Synthesis of 2-Substituted 1,3-Cycloheptanedione via a Lewis Acid Mediated Ring Expansion Reaction

We have established a new route to provide 2-substituted 1,3-cycloheptanediones via a Lewis acid mediated ring expansion reaction of cyclobutanones as the key step.The ring expansion reactions were mediated by a series of Lewis acids.Among the used Lewis acids, ZnI 2 was the most practical mediator.This route has succeeded in providing the title compounds even on a multi-gram scale.During the research, the Baeyer-Villiger oxidation of the cyclobutanones to obtain the new bicyclic lactones was also examined.The regioselective oxidation was observed in the case of chlorinated cyclobutanones.