- Development of effective bidentate diphosphine ligands of ruthenium catalysts toward practical hydrogenation of carboxylic acids
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Hydrogenation of carboxylic acids (CAs) to alcohols represents one of the most ideal reduction methods for utilizing abundant CAs as alternative carbon and energy sources. However, systematic studies on the effects of metal-to-ligand relationships on the catalytic activity of metal complex catalysts are scarce. We previously demonstrated a rational methodology for CA hydrogenation, in which CA-derived cationic metal carboxylate [(PP)M(OCOR)]+ (M = Ru and Re; P = one P coordination) served as the catalyst prototype for CA self-induced CA hydrogenation. Herein, we report systematic trial- and-error studies on how we could achieve higher catalytic activity by modifying the structure of bidentate diphosphine (PP) ligands of molecular Ru catalysts. Carbon chains connecting two P atoms as well as Ar groups substituted on the P atoms of PP ligands were intensively varied, and the induction of active Ru catalysts from precatalyst Ru(acac)3 was surveyed extensively. As a result, the activity and durability of the (PP)Ru catalyst substantially increased compared to those of other molecular Ru catalyst systems, including our original Ru catalysts. The results validate our approach for improving the catalyst performance, which would benefit further advancement of CA self-induced CA hydrogenation.
- Saito, Susumu,Wen, Ke,Yoshioka, Shota
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supporting information
p. 1510 - 1524
(2021/06/18)
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- Induction of chirality in 4,4′-azopyridine by halogen-bonding interaction with optically active ditopic donors
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Optically active ditopic halogen bond donors bearing two 4-iodotetrafluorophenyl groups were obtained by reaction of chiral diols with iodopentafluorobenzene. Co-crystallization of these donors with anti-4,4′-azopyridine afforded binary complexes containing infinite chains of the alternating component molecules connected by halogen bonds. The solid state CD measurements confirmed that complexation induces optical activity of the azo chromophore due to the twisting of the aryl-N═N system or external chiral perturbation exerted by host molecules.
- Alfuth, Jan,Chojnacki, Jaros?aw,Po?oński, Tadeusz,Olszewska, Teresa
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supporting information
p. 5512 - 5517
(2019/04/04)
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- [6+5] FUSED BICYCLES AS A THROMBIN ANTAGONIST, PROCESS FOR PREPARATION THEREOF AND PHARMACEUTICAL COMPOSITIONS CONTAINING THE BICYCLES
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The present invention relates to the new [6+5] fused bicycle derivatives, pharmaceutically acceptable salts or isomers thereof, processes for preparing the same, and pharmaceutical compositions comprising the same. The [6+5] fused bicycle derivatives can antagonize the thrombin receptor and thus may be effectively used for the treatment and prevention of thrombus, platelet aggregation, atherosclerosis, restenosis, blood coagulation, hypertension, arrhythmia, angina pectoris, heart failure, inflammation and cancer when used alone or with other cardiovascular agents.
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Page/Page column 64
(2012/01/14)
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- Electron-donating and rigid p-stereogenic bisphospholane ligands for highly enantioselective rhodium-catalyzed asymmetric hydrogenations
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More electron donating, more rigid: A new highly electron-donating P-stereogenic bisphospholane ligand (ZhangPhos) was synthesized in a practical and highly enantioselective manner from a commercially available chiral source. Better or comparable enantioselectivities and reactivities than TangPhos were achieved in rhodium-catalyzed hydrogenation of various functionalized olefins (see scheme; nbd=3,5-norbornadiene). Copyright
- Zhang, Xiaowei,Huang, Kexuan,Hou, Guohua,Cao, Bonan,Zhang, Xumu
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supporting information; experimental part
p. 6421 - 6424
(2010/12/19)
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- Design and synthesis of a novel three-hindered quadrant bisphosphine ligand and its application in asymmetric hydrogenation
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A novel three hindered quadrant bisphosphine ligand has been synthesized. The ligand shows excellent enantioselectivities and reactivities for rhodium-catalyzed hydrogenations of various functionalized olefins.
- Huang, Kexuan,Zhang, Xiaowei,Emge, Thomas J.,Hou, Guohua,Cao, Bonan,Zhang, Xumu
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supporting information; experimental part
p. 8555 - 8557
(2011/01/03)
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- Asymmetric Ring-Closing Metathesis Catalyzed by Chiral Molybdenum Alkylidene Complexes
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Kinetic resolution was observed in ring-closing metathesis of racemic dienes catalyzed by the newly developed chiral molybdenum alkylidene complexes (R,R)-Mo(CHCMe2Ph)(NAr)(TBEC) 1 (Ar = 2,6-i-Pr2C6H3, TBEC = 2′,2′ ,2″,2″-tetrakis(trifluoromethyl)-1,2-bis(2′-hydroxyethyl) cyclopentane) and (R,R)-Mo(CHCMe2Ph)(NAr)(TBEH) 2 (Ar - 2,6-i-Pr2C6H3, TBEH = 2′,2′,2″,2″-tetrakis(trifluoro- methyl)-1,2-bis(2′-hydroxyethyl)cyclohexane). In the case of a prochiral symmetric triene substrate, optically active cyclized product was formed by catalytic ring-closing metathesis with 1, which opens the possibility of a new version of two-directional synthesis. Although the observed enantiomeric excesses were modest to low, this data demonstrates the feasibility of asymmetric induction by chiral alkylidene catalysts in ring-closing metathesis.
- Fujimura, Osamu,Grubbs, Robert H.
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p. 824 - 832
(2007/10/03)
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- Synthesis of new C2-symmetrical diphosphines using chiral zinc organometallics
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The new C2-symmetrical diphosphines 1-4 of potential interest for asymmetric catalysis were prepared in protected form by a convergent synthesis based on the use of readily available (S,S)-1,2-cyclohexanedicarboxylic acid 8 and the phosphorus reagent (Et2N)2PLi·BH3.
- Longeau, Alexia,Durand, Sandrine,Spiegel, Anja,Knoechel, Paul
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p. 987 - 990
(2007/10/03)
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- Total syntheses of (-)-papuamine and (-)-haliclonadiamine
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The pentacyclic marine alkaloids (-)-papuamine (1) and (-)-haliclonadiamine (2) have been prepared by total synthesis. The synthesis began with (-)-8, which was converted into diester 20 by way of bis-mesylate 17, dinitrile 18, and diacid 19. Dieckmann cyclization of 20 provided keto ester 21, which was transformed into acetal 22. After hydrolysis of the acetal, ketone 25 was subjected to reductive amination with 1,3-propanediamine and sodium triacetoxyborohydride to obtain diamines 26 and 27 as a 71:29 mixture of diastereomers, favoring the symmetrical isomer having the papuamine relative configuration. After transformation of the diamines to their t-Boc derivatives, the benzyl ethers were cleaved and the resulting diol was oxidized to dialdehyde 30. Application of the Seyferth procedure for conversion of aldehydes to alkynes gave a mixture of diynes 31 and 32. After removal of the t-Boc protecting groups from 31, diamino diyne 15 was treated with tributylstannane and azoisobutyronitrile te obtain the bis-vinylstannane 34. Treatment of this compound with Pd(II) and Cu(I) in the presence of air produced (-)-papuamine (1). (-)Haliclonadiamine (2) was obtained from the unsymmetrical isomer, 32. The NMR spectra of the synthetic alkaloids were identical to those of authentic samples of the natural alkaloids.
- McDermott, Todd S.,Mortlock, Andrew A.,Heathcock, Clayon H.
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p. 700 - 709
(2007/10/03)
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- Enzymes in Organic Synthesis. 24. Preparations of Enantiomerically Pure Chiral Lactones via Stereospecific Horse Liver Alcohol Dehydrogenase Catalyzed Oxidations of Monocyclic Meso Diols
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Preparative-scale horse liver alcohol dehydrogenase catalyzed oxidation of monocyclic meso diols provides a direct and convenient one-step route to a broad range of chiral γ-lactones of value as synthons in asymmetric synthesis.The general applicability of the method is demonstrated by oxidations of cis-1,2-bis(hydroxymethyl) substrates of the cyclohexyl, cyclohexenyl, cyclopentyl, cyclobutyl, cyclopropyl, and dimethylcyclopropyl series.For each diol, oxidation of the hydroxymethyl group attached to the S chiral center occurs exclusively, and the pure γ-lactone products are isolated in high (68-90percent) yields and of 100percent ee.In contrast, the enzyme does not exhibit significant enantiomeric selectivity in its catalysis of oxidations of the corresponding racemic trans diols.The stereospecificities observed, or lack thereof, are as predicted by the active-site model.
- Jakovac, Ignac J.,Goodbrand, H. Bruce,Lok, Kar P.,Jones, J. Bryan
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p. 4659 - 4665
(2007/10/02)
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