Visible-Light-Mediated Synthesis of Biscoumarins Utilizing Photocaged Sulfonic Acid as the Catalyst

Abstract

Throughout the years, biscoumarin derivatives, known for their diverse biological properties, have attracted extensive synthetic interest. In pursuit of a sustainable, versatile, and cost-effective protocol, we studied the reaction between 4-hydroxycoumarin and various aldehydes, using arylazo sulfones as the photoacid generators. Hence, we developed a mild, visible-light-driven approach for the synthesis of biscoumarins, utilizing arylazo sulfones under 467 nm irradiation, affording products in moderate-to-high yields. The effectiveness and the limited waste production of our protocol, combined with its simplicity, including the purification by recrystallization, highlight its great potential for pharmaceutical applications.