On the Reactivity of Tetrakis(trifluoromethyl)cyclopentadienone towards Carbon-Based Lewis Bases

The reactivitiy of tetrakis(trifluoromethyl)cyclopentadienone towards different C‐based Lewis bases, such as N‐heterocyclic carbenes (NHC), ylides and isonitriles, are reported. While sterically not hindered carbenes were found to yield kinetic adducts by regiospecific nucleophilic attack at the position adjacent to the carbonyl group of the ketone, bulkier nucleophiles afforded the thermodynamically more stable O‐bridged zwitterions. Interestingly, isonitriles were found to dimerize and trimerize under the same reaction conditions, forming bicyclic products that evolve differently depending on the nature of the substituents. A ketone as Lewis acid: The reactivity of tetrakis(trifluoromethyl)cyclopentadienone towards C‐based Lewis bases has been studied. Interestingly, while N‐heterocyclic carbenes (NHCs) form C‐ or O‐adducts depending on their steric requirements, isonitriles are found to dimerize or trimerize.