AbstractThe alkylation of cyanide ion with 3‐chloromethylbenzo[b]thiophene gave a higher yield of benzo[b]thiophene‐3‐acetonitrile in dimethyl sulfoxide than in alcohol, and in addition 2‐cyano‐3‐methylbenzo[b]thiophene was obtained as a by‐product in this solvent. The abnormal product was prepared by an alternative, unequivocal synthesis. The isomers were hydrolyzed to their respective acids, which were reduced to 3+(β‐hydroxyethyl)benzo[b]thiophene and 2‐hydroxymethyl‐3‐methylbenzo[b]thiophene. The ultraviolet and nuclear magnetic resonance spectraof these