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

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 eta(1)-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.

Automated summary

This study achieved a novel bidentate directing-group-assisted cobalt-catalyzed oxidative C-H activation of aryl hydrazones followed by a syn-diastereoselective [3 + 2] annulation reaction using allenes as annulation partners, bypassing the need for stoichiometric metal oxidants and operating under aerobic conditions.