Kinetics and mechanisms of nucleophilic displacements with heterocycles as leaving groups. Part 13. Penta- and nona-cyclic derivatives
作者:Alan R. Katritzky、Charles M. Marson
DOI:10.1039/p29830001455
日期:——
Steric acceleration by α,β-polycyclic fusion in pyridine leaving groups is quantitatively assessed. Constraining phenyl rings in pyridines to near planarity by ethano bridges in phenanthro[2,3-h]quinolinium (39) is less effective in terms of SN2 displacement reactions by a factor of ca. 20 than in the less sterically hindered benzoquinolinium (2b). However, the corresponding rate for diphenanthro[2
定量评估吡啶离去基团中α,β-多环融合引起的立体加速。在菲并约束苯环在吡啶附近平面由乙醇桥[2,3- ħ ]喹啉(39)是较少在以下方面有效的小号Ñ通过的一个因子2置换反应约 比在空间上受阻较少的苯并喹啉(2b)中的20。然而,联苯并[2,3- c ; 3',2'- h ] -ac啶(43)的相应速率几乎与二苯并ac啶鎓(3b)系统的速率相同。与(2a)和(3a)相比,系统(12)和(19)中的侧基苯基降低了S N 2速率。2和ca。4,分别。这些结构修饰均未显着提高S N 1速率。