Component-Selective and Stereocontrolled One-Step Three-Component Reaction among Aldehydes, Amines, and Allenyl Boronic Acids or Allenyl Pinacolboronates

A one-step, three-component condensation of allenyl boronic acids or allenyl pinacolboronates with amines and aldehydes affords alpha-allenyl or alpha-propargyl alpha-amino acids and anti-beta-amino alcohols. This process gives the allenyl or propargyl product depending on the amine and boron components. Secondary amines generate exclusively alpha-allenyl alpha-amino acids, while primary aliphatic amines lead to alpha-propargyl alpha-amino acids. Secondary aliphatic amines react with chiral alpha-hydroxy aldehydes and allenyl boron derivatives to form stereoselectively allenyl anti-beta-amino alcohol products.