Bismuth Triflate–Catalyzed Friedel–Crafts Acylations of Sydnones

Abstract

Friedel–Crafts acylations of various 3-arylsydnones at the C4 position have been achieved in good yields using 4 equivalents of an alkyl anhydride and 25 mol% each of bismuth triflate and lithium perchlorate in anhydrous acetonitrile at 95 °C. Acylations appear to be faster with arylsydnones bearing electron-donating moieties and sterically unencumbered anhydrides.

GRAPHICAL ABSTRACT

Keywords:

• Acylation
• Friedel–Crafts
• mesoionic compounds
• sydnones

Notes

^a The Bi(OTf)₃ in these studies was freshly prepared from triphenyl bismuthene.

^b Unrecrystallized yield.

^a An additional equivalent of acetic anhydride and 10 mol % of Bi(OTf)₃/LiClO₄ were added after 26 h.