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submitted on 05.06.2020 and posted on 08.06.2020by Tobias Sandmeier, Erick Carreira
The enantio- and chemoselective iridium-catalyzed N- and O-allylation of oximes is described for the first time. Kinetic
resolution in an intramolecular setting provides access to cyclic nitrones,
oxime ethers and enantioenriched aliphatic allylic alcohols. Salient features
of this transformation are its ability to employ E/Z-isomeric mixtures of
oxime starting materials convergently, high functional group tolerance, and divergent
N- or O-allylation by choice of the reaction conditions. The
implementation of N-allylation/1,3-dipolar
cycloaddition reaction cascades furnish tricyclic isoxazolidines in highly
enantio- and diastereoselective fashion. Expansion of this approach to the
selective allylation of hydrazones allows enantioselective preparation of
azomethine imines. The synthetic utility of the approach is demonstrated by the
efficient, formal syntheses of glycoprotein GP IIb‐IIIa
receptor antagonist (–)-roxifiban and marine natural product (+)-halichlorine.