Non-innocent Role of the Halide Ligand in the Copper-Catalyzed Olefin Aziridination Reaction

Abstract

In the context of copper-catalyzed nitrene transfer to olefins, many systems operate upon mixing a CuX salt (X = halide, OTf) and a polydentate N-based ligand, assuming that the X ligand is displaced from the coordination sphere toward a counterion position. Herein, we demonstrated that such general assumption should be in doubt since studies carried out with the well-defined copper(I) complexes (TTM)CuCl and [(TTM)Cu-(NCMe)]PF 6 (TTM = tris(triazolyl)methane ligand) demonstrate a dual behavior from a catalytic and mechanistic point of view that exclusively depends on the presence or absence of the chloride ligand bonded to the metal center. When coordinated, the turnover-limiting step corresponds to the formation of the carbon−nitrene bond, whereas in its absence, the highest barrier corresponds to the formation of the copper−nitrene intermediate.

Nitrene-Transfer Chemistry to C–H and C═C Bonds Mediated by Triangular Coinage Metal Platforms Supported by Triply Bridging Pnictogen Elements Sb(III) and Bi(III)

“…On average, the previously explored catalyst [(TMG 3 trphen)­Cu]­(PF 6 ), featuring N amine apical coordination, is more active than the present reagents, but this may be due to its mononuclear character. Incidentally, an interesting mechanistic distinction between Cu­(I) catalysts that carry halide ligands and others that are halide-free, has been recently reported by Pérez and co-workers …”

“…Incidentally, an interesting mechanistic distinction between Cu(I) catalysts that carry halide ligands and others that are halide-free, has been recently reported by Peŕez and co-workers. 51 Hammett Plots. To start placing these reagents in a mechanistic context, Hammett plots were constructed for the competitive amination (PhINTces) of ethylbenzene versus seven para-X-ethylbenzenes (X = MeO, Me, F, Br, I, CF 3 , and NO 2 ) as mediated by catalyst 3 (5 mol % with respect to Cu) in PhCF 3 /HFIP (10:1 v/v) at 30 °C (5 h).…”

Recent advances in the accessibility, synthetic utility, and biological applications of aziridines

“…Indeed, a lot of pathways have been described by using different catalysts. 9 Among them, nickel was employed and in 2022 Wu and co-workers reported a nickel-catalyzed aminofluoroalkylative cyclization of unactive alkenes (15) with iododifluoromethyl ketones (14) to afford versatile difluoroalkylated nitrogen-containing hetorocycles including aziridines (18), as shown in Scheme 4. 10 According to the authors, the transformation proceeds through a radical mechanism.…”

“…12 After describing in 2022 the use of (NHC)M (M = Cu, Ag, Au) cores as catalysts for the olefin aziridination reaction, 13 recently, Pérez and co-workers reported the copper-catalyzed aziridination of olefins. 14 The authors highlighted the important role of the halide characterizing the copper catalyst (Scheme 7path a). Indeed, they demonstrated via mechanistic studies that the employed copper(I) complexes (TTM)CuCl (35)…”

“…After describing in 2022 the use of (NHC)M (M = Cu, Ag, Au) cores as catalysts for the olefin aziridination reaction, 13 recently, Pérez and co-workers reported the copper-catalyzed aziridination of olefins. 14 The authors highlighted the important role of the halide characterizing the copper catalyst (Scheme 7 – path a). Indeed, they demonstrated via mechanistic studies that the employed copper( i ) complexes (TTM)CuCl ( 35 ) and [(TTM)Cu-(NCMe)]PF 6 ( 36 ) (TTM = tris(triazolyl)methane ligand) possess different behaviors, from catalytic and mechanistic points of view, depending on the presence or absence of the chloride ligand bonded to the metal center.…”