Hydrochloric Acid → 4,5-Dihydro-8-methylthio-2-phenylthieno[3,4-e]benzothiazole-6-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

Ethyl 4,5-dihydro-8-methylthio-2-phenylthieno[3,4-e]benzothiazole-6-carboxylate (2.28 g) was suspended in a mixed solvent of ethanol (15 ml) and tetrahydrofuran (25 ml); a 2 N aqueous solution of sodium hydroxide (8.8 ml) was added at 50° C. After the reaction mixture was stirred at 50° C. for 4 hours, the solution obtained was poured over water (400 ml), acidified with concentrated hydrochloric acid, and extracted with ethyl acetate-tetrahydrofuran (3:1, v/v). The organic layer was washed with water and dried (MgSO4), after which the solvent was distilled off to yield 4,5-dihydro-8-methylthio-2-phenylthieno[3,4-e]benzothiazole-6-carboxylic acid (2.08 g, 98.6%), which was then recrystallized from chloroform-methanol. Light-yellow prisms. Melting point 255-256° C. (decomposed).

Provenance & Evidence