Novel Synthesis and Structures of Tris-Annelated Benzene Donors for the Electron-Density Elucidation of the Classical Mills−Nixon Effect

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American Chemical Society

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Journal of the American Chemical Society

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DOI: 10.1021/ja980805v


A versatile method for the high-yield synthesis of various tris-, bis-, and mono-annelated benzenes (as well as cyclooctatetraene) is based on the Pd-catalyzed coupling of three (or four) ethylenic units comprised of α,β-dibromoalkenes and α‘-alkenyl Grignard reagentsall carried out in a single pot. The particular application to tris(bicyclopentyl)-annelated benzene yields the syn isomer 1s in high purity; X-ray diffraction analysis confirms the aromatic bond alternation relevant to the Mills−Nixon effect. Most importantly, the efficient synthesis of 1s crystals of extraordinary quality allows us (for the first time) to make precise electron-density measurements of the “banana-type” distortion and the ellipticity (π-character) of the various aromatic C−C bondssufficient to identify the electronic origin of the classical Mills−Nixon effect. The unique electron-donor properties of tris-annelated benzenes also relate to their highly reversible one-electron oxidation potentials even in nonpolar solvents.


Accepted version. Journal of the American Chemical Society, Vol. 120, No. 24 (1998): 6012-6018. DOI. © 1998 American Chemical Society. Used with permission.

Sergey V. Lindeman and Rajendra Rathore were affiliated with the University of Houston at the time of publication.