SYNTHESIS AND PROPERTIES OF DIMETHYL 1,2-DIAZETINE-1,2-DICARBOXYLATE, A POTENTIALLY AROMATIC MOLECULE .2.
SYNTHESIS AND PROPERTIES OF DIMETHYL 1,2-DIAZETINE-1,2-DICARBOXYLATE, A POTENTIALLY AROMATIC MOLECULE .2.
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DOI：
10.1071/ch9792659
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发表时间：
1979-01-01
影响因子：
1.1
通讯作者：
PADDONROW, MN
中科院分区：
文献类型：
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作者：
WARRENER, RN;NUNN, EE;PADDONROW, MN
在2，5-二甲基-3，4-二苯基环戊二烯酮(17)与2，5-二甲基-3，4-二苯基环戊-2，4-二烯酮(17)的Diels-Alder反应中，二甲基2，3-diazabicyclo[2，2，0]hex-5-ene-cis-2，3-dicarboxylate(15)的环丁烯n键被用作双烯亲和剂。该反应具有很高的立体选择性，并且几乎完全导致了外熔合加合物(18)的形成。在二烯酮(17)和双环[2，2，0]六-5-烯-顺-2，3-二羧酸酐(5)之间进行类似的环加成反应，得到90：10的加合物(6)。这几个加合物被用作制备相关的双环[4，2，0]八-2，4-二烯衍生物(7)和(20)的前体，它们本身就是用于1，2-光芳构化反应的光底物。这样，碳环前体(7)得到了环-3-烯-顺-1，2-二羧酸酐(8)，而杂环类似物(20)得到了标题二氮杂卓(21)。该杂环的氢化反应生成了相应的1，2-二氮杂环(22)，并对其进行了充分表征。形式上含有六个离域电子的二氮杂环已烷的反应性被特别考虑，因为它与其潜在的芳香性有关。在实践中，二氮杂环对1，4-二氮杂-1，3-二烯(23)的容易开环恰好反映了该环系缺乏芳香性。用INDO-MO-SCF方法对未取代的1，2-二氮杂环的氮转化过程进行了能量计算。结果表明，平面态位于能面上最大值，电子离域很少。平面形式最好的描述是抗芳香性。PMO的论点支持了这一结论。
The cyclobutene n-bond of dimethyl 2,3-diazabicyclo[2,2,0]hex-5-ene-cis-2,3-dicarboxylate (15) has been employed as a dienophile in the Diels-Alder reaction with 2,5-dimethyl-3,4-diphenylcyclopenta- 2,4-dienone (17). The reaction occurred with high stereoselectivity and led, almost exclusively, to the formation of the exo-fused adduct (18). A similar cycloaddition was performed between the dienone (17) and the bicyclo[2,2,0]hex-5-ene-cis-2,3-dicarboxylic anhydride (5) to yield a 90 : 10 mixture of adducts (6). These several adducts were used as precursors for the preparation of the related bicyclo[4,2,0]octa-2,4-diene derivatives (7) and (20), themselves used as photosubstrates for the 1,2-photoaromatization reaction. In this way the carbocyclic precursor (7) yielded cyclobut-3- ene-cis-1,2-dicarboxylic anhydride (8), and the hetero analogue (20) yielded the title diazetine (21). Hydrogenation of this heterocycle yielded the related 1,2-diazetidine (22) which was fully characterized. The reactivity of the diazetine, which formally contains six delocalized electrons, is considered especially as it relates to its potential aromatic character. In practice the facile ring- opening of the diazetine to the 1,4-diazabuta-1,3-diene (23) fairly reflects the lack of aromaticity of this ring system. An INDO MO SCF method has been used to evaluate the energetics of the nitrogen inversion process in the unsubstituted 1,2-diazetine ring. The results indicate that the planar form lies at a maximum on the energy surface and that there is little electron delocalization. The planar form is best described as being antiaromatic. PMO arguments are presented which support this conclusion.