Ethyl 2-Cyano-2-(2-nitrobenzenesulfonyloxyimino) Acetate (ortho-NosylOXY)-Mediated Double Beckmann Rearrangement of Ketoximes under Microwave Irradiation: A Mechanistic Perception

Dharm Dev, Tapasi Kalita, Tanmay Mondal, Bhubaneswar Mandal

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

A method for Beckmann rearrangement using ethyl 2-cyano-2-(2-nitrobenzenesulfonyloxyimino) acetate (o-NosylOXY) under microwave irradiation is reported. Ketoximes (19 examples) are converted to the corresponding amides/lactams with 69–97% yields in ∼10 minutes without any Lewis acid or co-catalyst. This is an example of halogen-free organocatalytic Beckmann rearrangement. Nuclear magnetic resonance (NMR)- and high-resolution mass spectrometry (HRMS)-based detailed mechanistic investigation suggest that o-NosylOXY acts as an initiator. Such initiators are reported before based on density functional theory (DFT) calculations. However, we report here the HRMS signatures of two transient intermediates, the nitrilium ion and the nitrilium ion's dimeric species. Rigorous NMR-based investigation of the reaction mechanism is performed. Our results indicate that the reported Beckmann rearrangement proceeds via two consecutive rearrangements. (Figure presented.).

Original languageEnglish
Pages (from-to)1427-1435
Number of pages9
JournalAdvanced Synthesis and Catalysis
Volume363
Issue number5
DOIs
StatePublished - 2 Mar 2021
Externally publishedYes

Keywords

  • Beckmann Rearrangement
  • amides
  • microwave heating
  • organic catalyst

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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