Synthesis of Thiazolinone, Aminopyrazole, Pyrazolopyrimidine, and Pyrazolotriazine Derivatives Starting from 1-Naphthyl-2-Cyanoacetamide

Efficient and suitable methods for the synthesis of novel class of simple and fused heterocyclic compounds were prepared starting with 1-naphthyl-2-cyanoacetamide and commercially available reagents. The cyclocondensation of 1-naphthyl-2-cyanoacetamide with sulfanylacetic acid furnished phenylthiazolinone derivative. Stirring of the starting compound with PhNCS afforded thiocarbamoyl derivative which underwent heterocyclization with chloroacetyl chloride to give thiazolinone derivative. 5-Aminopyrazole derivative was prepared by following mild procedures via refluxing the last thiocarbamoyl with hydrazine hydrate. Different synthetic approaches were discussed to obtain the novel fused pyrazolo[1,5-a]pyrimidine, 4H-pyrazolo[3,4-d]pyrimidin-4-one moieties involving the reaction of the prepared 5-aminopyrazole with a) 1, 3-dielectrophilic centers (acetylacetone, acetoacetanilide), b) arylidines of malononitrile, and c) isothiocyanate derivatives. The action of iced sodium nitrite solution in acidic medium on the last 5-aminopyrazole gave pyrazolo[3,4-d][1,2,3]triazine. All novel structure were elucidated by different spectroscopic data (IR, MS, 1H, and 13C NMR) and elemental analysis.