Alkyl heterocycles in heterocyclic synthesis (II): Novel synthesis of isoquinoline, thiazolopyridine, and thieno[2,3-b]pyridine derivatives

Abstract

Treating 5 - (4-phenylcarboxamido)-3-cyano-4-methylpyridin-2(1H)thione (3) with elemental sulfur yielded thienopyridine 4. Compound 4 reacts with acrylonitrile to give isoquinoline 7. Compound 7 was also, prepared from 3 and methylenemalononitrile. Reaction of 3 with dimethylacetylene dicarboxylate (DMAD) gave the pyridothiazole 9. Also, 3 reacted with N,N-dimethylchloroacetamide (10) to afford compound 11 which further reacted with the reagents 12, 13 and 14 providing the thieno [2,3-b]pyridine derivatives 15, 16 and 17 respectively.