Auxiliary‐Directed C(sp³)−H Arylation by Synergistic Photoredox and Palladium Catalysis

Abstract

Herein we describe the auxiliary-directed arylation of unactivated C(sp )-H bonds with aryldiazonium salts, which proceeds under synergistic photoredox and palladium catalysis. The site-selective arylation of aliphatic amides with α-quaternary centres is achieved with high selectivity for β-methyl C(sp )-H bonds. This operationally simple method is compatible with carbocyclic amides, a range of aryldiazonium salts and proceeds at ambient conditions.

A comprehensive overview of directing groups applied in metal-catalysed C–H functionalisation chemistry

“…Indeed, by combining Pd catalysis and photoredox, Polyzos achieved the arylation of aliphatic amides derived from Q′NH 2 with α-quaternary centers in moderate to good yields (21–78%, Scheme 86A ). 518 The transformation was selective towards primary C(sp 3 ) centres and even a benzylic methylene group remained unaffected.…”

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

“…In contrast to C(sp 2 )-H bonds, C(sp 3 )-H bond activation is much more challenging. Inspired by the potential of bicoordinating DGs to facilitate C(sp 3 )-H metalation, Polyzos's group reported the direct arylation of aliphatic bonds with aryldiazonium salts via a palladium/photoredox dual catalysis ( Figure 26) [88]. The method utilized an 8-aminoquinoline-derived biden- were tolerated on the C-H substrates and electron-poor as well as electron-rich diazonium salts could be coupled smoothly.…”

“…Inspired by the potential of bicoordinating DGs to facilitate C(sp 3 )–H metalation, Polyzos’s group reported the direct arylation of aliphatic bonds with aryldiazonium salts via a palladium/photoredox dual catalysis ( Fig. 26 ) [ 88 ]. The method utilized an 8-aminoquinoline-derived bidentate auxiliary, and, in contrast with a vast majority of C(sp 3 )–H bond activation reactions, was effective at room temperature.…”

Merging Transition-Metal Catalysis with Photoredox Catalysis: An Environmentally Friendly Strategy for C–H Functionalization

“…Compared with C(sp 2 )-H bond transformations, C(sp 3 )-H bond activation is more challenging. Inspired by the recent impressive progress of auxiliary-directed activation of C(sp 3 )-H bonds, in 2017, Polyzos and co-workers 30 reported a novel arylation of unactivated C(sp 3 )-H bonds with aryldiazonium salts via synergistic Pd/photoredox dual catalysis (Scheme 22). This method features mild reaction conditions, broad substrate scope and high selectivity for β-methyl C(sp 3 )-H bonds.…”