Based On The Reaction Of Hexamethyldisilane And Palladium Heterocyclic Intermediate

Organosilanes play an important role in organic chemistry,materials science,and pharmaceutical industry.Therefore,the development of new methods for the synthesis of organosilanes has been widely studied by researchers.At present,the preparation methods of organosilanes mainly include:nucleophilic substitution reaction of grignard reagent or lithium reagent with halosilanes;transition-metal-catalyzed direct silylation reaction of hydrosilane or disilane reagent.In recent years,there were more and more studies on the synthesis of organosilanes using hexamethyldisilane as silicon reagent due to its atom economy and step economy.Compared with other silicon reagents,hexamethyldisilane has the advantages of stable property,low toxicity and insensitivity to air.Our group found that organosilane compounds can be easily and effectively synthesized via trapping palladacycles intermediates.In this paper,the synthesis of organosilane compounds through C,C-palladacycles intermediate coupled with hexamethyldisilane,using hexamethyldisilane as silicon reagent,was introduced in detail.The main research contents were as follows.1.A new method of synthesis of disilylation compounds by reaction of hexamethyldisilane with C(sp~2),C(sp~2)-palladacycle that constructed by2-iodobenzene was developed.The cleavage of C-X bond and activation of C-H bond were realized simultaneously,and the products could used to synthesize carbazole,dibenzothiophene and dibenzothiophene heterocyclic aromatic hydrocarbons.The reaction mechanism was as follows:Initially,C,C-palladacycles intermediate is produced from the oxidative addition of Pd(0)to the C-I bond,and in situ undergoes intramolecular C-H bond activation.Next,C,C-palladacycles intermediate coupled with hexamethyldisilane.Finally,reductive elimination of the C-Si bond to afford various2,2'-bis(trimethylsilyl)-1,1'-biphenyls and regenerates palladium(0)species.2.A palladium catalyzed route for the synthesis of disilylation compounds from C,C-palladacycle intermediate,generated from2-iodobromobenzene or iodobenzene and N-tosylhydrazones,coupled with hexamethyldisilane was proposed.It is proved that o-vinyl bromobenzene is an important intermediate through relevant control experiments.Combined with the literature reports,the possible reaction mechanism was proposed.First,o-iodo bromobenzene or iodobenzene react with N-tosylhydrazones to form o-vinyl bromobenzene intermediates,then formed C,C-palladacyclic intermediate,and finally reacted with hexamethyldisilane to affored various functionalized vinyl silanes.3.A new method for the synthesis of organosilane compounds by the reaction of hexamethyldisilane with palladacycle intermediates,formed by coordination of palladium species with acetyl as guiding group was developed.In this method,the transition metal palladium is coordinated with the directing group to activate the C-H bond and form a transient six membered palladacycles,which interacts with hexamethyldisilane to provide the related N-(2'-(trimethylsilyl)-[1,1'-biphenyl]-2-yl)acetamide compounds.The substrate range is wide with high isolated yield.4.A series of disilicylated compounds were synthesized by adding norbornene into 2-acetylaminobiphenyls to form palladacycle intermediate and reacting with hexamethyldisilane.The possible reaction mechanism was using norbornene to capture the transient six membered ring formed by the directing group coordination with palladium species,a new intermediate of C,C-palladacycle was formed,which realized the activation of the remote C-H bond,and also realized the interannular silylation and ortho-alkylation(or ortho-alkenylation).The yield of the target product is ideal,and the functional group tolerance is good.