Issue 22, 2003

Intramolecular radical additions to pyridines

Abstract

Intramolecular 6-exo/endo-trig and 5-exo-trig cyclisations of aryl radical intermediates to the α-, β- and γ-carbons of pyridine have been shown to be facile processes at neutral pH. The tether conjoining the radical donor to the pyridine plays an important role in determining the outcome of the reaction. When a Z-alkene is used as a tether, ortho-cyclisation proceeds in good yield. A more complex course is followed when a saturated two carbon tether is employed, leading to products derived from hydrogen atom abstraction, ipso-cyclisation and ortho-cyclisation pathways. All attempts to effect 5-exo/endo-trig cyclisations failed. Tributyltin hydride, tris(trimethylsilyl)silane, tris(trimethylsilyl)germane and, in part, samarium(II) iodide can each be employed as mediators of the reaction.

Graphical abstract: Intramolecular radical additions to pyridines

Article information

Article type
Paper
Submitted
05 Aug 2003
Accepted
17 Sep 2003
First published
13 Oct 2003

Org. Biomol. Chem., 2003,1, 4047-4057

Intramolecular radical additions to pyridines

D. C. Harrowven, B. J. Sutton and S. Coulton, Org. Biomol. Chem., 2003, 1, 4047 DOI: 10.1039/B309331J

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