Harnessing Gold(I)-Catalyzed Hydroamination/1,3-Sulfonyl Migration Cascade for Divergent Synthesis of Isoxazolidine and Isoxazoline from <i>O</i>-Alkynyl Hydroxylamine
Santosh J. Gharpure, Dhanyakumar S. Raut, Juhi Pal
Abstract
Gold-catalyzed 5- exo-dig hydroamination on O -homopropargylic hydroxylamine gave expeditious access to methylene isoxazolidine. Excess catalyst loading led to facile 1,3-sulfonyl migration in a cascade fashion to furnish the isoxazoline. Mechanistic studies using react-IR and NMR as well as crossover experiments indicated that 1,3-sulfonyl group migration is an intramolecular concerted process. The ene-hydroxylamine moiety also underwent dipolar cycloaddition reactions with nitrile oxide and nitrones leading to the first examples of spirocyclic bis -isoxazolidine derivatives.
Topics & Concepts
HydroaminationChemistryHydroxylamineSulfonylCascadeCatalysisCascade reactionCombinatorial chemistryOrganic chemistryChromatographyAlkylCatalytic Alkyne ReactionsCyclopropane Reaction MechanismsCatalytic C–H Functionalization Methods