Borates As A Traceless Activation Group For Intermolecular Alkylarylation Of Ethylene Through Photoredox/Nickel Dual Catalysis

The purpose of organic synthesis is to get the desired target product through various effective synthesis methods from simple and easily available raw materials.As we all know,olefins are not only important chemical raw materials,but also widely exist in various chemical raw materials and pharmaceutical intermediates.Therefore,it is of great significance to realize the conversion of olefins with high added value.Catalytic bifunctionalization of olefins is a common method to realize the conversion of olefins.Two new functional groups are directly introduced into the unsaturated double bond.On the one hand,it can extend the carbon chain,increase the diversity of molecules and shorten the synthesis steps of many complex molecules.On the other hand,it can be efficiently converted into a variety of high-value pharmaceutical intermediates or drug molecules,which has important synthetic application value.Therefore,we should constantly develop new and more convenient and efficient synthesis methods with olefins.We used inylborate pinacol ester,4-bromopyridine and methylcyclohexyl cesium salt as template substrates.The optimum reaction conditions were obtained by screening the photocatalyst,nickel catalyst,solvent,etc.With DMSO as solvent,we determined that the photocatalyst was Ir[d F(CF₃)ppy]₂(dtbbpy)PF₆,Ni Cl₂·DME as nickel catalyst and dtbbpy as ligand in nitrogen atmosphere and under the blue light of 90W,the reaction temperature was controlled between 35^oC and 40^oC with two fans and lamp distance for 24 h,and then the target product was obtained after a series of post-treatment.This reaction avoids the complexity and danger of olefin gas molecules directly used in the reaction.The stable free radicals are generated by the addition of vinylborate pinacol boron ester with methylcyclohexyl radical,and then the brominated pyridine compounds undergo oxidative addition and reduction elimination to form intermediate products without deboronation,which can be rapidly deboronized in the presence of alkaline system to form alkyl arylation products.