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Catalyzed by a Cinchona-based thiourea, the [3+2] cycloadditions of barbiturate-based olefins with 3-isothiocyanatooxindoles proceeded readily, and furnished dispirobarbiturates in excellent chemical yields with excellent diastereo- and enantioselectivities. The absolute configuration of dispirobarbiturates was firmly confirmed by an X-ray single crystal structure analysis. A reaction mechanism was proposed to account for the enantioselective formation of dispirobarbiturates. [ABSTRACT FROM AUTHOR]

In the presence of a Cinchona alkaloid-based squaramide organocatalyst, the [3+2] cycloaddition of isatin-derived azomethine ylides with maleimides proceeded readily, thus delivering the desired pyrrolidine-fused spirooxindoles in 61-89% yields with >20:1 dr and 12 to >99 % ee. The absolute configuration of 5-chloro-1,5′-dimethyl-3′-phenyl-3′,3a′-dihydro-2′ H-spiro[indoline-3,1′-pyrrolo[3,4- c]pyrrole]-2,4′,6′(5′ H,6a′ H)-trione was unambiguously determined by means of X-ray single crystal structure analysis. The reaction mechanism was hypothesized to account for the enantioselective formation of 5-chloro-1,5′-dimethyl-3′-phenyl-3′,3a′-dihydro-2′ H-spiro[indoline-3,1′-pyrrolo[3,4- c]pyrrole]-2,4′,6′(5′ H,6a′ H)-trione. [ABSTRACT FROM AUTHOR]

In the presence of cinchona-thiourea organocatalyst C1, the developed organocatalytic three-component cascade reaction of isatins, malononitrile, and 2-hydroxynaphthalene-1,4-diones readily proceeded to furnish chiral pyranonaphthoquinone-fused spirooxindoles in excellent chemical yields and high enantioselectivities (up to 99 % yield and 97 % ee). The absolute configurations of the spirooxindoles were assigned on the basis of an X-ray single crystal structure. Moreover, a reaction mechanism is proposed that accounts for the stereocontrolled formation of the chiral spirooxindoles,. [ABSTRACT FROM AUTHOR]

In the presence of the Cinchona alkaloid-based squaramide organocatalyst QSQ, the [3+2] cycloaddition of isatin-derived azomethine ylides with maleimides proceeds readily to deliver pyrrolidine-fused spirooxindoles. [ABSTRACT FROM AUTHOR]