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. 2

A series of pyrazolo[1,5‐a]pyrido[3,4‐e]pyrimidin‐6‐ones was obtained by reaction of ammonium acetate with ethyl 7‐dimethylaminovinylpyrazolo[1,5‐a]pyrimidine‐6‐carboxylates and these had been prepared from ethyl 7‐methylpyrazolo[1,5‐a]pyrimidine‐6‐carboxylates by reaction with dimethylformamide dimethylacetal. Under these conditions the compounds bearing a 2‐hydroxy group were also O‐alkylated. During the preparation of the ethyl 2‐hydroxy‐7‐methyl‐3‐phenylpyrazolo[1,5‐a]pyrimidine‐6‐carboxylate the corresponding 5‐methyl isomer was isolated and identified.