| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | 26.03.2002 |
| PATENT TITLE |
Process for the preparation of .alpha.-methylene-.gamma.-butyrolactone and .alpha.-acetoxymethyl-.gamma.-butyrolactone |
| PATENT ABSTRACT |
This invention pertains to a process for making .alpha.-methylene-.gamma.-butyrolactone by acid-catalyzed rearrangement of tetrahydro-3-furoic acid. In a further embodiment, when tetrahydro-3-furoic acid is treated with acetic anhydride and an acid catalyst, .alpha.-acetoxymethyl-.gamma.-butyrolactone is produced in high yield. Under basic conditions, .alpha.-acetoxymethyl-.gamma.-butyrolactone can readily form.alpha.-methylene-.gamma.-butyrolactone by the elimination of acetic acid. These reactions provide .alpha.-methylene-.gamma.-butyrolactone by novel routes which do not require butyrolactone or formaldehyde. |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | November 10, 2000 |
| PATENT REFERENCES CITED |
J. Martin, et al., A New method for the synthesis of Alpha-Methylenebutyrolactones, J. Chem. Soc., 1970, 1:27, Dow Chemical Company, Wayland, Massachusetts. A. W. Murray, et al., Convenient Synthesis of Alpha-Epoxylactones (4-Oxo-1,5-dioxaspiro[2.4]heptanes and -[2.5]octanes), Synthesis, 1985, 1:35-38, University of Dundee, Scotland. F. Gelman, et al., One-Pot Reactions with Opposing Reagents: Sol-Gel Entrapped Catalyst and Base, J. Am. Chem. Soc., 2000, Hebrew University of Jerusalem, Israel. |
| PATENT PARENT CASE TEXT | This data is not available for free |
| PATENT CLAIMS |
What is claimed is: 1. A process for preparing .alpha.-methylene-.gamma.-butyrolactone comprising heating a mixture of a furoic acid selected from the group consisting of tetrahydro-3-furoic acid and esters of tetrahydro-3-furoic acid and a strong acid catalyst under conditions whereby .alpha.-methylene-.gamma.-butyrolactone is formed and optionally recovering the .alpha.-methylene-.gamma.-butyrolactone. 2. The process of claim 1 wherein the furoic acid and the strong acid catalyst are heated at a temperature of from about 20.degree. C. to about 400.degree. C. 3. The process of claim 2 wherein the temperature is from about 100.degree. C. to about 200.degree. C. 4. The process of claim 1 wherein the strong acid catalyst is selected from the group consisting of fluorosulfonic acid, trifluoromethanesulfonic acid, sulfuric acid, benzenesulfonic acid, toluenesulfonic acid and phosphoric acid. 5. The process of claim 1 wherein the furoic acid and strong acid catalyst are combined in a ratio of furoic acid:strong acid catalyst of from about 1:1,000 to about 1,000:1 w/w. 6. The process of claim 1 where the strong acid catalyst is a perfluorocarbon sulfonic acid membrane and the furoic acid:perfluorocarbon sulfonic acid membrane ratio is from about 1:1,000 to about 10,000:1 w/w. 7. The process of any of claim 1, 2, 4 or 6 wherein the furoic acid is tetrahydro-3-furoic acid. 8. The process of any of claim 1, 2, 4 or 6 wherein the furoic acid is an ester of tetrahydro-3-furoic acid. 9. A process for preparing .alpha.-acetoxymethyl-.gamma.-butyrolactone comprising heating a mixture of a furoic acid selected from the group consisting of tetrahydro-3-furoic acid and esters of tetahydro-3-furoic acid, with acetic anhydride and a strong acid catalyst under conditions wherein .alpha.-acetoxymethyl-.gamma.-butyrolactone is formed and optionally recovering the .alpha.-acetoxymethyl-.gamma.-butyrolactone. 10. The process of claim 9 wherein the furcic acid, acetic anhydride and a strong acid catalyst are heated from about 20.degree. C. to about 200.degree. C. 11. The process of claim 10 wherein the furoic acid, acetic anhydride and a strong acid catalyst are heated from about 50.degree. C. to about 120.degree. C. 12. The process of claim 9 wherein the strong acid catalyst is selected from the group consisting of trifluoromethanesulfonic acid, sulfuric acid, benzenesulfonic acid, toluenesulfonic acid, phosphoric acid and perfluorocarbon sulfonic acid membrane. 13. The process of claim 9 wherein the furoic acid and strong acid catalyst are combined in a ratio of furoic acid:strong acid catalyst from about 1:1,000 to about 10,000:1 w/w, and wherein the furoic acid:acetic anhydride ratio is from about 10:1 to about 1:10,000 w/w. 14. The process of any of claim 9, 10, 12 or 13 wherein the furoic acid is tetrahydro-3-furoic acid. 15. The process of any of claim 9, 10, 12 or 13 wherein the furoic acid is an ester of tetrahydro-3-furoic acid. 16. The product produced by of the process of any of claim 9, 11, 10, 12 or 13. 17. An .alpha.-acetoxymethyl-.gamma.-butyrolactone composition according to the formula: ##STR5## 18. A process for preparing .alpha.-methylene-.gamma.-butyrolactone comprising heating a mixture of .alpha.-acetoxymethyl-.gamma.-butyrolactone and base catalyst under conditions whereby .alpha.-methylene-.gamma.-butyrolactone is formed and optionally recovering the .alpha.-methylene-.gamma.-butyrolactone. 19. The process of claim 18 wherein the .alpha.-acetoxymethyl-.gamma.-butyrolactone and base catalyst are heated at a temperature of from about 40.degree. C. to about 200.degree. C. 20. The process of claim 18 wherein the .alpha.-acetoxymethyl-.gamma.-butyrolactone and base catalyst are heated at a temperature of from about 60.degree. C. to about 120.degree. C. 21. The process of claim 18 wherein the base catalyst is any base which forms an acetate when reacted with acetic acid. 22. The process of claim 21 wherein the base catalyst is defined according to the formula, M(acetate).sub.x ; wherein x is an integer selected from the group consisting of 1 and 2; and M is a cation of charge +x selected from the group consisting of Li.sup.+, Na.sup.+, K.sup.+, Rb.sup.+, Cs.sup.+, Mg.sup.++, Ca.sup.++, Sr.sup.++, Ba.sup.++, (CH.sub.3).sub.4 N.sup.+, (C.sub.2 H.sub.5).sub.4 N.sup.+, (CH.sub.3).sub.4 P.sup.+, (C.sub.2 H.sub.5).sub.4 P.sup.+ and 1-ethyl-3-methylimidazolium cation. 23. The process of claim 22 wherein the base is selected from the group consisting of tetramethylammonium acetate and 1-ethyl-3-methylimidazolium acetate. 24. A process for preparing .alpha.-methylene-.gamma.-butyrolactone comprising: (a) combining a furoic acid selected from the group consisting of tetrahydro-3-furoic acid and an ester of tetrahydro-3-furoic acid with an acid anhydride and a strong acid catalyst under conditions whereby a .alpha.-carboxylatomethyl-.gamma.-butyrolactone is formed; (b) heating the product of step (a) under conditions whereby .alpha.-methylene-.gamma.-butyrolactone is formed; and (c) optionally recovering the .alpha.-methylene-.gamma.-butyrolactone. 25. The process of claim 24 wherein the combining of step (a) is conducted at a temperature from about 20.degree. C. to about 200.degree. C. 26. The process of claim 24 wherein the heating of step (b) is conducted at a temperature from about 100.degree. C. to about 400.degree. C. 27. The process of claim 24 wherein the acid anhydride is selected from the group consisting of acetic anhydride, formic-acetic anhydride, propionic anhydride, benzoic anhydride, phthalic anhydride, anhydrides of poly(acrylic acid), succinic anhydride, monomethylsuccinic anhydride, 2,2'-dimethylsuccinic anhydride and 2,3-dimethylsuccinic anhydride. 28. The process of claim 24 wherein at step (b) the product of step (a) is heated in the presence of a base catalyst at a temperature of about 40.degree. C. to about 200.degree. C. 29. The process of claim 28 wherein the base catalyst is defined according to the formula, M(carboxylate).sub.x ; wherein x is an integer selected from the group consisting of 1 and 2; and M is a cation of charge +x chosen from the group consisting of Li.sup.+, Na.sup.+, K.sup.+, Rb.sup.+, Cs.sup.+, Mg.sup.++, Ca.sup.++, Sr.sup.++, Ba.sup.++, (CH.sub.3).sub.4 N.sup.+, (C.sub.2 H.sub.5).sub.4 N.sup.+, (CH.sub.3).sub.4 P.sup.+, (C.sub.2 H.sub.5).sub.4 P.sup.+ and 1-ethyl-3-methylimidazolium cation; and carboxylate is selected from the group consisting of formate, acetate, propionate, benzoate, phthalate, poly(acrylate), succinate, monomethylsuccinate, 2,2'-dimethylsuccinate and 2,3-dimethylsuccinate. 30. The process of claim 24 wherein the strong acid catalyst is selected from the group consisting of trifluoromethanesulfonic acid, sulfuric acid, benzenesulfonic acid, toluenesulfonic acid, phosphoric acid and perfluorocarbon sulfonic acid membrane. 31. The process of claim 24 wherein the furoic acid and strong acid catalyst are combined in a ratio of furoic acid:strong acid catalyst from about 1:1,000 to about 10,000:1 w/w. 32. The process of claim 24 wherein the furoic acid:acid anhydride ratio is from about 100:1 to about 1:10,000 w/w. 33. The process of claim 24 wherein the strong acid catalyst is a perfluorocarbon sulfonic acid membrane and the base catalyst is an acetate loaded anion exchange resin. 34. The process of claim 24 wherein the furoic acid is tetrahydro-3-furoic acid. 35. The process of claim 24 wherein the furoic acid is an ester of tetrahydro-3-furoic acid. 36. A process for preparing .alpha.-methylene-.gamma.-butyrolactone comprising heating a mixture of a gaseous furoic acid selected from the group consisting of tetrahydro-3-furoic acid and esters of tetrahydro-3-furoic acid and a gas phase base catalyst under conditions whereby .alpha.-methylene-.gamma.-butyrolactone is formed and optionally recovering the .alpha.-methylene-.gamma.-butyrolactone. 37. The process of claim 36 wherein the gaseous furoic acid and the gas phase base catalyst are heated at a temperature from about 100.degree. C. to about 600.degree. C. 38. The process of claim 36 wherein the gas phase base catalyst is selected from the group consisting of magnesium oxide, calcium oxide, strontium oxide, barium oxide, magnesium hydroxide, calcium hydroxide, cadmium oxide, potassium hydroxide, strontium hydroxide, rubidium oxide, sodium hydroxide, lithium hydroxide and barium hydroxide. 39. The process of claim 37 wherein the gas phase base catalyst is optionally supported on a suitable support. 40. The process of claim 39 wherein the suitable support is selected from the group consisting of silica, titania, zirconia, alumina and various zeolites. |
| PATENT DESCRIPTION |
FIELD OF THE INVENTION This invention is in the field of synthetic organic chemistry. This invention pertains to simple, efficient and economic methods to produce .alpha.-methylene-.gamma.-butyrolactone from tetrahydro-3-furoic acid and .alpha.-acetoxymethyl-.gamma.-butyrolactone. TECHNICAL BACKGROUND OF THE INVENTION .alpha.-Methylenelactones have been the subject of intensive synthetic studies. Specifically, the .alpha.-methylene-.gamma.-butyrolactone group is an important structural feature of many sesquiterpenes of biological importance. In addition, .alpha.-methylene-.gamma.-butyrolactone, or its hydrogenated product, 3-methyltetra-hydrofuran, are regarded as a potential key monomers in both homopolymers and copolymers. Currently the cost of .alpha.-methylene-.gamma.-butyrolactone is too high to warrant commercial production of its resulting polymers. Some of the current synthetic routes suffer from low yields, byproducts and expensive starting materials. In the instant invention, high yields of .alpha.-methylene-.gamma.-butyrolactone are obtained by an acid-catalyzed rearrangement of tetrahydro-3-furoic acid or base-catalyzed reaction of .alpha.-acetoxymethyl-.gamma.-butyrolactone. An early synthesis of .alpha.-methylene-.gamma.-butyrolactone involved two steps (Martin et al., J. Chem. Soc. D 1:27 (1970)). The first is carboxylation of .gamma.-butyrolactone with methyl methoxymagnesium carbonate (Stiles' reagent) to produce the acid. Next, the acid is briefly treated with a mixture of aqueous formaldehyde and diethylamine, followed by a separate treatment of the crude product with sodium acetate in acetic acid. The first step requires 6-7 hours and affords almost quantitative yields, whereas the second step can be accomplished in less than 30 minutes but with yields of only 50%. Murray et al. (Synthesis 1:35-38 (1985); see also U.S. Pat No. 5,166,357) disclose a route to .alpha.-methylene-.gamma.-butyrolactone that also involves a two-step sequence consisting of the reaction of .gamma.-butyrolactone with ethyl formate in the presence of base, followed by refluxing the resulting .alpha.-formyl-.gamma.-butyrolactone sodium salt under nitrogen with paraformaldehyde in tetrahydrofuran. Distillation affords the desired .alpha.-methylene-.gamma.-butyrolactone as a colorless oil. This reaction sequence can best be explained by formyl transfer from carbon to oxygen followed by elimination of carboxylate anion. Essentially all approaches to .alpha.-methylene-.gamma.-butyrolactone are liquid-phase processes. One exception is the vapor-phase process described in JP 10120672. Production of .alpha.-methylene-.gamma.-butyrolactone comprises subjecting .gamma.-butyrolactone or an alkyl-substituted .gamma.-butyrolactone, in which one or more hydrogen atoms at the .beta.- or .gamma.-position of the .gamma.-butyrolactone are substituted with C.sub.1 -C.sub.18 alkyl groups, to a gaseous phase catalytic reaction using a raw material gas containing formaldehyde or its derivative in the presence of a catalyst. Molecular oxygen is preferably added to the raw material gas and the catalyst is preferably silica alumina catalyst. Specifically, a gaseous mixture of .gamma.-butyrolactone, formaldehyde, water, nitrogen and oxygen was passed through a reactor packed with Wakogel C-200, pretreated with an aqueous potassium hydroxide solution and heating, at 330.degree. C., to afford .alpha.-methylene-.gamma.-butyrolactone at a conversion of 35.5% and a selectivity of 46.9%. Although the above methods for the production of .alpha.-methylene-.gamma.-butyrolactone are useful, they are time consuming and are multipart processes. Therefore, the problem to be solved is to find a simple and efficient method to produce .alpha.-methylene-.gamma.-butyrolactone. The present methods represent an advance in the art by offering processes that are a single or double step with high yields and good selectivity. SUMMARY OF THE INVENTION The present invention provides a process for the preparation of .alpha.-methylene-.gamma.-butyrolactone comprising heating a mixture of a furoic acid selected from the group consisting of tetrahydro-3-furoic acid and esters of tetrahydro-3-furoic acid, and a strong acid catalyst under conditions whereby .alpha.-methylene-.gamma.-butyrolactone is formed and optionally recovering the .alpha.-methylene-.gamma.-butyrolactone. Typically the acid catalyst is selected from the group consisting of fluorosulfonic acid, trifluoromethanesulfonic acid, sulfuric acid, benzenesulfonic acid, toluenesulfonic acid and phosphoric acid. In an alternate embodiment the invention provides a process for preparing .alpha.-acetoxymethyl-.gamma.-butyrolactone comprising heating a mixture of a furoic acid selected from the group consisting of tetrahydro-3-furoic acid and esters of tetrahydro-3-furoic acid, with acetic anhydride and a strong acid catalyst under conditions wherein .alpha.-acetoxymethyl-.gamma.-butyrolactone is formed and optionally recovering the .alpha.-acetoxymethyl-.gamma.-butyrolactone. In another embodiment the present invention provides a process for preparing .alpha.-methylene-.gamma.-butyrolactone comprising heating a mixture of a gaseous furoic acid selected from the group consisting of tetrahydro-3-furoic acid and esters of tetrahydro-3-furoic acid and a gas phase base catalyst under conditions whereby .alpha.-methylene-.gamma.-butyrolactone is formed and optionally recovering the .alpha.-methylene-.gamma.-butyrolactone. Gas phase catalysts may be supported on suitable supports such as silica for example. The invention additionally provides a novel composition of .alpha.-acetoxy-methyl-.gamma.-butyrolactone according to the formula ##STR1## Another embodiment of the invention relates to a process for preparing .alpha.-methylene-.gamma.-butyrolactone comprising heating a mixture of .alpha.-acetoxymethyl-.gamma.-butyrolactone and base catalyst under conditions whereby .alpha.-methylene-.gamma.-butyrolactone is formed and optionally recovering the .alpha.-methylene-.gamma.-butyrolactone. Within the context of this embodiment the base catalyst may be any base which forms an acetate when reacted with acetic acid and is typically defined according to the formula, M(acetate).sub.x ; where x is an integer selected from the group consisting of 1 and 2; and M is a cation of charge +x selected from the group consisting of Li.sup.+, Na.sup.+, K.sup.+, Rb.sup.+, Cs.sup.+, Mg.sup.++, Ca.sup.++, Sr.sup.++, Ba.sup.++, (CH.sub.3).sub.4 N.sup.+, (C.sub.2 H.sub.5).sub.4 N.sup.+, (CH.sub.3).sub.4 P.sup.+, (C.sub.2 H.sub.5).sub.4 P.sup.+ and 1-ethyl-3-methylimidazolium cation. The invention additionally provides a process for preparing .alpha.-methylene-.gamma.-butyrolactone comprising: (a) combining a furoic acid selected from the group consisting of tetrahydro-3-furoic acid and an ester of tetrahydro-3-furoic acid with an acid anhydride and a strong acid catalyst under conditions whereby a .alpha.-carboxylatomethyl-.gamma.-butyrolactone is formed; (b) heating the product of step (a) under conditions whereby .alpha.-methylene-.gamma.-butyrolactone is formed; and (c) optionally recovering the .alpha.-methylene-.gamma.-butyrolactone. Typically the production of .alpha.-carboxylatomethyl-.gamma.-butyrolactone will occur at temperatures of about 20.degree. C. to about 200.degree. C. whereas the heating step will occur at temperatures of about 100.degree. C. to about 400.degree. C. Optionally abase catalyst may be added to the product of step (a) to effect the conversion of o-carboxylatomethyl-.gamma.-butyrolactone to .alpha.-methylene-.gamma.-butyrolactone. Under these conditions the temperature required for conversion is less, and will range from about 40.degree. C. to about 200.degree. C. Within the context of this embodiment the base catalyst may be defined according to the formula, M(carboxylate).sub.x where x is an integer selected from the group consisting of 1 and 2; and M is a cation of charge +x chosen from the group consisting of Li.sup.+, Na.sup.+, K.sup.+, Rb.sup.+, Cs.sup.+, Mg.sup.++, Ca.sup.++, Sr.sup.++, Ba.sup.++, (CH.sub.3).sub.4 N.sup.+, (C.sub.2 H.sub.5).sub.4 N.sup.+, (CH.sub.3).sub.4 P.sup.+, (C.sub.2 H.sub.5).sub.4 P.sup.+ and 1-ethyl-3-methylimidazolium cation; and carboxylate is selected from the group consisting of formate, acetate, propionate, benzoate, phthalate, poly(acrylate), succinate, monomethylsuccinate, 2,2'-dimethylsuccinate and 2,3-dimethylsuccinate. DETAILED DESCRIPTION OF THE INVENTION .alpha.-Methylene-.gamma.-butyrolactone is useful as a key monomer in both homopolymers and copolymers. The instant invention pertains to a process for making .alpha.-methylene-.gamma.-butyrolactone by acid-catalyzed rearrangement of tetrahydro-3-furoic acid (Scheme I). In an alternate embodiment, when tetrahydro-3-furoic acid or esters of tetrahydro-3-furoic acid are treated with acetic anhydride and an acid catalyst, .alpha.-acetoxymethyl-.gamma.-butyrolactone is produced in high yield (Scheme II). Under either basic conditions, or high temperature (100.degree. C.-400.degree. C.) .alpha.-acetoxymethyl-.gamma.-butyrolactone can readily form .alpha.-methylene-.gamma.-butyrolactone by the elimination of acetic acid. Acid anhydrides other than acetic acid similarly can be used to form .alpha.-methylene-.gamma.-butyrolactone within the scope of this embodiment. These reactions provide .alpha.-methylene-.gamma.-butyrolactone by two novel routes which do not require butyrolactone or formaldehyde. ##STR2## ##STR3## Additionally the invention provides a novel compound, .alpha.-acetoxymethyl-.gamma.-butyrolactone which may serve as an intermediate or starting material for the production of .alpha.-methylene-.gamma.-butyrolactone (Scheme II) and is potentially useful in its own right as pre-polymer or polymer additive. In the context of this disclosure, a number of terms and abbreviations shall be utilized for interpretation of the specification and the claims. The following definitions are provided. "Nuclear magnetic resonance" is abbreviated NMR. ".alpha.-methylene-.gamma.-butyrolactone" is abbreviated MBL ".alpha.-acetoxymethyl-.gamma.-butyrolactone" is abbreviated AMB As used herein the term "a .alpha.-carboxylatomethyl-.gamma.-butyrolactone" means a compound having the structure: ##STR4## wherein RC(.dbd.O)O is a carboxylato group, for example if R.dbd.CH.sub.3 then RC(.dbd.O)O is acetate. As used herein the term "strong acid catalyst" means any Bronstead acid with a pKa<1, capable of catalyzing the conversion of tetrahydro-3-furoic acid or esters of tetrahydro-3-furoic acid to either AMB or MBL under suitable conditions. The term "base or basic catalyst" or "strong base or basic catalyst" will refer to a basic catalyst useful in a low temperature, non-gas phase process for the production of .alpha.-methylene-.gamma.-butyrolactone. These catalysts are typically acetates or carboxylates. The term "gas phase base catalyst" refers to a basic catalyst used in a gas phase process for the production of .alpha.-methylene-.gamma.-butyrolactone. The term "furoic acid" as used herein will refer to the substituted furoic acids tetrahydro-3-furoic acid and esters of tetrahydro-3-furoic acid. Furoic Acids Furoic acids are useful as starting materials in the present invention, particularly tetrahydro-3-furoic acid and esters of tetrahydro-3-furoic acid. Suitable esters of tetrahydro-3-furoic acid include but are not limited to methyl tetrahydro-3-furoate, ethyl tetrahydro-3-furoate, propyl tetrahydro-3-furoate, butyl tetrahydro-3-furoate, and phenyl tetrahydro-3-furoate. The furoic acid may be provided in any state including solid, liquid or gaseous form, depending on the requirements of the reaction. Acid Catalyst The present invention provides an acidic catalyst for the conversion of tetrahydro-3-furoic acid to .alpha.-methylene-.gamma.-butyrolactone or .alpha.-acetoxymethyl-.gamma.-butyrolactone. Such catalysts are common and well known in the art. Suitable in the present invention are any Bronstead acids with a pKa<1, capable of catalyzing the conversion of tetrahydro-3-furoic acid or esters of tetrahydro-3-furoic acid to either AMB or MBL. For example suitable acids will include but are not limited to fluorosulfonic acid, trifluoromethanesulfonic acid, Nafion.RTM. perfluorocarbon sulfonic acid membrane, sulfuric acid, benzenesulfonic acid, toluenesulfonic acid and phosphoric acid. These acids may be used independently or jointly. A particularly useful acid catalyst is trifluoromethanesulfonic acid. The amount of time required for complete conversion of the furoic acid starting material to product will vary with contact temperature. The temperature of the reaction for the conversion of tetrahydro-3-furoic acid to .alpha.-methylene-.gamma.-butyrolactone can range from about 20.degree. C. to about 400.degree. C., where a range of about 100.degree. C. to about 200.degree. C. is particularly suitable. The temperature of the reaction for the conversion of tetrahydro-3-furoic acid to .alpha.-acetoxymethyl-.gamma.-butyrolactone can range from about 20.degree. C. to about 200.degree. C., where a range of about 50.degree. C. to about 120.degree. C. is particularly suitable. Reaction times may vary from about 30 minutes under high temperature conditions to about 100 hours under less favorable temperature conditions. Typically reactions may be completed in about 1 to about 24 hours. Base Catalyst and Gas Phase Base Catalyst The present invention provides a basic catalyst for the conversion of .alpha.-acetoxymethyl-.gamma.-butyrolactone, where acetic anhydride is an element of the reaction mixture, to .alpha.-methylene-.gamma.-butyrolactone. Such catalysts are common and well known in the art. Where acetic anhydride is an element of the reaction mixture a suitable base catalyst is any base that will form an acetate upon reacting with acetic acid. In this context, suitable bases will be defined by the formula M(acetate).sub.x, where x is 1 or 2; M is a cation of charge +x, including but not limited to Li.sup.+, Na.sup.+, K.sup.+, Rb.sup.+, Cs.sup.+, Mg.sup.++, Ca.sup.++, Sr.sup.++, Ba.sup.++, (CH.sub.3).sub.4 N.sup.+, (C.sub.2 H.sub.5).sub.4 N.sup.+, (CH.sub.3).sub.4 P.sup.+, (C.sub.2 H.sub.5).sub.4 P.sup.+ and 1-ethyl-3-methylimidazolium cations. Particularly suitable in the present invention are the bases tetramethylammonium acetate and 1-ethyl-3-methylimidazolium acetate. Alternatively, where any acid anhydride is an element of the reaction the base will be defined by the formula, M(carboxylate).sub.x, where x is 1 or 2; M is a cation of charge +x including, but not limited to Li.sup.+, Na.sup.+, K.sup.+, Rb.sup.+, Cs.sup.+, Mg.sup.++, Ca.sup.++, Sr.sup.++, Ba.sup.++, (CH.sub.3).sub.4 N.sup.+, (C.sub.2 H.sub.5).sub.4 N.sup.+, (CH.sub.3).sub.4 P.sup.+, (C.sub.2 H.sub.5).sub.4 P.sup.+ and 1-ethyl-3-methylimidazolium cations; and the carboxylate may include formate, acetate, propionate, benzoate, phthalate, poly(acrylate), succinate, monomethyl-succinate, 2,2'-dimethylsuccinate and 2,3-dimethylsuccinate. It will be appreciated that any of the aforementioned bases may be used independently or jointly to effect the desired conversion. As with the acid catalyzed reactions the amount of time required for complete conversion of acetoxymethyl-.gamma.-butyrolactone to .alpha.-methylene-.gamma.-butyrolactone will vary with contact temperature. Typically temperature of the reaction can range from about 40.degree. C. to about 200.degree. C., where a range of about 60.degree. C. to about 140.degree. C. is particularly suitable. In an alternate embodiment the present invention provides a gas phase process for the production of .alpha.-methylene-.gamma.-butyrolactone where a gaseous furoic acid is passed over a gas phase base catalyst at high temperature. In this embodiment suitable temperatures may range from about 100.degree. C. to about 600.degree. C. Suitable gas phase base catalysts may include but are not limited to magnesium oxide, calcium oxide, strontium oxide, barium oxide, magnesium hydroxide, calcium hydroxide, cadmium oxide, potassium hydroxide, strontium hydroxide, rubidium oxide, sodium hydroxide, lithium hydroxide and barium hydroxide. The gas phase catalysts may be used individually or in any combination, or may optionally be supported on a variety of supports. Suitable supports are well known in the art and may include, but are not limited to silica, titania, zirconia, alumina and various zeolites. Acid Anhydride The present invention provides an acid anhydride for the conversion of tetrahydro-3-furoic acid or esters of tetrahydro-3-furoic acid to ".alpha.-carboxylato-methyl-.gamma.-butyrolactone". When the acid anhydride is acetic anhydride, the product is .alpha.-acetoxymethyl-.gamma.-butyrolactone. From this point the .alpha.-carboxylato-methyl-.gamma.-butyrolactone or .alpha.-acetoxymethyl-.gamma.-butyrolactone may be converted to end product either via the use of a base catalyst (discussed above) or by thermolysis at temperatures in the range of 100.degree. C. to 400.degree. C. Such anhydrides are common and well known in the art. In the context of the present invention, suitable anhydrides will include but are not limited to acetic anhydride, formic-acetic anhydride, propionic anhydride, benzoic anhydride, phthalic anhydride, anhydrides of poly(acrylic acid), succinic anhydride, monomethylsuccinic anhydride, 2,2'-dimethylsuccinic anhydride and 2,3-dimethylsuccinic anhydride. The preferred acid anhydride is acetic anhydride. Phthalic anhydride, anhydrides of poly(acrylic acid), succinic anhydride, monomethylsuccinic anhydride, 2,2'-dimethylsuccinic anhydride and 2,3-dimethylsuccinic anhydride all offer the possibly advantageous feature that the corresponding acids, which form during the course of the reaction, can be thermally dehydrated to recover the anhydride. The skilled person will recognize that optimization of any catalytic conversion will involve determination of a specific ratio of catalyst to starting material, and methods for determining such ratios are well established in the art. In the context of the present invention for the production of MBL the ratio of furoic acid reactant to the acid catalyst will range from about 1:1,000 to about 10,000:1 w/w where a ratio of about 1000:1 w/w is suitable. Similarly, where an acid anhydride is an element of the reaction the ratio of the furoic acid starting material and acid anhydride may range from about 10:1 to about 1:10,000 w/w where a range of about 1:1 to about 1:10,000 w/w is suitable. Segregated Acid Catalyst and Base Catalyst In one embodiment of the invention the conversion of tetrahydro-3-furoic acid to ABM or MBL was accomplished in a common vessel under conditions whereby the acid and base catalysts were segregated. Ordinarily, combining a strong acid catalyst with a basic catalyst results in immediate neutralization and loss of catalytic activity. However, this difficulty may be overcome if the acid catalyst and basic catalyst are separately maintained on segregated supports. In this fashion each catalyst maintains its individual catalytic activity without complete neutralization. In the context of the present invention, Nafion.RTM. perfluorocarbon sulfonic acid membrane was used as the requisite acid catalyst and acetate-loaded anion exchange resin (for example, Dowex.RTM. 1X8-100 beads) was used as the requisite basic catalyst in a single vessel conversion of tetrahydro-3-furoic acid to both ABM and MBL. Good conversions were observed for both products as indicated in Example 12. Reaction Conditions and Processes The present method lends itself to either batch or continuous processes. A continuous process employs a pipeline reactor for the tetrahydro-3-furoic acid to .alpha.-methylene-.gamma.-butyrolactone conversion. Liquid tetrahydro-3-furoic acid is fed into a pipe containing a catalyst bed where the reaction occurs to make .alpha.-methylene-.gamma.-butyrolactone. Any off-gases are vented out the end of the pipeline and the .alpha.-methylene-.gamma.-butyrolactone product falls out as a liquid. If needed, the mixture can be fed into the pipeline again to increase the overall conversion to .alpha.-methylene-.gamma.-butyrolactone. Alternatively, the reaction can run under continuous flow conditions, where water is constantly removed from the reaction medium and neither starting tetrahydro-3-furoic acid nor product .alpha.-methylene-.gamma.-butyrolactone is allowed to be present in concentration great enough for rapid polymerization. Recovery Methods .alpha.-methylene-.gamma.-butyrolactone, may be recovered using techniques common to the art. For example, when allowed to cool the .alpha.-methylene-.gamma.-butyrolactone reaction mixture, forms a viscous, clear mass. Alternatively, when heated under vacuum, the .alpha.-methylene-.gamma.-butyrolactone mixture can be distilled directly from the reaction mixture. Additionally, the reaction mixture can be dissolved in water, adjusted to pH=4 with 6N HCl, then distilled. Similarly, the separation of .alpha.-methylene-.gamma.-butyrolactone from byproducts can be accomplished using vacuum distillation with a spinning band column. Another method to recover the desired product is to polymerize .alpha.-methylene-.gamma.-butyrolactone using standard free-radical polymerization, isolate the polymer by precipitation from methanol, then thermally depolymerize back to .alpha.-methylene-.gamma.-butyrolactone by heating under vacuum. Finally, .alpha.-methylene-.gamma.-butyrolactone may also be separated from byproducts by melt crystallization. .alpha.-Acetoxymethyl-.gamma.-butyrolactone may be recovered by distillation methods comparable to distillation methods discussed above for the isolation of MBL. .alpha.-Acetoxymethyl-.gamma.-butyrolactone is relatively stable and has been distilled in vacuum at temperatures less than about 140.degree. C. to afford a colorless oil which crystallizes upon cooling and standing to a white crystalline compound, but it can thermolyze to .alpha.-methylene-.gamma.-butyrolactone and darkly-colored residue when heated much above that temperature. Given that pure .alpha.-acetoxymethyl-.gamma.-butyrolactone crystallizes at room temperature, care must be taken during its distillation to avoid plugging the condenser. The molecular structure of .alpha.-acetoxymethyl-.gamma.-butyrolactone as determined by single crystal X-ray diffraction revealed no extraordinary features. The identification of AMB was confirmed after purification by NMR and revealed the following spectral data: .sup.1 H NMR (500 MHz, CD.sub.2 Cl.sub.2) .delta.2.06 (s, 3H), 2.2 (m, 1H), 2.4 (m, 1H), 2.9 (m, 1H), 4.25 (m, 2H), 4.38 (m, 2H); .sup.13 C NMR (125 MHz, CD.sub.2 Cl.sub.2) .delta.21.1, 26.3, 39.8, 63.1, 67.4, 171.1, 177.1. .sup.1 H NMR spectra are reported in ppm downfield from tetramethylsilane; s=singlet and m=multiplet. Anal. Calcd. for C.sub.7 H.sub.10 O.sub.4 : C, 53.16%; H, 6.37. Found C, 53.12; H, 6.46. |
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