In view of the antitumor activity reported for 7, 8-dimethylbenzo [b] azepine-2, 5-dione, new isosteric thieno [2, 3-b]-azepin-4-ones have been prepared by a Dieckmann ring closure reaction. Substituted 2-amino-3-carbethoxythiophenes were tosylated, or benzoylated, and the corresponding sodium salt was alkylated with ethyl 4-bromobutyrate. The resulting product was cyclized in the presence of sodium hydride, and the azepinones were ...