1,3-dipolar cycloaddition of Schiff bases and electron-deficient alkenes, catalyzed by α-amino acids

L-alpha-Amino acids catalyze 1,3-dipolar cycloaddition of methyl alpha-benzylideneamino acids to electron-deficient olefins in different solvents at room temperature. L-alpha-Amino acids ensure stereoselective formation of the corresponding syn,syn-azomethine ylides. The subsequent reaction with an active dipolarophile is stereospecific; it occurs as endo-cycloaddition with low asymmetric induction (up to ee 12%.). 3,4-Substituted 5-arylprolines were obtained in preparative yields using L-pyroglutamic acid or L-proline as catalyst.