A new method for generation of 4- and 6-aryl thieno[2,3-c]furans, and 3-aryl furo[3,4-b]pyridine

Abstract

6-Aryl thieno[2,3-c]furans 2a–c, 4-(3,4-dimethoxyphenyl)thieno[2,3-c]furan 3a, and 3-(3,4-dimethoxyphenyl)furo[3,4-b]pyridine 4a, which were intercepted in situ by dimethyl acetylenedicarboxylate to give the corresponding Diels–Alder adducts in good yields, were generated under acidic conditions from 2-(α-acetoxybenzyl)thiophene-3-carbaldehydes 5a–c, 3-(α-acetoxy-3,4-dimethoxybenzyl)thiophene-2-carbaldehyde 10a and 2-(α-acetoxy-3,4-dimethoxybenzyl)pyridine-3-carbaldehyde 12a, respectively.