Concise and Efficient Access to 5,7‐Disubstituted Pyrazolo[1,5‐a]pyrimidines by Pd‐Catalyzed Sequential Arylation, Alkynylation and SNAr Reaction

A simple and efficient method for synthesis of 5,7‐disubstituted pyrazolo[1,5‐a]pyrimidines is reported. The synthetic route involved first a one‐pot two‐step synthesis of 7‐substituted pyrazolo[1,5‐a]pyrimidin‐5‐ones from the reaction of 3‐aminopyrazole 1 with activated alkynes. These compounds were used as key intermediates to access, with excellent yields, a library of new 5,7‐disubstituted pyrazolo[1,5‐a]pyrimidines, which are known for their wide range of biological activities, through C–O bond activation with PyBroP (bromotripyrrolidinophosphonium hexafluorophosphate) as an activator reagent.