Volume 2003, Issue 14 p. 2626-2634
Full Paper

Regio- and Diastereoselectivity in 1,3-Dipolar Cycloaddition Reactions of 2-Phenylisatogen and Its 3-Phenylimino Derivative with Electron-Deficient Alkenes

Paola Astolfi

Paola Astolfi

Dipartimento di Scienze dei Materiali e della Terra, Università, Via Brecce Bianche, 60131 Ancona, Italy, Fax: (internat.) +39-071-2204714

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Paolo Bruni

Paolo Bruni

Dipartimento di Scienze dei Materiali e della Terra, Università, Via Brecce Bianche, 60131 Ancona, Italy, Fax: (internat.) +39-071-2204714

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Lucedio Greci

Lucedio Greci

Dipartimento di Scienze dei Materiali e della Terra, Università, Via Brecce Bianche, 60131 Ancona, Italy, Fax: (internat.) +39-071-2204714

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Pierluigi Stipa

Pierluigi Stipa

Dipartimento di Scienze dei Materiali e della Terra, Università, Via Brecce Bianche, 60131 Ancona, Italy, Fax: (internat.) +39-071-2204714

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Lara Righi

Lara Righi

Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Università, Viale delle Scienze, 43100 Parma, Italy

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Corrado Rizzoli

Corrado Rizzoli

Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Università, Viale delle Scienze, 43100 Parma, Italy

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First published: 26 June 2003
Citations: 17

Abstract

The 1,3-dipolar cycloadditions of the cyclic nitrones 2-phenyl-3H-indole-3-one N-oxide (2-phenylisatogen, 1a) and 2-phenyl-3-phenylimino-3H-indole N-oxide (1b) to several electron-deficient alkenes 2ad are reported. All the reactions studied are highly diastereoselective: the regioisomers with the ethoxycarbonyl group attached to the 4-position of the isoxazolidine moiety are the only products isolated, except in the reactions of nitrones 1a and 1b with ethyl acrylate 2a where mixtures of the two different regioisomers are obtained. Crystal structures of compounds 3b, 5a, 5b, 9a and 10b were determined by X-ray analysis, while the structure of the other cycloadducts was determined by spectroscopic analysis. Ab initio calculations were carried out showing that product distribution may be influenced by kinetic rather than thermochemical factors. Ab initio calculations of the 1H NMR shielding tensor were performed on compounds 3b, 4b, 5a and 6b and the chemical shifts obtained are in perfect agreement with the experimental ones. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)