Ethanol → 4,5-Dihydro-2-methyl-8-methylthiothieno[3,4-e]benzothiazole-6-carboxylic acid

Participants

Reaction Steps

Ethyl 4,5-dihydro-2-methyl-8-methylthiothieno[3,4-e]benzothiazole-6-carboxylate (0.76 g) was suspended in a mixed solvent of ethanol (10 ml) and tetrahydrofuran (25 ml); a 2 N aqueous solution of sodium hydroxide (2.3 ml) was added at room temperature. After the reaction mixture was stirred at room temperature for 1 hour, the solution obtained was diluted with water (30 ml) and washed with diethyl ether. The water layer was acidified with 1 N hydrochloric acid (5 ml) and extracted with a mixed solvent of ethyl acetate and tetrahydrofuran. The ethyl acetate-tetrahydrofuran layer was washed with water and dried (MgSO4), after which the solvent was distilled off to yield 4,5-dihydro-2-methyl-8-methylthiothieno[3,4-e]benzothiazole-6-carboxylic acid (0.35 g, 50%), which was then recrystallized from ethyl acetate-hexane. Brown prisms. Melting point 273-274° C.

Provenance & Evidence