X=Y-ZH systems as potentials 1,3-dipoles. Part 321,2 generation of nitrones from oximes. Tandem Michael addition-1,3-dipolar cycloaddition reactions. Background and class 1 processes

Article abstract of DOI:10.1016/S0040-4020(01)87116-7

Intermolecular Michael addition of aldoximes and ketoximes to electronegative olefins generates nitrones. The keto nitrones can be trapped in regiospecific intermolecular cycloaddition reactions giving single cycloadducts in good yield. Chemospecific 1:1:1 cycloadducts are obtained from ketoximes, monosubstituted electronegative olefins (Michael acceptor) and N-methylmaleimide (dipolarophile), whilst the chemoselectivity of the corresponding reactions with aldoximes is dependent on the oxime stereochemistry. Z-Aldoximes show high chemospecificity whilst E-aldoximes are much less chemoselective.