HIGHLY ENANTIOSELECTIVE SYNTHESIS OF 1,3-OXAZOLIDIN-2-IMINE DERIVATIVES BY ASYMMETRIC CYCLOADDITION REACTIONS OF VINYLOXIRANES WITH UNSYMMETRICAL CARBODIIMIDES CATALYZED BY PALLADIUM(0) COMPLEXES

4-Vinyl-1,3-oxazoilidin-2-imine derivatives have been synthesized by c ycloaddition reactions of 2-vinyloxiranes with unsymmetrical carbodiim ides catalyzed by palladium(0) complexes-in excellent total isolated y ields. After reaction two compounds were always formed, one of which w as isolated as the major product. A bulky alkyl group on one of the ni trogen atoms of the carbodiimide enhanced the product ratio in favor o f the N-aryl-3-alkyl-1,3-oxazolidin-2-imine. Highly enantioselective c ycloadducts (up to >99% ee) were formed by using TolBINAP as the chira l phosphine ligand, in THF at ambient temperatures. The enantiodetermi nation is believed to be dependent on nucleophilic attack of the anion ic nitrogen of the carbodiimide due to the steric interaction of the c arbodiimide substituents with the chiral phosphine ligand.