title: Selective and eco-friendly procedures for the synthesis of benzimidazole derivatives. The role of the Er(OTf)3catalyst in the reaction selectivity.
abstract: An improved and greener protocol for the synthesis of benzimidazole derivatives, starting fromo-phenylenediamine, with different aldehydes is reported. Double-condensation products were selectively obtained when Er(OTf)3was used as the catalyst in the presence of electron-rich aldehydes. Conversely, the formation of mono-condensation products was the preferred path in absence of this catalyst. One of the major advantages of these reactions was the formation of a single product, avoiding extensive isolation and purification of products, which is frequently associated with these reactions. Theoretical calculations helped to understand the different reactivity established for these reactions. Thus, we found that the charge density on the oxygen of the carbonyl group has a significant impact on the reaction pathway. For instance, electron-rich aldehydes better coordinate to the catalyst, which favours the addition of the amine group to the carbonyl group, therefore facilitating the formation of double-condensation products. Reactions with aliphatic or aromatic aldehydes were possible, without using organic solvents and in a one-pot procedure with short reaction time (2-5 min), affording single products in excellent yields (75-99%). This convenient and eco-friendly methodology offers numerous benefits with respect to other protocols reported for similar compounds.
authors.affiliation: INFIQC-CONICET and Facultad de Ciencias Químicas, Departamento de Química Orgánica, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, 5000 Argentina.
authors.forename: Natividad
authors.initials: N
authors.lastname: Herrera Cano
authors.affiliation: INFIQC-CONICET and Facultad de Ciencias Químicas, Departamento de Química Orgánica, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, 5000 Argentina.
authors.forename: Jorge G
authors.initials: JG
authors.lastname: Uranga
authors.affiliation: Dipartimento di Chimica, Università della Calabria Cubo 12C, 87036-Arcavacata di Rende (CS), Italia.
authors.forename: Mónica
authors.initials: M
authors.lastname: Nardi
authors.affiliation: Dipartimento di Scienze della Salute, Università Magna Graecia, Viale Europa, 88100-Germaneto (CZ), Italia.
authors.forename: Antonio
authors.initials: A
authors.lastname: Procopio
authors.affiliation: ICYTAC-CONICET and Facultad de Ciencias Químicas, Departamento de Química Orgánica, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, 5000 Argentina.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Wunderlin
authors.affiliation: INFIQC-CONICET and Facultad de Ciencias Químicas, Departamento de Química Orgánica, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, 5000 Argentina.
authors.forename: Ana N
authors.initials: AN
authors.lastname: Santiago
keywords: catalysis; charge density; condensation; erbium(III) trifluoromethanesulfonate; green procedure; heterocycle