A Simple and Highly Efficient One-Pot Procedure for the Synthesis of Amides via Beckmann Rearrangements Using 1-Tosylimidazole (TsIm)

Abstract

A facile and highly efficient method for one-pot Beckmann rearrangement of ketoximes into N-substituted amides using N-(p-toluenesulfonyl)imidazole (TsIm) is described. In this method, ketoximes are refluxed with TsIm and Cs₂CO₃ in the presence of SiO₂ as a recyclable catalyst in DMF affording the corresponding amides in high yields. This methodology is highly efficient and regioselective for various structurally diverse ketoximes including symmetrical and unsymmetrical as well as cyclic oximes. The results of quantum mechanical studies used to rationalize the experimental outcomes are discussed.

Keywords:

• Amide
• Beckmann rearrangement
• ketoxime
• SiO₂
• N-(p-toluenesulfonyl)imidazole (TsIm)

Acknowledgments

We wish to thank the Shiraz University of Technology and Shiraz University Research Councils for partial support of this work.

Notes

^a Isolated yield.

^b Anhydrous DMF.

^c No reaction.

^d (1:1) ratio.

^a Isolated yield.

^b Basic alumina.

^a Isolated yield.

^b No reaction.

^a Isolated yield.

^a All products were characterized by ¹H and ¹³C-NMR, IR, CHN and MS analysis.

^b Isolated yield.

^a The ratios were attained by HPLC analysis.

^a Charges in Mulliken unit.