Thieno[2,3-b]thiophenes: Part 7. Some Heterocyclization Reactions with Ethyl 3,4-diamino-5-cyanothieno[2,3-b]thiophene-2-carboxylate.

Ethyl 3,4-diamino-5-cyanothieno[2,3-b]thiophene-2-carboxylate (1) was treated with a mixture of carbon disulfide and halo compounds to give the corresponding bisthiazole and bisthiolane derivatives 2-4. Treatment of compound 1 with 2,5-dimethoxytetrahydrofuran gave the corresponding 3,4-dipyrrol-1-ylthienothiophene (5). Condensation of compound 5 with hydrazine afforded the carbohydrazide derivative 6, which was treated with CS2 or PhNCS to afford oxadiazole or triazole derivatives 7a,b. The cycloaddition reaction of compound 5 with CS2 or PhNCS under phase transfer conditions gave 1,4-thiazepino- or 1,4-diazepinothieno[2,3-b]thiophenes 8 and 9, respectively. Basic hydrolysis of compound 1 yielded 3,4-diaminothieno[2,3-b]thiophene (10), which was subjected to react with different reagents to give the corresponding bispyrido- and bispyrrolothieno[2,3-b]thiophenes, and bisarylideneaminothieno[2,3-b]thiophenes 11-15, respectively.