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Research Express@NCKU Volume 28 Issue 1 - December 5, 2014 [ http://research.ncku.edu.tw/re/articles/e/20141205/3.html ]
Synthesis, Structural Analysis, and Properties of [8]Circulenes
Chieh-Ning Feng
1, Ming-Yu Kuo
2, Yao-Ting Wu
1,*1 Department of Chemistry, National Cheng Kung University, 70101 Tainan, Taiwan
2 Department of Applied Chemistry, National Chi Nan University, 54561 Puli, Nantou, Taiwan [email protected]
Angewandte Chemie International Edition, Vol. 52, No. 30, 7791–7794 (2013)
[
n
]Circulene is a macrocyclic arene in which central n-sided polygon is completely surrounded and fused by benzenoids. 1Despite the interesting geometry and unusual aromaticity of [8]circulene, this study is the first to elucidate the synthesis, structural analysis and properties of [8]circulene derivatives. The palladium-catalyzed annulations of tetraiodo-substituted tetraphenylenes with diarylethynes gave persubstituted [8]circulenes in moderate yields. X-ray crystallography indicated that [8]circulene is a saddle-shaped molecule. Like 1,3,5,7-cyclooctatetraene, the central eight-membered ring is tub-shaped, butall bond lengths (approximately 1.45 Å) and bond angles (around 125˚) are almost identical. According to the structural and theoretical analyses, the eight-membered ring is non-aromatic and all six-membered rings have moderate to weak aromatic characteristics. Further investigations of their physical properties and chemical reactivity are underway.
References:
1. The compound class circulene is defined by Wynberg, see: a) J. H. Dopper, H. Wynberg, Tetrahedron Lett.
1972, 13, 763. Reviews for circulenes, see: b) J. S. Siegel, T. J. Seiders, Chem. in Britain 1995, 31, 313; c) C.-S. Chang, Y.-T. Wu in Science of Synthesis, Vol. 45b (Eds.: J. Siegel, Y. Tobe), Georg Thieme, Stuttgart, 2009, 45b, pp. 955.
