N-tosylhydrazones as acceptors for nucleophilic alkyl radicals in photoredox catalysis: A short case study on possible side reactions

Anna G. Kinsella, Joshua D. Tibbetts, Darren Stead, Alexander J. Cresswell

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Abstract

We report the attempted development of a photoredox-catalyzed α-C–H alkylation reaction of aliphatic amine derivatives, using N-tosylhydrazones as radical alkylating partners. The original intention was to intercept α-aminoalkyl radical intermediates with N-tosylhydrazones, followed by the expulsion of a sulfonyl radical by β-scission to generate N-H diazene species. Facile denitrogenation of these intermediates would remove all traces of the hydrazone moiety and provide a net C–H alkylation process. However, our plans were derailed by issues with the low reactivity of N-tosylhydrazones toward intermolecular capture by nucleophilic radicals, and several unexpected side reactions. Our findings, though unsuccessful, do serve to identify challenges for future researchers attempting to develop similar transformations.

Original languageEnglish
Pages (from-to)413-423
Number of pages11
JournalSynthetic Communications
Volume52
Issue number3
Early online date21 Jan 2022
DOIs
Publication statusPublished - 31 Dec 2022

Bibliographical note

Funding Information:
This work was funded by the Engineering and Physical Sciences Research Council (EP/S028595/1). A.J.C. thanks the Royal Society for a University Research Fellowship (UF150533), the University of Bath for a Ph.D. studentship (A.G.K.), and AstraZeneca for generous financial support. The authors gratefully acknowledge the technical staff within Chemistry at the University of Bath for technical support and assistance in this work, including the Material and Chemical Characterization Facility (MC2) (https://doi.org/10.15125/mx6j-3r54).

Keywords

  • Amines
  • hydrazones
  • photoredox
  • radicals
  • side reactions

ASJC Scopus subject areas

  • Organic Chemistry

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