Reactions of Carbon Electrophiles with Cobalt-Coordinated Enynes: Scope and Limitations
作者:Herbert Mayr、Oliver Kuhn、Clemens Schlierf、Armin R Ofial
DOI:10.1016/s0040-4020(00)00347-1
日期:2000.6
increases the nucleophilic reactivity of enynes by a factor of > 106. The exchange of one CO ligand by PPh3 (2a→2d), however, has only little effect on the reactivity of the enyne moiety. The second-order rate constants match the linear free energy relationship lg k20°C=s(E+N) and allow to determine the nucleophilicity parameters N and s for 2a–d. It is shown that at −70°C, electrophiles with E>0 are able to
用光度法研究了二甲酚配位的炔烃2a – d与二苯甲基阳离子3a – c,f的反应动力学。反应遵循二级动力学,表明Co 2(CO)6配位将烯炔的亲核反应性提高了> 10 6倍。然而,PPh 3(2a → 2d)交换一种CO配体对烯炔部分的反应性影响很小。二阶速率常数与线性自由能关系lg k 20°C = s(È + Ñ),并允许确定亲核性参数Ñ和š为图2a - d。结果表明,在-70°C下,E > 0的亲电试剂能够与烯炔配合物2a,2c和2d反应,而E > -2的亲电试剂适合与2b反应。