Study On The Carbon-Hydrogen Bond Boronation Of Indole Compounds Catalyzed By Lewis Acid And Promoted By Br(?)nsted Acid

Aryl borate is an important organic synthetic building block and is widely used in the fields of medicine and materials.In the past thirty years,the boronation reaction of aromatic hydrocarbon carbon-hydrogen bonds has developed rapidly and has become one of the most important synthetic methods of aryl boronic acid esters.Noble transition metal catalysts have the highest catalytic efficiency in aromatic hydrocarbon-carbon-hydrogen bond boronation reactions.In recent years,inexpensive transition metal-catalyzed aromatic hydrocarbon-hydrogen bond boronation reactions have also been widely reported.The aromatic hydrocarbon carbon-hydrogen bond boronization reaction without metal participation,without the use of transition metals,is environmentally friendly,and is a good alternative to transition metal catalytic systems.However,the currently reported non-metallic catalysts are generally expensive or difficult to obtain.Therefore,it is urgent to develop the aromatic hydrocarbon carbon-hydrogen bond boronation reaction involving non-metallic catalysts that are cheap and easily available.This dissertation first reviewed the aromatic hydrocarbon carbon-hydrogen bond boronation reaction catalyzed by transition metals and the aromatic hydrocarbon carbon-hydrogen bond boronation reaction without metal participation.By investigating the literature related to the indole carbon-hydrogen bond boronation reaction,combined with the relevant research background of this research group,we have realized two types of indole selective carbon-hydrogen bond boronation reactions involving indole derivatives with cheap and easily available catalysts.The synthesis provides an efficient and simple method.The main results are as follows:1.Selective carbon-hydrogen bond boronation at the C3 position of indole catalyzed by zinc trifluorosulfonate.Under the action of low catalyst equivalent of zinc trifluoromethanesulfonate,the indole compound reacts with pinacol borane to obtain the corresponding indole C3 boronation product.According to related mechanism experiments,we speculate that the reaction is carried out through the electrophilic boronization reaction mechanism.2.Benzoic acid promotes the selective carbon-hydrogen bond boronation reaction at the C2 position of indole.Under the promotion of benzoic acid,the indole compound reacts with pinacol borane to obtain the corresponding indole C2 boronation product.According to related mechanism experiments,we speculate that the active catalytic species of this reaction is the borane produced by the decomposition of HBpin.