Solvent-Free Friedel–Crafts Cyclization with Trichloroacetic Anhydride

Abstract

Friedel–Crafts cyclization products were obtained using 1.1 equivalents of environmentally benign trichloroacetic anhydride as sole reagent and solvent. The resulting ketones included benzothiepins, benzothiopyrans, benzoxepins, dibenzothiepins, dibenzoxepins, and tetralones.

Keywords:

• Benzothiepins
• benzothiopyrans
• benzoxepins
• dibenzothiepins
• dibenzoxepins
• Friedel–Crafts cyclization
• tetralones

ACKNOWLEDGMENTS

The authors gratefully acknowledge Dennis Heyer for frequent and varied discussions and Pascal Toma for the use of the automated DSC/MP apparatus.

Notes

^a 16 h. The yield at 36 h was 84%. Material was compared to authentic 1-tetralone by HPLC only.

^b Yield adjusted for 85% purity of input material.