Alternative synthesis of α-substituted β-amidophosphines by [1,4]-addition. A new route to chiral ligands

Phosphine–borane can be diastereoselectively added to chiral α,β-unsaturated amides 3, using amino-alcohols as chiral inducers, leading to α-substituted β-amidophosphine boranes 4 with up to 74% diastereomeric excess. Selective deprotection afforded optically pure carboxylic derivatives 5 which are key intermediates for the synthesis of various potential chiral ligands for asymmetric catalysis.