Palladium Template Promoted Asymmetric Synthesis of 1,2-Diphosphines by Hydrophosphination of Functionalized Allenes

Organopalladium complexes containing ortho-metalated (R)-(1-(dimethylamino)ethyl)naphthalene and (R)-[1-(1-(dimethylamino)-2,2-dimethylpropyl]-2,5-dimethylbenzene as the chiral auxiliaries were used to promote the asymmetric hydrophosphination reactions between diphenylphosphine and ester- and keto-functionalized allenes in high regio- and stereoselectivites under mild conditions. The hydrophosphination reactions generated the 1,2-diphosphine ligands with chirality residing on the carbon backbone as bidentate chelates on the chiral organopalladium templates. The major isomers were isolated in appreciable yields in configurationally pure forms and characterized by means of single-crystal X-ray crystallography. The chiral auxiliaries could be removed chemoseletively by treatment with concentrated hydrochloric acid to form the corresponding optically pure neutral dichloro complexes. Subsequently, the dichloro complexes underwent ligand displacement with aqueous cyanide to generate their corresponding optically pure diphosphine ligands in high yields.