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

Article abstract of DOI:10.1007/BF00807600

Phenylsulfonylacetophenones 1 react with a mixture of elemental sulfur and malononitrile to yield the corresponding 2-amino-4-aryl-5-phenylsulfonylthiophene-3-carbonitriles 2. Compound 2a could be annelated to the corresponding thieno[2,3-d]pyrimidine and thieno[2,3-c]-pyrazole derivatives 3 and 5 upon reaction with nitrogen nucleophiles (cyanamide and hydroxylamine hydrochloride), respectively. The applicability and synthetic potency of 5 to develop a facile convenient route to the polyfunctionally substituted thieno[2′,3′ : 3, 4]pyrazolo[1,5-a]pyrimidines 8, 14, 17, 20, and 21 is reported. Chemical and spectroscopic evidences for the structures of the new compounds are presented.