Improved access to thiazolo[5,4-d]thiazole and thieno[2,3-d]thiazole

Abstract

Five-membered rings are of interest as building blocks for nonlinear optical (NLO) materials. We found easy access to the title compounds: thiazolo[5,4-d]thiazole 1 has been obtained in three simple steps starting with the chlorination of ethyl isothiocyanatoacetate 8, followed by dehydrohalogenation to the diethyl 2,5-dicarboxylate of 1, which yielded 1 after saponification and decarboxylation. Thieno[2,3-d]thiazole 2 has been synthesized in two steps by reductive deamination of the easily available 2-aminothieno[2,3-d]thiazole 5.