Polystyrene-Supported, Al(OTf)₃-Catalyzed Chemoselective Synthesis of Acylals from Aldehydes

Abstract

Cross-linked polystyrene-supported aluminium triflate [Ps-Al(OTf)₃] has been shown to be a mild, efficient, and chemoselective heterogeneous Lewis acid catalyst for acetylation of aldehydes with acetic anhydride. The catalyst can be recovered simply and reused efficiently at least five times without any noticeable loss of catalytic activity.

Keywords:

• Acylal
• aldehyde
• aluminium triflate
• catalysis
• polystyrene

ACKNOWLEDGMENT

The author thanks the Research Council of Shahrekord University for partial support of this work.

Notes

^a The molar ratio of the aldehyde/Ac₂O/cat. is 1:1.5:0.1 except for entries 1i and 3, in which the molar ratio is 1:2.5:0.12.

^b Yields refer to pure isolated products, and all acylals prepared are known compounds and were characterized by comparison of their physical and spectral data with those of authentic samples.

^a The molar ratio of substrate 1 to substrate 2 to Ac₂O is 1:1:1.2 for entries 1 and 2 and 1:1:1 for entries 3 and 4.

^b All reactions were carried out in CH₂Cl₂ at room temperature in the presence of ¹ Ps-Al(OTf)₃ (0.1 mmol), ² Al(OTf)₃ (0.2 mmol), or ³ AlCl₃ (0.28 mmol).

^c GC yield.