Lewis Acid-Catalyzed C-H Silylation Of Indoles And Synthesis Of Silicon-Polymer Materials

Owning to the very useful physicochemical properties of silylated indoles,various synthetic strategies have been developed to synthesize regioselective silylated indoles in last 20 years.However,the high-efficiency catalytic systems are mainly based on transition metals.In general,metal-based catalyst is required for C–H silylation or excessive hydrogen acceptors or additives is necessary for achieving enhanced catalyst turnover,which restricts these synthetic methods from their practical applications.Therefore,it remains as challenging task for people to develop a general synthetic method to overcome such limitations for preparation of silylated indoles.A metal free B（C₆F₅）₃–catalyzed approach is developed for disproportionation reaction of a series of indoles with various hydrosilanes,without any additives such as base and production of any small molecule such as dihydrogen.This boron catalyst system also exhibits excellent catalytic performance for practical application,such as catalyst loading as low as 0.01 mol%under solvent free condition,and a long life catalytic performance highlighted by maintaining a constant catalytic activity and achieving excellent yields for desired products over ten sequential addition of starting materials.Based on characterization of key intermediates through a series of in–situ NMR reactions and detailed experimental data,we proposed reaction mechanism which illustrated pathways for the formation of different products,including both major products and byproducts.Additional control experiments were conducted to support our proposed mechanism.Understanding of mechanism enable us to successfully suppress side reactions by choosing appropriate substrates and hydrosilanes.More importantly,the use of elevated reaction temperature for continuous oxidation of resulted indoline to indole makes the convergent disproportionation reaction an ideal atom-economical process.Research on the catalysis of B（C₆F₅）₃,a method for the Al（C₆F₅）₃-catalyzed silylation of indoles is introduced,which was found to initiate the C-H silylation of indoles with hydrosilanes.This new catalytic system shows a higher tolerance for a wide range of indoles.This reaction features simple and neutral reations conditions,exclusive C3-selectivity,wide substrate scope and no additives and H₂ acceptor.Characterization of key reaction intermediates through a series of in–situ NMR reactions and detailed experimental data led to the proposed reaction mechanism which illustrated the pathways for the formation of silylated indoles.Additional control experiments were conducted to support our proposed mechanism,which achieved thermally induced frustration Al/N FLP catalytic C-H silylation reactions.The thermally induced system can inhibit the occurrence of C5-silylated and C3,C5-disilylated indole reactions,simultaneously,efficiently synthesize C3-silylated products.We used B（C₆F₅）₃–catalyzed approach to successfully achieved the synthesis of polymers containing indole and silane in the main chain,completing the transition from organic synthesis to polymer synthesis chemistry.First we synthesized a series of indoles and silanes.Then,we studied several model reactions and synthesized several indole or silane-based small molecules,that optical properties were characterized.Finally,we obtained different types of indole and silane polymers by introducing indole and silane into one molecule at the same time,or synthesizing bis-indole and bis-silane.The polymer has better thermal stability.What’s more interesting is that the polymer emits blue light under the irradiation of ultraviolet light,due to the acceptor structure of indole and silane,Therefore,This is nice potential blue light polymer materials.