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Essentially complete atropdiastereoselectivity was realized in the preparation of biaryl diphosphine dioxide by asymmetric intramolecular Ullmann coupling and oxidative coupling with central-toaxial chirality transfer. A bridged C2-symmetric biphenyl phosphine ligand possessing additional chiral centers on the linking unit of the biphenyl groups was synthesized. No resolution step was required for the preparation of the enantiomerically pure chiral ligand. These findings offer a general and practical tool for the development of previously uninvestigated atropdiastereomeric biaryl phosphine ligands. The diphosphine ligand was found to be highly effective in the asymmetric hydrogenation of ␣-and ␤-ketoesters, 2-(6-methoxy-2-naphthyl)propenoic acid, ␤-(acylamino)acrylates, and enol acetates.A xially chiral biaryls are not only common structural motifs in many natural products, but they are also the core of many highly effective chiral ligands for asymmetric reactions. Atropisomeric, C 2 -symmetric diphosphine ligands have played a particularly crucial role in the development of asymmetric catalysis (1-4). Therefore, it is not surprising that considerable efforts have been taken for the design and synthesis of atropisomeric ligands based on the biphenyl, binaphthyl, or other biaryl backbones (5-15). Enantiomerically pure biaryls can be obtained by aryl-aryl coupling followed by a classical resolution of the resulting atropisomers. The disadvantage of the path by resolution is that the maximum yield of the desired atropisomer is only 50% and the enantiomeric excesses (ee's) are usually Ͻ100%, not to mention that resolution procedures are frequently tedious. From a practical standpoint, it is desirable to develop efficient atroposelective methodologies for the synthesis of biaryls ligands to expand the scope of the useful catalysts. Various approaches, including desymmetrization of prochiral biaryls (16), kinetic resolution of racemic substrates (17), asymmetric catalytic coupling (18-23), and chirality transfer from central, axial, and planar asymmetry have been reported (24-38). Oxazolinemediated asymmetric Ullmann coupling was studied by Meyers and coworkers (28-30) to produce diastereomerically pure bis(oxazoline)s and corresponding enantiomerically pure biphenols and binaphthols. Previously, most of the research was focused on the syntheses of biphenols and binaphthols; in contrast, less attention was paid to the atroposelective syntheses of biaryl diphosphine oxides, the precursors of widely used diphosphine ligands. Recently, we successfully developed two diastereomeric diphosphine ligands for use in asymmetric hydrogenation reactions by stereoselective intermolecular Ullmann coupling of two chiral phosphine oxide precursors with moderate atropdiastereoselectivity (39). However, very careful separation of the diastereomers by column chromatography on silica gel was still needed. Herein, we report an example of essentially complete atropdiastereoselectivity in the synthesis of diphosphine dioxide by means of int...

[structure: see text] Diastereomeric biaryl diphosphine ligands 10 and 11 with added chiral centers on the backbone were synthesized. Substrate-directed asymmetric synthesis occurred in the coupling step of the preparation of the diastereomeric diphosphine oxides. The diastereomeric diphosphine oxides were easily separated by column chromatography with silica gel. Ruthenium catalysts containing these ligands were highly effective in the hydrogenation of 2-(6'-methoxy-2'-naphthyl)propenoic acid and beta-ketoesters. The additional chiral centers had a significant influence on the enantioselectivity and activity of the catalysts.

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Li-rich layered oxides (LLOs) are considered as the cathode materials for the next generation of lithium-ion batteries because of their high specific capacity. However, due to the structural rearrangement in the charging and discharging process, the initial Coulombic efficiency (ICE) is low and accompanied by serious voltage attenuation and bad cycle performance. In this work, the Li-gradient layer on the surface of the rod-like LLOs is constructed by the treatment of (NH 4 ) 2 SiF 6 under high temperature and subsequent washing. XRD, HRTEM, and Raman spectra verify the existence of the spinel phase of Li 1−x Mn 2 O 4 on the surface of LLOs by the modification. The results of electrochemical measurements show that the modified LLOs exhibit a higher ICE of 87% with an excellent cycling retention of 90.4% (after 100 cycles at 1 C). These improvements on the electrochemical performance are caused by the high Li + diffusion and improved the redox reversibility of oxygen ions on the LLOs with the unique structure of the Ligradient and spinel coating layer on the surface.

A rhodium diphosphine catalyst containing electron-withdrawing substituents on the ligand is highly regioselective in the hydroformylation of vinylarenes giving high branched/linear product ratios.

Three of the structures in Chart 1 were mislabeled in the text: structure 2 is saframycin S, structure 3 is naphthyridinomycin, and structure 4 is anthramycin.