CHEMISTRY OF SUBSTITUTED PYRAZOLO[1,5-A]PYRIMIDINES .4. A STRUCTURAL CORRECTION OF A SERIES OF PYRAZOLO[5',1'-2,3]PYRIMIDO[5,4-D][1,2]DIAZEPINES ON THE BASIS OF NMR-SPECTROSCOPY AND X-RAY-DIFFRACTION ANALYSIS

The reaction of a series of 7-(2-dimethylaminovinyl)pyrazolo[1,5-a]pyr imidines 3 with hydrazine hydrate has been re-investigated and the nat ure of the reaction product unambiguously established on the basis of both NMR spectroscopy and X-ray diffraction. Methyl-6-(pyrazol-3'-yl)p yrazolo[1,5-a]pyrimidines 1 and not, as formerly claimed, pyrazolo[5', 1':2,3]pyrimido-[5,4-d][1,2]diazepines 2 are shown to be the final pro ducts in the reaction of compounds 3 with hydrazine hydrate. The struc tures of compounds 1 have been rationalised on the basis of some diagn ostic coupling constants' values and confirmed by the X-ray structure of imethyl-6-(pyrazol-3'-yl)pyrazolo[1,5-a]pyrimidine 1b. The literatu re assignments for the quaternary carbon resonances have been revised and the signals unambiguously attributed by means of 2D experiments.