Mechanistic and Synthetic Investigations on the Dual Selenium-π-Acid/Photoredox Catalysis in the Context of the Aerobic Dehydrogenative Lactonization of Alkenoic Acids

Abstract

The aerobic dehydrogenative lactonization of alkenoic acids facilitated by a cooperative nonmetallic catalyst pair is reported. The title procedure relies on the adjusted interplay of a photoredox and a selenium-π-acid catalyst, which allows for the regiocontrolled construction of five- and six-membered lactone rings in yields of up to 96%. Notable features of this method are pronounced efficiency and practicality, good functional group tolerance, and high sustainability, since ambient air and visible light are adequate for the clean conversion of alkenoic acids into their respective lactones. The title method has been used as a case study to elucidate the general mechanistic aspects of the dual selenium-π-acid/photoredox catalysis. On the basis of NMR spectroscopic, mass spectrometric, and computational investigations, a more detailed picture of the catalytic cycle is drawn and the potential role of trimeric selenonium cations as catalytically relevant species is discussed.