An enantioselective aza-Friedel–Crafts reaction of 5-aminoisoxazoles with isatin-derived <i>N</i>-Boc ketimines
Hui Liu, Yingkun Yan, Min Li, Xiaomei Zhang
Abstract
By employing a chiral phosphoric acid as a catalyst, an enantioselective aza-Friedel-Crafts reaction of 5-aminoisoxazoles with isatin-derived N-Boc ketimines was realized. The reaction provided a wide variety of novel 3-isoxazole 3-amino-oxindoles with good yields (up to 99%) and moderate to good enantioselectivities (up to 99%). The absolute configuration of one product was assigned by X-ray crystal structural analysis and a plausible reaction mechanism was proposed. In addition, a scale-up reaction was performed successfully. Finally, one product was subjected to Suzuki-Miyaura coupling with phenylboronic acid to afford the product in a moderate yield without erosion of the enantioselectivity.
Topics & Concepts
Enantioselective synthesisIsatinFriedel–Crafts reactionPhosphoric acidOrganic chemistryCatalysisChemistryBrønsted–Lowry acid–base theoryAsymmetric Synthesis and CatalysisChemical Synthesis and AnalysisSynthetic Organic Chemistry Methods