Catalytic Oxidative Coupling of Phenols and Related Compounds

Abstract

Phenols and their derivatives are the elementary building blocks for several classes of complex molecules that play essential roles in biological systems. Nature has devised methods to selectively couple phenolic compounds, and many efforts have been undertaken by chemists to mimic such coupling processes. A range of mechanisms can be involved and with well-studied catalysts, reaction outcomes in phenol-phenol oxidative coupling reactions can be predicted with a good level of fidelity. However, reactions with catalysts that have not been studied or that do not behave similarly to known catalysts can be hard to predict and control. This Perspective provides an overview of catalytic methods for the oxidative coupling of phenols, focusing on the last 10 years, and summarizes current challenges.

Keywords: biphenols; cross-coupling; dehydrogenative coupling; oxidative coupling; phenol coupling.

Scheme 1.

Retrosynthetic Analysis of Honokiol

Scheme 2.

Effect of Oxidation Potentials on Reaction Outcomes

Scheme 3.

Phenol-Phenol Coupling Site-selectivity

Scheme 4:

Enantioselective Phenol-Phenol Oxidative Coupling

Scheme 5:

Oxidative Phenol Coupling and Possible Reaction Outcomes

Scheme 6:

Intramolecular Phenol-Phenol Coupling and Myricanol Synthesis

Scheme 7:

Mechanisms of Oxidative Phenol Coupling Reaction

Scheme 8:

Resonance Forms of a Phenoxyl Radical

Scheme 9:

Selective Phenol Homo-Coupling Reactions.

Scheme 10:

Photocatalytic Phenol Homo-Coupling Reactions

Scheme 11:

a) ortho-para Site Selective Oxidative Phenol Homo-Coupling b) ortho-para Site Selective Oxidative Phenol Homo-Coupling Leading to Pummerer Ketone Generation

Scheme 12:

Hydroxycarbazole ortho-ortho’ Dimerization and ortho-ortho Tetramerization

Scheme 13:

Electrochemical meta-meta/meta-para Oxidative Phenol Couplings

Scheme 14:

Chromium Catalyzed Phenol Cross-Coupling

Scheme 15:

Electrochemical and Iron Catalyzed Phenol Cross-Coupling

Scheme 16:

Photocatalytic Phenol Cross-Coupling

Scheme 17:

Enantioselective Phenol-Phenol Oxidative Coupling

Scheme 18:

Enantioselective Phenol-Phenol Oxidative Coupling Mechanism

Scheme 19:

Ruthenium Catalyzed Enantioselective Cross-Coupling Reaction

Scheme 20:

Vanadium Catalyzed Enantioselective Cross-Coupling Reaction

Scheme 21:

Scope of the Intramolecular Oxidative Phenol Coupling with a Vanadium Catalyst

Scheme 22:

Natural Products with Phenol C–O Couplings

Scheme 23:

C–C/C–O/C–O Phenol Coupling with a Copper Catalyst

Scheme 24:

Mechanism of the C–C/C–O/C–O Phenol Coupling

Scheme 25:

Unsymmetrical Trimerization via C–O Coupling

Scheme 26:

Linear Triphenols from the ortho-Quinone Spiroketals

Scheme 27:

Naphthylamine Phenol C–C vs C–O coupling

Scheme 28:

Copper Catalyzed Selective Phenol C–O Coupling

Scheme 29:

β-O Alkenylphenol Coupling with a Vanadium Catalyst

Scheme 30:

Mechanism of Vandium Catalyzed β-O vs β-β Alkenylphenol Coupling

Scheme 31:

β-β Alkenylphenol Coupling with a Vanadium Catalyst

Scheme 32:

Exocyclic Oxidative Phenol Coupling Reaction

Scheme 33:

Aniline-Phenol/Aminonaphthalene-Phenol Oxidative Couplings

Scheme 34:

Aniline-Phenol/oxizole -Phenol Oxidative Couplings

Scheme 35:

β-Ketoesters/Phenols Oxidative Couplings

Scheme 36:

β-Ketoesters/Phenols Oxidative Couplings C–C vs C–O

Scheme 37:

Malononitriles-Phenol/Aniline/Heteroarene Oxidative Coupling

Scheme 38:

Phenol/Arene Oxidative Coupling with Fe Catalyst or Through Electrochemical Processes

Scheme 39:

Oxidative Coupling of Phenols and Alkenes

Scheme 40:

Oxidative Coupling of Phenols and Hydrazides

Scheme 41:

Copper Catalyzed Oxindole Oxidative Coupling Reactions