ASYMMETRIC DIPOLAR CYCLOADDITION OF NITRILE OXIDES TO THE ALPHA,BETA-UNSATURATED ESTERS BEARING AN IMIDAZOLIDINE CHIRAL CONTROLLER AT THE BETA-POSITION

Some alpha,beta-unsaturated esters bearing an imidazolidine chiral controller at the beta-position were employed in the asymmetric cycloaddition to nitrile oxides. Regio- and diastereoselectivities were both poor when the chiral controller was a perhydropyrrolo[1,2-c]imidazol-3-yl auxiliary, while the reaction of the esters bearing a C2-symmetric imidazolidine chiral controller was exclusively regioselective or diastereoselective depending upon the nature of N-substituent. The transition state was briefly discussed.