Studies On Cyclization Reaction Involving Diazo Compounds

Diazo compounds resprent a type of very important synthetic intermediates,which demonstrate wide applications in organic synthesis,medicinal chemistry,chemical biology,materials chemistry,etc.After more than one hundred years,the reactions involving diazo compounds are becoming more and more important,they can be effectively used to construct organic compounds containing nitrogen through the process of retention of diazo groups due to their unique chemical structure,they can be also converted to metal carbene with transition and undergo the directly C(sp~2)-H bond functionalization without the need of guiding groups,and other types of tandem reactions.In this thesis,two novel and efficient chemical transformations have been developed about diazo compounds.The specific research contents include the following two parts:(1)Phosphine-Catalyzed[3+2]Cycloaddition Reaction of?-Diazoacetates and??Trifluoromethyl Enones.Aphosphine-catalyzed[3+2]cycloadditionof?-diazoacetatesand?-trifluoromethyl enones has been developed that provides facile access to multisubstituted 4-(trifluoromethyl)pyrazolines in good to excellent yields at room temperature.In addition,a tandem[3+2]cycloaddition/Michael addition is also presented.(2)Gold-catalyzed Chemoselective construction of spirocarbocycles via sequential C-H Functionalization and Dearomatizing of phenolic with o-alkynylaryl-?-Diazoesters.A new synthetic methodology for the concise synthesis of spirocarbocycles derivatives via the Gold(I)-catalyzed cascade C-H functionalization/dearomatization of naphthols with o-alkynylaryl-?-diazoesters has been developed.Various spirocyclic molecules bearing an all-carbon quaternary stereocenter could be obtained by this novel method in good yields under simple and mild reaction conditions(up to84%yield).This cascade reaction realizes two conversions of C(sp~2)-H bond activation and dearomatization at the same reaction site,and leading to the formation of various spirocyclic molecules that is difficult to synthsis.