Cinchonidine-Catalyzed Synthesis of Oxazabicyclo[4.2.1]nonanones from -Aryl--unsaturated Nitrones and 1-Ethynylnaphthalen-2-ols.

A variety of oxazabicyclo[4.2.1]nonanone derivatives were prepared in good yields through a cinchonidine-catalyzed cascade reaction of -aryl-α,β-unsaturated nitrones and 1-ethynylnaphthalen-2-ols. Mechanistic studies show that the reaction undergoes a [4 + 3] cycloaddition of nitrones to vinylidene -quinone methide generated in situ from 1-ethynylnaphthalen-2-ols in the presence of cinchonidine, 1,3-rearrangement of N-O vinyl moieties, ring-opening, and finally double intramolecular cyclizations to afford oxazabicyclo[4.2.1]nonanones over five steps in a one-pot reaction.