Copper(II) Trifluoromethanesulfonate as an Efficient, Versatile, and Dual-Purpose Catalyst for the Regioselective Acetylation of <scp>l</scp> -Sorbose under Neat and Solvent-Directed Conditions

<b>Herein</b>, we report that copper-(II) trifluoromethanesulfonate [Cu-(OTf)₂], a stable, versatile, and dual-purpose catalyst, efficiently catalyzed the acetylation of l-sorbose under various conditions following metal trifluoromethanesulfonate screening. Regioselectivity is critically governed by solvents: solvent-free reactions favor the open-chain <i>keto</i>-sorbopentaacetate, whereas coordinating solvents direct acetylation toward the cyclic α-l-sorbopyranosyl tetraacetate. These findings underscore the pivotal role of solvents in steering reaction pathways, enabling selective and sustainable synthesis of structurally distinct sugar derivatives while using a minimal amount of catalysts.