A Facile One-Pot Synthesis of Substituted Thieno[2,3-b]pyridines from Enaminones.

A facile and efficient one-pot synthesis of substituted thieno[2,3-b]pyridines has been developed. Treatment of enaminones, such as 2-acetyl-3-(dimethylamino)propenamides and -propenoates, with 2-cyanothioacetamide in the presence of potassium carbonate in N,N-dimethylformamide at 80 °C followed by addition of methylene-active bromides at room temperature provided, via intramolecular cyclization, 2,3,5,6-tetrasubstituted thieno[2,3-b]pyridines in yields of 78-90%. This protocol, which combines construction and modification of the thieno[2,3-b]pyridine ring, increases the structural diversity of the final products from readily available materials. [ABSTRACT FROM AUTHOR]