Application of asymmetric Henry reaction by copper(II) complexes containing (R,R)-1,2-diaminocyclohexane with naphthyl and thiophenyl substituents

Abstract

A series of Cu(II) complexes containing C1-symmetric thiophene derivatives of (1R,2R)-N1-(naphthalen-2-ylmethyl)cyclohexane-1,2-diamine, namely L1, L2 and L3 were synthesized and characterized. These complexes had distorted square-planar geometries around the Cu(II) center. High yield (99%) and excellent enantioselectivity (>99%) for (S)‐1‐nitro‐4‐phenylbutan‐2‐ol from the reaction of 3‐phenylpropanal and nitromethane was obtained using [L1Cu(OAc)2] or [L3Cu(OAc)2] with 10 mol% of diisopropylethylamine (DIPEA) within 24 h. The catalytic systems also demonstrated good activity and moderate to high enantioselectivity for aliphatic aldehydes.