First examples of Friedel–Crafts alkylation using ketals as alkylating agents: an expeditious access to the benzene-fused 8-oxabicyclo[3.2.1]octane ring system

A novel acid-catalyzed intramolecular Friedel–Crafts alkylation (cyclization) using a spiroketal as electrophile leading to the otherwise not easily accessible benzene-fused 8-oxabicyclo[3.2.1]octane ring system in synthetically useful yields is reported. Slightly more than one equivalent of BF3·OEt2 in THF at refluxing temperature are found to be the most satisfactory conditions to achieve the desired cyclization. An electron-donating group para to the position where cyclization will take place greatly facilitates the reaction.