Design And Synthesis Of Novel Spirocyclic NHC-Ir Complexes And Its Application In Isomerization Of Olefins

Olefin structures widely present in active natural products and pharmaceutical molecules,and their E/Z configuration has an important effect on the chemical and biological properties and functions.Therefore,the construction of olefins with high stereoselectivity is one of the researches focuses in organic synthetic chemistry.However,the classical construction methods of olefin(such as Wittig reaction and HWE reaction)often result in a mixture of E and Z olefins due to the poor selectivity.It is difficult to separate the two mixtures into a pure product with single configuration.In recent years,olefin isomerization reactions with high atom economy have been developed from simple and easily available terminal olefins to produce poly-substituted olefins through C=C bond migration.Among them,the development of new transition metal catalyst systems has been widely used in the isomerization of olefins,but most of the catalyst systems still possess the disadvantages of low stereoselectivity and poor regioselectivity.Therefore,it is still of great significance and value to develop a novel,efficient,and controllable olefin isomerization system.This paper has investigated the development of the synthesis of efficient olefin isomerization catalysts.In order to obtain the metal-catalyzed construction of olefins with single configuration,a novel type of olefin isomerization methodology was first designed and developed,inspired by the recently development of N-heterocyclic carbene(NHC)metal complexes in our group.Starting from spiro-[4,4] nonane-1,6-dione,a new type of iridium complexes with spirocyclic carbene structure were successfully synthesized after a series of transformations.By employing these coordination complexes as a core,we have successfully carried out iridium-catalyzed olefin isomerization studies,and completed the construction of several olefins with high stereoselectivity,nearly the complete E configuration achieved.This paper is divided into three parts: 1.Overview of olefin isomerization progress;2.Design and synthesis of new N-heterocyclic carbene iridium complexes;3.Reaction investigation of olefin isomerization catalyzed by NHC-Ir complexes.Chapter One,briefly introduced the progress of positional and geometrical isomerism of olefins.Chapter Two,introduced the background of the N-heterocyclic carbene complex,designed and synthesized a new type of NHC-Ir complex,and completed its structural characterization.Chapter Three,synthesized a series of E-type olefin compounds with an E selectivity of up to 99: 1 ratio and 90% yield,and conducted some explorations on the substrate scope by using the above catalysts and catalysts previously developed by our group.