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Alkenes and arenes represent two classes of feedstock compounds whose union has fundamental importance to synthetic organic chemistry. We report a new approach to alkene arylation using diaryliodonium salts and Cu catalysis. Using a range of simple alkenes, we have shown that the product outcomes differ significantly from those commonly obtained by the Heck reaction. We have used these insights to develop a number of new tandem and cascade reactions that transform readily available alkenes into complex arylated products that may have broad applications in chemical synthesis.

For over a century, chemical transformations of benzene derivatives have been guided by the high selectivity for electrophilic attack at the ortho/para positions in electron-rich substrates and at the meta position in electron-deficient molecules. We have developed a copper-catalyzed arylation reaction that, in contrast, selectively substitutes phenyl electrophiles at the aromatic carbon-hydrogen sites meta to an amido substituent. This previously elusive class of transformation is applicable to a broad range of aromatic compounds.

We have developed a new site-selective Cu(II)-catalyzed C-H bond functionalization process that can selectively arylate indoles at either the C3 or C2 position under mild conditions. The scope of the arylation process is broad and tolerates broad functionality on both the indole and aryl unit, which makes it amenable to further elaboration. The mechanism of the arylation reaction is proposed to proceed via a Cu(III)-aryl species that undergoes initial electrophilic addition at the C3 position of the indole motif. We speculate that site of indole arylation arises through a migration of the Cu(III)-aryl group from C3 to C2, and this can be controlled by the nature of the group on the nitrogen atom; free (NH)- and N-alkylindoles deliver the C3-arylated product, whereas N-acetylindoles afford the C2 isomer, both with excellent yield and selectivity.