Catalytic Asymmetric Cycloaddition Reaction of Alkenyl Trichloroacetates with Nitrones

A catalytic enantioselective cycloaddition reaction of alkenyl trichloroacetates with nitrones was achieved using an (S)-BINOL-derived chiral tin dibromide possessing a 4-trifluoromethylphenyl group at 3- and 3'-positions as the chiral precatalyst in the presence of sodium ethoxide, sodium iodide, and ethanol. Optically active isoxazolidines with up to 95% ee were diastereoselectively obtained in high yields even from aliphatic aldehyde derived nitrones under the influence of the in situ generated chiral tin ethoxide iodide.