Cobalt-Catalyzed C–H Activation and [3 + 2] Annulation with Allenes: Diastereoselective Synthesis of Indane Derivatives

Abstract

An unprecedented bidentate directing-group-assisted cobalt-catalyzed oxidative C–H activation of aryl hydrazones followed by a syn-diastereoselective [3 + 2] annulation reaction has been achieved, employing allenes as the annulation partners. The selective 2,3-migratory insertion of allenes with arylcobalt(III) species and the subsequent intramolecular diastereoselective nucleophilic addition of η1-allylcobalt onto the imine resulted in [3 + 2] annulation over the alternative [4 + 2] annulation. Furthermore, the oxidative annulation obviates the need for stoichiometric metal oxidants and proceeds under aerobic conditions.

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