title: Theoretical Study on the Mechanism of the Thermal Retro-Cycloaddition of Isoxazolinofullerenes.
abstract: The retro-cycloaddition thermal reaction of isoxazolino[4,5:1,2][60]fullerenes to pristine fullerene seems to be guided by the electronic nature of the substituted nitrile oxide 1,3-dipole in the isoxazoline ring. Trapping experiments proved that the reaction mechanism occurs by thermal removal of the nitrile oxide 1,3-dipole in a process that is favored in the presence of a big excess of a highly efficient dipolarophile such as maleic anhydride. Theoretical gas phase calculations carried out at the B3LYP/6-31G(d) and M06-2X/6-31G(d) levels of theory underpin the experimental findings and predict that compound 1c, bearing the p-(CH3)2N-Ph substituent on the isoxazoline ring and with a remarkable experimental conversion efficiency in just 12 h, showed the lowest activation energy. Solvent calculations have predicted the same behavior in gas phase. Different approaches such as electrostatic natural population analysis and Houk's distortion/interaction model have been applied to understand how the electronic nature of these substituents affects the retro-cycloaddition reaction process. Analysis of the values of the condensed Fukui functions and dual descriptor shed light on the mechanism of the retro-cycloaddition reaction.
authors.affiliation: Laboratorio de Química, Computacional y Teórica, Facultad de Química, Universidad de la Habana , 10400 La Habana, Cuba.
authors.forename: Cercis
authors.initials: C
authors.lastname: Morera-Boado
authors.affiliation: Laboratorio de Química, Computacional y Teórica, Facultad de Química, Universidad de la Habana , 10400 La Habana, Cuba.
authors.forename: Marco
authors.initials: M
authors.lastname: Martínez González
authors.affiliation: Laboratorio de Química, Computacional y Teórica, Facultad de Química, Universidad de la Habana , 10400 La Habana, Cuba.
authors.forename: Ramón A
authors.initials: RA
authors.lastname: Miranda-Quintana
authors.affiliation: Laboratorio de Síntesis Orgánica, Facultad de Química, Universidad de la Habana , 10400 La Habana, Cuba.
authors.forename: Margarita
authors.initials: M
authors.lastname: Suárez
authors.affiliation: Departamento de Química Orgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid , 28040 Madrid, Spain.
authors.forename: Roberto
authors.initials: R
authors.lastname: Martínez-Álvarez
authors.affiliation: Departamento de Química Orgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid , 28040 Madrid, Spain.
authors.forename: Nazario
authors.initials: N
authors.lastname: Martín
authors.affiliation: Departamento de Química Física Aplicada, Facultad de Ciencias, Universidad Autónoma de Madrid , 28049 Madrid, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: García de la Vega