An Unusual Intramolecular Acetal Alkylation

Upon treatment with Grignard reagents, suitably functionalized cis-fused bicyclic ketone acetals undergo intramolecular acetal alkylation to provide oxabicyclo[3.3.1]nonane derivatives. This transformation results in the formation of up to three stereogenic centers with high levels of stereoselectivity. Product distribution and stereochemistry vary with substrate substitution and the Grignard reagent utilized.