Facile Palladium-Catalyzed Synthesis of 3-Arylpyrazolo-[1,5-a]pyrimidines

Abstract

An efficient palladium-catalyzed synthesis of 3-arylpyrazolo[1,5-a] pyrimidines has been investigated. The key step in the synthesis is a Suzuki biaryl coupling of 3-bromo-2,5-dimethyl-7-aminopyrazolo[1,5-a]pyrimidines with arylboronic acids to provide 3-arylpyrazolo[1,5-a]pyrimidines in moderate to good yield. The synthetic utility of this methodology has been demonstrated by a concise and convergent synthesis of R121920, a potent CRHR1 antagonist recently undergoing clinical evaluations.