Quinoxaline-based U-shaped septuple-bridged [7,7]orthocyclophanes: synthesis, solid-state structure, and self-assembly |
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Authors: | Teh-Chang Chou Kuen-Cheng Lin |
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Institution: | a Department of Applied Chemistry, Chaoyang University of Technology, Wufong, Taichung 41369, Taiwan b Department of Chemistry and Biochemistry, National Chung Cheng University, Minsyong, Chiayi 621, Taiwan |
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Abstract: | We report a three-step synthesis of 12 septuple-bridged 7,7]orthocyclophanes 11 comprising (i) two quinoxaline-based sidewalls and (ii) a linker built-in with a succinimide ring that carries phenyl, p-methoxyphenyl, p-hydroxyphenyl, or p-methoxybenzyl appendants. The synthesis began from the Diels-Alder adduct of 1,2,3,4-tetrachloro-5,5-dimethoxycyclopentadiene (1) and succinimide ring-fused dioxatetracyclodecadiene 9, followed by ruthenium-promoted oxidation of dichloroetheno-bridges in the adduct to generate a bis-α-diketone, which was then condensed with an arene-1,2-diamine to construct sidewalls (phane parts), furnishing U-shaped septuple-bridged 7,7]orthocyclophanes 11 embedding quinoxaline, dimethylquinoxaline, or benzoquinoxaline rings. Concentration-variant 1H NMR spectra of N-p-methoxybenzyl substituted orthocyclophanes (11zd, 11xd, and 11yd) and single-crystal structures of four orthocyclophanes (11xa, 11yd, 11zb, and 11zd) revealed that the U-shaped septuple-bridged 7,7]orthocyclophanes 11 have a tendency of self-assembly, forming V-shaped dimeric entities driven chiefly by intermolecular π-π stacking interaction in both solid state and solution of high concentration. |
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Keywords: | Orthocyclophanes Self-assembly π-π stacking interaction Quinoxaline |
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