Synthesis of Amide and Ester Derivatives of Naphthopyrone Carboxylic Acid

The synthesis of various amide and ester derivatives of naphthopyrone‐2‐carboxylic acid has been carried out by reaction of 1‐naphthol with dimethyl acetylenedicarboxylate, which gave a mixture of E and Z isomers of naphthoxy diester. The diester on hydrolysis with KOH gave corresponding diacid, which was a mixture of E and Z isomers. The E and Z isomers were difficult to separate, which were subjected to cyclization in sulfuric acid to get cyclized naphthopyrone carboxylic acid. This acid is converted into titled compounds.