Research On The Synthesis Of Energetic Compounds Based On Adamantane Skeleton

High energy-density cage-like compounds have attracted extensive attention for their high energy and low sensitivity owing to their symmetrical structures,particularly in combination with good thermal stability.The energetic compounds based on adamantane skeleton,including polynitroadamantanes and polynitroazaadamantanes,have the advantages of high energy and insensitivity.It is expected that high energy-density materials with excellent properties will be developed by futher study on these compounds.Herein,recent progress of the development of high energy-density compounds,the synthesis of polynitroadamantanes and polynitroazaadamantanes were reviewed.Then,in view of the influence of high steric hindrance in the synthesis of polynitroadamantanes,the method of synthesizing adamantane with gem-dinitro group from nitroadamantane under steric hindrance condition was designed;on the other hand,the fluorine atom,with smaller steric hindrance,was used to replace nitro group to synthesize fluorine-containing polynitroadamantanes.In addition,a new route was attempted to synthesize1,2,2,3,5,6,6,7-octanitroadamantane,and finally one of diazaadamantane and its derivative were prepared.The reaction system of preparing 2,2,4,4-tetranitroadamantane from2,2,4-trinitroadamantane was studied.The optimal reaction conditions were determined and the highest yield was achieved as high as 87%.Sodium nitronates was directly converted into gem-dinitro products through a new nitrosation and oxidation tandem process.The reaction system has been applied to several polynitroadamantanes and arylnitroalkanes with good applicability of substrates.Finally,the reaction mechanism was studied,and it was confirmed that the reaction was a free radical reaction process.2,6-Difluoro-2,4,4,6-tetranitroadamantanewassynthesizedfrom4,4-dinitroadamantane-2,6-dione via oximation,oxidation and electrophilic fluorination.The crystal density of 2,6-difluoro-2,4,4,6-tetranitroadamantane was 1.787 g·cm^-3.2,4,6,8-Tetrafluoro-2,4,6,8-tetranitroadamantane was prepared in eight steps from4,8-dihydroxyadamantane-2,6-dione.Subsequently,the thermal stability of2,6-difluoro-2,4,4,6-tetranitroadamantane,2,4,4,6-tetranitroadamantane,2,4,6,8-tetrafluoro-2,4,6,8-tetranitroadamantane and 2,4,6,8-tetranitroadamantane were studied by thermogravimetric analysis and differential scanning calorimetry(TG-DSC),and their detonation properties and densities were calculated by using the Gaussian 09program.Finally,the influence of substituting groups of fluorine,hydrogen and nitro group in the framework of adamantane on the properties was discussed.2,6-Dioxane-1,3,5,7-tetracarboxylic acid was synthesized from diethyl malonate and polyformaldehyde via cyclization and hydrolysis.Two routes were designed to synthesize1,3,5,7-tetranitroadamantane-2,6-dione based on this tetracarboxylic acid,but both routes failed.Subsequently,the synthesis of nitroalkanes from aliphatic carboxylic acids catalyzed by metal was studied in detail for one-step synthesis of tetranitroadamantane from tetracarboxylic acid.The key intermediate of 9-(tert-butoxycarbonyl)-9-azabicyclo[3.3.1]nona-2,6-diene was synthesized from 1,5-cyclooctadiene via two routes.Subsequently,2,4,4,6,8,8-hexanitro-2,6-diazaadamantane was synthesized in nine steps.The crystal density of 2,4,4,6,8,8-hexanitro-2,6-diazaadamantane was 1.959 g·cm^-3 and the thermal stabilityofthecompoundwasstudiedbyTG-DSC.2,4,4,6,8,8-hexanitro-2,6-diazoadamantane has a decomposition peak temperature of276?,calculated detonation pressure of 40.3 GPa and detonation velocity of 9310 m·s^-1,which makes it possible to be used as high energetic materials.In this paper,a method for the synthesis of adamantane bearing gem-dinitro groups from nitroadamantane was developed.Two fluorine-containing polynitroadamantanes,2,6-difluoro-2,4,4,6-tetranitroadamantane and 2,4,6,8-tetrafluoro-2,4,6,8-tetranitro-adamantane,weresynthesized.Anewsynthesisrouteof1,2,2,3,5,6,6,7-octanitroadamantane and a method of preparing nitroadamantane from alkyl carboxylic acid were explored,which established the foundation of the synthesis of the adamantanes containing more nitro groups.Finally,a method of constructing the skeleton of2,6-diazzadamantanewasdeveloped.Thereafter,2,4,4,6,8,8-hexanitro-2,6-diazaadamantane was synthesized,which provided a template for the synthesis of other energetic cage-like compounds.