A bifunctional squaramide catalyzed the enantioselective Michael addition of pyrazol-3- ones to ortho-quinone methides, generated in situ from 2-(1-tosylalkyl)phenols is presented. The corresponding chiral pyrazolones are obtained with good to excellent yields (27-98%) and enantiomeric excess (14-99% ee).
Keywords: Asymmetric catalysis, organocatalysis, ortho-quinone methides, pyrazolones, Michael reaction.