Stoichiometric couplings of methylarenes through visible-light-induced bromo radical formation from aryl halides

Abstract

A visible-light/nickel dual catalyzed stoichiometric coupling of methylarenes via bromine radical-enhance HAT has been developed. Aryl bromides serve as both cross-coupling partners and bromine radical precursor. Mechanistic studies reveal that...

Bromine radical-enhanced HAT activity leading to stoichiometric couplings of methylarenes with acid chlorides

“…We initially tried to reduce 2a to a stoichiometric amount under the optimized conditions of Rueping's report, but it failed. According to our previous reports 14 and Murakami's work, 12 the bromine radical was proved to be a highly efficient HAT reagent for the benzylic C(sp 3 )–H bond. Following this design, we applied Ir(dF(CF 3 )ppy) 2 (dtbpy)PF 6 ( PC1 ) as the photocatalyst, NiBr 2 as the source of the Ni catalyst and bromine radical, dtbbpy ( L1 ) as the ligand (for Ni), and K 2 HPO 4 as the base in acetone under irradiation of 35 W blue light for 12 h at room temperature.…”

“…Recently, the use of the bromine radical as an efficient HAT reagent was proved to highly accelerate the formation of a stable benzyl radical from methylarenes. 14 Continuing our research efforts to harness the bromine radical for versatile functionalization of benzylic C–H bonds, we envisioned establishing a new route for benzylic C–H acylation from cheap and abundant methylarenes and acid chlorides through photoredox and nickel dual catalysis at room temperature in a stoichiometric manner (Scheme 1d).…”

Radical-mediated photoredox hydroarylation with thiosulfonate

“…9 However, the hydroarylation of unactivated alkenes has not been exploited in such a concise photocatalytic protocol. 10 Within our continuing program on sustainable chemistry, 11 herein, we report a visible-light-induced intramolecular hydroarylation of quinazolinone-attached alkenes (Fig. 1d).…”

Electrochemical deoxygenative arylation of aldehydes and ketones

“…Recently, a number of methods through various strategies have been reported for synthesizing diaryl alkanes. 3,4 Transition-metal-catalyzed reactions are a promising strategy for diaryl alkane synthesis, particularly the cross-coupling reactions (Scheme 1A). 5 In 2014, Molander's group effectively carried out the energetically demanding C(sp 3 )–C(sp 2 ) cross-coupling of alkyltrifluoroborates with aryl halides via a photoredox/Ni dual catalysis mechanism.…”