Nitrone-olefin (3 2) Cycloaddition
The nitrone-olefin (3+2) cycloaddition reaction is the combination of a nitrone with an alkene or alkyne to generate an isoxazoline or isoxazolidine via a +2cycloaddition process. This reaction is a 1,3-dipolar cycloaddition, in which the nitrone acts as the 1,3-dipole, and the alkene or alkyne as the dipolarophile. Mechanism and stereochemistry When nitrones are combined with either alkenes or alkynes, +2cycloaddition leads to the formation of a new C–C bond and a new C–O bond. The cycloadditions is stereospecific with respect to the configuration of the alkene; however, diastereoselectivity in reactions of C-substituted nitrones is often low. Regioselectivity is controlled by the dominant frontier orbitals interacting during the reaction, and substrates with electronically distinct substituents tend to react with high regioselectivity. Intramolecular versions of the reaction have been used to synthesize complex polyclic carbon frameworks. Reduction of the N–O linkage l ...
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