Cobalt‐Catalyzed Selective Transformation of Levulinic Acid and Amines into Pyrrolidines and Pyrrolidinones using Hydrogen

Abstract

AbstractCobalt‐catalyzed selective transformation of levulinic acid and primary amines into pyrrolidines and pyrrolidinones under H2has been developed. The catalyst system consisting of Co(NTf2)2, 1,1,1‐tris(di(4‐methoxyphenyl)phosphinomethyl) ethane ((p‐anisyl)triphos) and Me3SiOTf works well for the synthesis of pyrrolidines via reductive amination/cyclization/deoxygenative reduction of amide, and using Co(NTf2)2/1,1,1‐tris(diphenylphosphinomethyl) ethane (triphos) as the catalyst under reduced hydrogen pressure results in exclusive formation of pyrrolidinones. Both aryl and alkyl primary amines are suitable substrates, and a variety of functional groups are tolerated. Meanwhile, 4‐oxo‐4‐arylbutanoic acids, 5‐oxohexanoic acid, 6‐oxoheptanoic acid, 2‐formylbenzoic acid, 2‐acetylbenzoic acid and 2′‐acetyl‐[1,1′‐biphenyl]‐2‐carboxylic acid are also applicable, allowing for convenient access to cyclic amines and lactams with different ring size.magnified image