Dimethylformamide → N-ethyl-4,5-dihydro-8-methylthio-2-phenylthieno[3,4-e]benzothiazole-6-carboxamide

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Reaction Steps

4,5-Dihydro-8-methylthio-2-phenylthieno[3,4-e]benzothiazole-6-carboxylic acid (0.43 g) was suspended in tetrahydrofuran (15 ml); oxalyl chloride (0.23 g) and then N,N-dimethylformamide (6 μl) were added. After this mixture was stirred at room temperature for 2 hours, it was concentrated under reduced pressure. The residue was suspended in tetrahydrofuran (5 ml) and cooled with ice; a 70% aqueous solution of ethylamine (4.0 ml) was added. After the reaction mixture was stirred at room temperature for 1 hour, it was poured over water (150 ml) 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 N-ethyl-4,5-dihydro-8-methylthio-2-phenylthieno[3,4-e]benzothiazole-6-carboxamide (0.35 g, 76%), which was then recrystallized from chloroform-ethanol. Yellow needles. Melting point 211-212° C.

Provenance & Evidence