Mechanistic Investigation of the Dipolar [2+2] CycloadditionâCycloreversion Reaction between 4-(<i>N</i>,<i>N</i>-Dimethylamino)phenylacetylene and Arylated 1,1-Dicyanovinyl Derivatives To Form Intramolecular Charge-Transfer Chromophores
作者:Yi-Lin Wu、Peterâ
D. Jarowski、W.â
Bernd Schweizer、François Diederich
DOI:10.1002/chem.200902645
日期:2010.1.4
The kinetics and mechanism of the formal [2+2] cycloaddition–cycloreversion reaction between 4‐(N,N‐dimethylamino)phenylacetylene (1) and para‐substituted benzylidenemalononitriles 2 b–2 l to form 2‐donor‐substituted 1,1‐dicyanobuta‐1,3‐dienes 3 b–3 l via the postulated dicyanocyclobutene intermediates 4 b–4 l have been studied experimentally by the method of initial rates and computationally at the
4-(N,N-二甲基氨基)苯乙炔(1)与对位取代的亚苄基丙二腈2 b - 2 l形成2供体取代的1,1之间的正式[2 + 2]环加成-环还原反应的动力学和机理。通过假定的双氰基环丁烯中间体4 b - 4 l通过假定的双氰基环丁烯中间体4 b - 4 l对-dicyanobuta-1,3-二烯3 b - 3 l进行了无限制B3LYP / 6-31G(d)水平的实验研究。发现该转变遵循双分子二级动力学,= 13–18 kcal mol -1,≈−30 cal K -1 mol -1和= 22–27 kcal mol -1。这些决定速率的环加成步骤的实验激活参数接近于计算值。速率常数显示出良好的线性自由能关系(ρ与电子字符= 2.0)对-二甲基甲酰胺(DMF)中亚苄基部分上的取代基,表明存在偶极机制。对乙腈中计算结构及其对应的溶剂化能量的分析表明,决定亲核性末端炔碳对双氰基乙烯基亲电子体的速率