19436-52-3Relevant academic research and scientific papers
Chiral auxiliaries onto conducting polymers
Pellon, Pascal,Deltel, Elisabeth,Pilard, Jean-Fran?ois
, p. 867 - 869 (2001)
The synthesis of new chiral auxiliaries was performed onto conducting polythiophene. The electrochemical behavior of such a matrix was investigated and one of them present a noticeable stability when an adequate spacer is introduced between the redox centre and the chiral unit.
PegPhos: A monodentate phosphoramidite ligand for enantioselective rhodium-catalysed hydrogenation in water
Hoen, Rob,Leleu, Stephane,Botman, Peter N. M.,Appelman, Vanessa A. M.,Feringa, Ben L.,Hiemstra, Henk,Minnaard, Adriaan J.,Van Maarseveen, Jan H.
, p. 613 - 615 (2006)
A BICOL derived monodentate phosphoramidite ligand gives ee's up to 89% in the enantioselective Rh-catalysed hydrogenation of N-acyl dehydroalanine using water as the solvent. The Royal Society of Chemistry.
Optically pure 1,2-bis[(o-alkylphenyl)phenylphosphino]ethanes and their use in rhodium-catalyzed asymmetric hydrogenations of α-(acylamino)acrylic derivatives
Wada, Yoshiyuki,Imamoto, Tsuneo,Tsuruta, Hideyuki,Yamaguchi, Kentaro,Gridnev, Ilya D.
, p. 777 - 788 (2004)
Optically pure (S,S)-1,2-bis[(o-alkylphenyl)-phenylphosphino]ethanes 1a-d were prepared in four steps from phenyldichlorophosphine via phosphine-boranes as the intermediates. The rhodium complexes 5a-d of these diphosphines were used for the asymmetric hydrogenations of α-(acylamino)-acrylic derivatives including β-disubstituted derivatives. Markedly high enantioselectivity (78→99%) was observed for the reduction of β-monosubstituted derivatives. β-Disubstituted derivatives were also reduced in considerably high enantioselectivity (up to 90%). The single crystal X-ray analysis of the rhodium complex 5c of (S,S)-1,2-bis[phenyl(5′,6′,7′,8′- tetrahydronaphthyl)phosphino]ethane (1c) revealed its δ-type structure with face orientation of the two tetrahydronaphthyl groups and edge orientation of the two phenyl groups. This conformation corresponds to that of the rhodium complex of 1,2-bis[(o-methoxyphenyl)phenylphosphino]ethane (DIPAMP); the rhodium complex of (R,R)-DIPAMP, whose chirality at phosphorus is opposite that of 5c, exhibits a λ-type structure with the face orientation of the two o-methoxyphenyl groups and the edge orientation of the two phenyl groups. The conformational similarity of these rhodium complexes as well as the stereochemical outcome in the asymmetric hydrogenations means that the coordinative interaction of the methoxy group of DIPAMP with rhodium metal is not the main factor that affects asymmetric induction.
Artificial metalloenzymes for enantioselective catalysis: The phenomenon of protein accelerated catalysis
Collot, Jér?me,Humbert, Nicolas,Skander, Myriem,Klein, Gérard,Ward, Thomas R.
, p. 4868 - 4871 (2004)
We report on the phenomenon of protein-accelerated catalysis in the field of artificial metalloenzymes based on the non-covalent incorporation of biotinylated rhodium-diphosphine complexes in (strept)avidin as host proteins. By incrementally varying the [Rh(COD)(Biot-1)]+ vs. (strept)avidin ratio, we show that the enantiomeric excess of the produced acetamidoalanine decreases slowly. This suggests that the catalyst inside (strept)avidin is more active than the catalyst outside the host protein. Both avidin and streptavidin display protein-accelerated catalysis as the protein embedded catalyst display 12.0- and 3.0-fold acceleration over the background reaction with a catalyst devoid of protein. Thus, these artificial metalloenzymes display an increase both in activity and in selectivity for the reduction of acetamidoacrylic acid.
A new family of chelating diphosphines with a transition metal stereocenter in the backbone: Novel applications of "chiral-at-rhenium" complexes in rhodium-catalyzed enantioselective alkene hydrogenations
Kromm, Klemenz,Zwick, Bill D.,Meyer, Oliver,Hampel, Frank,Gladysz, John A.
, p. 2015 - 2027 (2001)
The title compounds are accessed by sequences starting with racemic and enantiomerically pure [(η5-C5H5)Re(NO)(PPh3) (CH3)]. Reactions with chlorobenzene/HBF4, PPh2H, and tBuOK give the phosphido complex [(η5-C5H5)Re(NO) (PPh3)(PPh2)] (3). Reactions with Ph3C+BF4-,PPh2H, and tBuOK give the methylene homologue [(η5-C5H5)Re(NO)(PPh3) (CH2PPh2)] (9). Treatment of 3 or 9 with nBuLi or tBuLi and then PPh2Cl gives the diphosphido systems [(η5-C5H4PPh2)Re(NO) (PPh3)-((CH2)nPPh2)] (n = 0/1, 5/11). Reactions of 5 and 11 with [Rh(NBD)Cl]2/AgPF6 (NBD = norbornadiene) give the rhenium/rhodium chelate complexes [(η5-C5H4-PPh2)Re(NO) (PPh3)((μ-CH2)nPPh 2)Rh-(NBD)]+PF6- (n = 0/1, 6+/12+ PF6-; 30-32% overall from commercial Re2(CO)10). The crystal structures of 6+ PF6- and 12+ PF6- are compared to those of 3 and 9, and other rhodium complexes of chelating bis(diphenylphosphines). The chiral pockets defined by the PPh2 groups show unusual features. Four alkenes of the type (Z)-RCH=C(NHCOCH3)CO2R′ are treated with H2 (1 atm) and (R)-6+ PF6- or (S)-12+ PF6- (0.5 mol%) in THF at room temperature. Protected amino acids are obtained in 70-98% yields and 93-82 % ee [(R)-6+ PF6-] or 72-60% ee [(S)-12+ PF6- ]. Pressure and temperature effects are defined, and turnover numbers of > 1600 are realized.
Enantioselective hydrogenation of N-acetyldehydroamino acids over supported palladium catalysts
Szoellosi, Gyoergy,Szabo, Emese,Barto, Mihaly
, p. 405 - 410 (2007)
The enantioselective hydrogenation of two N-acetyldehydroamino acids over Cinchona alkaloid-modified, supported palladium catalysts has been studied. Moderate enantioselectivities, up to 36%, were obtained in the hydrogenation of 2-acetamidocinnamic acid over cinchonidine-modified Pd/TiO2 under low hydrogen pressure. Increase in the pressure or use of benzylamine as additive led to a gradual decrease in the enantiomeric excess and eventually inversion of the sense of the enantioselectivity. On the contrary, the optical purity of the product resulting from the hydrogenation of 2-acetamidoacrylic acid was significantly increased by addition of benzylamine to the reaction mixture. Enantiomeric excess values up to 58% and 60% were obtained over Pd/Al 2O3 modified by cinchonidine and cinchonine, respectively. These optical purities are the best obtained in the hydrogenation of dehydroamino acid derivatives over chirally modified heterogeneous metal catalysts.
Artificial metalloenzymes for enantioselective catalysis based on biotin-avidin
Collot, Jerome,Gradinaru, Julieta,Humbert, Nicolas,Skander, Myriem,Zocchi, Andrea,Ward, Thomas R.
, p. 9030 - 9031 (2003)
Homogeneous and enzymatic catalysis offer complementary means to generate enantiomerically pure compounds. Incorporation of achiral biotinylated rhodium-diphosphine complexes into (strept)avidin yields artificial metalloenzymes for the hydrogenation of N-protected dehydroamino acids. A chemogenetic optimization procedure allows one to produce (R)-acetamidoalanine with 96% enantioselectivity. These hybrid catalysts display features reminiscent both of enzymatic and of homogeneous systems. Copyright
Mono- and bidentate phosphinanes - New chiral ligands and their application in catalytic asymmetric hydrogenations
Ostermeier, Markus,Priess, Jan,Helmchen, Guenter
, p. 612 - 614 (2002)
Obvious but unknown in asymmetric catalysis were chiral six-membered-ring phosphanes and secondary phosphanes. As first examples of such lingands, oxaphosphinanes were now prepared and examined in asymmetric hydrogenation. With the monodentate oxaphosphinane 1, for example, 96% ee was achieved with itaconic acid as the substrate and 97.5% ee was achieved with the chelate ligand 2 and 2-acetamidoacrylic acid as the substrate.
Application of P-chirogenic bisphospholane ligands to rhodium catalyzed asymmetric hydrogenation of α- and β-acetamido dehydroamino acid derivatives
Hoge, Garrett,Samas, Brian
, p. 2155 - 2157 (2004)
Two previously reported P-chirogenic bisphospholane rhodium catalysts have been applied to the asymmetric hydrogenation of α- and β-acetamido dehydroamino acid derivatives. For α-acetamido dehydroamino acid derivatives, catalyst 4 produced very high enantiomeric excesses. These are contrasted with the previously reported enantiomeric excesses using catalyst 2. Both catalysts provide excellent enantioselectivity (96%) for the β-acetamido dehydroamino acid derivative, (E)-methyl 3-acetamido-2- butenoate. However, catalyst 2 produces higher enantioselectivity (89%) for the (Z)-isomer when compared to catalyst 4 (83%).
Recyclable diguanidinium-BINAP and PEG-BINAP supported catalysts: Syntheses and use in Rh(I) and Ru(II) asymmetric hydrogenation reactions
Guerreiro, Patricio,Ratovelomanana-Vidal, Virginie,Genêt, Jean-Pierre,Dellis, Philippe
, p. 3423 - 3426 (2001)
The syntheses of new recyclable cationic BINAP type ligand diguanidinium 1 and PEG-bound BINAP ligand 2 are described. The use of ethylene glycol instead of water increased the enantioselectivity in the ruthenium-promoted hydrogenation reaction of functionalized ketones. These catalysts are highly active (catalyst/substrate ratio up to 1:10 000, up to 99% e.e.). The rhodium-mediated hydrogenation of acetamidoacrylic acid was also examined using 1 and 3 as chiral auxiliaries.
