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首页> 外文期刊>Organometallics >Ab initio studies of pericyclic reactions of aminoboranes. [2+2] dimerization and [4+2] Diels-Alder reactions of H2BNH2, Me2BNMe2, and (F3C)(2)BNMe2
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Ab initio studies of pericyclic reactions of aminoboranes. [2+2] dimerization and [4+2] Diels-Alder reactions of H2BNH2, Me2BNMe2, and (F3C)(2)BNMe2

机译：氨基硼烷周环反应的从头算研究。 H2BNH2，Me2BNMe2和（F3C）（2）BNMe2的[2 + 2]二聚化和[4 + 2] Diels-Alder反应

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Examination of the dimerizations and Diels-Alder reactions of the aminoboranes H2BNH2, 1; Me2BNMe2, 2; and (F3C)(2)BNMe2, 3, employing the B3LYP/6-31G* model and,basis set, provides a reasonable picture of the experimental results. Dimerization of 1 requires less activation energy and is more exothermic than its Diels-Alder reaction. Both the Diels-Alder and dimerization reactions of 2 have high barriers and are endothermic. Thus one expects that I will dimerize rather than react with a diene, while 2 should prove unreactive toward dienes or itself. Both expectations match experiment. By contrast, the Diels-Alder reaction of 3 exhibits a lower activation barrier and is more exothermic than dimerization. The activation energy required for the former reaction is sufficiently small that the reaction should occur at room temperature, which it does. In broad terms, these observations are explained by a combination of steric and electronic considerations. Dimerization of 2 and 3 is inhibited by the bulky substituents, but dominates for unsubstituted 1. The Lewis acidity of the bis(trifluoromethyl)borane moiety in 3 enhances its reactivity toward a diene, while the lowered Lewis acidity of the dimethylborane moiety in 2 renders this compound inert. [References: 20]
机译：氨基硼烷H2BNH2，1;的二聚化和Diels-Alder反应的检查Me2BNMe2，2;和（F3C）（2）BNMe2，3，使用B3LYP / 6-31G *模型，并基于基础，提供了合理的实验结果图。 1的二聚化比其Diels-Alder反应需要更少的活化能并且放热更大。 Diels-Alder和2的二聚反应都具有高阻隔性并且是吸热的。因此，人们希望我将二聚而不是与二烯反应，而我应该证明对二烯或它本身没有反应。两种期望都符合实验。相反，3的Diels-Alder反应显示出较低的活化势垒，并且比二聚反应放热更多。前一反应所需的活化能足够小，以至于该反应应在室温下进行。从广义上讲，这些观察结果是通过空间和电子因素的组合来解释的。 2和3的二聚反应受庞大的取代基抑制，但对未取代的1占优势。3中的双（三氟甲基）硼烷部分的路易斯酸度增强了其对二烯的反应性，而2中二甲基硼烷部分的路易斯酸度降低了。这种化合物是惰性的。 [参考：20]

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