Methyl tetrahydro-4-methyl-3-oxo-2-thiophenecarboxylate → Ethyl 5,5-dimethyl-3-oxothiolane-2-carboxylate

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Reaction Steps

The keto esters, alkyl 4-oxo-2,3,4,5-tetrahydrothiophene-3-carboxylate and alkyl 3-oxo-2,3,4,5-tetrahydrothiophene-2-carboxylate may be prepared by the procedure of Woodward and Eastman, J. Am. Chem. Soc. 68, 2229 (1946); alkyl 4-oxo-2,3,5,6-tetrahydro-4H-thiopyran-3-carboxylate by the method of G.M. Bennett and L. V. D. Scorah, J. Chem. Soc., 194, (1927); and alkyl 3-oxo-2,3,4,5-tetrahydro-6H-thiopyran-2-carboxylate by the procedure of Leonard and Figueras, J. Chem. Soc., 74, 917 (1952). Methyl 4-methyl-3-oxo-tetrahydrothiophene-2-carboxylate is disclosed in Chemical Abstracts, 63, 5491 (1965). Ethyl 5,5-dimethyl-3-oxo-tetrahydrothiophene-2-carboxylate is prepared by reacting diethyl 4,4-dimethyl-3-thiahexanedioate with potassium tertiary butoxide. 5-methyl-3-oxo-tetrahydrothiophene-2-carboxylate is formed by reacting diethyl 4-methyl-3-thiahexanedioate with potassium tertiary butoxide.

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