Sulfur–Azide Exchange (SuAEx): A Click Reaction for Chemoselective Sulfonate Ester Formation

Here, we report sulfur-azide exchange (SuAEx), which facilitates the efficient synthesis of sulfonate esters via the reaction of sulfonyl azides with phenolic substrates under mild conditions. The reaction tolerates a wide range of functional groups. Notably, SuAEx displays a distinct preference for phenolic hydroxyls over aliphatic alcohols, providing orthogonality critical for complex molecular editing. Its utility is further demonstrated through iterative ligation strategies when combined with azide-alkyne cycloaddition reactions.