Pyrazolo[1,5‐a]Pyrimidine Derivative as Precursor for Some Novel Pyrazolo[1,5‐a]Pyrimidines and Tetraheterocyclic Compounds

The 2‐(cyanomethyl)‐5,7‐dimethylpyrazolo1,5‐a ]pyrimidine‐3‐carbonitrile 3 reacted with phenyl isothiocyanate to afford the respective thioanilide derivative 4 that is a novel compound that has been unreported hitherto. The latter was used as a precursor to synthesize several novel polyheterocyclic compounds 9 , 12 , 15 , and 19 . Treatment of the enamine derivative of compound 3 with each of hydrazine hydrate and hydroxylamine hydrochloride yielded the tetraheterocyclic compounds 22 and 23 , respectively. The structures of all the newly synthesized compounds were confirmed on basis of their elemental, spectral data, and plausible mechanism has been postulated to account for their formation. X‐ray crystallography was carried out as a further evidence for the structure of the isolated product 19 .