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

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.