METAL CATALYST AND HYDROGEN GAS FREE APPROACHES FOR SELECTIVE REDUCTION OF ALDEHYDE TO METHYL GROUP OF DIFFERENT SUBSTITUTED FURANS

Abstract

The present invention relates to 5-methyl substituted furan compounds of general formula (I) and process for the preparation thereof: ORlR2 R3CH3(1) Particularly, the present invention relates to a metal catalyst and hydrogen gas free, atom-economy, highly selective and low-cost process for the preparation of methyl substituted furan compounds from different aldehyde substituted furan compounds.

Claims

1-13. (canceled)

14. A process for the preparation of a 5-methyl substituted furan of general formula (I): ##STR00024## where: R.sup.1 is selected from the group consisting of hydrogen, hydroxymethyl, alkyl, hydroxy, aldehyde, halide, ester, carboxyl, nitro, amino, amide, substituted amino, alkoxy/ether linkages, sulfur derivatives, phosphorous derivatives, aryl, and heteroaryl; and R.sup.2 and R.sup.3 are selected from the group consisting of hydrogen, alkyl, and aryl, the process comprising: (i) reacting an amine compound and an inorganic base with a substituted furfural in an alcoholic organic solvent selected from alkyl alcohols or cyclic alkyl alcohols at a reaction temperature from 120° C. to 140° C. for a reaction time period from 2 hours to 6 hours to obtain an in situ generated corresponding imine compound, the substituted furfural having formula (II): ##STR00025## where R.sup.1, R.sup.2, and R.sup.3 of formula (II) are as defined in general formula (I); (ii) reducing the in situ generated corresponding imine compound of (i) under basic conditions in the alcoholic organic solvent to obtain a 5-methyl substituted furan of general formula (I); (iii) isolating the 5-methyl substituted furan; and (iv) optionally, purifying the isolated 5-methyl substituted furan.

15. The process according to claim 14, wherein the amine compound is selected from the group consisting of hydrazine hydrate, hydrazine hydrochloride, aryl substituted hydrazine, alkyl substituted hydrazine, hydroxyl substituted hydrazine, and mixtures thereof.

16. The process according to claim 14, wherein the inorganic base is chosen from alkali metal alkoxides, alkali metal hydroxides, or alkali metal hydrides.

17. The process according to claim 14, wherein the inorganic base is selected from the group consisting of KO.sup.tBu, NaO.sup.tBu, KOEt, NaOEt, KOMe, NaOMe, NaOH, KOH, NaH, and mixtures thereof.

18. The process according to claim 14, wherein the alcoholic organic solvent has under the basic conditions a proton transfer capability sufficient to reduce the in situ corresponding imine compound.

19. The process according to claim 14, wherein the alcoholic organic solvent is selected from the group consisting of methanol, ethanol, isopropanol, n-butanol, 2-butanol, t-butanol, and mixtures thereof.

20. The process according to claim 14, wherein (iii) comprises extracting the 5-methyl substituted furan with a solvent selected from the group consisting of alkyl ketones, ethyl acetate, dichloromethane, chloroform, tetrahydrofuran, diethyl ether, and mixtures thereof.

21. The process according to claim 14, wherein (i) comprises reacting from 1 to 3 molar equivalents of the amine compound and from 0.5 to 4 molar equivalents of the inorganic base with 1 molar equivalent of the substituted furfural of formula (II).

22. The process according to claim 14, wherein: the substituted furfural of formula (II) is 5-hydroxymethylfurfural of formula (IIIa): ##STR00026## ; and the 5-methyl substituted furan of general formula (I) is 5-methyl furfuryl alcohol of formula (III): ##STR00027## .

23. The process according to claim 22, wherein the amine compound is selected from the group consisting of hydrazine hydrate, hydrazine hydrochloride, aryl substituted hydrazine, alkyl substituted hydrazine, hydroxyl substituted hydrazine, and mixtures thereof.

24. The process according to claim 22, wherein the inorganic base is selected from the group consisting of KO.sup.tBu, NaO.sup.tBu, KOEt, NaOEt, KOMe, NaOMe, NaOH, KOH, NaH, and mixtures thereof.

25. The process according to claim 22, wherein the alcoholic organic solvent is selected from the group consisting of methanol, ethanol, isopropanol, n-butanol, 2-butanol, t-butanol, and mixtures thereof.

26. The process according to claim 22, wherein (iii) comprises extracting the 5-methyl substituted furan with a solvent selected from the group consisting of alkyl ketones, ethyl acetate, dichloromethane, chloroform, tetrahydrofuran, diethyl ether, and mixtures thereof.

27. The process according to claim 22, wherein (i) comprises reacting from 1 to 3 molar equivalents of the amine compound and 0.5 to 2 molar equivalents of the inorganic base with 1 molar equivalent of the 5-hydroxymethylfurfural.

28. The process according to claim 22, further comprising reacting the 5-methyl furfuryl alcohol in the presence of aluminum trichloride and ethanol to obtain 2-(ethoxymethyl)-5-methylfuran of formula (V): ##STR00028## .

29. The process according to claim 14, wherein: the substituted furfural of formula (II) is 2,5-diformylfuran of formula (IVa): ##STR00029## the reaction temperature is 130° C.; the reaction time period is from 3 hours to 5 hours; the in situ generated corresponding imine compound is a diimine; and the 5-methyl substituted furan of general formula (I) is 2,5-dimethylfuran of formula (IV): ##STR00030## .

30. The process according to claim 29, wherein the amine compound is selected from the group consisting of hydrazine hydrate, hydrazine hydrochloride, aryl substituted hydrazine, alkyl substituted hydrazine, hydroxyl substituted hydrazine, and mixtures thereof.

31. The process according to claim 29, wherein the inorganic base is selected from the group consisting of KO.sup.tBu, NaO.sup.tBu, KOEt, NaOEt, KOMe, NaOMe, NaOH, KOH, NaH, and mixtures thereof.

32. The process according to claim 29, wherein the alcoholic organic solvent is selected from the group consisting of methanol, ethanol, isopropanol, n-butanol, 2-butanol, t-butanol, and mixtures thereof.

33. The process according to claim 29, wherein (i) comprises reacting 2 molar equivalents of the amine compound and 0.5 molar equivalents of the inorganic base with 1 molar equivalent of the 2,5-diformylfuran.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0041] Present invention provides “Metal free approaches for selective reduction of aldehyde to methyl group of different substituted furans” which comprises in situ steps following hydrazone of carbonyl compound and further decomposition in presence of strong base to give 5-methyl substituted furan compounds of general formula (I):

##STR00008##

wherein; R.sup.1 is selected from the group comprising: hydrogen, hydroxymethyl, methyl, alkyl, hydroxy, formyl, halide, ester, carboxyl, nitro, amide, amino, substituted amino, alkoxy, ether, sulphur derivatives, phosphorous derivatives, and aryl and hetero aryl functionality; and R.sup.2 and R.sup.3 may be selected from the group comprising: hydrogen, alkyl, and aryl.

[0042] In contrast to the prior art processes, the present invention provides a method for metal and hydrogen gas free reduction method for direct conversion of 5-HMF and di/monoformyl furan to corresponding 5-MFA and DMF, with good yields.

[0043] The problematic and yet not been attempted Wolff-Kishner reduction approach has been performed under this study at comparably low temperature for selective conversion of 5-aldehyde substituted furan compounds to 5-methyl substituted furan compound of general formula (I) in good yield with negligible by-product formation.

[0044] Further, the process was performed under normal reflux condition without the need of high pressure autoclave system.

[0045] The modified synthetic approach was found to be highly selective, high yielding and applicable for large-scale production of 5-MFA with very good yield.

[0046] The whole modified system also restricts unwanted byproduct formation, over reduction and polymerization.

[0047] In an embodiment, the present invention provides a process for the preparation of 5-methyl substituted furans of general formula (I):

##STR00009##

wherein; [0048] R.sup.1 is selected from the group comprising: hydrogen, hydroxymethyl, methyl, alkyl, hydroxy, aldehyde, halide, ester, carboxylic acid, amide, amine, substituted amine, alkoxy/ether linkages, sulphur derivatives, phosphorous derivatives, and aryl and hetero aryl functionality; R.sup.2 and R.sup.3 may be selected from the group comprising: hydrogen, alkyl, and aryl; the process comprising the steps of: [0049] i) reacting an amine compound and an inorganic base with a substituted furfural of formula (II) in a solvent to obtain an in situ corresponding imine compound; [0050] ii) reducing the in situ generated imine of step (i) under basic condition in a solvent to obtain the 5-methyl substituted furans of general formula (I); [0051] iii) isolating methyl substituted furans of general formula (I); and [0052] iv) optionally, purifying isolated methyl substituted furans of general formula (I).

[0053] In another embodiment, the alkyl is methyl.

[0054] In another embodiment, the present invention provides a cost-effective, atom-economic, highly-selective and high yielding approach for the preparation of 5-methyl substituted furan compounds of general formula (I) from low cost carbohydrates (such as sugarcane bagasse, rice straw, corn cob, other cellulosic resources, cellulose, starch, polysaccharide, glucose and fructose) through 5-HMF and its corresponding products and minimization of by-product formation to avoid costly purification process.

[0055] In another embodiment, the present invention provides one pot process for the preparation of 5-methyl substituted furans of general formula (I)

[0056] In another embodiment, the present invention provides a metal and hydrogen gas free, highly selective and cost-effective process for the preparation of 5-methyl substituted furans of general formula (I).

[0057] In another embodiment, the present invention provides a process for the preparation of 5-methyl furfuryl alcohol (5-MFA) of formula (1),

##STR00011##

comprising: [0058] i) reacting an amine compound and an inorganic base with 5-hydroxymethylfurfural (HMF) in a suitable solvent to produce in situ corresponding imine; [0059] ii) reducing in situ generated imine of step (i) under basic condition in a suitable solvent to 5-MFA of formula (1); [0060] iii) isolating 5-MFA of formula (III); and [0061] iv) optionally, purifying isolated 5-MFA of formula (III).

[0062] 5-HMF has been used as a main building block, produced from carbohydrates for the construction of 5-MFA.

[0063] Alcoholic group of 5-HMF was not found to be reactive and ended with major 5-MFA product and 2,5-diformylfuran or monoformylfuran, both get converted successfully under this process to DMF as major product.

[0064] In another embodiment, the final product of formula (I) or formula (III) or formula (IV) are isolated by method of extraction employing suitable extracting solvent.

[0065] The suitable extracting solvent include but are not limited to alkyl ketones, ethyl acetate, dichloromethane, chloroform, THF and diethyl ether, or the like, and mixture thereof.

[0066] To achieve high yield and purity of final product of formula (I) or formula (III) or formula (IV) the distillation is performed at variable pressure and temperature condition.

[0067] The present process follows the traditional Wolff-Kishner reduction approach which was not yet been explored for aldehyde substituted furan compounds of general formula (II).

[0068] The amine compound includes but are not limited to hydrazine hydrate, hydrazine hydrochloride, aryl substituted hydrazine/alkyl substituted hydrazine/hydroxyl substituted hydrazine and further extended any such group of diamine compounds having the tendency of imine formation and follow the similar Wolff-Kishner reduction approach, or the like. Preferably, the inorganic base is a strong inorganic base.

[0069] The inorganic base includes, but are not limited to inorganic bases of alkoxy alkali metals, hydroxyl alkali metals and hydride alkali metals. Most preferably, the alkali metals are K, Na and Cs. The alkoxy alkali metals are selected from the group consisting of KO.sup.tBu, NaO.sup.tBu, KOEt, NaOEt, KOMe and NaOMe. The hydroxyl alkali metals are selected from the group consisting of NaOH and KOH; and the hydride alkali metal is NaH.

[0070] Most preferably, the inorganic base is selected from the group consisting of KO.sup.tBu, NaO.sup.tBu, KOEt, NaOEt, KOMe, NaOMe, NaOH, KOH and NaH.

[0071] Preferably, the suitable solvent is an alcoholic organic solvent.

[0072] The alcoholic organic solvent is any protonic alcohol with variable boiling points and having proton transfer capability with strong basic condition to reduce the in situ imine formed from carbonyls to alkyl carbon.

[0073] The alcoholic organic solvent includes, but are not limited to, alkyl alcohol, cyclic alkyl alcohols or the like.

[0074] Preferably, the alkyl or cyclic alkyl alcoholic solvent is selected from the group consisting of methanol, ethanol, iso-propanol, n-butanol, 2-butanol, t-butanol or mixture thereof. Most preferably, the alcoholic solvent is 2-butanol and ethanol.

[0075] The isolation step iii) of above processes is done by a method of extraction employing a solvent selected from the group consisting of alkyl ketones, ethyl acetate, dichloromethane, chloroform, THF, diethyl ether, or a mixture thereof.

[0076] In another embodiment of present invention, the methyl furfuryl alcohol (5-MFA) of formula (III) is further reacted in presence of aluminum trichloride and ethanol to obtain 2-(ethoxymethyl)-5-methylfuran (EMMF) of formula (V).

##STR00012##

[0077] The suitable temperature for reaction may be variable from 80 to180° C. based on different base and solvent applied for this transformation. Preferably, the reaction is performed at the temperature in the range from 120 to140° C. to get highest yield with low by-product formation.

[0078] The reaction time may be selected from 2-6 hours or till completion of the reaction.

[0079] To enhance the scope of the present process, different 5-aldehyde substituted furan compounds have been used successfully for the production of 5-methyl substituted furans as proposed under the general formula (I).

[0080] In the process development different hydrazine analogues, inorganic bases and alcoholic solvents have been used for the selective formation of compounds proposed under general formula (I).

[0081] The present process for the preparation of the desired 5-methyl substituted furan of formula (I) in a highly selective manner involves use of amine compound for selective imine formation with aldehyde group of substituted furan compounds of formula (II). The base under alcoholic solvent condition specifically reduces the carbonyl group through proton transfer by producing nitrogen gas as one of the by-product.

[0082] Preferably, molar concentration/ratio of reactants is: aldehyde substituted furan (1 equiv.), amine compound (1-3 eqivs.), inorganic base (0.5-4 eqivs.).

[0083] The method of purification is selected from any suitable method known in the art, which include but is not limited to chromatography technique, distillation, crystallization etc.

[0084] Preferably, purification is performed by solvent extraction, fractional distillation and may be followed by other purification technique.

[0085] In yet another embodiment, the present invention provides a process for the preparation of 2-(ethoxymethyl)-5-methylfuran (EMMF) of formula (V) from 5-methyl furfuryl alcohol (5-MFA) of formula (III).

##STR00013##

[0086] In the present process, the optimized reagents, substrates, solvents and reaction conditions altogether are playing significant role to produce the desired compounds of general formula (I) with minimized by-product formation.

[0087] Further, the present process is applicable for scale-up production of 5-methyl substituted furan compounds of general formula (I) from different aldehyde substituted furan compounds; which could be applicable as a feedstock for bio-fuel and other commercially valuable products.

[0088] The scalable process for the preparation of 5-MFA as feedstock chemical could further be useful as precursor of biofuel such as 2,5-dimethylfuran (2,5-DMF) and other important bio-chemicals production (Scheme 1).

##STR00014##

Scheme 1. 5-MFA Production From 5-HMF is a Platform Compound for Biofuel and Other Important Bio-Chemicals Production

List of Abbreviations

[0089] HMF: 5-hydroxymethylfurfural [0090] DMF: 2,5-dimethylfuran [0091] 5-MFA: 5-methyl furfuryl alcohol [0092] MF: 2-methylfuran [0093] EMMF: 2-(ethoxymethyl)-5-methylfuran [0094] THF: Tetrahydrofuran [0095] GC-MS: Gas chromatography/Mass spectrometry [0096] NMR: Nuclear magnetic resonance [0097] TLC: Thin layer chromatography

Material and Method Used in Experiments

[0098] All the starting materials and solvents used were purchased from commercial suppliers such as Hydrazine hydrate and its analogs from Thomas Baker and Sigma, bases from Avra, solvents from CDH, SD Fine, the 5-HMF was used and prepared by our own patented process. (Application number: 201811023331) and other starting materials from Sigma and TCI.

EXAMPLES

General Experimental Procedure

[0099] An oven dried round bottomed flask (500 mL) was charged with base (0.5-2.0 eq.) and alcoholic solvent. The reaction mixture was heated at range of temperature 120° C. to 140° C. till the base completely got dissolved. In another round bottomed flask 5-HMF (1.0 eq.) was charged along with 2-butanol followed by the dropwise addition of hydrazine hydrate (1-3 eq.) with gentle agitation. 5-HMF mixture was added to the pre-dissolved basic solution gradually and refluxed at 120-130° C. for 2-6 hours. The progress of reaction was monitored by TLC and after completion of the reaction, the mixture was extracted by ethyl acetate/diethyl ether and dried over Na.sub.2SO.sub.4 followed by removal of solvent by distillation at 100-110° C. under vacuum gave crude product 5-MFA which further purified by vacuum distillation gave 5-MFA in 50-70% yield and >90% selectivity. The product was further analysed by GC-MS and NMR (.sup.1H and .sup.13C).

##STR00015##

Scheme 2. Synthesis of 5-Methylsubstituted Furans From 5-Aldehyde Substituted Furans

1. Experimental Procedure for 5-MFA Synthesis From 5-HMF

[0100] A dried batch reactor (15 L) was charged with KO.sup.tBu (106.8 g, 0.95 mol) and 2-butanol (1 L). The reaction mixture was heated, stirred and reflux at 130° C. till the base completely get dissolved. In another round bottomed flask, 5-HMF (100.0 g, 0.79 mol) was charged along with 2-butanol (300 mL) followed by the dropwise addition of hydrazine hydrate (78.0 mL, 1.58 mol) with gentle agitation. 5-HMF mixture was added to the pre-dissolved basic solution gradually and refluxed at 120-130° C. for 3-6 hours. The progress of the reaction was monitored by TLC and after completion of reaction, the mixture was extracted by ethyl acetate/diethyl ether and dried over Na.sub.2SO.sub.4 followed by removal of solvent by vacuum distillation at 100-110° C. gave 5-MFA, 45.15 g in 51% yield. The crude product was further analysed by GC-MS and NMR. .sup.1H NMR (300 MHz, CDCl.sub.3) δ 6.15 (d, 1 H, J = 3 Hz), 5.91 (d, 1 H, J = 3 Hz), 4.52 (s, 2 H), 2.29 (s, 3 H); .sup.13C NMR (300 MHz, CDCl.sub.3) δ 152.31, 152.30, 108.67, 106.19, 57.35, 13.48; GC-MS [M].sup.+= 112

##STR00016##

Scheme 3. Synthesis of 5-MFA From 5-HMF

2. Experimental Procedure for 5-MFA Synthesis From 5-HMF

[0101] An oven dried round bottomed flask (500 mL) was charged with sodium tert. butoxide NaO.sup.tBu (18.2 g, 0.19 mol) and 2-butanol (25 mL). The reaction mixture was heated, stirred and reflux at 130° C. till base completely got dissolved. In another round bottomed flask HMF (20 g, 0.15 mmol) was charged along with 2-butanol (15 mL) followed by dropwise addition of hydrazine hydrate (11.6 mL, 0.23 mol), with gentle agitation. 5-HMF mixture was added to the pre-dissolved basic solution gradually and refluxed at 120-130° C. for 3-6 hours. The progress of reaction was monitored by TLC and after completion of reaction the mixture was extracted by ethyl acetate/diethyl ether and dried over Na.sub.2SO.sub.4 followed by removal of solvent by distillation at 100-110° C. gave crude product 5-MFA which further purified by vacuum distillation gave 5-MFA, 9.0 g in 50.5 % yield. The distilled reaction residue was further analysed by GC-MS and NMR. The spectral data was same as mentioned in scheme 2, compound III.

##STR00017##

Scheme 4. Synthesis of 5-MFA From 5-HMF

3. Experimental Procedure for 5-MFA Synthesis From 5-HMF

[0102] An oven dried round bottomed flask (250 mL) was charged with KOH (3.3 g, 0.05 mol) and 2-butanol (10 mL). The reaction mixture was heated, stirred and reflux at 130° C. till base completely got dissolved. In another round bottomed flask HMF (5.0 g, 0.03 mol) was charged along with 2-butanol (10 mL) followed by dropwise addition of hydrazine hydrate ( 2.9 mL, 0.05 mol) with gentle agitation. 5-HMF mixture was added to the pre-dissolved basic solution gradually and refluxed at 120-130° C. for 3-6 hours. The progress of reaction was monitored by TLC and after completion of reaction the mixture was extracted by ethyl acetate/diethyl ether and dried over Na.sub.2SO.sub.4 followed by removal of solvent by distillation at 100-110° C. gave crude product 5-MFA which further purified by vacuum distillation gave 5-MFA, 1.1 g in 25% yield. The distilled reaction residue was further analysed by GC-MS and NMR. The spectral data was same as mentioned in scheme 2, compound III.

##STR00018##

Scheme 5. Synthesis of 5-MFA From 5-HMF

4. Experimental Procedure for 2-Methylfuran Synthesis From 2-Furfuraldehyde

[0103] An oven dried round bottomed flask (100 mL) was charged with KO.sup.tBu (1.1 g, 0.010 mol) and 2-butanol (3 mL). The reaction mixture was heated, stirred and reflux at 130° C. till base completely got dissolved. In another round bottomed flask 2-furfuraldehyde (1.0 g, 0.01 mol) was charged along with 2-butanol (3 mL) followed by dropwise addition of hydrazine hydrate (1.02 mL, 0.020 mol) with gentle agitation. 2-furfuraldehyde mixture was added to the pre-dissolved basic solution gradually and refluxed at 120-130° C. for 3-6 hours. The progress of reaction was monitored by TLC and after completion of reaction the mixture was analysed by GC-MS. The product was further analysed by GC-MS and compare with standard.

##STR00019##

Scheme 6. Synthesis of 2-Methylfuran From 2-Furfuraldehyde

5. Experimental Procedure for 2,5-Dimethylfuran (DMF) Synthesis From 2,5-Diformylfuran

[0104] An oven dried round bottomed flask (100 mL) was charged with KO.sup.tBu (45.0 mg, 0.403 mmol) and 2-butanol (1.5 mL). The reaction mixture was heated, stirred and reflux at 130° C. till base completely got dissolved. In another round bottomed flask 2,5-diformylfuran (100 mg, 0.806 mmol) was charged along with 2-butanol (3 mL) followed by dropwise addition of hydrazine hydrate (79 .Math.L, 1.612 mmol) with gentle agitation. 2,5-diformylfuran mixture was added to the pre-dissolved basic solution gradually and refluxed at 130° C. for 3-5 hours. The progress of reaction was monitored by TLC and after completion of reaction the mixture was analysed by GC-MS. The product was further analysed by GC-MS and compared with standard.

##STR00020##

Scheme 7. Synthesis of 2,5-Dimethylfuran From 2,5-Diformylfuran

6. Experimental Procedure for 2-Ethyl-5-Methylfuran Synthesis From 5-Ethylfuran-2-Carbaldehyde

[0105] An oven dried round bottomed flask (100 mL) was charged with KO.sup.tBu (45.0 mg, 0.403 mmol) and 2-butanol (1.5 mL). The reaction mixture was heated, stirred and reflux at 130° C. till base completely got dissolved. In another round bottomed flask 5-ethylfuran-2-carbaldehyde (100 mg, 0.805 mmol) was charged along with 2-butanol (3 mL) followed by dropwise addition of hydrazine hydrate (79 .Math.L, 1.611 mmol) with gentle agitation. 5-Ethylfuran-2-carbaldehyde mixture was added to the pre-dissolved basic solution gradually and refluxed at 120-130° C. for 3-5 hours. The progress of reaction was monitored by TLC and after completion of reaction the mixture was analysed by GC-MS and compared with standard.

##STR00021##

Scheme 8. Synthesis of 2-Ethyl-5-Methylfuran from 5-Ethylfuran-2-Carbaldehyde

7. Experimental Procedure for 4,5-Dimethylfuran-2-Carbaldehyde Synthesis

[0106] An oven dried round bottomed flask (100 mL) was charged with KO.sup.tBu (45.0 mg, 0.403 mmol) and 2-butanol (1.5 mL). The reaction mixture was heated, stirred and reflux at 130° C. till base completely got dissolved. In another round bottomed flask 4,5-dimethylfuran-2-carbaldehyde (100 mg, 0.806 mmol) was charged along with 2-butanol (3 mL) followed by dropwise addition of hydrazine hydrate (79 .Math.L, 1.612 mmol) with gentle agitation. 4,5-dimethylfuran-2-carbaldehyde mixture was added to the pre-dissolved basic solution gradually and refluxed at 120-130° C. for 3-5 hours. The progress of reaction was monitored by TLC and after completion of reaction the mixture was analysed by GC-MS and compared with standard.

##STR00022##

Scheme 9. Synthesis of 2,3,5-Trimethylfuran from 4,5-Dimethylfuran-2-Carbaldehyde

8. Experimental Procedure for 2-(Ethoxymethyl)-5-Methylfuran (EMMF) Synthesis from 5-MFA

[0107] An oven dried round bottomed flask (100 mL) was charged with 5-MFA (100 mg, 0.8919 mmol) and ethanol (2 mL) followed by the addition of aluminium trichloride (3.56 mg, 0.0267 mmol). Heat and stirred the reaction mass under reflux at 90° C. for 4-12 hr. The progress of the reaction was monitored by TLC and after completion of the reaction the reaction mixture was neutralized with sodium bicarbonate followed by the extraction with diethyl ether/ethyl acetate. The extract of the reaction was dried over sodium sulphate and concentrated under vacuum to get desired product compound V with approximately quantitative conversion. The product was further analysed by GC-MS and compared with standard.

##STR00023##

Scheme 10. Synthesis of EMMF From 5-MFA

The Main Advantages of the Present Invention Are

[0108] 1. A simple, atom-economy and cost-effective process has been developed for the preparation of 5-methyl substituted furans from 5-aldehyde substituted furans.

[0109] 2. Under this process no hydrogen gas and metal has been used and easy to scale-up and no need of tedious purification to achieve high yield.

[0110] 3. No over reduction was noticed under this process and product separation is easy by solvent extraction and distillation.

[0111] 4. No need of high-pressure autoclave system and the reaction performed under reflux condition therefore reduces the risk.

[0112] 5. The process could be applicable for low cost production of highly demanding platform compound 5-MFA, 2,5-DMF and other 5-methyl substituted furan compounds as a biofuel and other applications.

[0113] 6. 5-MFA is a very good choice for 2,5-DMF production following energy efficient process.

[0114] 7. Etherification of 5-MFA can be done under milder acidic condition with different alkyl alcohols having huge application as biofuel and bio-diesel.