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Structure of an Unsymmetrical Isomer from the Attempted Synthesis of 1,8-Dicyclooctatetraenylnaphthalene

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journal contribution
posted on 04.10.2001, 00:00 by Joanne D. Kehlbeck, Stuart W. Staley
Attempted synthesis of 1,8-dicyclooctatetraenylnaphthalene (1) by the palladium(0)-catalyzed coupling of 1,8-dibromonaphthalene with cyclooctatetraenyltrimethylstannane afforded a single unsymmetrical isomer of 1 in 88% yield. Two-dimensional NMR methods and spectral synthesis were employed to assign the structure of the isomer (2). AM1 geometry-optimized structures of 2 and its isomers showed that the unexpected unsymmetrical structure of 2 results from the minimization of repulsive inter-ring H−H interactions. Compound 2 is postulated to arise via tandem [2 + 2] cycloaddition and 6π → 4π + 2σ electrocyclization reactions of 1.