Shellhamer Dale F, Davenport Kevyn J, Forberg Heidi K, Herrick Matthew P, Jones Rachel N, Rodriguez Sean J, Sanabria Sunamita, Trager Nicole N, Weiss Ryan J, Heasley Victor L, Boatz Jerry A
Department of Chemistry, Point Loma Nazarene University, San Diego, CA 92106-2899, USA.
J Org Chem. 2008 Jun 20;73(12):4532-8. doi: 10.1021/jo800472e. Epub 2008 May 28.
Reactions of chlorine (Cl(2)) with 4-halo-1,1,2-trifluorobut-1-enes (1, 2, or 3) give open-ion intermediates A and E that are in equilibrium. The open-chloronium ions (E) rearrange to a five-membered-ring halonium ion during ionic chlorination of 3 when the number-4 halo-substituent is iodine. Three-membered-ring bromonium and iodonium ions from alkenes 1, 2, or 3 are rather symmetrical and similar in structure. Quantum chemical calculations show that five-membered-ring halonium ion intermediates are 11 to 27 kcal/mol more stable than the three-membered-ring halonium ions or the open-ions A and E. The five-membered-ring intermediates lead to rearranged products. Rearranged products increase as the number-4 halogen (Z) becomes more nucleophilic (Z: Cl < Br < I). Open chloronium ions from ionic chlorination of terminal fluorovinyl alkenes are compared to the open ions generated by protons to similar alkenes.
氯（Cl₂）与4-卤代-1,1,2-三氟丁-1-烯（1、2或3）反应生成处于平衡状态的开环离子中间体A和E。当4-卤代取代基为碘时，在3的离子氯化过程中，开环氯鎓离子（E）重排为五元环卤鎓离子。来自烯烃1、2或3的三元环溴鎓离子和碘鎓离子相当对称且结构相似。量子化学计算表明，五元环卤鎓离子中间体比三元环卤鎓离子或开环离子A和E稳定11至27千卡/摩尔。五元环中间体导致重排产物。随着4-卤素（Z）的亲核性增强（Z：Cl＜Br＜I），重排产物增加。将末端氟乙烯基烯烃离子氯化产生的开环氯鎓离子与质子作用于类似烯烃产生的开环离子进行了比较。
