A Nonaromatic Thiophene-Fused Heptalene and Its Aromatic Dianion
A Nonaromatic Thiophene-Fused Heptalene and Its Aromatic Dianion
复制标题
非芳香族噻吩稠合庚烯及其芳香族二价阴离子
DOI：
10.1002/anie.201501790
复制
发表时间：
2015
期刊：
影响因子：
--
通讯作者：
S. Yamaguchi
中科院分区：
文献类型：
--
作者：
H. Oshima;A. Fukazawa;T. Sasamori;S. Yamaguchi
Heptalene, a nonaromatic, bicyclic 12 π‐electron system with a twisted structure, is of great interest with regard to its potential Hückel aromaticity in the two‐electron oxidized or reduced forms. The synthesis of thiophene‐fused heptalene5from the reductive transannular cyclization of bisdehydro[12]annulene4, and its solid‐state structure, which was confirmed by X‐ray crystallographic analysis, is presented. Chemical reduction of5readily generated the corresponding dianion, which was successfully isolated as [(K[2.2.2]cryptand)+]252−. The X‐ray crystallographic analysis of the dianion revealed a shallower saddle structure for the heptalene moiety and a lesser degree of bond alternation relative to5.1H NMR spectroscopy exposed the effect of a diamagnetic ring current on dianion52−, which was corroborated by nucleus‐independent chemical shift (NICS) calculations. These results demonstrate that the heptalene dianion, containing 14 π‐electrons, does indeed exhibit pronounced degrees of Hückel aromaticity.
