Multicomponent cyclocondensation reactions of aminoazoles, arylpyruvic acids and aldehydes with controlled chemoselectivity
摘要:
The multicomponent reactions of 3-amino-1,2,4-triazoles/5-aminotetrazole with phenylpyruvic acids and aromatic aldehydes were studied using conventional thermal heating, ultrasonification and microwave dielectric heating. Two different reaction pathways for these cyclocondensations occurring under either kinetic or thermodynamic control were established depending on the temperature regime and building block selection. In case of aminotriazoles, an unprecedented reaction pathway leading to 5-aryl-7-hydroxy-6-phenyl-4,5,6,7-tetrahydro [1,2,4]triazolol [1,5-a]pyrimidine-7-carboxylic acids was found and discussed. (C) 2008 Elsevier Ltd. All rights reserved.
制备衍生自3-氨基-1,2,4-三唑和不同取代的芳族醛的杂环席夫碱,并进行1 H NMR,13 C NMR和质谱分析。DMSO中的1 H NMR光谱在9.35–8.90 ppm区域内显示出尖锐的单峰,与偶氮甲碱质子相对应。该信号的位置在很大程度上取决于苯并部分的取代基的性质。可以看出,三唑环(5 C)芳香质子信号的形状,位置和积分值明显受到交换速率,弛豫时间,溶液浓度以及所用溶剂的影响。13C NMR被认为是1 H NMR研究结果的重要依据。质谱结果被用作确认所研究化合物结构的工具。基本峰(100%),主要是M-1峰,表明氢自由基的易失性。将未取代的席夫碱的片段化模式作为一般方案。其他方案的差异是由于芳环上连接的取代基的电负性影响所致。