Synthesis and characterization of a chiral Zn(II) complex based on a trans-1,2-diaminocyclohexane derivative and catalytic reduction of acetophenone

Reaction of ZnCl2 with R,R-bmbcd (= N,N'-bis(4-methoxy-benzyl)-cyclohexane-1,2-diamine) I in ethanol yields the chiral [ZnCl2(R,R-bmbcd)] 2, which crystallizes in the monoclinic space group P2(1). The Zn atom has a distorted tetrahedral geometry involving two nitrogen atoms of R, R-bmbcd and two chloro ligands with the range of bond lengths, 2.066(2)-2.2289(9) Angstrom. The result of the catalytic enantioselective reduction of acetophenone promoted by R-1 R-bmbcd:Zn(OTf)(2) = 1:1 mole ratio in the presence of catecholborane for 48 h at 0 degreesC give (S)-(-)-1-phenylethanol in 48% ee with 77% yield. (C) 2004 Elsevier Ltd. All rights reserved.