An organopalladium complex containing ortho-metalated (S)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary has been used to promote the asymmetric hydrophosphination reactions between diphenylphosphine and (E)- or (Z)-diphenyl-1-propenylphosphine in high regio- and stereoselectivities under mild conditions. Hydrophosphination of (Z)-diphenyl-1-propenylphosphine with diphenylphosphine gave (S)-(-)-prophos as the major product. Using the same chiral metal template, the corresponding hydrophosphination reaction with (E)-diphenyl-1-propenylphosphine gave (R)-(+)-prophos predominantly. The hydrophosphination reactions generated the asymmetric diphosphines as bidentate chelates on the chiral naphthylamine palladium templates. The template products obtained undergo cis-trans isomerization in solution to form an equilibrium mixture of regioisomers. X-ray analysis of the major template products obtained from the hydrophosphination of (Z)-diphenyl-1-propenylphosphine reveals that the two regioisomers are cocrystallized in a 1:1 ratio. The naphthylamine auxiliary could be removed chemoselectively from the template products by treatment with concentrated hydrochloric acid to form the corresponding optically pure neutral complexes [(R)- or (S)-(prophos)PdCl(2)]. Subsequently, the (R)- and (S)-dichloro complexes undergo ligand displacement with aqueous cyanide to generate the corresponding optically pure diphosphine ligands in high yields. Mechanistic pathways explaining the stereoselectivity of the chiral organopalladium template promoted hydrophosphination reactions are also proposed.

An organoplatinum complex containing ortho-metalated (S)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary has been used to promote the asymmetric [4 + 2] Diels-Alder reaction between diphenylvinylphosphine and N-(diphenylphosphino)pyrrole. The reaction was complete in 7 days at room temperature, with the formation of three isomeric chelating diphosphine exo cycloadducts in the ratio 10:3:1. The cycloadducts are thermodynamically unstable and undergo retro-cycloaddition reactions slowly in solution. When the major isomer of the pyrrole cycloadducts was heated with 2-(diphenylphosphino)furan, the respective furan cycloadducts were formed via the retro pyrrole Diels-Alder pathway, followed by an asymmetric furan Diels-Alder reaction. The cyclic diene N-(diphenylphosphino)pyrrole was regenerated from this retro cycloaddition reaction. The undesired retro Diels-Alder reaction could be deterred by hydrogenation of the azanorbornene double bond. The chiral naphthylamine auxiliary could be removed chemoselectively from the metal template by treatment with concentrated hydrochloric acid to generate the corresponding dichloroplatinum(II) complex. The azabicyclic skeleton and the P-N bond remained unchanged in this acid treatment. Further treatment of the dichloro complex with aqueous cyanide liberates the chiral diphosphine cycloadduct, which could be coordinated to the Au-(I) metal ion.

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The asymmetric hydrophosphination reaction of 1,1-bis(diphenylphosphino)ethene and diphenylphosphine promoted by a chiral organopalladium(II) complex derived from (S)-N,N-dimethyl-1-(1-naphthyl)ethylamine proceeded stereoselectively to generate an equilibrium mixture of four diastereomeric triphosphine palladium(II) template products in a ratio of 17:5:3:2. Alternatively, the direct coordination of 1,1,2-tris(diphenylphosphino)ethane to the chiral organopalladium template generated the same equilibrium mixture of diastereomeric products with the same stereoselectivity. Subsequent asymmetric oxidation of the diastereomeric template products with hydrogen peroxide proceeded stereoselectively to generate four diastereomeric monooxidation products in the ratio of 14:3:3:1. The effects of solvent, temperature, and alternative oxidizing agents were also studied. The naphthylamine auxiliary was removed chemoselectively from the template products by treatment with concentrated hydrochloric acid to form an enantiomerically enriched mixture of the corresponding dichloro complexes, which upon subsequent repeated recrystallization gave the predominant enantiomeric complex in its optically pure form. Further ligand displacement of the enantiomerically pure dichloro complex with aqueous cyanide liberated the free mixed phosphine−phosphine oxide ligand in quantitative yield.