiophenone yield, and 55% selectivity.

[0097] Example 10 Acylation of MDB with the catalyst Aquivion PW98 according to the present invention 2.1307 grams of MDB and 2.2879 grams of propionic anhydride were placed inside a 25 mL two-neck round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.1117 grams of a catalyst (Aquivion PW98 corresponding to a molar ratio between the active acid sites equal to 0.007 and MDB) that had been pre-subjected to a micronization process to a particle size in the range of 40 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 100 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted with 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. Analysis of the product at the end of the reaction was performed by GC equipped with an HP-5 (Agilent) capillary column and a flame ionization detector (FID). The results were as follows: 40% MDB conversion, 64% propionic anhydride conversion, 29% 3,4-methylenedioxypropiophenone yield, and 72% selectivity.

[0098] Example 11 The method of the present invention using the catalyst Aquivion D79 supported on silica 2.1282 grams of MDB and 2.2860 grams of propionic anhydride were placed inside a 25 mL two-neck round-bottom flask and stirred to obtain a homogeneous solution. Subsequently, 0.2999 grams of catalyst (Aquivion D79 at 30% with respect to silica, corresponding to a molar ratio between the active acid sites equal to 0.007 and MDB) characterized by a particle size in the range of 40 μm to 100 μm, as measured by DLS (dynamic light scattering) or a particle size analyzer, was inserted inside the liquid mixture, and two condensers were attached to the flask. Then, the reaction mixture was placed in a preheated oil bath at 120 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. Analysis of the product at the end of the reaction was carried out by GC equipped with an HP-5 (Agilent) capillary column and a flame ionization detector (FID). The results were as follows: 65% MDB conversion, 95% propionic anhydride conversion, 47% 3,4-methylenedioxypropiophenone yield, and 72% selectivity.

[0099] Example 12 General procedure for laboratory-scale regeneration of the catalyst in the method of the present invention First, the catalyst was separated from the reaction solution by filtration through a Buchner funnel fitted with a filter aid. Considering 0.1 g of the exhausted catalyst, this was washed with acetone HPLC (25 mL) to remove all weakly adsorbed reactants and products remaining after the reaction, and finely ground in a mortar. Subsequently, the catalyst was inserted inside a flask equipped with two condensers. Then, 5 mL of a 20 wt% HNO3 (or HCl) solution was used to regenerate the catalyst under reflux for 1 hour. The resulting suspension was then cooled and separated from the solution by filtration through a Buchner funnel fitted with a filter aid. The catalyst was washed with water until neutral pH and then washed again with acetone HPLC. Before the catalyst test, the catalyst was dried in an oven at 120 °C for 1 hour.

[0100] Example 13 Recycling Test with Catalyst PW87-S, Regeneration with Nitric Acid The catalyst from Example 5 was regenerated in the same manner as in Example 12 using 50 mL of 20% w / w HNO3 solution at 100 °C for 1 hour.

[0101] 13.61 grams of MDB and 14.57 grams of propionic anhydride were placed inside a 250 mL three-necked round-bottom flask and stirred to obtain a homogeneous solution. The reagent mixture was heated in an 80 °C oil bath, and then 0.6299 grams of the regenerated catalyst (Aquivion PW87-S, corresponding to a molar ratio between the active acid sites equal to 0.007 and MDB) that had been previously subjected to a micronization process to a particle size in the range of 40 μm to 100 μm as measured by DLS (Dynamic Light Scattering) or a particle size analyzer was inserted inside the flask equipped with two condensers and a thermometer. The reaction was carried out for 1 hour under magnetic stirring (720 rpm). After the reaction, 2 mL of the reaction mixture was sampled and separated from the catalyst by filtration. 50 μL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. The analysis of the products at the end of the reaction was carried out by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating from 35 °C for 6 minutes and then to 280 °C at a rate of 10.00 °C / min) and a flame ionization detector (FID).

[0102] To test the recyclability of the material in several catalyst runs, the recovery and regeneration of the catalyst described in Example 12 were carried out 5 times. The results are reported in Table 3 below.

Table 3

[0103] By using nitric acid, which has obvious advantages regarding process efficiency, the catalyst was recovered and recycled several times.

[0104] Example 14 Recycling Test with Catalyst Aquivion PW87-S, Regeneration with Hydrochloric Acid 2.1284 grams of MDB and 2.2935 grams of propionic anhydride were placed inside a 25 mL two-neck round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.0990 grams of a catalyst (Aquivion PW87-S corresponding to a molar ratio between the active acid sites equal to 0.007 and MDB) that had been previously subjected to a micronization process to a particle size in the range of 40 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 120 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. Analysis of the product at the end of the reaction was performed by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating from 35 °C for 6 minutes and then to 280 °C at a rate of 10.00 °C / min) and a flame ionization detector (FID). Then, the catalyst was regenerated at 100 °C for 1 hour using 5 mL of a 20% w / w HCl solution as in Example 12, recovered, washed, dried as previously reported, and tested under the same conditions for the acylation reaction. The results were reported in Table 4 below. [Table 4]

[0105] By using hydrochloric acid, which has an apparent advantage regarding process efficiency, the catalyst was recovered and recycled.

[0106] Example 15 Effect of the molar ratio between reagents on the micronized catalyst Aquivion PW87-S according to the present invention By changing only the molar ratio mol MDB / mol AP between reagents in the range of 1:1, 1.4:1, 2:1 and 1:2, four other reactions were carried out as described in Example 2. The results were reported in Table 5 below. [Table 5]

[0107] Excessive increase in AP led to higher conversion values for terephthalenedioxybenzene but had a detrimental effect on selectivity. On the other hand, working with a slightly excessive amount of MDB resulted in a more selective conversion of AP to the target product. In both cases, the best compromise between MDB conversion and selectivity to the MDP1P product was the stoichiometric amount of reagent. -me

[0108] Example 16 Effect of catalyst loading by Aquivion PW87-S as a function of the molar ratio between active acid sites and limiting reagent. Three other reactions were carried out as described in Example 2 by varying only the molar ratio between active acid sites and limiting reagent, namely 0.003, 0.007, and 0.014. The catalyst was subjected to a micronization process and sized to a particle diameter in the range of 40 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer. The results are shown in Table 6 below. [Table 6]

[0109] Increasing the catalyst loading promoted the conversion of our reagents and resulted in only a slight decrease in product selectivity.

[0110] Example 17 Zn-exchanged Aquivion D79 supported on silica. Supported Aquivion D79 characterized by a particle diameter in the range of 40 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer was reacted as described in Example 9 by exchanging it 100% with Zn, specifically Zn 2+ . The results are shown in Table 7 below. [Table 7]

[0111] ​It was found that 100% percentage of exchange with Zn had an unfavorable effect on the reaction.

[0112] Therefore, the inventors have found that it is possible to acylate MDB only with the catalyst having partial exchange, as shown in Example 18 below. The partial exchange of the catalyst according to the present invention is the percentage of 5 to 80% of hydrogen atoms exchanged with metal ions selected from Fe, Zn and Ga, preferably the exchange percentage is 10 to 50%, more preferably about 30%.

[0113] Example 18 Fe-exchanged Aquivion PW87-S For other reactions, Aquivion PW87-S was exchanged with Fe:Fe 3+ at 50% and with Fe 3+ at 100%, and carried out at 80 °C or 120 °C as described in Example 2. The final catalyst was characterized by a particle size in the range of 40 μm to 100 μm measured by DLS (dynamic light scattering) or a particle size analyzer. After the first cycle of the reaction, the catalyst was recovered, washed with 2-propanone and recycled. The results are reported in Table 8 below.

Table 8

[0114] When Aquivion is partially exchanged with ions as Fe or Zn, the conversion rate of MDB decreases strongly, but the selectivity increases.

[0115] Example 19 Effect of catalyst shape Only the catalyst form: powder (Aquivion PW98) and pellets (8-14 mesh, Aquivion P98) were changed, and other reactions were carried out at 120 °C as described in Example 9, and the only forming agent was subjected to a micronization process to a particle size in the range of 40 μm to 100 μm measured by DLS (dynamic light scattering) or a particle size analyzer. The results are reported in Table 9 below.

Table 9

[0116] Surprisingly, when the catalyst having the particle size according to the present invention was used for 8-14 mesh pellets, better results were shown for the same catalyst in terms of yield, conversion rate and selectivity.

[0117] Example 20 Recycling test with Aquivion PW79, regeneration with nitric acid 2.1303 grams of MDB and 2.2947 grams of propionic anhydride were placed inside a 25 mL two-necked round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.0903 grams of a catalyst (Aquivion PW79 corresponding to a molar ratio between the active acid sites equal to 0.007 and MDB) which had been previously subjected to a micronization process to a particle size in the range of 40 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 120 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted with 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. Analysis of the product at the end of the reaction was performed by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating to 280 °C at a rate of 10.00 °C / min after 6 minutes at 35 °C) and a flame ionization detector (FID).

[0118] After the first run, the catalyst was regenerated at 100 °C for 1 hour using 5 mL of a 20% w / w HNO3 solution in the same manner as in Example 12, recovered, washed, dried, and finally tested under the same conditions as above. The results were reported in Table 10 below.

Table 10

[0119] By using nitric acid which has obvious advantages in terms of process efficiency, the catalyst was recovered and recycled several times.

[0120] Example 21 Recycling test with Aquivion PW79, regeneration with hydrochloric acid 2.1288 grams of MDB and 2.2972 grams of propionic anhydride were placed inside a 25 mL two-necked round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.0902 grams of the catalyst (Aquivion PW79 corresponding to the molar ratio between the active acid sites equal to 0.007 and MDB), which had been previously subjected to a micronization process to a particle size in the range of 40 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer, was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 120 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. The analysis of the product at the end of the reaction was performed by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating to 280 °C at a rate of 10.00 °C / min after 6 minutes at 35 °C) and a flame ionization detector (FID).

[0121] After the first run, the catalyst was regenerated at 100 °C for 1 hour using 5 mL of a 20% w / w HCl solution in the same manner as in Example 12, recovered, washed, dried, and finally tested under the same conditions as above. The results are reported in Table 11 below.

Table 11

[0122] By using nitric acid which has obvious advantages in terms of process efficiency, the catalyst was recovered and recycled.

[0123] Example 22 Acylation of MDB using a commercially available Amberlyst 39 catalyst having a particle size of 200 - 300 μm 2.1284 grams of MDB and 2.2822 grams of propionic anhydride were placed inside a 25 mL two-necked round-bottom flask and stirred to obtain a homogeneous solution. Then, a commercially available 0.1003 grams of catalyst (Amberlyst 39 corresponding to a molar ratio between the active acid sites equal to 0.029 and MDB) having a particle size in the range of 200 μm - 300 μm, measured by DLS (dynamic light scattering) or a particle size analyzer, was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 120 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. Analysis of the product at the end of the reaction was carried out by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating to 280 °C at a rate of 10.00 °C / min after 6 minutes at 35 °C) and a flame ionization detector (FID). The results were as follows: 42% MDB conversion, 65% propionic anhydride conversion, 3,4-methylenedioxypropiophenone yield 29% and selectivity 69%.

[0124] Example 23 Acylation and recycling test of MDB with a micronized Amberlyst 30 catalyst, regeneration with nitric acid 2.1284 grams of MDB and 2.2822 grams of propionic anhydride were placed inside a 25 mL two-neck round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.1003 grams of a catalyst (Amberlyst 39 corresponding to a molar ratio between the active acid sites equal to 0.029 and MDB) that had been previously subjected to a micronization process to a particle size in the range of 40 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 120 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. Analysis of the product at the end of the reaction was carried out by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating from 35 °C for 6 minutes and then to 280 °C at a rate of 10.00 °C / min) and a flame ionization detector (FID). After the first run, the catalyst was regenerated at 100 °C for 1 hour using 5 mL of a 20% w / w HNO3 solution as in Example 12, recovered, washed, dried, and finally tested under the same conditions as above. The results are reported in Table 12 below and are represented in Figure 2.

Table 12

[0125] By using hydrochloric acid, which has obvious advantages regarding process efficiency, the catalyst was recovered and recycled several times.

[0126] By using the catalyst in a preferred range of particle sizes, higher conversion and better selectivity could be obtained.

[0127] Example 24 Acylation of MDB using a commercially available Nafion NR50 catalyst having a particle size of 400 - 600 μm 2.1274 grams of MDB and 2.2815 grams of propionic anhydride were placed inside a 25 mL two-necked round-bottom flask and stirred to obtain a homogeneous solution. Then, a commercially available 0.1419 grams of catalyst (Nafion NR50 corresponding to a molar ratio between the active acid sites equal to 0.007 and MDB) having a particle size in the range of 400 μm to 600 μm, measured with a particle size analyzer, was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 120 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted with 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. The analysis of the product at the end of the reaction was performed by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating to 280 °C at a rate of 10.00 °C / min after 6 minutes at 35 °C) and a flame ionization detector (FID). The results were as follows: 20% MDB conversion, 29% propionic anhydride conversion, 3,4-methylenedioxypropiophenone yield 11% and selectivity 56%.

[0128] Example 25 Acylation of MDB with Nafion NR50 catalyst having a particle size according to the present invention As a general procedure, 2.1274 grams of MDB and 2.2815 grams of propionic anhydride were placed inside a 25 mL two-neck round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.1419 grams of a catalyst (Nafion NR50 corresponding to a molar ratio between the active acid sites equal to 0.007 and MDB), which had been previously subjected to a micronization process to a particle size in the range of 150 μm to 300 μm as measured by a particle size analyzer, was inserted into the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 120 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. The analysis of the product at the end of the reaction was carried out by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating from 35 °C for 6 minutes and then to 280 °C at a rate of 10.00 °C / min) and a flame ionization detector (FID). After the first run, the catalyst was regenerated at 100 °C for 1 hour using 5 mL of a 20% w / w HNO3 solution as in Example 12, recovered, washed, dried, and finally tested under the same conditions as above. The results are reported in Table 13 below.

Table 13

[0129] The inventors noted that the catalyst according to the present invention enables better conversion, yield, and selectivity compared to the same catalyst not micronized within the scope of the present invention.

[0130] Example 26 Catalyst testing under continuous flow conditions The catalytic test was carried out in a fixed-bed laboratory-scale reactor operating under atmospheric pressure and continuous flow. First, 0.1799 grams (0.4 ml) of the catalyst (Aquivion PW79), which had been pre-subjected to a micronization process to a particle size in the range of 40 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer and mixed with carborundum (total volume 0.6 mL), was inserted into the interior of a reactor consisting of a 1 / 4-inch stainless steel tube (equipped with quartz wool at the beginning and end of the reactor). The reactor was wrapped with a heating band and finally covered with an insulating ceramic cloth bandage. When the system reached a temperature of 150 °C, the reagent mixture (composed of 26.007 grams of MDB and 28.631 grams of propionic anhydride) (1 / 1 mol / mol) was supplied at 0.05 mL / min through a high-precision HPLC pump. The reaction time was started from when the first droplet of the mixture emerged from the outlet line of the system. Samples were taken every 10 minutes. From each sampling, 50 μL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. The analysis of the products at the end of the reaction was carried out by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating to 280 °C at a rate of 10.00 °C / min after 6 minutes at 35 °C) and a flame ionization detector (FID). The results corresponding to the relevant time points are reported in Table 14 below.

Table 14

[0131] This catalytic test carried out in a flow was aimed mainly at covering also this technical solution for the application of solid acid resins. The test demonstrated that the method of the present invention can be advantageously carried out continuously.

[0132] Example 27 Regeneration of the PW87 Catalyst with H2O2 2.1417 grams of MDB and 2.2994 grams of propionic anhydride were placed inside a 25 mL two-neck round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.1004 grams of a catalyst (AQUIVION PW87-S corresponding to a molar ratio between the active acid sites equal to 0.007 and MDB) that had been pre-subjected to a micronization process to a particle size in the range of 40 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 80 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. Analysis of the product at the end of the reaction was performed by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating to 280 °C at a rate of 10 °C / min after 6 minutes at 35 °C) and a flame ionization detector (FID). Then, instead of the mineral acid, 5 mL of a 30% w / w H2O2 solution was used to regenerate the catalyst at 100 °C for 20 minutes as described in Example 9, and it was recovered, washed, dried, and tested under the same conditions for the acylation reaction. The results are reported in Table 15 below.

[0133]

Table 15

[0134] Example 28 General procedure for the preparation of supported catalysts using Aquivion (D72 or D79, or D82, or D98) A mixture of Si(MeO)4, distilled water, and 0.04 M HCl having a weight ratio of 68:11:1 was stirred for 45 minutes to obtain a transparent solution. The Aquivion dispersion (D72 or D79, or D82, or D98) (for example, may contain 25% w / w resin in water or a mixture of water and alcohol) was diluted with water or a mixture of water and alcohol. An aqueous 0.4 M NaOH solution was added to the resin-containing solution with stirring. The silicon-containing solution prepared as described above was quickly added to the stirred resin / NaOH solution, and a solid gel was formed after mixing for several seconds. The solid was dried overnight in an oven at 95 °C. After grinding, the obtained powder was stirred with an appropriate amount of 3.5 M aqueous HCl solution to re-acidify it, and then washed with deionized water. This process was repeated 4 times. Then, the catalyst was treated with 25% w / w HNO3 at 75 °C overnight, washed with deionized water, and dried at 100 °C for 12 hours.

[0135] Example 29 Synthesis of a catalyst containing 13 wt% Aquivion supported on silica. A mixture of 12.6706 g of Si(MeO)4, 2.0497 g of distilled water, and 0.1863 g of 0.04 M HCl was stirred for 45 minutes to obtain a transparent solution. A mixture of 2.9712 g of Aquivion D72 (or D79, or D82, or D98) resin solution (containing 25% w / w resin), 8 g of distilled water, and 9.96 g of 1-propanol was prepared. 10.3 mL of an aqueous 0.4 M NaOH solution was added to the resin-containing solution with stirring. The silicon-containing solution prepared as described above was quickly added to the stirred resin / NaOH solution, and a solid gel was formed after mixing for several seconds. The solid was dried overnight in an oven at 95 °C. After grinding, the obtained powder with a particle size of 40 μm to 100 μm was stirred with 50 mL of 3.5 M aqueous HCl solution to re-acidify it, and then washed with deionized water. This process was repeated 4 times. Then, the catalyst was treated with 25% w / w HNO3 at 75 °C overnight, washed with deionized water, and dried at 100 °C for 12 hours.

[0136] Example 30 Synthesis of a catalyst containing 13 wt% Nafion supported on silica. A mixture of 7.6003 g of Si(MeO)4, 1.2306 g of distilled water, and 0.1112 g of 0.04 M HCl was stirred for 45 minutes to obtain a clear solution. A mixture of 2.2284 g of Nafion resin solution (containing 20% w / w resin), 3.34 g of distilled water, and 4.16 g of 1-propanol was prepared. 5.52 mL of 0.4 M aqueous NaOH solution was added to the resin-containing solution with stirring. The silicon-containing solution prepared as described above was quickly added to the stirred resin / NaOH solution, and a solid gel formed a few seconds after mixing. The solid was dried overnight in an oven at 95 °C. After pulverization, the resulting powder with a particle size of 40 μm to 100 μm was stirred and re-acidified with 50 mL of 3.5 M aqueous HCl solution, and then washed with deionized water. This process was repeated 4 times. Then, the catalyst was treated with 25% w / w HNO3 at 75 °C overnight, washed with deionized water, and dried at 100 °C for 12 hours.

[0137] Example 31 The process of the present invention using the catalyst Aquivion D72 supported in silica. 2.1458 grams of MDB and 2.3081 grams of propionic anhydride were placed inside a 25 mL two-necked round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.6726 grams of a catalyst (13% w / w Aquivion D72 with respect to silica, corresponding to a molar ratio between the active acid sites equal to 0.007 and MDB) produced with a particle size in the range of 40 μm to 100 μm was inserted inside the liquid mixture, and two condensers were attached to the flask. Subsequently, the reaction mixture was placed in a preheated oil bath at 80 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted with 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. The analysis of the product at the end of the reaction was performed by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating to 280 °C at a rate of 10 °C / min after 6 minutes at 35 °C) and a flame ionization detector (FID). The results were as follows: 59% MDB conversion, 90% propionic anhydride conversion, 50% 3,4-methylenedioxypropiophenone yield and 85% selectivity, 9% by-product yield.

[0138] Example 32 Acylation of the present invention using the catalyst Aquivion D79 supported on silica. 2.1354 grams of MDB and 2.2956 grams of propionic anhydride were placed inside a 25 mL two-neck round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.7448 grams of a catalyst (13% w / w Aquivion D79 with respect to silica, corresponding to a molar ratio between the active acid sites equal to 0.007 and MDB) produced with a particle size in the range of 40 μm to 100 μm was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 80 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. The analysis of the products at the end of the reaction was carried out by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating from 35 °C for 6 minutes and then to 280 °C at a rate of 10 °C / min) and a flame ionization detector (FID). The results were as follows: 50% MDB conversion, 85% propionic anhydride conversion, 43% 3,4-methylenedioxypropiophenone yield and 86% selectivity, 7% by-product yield.

[0139] Example 33 Acylation of the present invention using the catalyst Aquivion D83 supported on silica. 2.1402 grams of MDB and 2.3039 grams of propionic anhydride were placed inside a 25 mL two-neck round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.7754 grams of a catalyst (13% w / w Aquivion D83 with respect to silica, corresponding to a molar ratio between the active acid sites equal to 0.007 and MDB) produced with a particle size in the range of 40 μm to 100 μm was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 80 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. The analysis of the product at the end of the reaction was carried out by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating to 280 °C at a rate of 10 °C / min after 6 minutes at 35 °C) and a flame ionization detector (FID). The results were as follows: 51% MDB conversion, 86% propionic anhydride conversion, 42% 3,4-methylenedioxypropiophenone yield and 83% selectivity, 7% by-product yield.

[0140] Example 34 Process of the invention using the catalyst Aquivion D98 supported in silica. As a general procedure, 1.0673 grams of MDB and 1.1502 grams of propionic anhydride were placed inside a 25 mL two-necked round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.4589 grams of a catalyst (which is 13% w / w Aquivion D98 with respect to silica and corresponds to a molar ratio between the active acid sites equal to 0.007 and MDB) produced with a particle size in the range of 40 μm to 100 μm was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 80 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. The analysis of the products at the end of the reaction was carried out by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating to 280 °C at a rate of 10 °C / min after 6 minutes at 35 °C) and a flame ionization detector (FID). The results were as follows: 49% MDB conversion, 86% propionic anhydride conversion, 3,4-methylenedioxypropiophenone yield 42% and selectivity 85%, by-products

[0141] Example 35 Process of the invention using the catalyst Aquivion D72 (5% w / w) supported in silica. As a general procedure, 2.146 grams of MDB and 2.3044 grams of propionic anhydride were placed inside a 25 mL two-neck round-bottom flask and stirred to obtain a homogeneous solution. Then, 1.762 grams of the catalyst obtained as described in Example 29 with varying resin loadings and produced with a particle size in the range of 40 μm to 100 μm (which is 5% w / w of Aquivion D72 with respect to silica and corresponds to a molar ratio between the active acid sites equal to 0.007 and MDB) was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 80 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. Analysis of the product at the end of the reaction was performed by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating from 35 °C for 6 minutes and then to 280 °C at a rate of 10 °C / min) and a flame ionization detector (FID). The results were as follows: 39% MDB conversion, 96% propionic anhydride conversion, 33% 3,4-methylenedioxypropiophenone yield and 86% selectivity, 3% by-product yield.

[0142] Example 36 The process of the present invention using a catalyst Aquivion D72 (30% w / w) supported in silica. As a general procedure, 2.152 grams of MDB and 2.3269 grams of propionic anhydride were placed inside a 25 mL two-neck round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.2941 grams of the catalyst obtained as described in Example 29 with varying resin loadings and produced with a particle size in the range of 40 μm to 100 μm (which is 30% w / w Aquivion D72 with respect to silica and corresponds to a molar ratio between the active acid sites equal to 0.007 and MDB) was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 80 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. The analysis of the product at the end of the reaction was carried out by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating from 35 °C for 6 minutes and then to 280 °C at a rate of 10 °C / min) and a flame ionization detector (FID). The results were as follows: 47% MDB conversion, 78% propionic anhydride conversion, 42% 3,4-methylenedioxypropiophenone yield and 88% selectivity, 8% by-product yield.

[0143] Example 37 The method of the present invention using a catalyst Nafion (13% w / w) supported in silica. As a general procedure, 1.4281 grams of MDB and 1.5415 grams of propionic anhydride were placed inside a 25 mL two-neck round-bottom flask and stirred to obtain a homogeneous solution. Then, 0.630 grams of the catalyst obtained as described in Example 29, produced with a particle size in the range of 40 μm to 100 μm (which is 13% w / w Nafion with respect to silica and corresponds to a molar ratio between the active acid sites equal to 0.007 and MDB), was inserted inside the liquid mixture, and two condensers were attached to the flask. Next, the reaction mixture was placed in a preheated oil bath at 80 °C and reacted for 1 hour under magnetic stirring (500 rpm). After the reaction, the mixture was rapidly cooled in an ice bath, and the reaction mixture was recovered with 50 mL of acetone HPLC grade. 0.8 mL of the mixture was diluted in 10 mL of acetone HPLC grade, and 20 μL of octane was used as an internal standard for gas chromatographic quantification. The analysis of the products at the end of the reaction was carried out by GC equipped with an HP-5 (Agilent) capillary column (the temperature gradient used consisted of heating to 280 °C at a rate of 10 °C / min after 6 minutes at 35 °C) and a flame ionization detector (FID). The results were as follows: 49% MDB conversion, 85% propionic anhydride conversion, 41% 3,4-methylenedioxypropiophenone yield and 85% selectivity, 6% by-product yield.

Claims

1. A method for preparing 1-(1,3-benzodioxol-5-yl)-1-propanone, comprising reacting 3,4-methylenedioxybenzene with propionic anhydride in the presence of a bulk or supported catalyst, wherein the catalyst is selected from the group consisting of sulfonated crosslinked polystyrene-divinylbenzene resin, iron, zinc, or gallium-partially exchanged sulfonated crosslinked polystyrene-divinylbenzene resin, perfluorinated sulfonic resin, and iron, zinc, or gallium-partially exchanged perfluorinated sulfonic resin, and the catalyst has an average particle size of 1 μm to 300 μm, preferably 1 μm to 180 μm, more preferably 1 μm to 100 μm as measured by DLS (dynamic light scattering) or a particle size analyzer. A method for preparing 1-(1,3-benzodioxol-5-yl)-1-propanone.

2. The bulk or supported catalyst is a sulfonated crosslinked polystyrene-divinylbenzene resin used as a bulk or supported on silica, and the sulfonated crosslinked polystyrene-divinylbenzene resin has an acid loading represented by mmol of group -SO ３ H per gram of the material in the range of 2 to 6, preferably 2.5 to 5.5, more preferably about 5. The method according to claim 1.

3. The bulk or supported catalyst is a perfluorinated sulfonic acid resin used as a bulk or supported on silica, and the perfluorinated sulfonic acid resin has an acid loading represented by mmol of group -SO ３ H per gram of the material in the range of 0.2 to 2, preferably 0.7 to 1.6, more preferably an acid loading of about 1.

2. The method according to claim 1.

4. The method according to claim 2, wherein the sulfonated crosslinked polystyrene-divinylbenzene resin is product Amberlyst.

5. The method according to claim 3, wherein the perfluorinated sulfonic acid resin is product Aquivion or product Nafion.

6. The bulk or supported catalyst is a sulfonated crosslinked polystyrene-divinylbenzene resin or a perfluorinated sulfonic acid resin partially exchanged with iron or zinc or gallium, and the partial exchange is a percentage of 5 to 80% of hydrogen atoms exchanged with metal ions selected from Fe, Zn, and Ga, preferably the exchange percentage is 10 to 50%, more preferably about 30%, according to the method of claim 1.

7. The catalyst is supported on a suitable inorganic oxide, preferably zirconia, alumina, titania, and silica, more preferably silica, according to the method of any one of claims 1 to 6.

8. The catalyst is supported on the inorganic oxide in an amount of 1 to 60 weight percent (%) based on the total weight of the supported catalyst, more preferably 5 to 30 weight percent, even more preferably 10 to 15 weight percent, according to the method of claim 7.

9. The step of reacting 3,4-methylenedioxybenzene with propionic anhydride is carried out in a temperature range of 50 to 200 °C, preferably 60 to 150 °C, more preferably about 80 °C, according to the method of any one of claims 1, 3, 5 to 8.

10. The reaction time is 5 to 240 minutes, preferably 5 to 120 minutes, more preferably about 60 minutes, according to the method of claim 9.

11. The step of reacting 3,4-methylenedioxybenzene with propionic anhydride is carried out in a temperature range of 50 to 150 °C, preferably 60 to 130 °C, more preferably about 80 °C or about 120 °C, according to the method of any one of claims 1, 2, 4, 6 to 8.

12. The reaction time is 5 to 240 minutes, preferably 5 to 120 minutes, more preferably about 60 minutes, according to the method of claim 11.

13. The method according to any one of claims 1, 3, 5 to 10, wherein the amount of the catalyst expressed as the ratio between the number of moles of H+ or active sites per mole of the limiting reagent is 0.0001 to 1, preferably 0.001 to 0.04, more preferably about 0.

007.

14. The method according to any one of claims 1, 2, 4, 6 to 8, 11 to 12, wherein the amount of the catalyst expressed as the ratio between the number of moles of H+ or active sites per mole of the limiting reagent is 0.002 to 1, more preferably 0.01 to 0.08, even more preferably about 0.

03.

15. The method according to any one of claims 1 to 14, wherein the step of reacting 3,4 - methylenedioxybenzene with propionic anhydride is carried out at a molar ratio between 3,4 - methylenedioxybenzene and propionic anhydride in the range of 2 to 1 to 1 to 2, preferably at a stoichiometric ratio of 1:

1.

16. The method according to any one of claims 1 to 15, wherein the catalyst is recovered, regenerated and recycled.

17. The method according to claim 16, wherein the catalyst is recovered by filtration from a suspension in the reaction medium and a dilute aqueous acid solution of nitric acid at a concentration preferably in the range of 2 wt% to 60 wt%, more preferably 10 to 40%, even more preferably 20 wt%.

18. The method according to claim 16, wherein the catalyst is recovered by filtration from a suspension in the reaction medium and a dilute aqueous acid solution of hydrochloric acid at a concentration preferably in the range of 2 wt% to 30 wt%, more preferably 20 wt%.

19. The method according to any one of claims 16 to 18, wherein the recovery of the catalyst is carried out at a temperature in the range of room temperature to reflux for a time in the range of several minutes to 4 hours, preferably 1 hour.

20. The recovery, regeneration and recycling of the catalyst are carried out using H ２ O ２ The method according to claim 16, wherein the recovery, regeneration and recycling of the catalyst are carried out using H

21. The method according to any one of claims 1 to 20, wherein the catalyst has an average particle size of 40 μm to 100 μm.

22. The method according to any one of claims 1 to 21, wherein the method is a continuous method.

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