Hypervalent Activation as a Key Step for Dehydrogenative ortho CC Coupling of Iodoarenes

Building on earlier results, a direct metal-free [alpha]- arylation of substituted cyclic 1,3-diones using ArI(O2CCF3)2 reagents has been developed; unlike other arylative approaches, the arylated products retain the iodine substituent ortho to the newly formed CC bond. The mechanism is explored by using DFT calculations, which show a vanishingly small activation barrier for the CC bond-forming step. In fact, taking advantage of an efficient in situ hypervalent activation, the iodoarenes are shown to undergo a cross- dehydrogenative CC coupling at the CH ortho to the iodine. When Oxone is used as terminal oxidant, the process is found to benefit from a rapid initial formation of the hypervalent ArI(OR)2 species and the sulfate-accelerated final coupling with a ketone. This method complements the ipso selectivity obtained in the metal-catalyzed [alpha]-arylation of carbonyl compounds.