Newman-Kwart Rearrangement Enabled by Flavin Photoredox Catalysis

Abstract The Newman-Kwart Rearrangement (NKR) is a valuable transformation for accessing thiophenol derivatives from readily available phenols. Traditional methods for conducting the NKR are often limited by harsh reaction conditions, operational scalability, and reactions run in primarily organic solvents. Herein, we introduce a bioinspired approach to perform the NKR using (–)-riboflavin as a cheap and effective photocatalyst. The reaction has been demonstrated on a broad range of substrates in high yield, with low catalyst loadings, and under blue and green light irradiation. A combination of mechanistic and spectroscopic experiments suggests that the reaction is initiated by a photoinduced single electron transfer event between (–)-riboflavin and the starting O-aryl thiocarbamate. The developed NKR is demonstrated on gram scale and is compatible with biological buffers.