Studies on heterocyclic β-enaminonitriles: Synthesis of new condensed thieno[2,3-b]pyridines containing N-heterocyclic moieties

Abstract

New versatile enaminonitrile-type building blocks, 3-aminothieno[2,3-b]pyridine-2-carbonitriles 3a,b, were synthesized from 3-cyanopyridine-2-(1H)-thiones 1a,b. Interaction of 3a,b with triethyl orthoformate furnished the corresponding ethoxymethylideneamino derivatives 6a,b. Derivatives of heterocyclic systems having the pyrazole, pyrimidine, and pyridine rings were obtained from the key precursors 3a,b and 6a, respectively.