Asymmetric Michael/Aromatization Reaction of Azlactones to α,β‐Unsaturated Pyrazolones with C‐4 Regioselectivity Catalyzed by an Isosteviol‐Derived Thiourea Organocatalyst

Abstract

AbstractPyrazoles are an important class of molecular structures with significant biological and pharmaceutical activities. Herein, heterocyclic compounds containing both a pyrazole motif and a masked amino acid structure are synthesized through the asymmetric Michael/aromatization of azlactones to α,β‐unsaturated pyrazolones by using isosteviol‐derived amine thiourea as the organocatalyst. The products are obtained in good yields (up to 93 %) with good diastereoselectivities and good enantioselectivities (up to >10:1 dr, 97 % ee).