Nanostructured BiSI-Catalyzed One-Pot Photoredox Amidation, Thioesterification and Thiol-Ene/Yne Click Reactions via Radical Mechanism Under Visible Light

Abstract

Amide bond formation is a fundamental transformation in the synthesis of biologically active molecules; however, concerns about the inefficiency and ecological footprint of commonly used methodologies have intensified interest in improving this reaction. In this work, we report a visible-light-driven photocatalytic method for the formation of amides, thioesters, and thioethers using bismuth sulfoiodide (BiSI) as a heterogeneous photocatalyst. The developed approach demonstrates broad substrate tolerance, accommodating both electron-donating and electron-withdrawing substituents while maintaining high turnover numbers and excellent reaction efficiency. BiSI, a chalcohalide with a narrow band gap (1.81 eV), functions as a visible-light-responsive photocatalyst by facilitating the generation of radicals from thioacids.Supporting evidence for the hole-driven radical pathway was obtained through electron/holequenching studies, radical-trapping assays, and time-resolved NMR analysis. This study introduces a green protocol for amide, thioester, and thioether formation, further extending the utility of BiSI in organic photoredox catalysis. The synthetic utility was demonstrated by the formation of key drug molecules, including paracetamol, phenacetin, and moclobemide.