Rearrangement of 3-Membered 1,1,2-Trifluorobromonium and Iodonium Ions and Comparison of Trifluorochloronium to Fluorocarbenium Ions.
作者
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.;
[摘要]：Reactions of chlorine (Cl2) with 4-halo-1,1,2-trifluorobut-1-enes [1 (Cl), 2 (Br), or 3 (I)] give open-ion intermediates A and E that are in equil. The open-chloronium ions rearrange to a five-membered-ring halonium ion during ionic chlorination of 3 when the no.-4 halo-substituent is iodine. Three-membered-ring bromonium and iodonium ions from alkenes 1, 2, or 3 are rather sym. and similar in structure. Quantum chem. calcns. 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. The five-membered-ring intermediates lead to rearranged products. Rearranged products increase as the no.-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.
