Sacrifice of diorganyl diselenide Enables Cyclization of Aryl Propargyl Ethers in the Synthesis of 3-Organoselenyl Chromenones

Abstract

We report the synthesis of 3-organoselenyl chromenones via a cascade cyclization of organoselenyl arylpropargyl ethers. The method is promoted by diorganyl diselenides and hydrogen peroxide. In this process, diorganyl diselenides are sacrificially activated to generate reactive selenium species. These species enable alkyne functionalization, followed by ring closure and carbonyl insertion. Unlike classical approaches, the chromenone carbonyl group is generated in situ during cyclization, removing the need for pre-installed carbonyl functionalities. A broad range of diorganyl diselenides and substituted arylpropargyl ethers were evaluated. The protocol afforded the desired chromenones in moderate to excellent yields with good functional-group tolerance. Crossover and control experiments demonstrate that the selenium atom at the C3 position of the chromenone framework comes exclusively from the externally added diorganyl diselenide. It does not originate from the prefunctionalized substrate. Although the diselenide is used sacrificially, it is fully regenerated and recovered at the end. This highlights the protocol's sustainability and atom-economical nature. Mechanistic studies support a predominantly radical pathway for selenium-mediated cyclization. The synthetic utility of the products was demonstrated by their conversion into organoselenyl pyrimidines via amidine-mediated reactions.