Photochemical Allylation of Alkanes Enabled by Nickel Catalysis

Abstract

We have developed an allylic alkylation of alkanes by dual photo-HAT/nickel catalysis. In this reaction, radical-type hydrogen-atom-transfer of the alkanes is enabled by decatungstate as a photocatalyst, whereas nickel serves to cleave the C–O bond in the substrates under mild reaction conditions. This co-catalyzed reaction provides a method for direct functionalization of alkanes. Density functional theory calculations show that reductive elimination is the rate-determining step of this reaction.

Tetrabutylammonium decatungstate (TBADT), a compelling and trailblazing catalyst for visible-light-induced organic photocatalysis

“…The allylic alkylation of alkanes by synergistic photo-HAT/ nickel catalysis was reported by Gong et al, Scheme 29. 53 This process enables direct functionalization of alkanes, opening Scheme 47 Photocatalyzed hydroacylation of terminal alkyne.…”

On the Realties of Base Metal Catalysis: An Overview

“…Several research articles highlight the ability of Ni(II) bipyridine (bipy), phenanthroline (phen), and related complexes to perform radical C-E (E = C, F) coupling reactions under reducing or photocatalytic conditions. 34,[43][44][45][46] The recent surge of Ni catalysts to perform stereo-convergent cross-coupling reactions benefits from the ability of the Ni species to generate radical intermediates. Liu and Diao recently studied the mechanism of a classical [Ni(bipy)] complex and found that alkyl radical formation forms via a concerted mechanism (Figure 3B) with the bipy ligand acting as an electron reservoir.…”

“…These feature easily-synthesized pyridine and phosphine derived ligands, allowing for the direct allylation of alkanes under mild conditions. 46 Hosseini-Sarvari, similarly, presents a semi-heterogeneous photocatalytic system in which TiO2 nanoparticles are coupled with a simple NiCl2•glyme catalyst to perform photocatalytic C-P bond formation between aryl iodides and diarylphosphine oxides. 89 Taking inspiration from photosynthetic processes within nature, organic photocatalysts can be used in place of precious metal photoredox systems.…”

Atom Transfer Radical Coupling Enables Highly Enantioselective Carbo-Oxygenation of Alkenes with Hydrocarbons

“…Notably, the development of efficient chiral dirhodium catalysts developed by Davies has enabled site-selective and stereoselective alkylation of unactivated alkanes (Scheme A, top). Another widely employed strategy is controllable radical C–H functionalization via a hydrogen atom transfer (HAT) process, which finds extensive use in the functionalization of hydrocarbons . In this context, transition-metal-catalyzed radical relay, chiral Lewis acid catalysis, and organocatalyst-mediated radical coupling have enabled enantioselective transformations of aliphatic C–H bonds (Scheme A, middle and bottom).…”