ChemInform Abstract: Syntheses with Heterocyclic β-Enaminonitriles: An Expeditious Synthetic Approach to Polyfunctionally Substituted 5- Phenylsulfonylthiophenes and Their Fused Derivatives

Phenylsulfonylacetophenones1 react with a mixture of elemental sulfur and malononitrile to yield the corresponding 2-amino-4-aryl-5-phenylsulfonylthiophene-3-carbonitriles2. Compound2a could be annelated to the corresponding thieno[2,3-d]pyrimidine and thieno[2,3-c]-pyrazole derivatives3 and5 upon reaction with nitrogen nucleophiles (cyanamide and hydroxylamine hydrochloride), respectively. The applicability and synthetic potency of5 to develop a facile convenient route to the polyfunctionally substituted thieno[2′,3′:3,4]pyrazolo[1,5-a]pyrimidines8, 14, 17, 20, and21 is reported. Chemical and spectroscopic evidences for the structures of the new compounds are presented.