Mild and Efficient Tunable Brønsted Acidic Ionic Liquid Catalyzed <i>O</i>-Acetylation and <i>O</i>-Trimethylsilylation with Trimethylsilyl Acetate (TMSOAc) and Hexamethyldisilazane (HMDS)

Abstract

This report discloses a mild and efficient O-acetylation using easily accessible TMSOAc as a novel acetyl reagent and O-trimethylsilylation using HMDS for various alcohols catalyzed by tunable Brønsted acidic ionic liquids (TBAILs). Imidazolium-based TBAILs were prepared by a two-step atom-economic reaction and acidities measured by using UV-visible spectroscopy. Both protections for alcohols were accomplished at room temperature with good to excellent yields, while the products and TBAILs were separated by simple work-up for O-silylation and column chromatography for O-acetylation. Notably, with the simple post-process, TBAILs catalyst in this solvent free method easily recovered and recycled several times without significant degradation.

Keywords

• tunable Brønsted acidic ionic liquid
• <i>O</i>-acetylation
• <i>O</i>-trimethylsilylation
• recycle
• trimethylsilyl acetate
• HMDS