Conjugate Addition of Hydroxylamines, Oximes and Hydroxamic Acids

1 General Introduction

2 Conjugate Addition of Hydroxylamine and Itsderivatives

3 Conjugate Addition of Oximes

4 Conjugate Addition of Hydroxamic Acids

5 Conclusions

6 Acknowledgments

The conjugate addition of hydroxylamines, oximes and hydroxamic acids provides convenient route to incorporate an NO 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.

Keywords: Conjugate addition, Hydroxylamines, Oximes, Hydroxamic acids, 1,4-Adducts, Michael acceptor, Concerted cycloaddition, Asymmetric conjugate addition, Nitrone