Synthesis and Inclusion Behavior of [2.n] Naphthalenophanes Possessing Polar Groups


Department of Chemistry, Faculty of Engineering, Gunma University; 1-5-1 Tenjincho, Kiryu-shi 376-8515 Japan

[2.n] Naphthalenophanes 2--7 possessing polar substituents on the cyclobutane ring were prepared by the intramolecular [2+ 2] photocycloaddition of the corresponding, α,ω-bis(vinylnaphthyl)alkanes. Their inclusion behavior with aromatic solvents was investigated and compared with that for unsubstituted [2.n] naphthalenophanes 1a, b that afford only quite unstable inclusion crystals with aromatic solvents such as benzene and toluene.
[2.3] (1,4)Naphthalenophanes 2--4 having alkoxycarbonyl or acetyl groups and 5 having hydroxy methyl groups gave inclusion crystals with benzene and pyridine, respectively. [2.3] (1,5)Naphthalenophane 6 also provided inclusion crystals with benzene, whereas [2.5] (1,4)naphthalenophanes 7 with a pentamethylene linkage no inclusion crystals. These inclusion crystals were much more stable than those obtained from 1a, b and the ratio of naphthalenophane with solvent was different from one another.
According to the X-ray crystallographic analysis, the packing manner of the naphthalenophane and solvent was found to be remarkably dependent on the substituents, although the naphthalenophane molecules are arranged head-to-head mainly due to the intermolecular dipoledipole interaction between polar substituents. It is noteworthy that benzene molecules are accommodated in a channel along the b-axis in the crystal of 2-benzene. As demonstrated by 2 and 6, the difference in the position of trimethylene linkage hardly affected the arrangement of naphthalenophanes, but resulted in the difference in the ratio of included solvent molecules.

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