Conjugate Addition of Hydroxylamines, Oximes and Hydroxamic Acids

Abstract

The conjugate addition of hydroxylamines, oximes and hydroxamic acids provides convenient route to incorporate an NO moiety into various Michael acceptors. This chapter reviews comprehensive experimental reactions on the formation of carbon–nitrogen and carbon–oxygen bonds via conjugate addition of hydroxylamines, oximes and hydroxamic acids to alkenes, alkynes or allenes attached to one or more electron‐withdrawing groups. Hydroxylamine derivatives predominantly undergo N‐centered conjugate addition, while for the ambient nucleophilic oximes and hydroxamic acids, both N‐centered and O‐centered conjugate addition are operative by control of the reaction conditions. A concerted cycloaddition mechanism has been well established for the conjugate addition of N ‐substituted hydroxylamines. The last decade has witnessed enormous growth in enantioselective conjugate addition of hydroxylamine derivatives and the O‐centered oximes. General Introduction Conjugate Addition of Hydroxylamine and Itsderivatives Conjugate Addition of Oximes Conjugate Addition of Hydroxamic Acids Conclusions Acknowledgments

Double Hetero-Michael Addition of N-Substituted Hydroxylamines to Quinone Monoketals: Synthesis of Bridged Isoxazolidines

“…We envisioned that an N -substituted hydroxylamine would favor 1,4-addition and eventually lead to the bridged isoxazolidine system. A literature search reveals that hydroxylamine (NH 2 OH) reacted with santonin to afford a side product isoxazolidine through a double conjugate addition . However, it is known that condensation of hydroxylamine with quinone monoketals did not provide the double conjugate addition product, but instead led to nitroso products through a 1,2-addition and an ensuing aromatization .…”