19436-52-3Relevant articles and documents
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.
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.
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.
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
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%).
Diastereoselective synthesis of diphosphines, effect of their configuration in asymmetric catalysis
Pellon, Pascal,Le Goaster, Celine,Toupet, Loic
, p. 4713 - 4716 (1996)
The addition of diphenylphosphine-borane complex on the activated diene 2b (prepared from D-mannitol), led to the three diastereomeric diphosphines 1b, 3 and 4. Effect of the configuration of those diphosphines was observed in the catalytic α-acetamidoacrylic acid hydrogenation.
KetoABNO/NOx Cocatalytic Aerobic Oxidation of Aldehydes to Carboxylic Acids and Access to α-Chiral Carboxylic Acids via Sequential Asymmetric Hydroformylation/Oxidation
Miles, Kelsey C.,Abrams, M. Leigh,Landis, Clark R.,Stahl, Shannon S.
supporting information, p. 3590 - 3593 (2016/08/16)
A method for aerobic oxidation of aldehydes to carboxylic acids has been developed using organic nitroxyl and NOx cocatalysts. KetoABNO (9-azabicyclo[3.3.1]nonan-3-one N-oxyl) and NaNO2 were identified as the optimal nitroxyl and NOx sources, respectively. The mildness of the reaction conditions enables sequential asymmetric hydroformylation of alkenes/aerobic aldehyde oxidation to access α-chiral carboxylic acids without racemization. The scope, utility, and limitations of the oxidation method are further evaluated with a series of achiral aldehydes bearing diverse functional groups.
"Backdoor Induction" of chirality in asymmetric hydrogenation with rhodium(I) complexes of amino acid substituted triphenylphosphane ligands
Kokan, Zoran,Kirin, Srecko I.
supporting information, p. 8154 - 8161 (2014/01/06)
This paper describes the synthesis and characterization of 5-(diphenylphosphanyl)isophthalic acid bioconjugates (Lig-[R]2). In addition to symmetrically disubstituted conjugates with amino acids, peptides or amines, a convenient one-pot, two-step procedure for the synthesis of conjugates bearing two different substituents is reported. The 28 prepared phosphanes were used as monodentate ligands in the rhodium(I)-catalyzed hydrogenation of 2-acetamidoacrylate and (Z)-α-acetamidocinnamate. The ligand with the smallest side-chain substituents Lig-[Ala-OMe]2 (1a) revealed the highest selectivity, with up to 84 % ee. The catalysts presented herein are models of artificial metalloenzymes in which the outer-coordination sphere controls the selectivity in catalysis. The chirality of distant hydrogen-bonded amino acids is transmitted by "backdoor induction" to the prochiral RhI center. Models of artificial metalloenzymes are presented in which the outer-coordination sphere controls the selectivity in catalysis. The chirality of distant hydrogen-bonded amino acids or amines is transmitted by "backdoor induction" to the prochiral RhI center. Copyright
