Bergman Cyclization of Sterically Hindered Substrates and Observation of Phenyl-Shifted Products
作者:Kevin D. Lewis、Adam J. Matzger
DOI:10.1021/ja042703c
日期:2005.7.1
1-ethynyl-2-(phenylethynyl)benzene and (Z)-1,6-diphenylhex-3-ene-2,5-diyne also yielded products resulting from phenyl shifts. These results are explained through computations that point to the role of steric repulsion and benzyne stability in driving these isomerizations. The computed barriers for phenyl shifting are dramatically higher than those observed in the case of sp3 radicals. However, these transformations
在 1,4-环己二烯存在下,在 260 至 360 摄氏度的温度范围内加热 1,2-双(苯乙炔基)苯,产生预期的伯格曼产物 2,3-二苯基萘,仅作为次要产物 (<3%)在研究的所有反应条件下。由一个或多个苯基转移产生的主要产物是 1,3- 和 1,4- 二苯基萘,它们的产率分别高达 16% 和 11%。虽然效率稍低,但 1-乙炔基-2-(苯基乙炔基)苯和 (Z)-1,6-二苯基己-3-烯-2,5-二炔也产生由苯基位移产生的产物。这些结果是通过计算来解释的,这些计算指出了空间排斥和苄稳定性在驱动这些异构化中的作用。苯基转移的计算势垒显着高于在 sp3 自由基的情况下观察到的势垒。然而,