Radical Smiles Rearrangements: Aryl Migration for Molecular Editing

Smiles and Truce-Smiles rearrangements have evolved from classical nucleophilic aromatic substitutions into a versatile platform for radical aryl migration and molecular editing. This Review surveys how visible-light photoredox catalysis and related photoinduced activation modes-including electron-donor-acceptor (EDA) complexes, energy-transfer and ligand-to-metal charge-transfer (LMCT) processes, metal-hydride hydrogen atom transfer (MHAT), and radical-cation pathways-have transformed sulfonyl and sulfinyl groups into bifunctional aryl-migration handles that operate under remarkably mild conditions. After outlining the mechanistic features that distinguish ionic, radical, and radical-cation Smiles pathways, we discuss traditional radical Smiles rearrangements that established the feasibility of aryl transfer via open-shell Meisenheimer-like intermediates. We then focus on photocatalytic and catalyst-free radical Smiles and Truce-Smiles reactions, including alkene difunctionalizations, sulfur dioxide (SO₂) insertion/relay cascades, decarboxylative and decarbonylative arylations, remote sp³ carbon-hydrogen (C(sp³)-H) functionalization, and emerging applications in polymer synthesis and biocatalysis. Particular emphasis is placed on reagent design (sulfonamides, sulfones, sulfinamides, and sulfoxides), control over SO₂ extrusion versus retention, and recent advances in asymmetric sulfinyl-Smiles chemistry. We conclude by highlighting current limitations and future opportunities, especially in expanding substrate generality, stereocontrol, and late-stage functionalization, and in integrating Smiles rearrangements with electrochemical, flow, and data-driven catalysis for applications in medicinal chemistry and sustainable materials.