2,5-二溴甲基对苯二甲腈的合成

以对二甲苯为原料,分别通过芳环上的溴代、亲核取代及α-位溴代3步反应,合成了2,5-二溴甲基对苯二甲腈。以碘作催化剂,对二甲苯与液溴在二氯甲烷中于12℃严格避光条件下搅拌反应18 h,得到2,5-二溴对二甲苯;2,5-二溴对二甲苯与氰化亚铜在DMF中加热回流48 h得到2,5-二甲基对苯二甲腈;2,5-二甲基对苯二甲腈与N-溴代丁二酰亚胺(NBS)在四氯化碳中被偶氮二异丁腈催化反应16 h得到2,5-二溴甲基对苯二甲腈,各步收率分别为96.3%、87.5%、31.4%。借助正交实验优化了各步的反应条件:溴代n(B r2)∶n(p-xylene)=2.2∶1,c(p-xylene)=3.2 mol/L,反应温度12℃,反应时间18 h;亲核取代n(CuCN)∶n(2,5-二溴对二甲苯)=2.5∶1,c(2,5-二溴对二甲苯)=0.2 mol/L,反应温度155℃,反应时间48 h;α-位溴代n(NBS)∶n(2,5-二氰基对二甲苯)=2.1∶1,c(2,5-二氰基对二甲苯)=0.1 mol/L,反应温度80℃,反应时间16 h。并对各步产品进行了质谱和核磁共振氢谱表征。

Synthesis of 2,5-Bis(bromomethyl)-terephthalonitrile

2,5-Bis(bromomethyl)-terephthalonitrile(Ⅰ) was synthesized from p-xylene by aromatic bromination,aromatic nucleophilic substitution and α-bromination.Reaction conditions of each step were optimized by means of orthogonal experiments.Thus,p-xylene dissolved in CH_2Cl_2(3.2 mol/L) reacted with dropping bromine(n(Br_2)∶n(p-xylene)=2.2∶1) in the presence of trace iodine as catalyst under vigorous stirring and absolute exclusion of light at 12 ℃ for 18 h to form 2,5-dibromo-p-xylene(Ⅱ) in 96.3% yield.Then Ⅱ reacted with CuCN in DMF(n(CuCN)∶n(Ⅱ))=2.5∶1,conc.of Ⅱ=0.2 mol/L) under reflux for 48 h(refluxing temperature 155 ℃) to afford 2,5-dimethylterephthalonitrile(Ⅲ) in 87.5% yield.Finally,Ⅲ and N-bromosuccinimide(NBS) in CCl_4(n(NBS)∶n(Ⅲ)=2.1∶1,conc.of Ⅲ=0.1 mol/L)in the presence of azoisobutyrodinitrile were stirred and refluxed at 80 ℃ for 16 h to afford Ⅰ in 31.4% yield.All products were characterized by MS and NMR.