One-pot non-isocyanate urethane synthesis via visible light-activated Curtius rearrangement

• The Curtius rearrangement, which generates isocyanates without using phosgene, was performed for the first time under visible light. • Visible light one-pot reaction enabled the first-time synthesis of small molecules, polymer chain-end, and surface urethane modification. • It was demonstrated that increasing electron density leads to an absorption mismatch in the Curtius rearrangement. • DFT calculations and experiments revealed reaction depends on the microenvironment, including solvent and nucleophile presence. Curtius rearrangement is a highly versatile and powerful synthetic strategy for converting acyl azides into isocyanates. Herein, we introduce a visible-light-induced non-isocyanate method as an innovative ligation approach for urethane linkage formation, enabling the photochemical in situ generation of isocyanates under mild conditions. We design conjugated acyl azide molecules and successfully integrate these into diverse ligation processes, showcasing their versatility in small molecule synthesis, polymer chain-end functionalization, and surface modification of both inorganic and organic substrates. The resulting small molecules and materials were comprehensively characterized using nuclear magnetic resonance (NMR), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), ultraviolet–visible (UV–Vis) and fluorescence spectroscopy, contact angle (CA) measurements, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Critically, density functional theory (DFT) calculations provided molecular-level insights into the reaction mechanism, revealing how electronic effects influence the initiation efficiency of acyl azides. Our simple yet highly efficient visible-light-driven ligation strategy paves the way for new applications in the fabrication of complex macromolecular architectures, advanced biomaterials, as well as hydrogel networks.