The Study On The Transition Metal-catalyzed Construction Of Oxygen-and Sulfur-containing Heterocyclic Compounds Via C-H Bond Activation

In recent years,transition metal-catalyzed cycloaddition reactions have been recognized as one research hotspots in organic chemistry.Transition-metal catalyzed reactions have attracted the attention of organic researchers due to their unique high selectivity,broad functional group tolerance and high efficiency.As a result,the transition metal-catalyzed C-H activation reactions have made breakthrough progress and become a powerful tool for the construction of complex molecules.Among them,researches on the iridium and rhodium catalyzed C-H activation have made great achievments,due to their outstanding catalytic activities,wide substrate compatibility and functional group tolerance.Therefore,synthons such as diazonium compounds,sulfoxide ylides,salicylaldehyde and naphthylthiol are widely used in transition-metal catalyzed synthesis reactions,especially in the construction of heterocyclic compounds.In this thesis,we developed the rhodium-and iridium-catalyzed synthesis of oxygen and sulfur containing heterocyclic compounds via C-H activation.The main research content is divided into the following two parts:(1)Rhodium-catalyzed synthesis of chromone derivatives from salicylaldehydes and 4-diazoisochroman-3-imines.Salicylaldehyde,as a versatile organic synthesis intermediate,undergoes a [4+2] cycloaddition reaction with 4-diazoisochroman-3-imine under the catalysis of Rh(III),results in various substituented chromone compounds.Chromone and its related derivatives are a relatively important class of heterocyclic compounds in biochemistry which have important biological activities.Generally,common methods for the preparing of chromone were quite strict,with high temperature,high pressure,under inert atmosphere,etc.This reaction is conducted uunder air at room temperature,which represents as a convenient method for substituented chromones.(2)Iridium catalyzed synthesis of thiopyrans from sulfoxide ylides and naphthylthiophenols.Naphtho[1,8-bc]thiopyran is an important sulfur-containing fused aromatic compound due to its various functional properties.However,the synthetic methods of naphtho[1,8-bc]thiopyrans are very limited.Therefore,it is of great significance to develop effective and economically sustainable synthetic methods for such compounds.We developed the iridium-catalyzed cyclization reaction between naphthalene mercaptans and sulfoxide ylides.A variety of 2-arylnaphtho[1,8-bc]-thiopyrans were obtained in moderate to excellent yields.The reaction proceeds successively with cis C-H activation and cyclization of naphthalene,which represents a convenient way to construct naphthalene [1,8-bc]-thiopyran skeleton.