[Objective]Naphthalene diimide(NDI)is an important precursor for the preparation of various naphthalimide derivatives.The C—X(X=Br,I)directional conversion of naphthalene nuclei not only effectively regulates molecular energy level,but also facilitates controlled assembly between molecules.This method proves to be an effective means for efficiently creating new naphthalimide materials.However,conventional methods for the synthesis of halogenated naphthalimides often suffer from low synthetic efficiency and poor selectivity.Here,the synthesis conditions of dibromonaphthalenetetracarboxylic dianhydride(NDA-2Br)were optimized to improve the synthesis yield.[Methods]The synthesis conditions of brominated NDI were divided into two steps for optimization.Firstly,the bromination reaction was optimized.The reaction vessel was replaced by a pressure bottle suitable for pressurized reaction instead of a round-bottom flask used under traditional conditions to ensure the full reflux of bromine vapor to the greatest extent.The bromine vapor was reacted at 80 ℃ for 12 h.After allowing the reaction solution to cool to room temperature,it was poured into ice water and filtered to obtain an orange solid.Secondly,the solubility of NDA-2Br in acetic acid in the imide reaction was improved by adding the co-solvent dimethyl sulfoxide(DMSO).The products were characterized by nuclear magnetic resonance(NMR)and high resolution mass spectrum(HRMS).[Results]By using pressure resistant bottles as reaction vessels for bromination reactions,the degree of reflux of bromine vapor can be improved.The NDA-2Br obtained is not only of high purity,but also of large amount of synthesis,obtaining about 30 g(yield 92％)at a time.When the volume ratio of DMSO/AcOH is 1∶2,it reacts with 2-ethylhexylamine in an oil bath at 114 ℃ for 1 h,washes with ethanol to remove a few red by-products,and filters to obtain the yellow imide product dibrominated NDI-C2C4.The yield increases significantly.At the same time,the products in the reaction process are also tracked by 1H-NMR spectrum.The results show that dibrominated NDI-C2C4 is the main product,and no nucleophilic byproducts are observed,which is also the reason leading to the significant increase in yield in this step.The optimized synthesis conditions of dibrominated NDI are also applicable to other types of amines.In this experiment,it is found that the imidization results varied with different amine configurations.Compared to the straight chain amine,the branched chain amine has a certain steric hindrance,and therefore the yield of dibrominated NDI-C8C10 is low.In contrast,2,6-diisopropylaniline has a high yield of dibrominated NDI-iPr due to its good solubility.[Conclusion]In this study,a large amount of purer NDA-2Br was synthesized at one time by first enhancing the reflux degree of bromine source in the bromination reaction,and then the solubility of dibrominated NDA in acetic acid was improved in the imide reaction to improve the reaction efficiency and obtain dibromo-NDI products with high yield.Dibromo-NDI is an important precursor of naphthalene ring functionalized naphthalene diimide derivatives,and its efficient synthesis lays an important foundation for subsequent research.
国家科技期刊平台
NSTL
万方数据
维普
