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Spin polarization of an Fe/MgO(100) surface oxidized at room temperature has been analyzed with a spin-polarized metastable helium beam, which is an extremely surface sensitive spin probe, under high magnetic fields (0–50 kOe). The spin polarization of the Fe surface, although it initially decays with oxygen exposure, increases at >20 L (1 L=10−6 Torr sec) and becomes comparable to that observed for a clean Fe surface at >100 L. The polarization is negative and especially high at around the Fermi level. This may be understood if we assume the formation of Fe3O4.

A convenient, divergent strategy for the synthesis of a series of modular and fine-tunable C3-TunePhos-type chiral diphosphine ligands and their applications in highly efficient Ru-catalyzed asymmetric hydrogenations were explored. Up to 97 and 99% ee values were achieved for the enantioselective synthesis of beta-methyl chiral amines and alpha-hydroxy acid derivatives, respectively.

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The TunePhos/diamine-Ru(II) complex combined with t-BuOK in 2-propanol effectively catalyzes enantioselective hydrogenation of a wide range of simple ketones including aromatic, heteroaromatic, alpha,beta-unsaturated, and cyclopropyl ketones, affording high reactivity (up to 1,000,000 TON) and excellent enantioselectivities (>99% ee for 13 examples).

A highly efficient strategy for the synthesis of a series of C 3 *-TunePhos chiral diphosphine ligands was well established with several remarkable features. The synthetic utility of these ligands was explored for the ruthenium-catalyzed asymmetric hydrogenation of b-keto esters. Up to 99% ee values were achieved for the enantioselective synthesis of b-hydroxy acid derivatives, which are very important chiral building blocks for the synthesis of a variety of natural products and biologically active molecules.

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Enantiomerically pure 3-arylbutanoic acids and their derivatives such as chiral 3-arylbutanols are important intermediates for the synthesis of aromatic sesquiterpenes of the bisabolane family [1] and useful building blocks in organic synthesis. [2, 3a] A variety of asymmetric syntheses of the carboxylic acids have therefore been developed, such as 1,4-addition of organometallic reagents to chiral a,b-unsaturated esters and amides, [3] diastereoface-differentiating alkylation with a number of nucleophiles and chiral catalysts or promoters, [4] and the Mitsunobu reaction of chiral secondary benzylic alcohols.[5] However, low yields, moderate regioselectivities, and narrow substrate scopes limit the potential applications of these reactions. We envision that one of the most effective methods for the construction of these moieties will be asymmetric hydrogenation of the corresponding prostereogenic 3-aryl-3-butenoic acids. Although significant progress has been made in asymmetric hydrogenation of aarylacrylic acids and other a,b-unsaturated acids with various ruthenium or rhodium complexes, [6] the asymmetric hydrogenation of b,g-unsaturated carboxylic acids still remains a major challenge owing to moderate enantioselectivities (24-85 % ee) and high catalyst loadings (1-2 mol %).[7] Herein we report a Rh-catalyzed highly enantioselective hydrogenation for the preparation of chiral 3-arylbutanoic acids which has several outstanding features: 1) Selectivities of up to 99 % ee and turnover numbers (TONs) of up to 5000 can be achieved.2) The combination of a highly rigid electron-donating Pchiral bisphospholane ligand with optimal solvent and additive effects is the key to efficient transformations.3) The simplicity of obtaining substrates and highly enantioselective hydrogenation under mild conditions make this approach very attractive and practical.A family of prostereogenic unsaturated carboxylic acids was prepared through a simple and versatile synthetic method developed by Itoh et al. [8] using [Pd(PPh 3 ) 4 ] as a catalyst.[7b] As claimed in Itohs report, two advantages make the preparation of substrates especially suitable for large-scale synthesis. First, reactions can be accomplished in one pot by a palladium(0)-catalyzed coupling reaction of diketene with an arylzinc chloride reagent, providing desired 3-aryl-3-butenoic acids in high yields. Second, pure products can be obtained easily by recrystallization or fractional distillation. [8,9] A crucial point to achieving high enantioselectivities and activities for the asymmetric hydrogenation is finding effective catalysts.[10] We initiated our studies on the asymmetric hydrogenation of 3-phenyl-3-butenoic acid by briefly screening several chiral phosphorus ligands (Figure 1). Although the complexes [Rh(S,S,R,R)-TangPhos(cod)]BF 4 (3 a; cod = cyclooctadiene) [11] and [Rh(R,R)-Et-DuPhos(cod)]BF 4 (3 b) [12] were successful for the highly enantioselective hydrogenation of various substituted olefins, only low enantioselectivities were obtained at room temperatur...