Free radical reactions for heterocycle synthesis. Part 3: Formation of novel spirodilactones, spirolactone-lactams, and spirolactone-thiolactones

Synthesis of spirodilactones is achieved by intramolecular free radical Michael addition of enol esters derivatized from tetronic acid. Synthesis of spirolactone-lactams and spirolactone-thiolactones is also covered by the scope of this new reaction.