Inverse Electron Demand Diels−Alder Reactions:  Cycloaddition of Enol Ethers and Enamines with 4-Substituted 6-Nitrobenzofuroxans and a Nitroethylene Model. An ab Initio and Semiempirical Theoretical Study

The stereochemistry of the cycloaddition of nitroethylene, as a model of 6-nitrobenzofuroxans, with ethenol and vinylamine has been studied at the ab initio DFT level. MO analysis reveals that these inverse electron demand Diels−Alder reactions are under frontier orbital control. A one-step reaction...

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Bibliographic Details
Published in:Journal of organic chemistry 1997-12, Vol.62 (25), p.8687-8692
Main Authors: Pugnaud, Sylvie, Masure, Daniel, Hallé, Jean-Claude, Chaquin, Patrick
Format: Article
Language:English
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Summary:The stereochemistry of the cycloaddition of nitroethylene, as a model of 6-nitrobenzofuroxans, with ethenol and vinylamine has been studied at the ab initio DFT level. MO analysis reveals that these inverse electron demand Diels−Alder reactions are under frontier orbital control. A one-step reaction pathway involving a dissymmetrical transition state is favored relative to a two-step mechanism in which the intermediate has essentially a diradical character. Study of reactions of a series of 4-substituted 6-nitrobenzofuroxans with various enol ethers and enamines at the semiempirical AM1 level shows that in these instances a stepwise mechanism involving a short-lived diradical intermediate is likely to occur. Relative rates and stereoselectivities of these reactions as a function of the nature of reactants is discussed.
ISSN:0022-3263
1520-6904
DOI:10.1021/jo970851y