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We report herein an ortho‐C–H alkenylation reaction of aryl imines with alkenyl phosphates promoted by a cobalt–N‐heterocyclic carbene (NHC) catalytic system. While commercially available bulky NHC ligands exhibited only modest catalytic activity, elaboration of the nitrogen substituents and backbone of the NHC enabled the desired transformation to proceed in high yield at a mild temperature. The new Co–NHC system proved applicable to a variety of aryl imines and alkenyl phosphates to afford ortho‐alkenylated aryl imines, which serve as precursors to benzofulvene derivatives. MOE (Min. of Education, S’pore) Accepted version

The Co(II)/imidazolium catalyst in combination with neopentylmagnesium bromide allows arylation at room temperature.

An ortho-arylation reaction of aromatic imines with aryl chlorides has been achieved using a cobalt–N-heterocyclic carbene catalyst in combination with a neopentyl Grignard reagent. The reaction takes place at room temperature to afford biaryl products in moderate to good yields.

Ternary catalytic systems consisting of cobalt salts, phosphine ligands, and Grignard reagents promote addition of arylpyridines and imines to unactivated internal alkynes with high regio- and stereoselectivities. Deuterium-labeling experiments suggest that the reaction involves chelation-assisted oxidative addition of the aryl C−H bond to the cobalt center and insertion of the C−C triple bond into the Co−H bond, followed by reductive elimination of the resulting diorganocobalt species.