Solvent-free catalytic preparation of 1,1-diacetates from aldehydes using a Wells–Dawson acid (H6P2W18O62·24H2O)

Aromatic and aliphatic aldehydes are transformed in 1,1-diacetates (acylals) in mild conditions, by a treatment with acetic anhydride and a Wells–Dawson acid (H6P2W18O62·24H2O). gem-Diacetylation proceeds in Ac2O with a little as 1% mol Wells–Dawson acid at room temperature and under solventless conditions, obtaining very good to excellent yields (88–98%) of 1,1-diacetates (19 examples). Neither 4-dimethylaminobenzaldehyde nor ketones react under the same conditions.