Enantioselective Synthesis of Cyclic Nitrones by Chemoselective Intramolecular Allylic Alkylation of Oximes

The enantio- and chemoselective iridium-catalyzed N-allylation of oximes is described for the first time. Intramolecular kinetic resolution provides access to cyclic nitrones and enantioenriched aliphatic allylic alcohols. Salient features of this transformation are its ability to employ E/Z-isomeric mixtures of oxime starting materials convergently and high functional group tolerance. The implementation of N-allylation/1,3-dipolar cycloaddition reaction sequences furnishes tricyclic isoxazolidines in highly enantio- and diastereoselective fashion. The synthetic utility of the approach is demonstrated by the efficient, formal synthesis of the marine natural product (+)-halichlorine.

Automated summary

The study introduces the enantio- and chemoselective N-allylation of oximes, yielding cyclic nitrones and enantioenriched aliphatic allylic alcohols through intramolecular kinetic resolution. The method stands out for its ability to utilize E/Z-isomeric oxime mixtures convergently and high functional group tolerance, showcasing its synthetic utility with the formal synthesis of (+)-halichlorine.