N-Heterocyclic Carbene Copper Catalyzed C(sp)-C(sp~3) Bond Formations

Transition metal-catalyzed bond formation is the basic reaction in organic synthesis and has been one of the most efficient ways to construct C-C and C-heteroatom bonds.Recently,transition metal-catalyzed reactions with termial alkynes have attracted the attention of chemists,especially the C-C bond formations involving the sp-hybridized carbon atom.However,introducing one nonactivated alkyl group into a terminal alkynes to form C(sp)-C(sp~3)bonds is still challenging for quite a long time,and the corresponding reports are few.In this thesis,Cu-catalyzed C(sp)-C(sp~3)bond formations were studied,and the mechanism was also investigated.1.We have developped N-heterocyclic carbene copper catalyzed the C(sp)-C(sp~3)bond formation with terminal alkynes and primary alkyl triflates.The coupling between phenylacetylene and octyl triflate was used as the model and the reaction conditions were optimized.The results showed that in dichloromethane with tAmONa as the base,IMesCuCl as the catalyst,the cross-coupling product can be obtained in good isolated yield under inert atmosphere.Under the optimal conditions,the substrate scope was also examined.The results shows that the aromatic alkynes with electron-donating group exhit higher reactivity.Moreover,alkyl alkyne can also be tolerated in this catalytic system.2.We confirmed that the key intermediate was coppor acetylide in this process,and single crystal X-ray analysis confirmed the structure as [(IMes)2Cu]+[(PhCC)2Cu]+.Stoichiometric reactions and kinetic investigations revealed that coppor acetylide was the active species.We also analyzed other possible species in this process,which provided important information for the mechanism of this transformation.3.N-heterocyclic carbene copper catalyzed direct alkylation reaction of terminal alkynes with secondary alkyl methanesulfonate was also studied.The coupling using phenyl acetylene and octyl methanesulfonate was applied as the model reaction for optimizing the reaction conditions.The current results showed that in toluene with t AmONa as the bese,SIPrCu Cl as the catalyst,50% conversion can be achieved.More works are ongoing to improve the transformaiton.