2901-75-9Relevant academic research and scientific papers
Membrane Aerated Hydrogenation: Enzymatic and Chemical Homogeneous Catalysis
Greiner, Lasse,Müller, Daniela H.,Van Den Ban, Eyke C. D.,W?ltinger, Jens,Wandrey, Christian,Liese, Andreas
, p. 679 - 683 (2003)
Among the most successful systems for homogeneous catalysis, hydrogenation catalysts capable of activating molecular hydrogen, take outstanding roles in research laboratories and in industry. To open up the field of continuous catalytic hydrogenations a novel membrane reactor concept was developed and successfully applied for hydrogenations with dihydrogen both for chemical and for enzymatic catalysis. The hydrogenase I of the archaeon Pyrococcus furiosus was utilized for the continuous hydrogenation of NADP+ to NADPH with recycling of the enzyme by means of ultrafiltration. The well known PyrPhos-Rh system was used for the enantioselective synthesis of an amino acid derivative by hydrogenation.
Preparation of d,l-phenylalanine by amidocarbonylation of benzyl chloride
De Vries, Johannes G.,De Boer, Rene P.,Hogeweg, Marjo,Gielens, Esther E. C. G.
, p. 1842 - 1846 (1996)
The preparation of d,l-phenylalanine via amidocarbonylation of benzyl chloride with acetamide and CO/H2 is described. The rate of the reaction is dependent upon the CO pressure below 250 bar, but independent of the hydrogen pressure. A reaction temperature of 100°C gives optimum yields. A relatively large amount of the catalyst, Co2(CO)8, is needed for complete conversion because of inhibition caused by hydrogen chloride which is formed during the reaction. Addition of NaHCO3 removes HCl as insoluble NaCl, resulting in improved conversion and selectivity of the reaction. It also allows the use of a stoichiometric amount of acetamide, whereas a 2-to 3-fold excess of acetamide is needed for complete conversion of benzyl chloride without NaHCO3. Amidocarbonylation of benzyl alcohol gave d,l-phenylalanine in only 8% yield.
Mechanism of hydrolysis of azalactones catalyzed by a complex of Cu(II) with (S)-2-[(N-benzylpropyl)amino]benzaldoxime
Belokon',Bachurina,Tararov,Saporovskaya
, p. 422 - 429 (1992)
The hydrolysis of 2-methyl-4-benzyl-5(4H)oxazolone (MBA) in a mixture of water and MeCN has been studied - both the spontaneous reaction and that catalyzed by a complex of Cu(II) with (S)-2-[(N-benzylpropyl)amino]benzaldoxime (1). It has been shown that the complex 1 is an effective catalyst for the hydrolysis of MBA (chymotrypsin does not catalyze MBA hydrolysis). The mechanism of MBA hydrolysis catalyzed by this complex includes the formation of a mixed catalyst-substrate complex in which the MBA is coordinated with the metal ion through the N3 atom. It is suggested that the oxygen atom of the ionized oxime group in such a complex attacks the imine C2 atom of the MBA intramolecularly; this is the rate-determining stage. The change in the order of hydrolysis with respect to the catalyst from 1 to 1/2 when the concentration of 1 is increased indicates that the complex catalyst exists in aqueous solution in two forms, dimeric and monomeric, which are in equilibrium, and only the monomeric form of the complex is responsible for the catalysis. With an excess of the substrate we observe inhibition of the MBA hydrolysis - possibly an indirect indication of participation in the transition state by a water molecule coordinated in an apical position of the complex, which is displaced by excess substrate.
The η5-(σ-P,π-arene) chelating H-MOP ligand in an optically and catalytically active rhodium(I) complex
Soleilhavoup, Michele,Viau, Lydie,Commenges, Gerard,Lepetit, Christine,Chauvin, Remi
, p. 207 - 212 (2003)
(R)-methylbinapium, a Hayashi-type phosphonium-MOP ligand, reacts with [Rh(cod)2][BF4] in ethanol to afford the chiral mixed bis(monophosphane)rhodium(I) complex [Rh(η5-H-MOP)(MePh2P)][BF4]. The constitutional and geometrical features of this complex have been determined by exhaustive 1H, 11B, 13C, 31P and 103Rh 1-D, 2-D and NOE NMR spectroscopy and optical rotation measurements. The chelating η5-(γ-phosphanyldiene) ligand character of H-MOP in this complex is an extension to Rh1 of similar coordination modes studied by Pregosin in the coordination sphere of RuII. The process of its formation relies on an enantiospecific reductive cleavage of a P+-C bond, which is also reminiscent of Pregosin's P-C bond cleavages in the ruthenium series. The complex is a catalytic precursor for the hydrogenation of (Z)-αacetamidocinnamic acid. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
Disperse amphiphilic submicron particles as non-covalent supports for cationic homogeneous catalysts
Sablong, Rafael,Van Der Vlugt, Jarl Ivar,Thomann, Ralf,Mecking, Stefan,Vogt, Dieter
, p. 633 - 636 (2005)
A simple method for the effective immobilization of homogeneous catalysts on polystyrene colloids via non-covalent binding is demonstrated. Stable latices with sufficiently high loading of accessible borate anions are prepared via emulsion polymerization. Incorporation of cationic rhodium complexes, supported via their borate counter-anion is efficient, and these supported homogeneous catalysts maintain constant catalytic activity for C=C hydrogenation during several recycles, with very low metal leaching.
Kinetic study of homogeneous alkene hydrogenation by model discrimination
Greiner, Lasse,Ternbach, Michel Brik
, p. 1392 - 1396 (2004)
Model discrimination is one of the methods of choice to obtain a valid kinetic description of a catalytic reaction with minimal experimental effort. It allows fast judgement of catalyst behavior and its suitability for process development. Using dynamic experiments and modeling, the kinetics of a homogeneous hydrogenation with cationic rhodium-PyrPhos {[Rh(PyrPhos)(COD)] BF4} were investigated. A set of three batch experiments allowed the discrimination between 6 models. Qualitative and quantitative descriptions of the kinetic behavior could be derived. Most importantly, evidence for catalyst deactivation was gained.
Hydrogenation of α-acetamidocinnamic acid with polystyrene-supported rhodium catalysts
Bhaduri, Sumit,Lahiri, Goutam Kumar,Munshi, Pradip
, p. 151 - 155 (2000)
Divinylbenzene cross-linked chloromethylated polystyrene has been functionalised with cinchonine, ephedrine, 3S,4S-N-benzylpyrrolidinediol and four achiral amines. The resins have been used as supports for anchoring [Rh(CO)2Cl2]-. The polymer-supported complex has been tested as a catalyst precursor for the hydrogenation of α-acetamidocinnamic acid. Highest rate and modest enantioselectivity are obtained with cinchonine functionalized polymer-supported complex. This complex also undergoes reversible decarbonylation.
Chiral rhodium complexes covalently anchored on carbon nanotubes for enantioselective hydrogenation
Gheorghiu,Machado,Salinas-Martinez De Lecea,Gouygou,Roman-Martinez,Serp
, p. 7455 - 7463 (2014)
Chiral rhodium hybrid nanocatalysts have been prepared by covalent anchorage of pyrrolidine-based diphosphine ligands onto functionalized CNTs. This work constitutes the first attempt at covalent anchoring of homogeneous chiral catalysts on CNTs. The catalysts, prepared with two different chiral phosphines, were characterized by ICP, XPS, N2 adsorption and TEM, and have been tested in the asymmetric hydrogenation of two different substrates: methyl 2-acetamidoacrylate and α-acetamidocinnamic acid. The hybrid nanocatalysts have shown to be active and enantioselective in the hydrogenation of α-acetamidocinnamic acid. A good recyclability of the catalysts with low leaching and without loss of activity and enantioselectivity was observed. This journal is the Partner Organisations 2014.
Minisci-Type Alkylation of N-Heteroarenes by N-(Acyloxy)phthalimide Esters Mediated by a Hantzsch Ester and Blue LED Light
Kyne, Sara Helen,Li, Jiacheng,Siang Tan, Suan,Wai Hong Chan, Philip
supporting information, (2022/01/11)
A synthetic method that enables the Hantzsch ester-mediated Minisci-type C2-alkylation of quinolines, isoquinolines and pyridines by N-(acyloxy)phthalimide esters (NHPI) under blue LED (light emitting diode) light (456 nm) is described. Achieved under mild reaction conditions at room temperature, the metal-free synthetic protocol was shown to be applicable to primary, secondary and tertiary NHPIs to give the alkylated N-heterocyclic products in yields of 21–99%. On introducing a chiral phosphoric acid, an asymmetric version of the reaction was also realised and provided product enantiomeric excess (ee) values of 53–99%. The reaction mechanism was delineated to involve excitation of an electron-donor acceptor (EDA) complex, formed from weak electrostatic interactions between the Hantzsch ester and NHPI, which generates the posited radical species of the redox active ester that undergoes addition to the N-heterocycle.
Cobalt-Catalyzed Asymmetric Hydrogenation of α,β-Unsaturated Carboxylic Acids by Homolytic H2 Cleavage
Chirik, Paul J.,Shevlin, Michael,Zhong, Hongyu
supporting information, (2020/03/13)
The asymmetric hydrogenation of α,β-unsaturated carboxylic acids using readily prepared bis(phosphine) cobalt(0) 1,5-cyclooctadiene precatalysts is described. Di-, tri-, and tetra-substituted acrylic acid derivatives with various substitution patterns as well as dehydro-α-amino acid derivatives were hydrogenated with high yields and enantioselectivities, affording chiral carboxylic acids including Naproxen, (S)-Flurbiprofen, and a d-DOPA precursor. Turnover numbers of up to 200 were routinely obtained. Compatibility with common organic functional groups was observed with the reduced cobalt(0) precatalysts, and protic solvents such as methanol and isopropanol were identified as optimal. A series of bis(phosphine) cobalt(II) bis(pivalate) complexes, which bear structural similarity to state-of-the-art ruthenium(II) catalysts, were synthesized, characterized, and proved catalytically competent. X-band EPR experiments revealed bis(phosphine)cobalt(II) bis(carboxylate)s were generated in catalytic reactions and were identified as catalyst resting states. Isolation and characterization of a cobalt(II)-substrate complex from a stoichiometric reaction suggests that alkene insertion into the cobalt hydride occurred in the presence of free carboxylic acid, producing the same alkane enantiomer as that from the catalytic reaction. Deuterium labeling studies established homolytic H2 (or D2) activation by Co(0) and cis addition of H2 (or D2) across alkene double bonds, reminiscent of rhodium(I) catalysts but distinct from ruthenium(II) and nickel(II) carboxylates that operate by heterolytic H2 cleavage pathways.
