Arene‐Limited Nondirected C−H Activation of Arenes

Abstract

The nondirected C(sp2)−H activation of simple arenes has advanced significantly in recent years through the discovery of new catalyst systems that are able to perform transformations with the arene as the limiting reagent. Important developments in catalyst and ligand design that have improved reactivity and selectivity are reviewed.

Palladium-Catalyzed Late-Stage Direct Arene Cyanation

“…This challenge is illustrated by the very limited reports on transition-metal-catalyzed C-H functionalization with arene as the limiting reagent. [43][44][45][46][47][48][49][50][51] In 2017, Yu and coworkers reported a palladium (Pd)catalyzed, pyridone-ligand-enabled Fujiwara-Moritani olefination reaction with arenes as limiting reagent. 43 Shortly thereafter, van Gemmeren reported the same transformation using a combination of a pyridine ligand and a mono-N-protected amino acid (MPAA) ligand.…”

Electrophotocatalytic Undirected C−H Trifluoromethylations of (Het)Arenes

“…Our studiesw ere initiatedb ye xploring the electrophotochemicaln ondirected CÀHt rifluoromethylation of readily accessiblem esitylene (1a) [21] with the Langloisr eagent (CF 3 SO 2 Na, 2)i na no perationally-simple, user-friendly undivided cell set-up. These orientings tudiesu tilized ap latinum plate cathodea nd ag raphite felt (GF) anode, employing [Mes-Acr + ] ClO 4 À as ap hotocatalyst (PC) and cost-effective KOAc as ac onductive additive in CH 3 CN at ar oom temperature (rt) of 23 8C (Scheme 1).…”

Palladium Catalyzed C−H Olefination of Indolizines at the 1‐Position with Molecular Oxygen as the Terminal Oxidant

“…In this context, the undirected functionalization CÀ H bonds was recognized as a robust complementary approach to directed CÀ H activation, mainly because of its unique ability to reach more distant sites and can be applied to substrates without appropriate directing groups. [3] However, the functionalization of unreactive CÀ H bonds without the assistance of a chelating auxiliary is difficult to achieve, and selective functionalization without an existing coordinating groups controlling the regionselectivity is a more challenge. Recent years have witnessed intensive investigations culminated in the development of various catalytic systems to improve the reactivity and control the selectivity of non-directed CÀ H functionalization reactions.…”