Derivatization Of Closo-Dodecaborate Anion[B₁₂H₁₂]^2- And The Study Of The Applications Of The Derivatives

closo-dodecaboratet[B12H12]2-is an icosahedral cage anion,which has a high symmetry.It has unique properties such as extremely high thermal and chemical stability.Its electrons are delocalized over the whole icosahedral cage structure so that it has so called "3D aromaticity" and this delocalization leads to its properties different from those of other materials.This anion attracts more and more attention because of applications in many fields such as BNCT therapy,weakly coordinating anions,materials and catalysis.However,the anion’s stability and symmetry lead to poor reactivity and regio-selectivity,which are challenges in future applications.We have developed several methodologies for making new derivatives and expanding their scope based on mono-amino-closo-dodecaborates.The details are as follows:1.Improvement of an amidation methodology for[B12H11NH3]-and synthesis of amidine,urea and isocyanate derivativesThe amidation method was optimized so that the reactions can be carried out without the use of extra acylation reagents and the yields are much improved.In the meantime,the influence of pH value to the amidated products was studied.In addition,a new kind of derivatives,amidines,were synthesized by using a new methodology we developed which involves the addition of pentafluorobenzoyl chloride.The anion,[B12H11NH3]-,was reacted with aryl isocyanates to afford urea derivatives which were rarely reported before.Furthermore,a novel methodology was developed to synthesize isocyanate-closo-dodecaborate.The method relies on selective fragmentation of N,N-dimethylurea-N’-dodecaborate.2.The closo-dod ecabo rate dianion fused with oxazoles provides 3D diboraheterocycles with selective antimicrobial activityA new methodology was developed to achieve the cyclization of amide derivatives.The method achieves complete conversion at room temperature within 5-10 minutes using iodobenzene diacetate as the oxidant.Finally,the reaction afforded the target products in excellent yields,and the functional group tolerance is high.Additonaly,the substrates were tested for bioactivity.With our new method for the synthesis of diboraheterocycles,we can easily obtain a series of such derivatives,so we investigated the antibacterial properties of these cyclized products.Studies have shown that this class of compounds has a specific strong antibacterial activity against N.gonorrhoe N.The ability of the antibacterial property can be compared to commercially approved drugs.Importantly,this activity is highly selective and the mode of action is currently subj ect of further biological assays.3.Synthesis of nitrilium dodecaborates and the additional transformations of the productsThioamide derivatives of[B12H11NH3]-were synthesized by using Lawesson’s reagent.Subsequently,a part of the thioamide derivatives spontaneously release hydrogen sulfide to provide isonitrile-substituted products.For the thioamide derivatives that do not self-generate the target compounds,we use a Cu(Ⅱ)reagent to achieve this conversion.A preliminary study on the value of such amide derivatives as synthons was carried out,and derivatives such as tetrazoles,amidines and oxadiazoles were obtained by additions or reductions.