Study On Transition Metal Catalyzed Method For Conversion Of Unsaturated Substrate

Transition metal catalyzed conversion of unsaturated substrates has received extensive attention as a frontier of modern organic synthetic chemistry.The transition metal-catalyzed conversion of unsaturated organic small molecules into functional molecules with specific functions is of great significance for both theoretical and applied research.In this paper,the transition metal copper or ruthenium-catalyzed unsaturated substrate conversion method was studied.Cu(I)-catalyzed diastereoselective carboboration of ?-alkyl-substituted ?,?-unsaturated carboxylic esters to produce ?-boryl-?-quaternary carbon carboxylic esters were developed.At the same time,two kinds of different ring-switching metathesis transition metal ruthenium catalysts were also constructed,and the application of the catalytic ring-closing metathesis reaction in organic synthesis was studied.The following is the main research content of this paper:(1)In order to screen ligands,solvents,and bases,firstly,the transition metal copper catalyzed reaction of ?-aryl-?-methyl-?,?-unsaturated carboxylic acid methyl ester 1a and electrophilic reagent(allyl bromide)is used as a template reaction.Finally,we chose toluene as a suitable reaction solvent,4-bis(diphenylphosphinoethane)(dppe)or dicyclohexylphosphino-2',6'-dimethoxybiphenyl(Sphos)as suitable Phosphine ligand,KOMe as a suitable base.(2)The applicability of various effective electrophiles(including dialkyl sulfates,primary allyl halides and benzyl bromide)and various ?-(hetero)aryl substituents or linear ?-alkyl substituents ?-alkyl-?,?-unsaturated carboxylic acid methyl ester substrate to the reaction were investigated.At the same time,the mechanism of the carboboration reaction were inferred and verified.The results show:The carbon skeletons of dialkyl sulfates,primary allyl halides,and benzylbromides were transferred to the ?-position of the substrates to provide products in moderate to good yields with diastereoselectivity >95% in most cases.Substrates bearing a ?-(hetero)aryl substitutent give higher diastereoselectivities than those bearing a linear ?-alkyl substitutent.The reactions probably go through an copper(I)enolate intermediate and the diastereoselectivity arises from the electrophilic attack of electrophiles to the less hindered side of the enolates.(3)We chose magnetic ferroferric oxide nanoparticles as carriers and connected the carriers to the second-generation Grubbs type catalysts by ligands containing different structural linking chains to access the supported ruthenium catalyst A with a nitrogen-containing heterocyclic linking chain and the supported ruthenium catalyst B containing a nonpolar aprotic alkane chain.(4)Catalysts A and B were respectively used for the ring-closing metathesis reaction of different types of substrates to investigate the application of the catalytic ring-closing metathesis reaction in organic synthesis.The results show that it is very easy to synthesize 5- or 6-membered(hetero)ring compounds with substituents under the action of catalyst A or B,and the yield is as high as 80% or more.