Acid-Catalyzed Transacetalization from Glycol to Pinacol Acetals

Abstract

A one-pot transacetalization of glycol acetals, frequently used as protecting groups of the aldehyde function, into the more stable pinacol acetals is given. A clean transformation of aromatic and aliphatic substrates is possible with trifluoroacetic acid within 30 min at 0 °C. Glycol acetals derived from ketones (ketals) cannot be converted with this protocol. Deprotection of the pinacol acetals is possible with trifluoromethanesulfonic acid in the presence of water.

GRAPHICAL ABSTRACT

Keywords:

• Acetal
• aldehyde
• glycol
• pinacol
• protecting group

Notes

^a All reactions were performed with 5 mL TFA/6 mmol pinacol.

^b TFA/H₂O 4:1.

^a Reaction time 20 h.