Synthesis of alpha-substituted beta-amidophosphines by diastereoselective alkylation. A new access to chiral ligands for asymmetric catalysis.

Abstract

Chiral beta-amidophosphine boranes 7a-f can be diastereoselectively alkylated, using O-protected amino-alcohols as chiral inducers, to furnish alpha-substituted beta-amidophosphine boranes 8a-f and 9-12 with up to 72% diastereoisomeric excess. Selective deprotection afforded optically pure carboxylic derivative 13 which is a key intermediate for the synthesis of various potential chiral ligands for asymmetric catalysis.