Synthesis, Structural Analysis, and Properties of [8]Circulenes


  • Metal-Catalyzed Reactions of Alkynes. Part XIV. This work was supported by the National Science Council of Taiwan (NSC 101-2628M-006-002-MY3 and NSC 99-2113M-260-007-MY3). We also thank Prof. S.-L. Wang and Ms. P.-L. Chen (National Tsing Hua University, Taiwan) for the X-ray structure analysis.


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Polygons: [8]Circulenes were easily prepared by Pd-catalyzed annulations of tetraiodotetraphenylenes with alkynes. Their saddle-shaped structure with an [8]radialene character was identified by X-ray crystallography. Similar to 1,3,5,7-cyclooctatetraene, they have a tub-shaped eight-membered ring, but all of the bond lengths and bond angles are almost equal. Variable-temperature NMR investigations showed interesting dynamic behavior.