Hydrochloric Acid → 4,5-Dihydro-2-methyl-8-methylthiothieno[3,4-g]benzoxazole-6-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

Ethyl 4,5-dihydro-2-methyl-8-methylthiothieno[3,4-g]benzoxazole-6-carboxylate (1.88 g) was suspended in a mixed solvent of ethanol (15 ml) and tetrahydrofuran (10 ml); a 2 N aqueous solution of sodium hydroxide (9.1 ml) was added at 50° C. After the reaction mixture was stirred at 50° C. for 2 hours, the solution obtained was poured over water (300 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-2-methyl-8-methylthiothieno[3,4-g]benzoxazole-6-carboxylic acid (1.61 g, 94.2%), which was then recrystallized from chloroform-methanol. Light-yellow prisms. Melting point over 300° C.

Provenance & Evidence