Diastereoselective synthesis of dispiro[indoline-3,3′-furan-2′,3′′-pyrrolidine] via [3 + 2]cycloaddition reaction of MBH maleimides of isatins and 1,3-dicarbonyl compounds

Abstract

In the presence of mixed bases DABCO and K₂CO₃, the reaction of MBH maleimides of isatins with various cyclic 1,3-dicarbonyl compounds such as 1,3-cyclohexanedione, dimedone, 4-hydroxychromenone and benzoylacetonitrile afforded functionalized dispiro[indoline-3,3′-furan-2′,3′′-pyrrolidines] in satisfactory yields and with high diastereoselectivity. This formal [3 + 2]cycloaddition proceeded with nucleophilic substitution of an allylammonium ylide and oxa-Michael addition of an enolate. However, a similar reaction of MBH adducts of isatins derived from acrylonitrile and methyl acrylate resulted in functionalized spiro[indoline-3,4′-pyranes] in good yields through formal [3 + 3]cycloaddition reaction.