RECENT PROGRESS OF NEW CATALYTIC SYNTHETIC METHODS FOR NITROGEN HETEROCYCLES BASED ON HYDROGEN TRANSFER REACTIONS

This review summarizes a variety of synthetic methods for nitrogen heterocycles based on hydrogen transfer reactions catalyzed by transition metals in a past decade. Most of them employ iridium and ruthenium complexes as the catalysts and provide a versatile and environmentally benign synthetic methodology of various nitrogen heterocyclic compounds. Intermolecular cyclization reactions of amines with alcohols afford 5-7 membered alicyclic amines, quinolines, piperazines, indoles, quinoxalines, pyrroles, benzimidazoles, and benzoxazoles. Intramolecular cyclization reactions of amino alcohols give indoles, 1,2,3,4-tetrahydroqunolines, I,2,3,4-tetrahydroquinoxalines, 3,4-dihydro-2(1H)-quinolinones, and oxindoles. Friedlander-type cyclization reactions provide a convenient route to various quinolines. Finally, cyclization reactions of amines with amines afford quinolines and phenylpyrrolidines.