Issue 2, 2006

Photochemical intramolecular aromatic substitutions of the imidazol-2-yl radical are superior to those mediated by Bu3SnH

Abstract

Six-membered photochemical cyclisations of 2-iodo-N-(2-arylethyl)imidazoles proceeded regioselectively in higher yields than the equivalent tin hydride-mediated reactions. The decrease in yield of cyclisation products, 5,6-dihydroimidazo[2,1-a]isoquinolines containing strongly deactivating substituents on the aryl ring confirmed the electrophilic nature of the σ-imidazol-2-yl radicals. The seven-membered cyclisation was only successful under photochemical conditions, as radical reduction occurred with tin hydride. Nitration of 5,6-dihydroimidazo[2,1-a]isoquinoline with nitric/sulfuric acid occurred at the 2- and 8-positions.

Graphical abstract: Photochemical intramolecular aromatic substitutions of the imidazol-2-yl radical are superior to those mediated by Bu3SnH

Article information

Article type
Paper
Submitted
12 Sep 2005
Accepted
10 Nov 2005
First published
05 Dec 2005

Org. Biomol. Chem., 2006,4, 268-277

Photochemical intramolecular aromatic substitutions of the imidazol-2-yl radical are superior to those mediated by Bu3SnH

M. A. Clyne and F. Aldabbagh, Org. Biomol. Chem., 2006, 4, 268 DOI: 10.1039/B512729G

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