Two Approaches for the Conversion of Primary Sulfonamides to Sulfonyl Fluorides

Abstract

This report describes two complementary methods for converting primary sulfonamides (RSO2NH2) into the corresponding sulfonyl fluorides (RSO2F). The first involves the copper-mediated fluorination of sulfonyl radicals generated photochemically from sulfonyl imines. This transformation leverages KF as the fluorine source and proceeds at room temperature under 390 nm irradiation. The second involves the electrophilic fluorination of sulfinate salts (RSO2–) generated via N-heterocyclic carbene-catalyzed deamination of primary sulfonamides. The reaction proceeds via a telescoped two-step sequence with initial formation of RSO2– followed by fluorination with N-fluorobenzenesulfonimide (NFSI) or SelectFluor. This latter transformation affords modest to high yields, including in the presence of unprotected anilines, carboxylic acids, and phenols, functional groups that are incompatible with many other methods for converting RSO2NH2 to RSO2F.