The rhodium(II)-catalyzed aziridination of olefins with {[(4-nitrophenyl)sulfonyl]imino}phenyl-lambda³-iodane

Abstract

The aziridination of olefins with {(4-nitrophenylsulfonyl)imino}phenyl-λ 3 -iodane, NsNTIPh (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 NsNTIPh (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 ρ-value for aziridination of substituted styrenes is -0.61. No ring-opened products are observed upon aziridination of vinylcyclopropanes. In the presence of chiral Rh II catalysts, the aziridination is enantioselective, affording an ee of 73% with cis-β-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.

A Mechanistic Study of the Stereochemical Outcomes of Rhodium‐Catalysed Styrene Aziridinations

“…asc.wiley-vch.de results obtained by Müller and co-workers: [30] stereospecific rhodium-catalysed aziridination was observed with alkyl-and alkyl-aryl-substituted alkenes, but not with stilbene. One can hypothesizes a radical pathway with the later, where as a spin intersystem crossing process might be operational for the other substrates.…”

Asymmetric Nitrene Transfer Reactions: Sulfimidation, Aziridination and C–H Amination Using Azide Compounds as Nitrene Precursors

“…In 1996, Müller et al. reported the first asymmetric nitrene C–H bond amination using chiral rhodium(II) dimer complexes 8 as the catalyst, albeit with modest enantioselectivity . We found that manganese–salen complex 9 having bromo substituents was a good catalyst for intermolecular benzylic and allylic C–H amination .…”

Spin‐Selective Generation of Triplet Nitrenes: Olefin Aziridination through Visible‐Light Photosensitization of Azidoformates

“…This reaction resulted in the scrambling of the cyclopropane stereochemistry in the aziridinated products ( 30 ), a result that is only consistent with the reversible ring fragmentation of a cyclopropyl carbinyl radical intermediate. 23 Finally, we considered the possibility that the aziridination was not proceeding via a nitrene intermediate but rather by a [3+2] cycloaddition of the carbamoyl azide followed by a photocatalytic decomposition of a 1,2,3-triazoline intermediate. 24 To test this hypothesis, we prepared norbornene-derived triazoline 31 and irradiated it for 4 h in the presence and absence of 1c (Scheme 3C).…”