A NEW AND HIGHLY EFFICIENT ASYMMETRIC ROUTE TO CYCLIC ALPHA-AMINO PHOSPHONATES - THE FIRST CATALYTIC ENANTIOSELECTIVE HYDROPHOSPHONYLATION OF CYCLIC IMINES CATALYZED BY CHIRAL HETEROBIMETALLIC LANTHANOID COMPLEXES

The catalytic and enantioselective hydrophosphonylation of cyclic imin es is described for the first time. In addition, we have uncovered a n ew and highly efficient asymmetric approach to cyclic cc-amino phospho nates using thiazolines as the imine model component. The desired phar maceutically interesting phosphonates 5a-e could be synthesized by a h eterobimetallic (R)-LnPB-catalyzed (Ln = lanthanoid metal, P = potassi um, B = (R)=binaphthol) hydrophosphonylation of the C=N double bond wi th up to 98% enantiomeric excess and up to 98% chemical yield. Using o ther types of organometallic catalysts (titanium-(IV) complexes), the reaction proceeds with modest enantioselectivity. A detailed investiga tion concerning the dependence of enantioselectivity and chemical yiel d, respectively, on a series of reaction parameters (e.g.; lanthanoid and alkali metal, solvent, reaction temperature, pressure, and catalyt ic amount) is reported. An optimized catalytic lanthanoid system ''(R) -YbPB (5 mol %)/50 degrees C/48 h/THF-toluene (1:7)'' was found. The c atalytically active complex was isolated and analyzed by spectroscopic methods. In addition, P-31 and H-1 NMR spectroscopic and LDI-TOF mass spectrometric investigations were carried out to support a postulated mechanistic course for this (R)-LnPB-complex-catalyzed hydrophosphony lation reaction.