Alkali-metal-ion-assisted <i>B</i>
<sub>AL</sub>
2 cleavage of 2-(methoxycarbonyl)-1,3-xylylene-18-crown-5 by benzenemethanethiolate anion
作者:R. Cacciapaglia、L. Mandolini、V. Van Axel Castelli
DOI:10.1002/recl.19931120607
日期:——
BAL2 demethylation of 2-(methoxycarbonyl)-1,3-xylylene-18-crown-5 by benzenemethanethiolate anion in dimethylformamide (+ 1.6M water) at 35°C is significantly promoted by alkali-metal counterions, the efficiency order being Na+ > K+ > Cs+ > Li+. The contrasting behaviour of the model compound, methyl 2,6-dimethylbenzoate, whose demethylation reaction is in fact slightly inhibited by metal ions, points
乙AL 2去甲基化的2-(甲氧基羰基)-1,3-苯二亚甲基-18-冠-5,在35℃下在二甲基甲酰胺(+ 1.6M水)benzenemethanethiolate阴离子由碱金属抗衡离子显著促进,效率次序Na + > K + > Cs + > Li +。模型化合物2,6-二甲基苯甲酸甲酯的反差行为表明脱甲基反应实际上受到金属离子的轻微抑制,这表明冠醚底物的聚醚桥起着至关重要的作用。与该实验室先前的工作相一致,冠状醚底物在金属离子促进的裂解中的选择性过渡态稳定归因于金属离子的静电结合与从亲核体转移过来的负电荷的良好结合与会聚的甲氧基羰基结合并与聚醚桥的中性供体配位结合。