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The organopalladium complex containing ortho-metalated ( R )-[1-(dimethylamino) ethyl]naphthalene as the chiral auxiliary has been used as the chiral template to promote the asymmetric hydrophosphination reaction between diphenylphosphine and 2-ethynylpyridine in high selectivity under mild conditions. The double hydrophosphination reaction produces four stereoisomeric products in the ratio of 1:19.4:2.4:1.3. The naphthylamine auxiliary could be removed chemoselectively from the template products by treatment with concentrated hydrochloric acid to form the corresponding chiral dichloro complexes [(P–P)PdCl 2 ]. The molecular structure and absolute configuration of the dichloro complex have been resolved by single-crystal X-ray crystallography. It confirms that the asymmetric diphosphines as P–P bidentate chelate on the chiral naphthylamine palladium templates. Finally, the enantiomerically pure diphosphine ligand with chirality on the carbon backbone can be readily liberated from the dichloro palladium complex as an air-sensitive solid by treatment of the complex with aqueous potassium cyanide in high yield. [ABSTRACT FROM AUTHOR]

Abstract: An organopalladium(II) complex derived from (S)-N,N-dimethyl-1-(1-naphthyl)-ethylamine was employed as the chiral auxiliary to promote the asymmetric hydrophosphination reactions between diphenylphosphine and (E) or (Z)-diphenylphosphinostyrene in high regio- and stereoselectivities at low temperature with triethyl amine as external base. Optically active free ligand (R)-1,2-bis(diphenylphosphino)-1-phenylethane was obtained in high yield subsequently. Mechanistic pathways explaining the stereoselectivity of the chiral organopalladium template promoted hydrophosphination reactions are also proposed. [Copyright &y& Elsevier]