Catalytic Enantioselective Addition of Pyrazol‐5‐ones to Trisubstituted Nitroalkenes with an N‐Sulfinylurea Organocatalyst.

The first example of enantioselective nitronate protonation following Michael addition of a carbon nucleophile to an α,β,β-trisubstituted nitroalkene is reported. An N-sulfinylurea catalyst was employed to catalyze the addition of a variety of 3-substituted pyrazol-5-one nucleophiles to trisubstituted nitroalkenes incorporating an oxetane or azetidine ring at the β-position. The nitroalkane-pyrazolone adducts were obtained with good yield and enantioselectivity. Furthermore, the Michael addition products can be reduced to the corresponding enantioenriched amines with minimal loss of enantiomeric purity.