Dimethyl Carbonate → methyl 4-oxo-5,6,7,8-tetrahydro-4H-cyclohepta[b]thiophene-5-carboxylate

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Reaction Steps

To a solution of 5,6,7,8-tetrahydro-cyclohepta[b]thiophen-4-one (0.84 g, 5 mmol), prepared by the method of M. P. Cagniant (Bull. Soc. Chim. France, 1956, 1152-1163), in dimethylcarbonate (6 mL) was added a 60% dispersion of sodium hydride in oil (0.4 g, 10 mmol) and a few drops of dry methanol. The reaction mixture was heated at reflux for 4 hours, then cooled, quenched with 2 N hydrochloric acid solution, and the desired product was extracted with ethyl acetate. The combined organic layers were dried over magnesium sulfate, concentrated and chromatographed on silica gel, eluting with 20% ethyl acetate:hexane to provide the title compound: 1H NMR (300 MHz, DMSO-d6) δ 7.34 (d, J=5.42 Hz, 1H,), 7.28 (d, J=5.42 Hz, 1H), 4.04 (dd, J=10.8, 3.39 Hz, 1H), 3.66 (s, 3H), 3.80 (m, 4H), 3.14 (m, 2H); MS (DCI/NH3) m/z 225 (M+H)+, 242 (M+NH4)+.

Provenance & Evidence