title: Supported bifunctional thioureas as recoverable and reusable catalysts for enantioselective nitro-Michael reactions.
abstract: The catalytic activity of different supported bifunctional thioureas on sulfonylpolystyrene resins has been studied in the nitro-Michael addition of different nucleophiles to trans-β-nitrostyrene derivatives. The activity of the catalysts depends on the length of the tether linking the chiral thiourea to the polymer. The best results were obtained with the thiourea derived from (L)-valine and 1,6-hexanediamine. The catalysts can be used in only 2 mol % loading, and reused for at least four cycles in neat conditions. The ball milling promoted additions also worked very well.
authors.affiliation: Instituto CINQUIMA and Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Valladolid, Paseo de Belén 7, 47011-Valladolid, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Andrés
authors.affiliation: Instituto CINQUIMA and Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Valladolid, Paseo de Belén 7, 47011-Valladolid, Spain.
authors.forename: Miriam
authors.initials: M
authors.lastname: Ceballos
authors.affiliation: Instituto CINQUIMA and Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Valladolid, Paseo de Belén 7, 47011-Valladolid, Spain.
authors.forename: Alicia
authors.initials: A
authors.lastname: Maestro
authors.affiliation: Instituto CINQUIMA and Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Valladolid, Paseo de Belén 7, 47011-Valladolid, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Sanz
authors.affiliation: Instituto CINQUIMA and Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Valladolid, Paseo de Belén 7, 47011-Valladolid, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Pedrosa
keywords: bifunctional organocatalysts; organocatalysis; stereoselective nitro-Michael addition; supported catalysts; thioureas