title: Mechanistic studies on Lewis acid catalyzed Biginelli reactions in ionic liquids: evidence for the reactive intermediates and the role of the reagents.
abstract: This paper describes the use of common Lewis acids supported in imidazolium-based ionic liquids as the catalysts to promote the Biginelli reaction. The ionic liquid effect and the reaction mechanism are discussed on the basis of nuclear magnetic resonance (NMR), electrospray ionization mass spectrometry (ESI-MS), and theoretical calculations. Indeed, the results showed that the ionic medium plays a fundamental role in the synthesis of biologically active dihydropyrimidinones due to the stabilization of the charged intermediates proposed in the mechanism. When conducted in an ionic liquid as solvent, the reaction mechanism is more complex than in other Lewis acid catalyzed Biginelli reactions.
authors.affiliation: Laboratory of Medicinal and Technological Chemistry, University of Brasília, Chemistry Institute, Campus Universitário Darcy Ribeiro, CEP 70904-970, P.O. Box 4478, Brasília DF, Brazil.
authors.forename: Luciana M
authors.initials: LM
authors.lastname: Ramos
authors.forename: Adrian Y
authors.initials: AY
authors.lastname: Ponce de Leon y Tobio
authors.forename: Marcelo R
authors.initials: MR
authors.lastname: dos Santos
authors.forename: Heibbe C B
authors.initials: HC
authors.lastname: de Oliveira
authors.forename: Alexandre F
authors.initials: AF
authors.lastname: Gomes
authors.forename: Fabio C
authors.initials: FC
authors.lastname: Gozzo
authors.forename: Aline L
authors.initials: AL
authors.lastname: de Oliveira
authors.forename: Brenno A D
authors.initials: BA
authors.lastname: Neto