Highly selective: The title reaction is achieved with high enantiomeric and geometric control and thermodynamically unstable (Z)‐enone derivatives are obtained as the major products (see scheme). The procedure tolerates a wide range of substrates to generate optically active pyrazolones with vinyl‐substituted quaternary stereocenters.
Asymmetric α-Amination of 4-Substituted Pyrazolones Catalyzed by a Chiral Gd(OTf)<sub>3</sub>/<i>N,N′</i>-Dioxide Complex: Highly Enantioselective Synthesis of 4-Amino-5-pyrazolone Derivatives
The asymmetric α-amination of 4-substituted pyrazolones with azodicarboxylates was investigated for the first time, employing an N,N′-dioxide gadolinium(III) complex as the catalyst. The novel transformations exhibited high yield, and 4-amino-5-pyrazolone derivatives bearing a chiral quaternary center were obtained in excellent yields (up to 99%) and enantioselectivities (90%−97% ee) for a broad scope