title: Preparation of 13C4-6-methyl anthranilic ester via a Diels-Alder-type process. an experimental and theoretical study to characterize an unexpected isotope exchange.
abstract: 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 (13)C 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. [reaction: see text]
authors.affiliation: Departamento de Química Orgánica, Universidade de Vigo, 36310 Vigo, Spain.
authors.forename: J Lorenzo
authors.initials: JL
authors.lastname: Alonso-Gómez
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Pazos
authors.forename: Armando
authors.initials: A
authors.lastname: Navarro-Vázquez
authors.forename: Johan
authors.initials: J
authors.lastname: Lugtenburg
authors.forename: M Magdalena
authors.initials: MM
authors.lastname: Cid