Flash Communication: Exocyclic Alkenyl Tuning of Cyclic (Amino)carbene: Enhancing π-Acceptor Property without Ring Unsaturation

A new type of ambiphilic singlet carbene, termed cyclic (alkenyl)(amino)carbene ( exo -CA en AC), has been developed by replacing the endocyclic sp 3 -alkyl group of classical CAACs with an exocyclic alkenyl moiety. This structural modification imparts enhanced π-acceptor character while preserving a strong σ-donating ability, as supported by DFT studies. The representative exo -CA en AC is generated in situ from a dibenzobarrelene-derived iminium salt and can be trapped with selenium or group 9 and 11 metal precursors.