Xn:Harmful;
106-36-5Relevant articles and documents
Substrate conformations set the rate of enzymatic acrylation by lipases
Syren, Per-Olof,Hult, Karl
, p. 802 - 810 (2010)
Acrylates represent a class of α,β-unsaturated compounds of high industrial importance. We investigated the influence of substrate conformations on the experimentally determined reaction rates of the enzyme-catalysed transacylation of methyl acrylate and derivatives by ab initio DFT B3LYP calculations and molecular dynamics simulations. The results supported a least-motion mechanism upon the sp2 to sp3 substrate transition to reach the transition state in the enzyme active site. This was in accordance with our hypothesis that acrylates form productive transition states from their low-energy s-sis/s-trans conformations. Apparent kcat values were measured for Candida antarctica lipase B (CALB), Humicola insolens cutlnase and Rhizomucor miehei lipase and were compared to results from computer simulations. More potent enzymes for acryltransfer, such as the CALB mutant V190A and acrylates with higher turnover numbers, showed elevated populations of productive transition states.
Manganese Pincer Complexes for the Base-Free, Acceptorless Dehydrogenative Coupling of Alcohols to Esters: Development, Scope, and Understanding
Nguyen, Duc Hanh,Trivelli, Xavier,Capet, Frédéric,Paul, Jean-Fran?ois,Dumeignil, Franck,Gauvin, Régis M.
, p. 2022 - 2032 (2017)
Aliphatic PNP pincer-supported earth-abundant manganese(I) dicarbonyl complexes behave as effective catalysts for the acceptorless dehydrogenative coupling of a wide range of alcohols to esters under base-free conditions. The reaction proceeds under neat conditions, with modest catalyst loading and releasing only H2 as byproduct. Mechanistic aspects were addressed by synthesizing key species related to the catalytic cycle (characterized by X-ray structure determination, multinuclear (1H, 13C, 31P, 15N, 55Mn) NMR, infrared spectroscopy, inter alia), by studying elementary steps connected to the postulated mechanism, and by resorting to DFT calculations. As in the case of related ruthenium and iron PNP catalysts, the dehydrogenation results from cycling between the amido and amino-hydride forms of the PNP-Mn(CO)2 scaffold. For the dehydrogenation of alcohols into aldehydes, our results suggest that the highest energy barrier corresponds to the hydrogen release from the amino-hydride form, although its value is close to that of the outer-sphere dehydrogenation of the alcohol into aldehyde. This contrasts with the ruthenium and iron catalytic systems, where dehydrogenation of the substrate into aldehyde is less energy-demanding compared to hydrogen release from the cooperative metal-ligand framework.
Reaction of Primary Alkyl Hydroperoxides with Sulphamoyl Chloride: Alkyl(sulphamoyl)peroxides. Peroxo Compounds, XVIII
Blaschette, Armand,Safari, Hassan
, p. 875 - 880 (1984)
The novel peroxides H2NSO2OOCH2R (1a: R=CH2CH3; 1b: R=CH2CH2CH3) are obtained by reaction of sulphamoyl chloride with the appropriate hydroperoxides in the presence of pyridine (temperature below -30 deg C, solvent diethyl ether).The solvent-free liquids 1 deflagrate at ca. 0 deg C.Hydrolysis or ammonolysis of 1 generates the hydroperoxide and sulphamic acid or sulphamide, respectively.Controlled thermolysis of 1 affords sulphamic acid and carbonyl compounds, i.e. propanal and n-propyl propanoate from 1a, butanal, 2-methylpropanal and n-butyl n-butyrate from 1b.These products suggest a nonradical cyclic decomposition path-way. - Keywords: Sulphamoyl chloride, reaction with n-alkyl hydroperoxides; n-Alkyl hydroperoxides, reaction with sulphamoyl chloride; Alkyl(sulphamoyl)peroxides, preparation and thermolysis
Predicting a Sharp Decline in Selectivity for Catalytic Esterification of Alcohols from van der Waals Interactions
Friend, Cynthia M.,Luneau, Mathilde,Madix, Robert J.,Reece, Christian
, p. 10864 - 10867 (2020)
Controlling the selectivity of catalytic reactions is a critical aspect of improving energy efficiency in the chemical industry; thus, predictive models are of key importance. Herein the performance of a heterogeneous, nanoporous Au catalyst is predicted for the complex catalytic self-coupling of the series of C2–C4 alkyl alcohols, based solely on the known kinetics of the elementary steps of the catalytic cycle for methanol coupling, using scaling methods augmented by density functional theory. Notably, a sharp decrease in selectivity for ester formation with increasing molecular weight to favor the aldehyde due to van der Waals interactions of reaction intermediates with the surface was predicted and subsequently verified quantitatively by experiment. Further, the agreement between theory and experiment clearly demonstrates the efficacy of this approach for building a predictive model of catalytic behavior for a homologous set of reactants using a small set of experimental information.
The role of functionalized phosphines in the hydrogenation of carboxylic acids in the presence of phosphine substituted hydrido ruthenium complexes
Salvini, Antonella,Frediani, Piero,Bianchi, Mario,Piacenti, Franco,Pistolesi, Leonardo,Rosi, Luca
, p. 218 - 228 (1999)
Hydrido ruthenium carbonyl complexes substituted by functionalized phosphines such as H4Ru4(CO)8[P(CH2OCOR) 3]4 have been synthesized and tested as catalysts in the hydrogenation of carboxylic acids. These complexes are more active than those reported previously, containing trialkyl- or triarylphosphines. On the basis of their behavior, their different activity has been explained in terms of an involvement of the phosphine ligand in the catalytic cycle. The ester group present in the phosphine P(CH2OCOR)3 is hydrogenated to produce an alcohol (RCH2OH) and a P(CH2OH) group which, in turn, reacts with the free acid present in solution to restore the P(CH2OCOR) group. This hypothesis has been confirmed by the reactivity of the possible intermediate H4Ru4(CO)8[P(CH2OH) 3]4 with acetic acid. Another support to this statement is the almost equal catalytic activity, displayed by H4Ru4(CO)8[P(CH2OCOR) 3]4 complexes, whatever the R group present, in the phosphine ligand, in the hydrogenation of carboxylic acids. These complexes, on the other hand, are less active than the corresponding tributylphosphine substituted ones in the hydrogenation of alkenes and ketones. Finally when the phosphine ligand is P(CH2CH2COOCH3)3 the ester group is not reduced and consequently the catalytic activity of this complex in the hydrogenation of carboxylic acids is very low.
CATALYTIC OXIDATION OF ALCOHOLS TO ESTERS WITH Ru3(CO)12
Blum, Yigal,Shvo, Youval
, p. 93 - 108 (1984)
Ru3(CO)12 is an efficient homogeneous catalyst precursor for the conversion 2RCH2OH-->RCO2CH2R.With aliphatic primary alcohols and benzylic alcohols yields and selectivities of ca. 90percent are obtained.The reaction requires a hydrogen acceptor molecule; triple bonds and activated double bonds, as well as ketones and aldehydes, function as H-acceptors.The reaction proceeds in two steps, with an aldehyde intermediate which subsequently oxidatively couples with an alcohol to generate an ester.In most cases the aldehyde is present in a steady state concentration implying the presence of an equilibrium system.A disproportionation alcohol aldehyde is a component of the above system.A catalytically active intermediate complex, Ru(CO)6(Ph2C2), was isolated when Ph2C2 was used as an acceptor.
Transesterification via Baeyer-Villiger oxidation utilizing potassium peroxydisulfate (K2S2O8) in acidic media
Zarrabi,Mahmoodi,Marvi
, p. 889 - 891 (2010)
Baeyer-Villiger oxidation of ketones with potassium peroxydisulfate (K 2S2O8) and sulfuric acid generates the anticipated esters or lactones. These products are transformed into new esters (or hydroxy esters) in the presence of alcohols via transesterification under Baeyer-Villiger reaction conditions in one pot. Springer-Verlag 2010.
Solvent-free oxidation of straight-chain aliphatic primary alcohols by polymer-grafted vanadium complexes
Chaudhary, Nikita,Haldar, Chanchal,Kachhap, Payal
, (2021)
Oxidovanadium(IV) complexes [VO(tertacac)2] (1), [VO(dipd)2] (2), and [VO(phbd)2] (3) were synthesized by reacting [VO(acac)2] with 2,2,6,6-tetramethyl-3,5-hepatanedione, 1,3-diphenyl-1,3-propanedione, and 1-phenyl-1,3-butanedione, respectively. Imidazole-modified Merrifield resin was used for the heterogenization of complexes 1–3. During the process of heterogenization, the V4+ center in complex 2 converts into V5+, whereas the other two complexes 1 and 3 remain in the oxidovanadium(IV) state in the polymer matrix. Theoretically, calculated IPA values of 1–3 suggest that 2 is prone to oxidation compared with 1 and 3, which was also supported by the absence of EPR lines in 5. Polymer-supported complexes Ps-Im-[VIVO(tertacac)2] (4), Ps-Im-[VVO2(dipd)2] (5), and Ps-Im-[VIVO(phbd)2] (6) were applied for the solvent-free heterogenous oxidation of a series of straight-chain aliphatic alcohols in the presence of H2O2 at 60°C and showed excellent substrate conversion specially for the alcohols with fewer carbon atoms. Higher reaction temperature improves the substrate conversion significantly for the alcohols containing more carbon atoms such as 1-pentanol, 1-hexanol, and 1-heptanol while using optimized reaction conditions. However, alcohols with fewer carbon atoms seem less affected by reaction temperatures higher than the optimized temperature. A decreasing trend in the selectivity(%) of carboxylic acid was observed with increasing carbon atoms among the examined alcohols, whereas the selectivity towards aldehydes increased. The order of efficiency of the supported catalysts is 4 > 6 > 5 in terms of turnover frequency (TOF) values and substrate conversion, further supported by theoretical calculations.
Hydrogenation of carboxylic acids catalyzed by half-sandwich complexes of iridium and rhodium
Brewster, Timothy P.,Miller, Alexander J. M.,Heinekey, D. Michael,Goldberg, Karen I.
, p. 16022 - 16025 (2013)
A series of half-sandwich Ir and Rh compounds are demonstrated to be competent catalysts for the hydrogenation of carboxylic acids under relatively mild conditions. Of the structurally diverse group of catalysts tested for activity, a Cp*Ir complex supported by an electron-releasing 2,2′-bipyridine ligand was the most active. Higher activity was achieved with employment of Bronsted or Lewis acid promoters. Mechanistic studies suggest a possible reaction pathway involving activated carboxylic acid substrates. The hydrogenation reaction was shown to be general to a variety of aliphatic acids.
Highly efficient use of NaOCI in the Ru-catalysed oxidation of aliphatic ethers to esters
Gonsalvi, Luca,Arends, Isabel W.C.E.,Sheldon, Roger A.
, p. 202 - 203 (2002)
The selectivity of α-oxidation of ethers to esters via RuNaOCI can be dramatically improved by pH control, at high substrate to catalyst ratios using a stoichiometric amount of hypochlorite in biphasic media at room temperature.
