AIBN for Ru-catalyzed meta-C_Ar–H alkylation

Abstract

The meta-CAr–H alkylation of arenes with radicals produced from AIBN in the presence of a RuCl3 catalyst is presented.

Ruthenium-Catalyzed Meta-Selective C-H Difluoromethylation of Phenol Derivatives

“…Next, we found that meta-substituted phenol derivatives could not afford the difluoromethylated products along with the starting material being recovered (Scheme A-2). This result indicated that the cycloruthenium complex was specifically active on the C–H bond at the para position of the Ru–C bond, which was in agreement with the report published by Frost et al and Hofmann Ackermann . When D 2 O was added into the reaction, the deuterated product and the starting material were observed, indicating that C-H activation was reversible (Scheme B).…”

“…However, the high site-selective introduction of the difluoromethyl group via C-H functionalization has always been hindered due to the lack of site selectivity. Recently, ruthenium-catalyzed direct-activation reaction of the C-H bond in the meta-position has attracted significant attention and made progress, which includes benzene sulfonation, , alkylation, , halogenation, nitridation, , benzylation, benzoylation, and formylation reactions (Scheme a). The meta-selective difluoromethylation of the aromatic ring has been successfully realized by Ackermann et al., Wang et al, and our group (Scheme a).…”

Remote C–H Functionalizations by Ruthenium Catalysis

“…In addition to alkyl halides, azobis(alkylnitrile) compounds 74 were employed as alkylating agents for remote C-H alkylations, as presented by the group of Li (Scheme 22). 36 The decomposition of compounds 74 under thermal conditions eliminated a molecule of nitrogen gas and formed free alkyl radicals, which underwent site-selective C-C bond formations with arenes at the position para to ruthenium, furnishing the corresponding meta-alkylated products 75.…”

Ruthenium-Catalyzed Radical Cyclization/meta-Selective C–H Alkylation of Arenes via σ-Activation Strategy

“…Transition-metal-catalyzed meta -C Ar –H functionalization has been intensively developed in recent years, and four main strategies have been investigated: (a) the steric regiocontrol mode typically realized by Hartwig; (b) the template directing group elegantly designed by Yu, Maiti, and others; (c) the palladium/norbornene cooperative catalysis pattern mainly developed by Yu, Dong, Lautens, and others; and (d) the ruthenium-catalyzed C–H functionalization via σ-activation strategy established by Ackermann, Frost, and others. σ-Activation benefits from the ortho -ruthenation strategy, such as a series of C–H sulfonation, alkylation, halogenation, benzylation, nitration, acetylation, and others, have been developed through the development of a free radical or electrophilic reagent (Scheme a). Most recently, Ackermann and Greaney developed a novel photoinduced ruthenium-catalyzed meta -selective C–H alkylation at room temperature.…”