Abstract
Silica phosphoric acid was used as an efficient, mild, and recyclable solid catalyst for the synthesis of acylals from various structurally diverse aldehydes and acetic anhydride under solvent-free conditions. The acylation of aldehydes was highly chemoselective, and no ketone was acylated, which provided a method for the synthesis of acylals from aldehydes in the presence of ketones. Silica phosphoric acid–catalyzed deprotection of acylals to the corresponding aldehydes in MeOH has also been developed with excellent yield. The deprotection of the acylals of aromatic aldehydes took priority over those of aliphatic aldehydes.
ACKNOWLEDGMENTS
The authors thank NNSF of China (No. 20972142), the State Key Laboratory of Bio-organic and Natural Products Chemistry, Chinese Academy of Sciences (CAS), the Natural Science Project of Henan Province (2009A150030, 082300420110), and the Innovation Fund of Zhengzhou University (2008CXSY147) for financial support.
Notes
a The isolated yield.
b All the products were characterized by 1H NMR, IR, and mass spectroscopy.
c 4.0 equivalents of Ac2O.
d Time in hours.
e NR, no reaction.
a The yields refer to the isolated pure products.