Triflic Acid‐Catalyzed Chemo‐ and Site‐Selective C−H Bond Functionalization of Phenols With 1,3‐Dienes

Abstract

Herein, a Brønsted acid‐catalyzed C(sp2)−H functionalization of free phenols with 1,3‐dienes has been developed. In this transformation, triflic acid promoted C−H bond functionalization under mild conditions in a site‐selective manner.

Nickel/Brønsted acid dual-catalyzed regioselective C–H bond allylation of phenols with 1,3-dienes

“…1c, bottom left). 15 Therefore, the development of new catalytic systems for the site-selective C-H bond allylation of phenols with 1,3-dienes is desirable. As a continuation of our previous studies on nickel/ Brønsted acid dual-catalyzed regioselective allylation of N-H 16 and P-H bonds, 17 we speculated that the allylation of phenols will be achieved in an analogous dual catalytic system.…”

Csp2–H functionalization of phenols: an effective access route to valuable materials via Csp2–C bond formation

“…Further transformations of the product such as the debromination on the double bond, the Suzuki coupling with a phenyl boronic acid and the hydroxy group transformation were developed (Scheme 58). 160 In 2021, Liu and coworkers proposed a Lewis-acid-promoted para-allylic alkylation of phenol. Diazo compounds were employed as exceptionally reactive and versatile reagents capable of generating carbenes in order to synthesize paraallylated phenols through an insertion reaction.…”

Palladium-Catalyzed Chemo- and Regioselective C–H Bond Functionalization of Phenols with 1,3-Dienes

“…In 2019, Li and co-workers reported a B­(C 6 F 5 ) 3 -catalyzed 4,3-selective hydroarylation of 1,3-dienes with various phenols, and the reaction displayed excellent ortho -selectivity . Later, Liu and Zhang et al realized a triflic acid-catalyzed highly para -selective allylic alkylation of phenols with 1,3-dienes . During the preparation of this work, Yin’s group reported an elegant Ni/Brønsted acid dual-catalyzed regioselective C–H functionalization of phenols with 1,3-dienes, and TsOH has proved to be a necessary additive to enable the reaction to occur in this case .…”

“…To our delight, 1-naphthols could also be tolerated in this protocol. It is worth noting that 1-naphthols have never been reported as effective nucleophiles in previous reported studies on 1,3-diene hydrofunctionalizations. − Commercially available 1-naphthols 2i and 2j containing a methoxyl group at the C7 position reacted smoothly to furnish the corresponding allylic substitution products ( 3ai and 3aj ) in good yields (78% and 61%, respectively). In addition, polyfunctionalized electron-enriched phenols 2k , 2l , and 2m furnished the expected product 3ak , 3al , and 3am in decent to good yields (61%–84%).…”

“…14 Later, Liu and Zhang et al realized a triflic acid-catalyzed highly para-selective allylic alkylation of phenols with 1,3-dienes. 15 During the preparation of this work, Yin's group reported an elegant Ni/Brønsted acid dual-catalyzed regioselective C−H functionalization of phenols with 1,3dienes, and TsOH has proved to be a necessary additive to enable the reaction to occur in this case. 16 product from Markovnikov addition contains a stereogenic carbon center, and we thus envisage that the combination of a transition-metal and a suitable chiral ligand might enable good regio-and enantioselective control.…”