Palladium-Catalyzed Intramolecular Cross-Dehydrogenative Coupling: Synthesis of Fused Imidazo[1,2‑<i>a</i>]pyrimidines and Pyrazolo[1,5‑<i>a</i>]pyrimidines

A palladium-catalyzed intramolecular dehydrogenative coupling reaction was developed for the synthesis of fused imidazo­[1,2-a]­pyrimidines and pyrazolo­[1,5-a]­pyrimidines. The developed protocol provides a practical approach for the synthesis of biologically important substituted pyrimidines from easily available substrates, with a broad substrate scope under mild reaction conditions.