Reaction of Methyl Vinyl Sulfone with Schiff Bases Derived from α-Alanine Methyl Ester and Aromatic Aldehydes

Abstract

Schiff bases derived from α-alanine methyl ester and aromatic aldehydes reacted with methyl vinyl sulfone in toluene at 20°C in the presence of silver acetate and 1.5 equiv of triethylamine to give the corresponding 1,3-dipolar cycloaddition products, methyl (2S*,4S*,5S*)-5-aryl-4-methanesuffonylpyrrolidine-2-carboxylates containing a small impurity (8–25%) of diastereoisomeric (2S*,4R*,5S*)-5-aryl-4-methanesulfonylpyrrolidine-2-carboxylates. The same compounds were formed when the reaction was carried out in boiling toluene, but in this case the (4S*)-diastereoisomer was the minor product. The stereoselectivity of the cycloaddition reactions was interpreted by DFT/PBE calculations of the energies of the final products and transition states.