Multicomponent and multicatalytic asymmetric synthesis of furo[2,3-<i>b</i>]pyrrole derivatives: further insights into the mode of action of chiral phosphoric acid catalysts
Lara Cala, Pedro Villar, Ángel R. de Lera, Francisco J. Fañanás, Rosana Álvarez, Félix Rodríguez
Abstract
]pyrrole derivatives from simple 3-butynamines, glyoxylic acid and anilines in the presence of a dual catalytic system, formed from a gold complex and a chiral phosphoric acid. Computations, aimed to understand the exceptional performance of 9-anthracenyl-substituted BINOL-derived phosphoric acid catalyst, suggest a fundamental role of non-covalent interactions being established between the catalyst and the reagents for the outcome of the multicomponent process. The linear geometry of the anthracenyl substituent along with the presence of an electron-withdrawing group in the aniline and an aromatic substituent in the 3-butynamine derivative seem to be key structural factors to explain the experimental results and, particularly, the high stereoselectivity.