Metal Triflate–Catalyzed Friedel–Crafts Acetylation of 3-Phenylsydnone

Abstract

Friedel–Crafts acetylation at the 4-position of 3-phenylsydnone (1) was achieved via thermal heating overnight in moderate to good yields by employing various metal triflate catalysts (5–20 mol%), lithium perchlorate (0–20 mol%), and acetic anhydride (4 equivalents) using either acetonitrile or acetic anhydride, in excess, as solvent. Six commercially available, homogeneous metal triflate catalysts were investigated, and optimal conditions were determined. The best yields overall were achieved with indium triflate.

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GRAPHICAL ABSTRACT

Keywords:

• Acetylation
• Friedel–Crafts
• metal triflates
• sydnones