Cycloaddition reactions between 2-(1-cyanoallyl)thiophen and the dienophiles diethyl azodicarboxylate, N-phenylmaleimide , methyl propiolate, and dimethyl acetylenedicarboxylate are reported. Products include simple benzo[b] thiophen carboxylates (13,19) and reduced derivatives (8,9,10,12,18), as a mixture of diastereoisomers, except in the adduct with diethyl azodicarboxylate. With dimethyl acetylenedicarboxylate