Forming All‐Carbon Quaternary Stereocenters by Organocatalytic Aminomethylation: Concise Access to β 2,2 ‐Amino Acids

The asymmetric synthesis of β 2,2 ‐amino acids remains a formidable challenge in organic synthesis. Here a novel organocatalytic enantioselective aminomethylation of ketenes with stable and readily available N,O‐acetals is reported, providing β 2,2 ‐amino esters bearing an all‐carbon quaternary stereogenic center in high enantiomeric ratios with a catalytic amount of chiral phosphoric acid. Typically, this transformation probably proceeds through an asymmetric counter‐anion‐directed catalysis. As a result, a concise, practical, and atom‐economic protocol toward rapidly access to β 2,2 ‐amino acids has been developed.