Synthesis of Phenanthrothiazoles and 1,2-Di(heteroaryl)benzenes through Successive Pd-Catalyzed Direct Arylations.

Palladium-catalyzed direct arylation of 4-(2-bromophenyl)-2-methylthiazole proceeds with high efficiency at the thiazolyl C5 position using aryl bromides as the aryl source. This transformation provides simple access to 4-(2-bromophenyl)-2-methyl-5-arylthiazoles, which can be further converted into phenanthrothiazoles via palladium-catalyzed intramolecular direct arylation. When the direct arylation of 4-(2-bromophenyl)-2-methyl-5-arylthiazoles is conducted in the presence of an external heteroarene such as thiazoles, thiophenes, or imidazo[1,2-a]pyridines, the intermolecular arylation of such external heteroarenes proceeds faster than the intramolecular reaction, allowing the formation of 1,2-di(heteroaryl)benzene derivatives.