Visible Light/Molecular-Iodine-Mediated Intermolecular Spirolactonization Reaction of Olefins with Cyclic Ketones.

In this study, intermolecular spirolactonization via an iodine/visible-light-mediated C-C/C-O bond formation reaction was developed. The developed reaction proceeded to form quaternary carbon centers via carboesterification between cyclic β-keto esters and olefins, affording spirolactone derivatives in a single step. In addition, the mechanistic investigation revealed that the generation of iodine radicals from molecular iodine driven by visible-light irradiation is a crucial step. The developed reaction proceeded under milder conditions than previously reported procedures as iodine played a role of a conventional transition-metal catalyst, realizing an environmentally friendly, novel molecular transformation.