X = Y - ZH SYSTEMS AS POTENTIAL 1,3-DIPOLES .27. INTRAMOLECULAR CYCLOADDITION REACTIONS OF IMINES OF CYCLIC SECONDARY ALPHA-AMINO ESTERS - DIPOLE AND CYCLOADDITION STEREOCHEMISTRY

Condensation of cyclic secondary α- amino esters with aryl aldehydes containing an ω-alkenyl group leads to intramolecular 1,3-dipolar cycloaddition, via an intermediate azomethine ylide, in good yield. The stereochemistry of the azomethine ylides is controlled by steric interactions developing during conversion of the intermediate carbinolamines to the iminium ion species and generally results in stereo specific dipole formation. There is no pronounced endo - exo selectivity in these cycloadditions and an intramolecular β-acrylate moiety is a more reactive dipolarophile than an intermolecular maleimide moiety. © 1990.