Nitrosonium-Mediated Phenol–Arene Cross-Coupling Involving Direct C–H Activation

Abstract

The nitrosonium ion (NO+) is a highly versatile nitration and nitrosation reagent, as well as a strong one-electron oxidant. Herein, we describe an environmentally benign and mild method for the in situ formation of NO+ from readily available inorganic nitrate salts, i.e. lithium nitrate, through a finely tuned interplay between formic acid and MeOH, which are used as the solvent system. This methodology was applied to the NO+-induced oxidative C–H activation of methoxy-substituted phenols, which are versatile lignin-derived aromatic feedstocks, to achieve C–C cross-coupling reactions with arenes. The regeneration of NO+ by atmospheric molecular oxygen enables substoichiometric use of the nitrate.