The Construction Of Carbon-Carbon Bonds Via The Reactions Catalyzed By Metal Triflates

In recent years,a wide variety of reactions using Lewis acids as catalyst have received a great deal of attention.However,in some cases,the traditional Lewis acids still suffer some shortages,such as poor catalytic activity and selectively.Furthermore,these Lewis acids are moisture sensitive and easily decomposed or deactivated in the presence of even a small amount of water.Therefore,the development of efficient and stable novel Lewis acid is warmly expected.Due to their unique thermodynamic,chemical stability and catalytic activity,metal triflates have been regarded as a new type of Lewis acids and widely applied in a serious of organic reactions.Meanwhile,the development of efficient C-C bond forming process is an importance topic in organic chemistry.Our research mainly concentrates on designing the multi-component reactions and allylation reactions catalyzed by triflate metals to construct new carbon-carbon bonds.As a starting point,multi-component cascade reactions catalyzed by Sc(OTf)3 were developed.A novel approach for the three-component one-pot synthesis of N-substituted 3-oxoisoindoline-1-carbonitrile derivatives has been developed through a Sc(OTf)3-catalyzed Strecker/Lactamization cascade reaction involving methyl 2-formylbenzoate,amines and TMSCN.This protocal was conducted with 2.5 mol%catalyst and up to 97%yields were obtained.The methodology also had distinct advantages of easily accessible starting materials,operational simplicity and good functional group tolerance.Furthermore,new C-C bond and C-N bonds were constructed in this process.Next,multi-component cascade reactions catalyzed by In(OTf)3 were conducted.N-substituted 3-oxoisoindoline-l-difluoromethylene derivatives were synthesized via a Mannich/Lactomization cascade reaction employing 2-carboxybenzaldehyde,amines and difluoroenoxysilane as starting materials.The reaction proceeded smoothly in the presence of In(OTf)3,constructing new C-C bond and C-N bonds and affording a broad scope of isoindolinones with up to 86%yields.The N-p-methoxyphenyl group of isoindolinones could be oxidatively cleaved using ceric ammonium nitrate to form protecting group free isoindolinones,thereby making this methodology more useful for further transformations at the NH position.The oxidative allylation catalyzed by Cu(OTf)2 was explored for the synthesis of homoallylic amines.A facile approach for Cu(OTf)2-catalyzed oxidative a-allylation of glycine derivatives has been established using oxygen or tert-butyl hydroperoxide as oxidant.The selective oxidation of a C-H bond of glycine derivatives generate a reactive imine intermediate,which could be activated by Cu(OTf)2 for the nucleophilic attack of allyl regant,thus furnishing a new C-C bond.Various glycine esters and glycine amides were suitable substrates for this oxidative allylation reaction and afforded the desired a-allyl glycine deravatives in 41-73%yields.Experimental observations revealed that Cu(OTf)2 not only activated the imine intermediate for the nucleophilic attack,but also involved in the oxidation process of glycine esters.Finally,the asymmetric allylation cayalyzed by In(OTf)3 was also investigated.Together with Imidazolylpyridine ligand,In(OTf)3 can efficiently catalyse the asymmetric allylation of ketimines derived from isatins.Thus a new and stereoselective C-C bond was formed in this processes.This protocal was conducted with 2.5 mol%catalyst and ligand at room temperature without any additives and afforded the 3-allyl 3-aminooxindoles with good yields and moderate to excellent enantioselectivities(up to 97%ee).In addition,the major configuration of the product was assigned as S by X-ray crystallographic analysis.