基于肉桂醛的咪唑并[2,1-b]-1,3,4-二唑Mannich碱的合成及表征

The Synthesis and Characterization of Imidazo[2,1-b]-1,3,4-Oxadiazole Mannich Bases Based on Cinnamyl Aldehyde

以肉桂醛与氨基脲经缩合、环合得到2-氨基-5-苯乙烯基-1,3,4-二唑,再与ɑ-溴苯乙酮反应得到2-苯乙烯基-6-芳基咪唑并[2,1-b]-1,3,4-二唑,最后经Mannich反应得到Mannich碱.所有中间体及产物的结构经IR、1H NMR、ESI-MS及元素分析确证,同时优化了中间体及产物的反应条件.2-苯乙烯基-6-芳基咪唑并[2,1-b]-1,3,4-二唑的最佳反应条件为n(2-氨基-5-苯乙烯基-1,3,4-二唑)∶n(α-溴代苯乙酮)=1.0∶1.2.在浓盐酸催化下于无水乙醇中回流反应18 h,产率为57.8%.Mannich碱的最佳反应条件为n(2-苯乙烯基-6-芳基咪唑并[2,1-b]-1,3,4-二唑)∶n(40%甲醛)∶n(无水哌嗪)=1.0∶1.3∶1.3,在无水乙醇中回流反应8 h,产率为55.4%.

2-amino-5-styryl-1,3,4-oxadiazole and 2-styryl-6-arylimidazo[2,1-b]-1,3,4-oxadiazole are synthesized by condensation,cyclization of cinnamyl aldehyde with semicarbazide and then withɑ-bromine-acetophenone.Finally,Mannich bases are synthesized by Mannich reaction.All the intermediates and target products are characterized by IR,1H NMR,ESI-MS and elemental analysis.The reaction condition of intermediates and product are optimized.The optimal condition for synthesis of 2-styryl-6-arylimidazo[2,1-b]-1,3,4-oxadiazole is n(2-amino-5-styryl-1,3,4-oxadiazole)∶n(ɑ-bromine-acetophenone)=1.0∶1.2,refluxed for 18 h in absolute C2H5OH,the yield is above 57.8%.The optimal condition for synthesis of Mannich base is n(2-styryl-6-arylimidazo[2,1-b]-1,3,4-oxadiazole)∶n(40%formaldahyde)∶n(absolute piperazine)=1.0∶1.3∶1.3,catalyzed by concentrated.HCl and refluxed for 8 h,the yield is above 55.4%.