An interesting library of spiro[pyrrolidine-2,3'-oxindoles] of type 25 was prepared by applying a three-component 1,3-dipolar cycloaddition reaction of isatins (21), a-amino acids (22) and trans chalcones (24) , The isatin formed with the a-amino acid an azomethineylide (23) which was then trapped by the chalcone according to Scheme 14 to yield the final products. In this way, the authors have synthesized a library of 25 600 individual compounds of type 25.
The reaction was performed in closed vials at 80° C. Isatines and chalcones were dispensed from 0.25 M solutions in dioxane while amino acids were added as 0.25 M aqueous solutions. The products were obtained as racemates in high purity directly after evaporation of the solvent. The trans chalcones used in the reaction were easily prepared from commercially available acetophenones and arylaldehydes.
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