Selective Oxidative Phenol Coupling by Iron Catalysis

Abstract

The iron-catalyzed oxidative coupling of phenols has emerged as a powerful method for preparing complex phenolic frameworks from simple and readily available compounds. This synopsis describes the selectivity challenges inherent in oxidative coupling reactions while at the same time presents our mechanistic-driven strategy employed to confront them.

Synthetic Applications of Oxidative Aromatic Coupling—From Biphenols to Nanographenes

“…Recently, Egami and Katsuki developed chiral iron(salan) complexes (Scheme ), which afforded unsubstituted BINOL and 3,3′‐disubstitued derivatives with an enantiomeric excess of 64 % and up to 97 %, respectively . Progress in the asymmetric synthesis of biaryls has been briefly summarized in recent articles . The most important recent contributions are presented below.…”

“…[89] Progress in the asymmetric synthesis of biaryls has been briefly summarized in recent articles. [47,88,90,91] Themost important recent contributions are presented below.…”

Synthesis of Biaryl‐Bridged Cyclic Peptides via Catalytic Oxidative Cross‐Coupling Reactions

“…In order to address the above difficulties, we examined the idea of facilitating the oxidative coupling of tyrosine by introducing a removable activating group (AG). We postulated that a tert ‐butyl group at the ortho position of tyrosine would comply with the electronic and steric requirements of tyrosine as a coupling partner and therefore enhance its reactivity . This idea derives from the evidence that bulky alkyl groups at the ortho position of phenols reduce the bond dissociation energy (BDE) of the ArO−H bond .…”

Catalytic Aerobic Phenol Homo‐ and Cross‐Coupling Reactions with Copper Complexes Bearing Redox‐Active Guanidine Ligands

“…[15,16] Traditionally,n on-symmetric biphenols are prepared by transition-metal-catalyzed cross-coupling reactions of aryl halides (ArX). [20,21] For practical reasons, the parameter N of ap henol wass imply defined by the authors as the HOMO energy relative to tetrachloroethylene, allowing its determination by standard DFT methods. In their seminal work, Pappo et al systematically studied cross-coupling reactions of phenolsw ith ar adical-anion coupling mechanism and grouped the phenol cross-coupling reactions in two categories depending on their redox potential and "global nucleophilicity"( N)( Scheme1).…”

“…In their seminal work, Pappo et al systematically studied cross-coupling reactions of phenolsw ith ar adical-anion coupling mechanism and grouped the phenol cross-coupling reactions in two categories depending on their redox potential and "global nucleophilicity"( N)( Scheme1). [20,21] For practical reasons, the parameter N of ap henol wass imply defined by the authors as the HOMO energy relative to tetrachloroethylene, allowing its determination by standard DFT methods. [20] Clearly,f or ap air of phenols A and B with E Ox (A) < E Ox (B), the oxidationo fp henol A to ap henoxyl radical is thermodynamically favored.…”