Enoldiazosulfones undergo [3 + 3]-cycloaddition with nitrones when catalyzed by copper(I) catalysts, but not with dirhodium(II) catalysts. Under mild reaction conditions with chiral bisoxazoline ligands, copper(I) catalysts produce 1,2-oxazine-sulfone derivatives in high yields and enantioselectivities. Dirhodium(II) catalysts form stable donor−acceptor cyclopropenes that undergo uncatalyzed [3 + 2]-cycloaddition reactions with nitrones.
Adly, F. G., Marichev, K., Jensen, J., Arman, H., & Doyle, M. (2019). Enoldiazosulfones for Highly Enantioselective [3 + 3]-Cycloaddition with Nitrones Catalyzed by Copper(I) with Chiral BOX Ligands. Organic Letters, 21(1), 40-44. https://doi.org/10.1021/acs.orglett.8b03421