Studies On Constructing C-C Bonds By Transition Metal Rh(?)-Catalyzed C(sp~3)-H Bond Activation

Transition metal-catalyzed direct functionalization of C–H bonds activation has the advantages of reducing reaction steps,minimising by-products and improving atom utilization.This strategy can be applied in many fields such as drug syntheses,natural product syntheses and chemical production.In the past two decades,the research on C–H bond functionalization reaction has developed rapidly.Especially the research on C?sp²?–H bond functionalization has achieved more results.However,the activation of the C?sp³?–H bond is relatively slow,mainly due to the small polarity,high bond energy,and poor selectivity of the C?sp³?–H bond.The research on transition metal-catalyzed C?sp³?–H bond functionalization will be carried out in this paper.The main research contents are as follows:Firstly,Rh???-catalyzed oxidative cross-coupling of C?sp³?–H bonds with C?sp²?–H bonds has been accomplished under mild conditions.8-Methylquinolines have good tolerance for different substituents such as alkyl,halogen,nitro,etc in this reaction.The quinones and thiophenes show good reactivities by changing the solvent and temperature in the reaction.The result of the scale-up experiment indicates that this reaction can be used for scale-up synthesis.Quinones and thiophenes are two important types of building blocks existing frequently in natural products,biologically active molecules,and functional materials.The coupling reaction between these two types of compounds and 8-methylquinolines opens up new ways for their derivation and utilization.On the other hand,we have successfully developed an efficient Rh???-catalyzed protocol for the direct oxidative cross-coupling reaction of the C?sp³?–H bonds with maleimides providing the Heck-type products.In this catalytic system,the combination of Cu?OAc?₂,TEMPO and oxygen as the oxidant plays a vital effect to accomplish this transformation.The reaction is suitable for different types of maleimides,and the reaction yield is up to 97%.In order to understand the reaction mechanism,the kinetic isotope effect?KIE?experiments were conducted and the results indicates that the C–H bond cleavage of8-methylquinoline may be the rate-determining step of the whole reaction.And we conducted a preliminary study on the process of dehydrogenation to form Heck-type products.The establishment of the catalytic system provides a new way for the derivation of maleimides.