Palladium-catalyzed Sp~2 C-H Olefination Reactions

Transition metal catalyzed sp2 C-H functionalization of arenes/alkenes is an important method for the construction of carbon-carbon bonds and various carbon-hetero bonds.The discovery and development of this methodology greatly enriched the synthetic methods of natural products and molecules with high bioactivity,which was undoubtedly significant in synthetic chemistry.In this thesis,a couple of transition-metal-catalyzed arenes/alkenes sp2 C-H bond olefination reactions have been studied.It is mainly carried out in the following three parts:1.We have developed the oxidation coupling reaction of a series of O-acetyl cyanohydrins with the electron-deficient olefins under the catalysis of palladium acetate.The advantages of the reaction contained simple operation,mild condition,good substrates compatibility and high regioselectivity with good yields to obtain the target coupling products.However,for the substrates,when there were no substituents on the ortho site of the the directing group,we obtained a mixture coupling products of mono-and di-olefination on ortho-position of the directing group.In addition,the yield of the coupling products is lower when the coupling reagents are easily oxidized under our standard condition like acrolein.After inquiry experiments on directing groups,we found that the regioselectivity of such reactions was regulated by the synergistic effect of acetoxy group and cyano group,and this concept had never been reported before.2.We have reported a series of palladium catalyzed oxidation coupling reactions between ordinary linear homoallylic alcohols and alkenes.The methodology did not require gas protection,easy operation,mild conditions,well substrates compatibility and can tolerate a variety of functional groups.We could obtain high stereoselective conjugated dienes with good yields.Homoallylic alcohols could be coupled not only with electron-deficient olefins,but also for neutral coupling agents,such as vinyltrimethylsilane.Through experiments,we found that allyl alcohols and pent-4-en-l-ols were also able to obtain target coupling products under our standard conditions,but the yields were lower than homoallylic alcohol.3.We have investigated palladium(Ⅱ)-catalyzed oxidative coupling reactions of a series of sulfonyl protected homoallylic amines with N,N-dimethylacrylamide.The research was further divided into two parts.The first part was a series of substrates without substituent on the same carbon connected with p-toluenesulfonamide coupled with N,N-dimethylacrylamide to obtain a series of conjugated dienes with purestereoselectivity,which were racemic.By mild reaction conditions,a wide range of products with high yields and high stereoselectivities;The second part was the homoallylic amines with substituents on the carbon connected with p-toluenesulfonamide coupled with N,N-dimethylacrylamide to obtain conjugated dienes with high enantioselectivity and purestereoselectivity and enantioselective substrates.That had achieved the kinetic resolution of homoallylic amines to a certain extent.The synthesis of 1,3-butadienes with high enantioselectivity by oxidative coupling has never been reported.This methodology has a great potential application in organic synthsis.However,the yield of 1,3-butadiene compounds with high enantioselectivity were not high,which needs further study.