DOUBLE DIASTEREOSELECTIVITY OF 1,3-DIPOLAR CYCLOADDITIONS OF SUBSTITUTED CYCLIC AZOMETHINE YLIDES

Seven derivatives of methyl 5-phenyl-3,4-dihydro-2H-pyrrole-2-carboxylates 1 were synthetized. These compounds are precursors of pentagonal cyclic azomethine ylids, the two sides of which are diastereotopic. The 1,3-dipolar species react with N-methyl and N-phenylmaleimides diastereospecifically. The approach of the reactant species occurs from the less hindered side of the 1,3-dipole and in endo to lead the thermodynamically stable exo cycloadduct. Moreover, oxidation of the compounds 1 gives the corresponding substituted pyrroles.