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

Abstract

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.