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Thia-, Aza-, and Selena[3.3.1]bicyclononane Dichlorides: Rates vs Internal Nucleophile in Anchimeric Assistance

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journal contribution
posted on 03.06.2011 by Adrian A. Accurso, So-Hye Cho, Asmarah Amin, Vladimir A. Potapov, Svetlana V. Amosova, M. G. Finn
Sulfur-, selenium-, and nitrogen-containing compounds bearing leaving groups in the β-position undergo facile substitution chemistry enabled by anchimeric assistance. Here we provide direct comparisons between such systems in the rigid bicyclo[3.3.1]nonane framework easily derived from 1,5-cyclooctadiene. For a series of dichloride electrophiles of this type, the relative reactivities were found to be Se ≫ (alkyl)N > S ≥ (propargyl)N > (phenyl)N, with the reaction rates at the two extremes differing by more than 3 orders of magnitude. For the N-alkyl case, substitution rates were largely independent of the trapping nucleophile but were strongly dependent on solvent, showing that the process is controlled by the formation of the high-energy three-membered cationic intermediate.

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