A method for preparing cedarwood alkalone by utilizing MTO catalysis

Abstract

The invention discloses a method for preparing cedarwood alkanone by using MTO (methyl trioxide rhenium) catalysis, and belongs to the technical field of fine organic chemical synthesis. Under the action of MTO catalyst, the method uses 3-methylpyrazole as a basic ligand to oxidize cedarwood ene to obtain cedarwood alkanone. The present invention uses MTO as a catalyst, has good solubility and thermal stability and is green and environmentally friendly; using 3-methylpyrazole as a basic ligand reduces side reactions in the reaction, increases alkane selectivity, and greatly improves the yield of the target product; the prepared cedarwood alkanone has a sweet woody and ambergris flavor, a valuable and lasting aroma, high stability, and a good prospect for industrial application, and can be used in daily flavors such as perfume, soap, and cosmetic flavors.

Description

Technical Field

[0001] The invention belongs to the technical field of fine organic chemical synthesis, and specifically relates to a method for preparing cedarwood alkalone by utilizing MTO (methyl rhenium trioxide) catalysis. Background Art

[0002] Logrove cedarwood ketone is a sesquiterpene ketone compound, a colorless to light yellow oily liquid with a very sweet woody and ambergris scent. The aroma is precious and long-lasting. It can be used to formulate daily flavors such as woody and ambergris flavors, and can also be used in the preparation of perfume, leather, and tobacco.

[0003] At present, cedarwood alkanone fragrances are mainly synthesized by oxidation of α, β-cedrene as raw materials. The obtained cedarwood alkanone products have a pungent smell, a weak animal aroma, and average quality. However, cedarwood alkanone synthesized from cedarwood oleoresin has a strong aroma and the valuable aroma characteristics of musk and ambergris. Both cedarwood oleoresin and α, β-cedrene are derived from cedarwood oil, but α, β-cedrene has been studied more in the synthesis of high-end cedarwood fragrances, while cedarwood oleoresin has not been well utilized.

[0004] There are studies abroad reporting that cedarwood ene synthesizes cedarwood alkanone by oxidation, but it is mainly a synthetic route with organic peroxyacid as an oxidant. Due to the unstable and highly corrosive properties of organic peroxyacid, there are problems of low product yield and environmental pollution, which are restricted in use. In the previous research results of the applicant, CN111499502A, a synthetic method of cedarwood alkanone is disclosed, and the main steps include: preparing quaternary ammonium phosphotungstic acid salt with phosphotungstic acid and hexadecyltrimethylammonium chloride as raw materials, and loading the quaternary ammonium phosphotungstic acid salt on activated carbon to prepare an activated carbon-supported quaternary ammonium phosphotungstic acid catalyst; under the action of the activated carbon-supported quaternary ammonium phosphotungstic acid catalyst, cedarwood ene is subjected to oxidation reaction to obtain cedarwood alkanone; the method uses activated carbon-supported quaternary ammonium phosphotungstic acid salt as a catalyst, which can improve the stability of the catalyst, facilitate the regeneration and recycling of the catalyst, reduce the discharge of waste materials, is beneficial to the environment, and the synthetic method is simple, has little corrosion to equipment, is safe and environmentally friendly, and has low cost. This method can effectively solve the problems existing in the existing foreign preparation process of cedarwood alkanone, and the obtained product has high purity and a high conversion rate of cedarene. However, in this method, the yield of cedarwood alkanone products still has room for improvement. Therefore, further developing a synthetic method with a high yield of cedarwood alkanone has important research value and industrial application prospects. Summary of the invention

[0005] In view of the above problems existing in the prior art, the technical problem to be solved by the present invention is to provide a method for preparing cedarwood alkalone using MTO catalysis, which further improves the yield of the target product cedarwood alkalone on the basis of ensuring product purity and raw material conversion rate.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing cedarwood alkanone by utilizing MTO catalysis: under the action of MTO catalyst, cedarwoodene is oxidized with 3-methylpyrazole as a basic ligand to obtain cedarwood alkanone.

[0008] The method for preparing cedarwood alkanone by using MTO catalysis is specifically as follows: adding cedarwood alkene, MTO, 3-methylpyrazole and an organic solvent into a reactor, stirring under temperature control, slowly adding 30% H2O2 to react; after the reaction is completed, cooling to room temperature, extracting to obtain an organic phase, washing to neutrality, distilling to recover the solvent, and then vacuum distilling to obtain a crude cedarwood alkanone product. The crude product is subjected to column chromatography to obtain cedarwood alkanone with high purity, which is characterized by GC-MS.

[0009] The organic solvent is selected from ethanol, dichloromethane, 1,2-dichloroethane and ethyl acetate.

[0010] The molar ratio of the cedarwood ene to 30% H2O2 is 1:(1-5).

[0011] The mass ratio of the cedarwood ene to MTO is 1:(0.1-0.5%).

[0012] The mass ratio of the cedarwood ene to 3-methylpyrazole is 1: (6-10%).

[0013] The temperature was controlled at 20-40°C and the reaction time was 2-4h.

[0014] The method for preparing cedarwood alkanone by using MTO catalysis comprises extracting with ethyl acetate, separating the organic phase, washing with 10% Na2CO3 solution, distilled water and saturated NaCl solution in sequence until neutral, distilling and recovering the solvent, and then performing vacuum distillation to obtain a crude cedarwood alkanone product. The crude product is subjected to column chromatography to obtain cedarwood alkanone with high purity. The purified product is not used to calculate the product yield, but is used for GC-MS and nuclear magnetic resonance characterization.

[0015] This method uses methyl trioxide rhenium as a catalyst, but the catalytic system has the defect of easily producing diols and other products. Therefore, the basic ligand 3-methylpyrazole is added to reduce the acidity of the rhenium atom at the center of MTO, while improving the selectivity and yield of cedarwood alkalone in the reaction.

[0016] Beneficial effects: Compared with the prior art, the advantages of the present invention are:

[0017] 1) The present invention uses methyltrioxide rhenium as a catalyst, which has excellent catalytic performance, good solubility and thermal stability, and uses 3-methylpyrazole as a basic ligand to reduce side reactions in the reaction, increase the selectivity of alkanone, and greatly improve the yield.

[0018] 2) The cedarwood alkalone of the present invention has a very sweet woody and ambergris aroma, a valuable aroma, a long lasting fragrance, and high stability;

[0019] 3) The preparation process of the present invention is simple, the reaction time is short, and it is green and environmentally friendly, and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the mass spectrum of the cedarwood ketone synthesized in this application. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with specific examples. The raw material cedarwood used in the following examples and comparative examples has a cedarwood content of 68%; the calculation formula for the relevant results is as follows:

[0022] Yield calculation: Yield (%) = product amount (g) * product content / theoretical product amount (g);

[0023] Theoretical product amount (g) = raw material amount (g) * raw material content * cedarwood alkane molecular weight / cedarwood alkene molecular weight;

[0024] Conversion rate (%) = product amount (g) * (1-product content) / raw material amount (g) * raw material content;

[0025] Example 1

[0026] 6.12 g of cedarwood (content 68%), 0.018 g of methylrhenium trioxide, 0.612 g of 3-methylpyrazole, and 15 mL of ethanol were added to a reactor, and 6.8 g of 30% H2O2 was slowly dripped into the reactor, followed by stirring at 30°C for 3 h. After the reaction was completed, the reaction solution was extracted with ethyl acetate (3*50mL); the organic phase was washed with 10% Na2CO3 solution (3*50mL), deionized water (3*50mL), and saturated sodium chloride solution (3*50mL) in sequence; the organic phase was dehydrated with anhydrous sodium sulfate, the solvent was recovered by distillation, and then vacuum distillation was performed to obtain 3.14g of a crude product of cedarwood alkalone. Gas chromatography analysis showed that the cedarwood alkalone content was 81.9%. It was calculated that the cedarwood alkalone yield was 57.3%, and the cedarwood alkalone conversion rate was 76.8%; the crude product was subjected to column chromatography to obtain cedarwood alkalone with a purity of 94.6%, which was determined to be cedarwood alkalone by GC-MS characterization.

[0027] Example 2

[0028] 6.12 g of cedarwood (content 68%), 0.018 g of methylrhenium trioxide, 0.612 g of 3-methylpyrazole, and 15 mL of dichloromethane were added to a reactor, and 6.8 g of 30% H2O2 was slowly dripped into the reactor, followed by stirring at 30°C for 3 h. After the reaction was completed, the reaction solution was extracted with ethyl acetate (3*50mL); the organic phase was washed with 10% Na2CO3 solution (3*50mL), deionized water (3*50mL), and saturated sodium chloride solution (3*50mL) in sequence; the organic phase was dehydrated with anhydrous sodium sulfate, the solvent was recovered by distillation, and then vacuum distillation was performed to obtain 3.53g of a crude product of cedarwood alkane. Gas chromatography analysis showed that the cedarwood alkane content was 76.8%. It was calculated that the cedarwood alkane yield was 60.4%, and the conversion rate of cedarene was 80.7%; the crude product was subjected to column chromatography to obtain cedarwood alkane with a purity of 93.7%, which was determined to be cedarwood alkane by GC-MS characterization.

[0029] Example 3

[0030] 6.12 g of cedarwood (content 68%), 0.018 g of methylrhenium trioxide, 0.612 g of 3-methylpyrazole, and 15 mL of ethyl acetate were added to a reactor, and 6.8 g of 30% H2O2 was slowly dripped into the reactor, followed by stirring at 30°C for 3 h. After the reaction was completed, the reaction solution was extracted with ethyl acetate (3*50mL); the organic phase was washed with 10% Na2CO3 solution (3*50mL), deionized water (3*50mL), and saturated sodium chloride solution (3*50mL) in sequence; the organic phase was dehydrated with anhydrous sodium sulfate, the solvent was recovered by distillation, and then vacuum distillation was performed to obtain 3.84g of a crude product of cedarwood alkalone. Gas chromatography analysis showed that the cedarwood alkalone content was 73.2%. It was calculated that the cedarwood alkalone yield was 62.6%, and the cedarwood alkalone conversion rate was 81.3%; the crude product was subjected to column chromatography to obtain cedarwood alkalone with a purity of 94.1%, which was determined to be cedarwood alkalone by GC-MS characterization.

[0031] Example 4

[0032] 6.12 g of cedarwood (content 68%), 0.018 g of methylrhenium trioxide, 0.612 g of 3-methylpyrazole, and 15 mL of 1,2-dichloroethane were added to a reactor, and 6.8 g of 30% H2O2 was slowly dripped into the reactor, followed by stirring at 30°C for 3 h. After the reaction was completed, the reaction solution was extracted with ethyl acetate (3*50mL); the organic phase was washed with 10% Na2CO3 solution (3*50mL), deionized water (3*50mL), and saturated sodium chloride solution (3*50mL) in sequence; the organic phase was dehydrated with anhydrous sodium sulfate, the solvent was recovered by distillation, and then vacuum distillation was performed to obtain 5.16g of a crude product of cedarwood alkanone. Gas chromatography analysis showed that the cedarwood alkanone content was 62.9%. It was calculated that the cedarwood alkanone yield was 72.3%, and the cedarwoodene conversion rate was 96.7%; the crude product was subjected to column chromatography to obtain cedarwood alkanone with a purity of 94.8%, which was determined to be cedarwood alkanone by GC-MS characterization.

[0033] Example 5

[0034] Take 6.12g of cedarwood (content 68%), 0.018g of methylrhenium trioxide, 0.612g of 3-methylpyrazole, and 15mL of 1,2-dichloroethane, add them into the reactor, and slowly drip 6.8g of 30% H2O2 into the reactor, and then stir at 30°C for 2h. After the reaction was completed, the reaction solution was extracted with ethyl acetate (3*50mL); the organic phase was washed with 10% Na2CO3 solution (3*50mL), deionized water (3*50mL), and saturated sodium chloride solution (3*50mL) in sequence; the organic phase was dehydrated with anhydrous sodium sulfate, the solvent was recovered by distillation, and then vacuum distillation was performed to obtain 4.36g of a crude product of cedarwood alkalone. Gas chromatography analysis showed that the cedarwood alkalone content was 67.1%. It was calculated that the cedarwood alkalone yield was 65.2%, and the cedarwood alkalone conversion rate was 89.1%; the crude product was subjected to column chromatography to obtain cedarwood alkalone with a purity of 93.2%, which was characterized by GC-MS and determined to be cedarwood alkalone.

[0035] Example 6

[0036] Take 6.12g of cedarwood (content 68%), 0.018g of methylrhenium trioxide, 0.612g of 3-methylpyrazole, and 15mL of 1,2-dichloroethane, add them into the reactor, and slowly drip 6.8g of 30% H2O2 into the reactor, and then stir at 30°C for 4h. After the reaction was completed, the reaction solution was extracted with ethyl acetate (3*50mL); the organic phase was washed with 10% Na2CO3 solution (3*50mL), deionized water (3*50mL), and saturated sodium chloride solution (3*50mL) in sequence; the organic phase was dehydrated with anhydrous sodium sulfate, the solvent was recovered by distillation, and then vacuum distillation was performed to obtain 5.07g of a crude product of cedarwood alkalone. Gas chromatography analysis showed that the cedarwood alkalone content was 64.3%. It was calculated that the cedarwood alkalone yield was 71.6%, and the cedarwood alkalone conversion rate was 96.9%; the crude product was subjected to column chromatography to obtain cedarwood alkalone with a purity of 92.6%, which was determined to be cedarwood alkalone by GC-MS characterization.

[0037] The cedarwood ketone synthesized in the above example was characterized by gas chromatography-mass spectrometry (GC-MS): m / z = 220 [M] + ,like Figure 1 As shown, the molecular ion peak is 220, which is similar to C 15 H 24 O is completely consistent, the main fragment m / z is: 220, 192, 178, 163, 149, 137, 123, 107, 95, 81, 67, 55, 41; its molecular structure is as follows:

[0038]

[0039] Comparative Example 1

[0040] Synthesis of cedarwood alkane: 5g cedarwood ene (content 68%), 0.4g 20% ​​activated carbon supported phosphotungstate quaternary ammonium salt catalyst, 5mL30% H2O2 and 15mL acetone were added to the reactor and stirred at 60°C for 6h. After the reaction was completed, the reaction solution was extracted with ethyl acetate (3*50mL); the organic phase was washed with deionized water (3*50mL) and saturated sodium chloride solution (3*50mL) in turn; the organic phase was dehydrated with anhydrous sodium sulfate, and then vacuum distilled, and then vacuum distilled to obtain 4.1g of cedarwood alkane crude product. Gas chromatography analysis showed that the cedarwood alkane content was 42.8%. The cedarwood alkane yield was 47.9% and the conversion rate of cedarwood ene was 68.1%. The crude product was subjected to column chromatography to obtain cedarwood alkane with a purity of 94.6%.

[0041] Comparative Example 2

[0042] Synthesis of cedarwood alkanone: 5g cedarwood ene (content 68%), 0.4g 30% activated carbon supported phosphotungstate quaternary ammonium salt catalyst, 5mL 30% H2O2 and 15mL ethyl acetate were added to the reactor and stirred at 60°C for 6h. After the reaction was completed, the reaction solution was extracted with ethyl acetate (3*50mL); the organic phase was washed with deionized water (3*50mL) and saturated sodium chloride solution (3*50mL) in sequence; the organic phase was dehydrated with anhydrous sodium sulfate, and then vacuum distilled, and then vacuum distilled to obtain 4.8g of cedarwood alkanone crude product. Gas chromatography analysis showed that the cedarwood alkanone content was 65.7%, and the cedarwood alkanone yield was 65.7%, and the cedarwood ene conversion rate was 90.9%. The crude product was subjected to column chromatography to obtain cedarwood alkanone with a purity of 95.7%.

[0043] Comparative Example 3

[0044] Synthesis of cedarwood alkanone: 5g cedarwood ene (content 68%), 0.4g 40% activated carbon supported phosphotungstate quaternary ammonium salt catalyst, 5mL 30% H2O2 and 15mL dichloromethane were added to the reactor and stirred at 60°C for 6h. After the reaction was completed, the reaction solution was extracted with ethyl acetate (3*50mL); the organic phase was washed with deionized water (3*50mL) and saturated sodium chloride solution (3*50mL) in sequence; the organic phase was dehydrated with anhydrous sodium sulfate, then vacuum distilled, and then vacuum distilled to obtain 4.6g of cedarwood alkanone crude product. Gas chromatography analysis showed that the cedarwood alkanone content was 48.0%. The cedarwood alkanone yield was 60.2%, and the conversion rate of cedarwood ene was 85.6%. The crude product was subjected to column chromatography to obtain cedarwood alkanone with a purity of 95.1%.

[0045] Comparative Example 4

[0046] Synthesis of cedarwood alkanone: 5g cedarwood ene (content 68%), 0.4g 50% activated carbon supported phosphotungstate quaternary ammonium salt catalyst, 5mL 30% H2O2 and 15mL ethyl acetate were added to the reactor and stirred at 60°C for 6h. After the reaction was completed, the reaction solution was extracted with ethyl acetate (3*50mL); the organic phase was washed with deionized water (3*50mL) and saturated sodium chloride solution (3*50mL) in sequence; the organic phase was dehydrated with anhydrous sodium sulfate, then vacuum distilled, and then vacuum distilled to obtain 4.5g of cedarwood alkanone crude product. Gas chromatography analysis showed that the cedarwood alkanone content was 46.6%. The cedarwood alkanone yield was 57.2%, and the conversion rate of cedarwood ene was 81.7%. The crude product was subjected to column chromatography to obtain cedarwood alkanone with a purity of 94.3%.

[0047] The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements can be made without departing from the principle of the present invention. These improvements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing cedarwood alkalone using MTO catalysis, characterized in that: 6.12g of cedarene, 0.018g of methylrhenium trioxide, 0.612g of 3-methylpyrazole, and 15mL of 1,2-dichloroethane were added to a reactor, and 6.8g of 30% H2O2 was slowly dripped into the reactor, and then stirred at 30°C for 3h or 4h; after the reaction was completed, the reaction solution was extracted with ethyl acetate; the organic phase was washed with 10% Na2CO3 solution, deionized water, and saturated sodium chloride solution in sequence; the organic phase was dehydrated with anhydrous sodium sulfate, the solvent was recovered by distillation, and then vacuum distillation was performed to obtain a crude product of cedarwood alkanone; the crude product was subjected to column chromatography to obtain cedarwood alkanone, which was characterized by GC-MS and determined to be cedarwood alkanone.

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