THE ANNELATION OF THE 2-AMINOPYRAN-4-ONE RING TO CONDENSED THIOPHENES

The reaction of arylacetonitriles with the methyl ester of 3-hydroxybenzo[b]thiophene-2-carboxylic acid in the presence of a basic catalyst leads to the previously unreported 2-amino-3-arylbenzo[4,5]thieno[3,2-b]pyran-4-ones. Under the same conditions, the ethyl ester of 4,6-dimethyl-3-hydroxythieno[3,2-c]pyridine-2-carboxylic acid reacts to form derivatives of a new heterocyclic system, pyrano[2′,3′-4,5]-thieno[3,2-c]pyridine.