The Carbene/Bridgehead-Olefin Rearrangement: DFT Calculations on 1-Bicyclo[2.1.1]hexylcarbene and 1-Bicyclo[3.1.1]heptylcarbene; Rearrangement of (5-Bromobicyclo[3.1.1]heptyl)bromocarbene
作者:Eva Kohl、Thomas Ströter、Christina Siedschlag、Kurt Polborn、Günter Szeimies
DOI:10.1002/(sici)1099-0690(199911)1999:11<3057::aid-ejoc3057>3.0.co;2-m
日期:1999.11
1-bicyclo[3.1.1]heptylcarbene 12, the preferred stabilization is again enlargement of the four-membered ring to give bicyclo[3.2.1]oct-1(7)-ene 13. The further rearrangement of this alkene to 7-bicyclo[3.2.1]octylidene 16is endothermic by 32.2 kcal/mol and should not take place under moderate conditions. (5-Bromobicyclo[3.1.1]heptyl)bromocarbene 32, a derivative of 12 generated from the tetrabromide 23 with
B3LYP/6-31G(d) 对双环 [2.1.1] 己基卡宾 7a 的计算显示了四元环扩大得到 1-降冰片烯 8 的优选倾向。只有在高温下桥头烯烃 8 重排为 2-降冰片亚基 11 似乎是可能的;提供 2-双环 [3.1.1] 庚亚基 10 的竞争重排具有更高的活化势垒 20.2 kcal/mol。对于 1-双环 [3.1.1] 庚基卡宾 12,优选的稳定化方法是再次扩大四元环以得到双环 [3.2.1] oct-1(7)-烯 13。该烯烃进一步重排为 7 -双环[3.2.1] 亚辛基 16 吸热 32.2 kcal/mol,不应在温和条件下发生。(5-Bromobicyclo[3.1.1]heptyl)bromocarbene 32,一种由四溴化物 23 与 MeLi 生成的 12 的衍生物,