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首页> 外文期刊>Organometallics >Computational studies of the origin of regiospecificity in the [4+2] Diels-Alder reaction between R2B=NR2 ' compounds and substituted cis-butadienes
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Computational studies of the origin of regiospecificity in the [4+2] Diels-Alder reaction between R2B=NR2 ' compounds and substituted cis-butadienes

机译：R2B = NR2'化合物与取代的顺丁二烯之间的[4 + 2] Diels-Alder反应中区域特异性起源的计算研究

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摘要

Computational studies comparing the energetics of [4+2] Diels-Alder-like cyclizations of aminoboranes R2B=NR2'(R = H, CF3; R'= H, CH3) with substituted cis-2-R"-1,3-butadienes (R" = CH3, NH2, CF3) show that the regiospecificity observed experimentally derives from the transition state barrier heights rather than the reaction exothermicities. When R" is an electron-donating group such as CH3 or NH2, the model predicts a preference for the 5-R"-1-bora-2-azacyclohex-4-ene product; that is, the R" group favors proximity to the boron atom. When R" is an electron-withdrawing group such as CF3, the model predicts a preference for the 4-R"-1-bora-2-azacyclohex-4-ene product; that is, the R" group favors proximity to the nitrogen atom. The predictions are in accord with experimental results and organic frontier molecular orbital theory, although the aminoboranes exhibit a surprising degree of discrimination between similarly charged carbon atoms. [References: 16]
机译：计算研究比较了[4 + 2]氨基硼烷R2B = NR2'（R = H，CF3; R'= H，CH3）与取代的cis-2-R“ -1,3-的Diels-Alder样环化的能量丁二烯（R” = CH3，NH2，CF3）表明，实验观察到的区域特异性是由过渡态势垒高度而不是反应放热引起的。当R”为电子给体基团（例如CH3或NH2）时，该模型预测优先选择5-R” -1-bora-2-azacyclohex-4-ene产物;也就是说，R“基团倾向于靠近硼原子。当R”是吸电子基团，例如CF3时，该模型预测会优先考虑使用4-R“ -1-bora-2-azacyclohex-4-ene产物;即，R”基团有利于接近氮原子。尽管氨基硼烷在带相似电荷的碳原子之间表现出令人惊讶的区分度，但这些预测与实验结果和有机前沿分子轨道理论相符。 [参考：16]

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