Aerobic, enantioselective epoxidation of non-functionalized olefins catalyzed by Ni(II) chiral Schiff base complexes

Some symmetrical and non symmetrical square planar NI(II) chiral Schiff base complexes derived from 1S,2S(+)diaminocyclohexane, S(+)1,2-diaminopropane and 1R,2R(-)diphenyldiamino ethane with 3-acetyl-4-hydroxy-6-methyl-2-pyrone have been prepared. The characterization of the complexes was done by physico-chemical methods viz. microanalysis, conductance measurement, IR-, UV/visible-, H-1-, C-13{H-1}NMR, CD spectral studies, optical rotation and cyclic voltammetry. These complexes catalyses the epoxidation of non-functionalized olefins viz. 1-hexene, 1-octene, trans-4-octene and indene with molecular oxygen as terminal oxidant in presence of the sacrificial reductant. Excellent chemical yield was obtained by GC with middle and terminal longs chain alkenes than indene although the enantiomeric excess is good for indene with catalyst 3 and evaluated by H-1 NMR using chiral shift reagent Eu(hfc)(3) or by chiral capillary column on GC. (C) 1998 Elsevier Science B.V.