Regiodivergence in the Cycloadditions between a Cyclic Nitrone and Carbonyl-Type Dipolarophiles

The present report details the 1,3-dipolar cycloaddition between a chiral cyclic nitrone (1) and different carbonyl-type dipolarophiles, thus confirming the regiodivergence observed due to the cyclic nature of the dipolarophile source. An ortho regioselectivity is observed in the resulting isoxazolidines when the dipolarophile is acyclic, whereas the meta adducts are obtained from the cyclic dipolarophiles. This evidence is supported by both electronic calculations and X-ray diffraction.