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首页> 外文期刊>Chemistry: A European journal >Experimental and Theoretical Characterization of the Valence Isomerization of Bi-2H-azirin-2-yls to Diazabenzenes
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Experimental and Theoretical Characterization of the Valence Isomerization of Bi-2H-azirin-2-yls to Diazabenzenes

机译：Bi-2H-azirin-2-yls到二氮杂苯的化合价的实验和理论表征

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摘要

3,4-Diazidocyclobutenes 16 were prepared from the corresponding dihalides.Some of these diazides,such as parent compound 16d and phenyl-substituted derivatives 16c,f,under-went spontaneous stereoselective elec-trocyclic ring opening below room tem-perature,whereas the tetraalkyl deriva-tives of 16 had to be heated to force the same reaction.In most cases,the resulting l,4-diazidobuta-l,3-dienes 8 were isolated to study their photo-chemical transformation into bi-2H-azirin-2-yls 9 via intermediate mono-azirines 17.Except for starting materi-als with a low number of substituents such as 9d and 9f,title compounds 9 underwent a thermal valence isomeri-zation which led exclusively to pyrida-zines 18 at surprisingly low tempera-tures.Based on quantum-chemical cal-culations for the parent bi-2H-azirinyl-2-yl 9d at the UB3LYP/6-31+G(d) and MR-MP2/TZV(2df,2p) levels,the valence isomerization process is best explained by simultaneous homolytic cleavage of both C-N single bonds of 9 to generate energetically favorable N,N' diradicals 26,which cyclize to 18.The theoretical studies indicate also that one stereoisomer of 9,namely,the rac compound,should undergo valence isomerization more easily than the other,which is in conformity with dif-ferent rates of these rearrangement re-actions found experimentally.For the tetramethyl-bi-2H-azirin-2-yls 9g,which are better models for the experi-mentally studied compounds,simulta-neous homolytic cleavage of both C-N single bonds is also predicted by the calculations,although the intermediate diradicals 26g are significantly higher in energy than those of the parent system 9d.
机译：由相应的二卤化物制备3,4-二叠氮环丁烯16.其中一些叠氮化物，例如母体化合物16d和苯基取代的衍生物16c，f，在室温以下自发地发生立体选择性电环开环，而必须加热16个四烷基衍生物以强制进行相同的反应。在大多数情况下，分离所得的1,4-二氮杂丁-1-3-1,8二烯8研究其光化学转化为bi-2H-azirin-的过程。通过中间单叠氮基17生成2-yls9。除了具有少量取代基的起始材料（例如9d和9f）外，标题化合物9经历了热价异构化，仅导致吡啶酮-zines 18的出奇的低价基于UB3LYP / 6-31 + G（d）和MR-MP2 / TZV（2df，2p）水平的母体bi-2H-azirinyl-2-yl 9d的量子化学计算，价异构化过程最好通过9的两个CN单键同时均裂以生成e有益于N，N'的自由基，循环至18.理论研究还表明，9的一种立体异构体，即rac化合物应比另一种更容易进行价异构化，这与不同的速率相符实验中发现的这些重排反应。对于实验研究的化合物的更好模型四甲基-Bi-2H-叠氮基-2-基9g，还预测了两个CN单键的同时均质裂解。通过计算，尽管中间双自由基26g的能量明显高于母系统9d的能量。

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