Squaramide-catalyzed asymmetric Michael/cyclization of 4-isothiocyanato pyrazolones and a,/3-unsaturated ketones

The cascade Michael addition/cyclization reaction of 4-isothiocyanato pyrazolones with ethyl /3-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. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The cascade Michael addition/cyclization reaction of 4-isothiocyanato pyrazolones with ethyl /3-benzoylacrylates was explored using asymmetric organocatalysis, resulting in spiro[pyrazolone-pyrrolidinethione] cores with three contiguous stereogenic centers in excellent enantioselectivities (up to 95% ee) and yields (up to 91%). This process showed a broad substrate scope and the advantage of simple operation.