Visible-Light Promoted Selective Imination of Unactivated C–H Bonds via Copper-nitrene Intermediates for the Synthesis of 2H-Azirines

Abstract

A novel strategy to trap iminyl radicals with copper ions has been developed at room temperature, the resulted high-valent Cu­(III) imine intermediate resets quickly to form nitrene and then to furnish a 2H-azirine. This protocol with dual copper/photoredox catalyst enables the selective imination of unactivated C–H bonds under mild conditions with a broader scope. Moreover, this method also uncovers a novel ring-expansion rearrangement from cyclobutyl oxime derivatives to give the α-acylamino cyclopentanones.

Iminyl-Radical-Mediated Formation of Covalent Au–N Bonds for Molecular Junctions

“…Given these unique reactivities, we propose that, in our case, the free iminyl radicals undergo direct Au–N bonding reactions with Au electrodes, thus enabling the formation of single-molecule junctions. Note that, as suggested by previous studies, the reactions between N-centered radicals and transition metals may form covalent metal-N bonds by quenching the radicals . It is also possible that the radical binds to the metal surface via the N lone pair and produces a metal-bound radical intermediate .…”

Oxime‐Derived Iminyl Radicals in Selective Processes of Hydrogen Atom Transfer and Addition to Carbon‐Carbon π‐Bonds

“…Azirines 218 were synthesized by the irradiation of oxime esters 217 with blue light in the presence of the fac ‐Ir(ppy) 3 /CuBr catalytic system (Scheme 84). [156] The authors suggested that at the first stage of the reaction, the one‐electron reduction of oxime ester 217 by fac ‐Ir(ppy) 3 occurs with the formation of the iminyl radical. The latter is intercepted by Cu I .…”

Photoredox/copper cocatalyzed domino cyclization of oxime esters with TMSCN: access to antifungal active tetrasubstituted pyrazines

“…Based on the clues from our mechanistic investigations 23 and previous reports, a plausible reaction mechanism was depicted in Scheme 5. Initially, the excited Ir(III) catalyst (E 1/2 (Ir(III)*/Ir(IV)) = À1.73 V vs. SCE) 24 would be able to conduct a SET reduction of 1a (E red (1a/1a À ) = À1.78 V vs. SCE) (see the ESI † for details) to release the nitrogen-centered radical A, [9][10][11]19,25 which is trapped by Cu(I) to yield imino-Cu(II) complex B. The subsequent isomerization of B gives Cu(II) intermediate C. 17b-d,13b Concurrently, the cyano radical species, generated from the reaction of the Cu(II) salt and TMSCN, delivers dicyano-substituted iminyl radical E and Cu(I).…”

“…Therein, functionalized ketones 10 can be straightforwardly synthesized from oxime esters. In addition, diverse three- and five-membered nitrogen-containing heterocycles, including 2 H -azirines, 11 pyrroles, 12 pyrazoles, 13 oxazoles, 14 thiazoles, 15 and imidazoles, 16 have been efficiently constructed. The elegant syntheses of six-membered heterocycles such as pyridines, 17 quinolines, 18 phenanthridines, 19 and pyrimidines 20 have also been achieved (Scheme 1a).…”