The rhodium(II)-catalyzed aziridination of olefins with {[(4-nitrophenyl)sulfonyl]imino}phenyl-λ3-iodane

The aziridination of olefins with {(4-nitrophenylsulfonyl)imino)phenyl-lambda(3)-iodane, NsN=IPh (1c), in the presence of [Rh-2(OAc)(4)] proceeds in yields of up to 85% when the olefin is used in large excess. Under optimized conditions, styrene (4a) is aziridinated with 1 equiv. of NsN=IPh (1c) in 64% yield with 2 mol% of catalyst. The aziridines derived from electron-rich olefins undergo ring-opening under the conditions of the aziridination and afford rearrangement products or pyrrolidines. The aziridination is sterospecific with 1,2-dialkyl- and 1,2-arylalkyl-disubstituted olefins, but nonstereospecific with stilbene. The rho-value for aziridination of substituted styrenes is -0.61. No ring-opened products are observed upon aziridination of vinylcyclopropanes. Tn the presence of chiral Rh-II catalysts, the aziridination is enantioselective, affording an ee of 73% with cis-beta-methylstyrene (4k) and Pirrungs [Rh-2{(R)-(-)-bnp}(4)] catalyst. The experimental results are consistent with a one-step mechanism for transfer of the nitrenoid moiety from the catalyst to the olefin.