Novel Synthesis of Chiral 1,3-Diphosphines via Palladium Template Promoted Hydrophosphination and Functional Group Transformation Reactions

A novel cyano-functionalized monophosphine palladium substrate containing the ortho-metalated (R)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary was synthesized from 3-chloropropionaldehyde diethylacetal via a one-pot process. The asymmetric hydrophosphination reactions between diphenylphosphine and the trans- or cis-monophosphine substrates were carried out under mild conditions, which gave the corresponding cyano-substituted chiral 1,3-bis(diphenylphosphino)propane palladium complexes with good yields and stereoselectivities. Subsequent functional group transformation reactions were conducted by successive treatment of the hydrophosphination products with Dibal-H and chemoselectively yielded the formyl- and hydroxyl-functionalized chiral 1,3-diphosphine complexes. The absolute configurations and coordination information of the novel 1,3-diphosphine complexes were analyzed by X-ray crystallography. The optically pure 1,3-bis(diphenylphosphino)propane ligands with cyano, formyl, and hydroxyl functionalities could be liberated in high yields from the corresponding dihalo palladium complexes by treatment with aqueous potassium cyanide.