General and Regioselective Synthesis of Pyrroles via Ruthenium-Catalyzed Multicomponent Reactions

A general and highly regioselective synthesis of pyrroles via ruthenium-catalyzed three-component reactions has been developed. A variety of ketones including less reactive aryl and alkyl substrates were efficiently converted in combination with different type of amines and vicinal diols into various substituted pyrroles in reasonable to excellent isolated yields. Additionally, alpha-functionalized ketones gave synthetically interesting amido-, alkoxy-, aryloxy-, and phosphate-substituted pyrroles in a straightforward manner. The synthetic protocol proceeds in the presence of a commercially available ruthenium catalyst system and catalytic amount of base. It proceeds with high atom-efficiency and shows a broad substrate scope and functional group tolerance, making it a highly practical approach for preparation of various pyrrole derivatives.