A visible-light-induced bromine radical initiates direct C–H alkylation of heteroaromatics

Abstract

Herein, a photoredox-induced direct C(sp2)–H alkylation of N- Heteroaromatic by using commercially available tetrabutylammonium tribromide (TBATB) as a HAT reagent is described. The method is featured uses O2 as the...

A Facile Method for Multigram Scale Light-Induced Synthesis of 4′-(Bromomethyl)-2-cyanobiphenyl

“…There is also the possibility that any presence of tribromide, [Br 3 ] − , could hamper the bromination reaction because of the removal of free Br 2 from the solution. Nevertheless, [Br 3 ] − has been used before with success as a source of bromine radicals. − Any negative impact on the yield could in this case be caused by slower kinetics when [Br 3 ] − is the source of the bromine radicals.…”

Electroreductive Remote Benzylic C(sp3)–H Arylation of Aliphatic Ethers Using Cyanoarenes for the Synthesis of α-(Hetero)aryl Ethers

“…Among radical methods, direct α-C­(sp 3 )–H arylation of abundant ethers and their derivatives is of particular value and appeal since it can selectively append various (hetero)­aryl functionalities into the α-C­(sp 3 )–H bonds adjacent to the oxygen atom for the expeditious installation of important complex (hetero)­aryl compounds, even for the construction of quaternary carbons, thus significantly increasing the potency of bioactive molecules . Conventional radical methodologies for direct α-C­(sp 3 )–H arylation of ethers involve both the cross-dehydrogenative coupling (CDC) and the Minisci-type reaction, ,, which generally operate with oxidants (often peroxides and persulfates) to enable the selective formation of the α-C­(sp 3 )-centered radicals via hydrogen atom transfer (HAT) of the α-C­(sp 3 )–H bonds in ethers and then arylation. ,, Although the direct α-C­(sp 3 )–H arylation of ethers has been well explored, many transformations require the use of excess oxidants, external catalysts, and elevated temperature, thereby possessing low functional group tolerability and unsatisfactory selectivity. Especially, for unsymmetrical ethers, regioselective functionalization between α-positions remains greatly challenging and is underdeveloped with few reports, owing to the strongly similar reactivity of nearly equivalent C­(sp 3 )–H bonds (Scheme a) .…”