Rhodium(III)-catalyzed Intramolecular Ar-H/Ar-H Coupling Directed by Carboxylic Group to Produce Dibenzofuran Carboxylic Acids

The rhodium-catalyzed intramolecular Ar-H/Ar-H coupling of 3-phenoxybenzoic acids proceeds smoothly, accompanied by double C-H bond cleavage at the 2- and 2'-positions, to produce dibenzofuran-l-carboxylic acid derivatives. Related tetra- and pentacyclic molecules can also be readily constructed by the present procedure. A reaction mechanism involving 1,4-rhodium(III) migration is proposed.