Synthesis of ortho-Azophenols by Formal Dehydrogenative Coupling of Phenols and Hydrazines or Hydrazides.
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.
Department of Chemistry, McGill University, 801 Sherbrooke St. W., Montreal, Quebec, H3A 0B8, Canada.
Kenneth Virgel N
KVN
Esguerra
Department of Chemistry, McGill University, 801 Sherbrooke St. W., Montreal, Quebec, H3A 0B8, Canada.
Jean-Philip
http://orcid.org/0000-0002-9283-1199
JP
Lumb
C−H functionalization; aerobic reactions; copper catalysis; hydrazine; phenol