Study On Allylation Of Palladium-rhodium Dual Catalytic Reaction System

In past decades,the single catalyst reaction system has been studied extensively and applied in a large number of new reactions successfully.And its mechanism has been clearified.Recent years,palladium-rhodium bimetallic reaction system has been exploited as an efficiently synthetic strategy and has appealed synthetic chemists gradually.Dual metal system is able to realize the reaction transformation,which is difficult to occur or hard to be synthesized in the traditional single catalytic reaction system,therefore,could form novel skeletons with active substrates.In this thesis,Pd-Rh cooperative and asymmetric relay dual catalysis has been further studied,especially the reaction mechanism.At the same time,two highly-reactive intermediates was combined,included rhodium carbene formed by carbene precursors and ?-allyl palladium complex formed by Pd(0)catalyst reactedwith allyllic esters.Based on the compatibility of dual catalyst and the concept of bimetallic catalyst,the author has designed different types of reaction that to broaden the application of Palladium-Rhodium dual catalytic reaction system in organic synthesis.This thesis mainly studied palladium-rhodium synergistic dual catalysis and palladium-rhodium asymmetric relay dual catalysis.1.Pd-Rh synergistic dual catalysis is a process in which compatible dual metals of palladium and rhodium can independently catalyze and activate of nucleophiles and electrophiles to form activated species,respectively,finally combine to form desired products.Based on the two active intermediates,?-imine rhodium carbene complex from N-sulfonyl-1,2,3-triazole and ?-allyllic palladium complexes from esters,the author designed the palladium-rhodium synergistic dual reaction.The bimetallic synergistic catalytic reaction system,N-(4-methylbenzenesulfonyl)-1,2,3-triazole and allyl benzoate were used as template reaction substrates.After screening and investigating the reaction conditions of rhodium catalyst,ligand,palladium catalyst,reaction solvent,etc.,the optimal reaction conditions of the reaction were secured.Under the best reaction conditions,47 of(Z)-configuration multi-substituted enamine were synthesizedin the yields of 23-89% and stereospecifically.The research of reaction mechanism revealed that the Pd(0)/xantphos catalytic system is not only able to to form the target products,but it will further catalyze the conversion and rearrangement of target products.When the reaction time was excessively extended,the reaction yield descreased,or the target product was lost.2.Beta-lactam is a kind of maternal skeleton structure which plays an important role in pharmaceutical molecules with important physiological activity.The synthesis of lactams containing chiral quaternary carbon center is always a challenging subject.In this chapter,a palladium-rhodium asymmetric relay dual system has been designed for the synthesis of beta-lactam compounds,containing chiral quaternary carbon.N-benzyl-N-tert-butyl benzoyl acetamide diazo and allyl carbonate ester were chosen as the template reaction substrates.Under the optimal reaction conditions,38 chiral beta-lactam compounds were synthesized by using differently substituted diazo compounds and a range of allyllic carbonates with excellent yield(up to 99%)and stereoselectivity(up to 99:1 dr,up to 98% ee).The reaction mechanism revealed that the reaction was rhodium-catalyzed asymmetric benzyl C-H insertion reaction followed by a series of palladium-catalyzed allylation reaction.Moreover,the effect of chiral induction of the reaction was determined by the asymmetric rhodium catalyst solely.