Participation of alkoxy groups in reactions of acetals: violation of the reactivity/selectivity principle in a Curtin-Hammett kinetic scenario.

Nucleophilic substitution reactions of acetals having benzyloxy groups four carbon atoms away can be highly diastereoselective. The selectivity in several cases increased as the reactivity of the nucleophile increased, in violation of the reactivity/selectivity principle. The increase in selectivity with reactivity suggests that multiple conformational isomers of reactive intermediates can give rise to the products.