title: Reactivity of electrophilic chlorine atoms due to σ-holes: a mechanistic assessment of the chemical reduction of a trichloromethyl group by sulfur nucleophiles.
abstract: σ-Holes are shown to promote the electrophilic behavior of chlorine atoms in a trichloromethyl group when bound to an electron-withdrawing moiety. A halogen bond-type non-covalent interaction between a chlorine atom and a negatively charged sulfur atom takes place, causing the abstraction of such a chlorine atom while leaving a carbanion, subsequently driving the chemical reduction of the trichloromethyl group to a sulfide in a stepwise process. The mechanism for the model reaction of trichloromethyl pyrimidine 1 with thiophenolate and thiophenol to yield phenylsulfide 4 was followed through1H-NMR and studied using DFT transition state calculations, and the energy profile for this transformation is fully discussed. MP2 calculations of the electrostatic potential were performed for a series of trichloromethyl compounds in order to assess the presence of σ-holes and quantify them by means of the maximum surface electrostatic potential. Such calculations showed that the chlorine atoms behave as electrophilic leaving groups toward a nucleophilic attack, opening a new possibility in the synthetic chemistry of the trichloromethyl group.
authors.affiliation: Centro Conjunto de Investigación en Química Sustentable UAEM - UNAM, Carretera Toluca-Atlacomulco km 14.5, Unidad San Cayetano, Personal de la UNAM, Toluca 50200, Estado de México, Mexico. jbarroso@unam.mx and Facultad de Química, Universidad Autónoma del Estado de México, Paseo Colón/Paseo Tollocan, s/n, Toluca 50000, Estado de México, Mexico.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Caballero-García
authors.affiliation: Facultad de Química, Universidad Autónoma del Estado de México, Paseo Colón/Paseo Tollocan, s/n, Toluca 50000, Estado de México, Mexico.
authors.forename: Moisés
authors.initials: M
authors.lastname: Romero-Ortega
authors.affiliation: Centro Conjunto de Investigación en Química Sustentable UAEM - UNAM, Carretera Toluca-Atlacomulco km 14.5, Unidad San Cayetano, Personal de la UNAM, Toluca 50200, Estado de México, Mexico. jbarroso@unam.mx.
authors.forename: Joaquín
authors.identifier: http://orcid.org/0000-0003-0554-7569
authors.initials: J
authors.lastname: Barroso-Flores