Preparative Scale Demonstration and Mechanistic Investigation of a Visible Light-Mediated Radical Smiles Rearrangement

A visible light-mediated Smiles rearrangement providing the difluoroethanol motif has been shown to reliably operate on preparative scale up to 100 g of starting material. Mechanistic investigation has revealed the reaction proceeds predominantly via a radical chain process that in some instances can be initiated via visible light or thermal activation in the absence of a photocatalyst. The reaction was demonstrated in continuous flow, with visible light and thermal initiation using a thiophene substrate relevant to pharmaceutical development.