Facile synthesis of 4-alkyl (and aryl)-2-aryl-6-diazo-4h- thieno[3,2-b]pyridine-5,7-diones.

Abstract

Treatment of 3-[3-alkyl (and aryl)amino-5-arylthieno-2-yl]-2-diazo-3-oxopropanoates 8 with TMSOTf (3 equiv) in the presence of Et(3)N (6 equiv) in CH(2)Cl(2) for 1 h at room temperature afforded 4-alkyl (and aryl)-2-aryl-6-diazo-4H-thieno[3,2-b]pyridine-5,7-diones 14 in excellent yields. On heating of 14 in the presence of a catalytic amount of Rh(2)(CF(3)CF(2)CF(2)CO(2))(4) in PhH for 4-10 h at reflux, corresponding ring contraction products, 4-alkyl (and aryl)-5,6-dihydro-4H-thieno[3,2-b]pyrrol-5-ones 16, were produced in good to excellent yields.