Native and modified chitosan-based hydrogels as green heterogeneous organocatalysts for imine-mediated Knoevenagel condensation
作者:A. Franconetti、P. Domínguez-Rodríguez、D. Lara-García、R. Prado-Gotor、F. Cabrera-Escribano
DOI:10.1016/j.apcata.2016.03.012
日期:2016.5
Knoevenagel condensation catalysed with native and modified chitosan-based heterogeneous catalysts. The efficiency of our hydrogel organocatalysts, chitosan hydrogel beads and ureidyl-chitosan derivative hydrogel disks, was evaluated as function of pH, temperature and catalyst concentration by considering reaction rates, conversions, E/Z stereoselectivities, and kinetic studies of a model reaction between
以天然和改性壳聚糖为基的多相催化剂,通过Knoevenagel缩合反应,合成了衍生自芳族和杂芳族醛的多种亚甲基丙二腈和氰基丙烯酸乙酯。考虑到反应速率,转化率,E / Z立体选择性以及模型间4 -硝基苯甲醛和氰基乙酸乙酯。固态的空前研究13当转化率达到50%后淬灭反应时,所用催化剂的C CP MAS NMR表明,在此过程中形成了亚胺-壳聚糖中间体。使用新颖的CLIP-HSQMCB实验,通过NMR测量碳-质子偶合常数(3 J C,H),进行E / Z氰基丙烯酸乙酯异构体混合物的分析,以确定相应的立体选择性。此外,DFT计算使我们合理化了所观察到的E / Z立体选择性,并评估了脲基部分对与醛相互作用和与壳聚糖衍生物形成亚胺中间体的作用。