Heterogeneous photocatalytic C4 remote fluorosulfonamidation of pyridines

Abstract

N-Fluorosulfamoyl pyridinium salts have been ingeniously developed as redox-active precursors for generating fluorosulfamoyl radicals. However, the ubiquitous pyridine scaffold within these compounds, commonplace in numerous pharmaceuticals, has remained being wasted in reported methods only as a radical leaving group. This underutilization presents both a significant challenge and an exciting opportunity for further research in synthetic, medicinal, and materials chemistry. Herein, N-fluorosulfamoyl pyridinium salts were employed as bifunctional reagents to achieve remote and selective C–H functionalization of pyridines through a radical relay process that enables polarity reversal of radical intermediates. By employing ZnIn₂S₄ as a heterogeneous photocatalyst, this protocol enables the mild and efficient incorporation of both fluorosulfamoyl and pyridyl groups into alkenes, affording synthetically valuable fluorosulfamoyl pyridine derivatives in moderate to good yields. These transformations feature broad substrate scope, good functional group tolerance, and their synthetic utility is further demonstrated through late-stage functionalization of complex bio-relevant molecules. Importantly, the ZnIn₂S₄ photocatalyst displays exceptional recyclability, retaining high catalytic efficiency over five consecutive cycles. This work represents the first successful application of a heterogeneous photocatalyst compatible with N-fluorosulfamoyl pyridinium salts and N-aminopyridinium salts, effectively overcoming the longstanding challenge of catalyst recovery encountered in previous systems.