Cu(I)-mediated lactone formation in subcritical water: a benign synthesis of benzopyranones and urolithins AaC

Benzopyranones were successfully synthesized using Cu(I)-mediated CaO bond formation in subcritical water. A number of benzopyranone derivatives including polymethoxy benzopyranones, benzopyranopyridones, chromenoindolones, and furochromenones were synthesized in satisfactory yield. This methodology was further applied to synthesize the intestinal microbial metabolites, urolithins A, B, and C, which were found to exhibit potent antioxidant activity.