Abstract Several new pyrazolo[1,5‐ a ]pyrimidines were obtained from the reaction of 1 H ‐5‐amino‐3‐phenylpyrazole ( 1 ) with β‐dimethylaminopropiophenones 2 in pyridine. The structure elucidation of 6,7‐dihydropyrazolo[1,5‐ a ]pyrimidines 3 is based on nmr measurements. These compounds showed moderate anthelmintic in vitro activity against the Nipposirongylus brasiliensis model.