Thienopyridone Antibacterials. Part IV[1]. Synthesis of Some N(7)- Heteroaryl-4-oxothieno[2,3-b]pyridine-5-carboxylic Acids and Esters

A series of 7-heteroaryl-4-oxo-4,7-dihydrothieno[2,3-b]-pyridine-5-carboxylic acids (8a-d) and their methyl esters (7a-d) were prepared by cyclization of the respective 2-(2,5-dichlorothien-3-yl)-3-(N-heteroarylamino)acrylates (6a-d). The latter are accessible from methyl 2-(2,5-dichlorothien-3-yl)-3-ethoxyacrylate (5) which is obtained via methyl 3-(2,5-dichlorothien-3-yl)-3-oxopropanoate(4). Of the present series, the 7-(2-thienyl) derivative (8a) exhibited good activity, especially against E. coli and Kl. pneumoniae (MIC = 2 μg / mL).