Efficient Methods for the Synthesis of Thieno(3,2-b)thiophene and Thieno(3,2-b)furan Derivatives

摘要

A novel approach to the synthesis of thieno[3,2-b] thiophenes and thieno[3,2-b]furans bearing various substituents from readily accessible starting materials has been developed. The methodology is based on C- and O-alkylation of ethyl 4-hydroxy-2-methylthiophene-3-carboxylate with a-halo ketones, followed by cyclization. A great interest has been concentrated on thieno[3,2-b]thiophene and thieno[3,2-b]furan derivatives, because of both their biological activity and their potential elec-trooptical properties for use as molecular devices. These compounds could be used as aryl residues for di-hetarylethenes that possess good photochromic properties; however, research in this area has been impeded by the lack of efficient synthetic routes to thieno[3,2-b]thiophene and thieno[3,2-b]furan derivatives.