亚氨基环己二烯基：卡宾酯或双自由基？苯并三唑对氰基环戊二烯和1 <i>H-</i>苯并[ <i>b</i> ]叠氮化合物的杂沃尔夫重排,The Journal of Physical Chemistry A

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亚氨基环己二烯基：卡宾酯或双自由基？苯并三唑对氰基环戊二烯和1 H-苯并[ b ]叠氮化合物的杂沃尔夫重排
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2017-08-02 00:00:00 , DOI: 10.1021/acs.jpca.7b05325
Didier Bégué ₁ , Hugo Santos-Silva ₁ , Alain Dargelos ₁ , Curt Wentrup ₂

Affiliation

在DFT和CASPT2的理论水平上研究了苯并三唑1到富维宁4和1 H-苯并嗪7的热重排。苯并三唑1开环至2-重氮-环己二亚胺2，然后进行N ₂消除，得到Z-和E -2-亚氨基环己二烯基3，它们具有三重基态（³ A''）。的开壳层单峰（OSS）（^1名A“）和闭壳层单峰（CSS）（^1个的A'）3谎言〜15和40千卡/摩尔更高的自由能，分别。OSS 3（^1名A“）最好描述为一个1,3-二价基团，而CSS（^1个A'）具有卡宾的字符。OSS的杂沃尔夫重排3倍的产率fulvenimine 4，这是cyanocyclopentadiene的前体5，与千卡/摩尔在CASPT2 38计算的活化能垒（8,8）的水平，从而存在从OSS的表面交叉，以过渡状态附近的CSS。环化成1 H-苯并[ b ]叠氮7的势垒仅为〜13 kcal / mol。因此，涉及单线亚氨基环己二烯基双自由基3的反应路径必定会导致与1 H-benzazirine 7环之前收缩iminofulvene 4和cyanocyclopentadiene 5，在具有基于实验观察一致¹³ Ç标记。1-乙酰基苯并三唑7的热分解导致类似的N-乙酰基-重氮环己二亚胺8，N-乙酰基亚氨基环己二烯基双自由基9和N-乙酰基富马宁10。所述ë - ñ -acetyliminocyclohexadienylidene ë 9环关闭到Ñ乙酰基1 ħ-benzazirine 11之前收缩至N-乙酰基富马宁10，和Z - N-乙酰基-2-重氮环己二胺Z 8环接近2-甲基苯并恶唑12。1 H-苯并zi嗪被预测为可光谱观察到的物种。

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Iminocyclohexadienylidenes: Carbenes or Diradicals? The Hetero-Wolff Rearrangement of Benzotriazoles to Cyanocyclopentadienes and 1H-Benzo[b]azirines

The thermal rearrangements of benzotriazole 1 to fulvenimine 4 and 1H-benzazirine 7 are investigated at DFT and CASPT2 levels of theory. Ring opening of benzotriazole 1 to 2-diazo-cyclohexadienimine 2 followed by N₂ elimination affords Z- and E-2-iminocyclohexadienylidenes 3, which have triplet ground states (³A″). The open-shell singlet (OSS) (¹A″) and closed-shell singlet (CSS) (¹A′) of 3 lie ∼15 and 40 kcal/mol higher in free energy, respectively. The OSS 3 (¹A″) is best described as a 1,3-diradical, whereas the CSS (¹A′) has the character of a carbene. A hetero-Wolff rearrangement of OSS 3 yields fulvenimine 4, which is a precursor of cyanocyclopentadiene 5, with a calculated activation barrier of 38 kcal/mol at the CASPT2(8,8) level, whereby there is a surface crossing from the OSS to the CSS near the transition state. The barrier for cyclization to 1H-benzo[b]azirine 7 is only ∼13 kcal/mol. Therefore, reaction paths involving the singlet iminocyclohexadienylidene diradicals 3 will necessarily cause equilibration with 1H-benzazirine 7 prior to ring contraction to iminofulvene 4 and cyanocyclopentadiene 5, in agreement with experimental observations based on ¹³C labeling. The thermolysis of 1-acetylbenzotriazole 7 leads to the analogous N-acetyl-diazocyclohexadienimines 8, N-acetyliminocyclohexadienylidene diradicals 9, and N-acetylfulvenimine 10. The E-N-acetyliminocyclohexadienylidene E9 ring closes to the N-acetyl-1H-benzazirine 11 prior to ring contraction to N-acetylfulvenimine 10, and the Z-N-acetyl-2-diazocyclohexadienimine Z8 ring closes to 2-methylbenzoxazole 12. 1H-benzazirines are predicted to be spectroscopically observable species.

更新日期：2017-08-03

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