Stereochemistry of the thermal acetylenic Cope rearrangement. Experimental test for a 1,4-cyclohexenediyl as a mechanistic intermediate
作者:Karen Ann Owens、Jerome A. Berson
DOI:10.1021/ja00172a010
日期:1990.8
The reversible [3,3]-sigmatropic rearrangement that interconverts optically active 4-methyl-5-hepten-1-yne and 4-methyl-1,2,5-heptatriene (an acetylenic Cope rearrangement) occurs with a stereochemistry corresponding to an orbital symmetry allowed suprafacial pathway with essentially complete preservation of enantiomeric purity. Computational simulation of the time-composition profile shows that 1%
可逆 [3,3]-sigmatropic 重排将光学活性 4-methyl-5-hepten-1-yne 和 4-methyl-1,2,5-heptatriene(一种炔类 Cope 重排)相互转化,其立体化学对应于轨道对称允许表面通路,基本上完全保留对映体纯度。时间组成曲线的计算模拟表明,1% 或更少的重排通过立体化学等效的禁止的 antarafacial 途径。结合最近对模型 4-环己烯基环构象反转速率常数的实验测定,结果表明双基 3,5-二甲基-1-环己烯-1,4-二基发生在能量表面重排的分解率必须在 1.6-3.8×10 13 s − 1 范围内。