BENZENE OXIDE-OXEPIN VALENCE TAUTOMERISM
BENZENE OXIDE-OXEPIN VALENCE TAUTOMERISM
复制标题
DOI：
10.1002/anie.196703851
复制
发表时间：
1967-01-01
影响因子：
16.6
通讯作者：
GUNTHER, H
中科院分区：
文献类型：
--
作者：
VOGEL, E;GUNTHER, H
苯氧化物和潜在的8π电子系统氧杂卓存在于彼此的价互变异构平衡中，两种组分的贡献程度大致相同。NMR光谱测量表明，平衡很快建立（正向和反向反应的活化能分别为9.1和7.2 kcal mole−1）。目前对氧杂卓性质的了解证明其分类为“异托品烯”是合理的。氧化苯-氧杂环庚三烯是一种具有波动键的体系，其平衡可以通过合适的取代基从一个极端转移到另一个极端。氧化物组分决定了体系与大多数试剂的反应，对于1，6-oxido[10]annulene，其形式上是2，7-桥氧杂环庚烯，氧杂环庚烯的特征被完全抑制，形成了一个扩展到C10周长的离域10π电子系统。1，6-oxido[10]-annulene的存在和芳香性导致了氧桥环烯（1，6; 8，13-bisoxido[14]annulene，1，6; 8，17; 10，15-trisoxido[18]annulene等）同源系列的概念，与母体并苯一样，它们具有（4 n + 2）π电子系统。分子模型表明，在氧桥的顺式或全顺式排列的情况下，可以实现C4 n +2周长的相当大的平坦化，并且因此满足芳香性的要求。这一点在顺式-1，6; 8，13-双氧化[14]轮烯的合成和性质中得到了惊人的证实。
Benzene oxide and the potential 8π‐electron system oxepin exist in valence‐tautomeric equilibrium with each other, to which both components contribute to approximately the same extent. NMR spectroscopic measurements show that the equilibrium is rapidly established (activation energies of the forward and reverse reactions 9.1 and 7.2 kcal mole−1, respectively). The present knowledge of the properties of oxepin justifies its classification as a “heterotropilidene”. Benzene oxide‐oxepin represents a system having fluctuating bonds, the equilibrium of which can be displaced from one extreme to the other by means of suitable substituents. The oxide component determines the reactions of the system with most agents.With 1,6‐oxido[10]annulene, which is formally a 2,7‐bridged oxepin, the oxepin character is completely suppressed by the formation of a delocalized 10π‐electron system extending over the C10perimeter. The existence and aromatic character of 1,6‐oxido[10]‐annulene give rise to the conception of a homologous series of oxygen bridged annulenes (1,6; 8,13‐bisoxido[14]annulene, 1,6; 8,17; 10,15‐trisoxido[18]annulene etc.), which, like the parent acenes, possess a (4n + 2)π‐electron system. Molecular models demonstrate that a considerable flattening of the C4n+2perimeter is achievable in the case of a syn or all‐syn arrangement of the oxygen bridges, and that the requirement for aromaticity is thus satisfied. This is confirmed in a striking manner by the synthesis and properties of syn‐1,6; 8,13‐bisoxido[14]annulene.