RESUMO
An organocatalytic three-component reaction of isatins, malononitrile and isocyanoacetates provided 3,3'-dihydropyrryl-spirooxindoles in excellent yields and enantioselectivities. The products could be readily converted to valuable 3,3'-pyrrolidinyl-spirooxindoles.
Assuntos
Indóis/síntese química , Pirróis/química , Compostos de Espiro/síntese química , Produtos Biológicos/química , Catálise , Hidroxilação , Modelos Moleculares , Estrutura Molecular , Oxindóis , EstereoisomerismoRESUMO
Organocatalytic asymmetric conjugate addition of α-nitroketones to ß,γ-unsaturated α-keto esters has been developed. A pyrrolidine-based thiourea-tertiary amine was identified as the best catalyst. The reaction was found to proceed via cascade conjugate addition and acyl transfer reaction. A number of α-nitroketones and ß,γ-unsaturated α-keto esters were examined in this transformation. 5-Nitro-2-acyloxypent-2-enoates were obtained in good yields (up to 99%) and enantioselectivities (up to 99% ee). The products could be hydrolyzed to provide 5-nitro-2-oxopentanoates, which are not available from the direct addition of nitromethane to ß,γ-unsaturated α-keto esters.