Selective Aerobic C-H Amination of Phenols with Primary Amines over Copper toward Benzoxazoles.

Using O2 as the oxidant, the benzoxazole frameworks can be directly constructed from the readily available phenols and primary amines in the presence of NH4 PF6 over copper under mild conditions. Mechanistic studies showed that a novel mechanism involving biphenyldiols and o-quinones very possibly takes effect in the reaction, because both can selectively give the benzoxazoles under the reaction conditions. An unprecedented unstrained Caryl -Caryl bond cleavage takes place in the reaction.