Synthesis of spirocyclic Δ-isoxazolines [3 + 2] cycloaddition of indanone-derived ketonitrones with alkynes.

A [3 + 2] cycloaddition of indanone-derived nitrones and alkynes under mild conditions is developed, allowing facile synthesis of spirocyclicindenyl isoxazolines with structural diversity. The sequential protocol of generated ketonitrone from unsaturated ketones and -alkylhydroxylamines is also achieved successfully, affording the desired products in considerable yield with moderate to good diastereoselectivity. Moreover, the spirocyclic product can be conveniently transformed into indenyl-based allylic alcohol and enamide.