Mechanism of a Diels-Alder reaction. Butadiene and its dimers
作者:W. von E. Doering、M. Franck-Neumann、D. Hasselmann、R. L. Kaye
DOI:10.1021/ja00766a029
日期:1972.5
the trans,trans (or, less probably, the cis,cis) diradical to butadiene to be 81.1 5 2.0 kcal/mol, in good agreement with that (82.3 kcal/mol) deduced for the same reaction in the transformations of trans-divinylcyclobutane investigated by Hammond and DeBoer. In relation to the transition state for the Diels-Alder reaction of butadiene with itself to give Cvinylcyclohexene, the cleavage of the diradical
(I?)-(+)-1 ,l-dideuterio-2-(cyclohex-3-enyl)ethene(标记为 4vinylcyclohexene)的合成和动力学研究揭示了外消旋化和氘交换的新反应,前者固定了顺式,反式(和/或顺式,顺式)八-3,6-二烯-1,7-二基双自由基的形成热比以往更牢固。重新确定环辛基-1,5-二烯热反应的动力学参数确定反式、反式(或不太可能的顺式、顺式)双自由基裂解为丁二烯的形成热为 81.1 5 2.0 kcal /mol,与由 Hammond 和 DeBoer 研究的反式二乙烯基环丁烷转化中相同反应推导出的 (82.3 kcal/mol) 非常一致。关于丁二烯与其自身进行 Diels-Alder 反应生成 C乙烯基环己烯的过渡态,在目前的实验结果限制范围内,双自由基的裂解似乎能量稍高。这种 Diels-Alder 反应的机制暂时被认为是协调一致的,可能是两阶段,但不是两步。关于