Preparation of 13C4-6-Methyl Anthranilic Ester via a Diels−Alder-Type Process. An Experimental and Theoretical Study to Characterize an Unexpected Isotope Exchange

Buta-2,3-dienoate reacts with vinyl ketenimine to give the corresponding substituted aniline through a Diels−Alder cycloaddition. Besides the expected Diels−Alder adduct 3a, the aniline 3b was also obtained in a ratio of 91:9. The observed 13C exchange is explained on the basis of a reversible [2 +...

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Bibliographic Details
Published in:Organic letters 2005-08, Vol.7 (17), p.3773-3776
Main Authors: Alonso-Gómez, J. Lorenzo, Pazos, Yolanda, Navarro-Vázquez, Armando, Lugtenburg, Johan, Cid, M. Magdalena
Format: Article
Language:English
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Summary:Buta-2,3-dienoate reacts with vinyl ketenimine to give the corresponding substituted aniline through a Diels−Alder cycloaddition. Besides the expected Diels−Alder adduct 3a, the aniline 3b was also obtained in a ratio of 91:9. The observed 13C exchange is explained on the basis of a reversible [2 + 2] cycloaddition competing with the [4 + 2] process. This is supported by B3LYP DFT computations, as a stepwise pathway lies very close in energy to the [4 + 2] concerted one.
ISSN:1523-7060
1523-7052
DOI:10.1021/ol051433f