Diastereo‐ and Enantioselective Reductive Mannich‐type Reaction of
<i>α</i>
,
<i>β</i>
‐Unsaturated Carboxylic Acids to Ketimines: A Direct Entry to Unprotected
<i>β</i>
<sup>2,3,3</sup>
‐Amino Acids
Copper-catalyzed reductive Mannich-type reaction of unprotected α,β-unsaturated carboxylic acids has been developed. This process allows directaccess to β2,3,3-amino acids with vicinal stereogenic centers, which cannot be formed in analogous catalytic reactions. The silyl-protected carboxylic acid generated from acrylic acid and a hydrosilane indicates a good affinity with CuH catalysis than other