Reactivity of 7‐(2‐dimethylaminovinyl)pyrazolo[1,5‐ a ]pyrimidines: Synthesis of pyrazolo[1,5‐ a ]pyrido[3,4‐ e ]pyrimidine derivatives as potential benzodiazepine receptor ligands. 1

A series of 7‐methylpyrazolo[1,5‐ a ]pyrimidines were reacted with dimethylformamide dimethylacetal to give the corresponding dimethylaminovinyl derivatives. These were reacted with ammonium acetate affording, through a ring closure, a number of 6‐methylpyrazolo[1,5‐ a ]pyrido[3,4‐ e ]pyrimidines bearing various substituents on the pyrazole ring. The 6‐acetyl‐2‐hydroxy‐7‐methylpyrazolo[1,5‐ a ]pyrimidine was used as starting material for obtaining some O ‐alkyl derivatives. Catalytic transfer hydrogenation of 2‐benzyloxy‐6‐methylpyrazolo[1,5‐ a ]pyrido[3,4‐ e ]pyrimidine led to the 2‐hydroxy derivative.