Pd-catalyzed enantioselective synthesis of quaternary α-amino acid derivatives using a phenylalanine-derived P-chirogenic diaminophosphine oxide
摘要:
A Pd-catalyzed enantio selective synthesis of quaternary alpha-amino acid derivatives using a phenylalanine-derived P-chirogenic diaminophosphine oxide is described. Asymmetric allylic substitution using acyclic beta-keto esters with a nitrogen functional group at the alpha-carbon as prochiral nucleophiles proceeded in the presence of 5 mol % of Pd catalyst, 10 mol % of chiral diaminophosphine oxide 1j, BSA, and appropriate additives, affording the corresponding quaternary alpha-amino acid derivatives in excellent yield and in up to 92% ee. (c) 2007 Elsevier Ltd. All rights reserved.
Development of a New Class of Chiral Phosphorus Ligands: P-Chirogenic Diaminophosphine Oxides. A Unique Source of Enantioselection in Pd-Catalyzed Asymmetric Construction of Quaternary Carbons
phosphorus compounds have been successfully applied to Pd-catalyzed asymmetric construction of tertiary and quaternary carbons. The actual ligand structure was the trivalent phosphorus species 17, which was generated in situ by BSA-induced P(V) to P(III) transformation of 6, the preligand. Detailed mechanistic studies, including asymmetric amplification and initial rate kinetics, revealed that complex 18