Aziridination of olefins mediated by a [CuI(L1)2]+ complex via nitrene transfer reaction

Abstract

Copper-catalyzed aziridination of alkenes is dominated in the literature compared to any other metal catalysts. This catalytic reaction is believed to be mediated by the elusive Cu-nitrene intermediate. However, analytical characterization of this intermediate is extremely scarce in the literature. In this article, we intend to shed the light on the electronic structure of the Cu-nitrene intermediate. The reaction of Cu(I) salt in the presence of the redox-active bidentate Schiff base ligand (C21H20N2; L1) led us to isolate a monomeric copper(I) complex with the molecular formula of [Cu(L1)2]ClO4. 2C6H6 (1), which was structurally characterized. 1 behaves as an excellent catalyst that promotes the nitrene group transfer to the variety of alkenes in the presence of (N-(p-tolylsulfonyl)imino)phenyliodinane (PhINTs). The intermediate generated from 1 by the addition of PhINTs shows an m/z peak at 832.3079 g/mol which corresponds to an M+ ion peak of the intermediate with the molecular formula of [(L1)2CuII-NTs]+ (where Ts = Tosyl). Further, based on the detailed experimental studies (in-situ UV–Vis measurement and X-band EPR measurements) we propose that the active catalyst that possesses the copper ion in its +2 oxidation state under our experimental condition, whose electronic structure can be best described as [(L1)2CuII-NTs]+ nitrene radicals. The optimized structure of the Cu-nitrene intermediate suggests that the triplet state was found to be the ground state. Besides, we propose a mechanism for this catalytic reaction.