- 2,5-Dimethyl-3,4-bis[(2R,5R)-2,5-dimethylphospholano]thiophene: First member of the hetero-DuPHOS family
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The 2,5-dimethyl-3,4-bis[(2R,5R)-2,5-dimethylphospholano]thiophene (UlluPHOS), a new thiophene-based analogue of (R,R)-1,2-bis(phospholano)benzene (Me-DuPHOS), was synthesized, geometrically and electronically characterized, and employed as ligand of Rh and Ru in some standard hydrogenation reactions of prostereogenic functionalized carbon-carbon and carbon-oxygen double bonds. The synthesis of UlluPHOS is much easier than that provided for Me-DuPHOS. UlluPHOS and Me-DuPHOS display very similar geometries, while the electronic availability of the former is higher than that exhibited by the latter. The Rh and Ru complexes of UlluPHOS produced excellent enantiomeric excesses (98.9-99.5%) in the hydrogenation of N-acetyl-α-enamino acids and reaction rates higher than those found when employing the analogous complexes of Me-DuPHOS.
- Benincori, Tiziana,Pilati, Tullio,Rizzo, Simona,Sannicolo, Franco,Burk, Mark J.,De Ferra, Lorenzo,Ullucci, Elio,Piccolo, Oreste
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- General and selective copper-catalyzed reduction of tertiary and secondary phosphine oxides: Convenient synthesis of phosphines
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Novel catalytic reductions of tertiary and secondary phosphine oxides to phosphines have been developed. Using tetramethyldisiloxane (TMDS) as a mild reducing agent in the presence of copper complexes, PO bonds are selectively reduced in the presence of other reducible functional groups (FGs) such as ketones, esters, and olefins. Based on this transformation, an efficient one pot reduction/phosphination domino sequence allows for the synthesis of a variety of functionalized aromatic and aliphatic phosphines in good yields.
- Li, Yuehui,Das, Shoubhik,Zhou, Shaolin,Junge, Kathrin,Beller, Matthias
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p. 9727 - 9732
(2012/07/14)
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- Highly chemoselective metal-free reduction of phosphine oxides to phosphines
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Unprecedented chemoselective reductions of phosphine oxides to phosphines proceed smoothly in the presence of catalytic amounts of specific Br?nsted acids. By utilizing inexpensive silanes, e.g., PMHS or (EtO)2MeSiH, other reducible functional groups such as ketones, aldehydes, olefins, nitriles, and esters are well-tolerated under optimized conditions.
- Li, Yuehui,Lu, Liang-Qiu,Das, Shoubhik,Pisiewicz, Sabine,Junge, Kathrin,Beller, Matthias
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p. 18325 - 18329
(2013/01/15)
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- Method for Producing Polyhydroxyalkanoates
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The invention relates to a process for preparing polyhydroxyalkanoates by polymerization of lactones of the general formula I, where the substituents and the index n have the meanings given in the description, in the presence of at least one catalyst of the formula (II) LIMaXam, where the substituents and indices have the meanings given in the description. The invention further relates to poly-3-hydroxybutyrates which have a novel property profile and are obtainable for the first time by means of this process, and also biodegradable polyester mixtures based on these poly-3-hydroxybutyrates.
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- Probing the importance of the hemilabile site of bis(phosphine) monoxide ligands in the copper-catalyzed addition of diethylzinc to N-phosphinoylimines: Discovery of new effective chiral ligands
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(Chemical Equation Presented) The hemilabile ligand Me-DuPHOS(O) 2 has proven to be a successful ligand for the copper-catalyzed addition of diethylzinc to N-phosphinoylimines. The corresponding α-chiral amines were obtained in high yields (80-98%) and enantiomeric ratios (19.0:1 to 99.0:1 er). Furthermore, this Cu?2 catalytic system has been shown to be effective in the addition of diethylzinc to nitroalkenes and in the reduction of β,β-disubstituted vinyl phenyl sulfones. This paper describes a general structure/selectivity study in which the three ligand subunits (chiral phospholane-linker-labile coordinating group (Z)) are systematically modified and tested in the copper-catalyzed addition of diethylzinc to the N-phosphinoylimine 1 derived from benzaldehyde. This study led to the discovery of a new class of effective chiral ligands that combine a chiral phospholane unit and an achiral phosphine oxide.
- Bonnaventure, Isabelle,Charette, Andre B.
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p. 6330 - 6340
(2008/12/22)
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- Preparation and use of C2-symmetric bis(phospholanes): Production of α-amino acid derivatives via highly enantioselective hydrogenation reactions
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A new class of chiral C2-symmetric bis(phospholane) ligands has been prepared and used in rhodium-catalyzed asymmetric hydrogenation reactions. We describe a practical, one-pot procedure which utilizes enantiomerically pure 1,4-diol cyclic sulf
- Burk, Mark J.,Feaster, John E.,Nugent, William A.,Harlow, Richard L.
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p. 10125 - 10138
(2007/10/02)
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