Synthesis of 7-(2-dimethylaminovinyl) derivatives of pyrazolo[1,5-a]pyrimidines, as precursors of new tricyclic series. Binding studies of BDZ receptor

A series of 7-dimethylaminovinylpyrazolo[1,5-a]pyrimidines bearing an acetyl or an ethoxycarbonyl group at the 6-position turned out to be useful intermediates for the synthesis of pyrazolo[1,5-a]pyrido[3,4-e]pyrimidines and 8H-pyrazolo[5',1':2,3]pyrimido[5,4-d][1,2]diazepines. These tricyclic derivatives were studied for their affinity for the central benzodiazepine receptor, and meaningful suggestions about the structure-affinity relationship were obtained. Some of the above intermediates were also reacted with S-methylthiourea, to give a mixture of pyrazolo[5',1':1,2]pyrimido[5,6-e][1,3]diazocines and pyrazolo[1,5-a]quinazolines.