Recent advances in combining photo- and N-heterocyclic carbene catalysis

Abstract

This review summarizes recent advances in combining photo- and N-heterocyclic carbene catalysis, as well as provides an outlook on future opportunities and challenges.

Visible Light-Mediated Monofluoromethylation/Acylation of Olefins by Dual Organo-Catalysis

“…On the other hand, stemming from the groundbreaking contributions of Studer [ 37 , 38 ], Ohmiya [ 39 , 40 ], and Chi [ 41 ] et al, NHC-attached persistent Breslow intermediate radicals (BIR) [ 42 , 43 , 44 ] have emerged as valuable acyl radical equivalents, enabling radical-radical cross-coupling and thereby paving the way for a new paradigm in radical acylation chemistry [ 45 , 46 , 47 , 48 ]. In radical NHC catalysis, persistent BIR and transient radical species can be concurrently generated at a comparable rate through a single electron transfer process.…”

Energy-Transfer-Enabled Radical Acylation Using Free Alkyl Boronic Acids through Photo and NHC Dual Catalysis

“…In recent years, N -heterocyclic carbene (NHC) radical catalysis has emerged as a fertile platform for the discovery of novel acylation reactions . As one of the key intermediates in NHC catalysis, the acyl azolium species can produce a persistent ketyl radical by single-electron reduction.…”

NHC and photoredox catalysis dual-catalyzed 1,4-mono-/di-fluoromethylative acylation of 1,3-enynes

“…As pioneered by Ohmiya, 20 a Studer, 21 a , b and Chi 22 a N-heterocyclic carbenes (NHCs) 23 could modulate the reactivity of acyl radicals, 24 which opened a new avenue for acyl radical participating radical–radical cross coupling. 20–22,25–29 In this scenario, persistent NHC-attached acyl radicals generated from single-electron-transfer (SET) oxidation of a Breslow intermediate 20 a , b ,26 or photoredox assisted SET reduction of acylazolium 21,27–29 underwent radical cross-coupling with transient alkyl or allene radicals. Inspired by these elegant approaches, we speculated that employing Hu's reagent (CH 2 FSO 2 Na) and carboxylic acid derivatives might enable the generation of the CFH 2 radical and NHC-attached acyl radical under NHC/PC dual-catalyzed conditions by releasing SO 2 .…”