Cyanothioacetamide in Heterocyclic Chemistry: Synthesis of Thiopyran, Pyridinethione, Thienopyridine, Pyridothienotriazine and Pyridothienopyrimidine Derivatives

Cyanothioacetamide (1) reacted with α- and β-naphthaldehyde 2a,b to afford the corresponding 3-naphthyl-2-thiocarboxamidopropenonitriles 3a,b. Compounds 3a,b structures could be elucidated via their reactions with acrylonitrile, ethyl acrylate (4a,b). N-arylmaleimides 6a-c and ethyl acetoacetate (8). The isolated products could be represented as the thiopyran, thiopyranopyrrolidine and pyridinethione derivatives 5a-d, 7a-f and 9a,b respectively. Pyridinethiones 9a,b had been used as the starting materials in the present study in addition to the next ones to synthesize several new thienopyridines, pyridothienotriazine and pyridothienopyrimidines 12a-f, 15a,b, 16b, 17-19a,b respectively through their reactions with the corresponding reagents. All structures of the newly synthesized heterocyclic compounds were established on the basis of the data of IR, 1 H NMR and elemental analyses.