Metallaphotoredox-Mediated C_sp2–H Hydroxylation of Arenes under Aerobic Conditions

Abstract

The direct hydroxylation of 2-arylpyridines and 2-arylbenzothiazoles via the merger of organic photoredox and metal catalysis is reported where 4CzIPN is used as the visible-light photocatalyst and Pd(OAc) as the metal catalyst. This method has been employed to synthesize organic molecules exhibiting excited-state intramolecular proton transfer properties for generating tunable luminescence responses.

Enhancing Ru(II)‐Catalysis with Visible‐Light‐Mediated Dye‐Sensitized TiO2 Photocatalysis for Oxidative C−H Olefination of Arene Carboxylic Acids at Room Temperature

“…However, less abundance and high cost of these catalysts are the major issues towards their broad utility. Organic dyes are also found ineffective and only sporadic examples are reported in this direction . Thus, the introduction of readily available inexpensive photo‐redox catalysts with good chemical stability can fulfil the available synthetic space in metallaphotoredox catalyzed C−H bond activation reactions.…”

Synthesis of Phenolic Compounds via Palladium Catalyzed C−H Functionalization of Arenes

“…Direct C−H hydroxylation of 2‐arylpyridines and 2‐arylbenzothiazoles by merging transition metal catalysis with photocatalysis was reported by Singh et al. (Figure ) . With this protocol, a wide array of hydroxylated arenes were synthesized at room temperature under visible‐light photoirradiation using 4CzIPN (1,2,3,5‐tetrakis(carbazol‐9‐yl)‐4,6‐dicyanobenzene) as organophoto‐catalyst and Pd(OAc) 2 as metal catalyst in the presence of BrCCl 3 and O 2 .…”

“…DirectC ÀHh ydroxylation of 2-arylpyridines and 2-arylbenzothiazolesbymergingt ransition metal catalysis with photocatalysis was reported by Singh et al (Figure 47). [32] With this protocol, aw ide array of hydroxylated arenes were synthesized at room temperature under visible-light photoirradiation using Chem. Asian J.…”

Recent Advancements on Transition‐Metal‐Catalyzed, Chelation‐Induced ortho‐Hydroxylation of Arenes

“…developed an elegant Pd(II)-catalyzed ortho-hydroxylation of 2arylpyridines (Scheme 12) and 2-aryl benzothiazoles (Scheme 13) using photocatalyst 4CzIPN [1,2,3,5tetrakis(carbazol-9-yl)-4,6-dicyanobenzene]. [30] Addition of only 2 mol% 4CzIPN in a mixture of Pd(OAc) 2 (10 mol%), BrCCl 3 (2 equiv) and toluene under visible light and oxygen prompted the reaction for successful hydroxylation. Similarly, benzothiazole provided ortho-hydroxylated product under the same reaction condition when cyclohexane was used instead of toluene in DCE.…”