Self-Assembly of Conformationally Rigid Dialcohols (Bis-Benzocyclobutenols): Supramolecular Cyclophanes and Arrays
摘要:
Bis-benzocyclobutenols are synthetically important intermediates, and their structures have been established for the first time. These unique molecular systems allow investigation of the hydrogen bond-mediated aggregation of diols with rigid disposition of the hydroxyl groups on both sides of a flat arene core, namely bis-benzocyclobutene. The syn-diols la and 2a were found to assemble via O-H center dot center dot center dot O hydrogen bonds between the hydroxyl groups into dimers, which may be termed "supramolecular cyclophanes". However, the analogous diols that are sterically encumbered by ethyl and phenyl groups were found to aggregate via adoption of tetrameric (syn-2c) or water-expanded dimeric (syn-2b) supramolecular synthons. The sterically un-hindered anti diols were found to self-assemble via helical supramolecular synthon in contrast to the sterically encumbered ones; the latter were found to display preference to undergo cyclic tetrameric aggregation. The results thus point to intriguing possibilities in the adoption of supramolecular synthons when a given diol is constrained by the obligation to exploit two or more functional groups of the same kind.
6-dipivaloyl-1,2,4,5-tetramethylbenzene were prepared by the Friedel-Grafts dipropionylation of the corresponding polymethylbenzenes, followed by the exhaustivemethylation of the resulting diketones with potassium t-butoxide and methyl iodide in boiling benzene-t-butyl alcohol. The PMR and IR spectra are reported for these new compounds.
2,4-二新戊酰基-1,3,5-三甲基苯、4,6-二新戊酰基-1,2,3,5-四甲基苯和 3,6-二新戊酰基-1,2,4,5-四甲基苯的制备方法如下:相应的多甲基苯的 Friedel-Grafts 二丙酰化,然后在沸腾的苯 - 叔丁醇中用叔丁醇钾和甲基碘彻底甲基化得到的二酮。报告了这些新化合物的 PMR 和 IR 光谱。
Self-Assembly of Conformationally Rigid Dialcohols (Bis-Benzocyclobutenols): Supramolecular Cyclophanes and Arrays
Bis-benzocyclobutenols are synthetically important intermediates, and their structures have been established for the first time. These unique molecular systems allow investigation of the hydrogen bond-mediated aggregation of diols with rigid disposition of the hydroxyl groups on both sides of a flat arene core, namely bis-benzocyclobutene. The syn-diols la and 2a were found to assemble via O-H center dot center dot center dot O hydrogen bonds between the hydroxyl groups into dimers, which may be termed "supramolecular cyclophanes". However, the analogous diols that are sterically encumbered by ethyl and phenyl groups were found to aggregate via adoption of tetrameric (syn-2c) or water-expanded dimeric (syn-2b) supramolecular synthons. The sterically un-hindered anti diols were found to self-assemble via helical supramolecular synthon in contrast to the sterically encumbered ones; the latter were found to display preference to undergo cyclic tetrameric aggregation. The results thus point to intriguing possibilities in the adoption of supramolecular synthons when a given diol is constrained by the obligation to exploit two or more functional groups of the same kind.