Metal-free oxidative cyclization of acetophenones with diamines: a facile access to phenylpyridines.

An efficient metal-free access to 2- and 3-phenylpyridines via oxidative coupling of acetophenones or phenylacetones with 1,3-diaminopropane has been described. The reaction involves shorter reaction time, excellent yields and a broad substrate scope. The reaction proceeds via the formation of imine, which further undergoes oxidative C-N bond cleavage, C-C bond formation and oxidation to give a pyridine skeleton. The quantum chemical calculations identified the transition state for the reaction and helped in tracing the reaction mechanism.