title: Reaction of phosphinylated nitrosoalkenes with electron-rich heterocycles. Electrophilic aromatic substitution vs. cycloaddition.
abstract: The behavior of phosphinyl nitrosoalkenes with indole, pyrrole and 2,5-dimethylpyrrole is described. The reaction of nitrosoalkenes with indole leads to the formation of 3-substituted indoles. While a concerted asynchronous [4 + 2] cycloaddition process may explain the formation of 3-substituted indole when a methyl group is present at the 3-position of nitrosoalkene, the presence of a 3-methoxycarbonyl group at the same position of nitrosoalkene increases its electrophilic character, and both mechanisms, an electrophilic aromatic substitution and a [4 + 2] cycloaddition process, are predicted to be competitive, although thermodynamically the cycloaddition is favoured. Phosphinyl nitrosoalkenes react with pyrrole leading to the corresponding 2-substituted pyrroles, while the treatment of 2,5-dimethylpyrrole with these nitrosoalkenes gives rise to the formation of bicyclic 1,2-oxazines. The mechanism of the reaction of phosphinyl nitrosoalkenes with pyrrole and 2,5-dimethylppyrrole may be explained by an initial hetero-Diels-Alder cycloaddition in both cases, but only subsequent rearomatization in the case of pyrrole. Theoretical studies show very good agreement with the experimental findings and the proposed mechanisms.
authors.affiliation: Departamento de Química Orgánica I, Facultad de Farmacia, Centro de Investigaciones y Estudios Avanzados "Lucio Lascaray", Universidad del País Vasco UPV/EHU, Paseo de la Universidad 7, 01006 Vitoria, Spain. francisco.palacios@ehu.es.
authors.forename: Jesús M
authors.initials: JM
authors.lastname: de Los Santos
authors.affiliation: Departamento de Química Orgánica I, Facultad de Farmacia, Centro de Investigaciones y Estudios Avanzados "Lucio Lascaray", Universidad del País Vasco UPV/EHU, Paseo de la Universidad 7, 01006 Vitoria, Spain. francisco.palacios@ehu.es.
authors.forename: Gloria
authors.initials: G
authors.lastname: Rubiales
authors.affiliation: Departamento de Química Orgánica I, Facultad de Farmacia, Centro de Investigaciones y Estudios Avanzados "Lucio Lascaray", Universidad del País Vasco UPV/EHU, Paseo de la Universidad 7, 01006 Vitoria, Spain. francisco.palacios@ehu.es.
authors.forename: Zouhair Es
authors.initials: ZE
authors.lastname: Sbai
authors.affiliation: Departamento de Química Orgánica I, Facultad de Farmacia, Centro de Investigaciones y Estudios Avanzados "Lucio Lascaray", Universidad del País Vasco UPV/EHU, Paseo de la Universidad 7, 01006 Vitoria, Spain. francisco.palacios@ehu.es.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Ochoa de Retana
authors.affiliation: Departamento de Química Orgánica I, Facultad de Farmacia, Centro de Investigaciones y Estudios Avanzados "Lucio Lascaray", Universidad del País Vasco UPV/EHU, Paseo de la Universidad 7, 01006 Vitoria, Spain. francisco.palacios@ehu.es.
authors.forename: Francisco
authors.identifier: http://orcid.org/0000-0001-6365-0324
authors.initials: F
authors.lastname: Palacios