A new preparation of homochiral N-protected 5-hydroxy-3-piperidenes, promising chiral building blocks, by palladium-catalyzed deracemization of their alkyl carbonates

The palladium-catalyzed deracemization of N-protected alkyl carbonates of 5-hydroxy-3-piperidenes by use of chiral phosphine ligands is described. A Trost ligand such as (R)-BPA was found to be a suitable chiral ligand for the deracemization, providing N-protected 5-hydroxy-3-piperidenes in good yields with good to high enantioselectivities. A plausible mechanism for the reaction is proposed.