Cobalt‐Catalyzed Selective Transformation of Levulinic Acid and Amines into Pyrrolidines and Pyrrolidinones using Hydrogen
Yixiao Pan, Zhenli Luo, Ji Yang, Jiahong Han, Jianbo Yang, Zhen Yao, Lijin Xu, Peng Wang, Qian Shi
Abstract
Abstract Cobalt‐catalyzed selective transformation of levulinic acid and primary amines into pyrrolidines and pyrrolidinones under H 2 has been developed. The catalyst system consisting of Co(NTf 2 ) 2 , 1,1,1‐tris(di(4‐methoxyphenyl)phosphinomethyl) ethane (( p ‐anisyl)triphos) and Me 3 SiOTf works well for the synthesis of pyrrolidines via reductive amination/cyclization/deoxygenative reduction of amide, and using Co(NTf 2 ) 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