Enantioselective Michael addition of 2-nitropropane to chalcone analogues catalyzed by chiral azacrown ethers based on α-d-glucose and d-mannitol

Abstract The chiral monoaza-15-crown-5 type lariat ethers 1 and 2 derived from α- d -glucose and from d -mannitol, respectively, have been applied as phase transfer catalysts in the enantioselective Michael addition of 2-nitropropane to aromatic 3b – c and heteroaromatic 3d – h chalcone analogues. Among the catalysts, the glucose-based 1c with a phosphinoxidobutyl side arm proved to be the most effective, it inducing 34% e.e. for 4b , 59% e.e. for 4c , 80% e.e. for 4d , 64% e.e. for 4e , 17% e.e. for 4f . Catalyst 1a having 3-hydroxypropyl substituent resulted in 81% e.e. for compound 4g . The formation of the (+)-( S )-enantiomer of 4 was preferred using crown ethers 1a – c , while the (−)-( R )-enantiomer was in excess with catalyst 2 . The absolute configuration of the Michael adduct 4d was determined by single-crystal X-ray analysis.