THE FIRST HETEROBIMETALLIC MULTIFUNCTIONAL ASYMMETRIC CATALYST

摘要

The optically active lanthanum-sodium-BINOL complex (LSB), prepared from La(O-i-Pr)(3), (R)-BINOL (3 mol equiv), and NaO-t-Bu (3 mol equiv),is quite effective as an asymmetric catalyst for various Michael reactions to give adducts in up to 92% ee; X-ray crystallographic analysis of LSB shows that this catalyst consists of LaNa3C60H36O6 . 6THF . H2O, in which three BINOL molecules, three sodium atoms, and one water molecule surround; a lanthanum atom and two THF molecules coordinate to the each sodium atom. H-1-NMR study indicates the coordination of cyclohexenone, acts as a Michael acceptor, to the lanthanum atom in LSB. Furthermore, Rappe's universal force field calculation of the LSB catalyzed reaction of cyclohexenone with dimethyl malonate supports that this basic LSB complex also acts as a Lewis acid to control the direction of the carbonyl function and enhance the reactivity of the enone. This is the first example of a multifunctional heterobimetallic asymmetric catalyst (chemzyme) in which two different metals play different roles. [References: 18]