Ruthenium(II)‐Catalyzed CH Alkenylations of Phenols with Removable Directing Groups

Abstract

Cationic ruthenium(II) complexes enabled oxidative alkenylations of phenols bearing easily cleavable directing groups. The optimized catalytic system allowed twofold CH bond activations with excellent chemo-, site-, and diastereoselectivities. The double CH functionalization process proceeded efficiently in an aerobic fashion under an atmosphere of ambient air. Detailed mechanistic studies were performed and provided strong support for an initial reversible CH bond activation by the formation of six-membered ruthenacycles as the key intermediates.

CH Functionalization of Phenols Using Combined Ruthenium and Photoredox Catalysis: In Situ Generation of the Oxidant

“…[11] Using a 2-pyridyl protecting group (Pyr), the selective ortho olefination of a variety of aromatic and heteroaromatic compounds could be achieved. [11] Using a 2-pyridyl protecting group (Pyr), the selective ortho olefination of a variety of aromatic and heteroaromatic compounds could be achieved.…”

“…Quite recently, the group of Ackermann extended the substrate scope to protected phenols. [11] Using a 2-pyridyl protecting group (Pyr), the selective ortho olefination of a variety of aromatic and heteroaromatic compounds could be achieved. This procedure made use of over-stoichiometric amounts of Cu II salts.…”

Ruthenium Oxidase Catalysis for Site‐Selective C–H Alkenylations with Ambient O2 as the Sole Oxidant

“…Thev ersatile ruthenium(II) oxidase catalysis was not limited to the preparation of benzannulated heterocycles 3. Indeed, the aerobic C À Hf unctionalization also enabled aerobic alkenylations of phenol derivatives 4 [16] having ar emovable directing group (Scheme 2; Table S2). Thus, single-component ruthenium(II) biscarboxylates [17] could be used to successfully catalyze reactions with excellent chemoand positional selectivity.…”

Ruthenium(II)‐Catalyzed CH Acyloxylation of Phenols with Removable Auxiliary

“…[21,22] For instance, we have devised reaction conditions for step-economi-cal direct arylations [21] as well as alkenylations. [22] In consideration of the practical importance of substituted phenols and catechols, we became interested in exploring the use of the 2pyridyloxy substituent as a removable auxiliary for oxidative CÀH functionalization reactions that lead to CÀO-bond formation. As part of our ongoing research program on step-economical CÀH functionalizations, [23,24] we report herein the development of a protocol for the efficient oxygenation of unactivated aromatic CÀH bonds in 2-pyridyloxyarenes.…”