Isotope Effects and the Mechanism of Triazolinedione Ene Reactions. Aziridinium Imides Are Innocent Bystanders
作者:Daniel A. Singleton、Chao Hang
DOI:10.1021/ja9933339
日期:1999.12.1
Kinetic isotope effects were determined for the ene reactions of 4-phenyl-1,2,4-triazoline-2,5-dione with 2-methyl-2-butene and 2-methyl-1-pentene. In each case highly inverse (kH/kD = 0.87−0.88) vinylic deuterium isotope effects were observed. Large 13C isotope effects were observed for the less-substituted olefinic carbons of each alkene and much smaller effects were found in the more-substituted
4-苯基-1,2,4-三唑啉-2,5-二酮与2-甲基-2-丁烯和2-甲基-1-戊烯的烯反应测定了动力学同位素效应。在每种情况下,都观察到高度反向 (kH/kD = 0.87−0.88) 乙烯基氘同位素效应。对于每个烯烃的较少取代的烯烃碳,观察到大的 13C 同位素效应,并且在较多取代的烯烃碳中发现小得多的效应。Becke3LYP 对 1,2,4-三唑啉-2,5-二酮与异丁烯、2-甲基-2-丁烯和四甲基乙烯的烯反应机理途径的计算预测了这些反应的新机制,涉及开放双自由基作为关键中间体。这种双自由基可以形成烯产物或可逆地形成中间体氮丙啶酰亚胺。这些计算的有效性得到了实验和理论预测同位素效应的比较的支持。发现了在甲基存在下 2-甲基-1-戊烯的烯反应的产物比率的弯曲 Arrhenius 图。