Direct C-H bond (Hetero)arylation of thiazole derivatives at 5-position catalyzed by N-heterocyclic carbene palladium complexes at low catalyst loadings under aerobic conditions

A highly efficient and practical protocol has been developed for the synthesis of 5-(hetero)arylated thiazole derivatives via an N-heterocyclic carbene palladium (Pd-NHC) complex catalyzed direct C-H arylation reaction. Utilization of this methodology, the arylation of substituted thiazoles with (hetero)aryl bromides efficiently proceeded at low catalyst loading (0.1–0.05 mol%) and under aerobic conditions. A variety of (hetero)aryl bromides, even some strongly deactivated or highly congested (hetero)aryl bromides, with a broad range of functional groups were compatible under the optimal reaction conditions. In all cases, the target products were afforded in moderate to quantitative yields.