Research On The Intramolecular Aryl-carbocyclization Of Diynes Initiated By Diaryliodonium Salts

Polycyclic compounds widely exist in natural products,pharmaceuticals and opto-electronic materials.Thus the methodology of building cyclic backbones is very worthy of being studied.During the past few decades,various methods have been well established to construct polycyclic compounds:pericyclic reaction such as Diels–Alder reaction with alkenes or alkynes,radical cyclization such as Bergman reaction,ionic cyclization such as electrophilic cyclization reactions.Among these methods,electrophilic cyclization has been one of the most efficient ways to synthesize cyclic compounds because of its step economy and high efficiency.These electrophilic cyclization reactions featured mild conditions,simple operation and easily available linear substrates.Thus,many electrophiles were explored by researchers to promote cyclization,such as H~+,Lewis acids,halogen,etc.However the employment of carbon-electrophile to initiate the cyclization is rarely reported.Diaryliodonium salt is a new generation of carbon electrophilic reagent with high electron deficiency.Diaryliodonium salt is easy to prepare and stable in the air,and it also has high reactivity in the reaction.In this thesis,in order to construct new carbo-rings,various easily obtained diynes were designed.Diaryliodonium salt were used to initiate the carbo-cyclization with the diynes.As a result,aryl-carbo-rings were formed and two parts of related work were done as listed below:Based on precedent research of cyclization reactions triggered by diaryliodonium salts,the linear diyne substrate such as 1,6-diyne and 1,7-diyne could form the vinyl carbocation twice during the cyclization which consequently opens up the possibility to build up polycyclic backbones.Initiated by diaryliodonium salt with copper catalyst,six or seven membered ring-fused indene backbones were formed.The mechanism was proposed as follows:aryl cation is formed through the electrophilic addition of copper species by diaryliodonium salts.Then aryl cation is attacked by the alkynyl group of the diyne to form a vinyl-cation center.Then the vinyl-cation center is attacked by the other alkynyl groups in the same molecule to give a new electrophilic center.Subsequently,the electrophilic center undergoes a Friedel-Crafts type reaction to produce the target product.Further study on diyne was done by this thesis.When the diyne1,2-diethynyl-4,5-dimethylbenzene was used,by using diaryliodonium salts and relevant solvent,the aryl-halogen-carbocyclic naphthalene derivatives were formed in the reaction.The halogen were proven to come from the solvent.A new type of Bergman cyclization might happened in this reaction.Two type of aryl-carbo-rings were formed by diaryliodonium salts initating cylization with diynes.This method gave hint on exploring new substrates and new type of hypervalent iodine to construct cyclic compounds.