Synthesis and structures of copper complexes bearing unsymmetric derivatives of (R,R)‐1,2‐diaminocyclohexane: An efficient catalyst for asymmetric Henry reaction

Abstract

A series of Cu (II) complexes bearing asymmetric derivatives of (R,R)‐1,2‐diaminocyclohexane were synthesised and characterised. The X‐ray structures of the complexes showed distorted square planar geometry. The catalytic activities of in situ‐generated copper acetate complexes in the presence of 10 mol% of N,N‐diisopropylethylamine were evaluated in the asymmetric Henry reaction. The current catalysts showed high enantioselectivity (up to 99%) for (S)‐1‐nitro‐4‐phenylbutan‐2‐ol from the reaction of 3‐phenylpropanal and nitromethane.

(3S,4S)‐N‐substituted‐3,4‐dihydroxypyrrolidines as ligands for the enantioselective Henry reaction

“…The use of polar and apolar solvents is mentioned in the literature, although polar protic solvents such as alcohols usually give better conversions and er . [ 43–46 ] Therefore, several alcohols were tested as solvents for the reaction and conversions higher than 96% were obtained in all cases. However, low er resulted with all the alcohols tested.…”