Benzo-9-crown-3 ether trimerizes in the presence of FeCl3 and aqueous H2SO4 to produce tris(9-crown-3)triphenylene in 25.4% yield. This compound crystallizes in the monoclinic P21/c space group: a = 13.759(2) Å, b = 13.318(2) Å, c = 13.399(2) Å, β = 96.883(2)°, with Z = 4. The three 9-crown-3 ether units of the trimer possess different geometries and there is substantial deviation from coplanarity in the three aromatic rings. 13C NMR chemical shifts in the solid state are consistent with this lack of symmetry and are discussed in terms of the X-ray crystal-structure data.

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Keywords Crown ether, Stereochemistry, Trimerization
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Journal Canadian Journal of Chemistry
Buchanan, G.W, Rastegar, M.F., & Yap, G.P.A. (2001). Synthesis, X-ray crystal structure, and solid-state 13C NMR study of tris(9-crown-3)triphenylene. Canadian Journal of Chemistry, 79(2), 195–200. doi:10.1139/cjc-79-2-195