A Direct Method for the Efficient Synthesis of Benzylidene Acetal at Room Temperature

For the first time, a metal-free direct method has been developed for the efficient synthesis of benzylidene acetal at room temperature using Dowex 50WX8 as a solid acid catalyst and Cl 3 CCN as a novel water scavenger. At room temperature, a wide variety of aryl and α,β-unsaturated aldehydes react readily with functionalized 1,2- and 1,3-diols to furnish the corresponding acetals in very good yields. Labile functional groups, like N-Boc, N-Cbz, -OTBDMS, -OBn, -N 3 and acetonide are found to be stable under the reaction conditions. The versatility of this method is further demonstrated with carbohydrate substrates and optically active diols.