2-(2-Benzimidazolyl)pyridine Mn(I) Complexes: Synthesis and Exploration of Catalytic Activity toward Synthesis of Pyrimidine and Quinoline

A series of phosphine-free benzimidazole and pyridine-containing bidentate Mn(I) complexes were synthesized. Among them, Mn1 complex bearing a proton-responsive 2-hydroxypyridine-appended benzimidazole ligand was found to be highly effective for the synthesis of different N-heterocycles utilizing alcohols. Employing significantly lower catalyst loading (0.05 mol %), several substituted pyrimidines and quinolines were effectively synthesized. The lactim–lactam acid–base equilibrium of the 2-hydroxypyridine fragment, role of the countercation of the base, and effect of the externally added ligands were investigated. A probable catalytic cycle was proposed based on the basis of various control experiments and different kinetic studies.