The Research Of C-C Bonds Building And Mechanism Studying Under Electrochemical Conditions

Synthetic chemistry has played a crucial role in medicine,energy and other fields.“How to build the C-C bond efficiently”is one of the most important topics in organic synthesis area.For sustainable development,improving atom-economy and step-economy have become the goal of chemists.In this article,we have focused on the electrochemical synthesis methods for building C-C bonds.The C-H bonds of alkanes and arenes could be activated directly,which showed a high step-economy.On the other hand,the H₂ could be the only by-product in the electrochemical oxidative cross-coupling,which is one of the highest atom-economy ways.Meanwhile,in-depth mechanistic researches could also give a strong supporting for designing new reactions.The main results are as follows:1.By using sulfonamides as the redox-mediator,we have achieved the unactivated C（sp³）-H arylation reaction via the hydrogen atom transfer approach.Supported by the in-situ electron paramagnetic resonance technique,nuclear magnetic resonance,theoretical calculation,kinetics experiments and cyclic voltammetry results,the formation,structure and reactivity of N-centered radicals have been revealed and discussed.We believe these mechanistic study methods for radical intermediates could serve as a platform for other electrochemical mechanistic researches.2.According to the electrochemical process,the decarboxylative cross-coupling between N-hydroxyphthalimide（NHP）esters and N-heteroarenes have been achieved.Comparing with previous works,we have developed a catalyst-free electrochemical protocol for the Minisci-type arylation.The NHP ester could be reduced on cathode directly.And our approach is a complement to the Kolbe oxidative decarboxylation.3.Combining the ruthenium-catalysis with electrochemical method,the C-H/O-H（4+2）annulation between the naphthol and alkyne has been developed.It is worth mentioning that the product has a strong fluorescence structure.Comparing with previous reports,this strategy does not need equivalent copper salt as the oxidant,and the H₂ is the only by-product.4.The electrochemical palladium-catalyzed C-H arylation reaction was realized onC4 position of thiophenes.In divided cell,the reduction of palladium catalyst on the cathode was avoided.At the same time,the amount of oxidant could decrease to catalytic amount.Nowaday,the C-H activation of methane or ethane has remained a challenge.If the C-H functionalization of gaseous alkanes could be achieved by electrochemical strategy,it would have a broad development in both laboratory and industrial area.