Title of Invention	A VERSATILE PROCESS FOR THE OXIDATION OF CARBINOLS TO CARBONYLS USING TRIPHASE CATALYTIC CONDITION.
Abstract	The present invention described an efficient method for catalytic oxidation of carbinols with hydrogen peroxide using Amberlite basic resin (IR-400) in presence of sodium tungstate as catalyst at an ambient condition in a suitable solvent. This method is high yielding, clean, safe, operationally simple and cost effective. Synthesis of carbonyl compounds in an environment friendly way is a very important fundamental reaction and has long been a challenge to the organic chemists. Although several oxidants have been reported in the last few years, in the present day scenario of the environmental protection, many of the existing methods have to be reviewed or replaced owing to the demerits reflected from such agents. Most of the carbonyls obtained like benzophenone, acetophenone vanillin, geranic acid, benzaldehyde, cyclohexanone etc are used in perfumery, beverage, food, nylon etc industries

Title of Invention

A VERSATILE PROCESS FOR THE OXIDATION OF CARBINOLS TO CARBONYLS USING TRIPHASE CATALYTIC CONDITION.

Abstract

The present invention described an efficient method for catalytic oxidation of carbinols with hydrogen peroxide using Amberlite basic resin (IR-400) in presence of sodium tungstate as catalyst at an ambient condition in a suitable solvent. This method is high yielding, clean, safe, operationally simple and cost effective. Synthesis of carbonyl compounds in an environment friendly way is a very important fundamental reaction and has long been a challenge to the organic chemists. Although several oxidants have been reported in the last few years, in the present day scenario of the environmental protection, many of the existing methods have to be reviewed or replaced owing to the demerits reflected from such agents. Most of the carbonyls obtained like benzophenone, acetophenone vanillin, geranic acid, benzaldehyde, cyclohexanone etc are used in perfumery, beverage, food, nylon etc industries

Full Text	A VERSATILE PROCESS FOR THE OXIDATION OF CARBINOLS TO CARBONYLS TRIPHASE CATALYTIC CONDITION This invention relates to a novel process for oxidation of carbinols to carbonyls, a very important class of organic compounds used as precursors of various fine chemicals including drugs, vitamins, fragrances, perfumery, beverage and food industry apart from being a flavoring agent, solvents for resins, lacquers, dyes, nylon etc. This invention particularly relates to a novel method for oxidation of carbinols to carbonyls by triphase catalysis. The resin bound phase transfer catalyst (PTC) has been used for the oxidation of such compounds with hydrogen peroxide in the presence of sodium tungstate catalyst in a suitable solvent. Hydrogen peroxide is the best oxidant with respect to environmental and economic considerations. The hitherto known methods for preparation of important carbonyl compounds from their corresponding carbinols are 1. J. Dong; J Chem Res (s), 6,206, 1997 In this method, preparation of aldehyde and ketones has been reported to be done by the oxidation of primary and secondary alcohols of the formula 1 in which R1 represents alkyl or aryl group, R2 represents H, alkyl, aryl etc with K2Cr2O7 in a benzene water system. (Scheme Removed) SCHEME -1 The drawback of this method is that chromium reagents and benzene which are used, are highly toxic. 2. I. Prakash; S. K. Tanielyan; R. L. Augustine; L. Robert; K.E. Furlong; R.C. Scherm; H.E. Jackson; U. S. Patent 6,825,384 Prakash et al have carried out the oxidation of alcohols selectively to aldehydes with NaOCI using a TEMPO-borate catalyst system. It was shown that the oxidation could be efficiently carried out without KBr additives under solvent free conditions. Aldehydes such as 3, 3-dimethylbutyraldehyde can be produced efficiently by this method. (Scheme Removed) SCHEME - 2 The drawback of this method is that it is specific for certain type of molecules. 3 T.Mallat; A. Barker; Chem. Review 104 (6), 3037, 2004 In this method oxidation of secondary alcohol of the formula 1 in which R1 represents alkyl or aryl group, R2 represents H, alkyl, aryl etc has been reported to be carried out in water using molecular oxygen under the catalytic influence of detergent. (Scheme Removed) SCHEME - 3 The drawback is that the gas phase reaction is cumbersome to carry out. 4. S.Dorit; P. Kozner; L Asters; J. Amer. Chem. Soc.125, 5280-5281, 2003 Dorit et al have reported that polyoxometalate a "self assembled" water-soluble catalyst can very conveniently oxidize alcohols to carbonyls with hydrogen peroxide in water. (Scheme Removed) SCHEME-4 The catalyst has the advantage of recycling but the yield is very poor. 5. P. Alsters; V. Schmieden H. Elisabeth; U.S Patent, 6,593,494 In this method alcohol of the formula 1 in which R1 represents alkyl or aryl group, R2 represents H, alkyl, aryl etc was oxidized to the corresponding acid in the presence of periodate, catalytic amount of dichromate, an acid in water, and/or water/ organic solvent at a temperature range of -20 °C to +50 °C. (Scheme Removed) SCHEME - 5 Drawback of this method is that it is not environment friendly. 6 M. N. Sheng; U.S. Patent 3,997,578 In this method, a process for the preparation of fatty acids by the oxidation of alcohols, particularly, primary and /or secondary alcohols such as, octanol-1, cyclohexane-1, 2-diol of the formula 7 as shown in the Scheme 6 was described using a peracid as an oxidizing agent in the presence of a ruthenium catalyst and an organic solvent. This method has the disadvantage of using heavy metal and (Scheme Removed) SCHEME-6 uncontrolled oxidation of alcohols to acid. 7 J.H. Lee; S. J. Schmieg; U. S Patent 7,000,382 In this method it was described that the primary or secondary alcohol of the formula R1R2CHOH as shown in the Scheme 7 wherein R1 represents alkyl or aryl having 1-6 carbon atoms and R2 represents H, alkyl or aryl group were oxidized to the corresponding ketone or acid in the presence of solid Mo(VI) catalyst and oxygen gas. (Scheme Removed) SCHEME - 7 The disadvantage is that the gas phase reaction is cumbersome and substrate is restricted to 1-6 carbon atoms only. 8. T. K. Vinod; A.P. Thottumkara; U. S. Patent 6, 933,405 Thottumkara et. al. have reported a user and eco-friendly hyper-valent iodine reagent (IBX), that selectively oxidises allylic and benzylic alcohols of the formula 9 in which R represents allyl or benzyl group in water and / or other eco-friendly solvents to the corresponding aldehydes. (Scheme Removed) SCHEME - 8 However preparation of IBX is difficult. 9 M. Eckert; H.C. Militzer; M. Beller; C. Dobler;; G. Mehltretter; U. Sundermeier; U. S. Patent 6,790,997 This method relates to a process for the preparation of carbonyl compounds by the oxidation of alcohols of the formula 1 in which R1 represents alkyl or aryl group and R2 represents H, alkyl, aryl etc in the presence of osmium compounds as catalysts in water and / or solvent. (Scheme Removed) SCHEME - 9 However osmium is toxic to the environment. 10 A.R. Hajipour: N. Mahboobkhah; Ind J Chem, 37b (3), 285-287, 1998 Hajipour et al made use of 1-(phenyl methyl)-1-aza-4-azoniabicyclo [2,2,2] octane (PMAAO) periodate as an oxidizing agent to convert alcohol of the formula 1 in which R1 represents alkyl or aryl group and R2 represents H, alkyl, aryl etc to the corresponding carbonyl compound. (Scheme Removed) SCHEME-10 But the design of the oxidant is cumbersome. 11. P. Bragd; A. C. Besemer; U. S. Patent 6,936,710 In this method it is reported that primary hydroxyl groups in a substrate having both primary and secondary hydroxyl groups can be selectively oxidized to carbaldehyde and/or carboxyl groups by contacting the substrate with a cyclic nitroxyl compound in the presence of a peroxosulfate as a co-oxidant and by carrying out the reaction at a temperature below 30 °degree and at a pH below 9. (Scheme Removed) SCHEME-11 Catalyst represents cyclic nitroxyl compound. The process is suitable only for oxidizing polysaccharides. 12. P. Gogoi; D. Konwar; Org. Biomol.Chem.3, 3473-3475, 2005 Gogoi et al reported a new system I2-KI-K2CO3-H2O, which selectively oxidizes alcohols of the formula 1 in which R1 represents alkyl or aryl group and R2 represents H, alkyl, aryl etc to aldehydes and ketones under anaerobic conditions in water at 90°C. (Scheme Removed) SCHEME-12 This method has the drawback of maintaining the anaerobic condition Oxidation of carbinols to carbonyl compounds is a very important fundamental reaction. However, preparation of such important compounds in an environmentally friendly and cost effective way have still been a challenge to the organic chemists. It is therefore, desirable to have an efficient and versatile method to obtain such important class of compounds in one step, eliminating the drawbacks stated earlier. Objectives of the invention The major objective of the present invention is to provide a novel and efficient method for oxidation of carbinols to carbonyls. Another object of the invention is to provide an environment friendly method of preparation for oxidation of carbinols to carbonyls. More particularly the objective of the present invention is to provide a process for oxidation of primary and secondary alcohols of the formula R1R2CHOH as shown in the Scheme -13 at temperature range of 50-90°C in a suitable organic solvent such as dichloroethane or water using 50% hydrogen peroxide in the presence of sodium tungstate to produce the corresponding aldehydes, ketones, carboxylic acids and esters avoiding the drawbacks summarized above in the hitherto known processes. Another objective of the present invention is to provide a novel method for oxidation of carbinols of the formula R1R2CHOH as shown in the Scheme -13 in which R1, R2 represents alkyl, aralkyl, carbocyclic, aryl etc using 50% H2O2 and sodium tungstate in the presence of basic Amberlite resin (IR-400) at an ambient temperature. Yet another objective of the present invention is to provide an eco-friendly and cost effective method for oxidation of carbinols to carbonyls using H2O2 and sodium tungstate in the presence of Amberlite resin (IR-400) in water at an ambient temperature. Still another objective of the present invention is to provide an eco-friendly and cost effective method for oxidation of carbinols to carbonyls using H2O2 and sodium tungstate in the presence of Amberlite basic resin in an ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate at around 50 °C. The oxidation of carbinols using H2O2, sodium tungstate under triphase catalytic conditions at ambient temperature gives primarily ketones from the secondary alcohols. Primary aliphatic and aromatic alcohols give aldehydes and carboxylic acids accompanied by trace amount of esters. The solid supported triphase system can be very conveniently carried out at an ambient temperature to give the corresponding carbonyl compounds within 5-16 hrs with 60-95% yield. The result obtained is novel and non obvious. The basic Amberlite resin has found application in cation exchange reaction only. Summary of the invention The present invention provides a versatile method for oxidation of carbinols to carbonyls of the formula R1R2CHOH which comprises reacting carbinols with sodium tungstate, basic Amberlite resin and H2O2 in a suitable solvent at 50-90°C for 5-16 hrs to give the corresponding carbonyls, extracting the reaction mixture in an water immiscible organic solvents, drying and concentrating the organic extract, removing the organic solvent, purifying the product by silica gel chromatography to get pure products of the formula 2 as shown in the Scheme13. (Scheme Removed) SCHEME 13 Detailed description Accordingly, the present invention provides a process for preparation of carbonyl compounds of general formula 2 wherein R1 represents alkyl, aralkyl, carbocyclic, aryl; R'2 represents H, alkyl, aralkyl, carbocyclic, aryl, OH (Scheme Removed) which comprises reacting a carbinol of general formula 1 wherein R1 represents alkyl, aralkyl, carbocyclic, aryl; R2 represents H, alkyl, aralkyl, carbocyclic, aryl, with H2O2 in presence of sodium tungstate and basic Amberlite resin at pH ranging between 1 to 2 in a solvent selected from a group consisting of water, dichloromethane or ionic solvent such as 1-butyl-3-methyl imidazolium tetrafluoroborate at a temperature ranging between of 50-90°C for a period ranging between 5-16 hrs under stirring and followed by purification by conventional method. In an embodiment of the invention wherein the resin used is Amberlite basic resin (IR-400) in triphase catalysis. Other strongly basic resin having quaternary ammonium functionality such as Amberjet 4200, Amberlite IRA 410 in chloride or bromide form can also be used as triphase catalysis. In another embodiment of the present invention wherein, the oxidation is carried out preferably between 5-16 hrs. In yet another embodiment.of the invention wherein the Amberlite basic resin (IR-400) can be reused 4-5 times. In still another embodiment of the invention wherein the absence of of Amberlite (basic) IR-400 resin prolongs the reaction time. In a further embodiment of the invention wherein the reaction is carried out at pH ranging between 1 to 2. In another embodiment of the invention wherein olefinic alcohols were also oxidized efficiently without getting affected at the double bond functionality. In an embodiment of the invention wherein oxidation of primary alcohol gives a mixture of aldehyde, acid and trace amount of ester. In an embodiment of the invention wherein the reaction gives water as the only byproduct. In another embodiment of the invention wherein the molar ratio of substrate, H2O2, Na2WO4 is 10-20:40-60:1. In another embodiment of the invention wherein ionic solvent used is preferably 1-butyl-3-methylimidazolium tetrafluoroborate gives better results in terms of temperature (50 °C) and time (5 hrs) In another embodiment of the invention wherein the other ionic liquids that can be used as solvents are 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide etc. In another embodiment of the present invention oxidation of different primary or secondary alcohols of the formula R1R2CHOH can be affected by using 50% H2O2 in the presence of sodium tungstate under the triphase catalytic condition with strongly basic Amberlite IR 400 resin. In another embodiment of the present invention, it was observed that for the oxidation of carbinols, the solvent used is dichloromethane. In yet another embodiment of the present invention, it was observed that the oxidation of carbinols could be carried out using water as the only solvent. In still another embodiment of the present invention, the oxidation of carbinols could be carried out in ionic solvent (1-butyl-3-methylimidazolium tetrafluoroborate) which can be recovered. In still another embodiment of the present invention the oxidation of carbinols takes place at reflux temperature and absence of Amberlite basic resin affected with very poor yield of carbonyl compounds. The following specific examples are given by way of illustration of the invention in actual practice and therefore should not be construed to limit the scope of the present invention. Example 1 Oxidation of benzhydrol to benzophenone Diphenylmethanol (1.84g, 10mmol) was added to a stirred solution of sodium tungstate (0.329 g, 1mmol) cone. H2SO4 (pH 1.5) and resin (0.1g) in dichloroethane (15ml_) into a 25 ml three necked round bottomed flask equipped with a magnetic stirring bar and reflux condenser at 25 °C. The reaction mixture was stirred further for 30 minutes. The resultant was then heated to 80 °C with the slow and continuous addition of H2O2 (50%, 4.16 ml_, 60mmol) by dropping funnel. Small aliquots of the reaction mixture were taken out at different time intervals and monitored by gas chromatography and thin layer chromatography. At the end of the reaction after 8hrs, the reaction mixture was cooled to room temperature, and the two layers were separated. The organic phase was then washed with water (3X10 mL) at which time no residual peroxide was detected in the organic phase, dried over sodium sulphate and concentrated under reduced pressure. The residual crude reaction mixture was purified by silica-gel column chromatography to give the pure ketone (benzophenone) Yield: 95%. Example 2 Oxidation of 1-phenyl ethanol to acetophenone (water only) Same procedure was followed as described in example 1 but instead of dichloroethane water was taken. The reaction was complete in 16 hrs at a temperature of 90 °C Molar ratio of alcohol:H2O2:Na2WO4: 20:40:1 (16h),Yield : Acetophenone: 95% Example 3 Oxidation of pentanol to pentanoic acid Same procedure was followed as described in example 1 Molar ratio: Alcohol: H2O2: Na2WO4:20: 50: 1 (16 h) Yield: pentanoic acid: 85% pentanal: 15% Example 4 Oxidation of octanol to octanoic acid Same procedure was followed as described in example 1 Molar ratio: Alcohol: H2O2: Na2WO4:20: 50: 1 (16 h) Yield: octanoic acid: 75% octyl octanoate: ( Example 5 Oxidation of 2-methyl butanol to 2-methyl butanoic acid Same procedure was followed as described in example 1 Molar ratio: Alcohol: H2O2: Na2WO4: 20: 50: 1 (16 h) Yield: 2-methyl butanoic acid: 85% Example 6 Oxidation of vanillyl alcohol to vanillin Same procedure was followed as described in example 1 Molar ratio: Alcohol: H2O2: Na2WO4: 20: 50: 1: 1 (16 h) Yield: Vanillin: 70% Example 7 Oxidation of benzyl alcohol to benzaldehyde Same procedure was followed as described in example 1 Molar ratio: Alcohol: H2O2: Na2WO4: 20: 50: 1 (16 h) Yield: benzaldehyde: 75%, benzoic acid : 15% Example 8 Oxidation of 3-pentanol to 3-pentanone Same procedure was followed as described in example 1 Molar ratio: Alcohol: H2O2: Na2WO4: 20: 40: 1 (12 h) Yield: 3-pentanone: 90% Example 9 Oxidation of 2-methyl cyclohexanol to 2-methyl cyclohexanone Same procedure was followed as described in example 1 Molar ratio: Alcohol: H2O2: Na2WO4: 20: 40: 1 (12 h) Yield: 2-methyl cyclohexanone: 90%. Example 10 Oxidation of cyclohexanol to cyclohexanone Same procedure was followed as described in example 1 Molar ratio: Alcohol: H2O2: Na2WO4: 20: 40: 1 (12 h) Yield: cyclohexanone: 75% Example 11 Oxidation of 2, 6-dimethyl cyclohexanol to 2, 6-dimethyl cyclohexanone Same procedure was followed as described in example 1 Molar ratio: Alcohol: H2O2: Na2WO4: 20: 40: 1 (12 h) Yield: 2, 6-dimethyl cyclohexanone: 70% Example 12 Oxidation of cholesterol to cholest-5-ene-3-one Same procedure was followed as described in example 1 Molar ratio: Alcohol: H2O2: Na2WO4: 20: 60: 1 (16 h) Yield: Cholest-5-ene-3-one: 65% Example 13 Oxidation of p-sito sterol to 24- p-ethyl-5-cholesten-3-one Same procedure was followed as described in example 1 Molar ratio: Alcohol: H2O2: Na2WO4: 20: 60: 1 (16 h) Yield: 24- ß-ethyl-5-cholesten-3-one: 65% Example 14 Oxidation of 1-phenyl ethanol to acetophenone Same procedure was followed as described in example 1 Molar ratio: Alcohol: H202: Na2W04: 20: 40: 1 (12 h) Yield: acetophenone: 95% Example 15 Oxidation of geraniol to geranic acid Same procedure was followed as described in example 1 Molar ratio: Alcohol: H202: Na2W04: 20: 60: 1 (12 h) Yield: geranic acid: 60% Example 16 Oxidation of benzhydrol to benzophenone (ionic liquid) Same procedure was followed as described in example 1 but instead of dichloroethane ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate was taken. The reaction was complete in 5 hrs at a temperature of 50 °C. After the isolation of the product, ionic solvent was recovered. Molar ratio: Alcohol: H202: Na2W04: 20: 50: 1 (5 h). Yield : Benzophenone : 85% Example 17 Oxidation of octanol to octanoic acid (ionic liquid) Same procedure was followed as described in example 1 but instead of dichloroethane ionic liquid (1-butyl-3-methyl imidazolium tetrafluoroborate) was taken. The reaction was complete in 5 hrs at a temperature of 50 °C. After the isolation of the product, ionic solvent was recovered. Molar ratio: Alcohol: H202: Na2W04: 20: 50: 1 (5 h). Yield : Octanoic acid : 65%, Octyl octanoate : 15% Advantages of the present invention It is a one-pot reaction. The chemicals used are cheap and commercially available. The reaction takes place at mild conditions. The resin used can be reused. The method is eco-friendly. Hydrogen peroxide used is environment friendly with the by-product being only water. We claim 1 .A process for preparation of carbonyl compounds of general formula 2 wherein R'i represents alkyl, aralkyl, carbocyclic or aryl; R'2 represents H, alkyl, aralkyl, carbocyclic, aryl, OH (Formula Removed) which comprises reacting a carbinol compound of general formula 1 wherein R1 represents alkyl, aralkyl, carbocyclic, aryl; R2 represents H, alkyl, aralkyl, carbocyclic ,aryl with H2O2 in presence of sodium tungstate and basic Amberlite resin at pH ranging between 1 to 2 in a solvent selected from a group consisting of water, dichloroethane or an ionic liquid at a temperature ranging between 50-90°C for a period ranging between 5-16 hrs under stirring and followed by purification by conventional method to obtain the desired compound up to 90% yield. 2. A process as claimed in claim 1 wherein resin used is selected from a group consisting of Amberlite basic(IR-400), Amberjet 4200, and Amberlite IRA 410 resin in triphase catalysis. 3. A process as claimed in claim 1 wherein oxidation is carried out preferably between 8-16 hrs. 4. A process as claimed in claim 1 wherein the Amberlite resin (IR-400) can be reused 4-5 times. 5. A process as claimed in claim 1 wherein the absence of Amberlite (basic) resin (IR-400) or other strongly basic resin as stated above in claim 2 prolongs the reaction time. 6. A process as claimed in claim 1 wherein the reaction is carried out at pH ranging between 1-2. 7. A process as claimed in claim 1 wherein olefinic alcohols were also oxidized efficiently without getting affected at the double bond functionality. 8. A process as claimed in claim 1 wherein the oxidation of primary alcohol gives a mixture of aldehyde, acid and trace amount of ester. 9. A process as claimed in claim 1 wherein the reaction gives water as the only by-product. 10. A process as claimed in claim 1 wherein the molar ratio of substrate, H2O2, Na2WO4 is 10-20:40-60:1 respectively. 11. A process as claimed in claim 1 wherein ionic liquid used is selected from a group consisting of 1-butyl-3-methyl imidazolium tetrafluoroborate, 1-butyl-3- methyl imidazolium chloride, 1-butyl-3-methyl imidazolium bromide, preferably 1- butyl-3-methyl imidazolium tetrafluoroborate. 12.A process for preparation of carbonyl compounds of general formula 2 as claimed in claim 1 substantially as herein described with reference to the examples

Full Text

A VERSATILE PROCESS FOR THE OXIDATION OF CARBINOLS TO CARBONYLS TRIPHASE CATALYTIC CONDITION
This invention relates to a novel process for oxidation of carbinols to carbonyls, a very important class of organic compounds used as precursors of various fine chemicals including drugs, vitamins, fragrances, perfumery, beverage and food industry apart from being a flavoring agent, solvents for resins, lacquers, dyes, nylon etc. This invention particularly relates to a novel method for oxidation of carbinols to carbonyls by triphase catalysis. The resin bound phase transfer catalyst (PTC) has been used for the oxidation of such compounds with hydrogen peroxide in the presence of sodium tungstate catalyst in a suitable solvent. Hydrogen peroxide is the best oxidant with respect to environmental and economic considerations.
The hitherto known methods for preparation of important carbonyl compounds from their corresponding carbinols are
1. J. Dong; J Chem Res (s), 6,206, 1997
In this method, preparation of aldehyde and ketones has been reported to be done by the oxidation of primary and secondary alcohols of the formula 1 in which R1 represents alkyl or aryl group, R2 represents H, alkyl, aryl etc with K2Cr2O7 in a benzene water system.
(Scheme Removed)
SCHEME -1
The drawback of this method is that chromium reagents and benzene which are used, are highly toxic.
2. I. Prakash; S. K. Tanielyan; R. L. Augustine; L. Robert; K.E. Furlong; R.C.
Scherm; H.E. Jackson; U. S. Patent 6,825,384
Prakash et al have carried out the oxidation of alcohols selectively to aldehydes with NaOCI using a TEMPO-borate catalyst system. It was shown that the oxidation could be efficiently carried out without KBr additives under solvent free
conditions. Aldehydes such as 3, 3-dimethylbutyraldehyde can be produced efficiently by this method.
(Scheme Removed)
SCHEME - 2
The drawback of this method is that it is specific for certain type of molecules. 3 T.Mallat; A. Barker; Chem. Review 104 (6), 3037, 2004 In this method oxidation of secondary alcohol of the formula 1 in which R1 represents alkyl or aryl group, R2 represents H, alkyl, aryl etc has been reported to be carried out in water using molecular oxygen under the catalytic influence of detergent.
(Scheme Removed)
SCHEME - 3
The drawback is that the gas phase reaction is cumbersome to carry out.
4. S.Dorit; P. Kozner; L Asters; J. Amer. Chem. Soc.125, 5280-5281, 2003
Dorit et al have reported that polyoxometalate a "self assembled" water-soluble
catalyst can very conveniently oxidize alcohols to carbonyls with hydrogen peroxide in water.
(Scheme Removed)
SCHEME-4
The catalyst has the advantage of recycling but the yield is very poor.
5. P. Alsters; V. Schmieden H. Elisabeth; U.S Patent, 6,593,494
In this method alcohol of the formula 1 in which R1 represents alkyl or aryl group, R2 represents H, alkyl, aryl etc was oxidized to the corresponding acid in the
presence of periodate, catalytic amount of dichromate, an acid in water, and/or water/ organic solvent at a temperature range of -20 °C to +50 °C.
(Scheme Removed)
SCHEME - 5
Drawback of this method is that it is not environment friendly.
6 M. N. Sheng; U.S. Patent 3,997,578
In this method, a process for the preparation of fatty acids by the oxidation of alcohols, particularly, primary and /or secondary alcohols such as, octanol-1, cyclohexane-1, 2-diol of the formula 7 as shown in the Scheme 6 was described using a peracid as an oxidizing agent in the presence of a ruthenium catalyst and an organic solvent. This method has the disadvantage of using heavy metal and
(Scheme Removed)
SCHEME-6
uncontrolled oxidation of alcohols to acid.
7 J.H. Lee; S. J. Schmieg; U. S Patent 7,000,382
In this method it was described that the primary or secondary alcohol of the formula R1R2CHOH as shown in the Scheme 7 wherein R1 represents alkyl or aryl having 1-6 carbon atoms and R2 represents H, alkyl or aryl group were oxidized to the corresponding ketone or acid in the presence of solid Mo(VI) catalyst and oxygen gas.
(Scheme Removed)
SCHEME - 7
The disadvantage is that the gas phase reaction is cumbersome and substrate is restricted to 1-6 carbon atoms only.
8. T. K. Vinod; A.P. Thottumkara; U. S. Patent 6, 933,405 Thottumkara et. al. have reported a user and eco-friendly hyper-valent iodine reagent (IBX), that selectively oxidises allylic and benzylic alcohols of the formula 9 in which R represents allyl or benzyl group in water and / or other eco-friendly solvents to the corresponding aldehydes.
(Scheme Removed)
SCHEME - 8
However preparation of IBX is difficult.
9 M. Eckert; H.C. Militzer; M. Beller; C. Dobler;; G. Mehltretter; U. Sundermeier;
U. S. Patent 6,790,997
This method relates to a process for the preparation of carbonyl compounds by the oxidation of alcohols of the formula 1 in which R1 represents alkyl or aryl group and R2 represents H, alkyl, aryl etc in the presence of osmium compounds as catalysts in water and / or solvent.
(Scheme Removed)
SCHEME - 9
However osmium is toxic to the environment.
10 A.R. Hajipour: N. Mahboobkhah; Ind J Chem, 37b (3), 285-287, 1998
Hajipour et al made use of 1-(phenyl methyl)-1-aza-4-azoniabicyclo [2,2,2]
octane (PMAAO) periodate as an oxidizing agent to convert alcohol of the formula 1 in which R1 represents alkyl or aryl group and R2 represents H, alkyl, aryl etc to the corresponding carbonyl compound.
(Scheme Removed)
SCHEME-10
But the design of the oxidant is cumbersome.
11. P. Bragd; A. C. Besemer; U. S. Patent 6,936,710
In this method it is reported that primary hydroxyl groups in a substrate having both primary and secondary hydroxyl groups can be selectively oxidized to carbaldehyde and/or carboxyl groups by contacting the substrate with a cyclic nitroxyl compound in the presence of a peroxosulfate as a co-oxidant and by carrying out the reaction at a temperature below 30 °degree and at a pH below 9.
(Scheme Removed)
SCHEME-11
Catalyst represents cyclic nitroxyl compound. The process is suitable only for oxidizing polysaccharides.
12. P. Gogoi; D. Konwar; Org. Biomol.Chem.3, 3473-3475, 2005
Gogoi et al reported a new system I2-KI-K2CO3-H2O, which selectively oxidizes alcohols of the formula 1 in which R1 represents alkyl or aryl group and R2 represents H, alkyl, aryl etc to aldehydes and ketones under anaerobic conditions in water at 90°C.
(Scheme Removed)
SCHEME-12
This method has the drawback of maintaining the anaerobic condition Oxidation of carbinols to carbonyl compounds is a very important fundamental reaction. However, preparation of such important compounds in an environmentally friendly and cost effective way have still been a challenge to the organic chemists. It is therefore, desirable to have an efficient and versatile method to
obtain such important class of compounds in one step, eliminating the drawbacks stated earlier.
Objectives of the invention
The major objective of the present invention is to provide a novel and efficient method for oxidation of carbinols to carbonyls.
Another object of the invention is to provide an environment friendly method of preparation for oxidation of carbinols to carbonyls.
More particularly the objective of the present invention is to provide a process for oxidation of primary and secondary alcohols of the formula R1R2CHOH as shown in the Scheme -13 at temperature range of 50-90°C in a suitable organic solvent such as dichloroethane or water using 50% hydrogen peroxide in the presence of sodium tungstate to produce the corresponding aldehydes, ketones, carboxylic acids and esters avoiding the drawbacks summarized above in the hitherto known processes.
Another objective of the present invention is to provide a novel method for oxidation of carbinols of the formula R1R2CHOH as shown in the Scheme -13 in which R1, R2 represents alkyl, aralkyl, carbocyclic, aryl etc using 50% H2O2 and sodium tungstate in the presence of basic Amberlite resin (IR-400) at an ambient temperature.
Yet another objective of the present invention is to provide an eco-friendly and cost effective method for oxidation of carbinols to carbonyls using H2O2 and sodium tungstate in the presence of Amberlite resin (IR-400) in water at an ambient temperature.
Still another objective of the present invention is to provide an eco-friendly and cost effective method for oxidation of carbinols to carbonyls using H2O2 and sodium tungstate in the presence of Amberlite basic resin in an ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate at around 50 °C. The oxidation of carbinols using H2O2, sodium tungstate under triphase catalytic conditions at ambient temperature gives primarily ketones from the secondary alcohols. Primary aliphatic and aromatic alcohols give aldehydes and carboxylic acids accompanied by trace amount of esters. The solid supported triphase
system can be very conveniently carried out at an ambient temperature to give the corresponding carbonyl compounds within 5-16 hrs with 60-95% yield. The result obtained is novel and non obvious. The basic Amberlite resin has found application in cation exchange reaction only. Summary of the invention
The present invention provides a versatile method for oxidation of carbinols to carbonyls of the formula R1R2CHOH which comprises reacting carbinols with sodium tungstate, basic Amberlite resin and H2O2 in a suitable solvent at 50-90°C for 5-16 hrs to give the corresponding carbonyls, extracting the reaction mixture in an water immiscible organic solvents, drying and concentrating the organic extract, removing the organic solvent, purifying the product by silica gel chromatography to get pure products of the formula 2 as shown in the Scheme13.
(Scheme Removed)
SCHEME 13 Detailed description
Accordingly, the present invention provides a process for preparation of carbonyl compounds of general formula 2 wherein R1 represents alkyl, aralkyl, carbocyclic, aryl; R'2 represents H, alkyl, aralkyl, carbocyclic, aryl, OH
(Scheme Removed)
which comprises reacting a carbinol of general formula 1 wherein R1 represents alkyl, aralkyl, carbocyclic, aryl; R2 represents H, alkyl, aralkyl, carbocyclic, aryl, with H2O2 in presence of sodium tungstate and basic Amberlite resin at pH ranging between 1 to 2 in a solvent selected from a group consisting of water, dichloromethane or ionic solvent such as 1-butyl-3-methyl imidazolium tetrafluoroborate at a temperature ranging between of 50-90°C for a period
ranging between 5-16 hrs under stirring and followed by purification by conventional method.
In an embodiment of the invention wherein the resin used is Amberlite basic resin (IR-400) in triphase catalysis. Other strongly basic resin having quaternary ammonium functionality such as Amberjet 4200, Amberlite IRA 410 in chloride or bromide form can also be used as triphase catalysis.
In another embodiment of the present invention wherein, the oxidation is carried out preferably between 5-16 hrs.
In yet another embodiment.of the invention wherein the Amberlite basic resin (IR-400) can be reused 4-5 times.
In still another embodiment of the invention wherein the absence of of Amberlite (basic) IR-400 resin prolongs the reaction time.
In a further embodiment of the invention wherein the reaction is carried out at pH ranging between 1 to 2.
In another embodiment of the invention wherein olefinic alcohols were also oxidized efficiently without getting affected at the double bond functionality. In an embodiment of the invention wherein oxidation of primary alcohol gives a mixture of aldehyde, acid and trace amount of ester.
In an embodiment of the invention wherein the reaction gives water as the only byproduct.
In another embodiment of the invention wherein the molar ratio of substrate, H2O2, Na2WO4 is 10-20:40-60:1.
In another embodiment of the invention wherein ionic solvent used is preferably 1-butyl-3-methylimidazolium tetrafluoroborate gives better results in terms of temperature (50 °C) and time (5 hrs)
In another embodiment of the invention wherein the other ionic liquids that can be used as solvents are 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide etc.
In another embodiment of the present invention oxidation of different primary or secondary alcohols of the formula R1R2CHOH can be affected by using 50%
H2O2 in the presence of sodium tungstate under the triphase catalytic condition
with strongly basic Amberlite IR 400 resin.
In another embodiment of the present invention, it was observed that for the
oxidation of carbinols, the solvent used is dichloromethane.
In yet another embodiment of the present invention, it was observed that the
oxidation of carbinols could be carried out using water as the only solvent.
In still another embodiment of the present invention, the oxidation of carbinols
could be carried out in ionic solvent (1-butyl-3-methylimidazolium
tetrafluoroborate) which can be recovered.
In still another embodiment of the present invention the oxidation of carbinols
takes place at reflux temperature and absence of Amberlite basic resin affected
with very poor yield of carbonyl compounds.
The following specific examples are given by way of illustration of the invention in
actual practice and therefore should not be construed to limit the scope of the
present invention.
Example 1
Oxidation of benzhydrol to benzophenone
Diphenylmethanol (1.84g, 10mmol) was added to a stirred solution of sodium
tungstate (0.329 g, 1mmol) cone. H2SO4 (pH 1.5) and resin (0.1g) in
dichloroethane (15ml_) into a 25 ml three necked round bottomed flask equipped
with a magnetic stirring bar and reflux condenser at 25 °C. The reaction mixture
was stirred further for 30 minutes. The resultant was then heated to 80 °C with
the slow and continuous addition of H2O2 (50%, 4.16 ml_, 60mmol) by dropping
funnel. Small aliquots of the reaction mixture were taken out at different time
intervals and monitored by gas chromatography and thin layer chromatography.
At the end of the reaction after 8hrs, the reaction mixture was cooled to room
temperature, and the two layers were separated. The organic phase was then
washed with water (3X10 mL) at which time no residual peroxide was detected
in the organic phase, dried over sodium sulphate and concentrated under
reduced pressure. The residual crude reaction mixture was purified by silica-gel
column chromatography to give the pure ketone (benzophenone) Yield: 95%.
Example 2
Oxidation of 1-phenyl ethanol to acetophenone (water only)
Same procedure was followed as described in example 1 but instead of
dichloroethane water was taken. The reaction was complete in 16 hrs at a
temperature of 90 °C
Molar ratio of alcohol:H2O2:Na2WO4: 20:40:1 (16h),Yield : Acetophenone: 95%
Example 3
Oxidation of pentanol to pentanoic acid
Same procedure was followed as described in example 1
Molar ratio: Alcohol: H2O2: Na2WO4:20: 50: 1 (16 h)
Yield: pentanoic acid: 85% pentanal: 15%
Example 4
Oxidation of octanol to octanoic acid
Same procedure was followed as described in example 1
Molar ratio: Alcohol: H2O2: Na2WO4:20: 50: 1 (16 h)
Yield: octanoic acid: 75% octyl octanoate: ( Example 5
Oxidation of 2-methyl butanol to 2-methyl butanoic acid
Same procedure was followed as described in example 1
Molar ratio: Alcohol: H2O2: Na2WO4: 20: 50: 1 (16 h)
Yield: 2-methyl butanoic acid: 85%
Example 6
Oxidation of vanillyl alcohol to vanillin
Same procedure was followed as described in example 1
Molar ratio: Alcohol: H2O2: Na2WO4: 20: 50: 1: 1 (16 h)
Yield: Vanillin: 70%
Example 7
Oxidation of benzyl alcohol to benzaldehyde
Same procedure was followed as described in example 1
Molar ratio: Alcohol: H2O2: Na2WO4: 20: 50: 1 (16 h)
Yield: benzaldehyde: 75%, benzoic acid : 15%
Example 8
Oxidation of 3-pentanol to 3-pentanone
Same procedure was followed as described in example 1
Molar ratio: Alcohol: H2O2: Na2WO4: 20: 40: 1 (12 h)
Yield: 3-pentanone: 90%
Example 9
Oxidation of 2-methyl cyclohexanol to 2-methyl cyclohexanone
Same procedure was followed as described in example 1
Molar ratio: Alcohol: H2O2: Na2WO4: 20: 40: 1 (12 h)
Yield: 2-methyl cyclohexanone: 90%.
Example 10
Oxidation of cyclohexanol to cyclohexanone
Same procedure was followed as described in example 1
Molar ratio: Alcohol: H2O2: Na2WO4: 20: 40: 1 (12 h)
Yield: cyclohexanone: 75%
Example 11
Oxidation of 2, 6-dimethyl cyclohexanol to 2, 6-dimethyl cyclohexanone
Same procedure was followed as described in example 1
Molar ratio: Alcohol: H2O2: Na2WO4: 20: 40: 1 (12 h)
Yield: 2, 6-dimethyl cyclohexanone: 70%
Example 12
Oxidation of cholesterol to cholest-5-ene-3-one
Same procedure was followed as described in example 1
Molar ratio: Alcohol: H2O2: Na2WO4: 20: 60: 1 (16 h)
Yield: Cholest-5-ene-3-one: 65%
Example 13
Oxidation of p-sito sterol to 24- p-ethyl-5-cholesten-3-one
Same procedure was followed as described in example 1
Molar ratio: Alcohol: H2O2: Na2WO4: 20: 60: 1 (16 h)
Yield: 24- ß-ethyl-5-cholesten-3-one: 65%
Example 14
Oxidation of 1-phenyl ethanol to acetophenone
Same procedure was followed as described in example 1
Molar ratio: Alcohol: H202: Na2W04: 20: 40: 1 (12 h)
Yield: acetophenone: 95%
Example 15
Oxidation of geraniol to geranic acid
Same procedure was followed as described in example 1
Molar ratio: Alcohol: H202: Na2W04: 20: 60: 1 (12 h)
Yield: geranic acid: 60%
Example 16
Oxidation of benzhydrol to benzophenone (ionic liquid)
Same procedure was followed as described in example 1 but instead of
dichloroethane ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate was
taken. The reaction was complete in 5 hrs at a temperature of 50 °C. After the
isolation of the product, ionic solvent was recovered.
Molar ratio: Alcohol: H202: Na2W04: 20: 50: 1 (5 h).
Yield : Benzophenone : 85%
Example 17
Oxidation of octanol to octanoic acid (ionic liquid)
Same procedure was followed as described in example 1 but instead of
dichloroethane ionic liquid (1-butyl-3-methyl imidazolium tetrafluoroborate) was
taken. The reaction was complete in 5 hrs at a temperature of 50 °C. After the
isolation of the product, ionic solvent was recovered.
Molar ratio: Alcohol: H202: Na2W04: 20: 50: 1 (5 h).
Yield : Octanoic acid : 65%, Octyl octanoate : 15%
Advantages of the present invention
It is a one-pot reaction.
The chemicals used are cheap and commercially available.
The reaction takes place at mild conditions.
The resin used can be reused.
The method is eco-friendly.
Hydrogen peroxide used is environment friendly with the by-product being only
water.

We claim
1 .A process for preparation of carbonyl compounds of general formula 2 wherein R'i represents alkyl, aralkyl, carbocyclic or aryl; R'2 represents H, alkyl, aralkyl, carbocyclic, aryl, OH
(Formula Removed)
which comprises reacting a carbinol compound of general formula 1 wherein R1 represents alkyl, aralkyl, carbocyclic, aryl; R2 represents H, alkyl, aralkyl, carbocyclic ,aryl with H2O2 in presence of sodium tungstate and basic Amberlite resin at pH ranging between 1 to 2 in a solvent selected from a group consisting of water, dichloroethane or an ionic liquid at a temperature ranging between 50-90°C for a period ranging between 5-16 hrs under stirring and followed by purification by conventional method to obtain the desired compound up to 90% yield.
2. A process as claimed in claim 1 wherein resin used is selected from a group consisting of Amberlite basic(IR-400), Amberjet 4200, and Amberlite IRA 410 resin in triphase catalysis.
3. A process as claimed in claim 1 wherein oxidation is carried out preferably between 8-16 hrs.
4. A process as claimed in claim 1 wherein the Amberlite resin (IR-400) can be reused 4-5 times.
5. A process as claimed in claim 1 wherein the absence of Amberlite (basic) resin (IR-400) or other strongly basic resin as stated above in claim 2 prolongs the reaction time.
6. A process as claimed in claim 1 wherein the reaction is carried out at pH ranging between 1-2.
7. A process as claimed in claim 1 wherein olefinic alcohols were also oxidized efficiently without getting affected at the double bond functionality.
8. A process as claimed in claim 1 wherein the oxidation of primary alcohol gives a mixture of aldehyde, acid and trace amount of ester.
9. A process as claimed in claim 1 wherein the reaction gives water as the only by-product.
10. A process as claimed in claim 1 wherein the molar ratio of substrate, H2O2,
Na2WO4 is 10-20:40-60:1 respectively.
11. A process as claimed in claim 1 wherein ionic liquid used is selected from a
group consisting of 1-butyl-3-methyl imidazolium tetrafluoroborate, 1-butyl-3-
methyl imidazolium chloride, 1-butyl-3-methyl imidazolium bromide, preferably 1-
butyl-3-methyl imidazolium tetrafluoroborate.
12.A process for preparation of carbonyl compounds of general formula 2 as claimed in claim 1 substantially as herein described with reference to the examples

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Patent Number

270403

Indian Patent Application Number

645/DEL/2007

PG Journal Number

52/2015

Publication Date

25-Dec-2015

Grant Date

18-Dec-2015

Date of Filing

23-Mar-2007

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

ANUSANDHAN BHAWAN, RAFI MARG, NEW DELHI-110 001,INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	DR.AMRIT GOSWAMI	REGIONAL RESEARCH LABORATORY JORHAT-785006
2	DR.(MS) NISHI BHATI	REGIONAL RESEARCH LABORATORY JORHAT-785006
3	MR KULADEEP SARMAH	REGIONAL RESEARCH LABORATORY JORHAT-785006

PCT International Classification Number

C07C

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA