Catalytic asymmetric 1,3-dipolar cycloaddition of nitrones to alkylidene malonates: Highly enantioselective synthesis of multisubstituted isoxazolidines

摘要

All under control! A catalytic asymmetric 1,3-dipolar cycloaddition reaction of nitrones to alkylidene malonates, catalyzed by chiral N,N'-dioxide-Ni(ClO_4)_2.6 H_2O complexes, has been developed with excellent yields, diastereo-, and enantioselectivities (see scheme, R~1=aryl, R~2=alkyl, R~3, R ~4=Ph). In addition, a possible transition state has also been proposed to elucidate the high level of enantio- and diastereocontrol.