The readily available carbonyl(pentamethylcyclopentadienyl)cobalt diiodide complex [Cp*Co(CO)I 2 ] was successfully utilized as the precursor of a cationic cobaltA C H T U N G T R E N N U N G (III) active catalyst for directed C À H bond functionalization. The complex Cp*Co(CO)I 2 (2.5-1.25 mol%), in combination with silver hexafluoroantimonate (AgSbF 6) and potassium acetate (KOAc), efficiently catalyzed the directed C-2 selective amidation of indoles with sulfonyl azides, and the corresponding products were obtained in 85-98 % yield.

The unique reactivity of [Cp*Co(III)] over [Cp*Rh(III)] was demonstrated. A cationic [Cp*Co(III)] catalyst promoted direct dehydrative C-H allylation with non-activated allyl alcohols, thus giving C2-allylated indoles, pyrrole, and phenyl-pyrazole in good yields, while analogous [Cp*Rh(III)] catalysts were not effective. The high γ-selectivity and C2-selectivity indicated that the reaction proceeded by directing-group-assisted C-H metalation. DFT calculations suggested that the γ-selective substitution reaction proceeded by C-H metalation and insertion of a C-C double bond, with subsequent β-hydroxide elimination. The [Cp*Co(III)] catalyst favored β-hydroxide elimination over β-hydride elimination.

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C2-selective indole C-H phosphoramidation was achieved through improved Cp*Co(III) catalysis. A cationic Co(III) species generated in situ from a Cp*CoI2-dimer showed the best catalytic activity, giving phosphoramidated indoles in 60-86% yield.