Functionalization of Azacalixaromatics by Cu(II)-Catalyzed Oxidative Cross-Coupling Reaction between the Arene C-H Bond and Boronic Acids.

Catalyzed by Cu(ClO4)2·6H2O under mild aerobic conditions using air as the oxidant, azacalix[1]arene[3]pyridines underwent a highly efficient oxidative cross-coupling reaction with a large number of aryl-, alkenyl-, and alkylboronic acids to afford diverse functionalized macrocycles. Stoichiometric reactions of an arylboronic acid with isolated and structurally well-defined high valent organocopper compounds indicated the involvement of arylcopper(II) rather than arylcopper(III) species as an organometallic intermediate in catalysis.