Study On The Catalyzed Reductive Heck Reactions Via Palladium Complexes Of Bidentate Nitrogen Ligands

Pd-catalyzed Heck reaction has been wildly applied in organic synthesis as one of the most efficient ways to synthesize substituted alkenes.In the catalysis mechanism,a syn migtory insertion of alkene into the Ar-Pd bond and the subsequent?-H elimination were assigned as the key elementary steps during the whole catalytic cycle.In the Heck reaction,olefin provided the alkenyl source to couple with aryl or vinyl electrophiles could deliver a?-Pd-alkyl intermediate.This intermediate exhibited short lifetimes,which could construct C(sp~2)-C(sp~3)for further functionalization.The strategy of reductive Heck reactions were provided a feasible way to trap the?-Pd-alkyl species and then constructed C(sp~2)-C(sp~3),so had received great attentions.At first,reductive Heck reaction is the cross-coupling between olefins and aryl halides.Recently,although had developed a series of reductive cross-coupling reactions of olefins with aryl mental reagents,aryl diazonium salts,ArOTf or ArOTs,constructed C(sp~2)-C(sp~3)by reductive Heck reactions,while some limitations and challenges still exist.In this thesis,based on the palladium complexes of bidentate nitrogen ligands,Pd-catalyzed intermolecular reductive Heck reaction was studied,which construct C(sp~2)-C(sp~3)bonds successfully,and the reaction mechanism was also investigated.The research progress into two aspects as follow.1.Palladium complexes of bidentate nitrogen ligands catalyzed the C(sp~2)-C(sp~3)bond formation with olefins and aryl bromides.The cross-coupling reaction between p-methylstyrene and bromidebenzene as the model and the reaction conditions were optimized.The results showed that i-PrOH as the solvent and reductant,KOH as the base,palladiun complexes of bidentate nitrogen ligands as the catalyst,linear reductive cross-coupling product could be obtained selectively.And then under the optimal conditions to expand substrates,various aromatic olefins and arylbromides all obtained great results;In addition,aliphatic olefins could also be used in this reaction system.2.By the kinetic and deuterium labeling experiment,the reaction produced the Heck product,then the Heck product was reduced to the target product under Pd/i-PrOH conditions,and direct protonolysis of the?-Pd-alkyl intermediate by i-PrOH to the target product,which these two processes were eliminated.Then proposed alcoholysis of the?-Pd-alkyl intermediate under the Pd/KOH conditions and the following?-H elimination step resulted to the formation of C(sp~3)-Pd-H species,which finally occurred reductive elimination for the possible reaction mechanism.