The Study Of Rh(?) Catalyzed C-H Activation,C-C Coupling And Annulation Reactions

Transition metal-catalyzed C-H functionalization has become a prominent and indispensable tool in organic synthesis.In recent years,the catalytic properties of the ? transition metals?eg,rhodium,palladium,cobalt,etc.?have received extensive attentions.The first chapter simply reviews the transition metal-catalyzed C-H bond functionalization history and the current status of the field.This chapter classifies the reactions of various of direct groups with olefins,alkynes,diazo compunds,aryl iodides and other coupling reagents.In the second chapter,we report Rh???-catalyzed,N-amino?hydrazine?-directed C-H functionalization with ?-diazo-?-ketoesters for the access to cinnoline scaffold.A diverse set of non-discriminating conditions obtained for a highly efficient test transformation prompted use of a substrate-replacement?SURE?technique for in-depth search in experimental parameter space and pinpointing of the optimized condition.Furthermore,the mechanism of this reaction system was examined by hydrogen-deuterium exchange experiments and kinetic isotope effect?KIE?studies.This high KIE value indicated that the C-H activation step was likely rate-determining in the catalytic process.In our previous work,the mechanism of C-H activation step of 1-alkyl-1-phenylhydrazine substrates was well investigated.Based on this understanding and the observations in the mechanism studies,we proposed a mechanism of this reaction using 1-alkyl-1-phenylhydrazines and 2-diazo-3-oxobutanoate as the model reactants.Initially,the rhodium catalyst dimer experienced a ligands exchange to form a reactive acetate rhodium species.Then it was coordinated by the amino group of the substrate 1-alkyl-1-phenylhydrazines,and activated the ortho C-H bond of the directing group to generate the rhodacycle complex,a species already identified in our previous report.Then the diazo compound 2-diazo-3-oxobutanoate formed a carbene species,bound to rhodium atom,and inserted into the Rh-C bond.Through ligand exchange with acetate compounds,the catalytic cycle was completed,and a C-C coupling product was formed leading to the end product by an easy dehydration process.The third chapter describes the use of diazophosphate in Rh???catalyzed reaction with enaminone substrates.The alkylated derivatives of the product were annulated using a solution of 5.0 equiv tBuONa and 1.0 equiv H₂O in tetrahydrofuran to give the novel 4-hydroxy-1-naphthoic acid derivative.The reaction conditions are mild,efficient and compatible with a wide range of substrates.