1,3-Dipolar cycloadditions of five and six membered cyclic nitrones to α,β-unsaturated acid derivatives

The cycloadditions of 3,4-dihydro-2H-pyrrole 1-oxide, 3,4,5,6- tetrahydropyridine 1-oxide, and (S)-3,4-dihydro-2-hydroxymethyl-2H-pyrrole 1- oxide to α,β-unsaturated acid derivatives have been reviewed. As Z-olefins, several five, six, and seven membered lactones with different functionalization at the γ-position were employed. As E-olefins, γ-hydroxy- , γ-alkoxy-, and γ-oxo-α,β-unsaturated esters have been incorporated to this study. Steric factors play a very important role in the regio- and stereochemical outcome of these 1,3-dipolar cycloadditions, cis-Olefins yield products derived mainly from an exo transition state, while the cycloadducts of trans-olefins result mainly from endo approaches.