Photocatalytic synthesis of α,β-unsaturated carbonyl compounds and their intermediates

Abstract

This specification describes a process for producing α,β-unsaturated acids and amides and their intermediates via a photocatalytic reaction in the presence of a photocatalyst, oxygen, and optionally a solvent. The photocatalyst contains tungstic acid or a salt of tungstic acid. This process is simple, clean, energy efficient, and provides good conversion of the final product, good selectivity, good turnover, and easy purification.

Description

Technical Field

[0001] The present invention relates to the photocatalytic synthesis of α,β-unsaturated carbonyl compounds and their intermediates.

Background Art

[0002] Unsaturated carbonyl compounds, especially α,β-unsaturated acids and amides (such as methacrylic acid (MAA), methyl methacrylate (MMA), acrylamide (AA), methacrylamide (MA), etc.) are important compounds in the chemical industry. They are useful not only by themselves but also in combination with other monomers in the production of polymers for various applications such as adhesives, binders, coatings, paints, abrasives, detergents, flocculants, dispersants, metal ion sequestering agents, etc.

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, fossil-derived α,β-unsaturated acids and amides contribute to greenhouse gas emissions, and as fossil resources become increasingly scarce, more expensive, and subject to regulation, there is a growing need for non-fossil-derived α,β-unsaturated acids and amides made from renewable raw materials that can be replenished naturally or, for example, via agricultural technology. Biogenic volatile fatty acids (such as propionic acid, butyric acid, isobutyric acid, isovaleric acid, valeric acid, isocaproic acid, caproic acid, heptanoic acid, octanoic acid, etc.) provide one possible source of such renewable raw materials.

[0004] In addition, regardless of the source of the raw materials, there is a need in the art for a simple, clean, energy-efficient process for producing α,β-unsaturated acids and amides that provides good conversion of the final product, good selectivity, and easy purification.

Means for Solving the Problems

[0005] This specification describes a simple, clean, and highly energy-efficient photocatalytic process for producing α,β-unsaturated acids and amides and their intermediates that provides good conversion of the final product, good selectivity, good turnover, and easy purification.

[0006] In a preferred embodiment, a compound of formula (1):

Chemical formula

[0007] In another embodiment, a compound of formula (3) and / or a compound of formula (3’) is prepared from a compound of formula (1) by oxidizing the compound of formula (1) via a photocatalytic reaction in the presence of oxygen and a photocatalyst:

Chemical formula

[0008] In another preferred embodiment, the intermediate compound of formula (3) and / or formula (3’) is prepared from the compound of formula (1) by oxidizing the compound of formula (1) via a photocatalytic reaction in the presence of oxygen and a photocatalyst.

Chemical formula

Chemical formula

Brief Description of the Drawings

[0009]

Fig. 1A

Fig. 1B

Fig. 2A

Fig. 2B

Fig. 3A

Fig. 3B

Fig. 4

[0010] As used herein, when terms such as "invention", "the invention", "the present invention" appear in both the headings and the text, they refer only to the specific embodiments immediately following. They are not intended to be generally limiting, nor are they generally limited to some individual advancements in the technical field described herein.

[0011] When a quantity, concentration, or other value or parameter is given herein as a range and / or as a list of values, this is specifically disclosed as including all ranges formed from any pair of any upper and lower limits, and all such ranges, integers, and fractions are to be understood as including all integers and fractions within that range, whether or not such integers and fractions are separately disclosed. When a numerical range is recited herein, unless otherwise specified, the range is intended to include its endpoints, as well as all integers and fractions within that range. For example, the range of 1 to 10 includes and discloses 3. The scope of the present invention is not limited to the specific values recited when defining a range.

[0012] In one embodiment, the present invention is a compound of formula (1): **CHEMICAL STRUCTURE** is irradiated with long-wavelength ultraviolet rays and / or short-wavelength visible light (e.g., 200 - 500 nm) in the presence of a photocatalyst such as oxygen and tungstic acid or its salts, wherein R 1 , R 2 , and R 3 each independently represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, X represents a monovalent group represented by -OR a or NR b R c , and R a , R b , and R c each independently represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. Preferably, the compound of formula (1) is irradiated for a sufficient time and under conditions to undergo a chemical change (i.e., conversion to one or more different compounds).

[0013] In one embodiment, the present invention provides a method for producing a compound of formula (3), a compound of formula (3'), or both, comprising oxidizing the compound of formula (1) via a photocatalytic reaction in the presence of a photocatalyst such as oxygen and tungstic acid or its salts:

Chemical formula

[0014] In another embodiment, the present invention is a method for producing a compound of formula (2), comprising

Chemical formula

Chemical formula

[0015] In all the formulas and reactions described herein, non-limiting preferred organic groups (organic radicals) having 1 to 20 carbon atoms for R 1 , R 2 , R 3 , R a , R b , and R c include saturated straight-chain or branched-chain hydrocarbon radicals (alkyl radicals). In one embodiment, the alkyl radical has 1 to 18 carbon atoms (C1-C 18 ). In other embodiments, the alkyl radical is C1-C6, C1-C5, C1-C3, C1-C 12 , C1-C 10, C1-C8, C1-C4 or C1-C3. Examples of alkyl groups include methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (n-Pr, n-propyl, -CH2CH2CH3), 2-propyl (i-Pr, i-propyl, -CH(CH3)2), 1-butyl (n-Bu, n-butyl, -CH2CH2CH2CH3), 2-methyl-1-propyl (i-Bu, i-butyl, -CH2CH(CH3)2), 2-butyl (s-Bu, s-butyl, -CH(CH3)CH2CH3), 2-methyl-2-propyl (t-Bu, t-butyl, -C(CH3)3), 1-pentyl (n-pentyl, -CH2CH2CH2CH2CH3), 2-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH(CH2CH3)2), 2-methyl-2-butyl (-C(CH3)2CH2CH3), 3-methyl-2-butyl (-CH(CH3)CH(CH3)2), 3-methyl-1-butyl (-CH2CH2CH(CH3)2), 2-methyl-1-butyl (-CH2CH(CH3)CH2CH3), 1-hexyl (-CH2CH2CH2CH2CH2CH3), 2-hexyl (-CH(CH3)CH2CH2CH2CH3), 3-hexyl (-CH(CH2CH3)(CH2CH2CH3)), 2-methyl-2-pentyl (-C(CH3)2CH2CH2CH3), 3-methyl-2-pentyl (-CH(CH3)CH(CH3)CH2CH3), 4-methyl-2-pentyl (-CH(CH3)CH2CH(CH3)2), 3-methyl-3-pentyl (-C(CH3)(CH2CH3)2), 2-methyl-3-pentyl (-CH(CH2CH3)CH(CH3)2), 2,3-dimethyl-2-butyl (-C(CH3)2CH(CH3)2), 3,3-dimethyl-2-butyl (-CH(CH3)C(CH3)3, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl. Preferred alkyl groups include methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-methyl-1-propyl, 2-butyl, and 2-methyl-2-propyl; Linear or branched hydrocarbon radicals (alkenyl radicals) having at least one carbon-carbon double bond, including those having "cis" and "trans" orientations, or alternatively "E" and "Z" orientations (all of which are included herein), are mentioned. In one example, the alkenyl radical has 2 to 18 carbon atoms (C2-C 18 ). In other examples, the alkenyl radical is C2-C 12 , C2-C 10 , C2-C8, C2-C6, or C2-C3. Examples include ethenyl or vinyl (-CH=CH2), prop-1-enyl (-CH=CHCH3), prop-2-enyl (-CH2CH=CH2), 2-methylprop-1-enyl, but-1-enyl, but-2-enyl, but-3-enyl, buta-1,3-dienyl, 2-methylbuta-1,3-diene, hexa-1-enyl, hexa-2-enyl, hexa-3-enyl, hexa-4-enyl, and hexa-1,3-dienyl; Linear or branched hydrocarbon radicals (alkynyl radicals) having at least one carbon-carbon triple bond are mentioned, but not limited thereto. In one example, the alkynyl radical has 2 to 18 carbon atoms (C2-C 18 ). In other examples, the alkynyl radical is C2-C 12 , C2-C 10 , C2-C8, C2-C6, or C2-C3. Examples include ethynyl (-C≡CH), prop-1-ynyl (-C≡CCH3), prop-2-ynyl (propargyl, -CH2C≡CH), but-1-ynyl, but-2-ynyl, and but-3-ynyl; Linear or branched radicals (alkoxy groups) represented by the formula -OR, where R is alkyl, alkenyl, alkynyl, or carboxysilyl, are mentioned, but not limited thereto. Examples of alkoxy groups include methoxy, ethoxy, propoxy, isopropoxy, and cyclopropoxy; Alkyl radicals (haloalkyl groups) substituted with one or more (e.g., 1, 2, 3, or 4) halo groups; An alkyl radical (ether group) interrupted by one or more (e.g., 1, 2, 3, or 4) oxygen atoms; An alkyl radical (ester group) interrupted by one or more (e.g., 1, 2, 3, or 4) -COO- or -OCO- groups; A monocyclic, bicyclic, or tricyclic carbocyclic group containing a condensed ring may be mentioned. In one embodiment, the aryl radical is a group having 6 to 20 carbon atoms (C6-C 20 aryl). In another embodiment, the aryl contains a group having 6 to 10 carbon atoms (C6-C 10 aryl). Examples of aryl groups include phenyl, naphthyl, anthracyl, biphenyl, phenanthrenyl, naphthacenyl, 1,2,3,4-tetrahydronaphthalenyl, 1H-indenyl, 2,3-dihydro-1H-indenyl, etc., which may be substituted by one or more substituents described herein and may be independently substituted; A monocyclic, bicyclic, or tricyclic ring system group having 5 to 14 ring atoms, in which at least one ring is aromatic and contains at least one heteroatom (heteroaryl radical) may be mentioned. In one embodiment, the heteroaryl contains a 4- to 6-membered monocyclic aromatic group, and one or more ring atoms are independently nitrogen, sulfur, or oxygen which may optionally be substituted. In another embodiment, the heteroaryl contains a 5- to 6-membered monocyclic aromatic group, and one or more ring atoms are independently nitrogen, sulfur, or oxygen which may optionally be substituted. In some embodiments, the heteroaryl group is C1-C 20A heteroaryl group, wherein the heteroaryl ring contains 1 to 20 carbon atoms and the remaining ring atoms include one or more nitrogen, sulfur, or oxygen atoms. Examples of heteroaryl groups include thienyl, furyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, oxazolyl, isoxazolyl, triazolyl, thiadiazolyl, oxadiazolyl, tetrazolyl, thiatriazolyl, oxatriazolyl, pyridyl, pyrimidyl, pyrazinyl, pyridazinyl, triazinyl, tetrazinyl, tetrazolo[1,5-b]pyridazinyl, imidazo[1,2-a]pyrimidinyl, purinyl, benzoxazolyl, benzofuryl, benzothiazolyl, benzothiadiazolyl, benzotriazolyl, benzimidazolyl, indolyl, 1,3-thiazol-2-yl, 1,3,4-triazol-5-yl, 1,3-oxazol-2-yl, 1,3,4-oxadiazol-5-yl, 1,2,4-oxadiazol-5-yl, 1,3,4-thiadiazol-5-yl, 1H-tetrazol-5-yl, 1,2,3-triazol-5-yl, pyridine-2-yl N-oxide, and pyrazolo[4,3-c]pyridinyl. The term "heteroaryl" also includes groups in which the heteroaryl is fused to one or more aryl rings, carbocyclic rings, or heterocyclic rings and the radical or point of attachment is on the heteroaryl ring. Non-limiting examples include indolyl, isoindolyl, benzothienyl, benzofuranyl, dibenzofuranyl, indazolyl, benzimidazolyl, benzothiazolyl, quinolyl, isoquinolyl, cinnolinyl, phthalazinyl, quinazolinyl, quinoxalinyl, 4H-quinolizinyl, carbazolyl, acridinyl, phenazinyl, phenothiazinyl, phenoxazinyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, and pyrido[2,3-b]-1,4-oxazin-3(4H)-one. The heteroaryl group may be monocyclic, bicyclic, or tricyclic; It can be a saturated, partially unsaturated, or aromatic ring system group (carbocyclic radical) having 3 to 20 carbon atoms. In one embodiment, the carbocyclic contains 3 to 12 carbon atoms (C3-C 12)。In another embodiment, the carbocyclic ring is C3-C8, C3-C 10 , or C5-C 10 . In other embodiments, the carbocyclic ring, as a monocyclic ring, includes C3-C8, C3-C6, or C5-C6. In another embodiment, the carbocyclic ring as a bicyclic ring includes C7-C 12 . In another embodiment, the carbocyclic ring as a spiro ring system includes C5-C 12 . Examples of monocyclic carbocyclic rings include cyclopropyl, cyclobutyl, cyclopentyl, 1-cyclopenta-1-enyl, 1-cyclopenta-2-enyl, 1-cyclopenta-3-enyl, cyclohexyl, perdeuterocyclohexyl, 1-cyclohex-1-enyl, 1-cyclohex-2-enyl, 1-cyclohex-3-enyl, cyclohexadienyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl, phenyl, and cyclododecyl. Bicyclic carbocyclic rings having 7 to 12 ring atoms include [4,3], [4,4], [4,5], [5,5], [5,6], or [6,6] ring systems, such as bicyclo[2.2.1]heptane, bicyclo[2.2.2]octane, naphthalene, and bicyclo[3.2.2]nonane. Spirocarbocyclic rings include spiro[2.2]pentane, spiro[2.3]hexane, spiro[2.4]heptane, spiro[2.5]octane, and spiro[4.5]decane. The term carbocyclic ring includes aryl ring systems as defined herein. The term carbosicyl also includes cycloalkyl rings (e.g., saturated or partially unsaturated mono-, di-, or spiro-carbon rings). A carbocyclic group (heterocyclyl or heterocyclic radical) in which one or more (e.g., 1, 2, 3, or 4) carbon atoms are replaced by a heteroatom (e.g., O, N, or S). In some embodiments, the heterocyclyl or heterocycle refers to a saturated ring system such as a 3- to 12-membered saturated heterocyclyl ring system. In some embodiments, the heterocyclyl or heterocycle refers to a heteroaryl ring system such as a 5- to 14-membered heteroaryl ring system. The heterocyclyl or heterocycle may optionally be substituted with one or more substituents independently selected from those defined herein. In one example, the heterocyclyl or heterocycle contains 3 to 12 ring atoms, includes monocyclic, bicyclic, tricyclic, and spiro ring systems, the ring atoms are carbon, and 1 to 5 ring atoms are heteroatoms selected from nitrogen, sulfur, or oxygen, which are optionally substituted with one or more groups independently. In one example, the heterocyclyl or heterocycle contains 1 to 4 heteroatoms. In another example, the heterocyclyl or heterocycle contains a 3- to 7-membered monocyclic ring having one or more heteroatoms selected from nitrogen, sulfur, or oxygen. In another example, the heterocyclyl or heterocycle contains a 4- to 6-membered monocyclic ring having one or more heteroatoms selected from nitrogen, sulfur, or oxygen. In another example, the heterocyclyl or heterocycle contains a 3-membered monocyclic ring. In another example, the heterocyclyl or heterocycle contains a 4-membered monocyclic ring. In another example, the heterocyclyl or heterocycle contains a 5- to 6-membered monocyclic ring. In one example, the heterocyclyl group or heterocyclic group contains 0 to 3 double bonds. Any nitrogen or sulfur heteroatom may optionally be oxidized (e.g., NO, SO, SO2), and any nitrogen heteroatom may optionally be quaternized (e.g., [NR4] + Cl - , [NR4] + OH -) Examples of heterocyclyl or heterocyclic rings include oxiranyl, aziridinyl, thiiranyl, azetidinyl, oxetanyl, thietanyl, 1,2-dithietanyl, 1,3-dithietanyl, pyrrolidinyl, dihydro-1H-pyrrolyl, dihydrofuranyl, tetrahydrofuranyl, dihydrothienyl, tetrahydrothienyl, imidazolidinyl, piperidinyl, piperazinyl, morpholinyl, thiomorpholinyl, 1,1-dioxo-thiomorpholinyl, dihydropyranyl, tetrahydropyranyl, hexahydrothiopyranyl, hexahydropyrimidinyl, oxazinanyl, thiazinanyl, thioxanyl, homopiperazinyl, homopiperidinyl, azepanyl, oxepanyl, thiepanyl, oxazepinyl, oxazepanyl, diazepanyl, 1,4-diazepanyl, diazepinyl, thiazepinyl, thiazepanyl, tetrahydrothiopyranyl, oxazolidinyl, thiazolidinyl, isothiazolidinyl, 1,1-dioxoisothiazolidinonyl, oxazolidinonyl, imidazolidinonyl, 4,5,6,7-tetrahydro[2H]indazolyl, tetrahydrobenzimidazolyl, 4,5,6,7-tetrahydrobenzo[d]imidazolyl, 1,6-dihydroimidazo[4,5-d]pyrrolo[2,3-b]pyridinyl, thiazinyl, oxazinyl, thiadiazinyl, oxadiazinyl, dithiazinyl, dioxazinyl, oxathiazinyl, thiatriazinyl, oxatriazinyl, dithiadiazinyl, imidazolinyl, dihydropyrimidyl, tetrahydropyrimidyl, 1-pyrrolinyl, 2-pyrrolinyl, 3-pyrrolinyl, indolinyl, thiapyranyl, 2H-pyranyl, 4H-pyranyl, dioxanyl, 1,3-dioxolanyl, pyrazolinyl, pyrazolidinyl, dithianyl, dithiolanyl, pyrimidinonyl, pyrimidinedionyl, pyrimidine-2,4-dionyl, piperazinonyl, piperazinedionyl, pyrazolidinylimidazolinyl, 3-azabicyclo[3.1.0]hexanyl, 3,6-azabicyclo[3.1.1]heptanyl, 6-azabicyclo[3.1.1]heptanyl, 3-azabicyclo[3.1.1]heptanyl, 3-azabicyclo[4.1.0]heptanyl, azabicyclo[2.2.2]hexanyl, 2-azabicyclo[3.2.1]octanyl, 8-azabicyclo[3.2.1]octanyl, 2-azabicyclo[2.2.2]octanyl, 8-azabicyclo[2.2.2]octanyl, 7-oxabicyclo[2.2.1]heptane, azaspiro[3.5]nonanyl, azaspiro[2.5]octanyl, azaspiro[4.5]decanyl, 1-azaspiro[4.5]decan-2-one, azaspiro[5.5]undecanyl, tetrahydroindolyl, octahydroindolyl, tetrahydroisoindolyl, tetrahydroindazolyl. Examples of 5-membered heterocyclyl or heterocyclic rings containing a sulfur or oxygen atom and 1 to 3 nitrogen atoms include thiazolyl such as thiazol-2-yl and thiazol-2-yl N-oxide, thiadiazolyl such as 1,3,4-thiadiazol-5-yl and 1,2,4-thiadiazol-5-yl, oxazolyl such as oxazol-2-yl, and oxadiazolyl such as 1,3,4-oxadiazol-5-yl and 1,2,4-oxadiazol-5-yl. Examples of 5-membered ring heterocyclyl or heterocyclic rings containing 2 to 4 nitrogen atoms include imidazolyl such as imidazol-2-yl; triazolyl such as 1,3,4-triazol-5-yl; 1,2,3-triazol-5-yl, 1,2,4-triazol-5-yl, and tetrazolyl such as 1H-tetrazol-5-yl. Examples of benzo-fused 5-membered heterocyclyl or heterocyclic rings are benzoxazol-2-yl, benzthiazol-2-yl, and benzimidazol-2-yl. Examples of 6-membered heterocyclyl or heterocyclic rings include 1 to 3 nitrogen atoms and optionally a sulfur or oxygen atom, such as pyridyl such as pyrid-2-yl, pyrid-3-yl, and pyrid-4-yl; pyrimidyl such as pyrimid-2-yl and pyrimid-4-yl; triazinyl such as 1,3,4-triazin-2-yl and 1,3,It contains 5-triazin-4-yl; pyridazinyl, especially pyridazin-3-yl and pyrazinyl. Pyridine N-oxide and pyridazine N-oxide and pyridyl, pyrimido-2-yl, pyrimido-4-yl, pyridazinyl, and 1,3,4-triazin-2-yl groups are other exemplary heterocyclyl groups. The term "heterocyclyl" or "heterocycle" also includes groups in which the heterocyclyl is fused to one or more aryl rings, carbocyclic rings, or heterocyclyl rings and the radical or point of attachment is on the heterocyclyl ring. Non-limiting examples include tetrahydroquinolinyl and tetrahydroisoquinolinyl. See, for example, U.S. Patent No. 11,247,989, which is incorporated herein by reference.,

[0016] In a preferred embodiment, R 1 、R 2 、R 3 、R a 、R b 、and R c are each independently a hydrogen atom or an alkyl, alkoxy, haloalkyl, ether, or ester radical. In a preferred embodiment, an organic group having 1 to 20 carbon atoms preferably has 1 to 18, 1 to 16, 1 to 8, etc. carbons including 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 carbons.,

[0017] Preferred compounds of formula (1) include propionic acid, butyric acid, pentanoic acid, hexanoic acid, isobutyric acid, 2-methylbutyric acid, 2-methylpentanoic acid, 2-methylhexanoic acid, methyl esters of these acids (e.g., methyl propionate, methyl pentanoate, methyl isobutyrate, etc.), propylamide, butylamide, 2-methylbutanamide, pentylamide, hexylamide, isobutylamide, and -NH(methyl) and -N(methyl)2 derivatives of these amides.,

[0018] The reactions described herein are photocatalytic reactions that occur in the presence of light, oxygen, and one or more photocatalysts (e.g., tungstic acid or its salts). Generally speaking, without limitation, a photocatalytic reaction involves the absorption of light by one or more reactant species in the presence of one or more photocatalysts that participate in the chemical reaction without being consumed.

[0019] The photocatalytic reactions described herein may be homogeneous when the reactants and the photocatalyst are present in the same phase, or may be heterogeneous when the photocatalyst is present in a phase different from the reactants. The reaction may be carried out in a solvent or without a solvent (i.e., under neat conditions). Preferably, light in the wavelength range of 300 - 425 nm, including long-wavelength ultraviolet light and / or short-wavelength visible light, such as 200 - 500 nm, preferably 250 - 450 nm, more preferably 320, 340, 350, 360, 365, 370, 380, 390, 400, 410, and 420 nm, is used. Any suitable light source of such wavelengths can be used such that it enables irradiation of the reactants, such as those constructed of borosilicate glass, with any suitable photoreaction vessel (batch reactor, flow reactor, etc.). For example, when particularly low oxygen or only air pressure is required, a flow reactor and a bubble column reactor (batch or semi-batch) are preferred for scaling up the conversion of isobutyric acid (IBA) to methacrylic acid (MAA). The irradiance can vary within a wide range of, for example, 0.1 mW / cm 2 ~1200 mW / cm 2 such as 10, 20, 40, 60, 80, 100, 200, 300, 400, 500, 600, 700, 800, 900, and 1000 mW / cm 2 including 0.1 mW / cm 2 ~10,000 mW / cm 2 The preferred range of irradiance is about 10 mW / cm 2 ~400 mW / cm 2 is.

[0020] The setting and initiation of the reactions described herein are within the ability of one of ordinary skill in the art, taking this specification into account, similar to monitoring the progress of the reaction, including the identity and amount of the product produced by, for example, chromatography using an internal standard, NMR, etc. The reaction time can be varied within a wide range (e.g., 15 minutes to 72 hours or more) depending on various reaction variables such as the intensity of light, the wavelength of light, the concentration of reactants, the reaction temperature (e.g., -20 °C, -10 °C, 0 °C, 10 °C, room temperature (20 °C), and -30 to 200 °C including 30, 40, 50, 60, 70, 80, and 90 °C, etc.), all of which are within the ability of one of ordinary skill in the art taking this specification into account.

[0021] When a solvent is used, its selection is not limited. Preferably, the solvent does not appreciably absorb the irradiated light and dissolves the reactants. A mixture may be used. Examples include, for example, acetonitrile, acetone, water, dichloromethane, dimethylformamide, dimethyl sulfoxide, ethyl acetate, pyridine, tetrahydrofuran, etc. Preferred solvents include acetonitrile and acetone.

[0022] When a solvent is used, its amount is not particularly limited and can vary within a wide range. Taking this disclosure into account, one of ordinary skill in the art can determine the amount to be used based on reaction conditions, etc. For example, when both the reactant, such as isobutyric acid, and the solvent are in liquid form at room temperature, the amount of solvent used can be quantified based on volume / volume (v / v), and it can also be used for reactants that are solid at room temperature by performing the measurement at a temperature higher than the melting point of the reactant and the melting point of the solvent. Example v / v ratios of reactant / solvent include 1 / 99, 5 / 95, 10 / 90, 15 / 85, 20 / 80, 30 / 70, 40 / 60, 50 / 50, 60 / 40, 30 / 70, 80 / 20, 85 / 15, 90 / 10, 95 / 5, and 99 / 1. The amount of solvent used can also be quantified on a concentration (molar) basis. For example, concentrations of reactants from 0.01 to 30 M based on the reaction volume can be used, including 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7 M, etc.

[0023] Oxygen is present in the reaction mixture as used herein. It can be provided in any form and in multiple forms, such as in the air present in the solvent (if present), in the air present in the reaction chamber, in the air added to the reaction chamber intermittently or continuously, in the air used to pressurize the reaction vessel when performing a reaction at a pressure exceeding atmospheric pressure, etc. Of course, pure oxygen, or a mixture of oxygen and air and / or any other inert gas, can be used in the same manner as, or in addition to, the ways in which air can be used. Optionally, the reaction vessel can be purged of gases other than oxygen and maintained such that only oxygen, or a mixture of oxygen and one or more other selected gases, such as nitrogen, helium, neon, argon, krypton, xenon, etc., is present during the reaction in a selected ratio. Such methods are well within the scope of the skill of those skilled in the art considering this specification. When pressure is used in the reactions herein, the oxygen pressure can be in the range of about 1 atmosphere (0 psig) to 5000 psig, including, for example, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 75, 100, 250, 500, and 1000 psig, preferably 0 to 75 psig, more preferably 10 to 30 psig.

[0024] This reaction is photocatalyzed in the presence of oxygen, which means that the reactants are irradiated in the presence of one or more photocatalysts. The photocatalyst need not be soluble in the solvent if a solvent is used in the reaction.

[0025] The photocatalyst can be tungstic acid or a salt thereof. Exemplary tungstic acids include H2WO4 and H3PW 12 O 40 and the like. Exemplary tungstates include tetra-n-butylammonium decatungstate (TBADT), sodium decatungstate (NaDT), calcium tungstate (CaWO4), potassium tungstate (K2WO4), lithium tungstate (Li2WO4), sodium tungstate (Na2WO4), ammonium tungstate ((NH4) 10H2(W2O7)6), cadmium tungstate (Cd2WO4), ammonium paratungstate ((NH4) 10 H2(W2O7)6·xH2O), sodium polytungstate (3Na2WO4·9WO3·H2O), (Bu4N)3PW 12 O 40 、(NH4)6P2W 18 O 62 、and (Bu4N)2W6O 19 are mentioned. For example, see Angew. Chem. Int. Ed. Engl. 27, 1988, 1526 - 1527, which is incorporated herein by reference in its entirety.

[0026] A preferred photocatalyst for use in the reactions described herein is a salt of the decatungstate anion (W 10 O 32 -4 ,"decatungstate"). Counterions therefor include, for example, sodium, lithium, potassium, iron, magnesium, calcium, strontium, barium, aluminum, tin, manganese, cobalt, lead, nickel, copper, silver, gold, zinc, mercury, phosphonium, imidazolium, pyrrolidinium, piperidinium, pyridinium, ammonium, and (C1 - C8 alkyl) 1-4 substituted phosphonium, imidazolium, pyrrolidinium, piperidinium, pyridinium, and ammonium, but are not limited thereto, and the substituents may be the same or different. A preferred decatungstate compound herein is tetrabutylammonium decatungstate (TBADT). For example, see Tzirakis et.al, Chem. Soc. Rev., 2009, 38, 2609 - 262 and Laudadio et al., Science, 2020 Jul 3, 369(6499):92 - 96, both of which are incorporated herein by reference in their entirety. Two or more decatungstate compounds can be used to provide the decatungstate anion in the reactions described herein.

[0027] Other inorganic photocatalysts (e.g., metal chlorides) and organic photocatalysts (e.g., organic benzophenone derivatives) can also be used. Examples include benzophenone, bis(4-(trifluoromethyl)phenyl)methane, bis(4-chlorophenyl)methane, (4-methoxyphenyl)(4-(trifluoromethyl)phenyl)methane, acetophenone, 9H-fluorene-9-one, phenanthrene-9,10-dione, pentacene-5,7,12,14-tetraone, 2-oxo-2-phenylacetic acid, 3a,5a-dihydropyrene-1,6-dione, anthracene-9,10-dione, 2-chloroanthraquinone, xanthone, thioxanthone, FeCl3·6H2O, FeCl2·4H2O, CuCl2, and (TEA)2CeCl6.

[0028] The concentration or amount of the photocatalyst used in the reaction described herein is not particularly limited and can vary within a wide range. Considering the present disclosure, one skilled in the art can determine the amount used based on reaction conditions and the like. For example, decatungstate at a concentration of 0.01 - 30 mM can be used, including 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 15, 20, 25 mM, etc. If the photocatalyst does not dissolve completely or at all in the solvent and / or reactants when present, the amount of the photocatalyst used is not limited. For example, it can be an amount that would result in the above concentrations when dissolved. However, it can be more or less than this amount and can depend on the physical form of the catalyst, the amount of surface area exposed to the reaction medium, etc.

[0029] In the method for producing the compound of formula (3), the compound of formula (3’), or both described herein, the compound of formula (1) is oxidized by a photocatalytic reaction, i.e., irradiated in the presence of oxygen, a photocatalyst (such as tungstic acid and / or its salts), and optionally a solvent to produce at least one of compounds (3) and (3’):

Chemical formula

Chemical formula

[0030] For example, the compound of formula (3) can be converted to the compound of formula (3’) by reaction with trimethyl phosphite (reducing agent), heating, etc. The compound of formula (3’) can be converted to the compound of formula (2) by dehydration, etc., using well-known reactions, methods, etc. as described, for example, in European Patent Application Publication No. 0941984A2, U.S. Patent No. 10,138,306B1, and Pirmorade et al., ACS Sustainable Chem. Eng. 2017, 5, 1517 - 1527, all of which are incorporated herein by reference. Other catalytic, chemical, etc. methods for converting the compounds of formula (3) and formula (3’) to the compound of formula (2) can be used.

[0031] In a preferred embodiment of the present specification, without being bound by theory, the process of the present invention for reacting the compound of formula (1) to prepare the compounds of formula (3), (3’), and (2) is shown below, for example, using the preparation of methacrylic acid (MAA) from isobutyric acid (IBA) in the presence of oxygen and tetrabutylammonium decatungstate (TBADT) photocatalyst (a similar process for preparing methyl methacrylate (MMA) from methyl isobutyrate (MIB), etc. can be shown):

Chemical formula

[0032] The products of the reactions herein can be isolated by conventional procedures well known to those skilled in the art, including distillation, chromatography, filtration, extraction, etc.

[0033] As will be appreciated by those skilled in the art, all reaction variables such as the type of photocatalyst, the amount of photocatalyst added to the reaction mixture, oxygen pressure, irradiance, temperature, solvent, and reaction time can affect the photocatalytic process described herein.

[0034] The reaction rate depends strongly on the irradiance. Increasing the irradiance generally increases the reaction rate. For example, as shown in FIGS. 1A - 1B, an irradiance of about 300 mW / cm 2 dramatically increased the conversion rates of both IBA and MIB compared to the low irradiance of about 20 or 60 mW / cm 2 . The higher reaction rate due to higher irradiance did not result in a lower selectivity for the desired products for both IBA and MIB. Instead, as shown in FIGS. 2A - 2B, the selectivity was equivalent at the same conversion but at different irradiances.

[0035] A reasonable selectivity for the desired products is generally maintained at a high conversion of MIB, as shown in FIG. 2B. However, as shown in FIG. 2A, the higher the conversion rate of IBA, the lower the selectivity for the desired products tends to be.

[0036] The choice of solvent also affects the conversion rate of the reactants and the selectivity of the desired product. In one embodiment, four solvents, acetonitrile (MeCN), acetone, water, and dimethyl sulfoxide (DMSO), were evaluated when preparing MAA from IBA and when preparing MMA from MIB in the presence of oxygen and TBADT. To facilitate the quantification and identification of the products, deuterated solvents, namely MeCN-d3, acetone-d6, D2O, and DMSO-d6, were used. TBADT is readily soluble in MeCN-d3 and DMSO-d6 but is completely insoluble in acetone-d6 and D2O. As shown in FIGS. 3A and 3B, it was found that MeCN-d3 and acetone-d6 gave good IBA or MIB conversion rates compared to D2O and DMSO-d6. Compared to MeCN-d3, acetone-d6 showed a higher conversion rate of the reactants, however, the selectivity of the desired products of hydroperoxides and hydroxy compounds using acetone-d6 was lower. In addition, in this study, generally, the higher the solvent ratio (e.g., 90%), the higher the conversion rate.

[0037] Among the photocatalysts evaluated for the processes described herein, decatungstates such as TBADT show excellent performance regarding the conversion rate and overall selectivity of the desired products. A large amount of photocatalyst may have solubility problems when a solvent is used in the reaction. Therefore, an excessive amount of photocatalyst is not desirable. For the conversion of IBA or MIB, for example, a TBADT loading of 0.5 mM to 2 mM can be used in certain embodiments.

[0038] An overly low oxygen environment gives low conversion rates and selectivities, while a high oxygen pressure does not necessarily result in a high conversion rate. In certain embodiments, air (containing about 80% N2 and about 20% O2) gives better performance than pure oxygen. In certain embodiments, a higher oxygen pressure leads to a decrease in the conversion rate. For the conversion of IBA or MIB, the oxygen pressure is preferably from 1 atmosphere (0 psig) to 75 psig, more preferably from 0 to 40 psig, and even more preferably from 0 to 20 psig.

[0039] In certain embodiments, the reactions described herein are less sensitive to temperature when the v / v ratio of reactants (such as IBA, MIB, etc.) to the solvent is less than 50 / 50. In certain embodiments, the conversion rate of the reactants can increase as the temperature increases. In certain embodiments, high temperatures may tend to increase the selectivity of by-products, while in certain embodiments, lower temperatures tend to improve the selectivity for the desired product.

[0040] In certain embodiments, at the same irradiance, a higher conversion rate (95% or more) of the reactants can be achieved with a longer reaction time (such as 65, 70, 80, 90, 100, 120, 140 hours or more). As described above, higher irradiance significantly shortens the reaction time required to achieve a high conversion rate of the reactants.

[0041] In addition, in certain embodiments, a photoreaction using a flow reactor achieves better performance (lower irradiance with a shorter reaction time, higher product selectivity, higher selectivity for the desired product, higher conversion rate, etc.) than one using a batch reactor under similar reaction conditions.

Examples

[0042] Typical reaction procedures, reaction configurations, and result evaluations When preparing the examples using a batch reactor, typically, a glass tube (pressure rating = 150 psi, Ace Glass part #8648-62, volume 9 ml) was charged with a stir bar and a photocatalyst. Reactants (IBA or MIB) (containing 1,4-bis(trifluoromethyl)benzene as an internal standard to quantify the conversion of the reactants and the selectivity of the desired products and by-products) and a solvent were pipetted into the glass tube prior to the reaction. These reagents were introduced under ambient atmosphere without degassing such that the glass tube initially contained air at 1 atm (about 20% O2 and about 80% N2). The glass tube was then sealed and pure oxygen or additional air was introduced. The glass tube was irradiated with a Kessil PR160L-370 LED light (370 nm) or a Lumidox® Gen II 96-well LED array (365 nm) from Analytical Sales and Services. The reaction temperature was maintained by circulating a coolant around the glass tube. The reaction mixture was stirred and irradiated until the reaction time elapsed.

[0043] An exemplary configuration when using a flow photoreactor for the photoreaction is shown in Figure 4. Two flow photoreactors irradiated with LED light were connected in series, and a liquid sample (reactants (IBA or MIB) containing 1,4-bis(trifluoromethyl)benzene as a solvent and an internal standard) and a gas sample (oxygen and / or air) were continuously administered to a syringe pump and a mass flow controller, respectively. The liquid and gas samples were mixed in a Y-type mixer to create distinct gas-liquid segments before passing through the photoreactor. The gas / liquid ratio (G / L ratio) was controlled by the flow rates of the gas and the liquid. The system pressure was adjusted by a back pressure regulator (BPR) positioned after the photoreactor. At the end of the reaction, the sample was collected in an ice bath-cooled vial containing d-acetonitrile.

[0044] For example, different configurations were achieved by adjusting the LED output and the distance between the LED light and the glass tube, and various irradiances were achieved. For example, a Lumidox® Gen II 96-well LED array at a proximity distance of about 0.5 cm from the glass tube achieved an irradiance of about 300 mW / cm 2 and a Kessil PR160L-370 LED light positioned about 10 cm from the glass tube achieved an irradiance of about 60 mW / cm 2 and a Kessil PR160L-370 LED light positioned about 12 cm from the glass tube achieved an irradiance of about 20 mW / cm 2 . By using a higher LED output and / or placing the LED array closer to the glass tube, higher irradiances (e.g., 400 and 900 mW / cm 2 ) can be achieved.

[0045] The photocatalytic process was evaluated by measuring the conversion rate of the reactants, the total selectivity, the selectivity for the desired products of hydroperoxides and hydroxy compounds, the selectivity for the by-products of acetic acid and acetone, and the total turnover number (TON) of the photocatalyst. A high TON represents good stability of the photocatalyst.

[0046] Reactions under different conditions In one embodiment using TBADT as the photocatalyst, the results of IBA under different reaction conditions (Examples 1-17) using a batch reactor and the results of MIB under different reaction conditions (Examples 18-35) are shown in Tables 1 and 2, respectively. In these examples, deuterated acetonitrile (d-MeCN) or deuterated acetone (d-acetone) was used as the solvent, and except for Example 1 in Table 1 and Example 18 in Table 2, the irradiance (measured by Ophir Photonics (part numbers: 7Z02480 PD300RM-8W and 7Z01565 StarLite) unless otherwise specified) was in the range of 20-60 mW / cm 2 . Example 1 in Table 1 and Example 18 in Table 2 had an irradiance of 300 mW / cm 2prepared at about 100 mW / cm 2 (estimated from light intensity measurement) irradiance. In addition, as shown in Table 1, air was used as the oxidant in the preparation of Example 17 instead of pure oxygen.

[0047] Specific observations can be made regarding this embodiment with respect to the effects of the filling amount of TBADT, the solvent, the amount of solvent used in the reaction mixture, the oxygen pressure, the temperature, and the reaction time on the performance of the photocatalytic reaction.

[0048] In particular, the conversion rate of IBA or MIB did not strongly depend on the filling amount of TBADT, indicating the stability of TBADT. Generally, 0.5 mM or 2 mM of TBADT gave good and comparable performance. However, perhaps due to the low solubility of the photocatalyst in the solvent, lower performance (e.g., indicated by a lower TON) was observed at a high filling amount of 4 mM (see, for example, Example 14 in Table 1 and Example 34 in Table 2). Generally, the stability of TBADT was good, as demonstrated by the increase in the conversion rate of the reactants and the increase in TON with an increase in the reaction time (see, for example, Example 27 vs. Example 29 in Table 2).

[0049] When a solvent was used, the conversion rate of the reactants was related to the concentration of the reactants in the solution. For example, from the comparison of Example 4 vs. Example 5 in Table 1 and Example 22 vs. Example 23, Example 25 vs. 26, and Example 29 vs. Example 30 in Table 2, it can be seen that generally, the higher the solvent ratio, the higher the conversion rate of the reactants.

[0050] The conversion rate and selectivity were also solvent-dependent. Both acetonitrile and acetone were able to promote a higher conversion rate of IBA and a higher conversion rate of MIB compared to water and dimethyl sulfoxide. Between acetonitrile and acetone, d-MeCN showed a higher selectivity for the desired products (i.e., 2-HIBA and 2-IBA-OOH) for IBA than d-acetone, as shown by the comparison between Example 10 and Example 15 in Table 1 and the comparison between Example 11 and Example 16. The same observation can be made for MIB (see, for example, Example 27 vs. Example 35 in Table 2).

[0051] The influence of temperature on the MIB conversion rate in this embodiment seemed to be related to the reactant filling amount. For the 50% MIB / 50% d-MeCN solution, the conversion rate increased significantly from 10.7% (Example 22) to 41.4% (Example 28) when the temperature was raised from 10 °C to 50 °C. However, when there was more solvent relative to the reactants (e.g., 10% MIB / 90% d-MeCN solution), the reaction seemed to be less sensitive to temperature changes. In addition, low temperatures such as 0 °C and 10 °C seemed to improve the selectivity for the desired products of 2-HMIB and 2-MIB-OOH (see, for example, Examples 18 - 23 in Table 2).

[0052] In the case of IBA, the temperature did not seem to have much effect on the conversion rate in this embodiment, regardless of the reactant filling amount relative to the solvent. However, as in the case of MIB, low temperatures (e.g., 0 °C) generally tended to have a higher selectivity for the desired products of 2-HIBA and 2-IBA-OOH than high temperatures (e.g., Examples 1 and 2 in Table 1).

[0053] An overly low oxygen environment tended to give low conversion rates and low selectivities in this embodiment. However, when sufficient oxygen was supplied initially or when oxygen was supplied continuously, the oxygen pressure did not seem to affect the results of both IBA and MIB much. For example, at oxygen pressures of 10 psig and 20 psig, the conversion rates and overall selectivities were nearly the same (see, e.g., Example 6 vs. Example 10 and Example 7 vs. Example 11 in Table 1, Example 24 vs. Example 31, Example 25 vs. Example 32, and Example 27 vs. Example 33 in Table 2). As demonstrated by Example 17 in Table 1, it was also found that air generally functions better than pure oxygen, especially with respect to the selectivity of the desired product.

[0054] The examples also show that higher conversion rates can be achieved with longer reaction times (see Example 27 vs. Example 29 in Table 2), which indicates the robustness of the TBADT photocatalyst.

[0055]

Table 1

[0056]

Table 2

[0057] Reactions using different photocatalysts In other embodiments, in addition to TBADT, four organic photocatalysts, namely benzophenone, xanthone, thioxanthone, and 2-chloroanthraquinone, and the inorganic photocatalyst FeCl3·6H2O were evaluated for the activation of the C(sp 3 )-H bond of IBA or MIB.

[0058] In these examples, each photocatalyst in an amount of 2 mM was added to the reactant solution in deuterated acetonitrile (d-MeCN, 90% v / v). The reaction was carried out in a Hepatochem batch reactor under LED light irradiation at 370 nm (20 - 60 mW / cm 2was carried out at 0 °C for 16 hours using an irradiance of) and 20 psig of O2. The results are 1 analyzed by 1H-NMR and shown in Tables 3 (Examples 2 and 36 to 40) and 4 (Examples 41 to 46) for IBA and MIB, respectively.

[0059]

Table 3

[0060]

Table 4

[0061] Compared with TBADT, FeCl3·6H2O showed high conversion rates for both IBA and MIB, however, the selectivity of the desired product to by-products was generally low.

[0062] Comparison of reactions using batch reactors and flow reactors By comparing Examples 47 and 48 for IBA and Examples 49 and 50 for MIB, the performance of using flow reactors versus batch reactors for both IBA and MIB was evaluated under similar reaction conditions (Table 5).

[0063] The reaction solutions of these examples contained 90% d-acetonitrile and 10% IBA or MIB. All reactions occurred at a temperature of 25 °C and an oxygen pressure of 20 psig using light with an irradiation wavelength of 365 nm and TBADT (2 mM) as the photocatalyst. When using a flow reactor (i.e., Examples 47 and 49), a G / L ratio of 10 was applied to ensure that a sufficient amount of O2 was introduced, the gas flow rate was 0.1 mL / min, and the liquid flow rate was 0.01 mL / min. The conversion rate (concentration (%)) of the reactants and the selectivity (selectivity (%)) for the desired product were 1 quantified by 1H-NMR.

[0064]

Table 5

[0065] Generally speaking, a flow reactor is superior to a batch reactor, and higher conversion rates of reactants and / or higher selectivity for the desired product can be obtained with a shorter reaction time and a lower irradiance.

[0066] As an alternative to the flow reactors examined here, for example, a bubble column (batch or semi-batch) for scaling up the conversion from IBA to MAA can be considered, especially when only low O2 or air pressure is required.

[0067] Considering the balance of factors such as the conversion rate of reactants, the selectivity of the desired product, irradiance, and reaction time, Examples 1, 2, 17 to 20, and 49 described above can be mentioned.

[0068] Preferred embodiments that are fully described and can be implemented by those skilled in the art based on this specification include the following:

[0069] 1. A method comprising irradiating a compound of formula (1) with an irradiance of 1 mW / cm to 10,000 mW / cm having a wavelength of 200 to 500 nm in the presence of oxygen and a photocatalyst, 2 ~10,000mW / cm 2 wherein,

Chemical formula

[0070] 2. A method for preparing the compound of formula (3), the compound of formula (3’), or both from the compound of formula (1), comprising oxidizing the compound of formula (1) by a photocatalytic reaction in the presence of oxygen and a photocatalyst:

Chemical formula

[0071] 3. A method for preparing the compound of formula (2), comprising preparing the compound of formula (3) and / or the compound of formula (3’) by the method described in Embodiment 2, and converting the compound of formula (3) and / or the compound of formula (3’) into the compound of formula (2):

Chemical formula

[0072] 4. The method according to any one of Embodiments 1 to 3, wherein the compound of formula (1) is at least one selected from the group consisting of propionic acid, butyric acid, pentanoic acid, hexanoic acid, isobutyric acid, 2-methylbutyric acid, 2-methylpentanoic acid, 2-methylhexanoic acid, and methyl esters thereof.

[0073] 5. The method according to Embodiment 3, wherein the compound of formula (1) is isobutyric acid and the compound of formula (2) is methacrylic acid.

[0074] 6. The method according to Embodiment 3, wherein the compound of formula (1) is methyl isobutyrate and the compound of formula (2) is methyl methacrylate.

[0075] 7. The method according to any one of Embodiments 1 to 6, wherein the photocatalyst contains at least one selected from the group consisting of an inorganic photocatalyst and an organic photocatalyst.

[0076] 8. The method according to any one of Embodiments 1 to 7, wherein the photocatalyst contains at least one inorganic photocatalyst selected from the group consisting of tungstic acid and salts of tungstic acid.

[0077] 9. The photocatalyst is tetrabutylammonium decatungstate, sodium decatungstate, calcium tungstate, potassium tungstate, lithium tungstate, sodium tungstate, ammonium tungstate, cadmium tungstate, ammonium paratungstate, sodium polytungstate, (Bu4N)3PW 12 O 40 、(NH4)6P2W 18 O 62 、(Bu4N)2W6O 19 、FeCl3·6H2O, FeCl2·4H2O, CuCl2, and at least one inorganic photocatalyst selected from the group consisting of (TEA)2CeCl6. The method according to any one of Embodiments 1 to 8.

[0078] 10. The method according to any one of Embodiments 1 to 9, wherein the photocatalyst contains a decatungstate.

[0079] 11. The method according to any one of Embodiments 1 to 10, wherein the photocatalyst contains tetrabutylammonium decatungstate.

[0080] 12. The method according to any one of Embodiments 1 to 11, wherein the photocatalyst contains at least one organic photocatalyst selected from the group consisting of benzophenone, bis(4-(trifluoromethyl)phenyl)methane, bis(4-chlorophenyl)methane, (4-methoxyphenyl)(4-(trifluoromethyl)phenyl)methane, acetophenone, 9H-fluorene-9-one, phenanthrene-9,10-dione, pentacene-5,7,12,14-tetraone, 2-oxo-2-phenylacetic acid, 3a,5a-dihydropyrene-1,6-dione, anthracene-9,10-dione, 2-chloroanthraquinone, xanthone, and thioxanthone.

[0081] 13. The method according to any one of Embodiments 1 to 12, wherein the amount of the photocatalyst is 0.5 mM or more and less than 4 mM.

[0082] 14. The method according to any one of Embodiments 1 to 13, wherein the photocatalytic reaction occurs by irradiation with light having a wavelength in the range of 300 nm to 425 nm and an irradiance in the range of 10 mW / cm 2 ~400 mW / cm 2 of the range.

[0083] 15. The method according to any one of Embodiments 1 to 14, wherein the photocatalytic reaction occurs at an oxygen pressure in the range of 0 psig to 20 psig.

[0084] 16. The method according to any one of Embodiments 1 to 15, wherein the photocatalytic reaction occurs in the presence of a solvent.

[0085] 17. The method according to any one of Embodiments 1 to 16, wherein the solvent contains at least one of acetonitrile and acetone.

[0086] The above written description of the present invention provides a way and process of making and using it so as to enable those skilled in the art to make and use it, and this possibility is provided especially for the subject matter of the appended claims that form part of the original description. This description is provided in the context of a particular use and its requirements. Various changes to the embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and uses without departing from the spirit and scope of the present invention. Accordingly, the present invention is not intended to be limited to the embodiments shown, but rather to be accorded the widest scope consistent with the principles and features disclosed herein. In this regard, specific embodiments within the present invention do not necessarily represent all of the broadly contemplated benefits of the present invention.

Claims

1. In the presence of oxygen and a photocatalyst, irradiating a compound of formula (1) with an irradiance of 1 mW / cm ２ to 10,000 mW / cm ２ having a wavelength of 200 to 500 nm, which method comprises: 【Chemical 1】 wherein, R １ , R ２ , and R ３ each independently represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, X is -OR ａ or NR ｂ R ｃ represents a monovalent group represented by, and R ａ R ｂ , and R ｃ each independently represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, a method.

2. A method for preparing a compound of formula (3), a compound of formula (3'), or both from a compound of formula (1), said method comprising oxidizing the compound of formula (1) by a photocatalytic reaction in the presence of oxygen and a photocatalyst, 【Chemical 2】 In the formula, R １ , R ２ , and R ３ each independently represent a hydrogen atom or an organic group having 1 to 20 carbon atoms. X is -OR ａ or NR ｂ R ｃ represents a monovalent group represented by, and R ａ , R ｂ , and R ｃ each independently represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, a method.

3. A method for preparing a compound of formula (2), comprising preparing a compound of formula (3) and / or a compound of formula (3') by the method according to claim 2, and converting the compound of formula (3) and / or the compound of formula (3') into the compound of formula (2), 【Chemical Formula 3】 wherein R in the above formula (2) １ , R ２ , R ３ , and X are the same as those contained in the compound of the above formula (1), method.

4. The method according to any one of claims 1 to 3, wherein the compound of formula (1) is at least one selected from the group consisting of propionic acid, butyric acid, pentanoic acid, hexanoic acid, isobutyric acid, 2-methylbutyric acid, 2-methylpentanoic acid, 2-methylhexanoic acid, and their methyl esters.

5. The method according to claim 3, wherein the compound of formula (1) is isobutyric acid and the compound of formula (2) is methacrylic acid.

6. The method according to claim 3, wherein the compound of formula (1) is methyl isobutyrate and the compound of formula (2) is methyl methacrylate.

7. The method according to any one of claims 1 to 6, wherein the photocatalyst comprises at least one selected from the group consisting of inorganic photocatalysts and organic photocatalysts.

8. The method according to any one of claims 1 to 7, wherein the photocatalyst comprises at least one inorganic photocatalyst selected from the group consisting of tungstic acid and salts of tungstic acid.

9. The photocatalyst includes at least one inorganic photocatalyst selected from the group consisting of tetrabutylammonium decatungstate, sodium decatungstate, calcium tungstate, potassium tungstate, lithium tungstate, sodium tungstate, ammonium tungstate, cadmium tungstate, ammonium paratungstate, sodium polytungstate, (Bu ４ N) ３ PW １２ O ４０ , (NH ４ ) ６ P ２ W １８ O ６２ , (Bu ４ N) ２ W ６ O １９ , FeCl ３ ·6H ２ O, FeCl ２ ·4H ２ O, CuCl ２ , and (TEA) ２ CeCl ６ ; the method according to any one of claims 1 to 8.

10. The method according to any one of claims 1 to 9, wherein the photocatalyst comprises decatungstate.

11. The method according to any one of claims 1 to 10, wherein the photocatalyst comprises tetrabutylammonium decatungstate.

12. The method according to any one of claims 1 to 11, wherein the photocatalyst contains at least one organic photocatalyst selected from the group consisting of benzophenone, bis(4-(trifluoromethyl)phenyl)methane, bis(4-chlorophenyl)methane, (4-methoxyphenyl)(4-(trifluoromethyl)phenyl)methane, acetophenone, 9H-fluorene-9-one, phenanthrene-9,10-dione, pentacene-5,7,12,14-tetraone, 2-oxo-2-phenylacetic acid, 3a,5a-dihydropyrene-1,6-dione, anthracene-9,10-dione, 2-chloroanthraquinone, xanthone, and thioxanthone.

13. The method according to any one of claims 1 to 12, wherein the amount of the photocatalyst is 0.5 mM or more and less than 4 mM.

14. The photocatalytic reaction occurs by irradiation with light having a wavelength in the range of 300 nm to 425 nm and an irradiance in the range of 10 mW / cm ２ to 400 mW / cm ２ The method according to any one of claims 1 to 13.

15. The method according to any one of claims 1 to 14, wherein the photocatalytic reaction occurs at an oxygen pressure in the range of 0 psig to 20 psig.

16. The method according to any one of claims 1 to 15, wherein the photocatalytic reaction occurs in the presence of a solvent.

17. The method according to any one of claims 1 to 16, wherein the solvent contains at least one of acetonitrile and acetone.

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