Aryl substituent effects on the thermal interconversion of cyclobutenediones and 1,2-bisketenes
作者:Ronghua Liu、Thomas T. Tidwell
DOI:10.1039/p29960002757
日期:——
The rates and activation parameters are reported for ringclosure of 1,2 bisketenes OCC(C6H4X)C(SiMe3)CO (7), generated by photolysis of the corresponding cyclobutenediones 6. The rates at 70 °C are correlated with the σp+ constants of the aryl substituents by the relationship log k=–1.10 σp+–3.60 (r= 1.000). The greater reactivity in ringclosure to 6 for electron-donating aryl substituents is consistent
报告了速率和活化参数,用于通过相应环丁烯二酮6的光解反应生成的1,2双烯酮O C C(C 6 H 4 X)C(SiMe 3)C O(7)的闭环。C被与σ相关p +由关系日志常数芳基取代基的ķ = -1.10σ p + -3.60(ř= 1.000)。对于给电子的芳基取代基,闭环反应具有更大的反应性,达到6,这与通过电子供体基团稳定缺电子的环丁烯二酮环,通过π-受体基团进行乙烯酮稳定和通过电子-π-供体基团进行乙烯酮去稳定相一致。以前是根据理论计算得出的。还测量了7d(X = CH 3 CO)的平衡浓度,其平衡浓度从69.2°C时的1.6%变化到143.1°C时的9.7%,超出了7a的5.4–7.5倍(X = H)。CH 3 CO对双烯酮的支持与对反应速率的影响密切相关。
Liu, Ronghua; Tidwell, Thomas T., Canadian Journal of Chemistry, 1995, vol. 73, p. 1818 - 1822