Concise and Efficient Access to 5,7-Disubstituted Pyrazolo[1,5-a]pyrimidines by Pd-Catalyzed Sequential Arylation, Alkynylation and SN_(Ar) Reaction

摘要

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.