New pharmacologically active 2-phenylpyrazolo [1,5-a]pyrimidines.

2-Phenylpryrazolo [1,5-a]pyrimidine (I) 4,7-dihydro-2-phenylpyrazolo [1,5-a]pyrimidin-7-one (II) and 4,5-dihydro-2-phenylpyrazolo [1,5-a]pyrimidin-5-one (III) are prepared. Because of the interesting antipyretic, hypothermizing and anti-inflammatory properties of some of their derivatives, the above mentioned compounds are used as reference compounds in a Q.S.A.R. study still in progress. Methylation of (II) and (III) with (CH3)2SO4 and CH2N2 gives methylderivatives whose structure is determined by spectroscopic means.