Ruthenium-Catalyzed Direct Synthesis of Semisaturated Bicyclic Pyrimidines via Selective Transfer Hydrogenation

A new ruthenium-catalyzed direct and selective synthesis of semisaturated bicyclic pyrimidines, from α-aminopyridyl alcohols and nitriles, has been demonstrated. The synthesis proceeds with an easily available catalyst system, broad substrate scope, excellent functional tolerance, and no need for high pressure H₂ gas. Control experiments indicate that the reaction proceeds via successive dehydrogenative annulation and transfer hydrogenation of the less electrophilic pyridyl nucleus, and the density functional theory (DFT) study reveals the origin of such a unique selectivity.