1,3-dipolar cycloaddition of schriff bases and electron-deficient alkenes, catalyzed by α-Amino acids
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L-α-Amino acids catalyze 1,3-dipolar cycloaddition of methyl α-benzylideneamino acids to electron-deficient olefins in different solvents at room temperature. L-α-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.
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