Molybdenum Catalyzed Acceptorless Dehydrogenation of Alcohols for the Synthesis of Quinolines

The first molybdenum triazolylidene complexes catalyzing the atom-economical synthesis of quinolines through acceptorless dehydrogenative coupling of alcohols is reported. A new family of Mo(0) complexes bearing chelating bis-1,2,3-triazolylidene, pyridyl-1,2,3-triazolylidene, and bis-triazole ligands have been prepared and applied as catalysts for the synthesis of quinolines. Interestingly, Mo complexes bearing bis-1,2,3-triazolylidene ligands with alkyl groups (Et, n-Bu) displayed superior catalytic activities than those containing aryl substituents on the triazolylidene rings. Control experiments corroborated that the catalytic reaction involves the dehydrogenation pathway. Molybdenum triazolylidene complexes displayed excellent catalytic activity in the synthesis of a wide variety of quinolines through acceptorless dehydrogenative coupling reactions. image