Dehydrative Direct CH Allylation with Allylic Alcohols under [Cp*Co^III] Catalysis

Abstract

Abstract 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.