Nonstatistical dynamics in the thermal C2-C6/diels-alder cyclization of enyne-allenes: effect of topology.
Nonstatistical dynamics in the thermal C2-C6/diels-alder cyclization of enyne-allenes: effect of topology.
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DOI：
10.1021/jo502693b
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发表时间：
2015-02
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影响因子：
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通讯作者：
Debabrata Samanta;Anup Rana;M. Schmittel
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文献类型：
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作者：
Debabrata Samanta;Anup Rana;M. Schmittel
在丙二烯末端具有两个芳基环的烯炔-丙二烯的热C(2)-C(6)（施密特尔）环化在实验上产生了三种形式的狄尔斯-阿尔德（DA）环加成产物，其中两种（涉及二甲氨基苯基单元）被证明是在非统计过程中形成的。对反应路径的 DFT 计算表明，两个芳环（Ph 与 PhNMe2）不会以动态方式相互作用，因为它们的最小能量路径 (MEP) 被大势垒隔开。尽管 8 的能量 TS 更高，但受阻较多的 DA 产物 8（二甲氨基的邻位）优先于受阻较少的产物 9（二甲氨基的对位）优先形成，这表明在二甲氨基苯基单元上的环化过程中出现了非统计动力学。势能面 (PES) 计算表明，大量的非统计动力学 (97%) 来自简单的 IRC 动力学（左图），与相关系统的非 IRC 动力学相比（∼76%，右图，J. Org. Chem. 2014, 79, 2368）。
The thermal C(2)-C(6) (Schmittel) cyclization of an enyne-allene with two aryl rings at the allene terminus experimentally leads to three formal Diels-Alder (DA) cycloaddition products, two of which (involving the dimethylamino phenyl unit) are shown to form in a nonstatistical process. DFT computations on the reaction paths reveal that the two aryl rings (Ph vs PhNMe2) do not interact in a dynamic manner as their minimum energy pathways (MEPs) are separated by a large barrier. The preferential formation of the more-hindered DA product 8 (ortho to the dimethylamino group) over the less-hindered product 9 (para to the dimethylamino group), despite the higher energy TS for 8, suggests the occurrence of nonstatistical dynamics in the cyclization onto the dimethylamino phenyl unit, though. Potential energy surface (PES) computations indicate that the large amount of nonstatistical dynamics (97%) arises from facile IRC dynamics (left picture) that is compared with the non-IRC dynamics of a related system (∼76%, right picture, J. Org. Chem. 2014, 79, 2368).