Convenient Preparation of 3,6‐Anhydro Sugars via Intramolecular Cyclization of 6‑ <i>O</i> ‑Tosyl Pyranosides Promoted by a Catalytic Amount of TBAF

Abstract 3,6‐Anhydro sugars are one of most common anhydro sugars in bioactive compounds and natural products. Herein, a high‐yielding, mild, and environmentally friendly synthetic approach for 3,6‐anhydro sugars was established via the intramolecular cyclization of 6‐ O ‐tosyl pyranosides, promoted by a catalytic amount of tetrabutylammonium fluoride (TBAF) and Na 2 CO 3 as a cocatalyst. The advantages include avoidance of protection at the 2,4‐positions, free of strong bases, minimization of excessive TBAF usage, and extensive substrate applicability, contributing to its efficiency and versatility especially for large‐scale preparations.