A major issue with employing activating groups for the functionalization of arenes is the lack of atom economy.  We are addressing this shortcoming by developing new methods catalyzed by first-row transition metals that essentially 'recycle' the activating group, so that it can be employed for multiple bond formations in efficient tandem reactions. In this context, I will discuss a Cu(I)-catalyzed 1,3-halogen migration reaction capable of transferring chlorine, bromine or iodine from an aromatic carbon to a benzylic carbon with concomitant borylation of the Ar-X bond. The resulting benzyl halide can be reacted in the same vessel under a variety of conditions to form an additional carbon-heteroatom bond. Cross-over experiments using an isotopically enriched bromide source support an intramolecular transfer of the halogen, and the reaction can be rendered asymmetric by employing enantioenriched, electron-rich bidentate phosphine ligands.  This talk will discuss the scope and synthetic applications of this novel transformation, as well as mechanistic studies that provide insight into developing a whole suite of powerful Cu-catalyzed arene functionalizations.

Cu-catalyzed recycling of halogen activating groups via 1,3-halogen migration

245th National Meeting (2013)

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