Synthesis and X-ray structure of a Cu(II) complex of N,N′-bis(2-pyridylmethylidene)-(R,R)-1,2-diaminocyclohexane and its catalytic application for asymmetric Henry reaction

The reaction of NN-bis(2-pyridylmethylidene)-(R,R)-1,2-diaminocyclohexane (L) with Cu(ClO4)(2) center dot 6H(2)O was carried out and resulted in the formation of a new chiral tetradentate Cu(II) complex. The structure of Cu(L)(NCCH3)(ClO4)(2) was determined by X-ray diffraction method. This result revealed that Cu2+ ion in the complex was coordinated by four nitrogen atoms of the chiral Schiff base ligand and one nitrogen atom of NCCH3 in a distorted trigonal bipyramid geometry. The yields of asymmetric Henry reaction between benzaldehyde and nitromethane in the presence of triethylamine or diiospropylethylamine by using the complex as a catalyst were high (>= 94%), however, the enantiomeric excesses were not (ca. 30%). (C) 2005 Elsevier Ltd. All rights reserved.