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A cyclophane is a hydrocarbon consisting of an aromatic unit (typically a benzene ring) and an aliphatic chain that forms a bridge between two non-adjacent positions of the aromatic ring. More complex derivatives with multiple aromatic units and bridges forming cagelike structures are also known. Cyclophanes are well-studied in organic chemistry because they adopt unusual chemical conformations due to build-up of strain. Despite this, cyclophane structures are not unknown to biomolecules. Basic cyclophane types are ()metacyclophanes (I) in ''scheme 1'', ()paracyclophanes (II) and ()cyclophanes (III). the prefixes ''meta'' and ''para'' correspond to the usual arene substitution patterns and n refers to the number of atoms making up the bridge. ==Structure== Paracyclophanes adopt the boat conformation normally observed in cyclohexanes but are still able to retain aromaticity. The smaller the value of n the larger the deviation from aromatic planarity. In ()paracyclophane which is one of the smallest, yet stable, cyclophanes X-ray crystallography shows that the aromatic bridgehead carbon atom makes an angle of 20.5° with the plane. The benzyl carbons deviate by another 20.2°. The carbon to carbon bond length alternation has increased from 0 for benzene to 39 pm.〔''Synthesis and molecular structure of (Z)-()Paracycloph-3-enes'' Yoshito Tobe, Kenichi Ueda, Teruhisa Kaneda, Kiyomi Kakiuchi, Yoshinobu Odaira, Yasushi Kai, Nobutami Kasai J. Am. Chem. Soc.; 1987; 109(4); 1136-1144. (Abstract )〕〔J. Hunger, C. Wolff, W. Tochtermann, E-M. Peters, K.Peters, H.G. von Schering Chem. Ber., 119, 2698 (1986)〕 In organic reactions ()cyclophane tends to react as a diene derivative and not as an arene. With bromine it gives 1,4-addition and with chlorine the 1,2-addition product forms. Yet the proton NMR spectrum displays the aromatic protons and their usual deshielded positions around 7.2 ppm and the central methylene protons in the aliphatic bridge are even severely shielded to a position of around - 0.5 ppm, that is, even shielded compared to the internal reference tetramethylsilane. With respect to the diamagnetic ring current criterion for aromaticity this cyclophane is still aromatic. One particular research field in cyclophanes involves probing just how close atoms can get above the center of an aromatic nucleus.〔''Molecular Iron Maidens: Ultrashort Nonbonded Contacts in Cyclophanes and Other Crowded Molecules'' Robert A. Pascal, Jr Eur. J. Org. Chem. 2004, 3763-3771 〕 In so-called in-cyclophanes with part of the molecule forced to point inwards one of the closest hydrogen to arene distances experimentally determined is just 168 picometer. A non-bonding nitrogen to arene distance of 244 pm is recorded for a pyridinophane and in the unusual superphane the two benzene rings are separated by a mere 262 pm. Other representative of this group are in-methylcyclophanes,〔Song, Q., D. M. Ho, and R. A. Pascal, Jr., A Sterically Congested In-Methylcyclophane, J. Am. Chem. Soc. 2005, 127, 11246-11247.〕 in-ketocyclophanes〔Qin, Q., J. T. Mague, and R. A. Pascal, Jr., An in-Ketocyclophane, Org. Lett. 2010, 12, 928-930.〕 and in,in-bis(hydrosilane).〔Zong, J., J. T. Mague, and R. A. Pascal, Jr., Exceptional Steric Congestion in an in,in-Bis(hydrosilane), J. Am. Chem. Soc. 2013, 135, 13235-13237.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cyclophane」の詳細全文を読む スポンサード リンク
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