Trifluoromethyl-promoted Oxygen-atom Insertion Of (NHC)-copper Complexes

In recent years, research on trifluoromethylation reactions has been developed rapidly.Since the special chemical and physical properties of the trifluoromethyl group, it plays anincreasingly important role in the field of medicine, pesticides and materials. Althoughtrifluoromethyl reaction has made important progress, the special nature of thetrifluoromethyl performance in the reaction is not very clear, which has been subject to theresearchers’ attention.This is the first discovery of trifluoromethyl promoted oxygen-atom insertion ofN-Heterocyclic Carbene (NHC)-copper complex with N,N-dimethylformamide (DMF), thatis one of the most straightforward and simple new methods in transferring metal-carbonbonds into carbon-oxygen double bond (C=O) bond. Experimental results show that theoxygen atom of the product is from DMF, while the trifluoromethyl shows significant rolein promoting the reaction. Various (NHC)-copper complexes are applicable, and obtainmoderate yields (48-94%). Finally, a possible reaction mechanism is proposed by thecontrol experiments with trifluoromethylcopper intermediate.Based on this,(NHC)-copper complex oxidated by DMSO is uncovered for the firsttime, in which DMSO is first successful used in oxidating the metal carbene complexes. Inthe mild reaction conditions, a variety of (NHC)-copper complexes are applicable, and getmoderate yields (33-79%). Surprisingly, it is also successfully applied to the nitrogen oxideas an oxidant in this reaction. Eventually, a supposed mechanism is suggested by thecontrol experiments.It has very important significance in studying new conversion process of metalcarbene complexes with unexpected discovery of the special role of trifluoromethyl group.It has been reported about the characteristics of trifluoromethyl in the organic reactions ormetal complexes, researching on that it will contribute to depth understanding thetrifluoromethylation mechanism. It provides an important theoretical basis for thedevelopment of new trifluoromethyl reactions.