NH2-Ga-MIL-53催化剂对Strecker反应的底物选择性（英文）

研究了金属有机骨架化合物NH2-Ga-MIL-53对多种N-苯基亚胺底物的Strecker反应的催化性能,研究结果表明:(1)NH2-Ga-MIL-53具有高度催化活性和良好的底物普适性;(2)亚胺底物上取代基的电子效应是影响催化反应速率的关键因素,在亚胺底物上引入给电子取代基团(如甲氧基和苯基)可以加快反应速率,引入吸电子取代基团(如三氟甲基和硝基)可降低反应速率;(3)亚胺底物上取代基的位置对于催化反应速率同样具有重要影响,在亚胺底物的邻位引入甲氧基取代基团时,反应速率加快得最明显;(4)作为非均相催化剂,NH2-Ga-MIL-53可循环使用9次而不失活且保持骨架结构不变;(5)NH2-Ga-MIL-53和Ga-MIL-53催化性能的对比结果表明,NH2-Ga-MIL-53结构中的氨基可以作为路易斯碱活性中心协同路易斯酸催化中心(Ga3+)有效促进strecker反应的进行。此外,由NH2-Ga-MIL-53、六水合硝酸镓和2-氨基对苯二甲酸对Strecker反应的催化效果的对比可知,NH2-Ga-MIL-53的孔结构是提高反应产物专一性的重要因素。     

Binding Studies on Substrate- and Enantio-Selective Molecularly Imprinted Polymers

Abstract

A molecularly imprinted polymer was prepared using tert-butyloxycarbonyl-L-phenylalanine as the print molecule and methacrylic acid as the functional monomer. The bulk polymer obtained was ground, sieved, packed into a column and investigated in the HPLC-mode by frontal chromatography to determine the number of binding sites and dissociation constants for the enantiomers interacting with the polymer. The dissociation constant for the L-enantiomer of the print molecule was lower than for the D-enantiomer (6.3 mM and 8.1 mM, respectively). This means that the affinity for the L-enantiomer was higher than for the D-enantiomer. The number of binding sites in the polymer giving rise to these dissociation constants were determined to be 28 μmol per g dry polymer.