3,5-二甲基-4-溴碘苯和2,6-二甲基-4-溴碘苯的合成

Synthesis of 3,5-Dimethyl-4-bromoiodobenzene and 2,6Dimethyl-4-bromoiodobenzene

二甲基对溴碘代苯是带有两种不同卤素基团的芳香族有机合成中间体。2,6-二甲基苯胺在过碳酸钠作用下,于45～50℃与碘反应1 h,得到2,6-二甲基-4-碘苯胺,收率42.5%。2,6-二甲基-4-碘苯胺在-5～0℃下进行重氮化,进一步与溴化亚铜发生Sandmeyer反应,得到3,5-二甲基-4-溴碘苯,收率31.5%。2,6-二甲基苯胺室温下与六亚甲基四胺溴络合物反应30 min,得到2,6-二甲基-4-溴苯胺,收率62.0%。2,6-二甲基-4-溴苯胺在-5～0℃进行重氮化,与K I反应,得到2,6-二甲基-4-溴碘苯,收率33.1%。通过熔点、红外光谱和核磁共振氢谱对中间体2,6-二甲基-4-碘苯胺、2,6-二甲基-4-溴苯胺以及最终产物3,5-二甲基-4-溴碘苯和2,6-二甲基-4-溴碘苯进行了表征。

Dimethyl-4-bromoiodobenzenes are aromatic organic intermediates used in many fields. In the presence of sodium percarbonate,4-iodo-2,6-dimethylaniline was obtained in 42. 5% yield by reaction of 2,6-dimethylaniline with iodine in ethyl acetate at 45 - 50 ℃ for 1 h. Then, from 4-iodo-2,6- dimethylaniline, via diazotization at - 5 - 0 ℃ and Sandmeyer reaction, 3, 5-dimethyl-4- bromoiodobenzene was obtained in 31.5 % yield. 4-Bromo-2,6-dimethyl aniline was obtained from the same starting material 2,6-dimethylaniline by reacting with hexamethylene tetramine - bromine complex for 0. 5 h at room temperature,and the yield was 62. 0%. Then 2,6-dimethyl-4-bromoiodobenzene was obtained in 33.1% yield from 4-bromo-2, 6-dimethylaniline via diazotization at - 5 - 0 ℃ and iodonation with KI. Structures of the intermediates and the final products were characterized by melting point, IR and ^1HNMR.