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Synthesis of ortho ‐Azophenols by Formal Dehydrogenative Coupling of Phenols and Hydrazines or Hydrazides
Author(s) -
Esguerra Kenneth Virgel N.,
Lumb JeanPhilip
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201701226
Subject(s) - hydrazine (antidepressant) , hydrazide , chemistry , isomerization , catalysis , reagent , phenols , chromophore , combinatorial chemistry , stoichiometry , organic synthesis , molecular switch , condensation , organic chemistry , molecule , physics , chromatography , thermodynamics
Abstract Azophenols are important chromophores and reagents in organic synthesis, with applications as pigments and molecular switches. Here, we describe a catalytic aerobic process that couples phenols and hydrazines or hydrazides for their synthesis. The key aromatic C−N bond is formed by condensation between the hydrazine or hydrazide and an ortho ‐quinone, which triggers a redox‐isomerization to install the azo‐functionality. Notable features include rapid access to highly functionalized azophenols with a range of electronic configurations, including “push–pull” systems, conditions that employ simple, unactivated substrates, occurrence at room temperature using an earth‐abundant and commercially available copper catalyst, and production of water as the only stoichiometric byproduct.