Enantioselective synthesis of α-aryl α-hydrazino phosphonates.

Catalysts generated by the combination of pyridine-hydrazone ,-ligands and Pd(TFA) have been applied to the addition of arylboronic acids to formylphosphonate-derived hydrazones, yielding α-aryl α-hydrazino phosphonates in excellent enantioselectivities (96 → 99% ee). Subsequent removal of the benzyloxycarbonyl (Cbz) -protecting group afforded key building blocks en route to appealing artificial peptides, herbicides and antitumoral derivatives. Experimental and computational data support a stereochemical model based on aryl-palladium intermediates in which the phosphono hydrazone coordinates in its -configuration, maximizing the interactions between the substrate and the pyridine-hydrazone ligand.