Synthesis of 3-amino-4,5-dihydro(5H)4-oxothieno[3,2-c]quinoline-2-carboxylic acids and their alkyl esters

4-Hydroxyquinolin-2(H)ones are converted to 4-chloro-3-cyanoquinolin-2(H)ones and are cyclised with thioglycolic acid and its alkyl esters to furnish the title compounds viz. 3-amino-4,5-dihydro(5H)4-oxothieno[3,2-c]quinoline-2-carboxylic acids and their corresponding alkyl esters, which are characterised by elemental analysis and spectral data.