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Synthesis 2009(15): 2591-2595  
DOI: 10.1055/s-0029-1217402
PAPER
© Georg Thieme Verlag Stuttgart ˙ New York

Synthesis of Isoindoline Nitroxides by Electrocyclic Reactions

Tamás Kálaia, József Jekőb,c, Kálmán Hideg*a
a Department of Organic and Medicinal Chemistry, University of Pécs, P.O. Box 99, 7602 Pécs, Hungary
Fax: +36(72)536219; e-Mail: kalman.hideg@aok.pte.hu;
b ICN Hungary, P.O. Box 1, 4440 Tiszavasvári, Hungary
c Department of Chemistry, College of Nyíregyháza, Sóstói st. 31/B, 4440 Nyíregyháza, Hungary
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Publication History

Received 3 April 2009
Publication Date:
22 June 2009 (online)

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Abstract

The Suzuki reaction of the pyrroline nitroxide, 3-bromo-4-formyl-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-1-yloxyl radical, with vinylboronic acids and subsequent Horner-Wadsworth-Emmons reaction followed by electocyclic reaction of the thus formed 1,3,5-triene and oxidation offers a new route for the synthesis of 5,6-disubstituted 1,1,3,3-tetramethylisoindolin-2-yloxyl radicals. The alternative Diels-Alder reaction pathway sometimes resulted in poor yields. Starting from 5-(ethoxycarbonyl)-1,1,3,3-tetramethyl-6-phenylisoindolin-2-yloxyl radical we obtained a spin-labeled fluorenone.

Key words

cross-coupling - Diels-Alder reaction - electrocyclic reaction - free radical - Wittig reaction