Koji Yonehara

Palladium-catalyzed asymmetric intermolecular arylation of cyclic or acyclic alkenes using phosphinite-oxazoline ligands derived from d-glucosamine

Abstract Chiral phosphinite-oxazolines, 2-alkyl- or 2-aryl-4,5-(4,6-O-benzylidene-3-O-(diphenylphosphino)-1,2-di-deoxy-α- d -glucopyranosyl)-[2,1-d]-2-oxazolines 1a–f derived from d -glucosamine hydrochloride, are revealed to work as effective P,N-bidentate ligands in the palladium-catalyzed enantioselective arylation of 2,3-dihydrofuran to give 2-aryl-2,5-dihydrofuran selectively in high yield with up to 96% ee. The first asymmetric phenylation reaction of trans- and cis-crotyl alcohols as acyclic alkenes with iodobenzene is also carried out to afford 3-phenylbutanal in moderate chemical yield with up to 17% ee. The complex [PdCl2(1b)] is newly prepared and its structure is characterized by X-ray crystallography. Structures of the new complex [(p-MeO2CC6H4)PdI(1a)] (8) and its cationic complex [(p-MeO2CC6H4)Pd(1a)]+OTf− (9) are also elucidated on the basis of 1H-, 13C-, and 31P-NMR spectra, p-MeO2CC6H4 moiety on the palladium being located trans to the nitrogen of 1a. This configuration might be responsible for an enantiofacial discrimination of 2,3-dihydrofuran to produce (R) isomer predominantly. The stoichiometric reaction of [PhPd(1f)]+OTf− (11) with 2,3-dihydrofuran has provided the mechanistic aspect for the arylation using P,N-ligands, in which the base-promoted deprotonation at β-position leading to an alkene(2-aryl-2,5-dihydrofuran)–palladium(0) complex has been shown to be an important step for the selective formation of the product.

Efficient Heterogeneous Epoxidation of Alkenes by a Supported Tungsten Oxide Catalyst

The tungsten and zinc oxides supported on SnO2 (W-Zn/SnO2) could act as effective and reusable solid catalysts for selective oxidn. with aq. H2O2. Various kinds of org. substrates such as olefins, amines, silanes, and sulfides could be converted into the corresponding epoxides, N-oxides, silanols, and sulfoxides in high to excellent yields. The present system was applicable to larger-scale epoxidn. of cyclooctene with one equiv. of H2O2 (20 mmol scale) with respect to cyclooctene, and the corresponding epoxide could be isolated in 88% yield. In this case, the turnover no. reached up to 650 and the turnover frequency was 108 h-1, and these values were larger than those of the heterogeneous tungsten catalysts. The obsd. catalysis for the present epoxidn. was truly heterogeneous and the recovered catalyst could be reused several times without an appreciable loss of its high catalytic performance. The kinetic, mechanistic, and spectroscopic studies show that polytungstates with dioxo groups play an important role in the present epoxidn. [on SciFinder(R)]

A Flexible Nonporous Heterogeneous Catalyst for Size‐Selective Oxidation through a Bottom‐Up Approach

The bottom-up approach has the potential to create novel devices with a wide range of applications such as in electronics, medicine, and energy, as the arrangement of molecular building blocks into nanostructures can be controlled. 2] It is still a great challenge to fabricate not only devices but also heterogeneous catalysts with intended structures and functions by a bottom-up approach, while biominerals such as shells and bones have been already formed by the bottom-up approach through the self-assembly of inorganic building blocks with organic molecules in water. The control of the self-organization of nanobuilding blocks with well-defined sizes, shapes, and physical and chemical properties would lead to progress in science and technology. Various catalytically active sites, such as metal nodes, framework nodes, and molecular species, can be introduced into metal–organic frameworks (MOFs) through self-assembly. Efficient sizeand enantioselective catalysis by crystalline and porous MOFs has been reported for reduction, C C bond formation, and acid–base reactions, and hydrolytic and oxidative stabilities are critical for the development of MOF-based oxidation systems that are efficient, chemoand size-selective, and recyclable, and use the green oxidant H2O2. [5–7] Therefore, the development of efficient, easily recoverable, and recyclable heterogeneous oxidation catalysts with H2O2 by a bottom-up approach has received particular research interest. Polyoxometalates (POMs) are discrete early transitionmetal oxide cluster anions with applications in broad fields, such as catalysis, materials, and medicine, because their structures and chemical properties can be finely tuned by choose of the constituent elements. Various POMs such as peroxometalates, lacunary POMs, and transition-metal-substituted POMs have been developed for H2O2or O2-based green oxidations. Therefore, POMs are suitable nanobuilding blocks to construct heterogeneous oxidation catalysts. Recently, the development of heterogeneous oxidation catalysts based on POMs and the related compounds has been attempted according to the following strategies: “solidification” of POMs (formation of insoluble solid ionic materials with appropriate countercations) and “immobilization” of POMs through adsorption, covalent linkage, and ion exchange. In most cases, however, the catalytic activities and selectivities of the parent homogeneous POMs are somewhat or much decreased by the heterogenization, and there are only a few successful examples. We are interested in a bottom-up approach to the design and synthesis of artificial heterogeneous catalysts with POMs and herein report that the nonporous tetra-n-butylammonium salt of [g-SiW10O34(H2O)2] 4 ([(n-C4H9)4N]4[g-SiW10O34(H2O)2]·H2O, 1·H2O) synthesized through a bottom-up approach sorbs ethyl acetate (EtOAc), which is highly mobile in the solid bulk of the compound, probably contributing to the easy co-sorption of the olefins and H2O2. The compound heterogeneously catalyzes size-selective oxidation of various organic substances including olefins, sulfides, and silanes with aqueous H2O2 in EtOAc. The compound can easily be separated by filtration and reused several times with retention of its high catalytic activity. The catalysis is truly heterogeneous in nature because the filtrate after removal of the solid catalyst is completely inactive. Notably, sizeselective oxidation catalysis is observed: small olefins are much more preferentially epoxidized than large olefins. To the best of our knowledge, this study provides the first example for the heterogeneously catalyzed size-selective liquid-phase oxidation with H2O2 by a POM-based catalyst. Compound 1·H2O was synthesized by a bottom-up approach as described below. The silicodecatungstate [gSiW10O34(H2O)2] 4 was synthesized in situ by the addition of concentrated HNO3 to an aqueous solution of [g-SiW10O36] 8 . Then, tetra-n-butylammonium bromide [(n-C4H9)4N]·Br was added to the solution, and white powder of 1·H2O was formed. The use of other cations, such as tetramethylammonium [(CH3)4N] , formed single crystals. The powder Xray diffraction (XRD) pattern, crystal structure, and spacefilling model of 1·H2O are shown in Figure 1a–c. The [*] Prof. Dr. N. Mizuno, Dr. S. Uchida, Dr. K. Kamata, R. Ishimoto, S. Nojima Department of Applied Chemistry, School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

A new sealed lithium-peroxide battery with a co-doped Li2O cathode in a superconcentrated lithium bis(fluorosulfonyl)amide electrolyte.

We propose a new sealed battery operating on a redox reaction between an oxide (O2−) and a peroxide (O22−) with its theoretical specific energy of 2570 Wh kg−1 (897 mAh g−1, 2.87 V) and demonstrate that a Co-doped Li2O cathode exhibits a reversible capacity over 190 mAh g−1, a high rate capability, and a good cyclability with a superconcentrated lithium bis(fluorosulfonyl)amide electrolyte in acetonitrile. The reversible capacity is largely dominated by the O2−/O22− redox reaction between oxide and peroxide with some contribution of the Co2+/Co3+ redox reaction.

Asymmetric hydrogenation of enamides in aqueous media with a new water-soluble chiral rhodium-α,α-trehalose-derived phosphine–phosphinite catalyst

Abstract A new chiral rhodium catalyst with α,α-trehalose-derived phosphine–phosphinite (α,α-TREHAPPN) ligand, [(TREHAPPN)Rh(cod)]BF4 8 has been prepared. This catalyst is soluble in water and is an effective chiral catalyst for asymmetric hydrogenation of N-acyldehydroamino acids in aqueous media to give enantiomerically enriched α-amino acid derivatives with R configuration. The simple decantation allows retrieval of the catalyst from the reaction mixture, the recovered catalyst being re-used without marked loss of enantioselectivity.

Palladium-catalysed asymmetric allylic alkylation using new chiral phosphinite–nitrogen ligands derived from D-glucosamine

Novel phosphinite–nitrogen chiral ligands synthesized from D-glucosamine furnish a high level of enantiomeric excess (up to 96% ee) in palladium-catalysed allylic alkylation.

Synthesis of novel chiral phosphines from α,α-trehalose

Abstract New disaccharide chiral phosphines, such as 4,6- O -benzylidene-2-(diphenylphosphino)-2-deoxy-α- d -altropyranosyl-(1,1)-4,6- O -benzylidene-2-(diphenylphosphino)-2-deoxy-α- d -altropyranoside 1 and 2-(diphenylphosphino)-2-deoxy-4,6- O -isopropylidene-α- d -altropyranosyl-(1,1)-2-(diphenylphosphino)-2-deoxy-4,6- O -isopropylidene-α- d -altropyranoside 9 , were prepared from α,α-trehalose. We also succeeded in the synthesis of polyhydroxy chiral diphosphine 2-(diphenylphosphino)-2-deoxy-α- d -altropyranosyl-(1,1)-2-(diphenylphosphino)-2-deoxy-α- d -altropyranoside 5 by deprotection of isopropylidene groups.

Palladium-Catalyzed Aerobic Intermolecular Cyclization of Acrylic Acid with 1-Octene to Afford α-Methylene-γ-butyrolactones: The Remarkable Effect of Continuous Water Removal from the Reaction Mixture and Analysis of the Reaction by Kinetic, ESI-MS, and XAFS Measurements

Further study of our aerobic intermolecular cyclization of acrylic acid with 1-octene to afford α-methylene-γ-butyrolactones, catalyzed by the Pd(OCOCF(3))(2)/Cu(OAc)(2)⋅H(2)O system, has clarified that the accumulation of water generated from oxygen during the reaction causes deactivation of the Cu cocatalyst. This prevents regeneration of the active Pd catalyst and, thus, has a harmful influence on the progress of the cyclization. As a result, both the substrate conversion and product yield are efficiently improved by continuous removal of water from the reaction mixture. Detailed analysis of the kinetic and spectroscopic measurements performed under the condition of continuous water removal demonstrates that the cyclization proceeds in four steps: 1) equilibrium coordination of 1-octene to the Pd acrylate species, 2) Markovnikov-type acryloxy palladation of 1-octene (1,2-addition), 3) intramolecular carbopalladation, and 4) β-hydride elimination. Byproduct 2-acryloxy-1-octene is formed by β-hydride elimination after step 2). These cyclization steps fit the Michaelis-Menten equation well and β-hydride elimination is considered to be a rate-limiting step in the formation of the products. Spectroscopic data agree sufficiently with the existence of the intermediates bearing acrylate (Pd-O bond), η(3)-C(8)H(15) (Pd-C bond), or C(11)H(19)O(2) (Pd-C bond) moieties on the Pd center as the resting-state compounds. Furthermore, not only Cu(II), but also Cu(I), species are observed during the reaction time of 2-8 h when the reaction proceeds efficiently. This result suggests that the Cu(II) species is partially reduced to the Cu(I) species when the active Pd catalytic species are regenerated.