Thermal and induced decompositions of N-alkoxycarbonyldihydropyridines: End product analysis and EPR spectra of azacyclohexadienyl radicals

PA Baguley, John Christopher Walton*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

Hydrogen abstraction from N-alkoxycarbonyldihydropyridines generated azacyclohexadienyl radicals (pyridinyl radicals) which are characterised by EPR spectroscopy. In the presence of peroxide initiators, N-alkoxycarbonyl-1,2-dihydropyridines decomposed with production of pyridine, the corresponding alkyl formate, alkyl benzoate and alkanol being formed as the major products. Absence of cyclised products in experiments with substrates containing hex-5-enyl, pent-4-enyloxy etc. units demonstrates that radical production must be minor and that N-alkoxycarbonylazacyclohexadienyl radicals do not readily undergo β-scission of the exocyclic N-C bond. The most probable mechanism is a direct 1,2-elimination of formate. The alcohols which accompanied the other products are probably formed by hydrolysis of the formates and benzoates. Analogous chemistry is displayed by N-alkoxycarbonyl-1,4-dihydropyridines at higher temperatures where 1,4-elimination of formate is too rapid for homolytic radical production to compete.

Original languageEnglish
Pages (from-to)1423-1429
Number of pages7
JournalJournal of Chemical Society, Perkin Transactions 2
Issue number6
DOIs
Publication statusPublished - Jun 1998

Keywords

  • ORGANOTIN HYDRIDES
  • 1,2-DIHYDROPYRIDINES
  • SELENOCARBONATES
  • MECHANISM
  • ALDEHYDE

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