Regioselective functionalization of arenes remains a challenging problem in organic synthesis. Steric interactions are often used to block sites adjacent to a given substituent, but they do not distinguish the remaining remote sites. We report a strategy based on remote steric control, whereby a roof-like ligand protects the distant para site in addition to the ortho sites, and thereby enables selective activation of meta carbon-hydrogen (C–H) bonds in the absence of ortho or para substituents. We demonstrate this concept for iridium-catalyzed meta -selective borylation of various monosubstituted arenes, including complex drug molecules. This strategy has the potential to expand the toolbox of C–H bond functionalization to previously nondifferentiable reaction sites.

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A Co(III)-catalyzed [4 + 1] annulation of amides with allenes to synthesize isoindolone and 1,5-dihydro-pyrrol-2-one derivatives is reported. A wide range of aromatic and vinylic amides react with allenes to give the corresponding annulation products in good to excellent yields. The mechanistic studies strongly support that the catalytic reaction proceeds through an amide-directed CÀH activation, followed by carbocobaltation of allene, b-hydride elimination, and an intramolecular 1,2hydroamination.

A cobalt-catalyzed C−H/N−H annulation of anilides with allenes to synthesize 1,2-dihydroquinolines is described. The reaction proceeds via a C−H activation, allene insertion, followed by β-hydride elimination and an intramolecular 1,4-addition to a butadiene-group-containing intermediate. Allenes act as a threecarbon source in the present C−H activation strategy.

An efficient C-H activation method for the ortho alkynylation of aromatic N-methoxyamides with hypervalent iodine-alkyne reagent using a ruthenium catalyst is described. The reaction proceeds under mild reaction conditions with broad substrate scope. A possible catalytic cycle involving a ruthenium carboxylate assisted C-H bond cleavage is proposed from the preliminary mechanistic evidence.