1,3-Dipolar cycloaddition reaction for diastereoselective synthesis of functionalized dihydrospiro[indoline-3,2'-pyrroles]

The BF₃OEt₂ catalyzed one-pot 1,3-dipolar cycloaddition reaction of benzylamines, isatins and dimethyl acetylenedicarboxylate in dry methylene dichloride afforded the functionalized dihydrospiroindoline-3,2'-pyrroles] in moderate to good yields and with high diastereoselectivity. The reaction was accomplished by the tandem 1,3-dioplar cycloaddition of in situ generated azomethine ylide with acetylenedicarboxylate and the nucleophilic addition of pyrrole ring to second molecular acetylenedicarboxylate.