Squaramide-catalyzed asymmetric Michael/cyclization of 4-isothiocyanato pyrazolones and α,β-unsaturated ketones.

[Display omitted] • Highly enantioselectivities synthesis of spiropyrazolones. • Spiro[pyrazolone-pyrrolidinethiones] were synthetized under mild conditions. • The asymmetric Michael addition of 4-isothiocyanato pyrazolones with ethyl β -benzoylacrylates. The cascade Michael addition/cyclization reaction of 4-isothiocyanato pyrazolones with ethyl β -benzoylacrylates has been explored by asymmetric organocatalysis, delivering spiro[pyrazolone-pyrrolidinethione] cores bearing three contiguous stereogenic centers in excellent enantioselectivities (up to 95% ee) with excellent yields (up to 91%). This process exhibited broad substrate scope and the advantages of simple operation. A plausible mechanism for this reaction was proposed. [ABSTRACT FROM AUTHOR]