- Effective oxidation of alcohols with H5IO6 catalyzed by nickel(II) schiff base complexes
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Nickel(II)-Schiff base-triphenylphosphine complexes catalyze oxidation of alcohols to carbonyls in presence of minimum amount of periodic acid. The catalytic oxidation was developed in mild conditions and showed good yields. The effects of temperature, time, and concentrations of catalyst and co-oxidant were studied. Higher catalytic activity has been observed for NiL1 compared to the other complexes.Copyright Taylor & Francis Group, LLC.
- Ramakrishna, Dileep,Bhat, Badekai Ramachandra
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- Effect of CTAB micelle on the oxidation of L-Leucine by N-Bromophthalimide: A kinetic study
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The effect of cationic surfactant cetyltrimethylammonium bromide (CTAB) on the oxidation of L-leucine by N-bromophthalimide (NBP) has been studied at 308 K. The reaction exhibits first order dependence on NBP and L-leucine and negative and fractional order dependence on HClO4. The effects of KCl, KBr, phthalimide and mercuric acetate have also been studied and summarized. The rate of reaction increased with an increase in dielectric constant of the medium. CTAB strongly catalyzes the reaction and typical k obs and CTAB profile was observed, i.e., with a progressive increase in CTAB, the reaction rate increased and after achieving a peak kobs decreased at higher concentrations of CTAB. The results are treated quantitatively in terms of "Piszkiewicz" and "Raghvan and Srinivasan's" models. The various activation parameters in presence and absence of CTAB have been also evaluated. A suitable mechanism consistent with the experimental findings has been proposed. The rate constant in micellar phase kM, cooperativity index (n), binding constant (K1 and K2) have been computed. by Oldenbourg Wissenschaftsverlag, Mu?nchen.
- Katre, Yokraj,Goyal, Namita,Kumar Singh, Ajaya
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- Mixed anionic-nonionic micelle catalysed oxidation of aliphatic alcohol in aqueous medium
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Oxidation of isoamyl alcohol was carried out under pseudo 1st order reaction condition in aqueous medium by chromic acid. In addition to single micelle, mixed anionic-nonionic micelle (SDS-TX 100) was found to be effective catalyst. Promoters in presence of micelle catalyst showed almost million fold rate acceleration. The product was confirmed by IR and NMR study. UV and NMR analysis were carried out to establish the formation of mixed micelle. Formation of active oxidant was confirmed by fluorescence measurement. Interactions between surfactant and substrate were analysed by NMR spectra. In addition to SDS catalysed Bpy promoted reaction combination of mixed micelle with Bpy promoter was found to show higher rate of oxidation. For single micelle catalysed path the observed rate constants follow the order kobs (SDS) > kobs (TX 100) and kobs (Phen) > kobs (Bpy) > kobs (PA) was observed for promoted reactions. In SDS micelle and mixed micelle kobs (Bpy) > kobs (Phen) > kobs (PA) was observed while in TX 100 micelle kobs (Phen) > kobs (Bpy) > kobs (PA) was found.
- Acharjee, Animesh,Ali, Md. Ansar,Chowdhury, Suman,Rakshit, Atanu,Saha, Bidyut,Singh, Bula
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- Catalytic oxidation of alcohols by nickel(II) Schiff base complexes containing triphenylphosphine in ionic liquid: An attempt towards green oxidation process
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A series of square planar nickel(II) complexes containing N,O donor Schiff base ligand, i.e. N-(2-pyridyl)-N′-(5-substituted-salicylidene)hydrazine and triphenylphosphine, have been synthesized and characterized by analytical and spectral methods. Catalytic activities of all the complexes have been studied for the oxidation of alcohols in ionic liquid media using NaOCl as oxidant.
- Ramakrishna, Dileep,Bhat, Badekai Ramachandra,Karvembu, Ramasamy
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- Effective oxidation of alcohols by Iron(III)-Schiff base-triphenylphosphine complexes
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Iron(III)-Schiff base-triphenylphosphine complexes catalyze the oxidation of alcohols to their corresponding carbonyl compounds in presence of hydrogen peroxide in good yields.
- Rani, Sandya,Bhat, Badekai Ramachandra
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- Isobutene hydroformylation in catalytic systems based on rhodium compounds and polyelectrolytes
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The catalytic properties of water-soluble systems based on rhodium complexes and polyelectrolytes in isobutene hydroformylation were studied. All of the catalytic systems exhibited an unexpectedly high activity under the conditions where homogeneous hydroformylation virtually did not occur in the presence of conventional rhodium catalysts. A stable catalytic system based on acacRh(CO)2 - PEG complex was proposed, allowing isobutene hydroformylation to be performed with a high activity under mild conditions.
- Sharikova,Kolesnichenko,Markova,Slivinskii
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- Hydroformylation of olefins in the presence of rhodium carbonyl catalysts immobilized on polymeric pyrrolidinopyridines
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The hydroformylation of olefins in the presence of catalytic systems based on RhCl3 and polymeric pyrrolidinopyridines was studied. It was shown that the catalytic system has high activity in the hydroformylation of isobutylene under conditions when the activity of conventional homogeneous catalysts is low. The polymeric catalysts are also thermostable. The effect of solvents on the catalytic properties of the system was studied.
- Terekhova,Kolesnichenko,Alieva,Markova,Trukhmanova,Slivinsky,Plate
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- Purification and characterization of isoamyl alcohol oxidase ("Mureka"-forming enzyme)
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Isoamyl alcohol oxidase (IAAOD) was purified to apparent homogeneity on SDS-PAGE from ultrafiltration (UF) concentrated sake. IAAOD was a glycoprotein, a monomeric protein with an apparent molecular mass of 73 and 87 kDa, by SDS-PAGE and gel filtration on HPLC, respectively. IAAOD showed high substrate specificity toward C5 branched-chain alkyl alcohol (isoamyl alcohol), and no activity toward shorter (C1-C4) or longer (C7-C10) alkyl alcohols tested. IAAOD was stable between pH 3.0-6.0 at 25°C. The optimum pH was 4.5 at 35°C. Heavy metal ions, p-chloromercuribenzoate (PCMB), hydrazine, and hydroxylamine strongly inhibited the enzyme activity, and an anti-oxidant like L-ascorbate did also. Isovaleraldehyde was produced markedly in pasteurized sake by adding purified IAAOD, therefore, we concluded that it was the enzyme that causes formation of mureka, an off-flavor of sake, the main component of which is isovaleraldehyde.
- Yamashita, Nobuo,Motoyoshi, Toru,Nishimura, Akira
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- Aerobic oxidation of alcohols with ruthenium catalysts in ionic liquids
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The aerobic oxidations of aliphatic and aromatic alcohols into the corresponding aldehydes and ketones have been efficiently performed with several ruthenium catalysts in various ammonium salts under low oxygen pressure and without any co-catalyst.
- Wolfson, Adi,Wuyts, Stijn,De Vos, Dirk E.,Vankelecom, Ivo F.J.,Jacobs, Pierre A.
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- Mechanistic study of [RuCl3(H2O)2OH]- catalyzed oxidation of L-leucine by acidic N-bromophthalimide
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Kinetic studies in homogenous Ru(III) catalyzed oxidation of L-leucine (Leu), by N-bromophthalimide (NBP) in the presence of perchloric acid have been made at 303 K using mercuric acetate as Br- ion scavenger. The reaction follows first-order kinetics with respect to [NBP]. In the lower concentration range of Leu and Ru(III) chloride, the reaction follows first-order kinetics but tends to zero at higher concentration. A positive effect of [Cl-] was observed in the oxidation of Leu. An increase in the rate of reaction with the decrease in dielectric constant of the medium was observed while negative effect was observed for [H+]. The rate of oxidation is unaffected by the change in [phthalimide (NHP)]. Rate of reaction decreased with increase in ionic strength of the medium. The main oxidation products of the reactions were identified as aldehyde, ammonia and CO2 for the oxidation of Leu. From the effect of temperature (298-318 K) on the reaction rate, various activation parameters have been calculated and on the basis of these parameters, a suitable explanation for the reaction mechanism has been given.
- Jain, Bhawana,Singh, Ajaya Kumar,Negi, Reena
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- Kinetic studies of transition metal ion catalyzed oxidation of some fragrance alcohols
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The controlled oxidation of the aliphatic alcohols 2-propanol, 2-butanol and 3-methyl-1-butanol to the corresponding carbonyl compounds has been carried out using Ce (IV) in acidic medium in the absence and presence of transition metal ions of the first series. The aliphatic alcohols are widely used as diluents in the perfumery industry. The oxidation reaction was monitored under pseudo unimolecular conditions with respect to [Ce (IV)] in the temperature range 303-318 K. Aliquots of the reaction were withdrawn at regular time intervals, quenched using ice and the unreacted oxidant was estimated titrimetrically using standard ferrous ammonium sulphate with ferroin as indicator. The pseudo first order rate constants were determined from the linear plots of log (a-x) versus time. It was observed that the rate increases with alcohol concentration but decreases with Ce(IV) concentration. This has been attributed to the formation of unreactive dimeric [Ce(IV)]2at higher concentration of Ce(IV). Potassium sulfate was used to study the effect of ionic strength on the oxidation rate. The thermodynamic activation parameters were determined from the effect of temperature on the oxidation rate. The Ru(VIII), Os(VIII) and Cr(VI) ions have been exhaustively used to catalyse a variety of organic reactions. In the present study, relatively low-cost metal ions of the first transition series have been used as effective catalysts for the oxidation of the fragrance alcohols under study. The reaction mechanism suggested for the oxidation process involves intermediates with hypervalent ions i.e., M(III). The catalytic efficiency of the metal ions is based on the stability of the complexes formed as reaction intermediates which in turn depends on the charge density of the metal ions involved. We have observed some discrepancies as the experimentally determined sequence of catalytic efficiency of metal ions does not follow the theoretically expected sequence. Suitable reaction mechanisms have been suggested for the oxidation of the alcohols in the absence and presence of transition metal ions. In the absence of metal ions, the oxidation rates of aliphatic alcohols the sequence: 2-propanol > 2-butanol > 3-methyl-1-butanol. The relative rates of oxidation of alcohols have been discussed and explained on the basis of structures, steric factors and isomeric characteristics of the perfumery alcohols under study.
- Prabhu,Parbat,Tandel
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- Dual utility of a single diphosphine-ruthenium complex: A precursor for new complexes and, a pre-catalyst for transfer-hydrogenation and Oppenauer oxidation
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The diphosphine-ruthenium complex, [Ru(dppbz)(CO)2Cl2] (dppbz = 1,2-bis(diphenylphosphino)benzene), where the two carbonyls are mutually cis and the two chlorides are trans, has been found to serve as an efficient precursor for the synthesis of new complexes. In [Ru(dppbz)(CO)2Cl2] one of the two carbonyls undergoes facile displacement by neutral monodentate ligands (L) to afford complexes of the type [Ru(dppbz)(CO)(L)Cl2] (L = acetonitrile, 4-picoline and dimethyl sulfoxide). Both the carbonyls in [Ru(dppbz)(CO)2Cl2] are displaced on reaction with another equivalent of dppbz to afford [Ru(dppbz)2Cl2]. The two carbonyls and the two chlorides in [Ru(dppbz)(CO)2Cl2] could be displaced together by chelating mono-anionic bidentate ligands, viz. anions derived from 8-hydroxyquinoline (Hq) and 2-picolinic acid (Hpic) via loss of a proton, to afford the mixed-tris complexes [Ru(dppbz)(q)2] and [Ru(dppbz)(pic)2], respectively. The molecular structures of four selected complexes, viz. [Ru(dppbz)(CO)(dmso)Cl2], [Ru(dppbz)2Cl2], [Ru(dppbz)(q)2] and [Ru(dppbz)(pic)2], have been determined by X-ray crystallography. In dichloromethane solution, all the complexes show intense absorptions in the visible and ultraviolet regions. Cyclic voltammetry on the complexes shows redox responses within 0.71 to -1.24 V vs. SCE. [Ru(dppbz)(CO)2Cl2] has been found to serve as an excellent pre-catalyst for catalytic transfer-hydrogenation and Oppenauer oxidation.
- Mukherjee, Aparajita,Bhattacharya, Samaresh
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p. 15617 - 15631
(2021/05/19)
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- Chemoselective hydrogenation of α,β-unsaturated aldehydes over Rh nanoclusters confined in a metal-organic framework
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Selective hydrogenation of α,β-unsaturated aldehydes to achieve high selectivity towards a desirable product is still a great challenge mainly because of the complex conjugate system. Herein, Rh nanoclusters encapsulated in MIL-101 (Cr), synthesized by the double solvent method, are able to selectively hydrogenate C-C of cinnamaldehyde, an α,β-unsaturated aldehyde and achieve over 98percent selectivity with a conversion of 98percent to a saturated aldehyde under mild conditions. Fourier transform infrared spectroscopy confirms that MIL-101 acts as an aldehyde protector to suppress the reactivity of C-O, and the X-ray photoelectron spectroscopy (XPS) data indicate that the electropositive Rh, owing to the electron transfer from Rh to MIL-101, preferentially absorbs C-C rather than C-O leading to -improvement of the selectivity towards saturated aldehydes. In addition, Rh@MIL-101 can also efficiently catalyse hydrodefluorination of aryl fluorides with good stability. This work provides a basic strategy to develop other selective heterogeneous catalystsviastructural modulation for synergetic catalysis.
- Liu, Qinglin,Li, Yinle,Fan, Yanan,Su, Cheng-Yong,Li, Guangqin
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p. 11442 - 11447
(2020/06/29)
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- Solvent-free, microwave assisted oxidation of alcohols with 4-hydroxypyridinium chlorochromate functionalized silica gel
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4-Hydroxypyridinium chlorochromate functionalized silica gel was found to be an efficient and reusable oxidant for the very fast oxidation of primary and secondary alcohols to the corresponding carbonyl compounds under solventfree conditions and microwave irradiation in excellent yields.
- AHMADI, Sayed Ali,GHALEHBANDI, Shermineh Sadat,GHAZANFARI, Dadkhoda,SHEIKHHOSSEINI, Enayatollah
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p. 283 - 289
(2020/10/06)
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- Selective Oxidation of Alcohols to Carbonyl Compounds over Small Size Colloidal Ru Nanoparticles
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The selective oxidation of alcohols to corresponding aldehydes is one of the most challenging problems in modern chemistry due to over-oxidation of these products further into corresponding acids and esters. Herein, we report an efficient and eco-friendly method for selective oxidation of aliphatic, unsaturated and aromatic alcohols to aldehydes (>90 %) using small size (2 nm) non-supported colloidal Ru nanoparticles. The selectivity rapidly decreases with increase of the size of nanoparticles (from 2 to 10 nm) or after their deposition over support. X-ray photoelectron spectroscopy suggests that this catalytic performance can be attributed to high content Ru?O species on the surface of small size Ru nanoparticles, which undergo reduction with formation of water and aldehyde and easy oxidation cycles during the reaction according to the Mars-van Krevelen mechanism. The presence of surface oxide layer over small size Ru nanoparticles suppresses over-oxidation of aldehydes to acids.
- Zhao, JingPeng,Hernández, Willinton Y.,Zhou, WenJuan,Yang, Yong,Vovk, Evgeny I.,Capron, Mickael,Ordomsky, Vitaly
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p. 238 - 247
(2019/11/14)
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- Phosphine ligand, preparation method and application thereof
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The invention provides a preparation method of a phosphine ligand and application of the phosphine ligand in catalyzing olefin hydroformylation reaction. A structural formula of the phosphine ligand is shown as the specification, wherein R, R1, R2 and R3 are selected from C1-C40 alkyl, alkenyl, alkynyl, and phenyl, substituted phenyl, naphthyl, anthryl, phenanthryl or other aromatic ring and aromatic heterocyclic substituents with higher carbon number. The preparation method of the phosphine ligand comprises the following step: carrying out one-step reaction on an isochroman salt and trisilylphosphine under the promotion of villiaumite. The phosphine ligand has strong stability and coordination ability, and can be well coordinated with cobalt, rhodium and other metals, the obtained complex can be used for hydroformylation reaction of terminal olefin, internal olefin, trisubstituted olefin and tetrasubstituted olefin, the catalyst dosage is small, the reaction conditions are mild, andthe yield and selectivity of aldehyde products are very high.
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Paragraph 0069-0071
(2020/07/13)
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- Chemoselective Hydrogenation of α,β-Unsaturated Carbonyls Catalyzed by Biomass-Derived Cobalt Nanoparticles in Water
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Herein, we report highly chemoselective hydrogenation of α,β-unsaturated carbonyls to saturated carbonyls catalyzed by cobalt nanoparticles supported on the biomass-derived carbon from bamboo shoots with molecular hydrogen in water, which is the first prototype using a heterogeneous non-noble metal catalyst for such organic transformation as far as we know. The optimal cobalt nanocatalyst, CoOx@NC-800, manifested remarkable activity and selectivity for hydrogenation of C=C in α,β-unsaturated carbonyls under mild conditions. A broad set of α,β-aromatic and aliphatic unsaturated carbonyls were selectively reduced to their corresponding saturated carbonyls in up to 99 % yields with good tolerance of various functional groups. Meanwhile, a new straightforward one-pot cascade synthesis of saturated carbonyls was realized with high activity and selectivity via the cross-aldol condensation of ketones with aldehydes followed by selective hydrogenation. More importantly, this one-pot strategy is applicable for the expedient synthesis of Loureirin A, a versatile bioactive and medicinal molecule, from readily available starting materials, further highlighting the practical utility of the catalyst. In addition, the catalyst can be easily separated for successive reuses without significant loss in both activity and selectivity.
- Song, Tao,Ma, Zhiming,Yang, Yong
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p. 1313 - 1319
(2019/01/25)
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- Method for selectively hydrogenating alpha, beta-unsaturated carbonyl compound by cobalt complex
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The invention provides a method for selectively hydrogenating an alpha, beta-unsaturated carbonyl compound. The method for selectively hydrogenating the alpha, beta-unsaturated carbonyl compound comprises the steps that first, a cobalt metal precursor and a carbene ligand are coordinated in a solution to obtain a cobalt complex, and the cobalt complex selectively enables the alpha, beta-unsaturated carbonyl compound to be reduced into a corresponding saturated carbonyl compound in a hydrogen atmosphere under the activation of an activator. The method for selectively hydrogenating the alpha, beta-unsaturated carbonyl compound has the main advantages that cobalt is used as a catalyst, and metal cobalt is cheap and easy to obtain relative to noble metal such as palladium, ruthenium, osmium, iridium and platinum, and the catalyst cost is greatly reduced; secondly, the carbene ligand used in the method has the advantages of simple structure, low price, strong coordination ability with cobalt atoms compared with a commonly used phosphine ligand; and finally, the addition of the activator can further significantly increase the activity of the cobalt catalyst. The hydrogenation reaction condition is mild, the reaction rate is high, substantially no carbonyl hydrogenation side reaction occurs, and the carbonyl compound can be obtained in a high yield.
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Paragraph 0067-0069
(2019/11/20)
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- An Engineered Alcohol Oxidase for the Oxidation of Primary Alcohols
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Structure-guided directed evolution of choline oxidase has been carried out by using the oxidation of hexan-1-ol to hexanal as the target reaction. A six-amino-acid variant was identified with a 20-fold increased kcat compared to that of the wild-type enzyme. This variant enabled the oxidation of 10 mm hexanol to hexanal in less than 24 h with 100 % conversion. Furthermore, this variant showed a marked increase in thermostability with a corresponding increase in Tm of 20 °C. Improved solvent tolerance was demonstrated with organic solvents including ethyl acetate, heptane and cyclohexane, thereby enabling improved conversions to the aldehyde by up to 30 % above conversion for the solvent-free system. Despite the evolution of choline oxidase towards hexan-1-ol, this new variant also showed increased specific activities (by up to 100-fold) for around 50 primary aliphatic, unsaturated, branched, cyclic, benzylic and halogenated alcohols.
- Heath, Rachel S.,Birmingham, William R.,Thompson, Matthew P.,Taglieber, Andreas,Daviet, Laurent,Turner, Nicholas J.
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p. 276 - 281
(2019/01/04)
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- Aerobic oxidation of alcohols with air catalyzed by decacarbonyldimanganese
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The oxidation of alcohols to carbonyl compounds using air as the terminal oxidant is highly desirable. As described in previous reports, the abstraction of α-H of the alcohol is the most important step, and it typically requires not only a metal catalyst but also complex ligands, co-catalysts and bases. Herein, we report a practical and efficient method for the oxidation of primary alcohols, secondary alcohols, 1,2-diols, 1,2-amino alcohols, and other α-functionalized alcohols using a commercially available catalyst, Mn2(CO)10, and no additives. Preliminary mechanistic studies indicated that an alkoxyl radical intermediate existed in our system, and a plausible mechanism consistent with the experimental results and literature was proposed.
- Meng, Shan-Shui,Lin, Li-Rong,Luo, Xiang,Lv, Hao-Jun,Zhao, Jun-Ling,Chan, Albert S. C.
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supporting information
p. 6187 - 6193
(2019/11/20)
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- New thiosemicarbazide and dithiocarbazate based oxidovanadium(iv) and dioxidovanadium(v) complexes. Reactivity and catalytic potential
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The Schiff bases {H3dfmp-(smdt)2} (I), {H3dfmp-(sbdt)2} (II) and {H3dfmp-(tsc)2} (III) are synthesized by reaction of 2,6-diformyl-4-methylphenol (H3dfmp) and S-methyldithiocarbazate (smdt), S-benzyldithiocarbazate (sbdt) and thiosemicarbazide (tsc), respectively. Addition of [VIVO(acac)2] to solutions of these compounds in methanol leads to the formation of the oxidovanadium(iv) complexes [VIVO{Hdfmp-(smdt)2(CH3OH)}] (1), [VIVO{Hdfmp-(sbdt)2(CH3OH)}] (2) and [VIVO{Hdfmp-(tsc)2(CH3OH)}] (3). All these VIVO-compounds can be oxidized to the corresponding dioxidovanadium(v) (VVO2) complexes in methanolic solution upon aerial oxidation in the presence of KOH. The isolated compounds are K[VVO2{Hdfmp-(smdt)2}] (4), K[VVO2{Hdfmp-(sbdt)2}] (5) and K[VVO2{Hdfmp-(tsc)2}] (6). The Cs+ salts of these complexes i.e. Cs[VVO2{Hdfmp-(smdt)2}] (7), Cs[VVO2{Hdfmp-(sbdt)2}] (8) and Cs[VVO2{Hdfmp-(tsc)2}] (9) are prepared similarly in the presence of CsOH. All these compounds are characterized by various spectroscopic techniques like FT-IR, UV-visible, and 1H and 51V NMR and thermal studies. IR spectral data confirm the coordination of ligands through the azomethine nitrogen, the sulphur and the phenolic oxygen atoms to the metal. These complexes show excellent catalytic activity and selectivity for the oxidation of benzyl alcohol and ethylbenzene in the presence of H2O2 as an oxidant. Various parameters such as the amount of catalyst and oxidant, reaction time, reaction temperature and solvent were taken into consideration to optimize these catalytic oxidations. Compound 7 was also remarkably efficient and selective in the catalytic oxidation of primary and secondary alcohols to the corresponding aldehyde/ketone, as well as of several aromatic compounds such as toluene, benzene, cumene and tetralin.
- Maurya, Mannar R.,Sarkar, Bithika,Kumar, Amit,Ribeiro, Nádia,Miliute, Aistè,Pessoa, Jo?o Costa
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p. 17620 - 17635
(2019/11/25)
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- The Low Dimensional Co-Based Nanorods as a Novel Platform for Selective Hydrogenation of Cinnamaldehyde
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Abstract: Since hydrogenation of C=C bond in the cinnamaldehyde is thermodynamically favored, the selective hydrogenation of C=O group is challenging. Developing effective catalysts for this transformation has been hindered by the intrinsic disadvantages of traditional materials for decades. Hereby, we report the synthesis of the low dimensional Co based nanorods (NRs) as the effective platform for C=O groups hydrogenation in the conjugated compounds. The Pt/Co-NRs catalyst is simply fabricated by loading the Pt nano-particles (NPs) on the Co-NRs and the stability of the Co-NRs support is improved by coordination between the Pt NPs and the pyridinic N ring. Resorting to XRD, FT-IR, XPS, HRTEM, DTG-TG characterization methods, the catalytic mechanism for C=O bond hydrogenation has been proposed. The synergistic effects of K+ and OH? enhance the polarization of C=O group, leading to more adsorption of C=O groups on the Co-NRs so as to promote its hydrogenation performance. In the absence of spatial micropores in low dimensional Co based nanorods, the Pt/Co-NRs catalyst is more advantageous for mass transfer. Under optimal conditions, the conversion of cinnamaldehyde is 97.9% with 92.7% selectivity of cinnamyl alcohol within 3 h. In addition, the selectivity of cinnamyl alcohol changes slightly (only 2.4% fluctuations) after five recycle tests. Graphical Abstract: [Figure not available: see fulltext.].
- Yuan, Tao,Liu, Derong,Gu, Jianshan,Xia, Yongde,Pan, Yue,Xiong, Wei
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p. 2906 - 2915
(2019/04/30)
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- Production and testing of technical catalysts based on MnO2 for the abatement of aromatic volatile compounds at the laboratory and pilot plant scales
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Shaping is a crucial step to produce technical catalysts that remains as some sort of dark art for catalytic researchers in academia. This contribution discusses aspects concerning the fabrication of technical catalysts based on MnO2 powders ai
- Baldovino-Medrano, Víctor Gabriel,Kartheuser, Beno?t,Gaigneaux, Eric M.
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- Aerobic Oxidation of Secondary Alcohols with Nitric Acid and Iron(III) Chloride as Catalysts in Fluorinated Alcohol
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Fluorinated alcohols as solvents strongly influence and direct chemical reaction through donation of strong hydrogen bonds while being weak acceptors. We used 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as the activating solvent for a nitric acid and FeCl3-catalyzed aerobic oxidation of secondary alcohols to ketones. Reaction proceeded selectively with excellent yields with no reaction on the primary alcohol group. Oxidation of benzyl alcohols proceeds selectively to aldehydes with only HNO3 as the catalyst, while reaction on tertiary alcohols proceeds through dehydration and dimerization. A mechanistic study showed in situ formation of NOCl that converts alcohol into alkyl nitrite, which in the presence of Fe3+ ions and fluorinated alcohol decomposes into ketone. The study indicates that iron(III) acts also as the single-electron transfer catalyst in regeneration of NOCl reactive species.
- Mo?ina, ?tefan,Iskra, Jernej
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p. 14579 - 14586
(2019/11/14)
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- An On-Demand, Selective Hydrogenation Catalysis over Pt?Fe Nanocatalysts under Ambient Condition
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The selective hydrogenation of organic compounds with multiple unsaturated bonds is of significant for fine chemicals, while simultaneously achieving high selectivities of different potential products is still great challenge. Herein, we have successfully designed a nanocatalysis system, which can serve as a control switch of selective α, β-unsaturated aldehydes hydrogenation towards potential products in a highly on-demand fashion. We demonstrate that the PtFe nanospheres (NSs) represent excellent selectivity (>92.8 %) to unsaturated alcohols with high conversion (>99.7 %), due to the higher electron density of the active Pt atoms. When introducing AlCl3, the selectivity of saturated aldehydes enhances to 97.1 % at 95.8 % conversion, owing to synergy between PtFe NSs and AlCl3. Finally, the PtFe?A NSs generated by etching away the Fe can promote the selectivity saturated alcohols (>99.7 %) with the highest activity, on account of more exposed active sites after the chemical etching. Significantly, the developed nanocatalysis system can also exhibit high activity/selectivity for other typical α, β-unsaturated aldehydes as well as excellent stability after consecutive reactions. This work provides a guideline for the rational design highly active and selective Pt-based nanocatalyst.
- Yang, Chengyong,Bai, Shuxing,Feng, Yonggang,Huang, Xiaoqing
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p. 2265 - 2269
(2019/04/13)
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- Rhenium-Catalyzed Reduction of Carboxylic Acids with Hydrosilanes
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Re2(CO)10 efficiently catalyzes the direct reduction of various carboxylic acids under mild conditions (rt, irradiation 350 or 395 nm). While aliphatic carboxylic acids were readily converted to the corresponding disilylacetals with low catalyst loading (0.5 mol %) in the presence of Et3SiH (2.2 equiv), aromatic analogues required more drastic conditions (Re2(CO)10 5 mol %, Ph2MeSiH 4.0 equiv) to afford the corresponding aldehydes after acid treatment.
- Wei, Duo,Buhaibeh, Ruqaya,Canac, Yves,Sortais, Jean-Baptiste
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supporting information
p. 7713 - 7716
(2019/10/10)
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- Multicomponent Pt-Based Zigzag Nanowires as Selectivity Controllers for Selective Hydrogenation Reactions
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The selective hydrogenation of α, β-unsaturated aldehyde is an extremely important transformation, while developing efficient catalysts with desirable selectivity to highly value-added products is challenging, mainly due to the coexistence of two conjugated unsaturated functional groups. Herein, we report that a series of Pt-based zigzag nanowires (ZNWs) can be adopted as selectivity controllers for α, β-unsaturated aldehyde hydrogenation, where the excellent unsaturated alcohol (UOL) selectivity (>95%) and high saturated aldehyde (SA) selectivity (>94%) are achieved on PtFe ZNWs and PtFeNi ZNWs+AlCl3, respectively. The excellent UOL selectivity of PtFe ZNWs is attributed to the lower electron density of the surface Pt atoms, while the high SA selectivity of PtFeNi ZNWs+AlCl3 is due to synergy between PtFeNi ZNWs and AlCl3, highlighting the importance of Pt-based NWs with precisely controlled surface and composition for catalysis and beyond.
- Bai, Shuxing,Bu, Lingzheng,Shao, Qi,Zhu, Xing,Huang, Xiaoqing
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supporting information
p. 8384 - 8387
(2018/06/29)
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- Chemoselective flow hydrogenation of Α,Β – Unsaturated aldehyde with nano-nickel
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Herein, it is presented a novel catalytic system for the continuous-flow chemoselective hydrogenation of α,β – unsaturated aldehydes used in the production of high-value cosmetics and pharmaceuticals precursors. The reaction was catalyzed by nano-nickel particles grafted on polymeric support, synthesized via a simple, adaptable and green methodology. The system was highly active and very selective to C[dbnd]C bond saturation.
- Giziński, Damian,Goszewska, Ilona,Zieliński, Maciej,Lisovytskiy, Dmytro,Nikiforov, Kostiantyn,Masternak, Joanna,Zienkiewicz-Machnik, Ma?gorzata,?r?bowata, Anna,Sá, Jacinto
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- Highly efficient aqueous phase chemoselective hydrogenation of α,β-unsaturated aldehydes catalysed by phosphine-decorated polymer immobilized IL-stabilized PdNPs
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Phosphino-decorated polymer immobilised ionic liquid phase stabilised palladium nanoparticles (PdNP@PPh2-PIILP) and their PEGylated counterparts (PdNP@PPh2-PEGPIILP) are remarkably active and exceptionally selective catalysts for the aqueous phase hydrogenation of α,β-unsaturated aldehydes, ketones, esters and nitriles with PdNP@PPh2-PEGPIILP giving complete conversion and 100% selectivity for reduction of the CC bond, under mild conditions. This is the most selective PdNP-based system to be reported for the aqueous phase hydrogenation of this class of substrates.
- Doherty,Knight,Backhouse,Abood,Alshaikh,Fairlamb,Bourne,Chamberlain,Stones
-
supporting information
p. 1635 - 1641
(2017/06/05)
-
- Promotion effect of nickel for Cu–Ni/γ-Al2O3 catalysts in the transfer dehydrogenation of primary aliphatic alcohols
-
Cu–Ni/γ-Al2O3 bimetallic catalysts were developed for anaerobic dehydrogenation of non-activated primary aliphatic alcohols to aldehydes. Systematic investigation about the promotion effect of nickel on the catalytic performance was carried out. Hydrogenation of C=C bond rather than C=O bond, was significantly improved over Cu–Ni/γ-Al2O3 catalyst by introducing nickel, which interprets the good conversion of primary aliphatic alcohols. This work would contribute to design new catalysts for dehydrogenation of primary aliphatic alcohols.
- Yang, Xiaomei,Fu, Xiaomin,Bu, Ningning,Han, Li,Wang, Jianfeng,Song, Chengying,Su, Yunlai,Zhou, Lipeng,Lu, Tianliang
-
p. 111 - 119
(2017/01/05)
-
- SeO2-Mediated One-Pot Synthesis of 3-Cyanofurans from 3-Oxo-3-arylpropanenitriles and Substituted Acetaldehydes
-
An SeO2-mediated one-pot method was established for the synthesis of 3-cyanofurans from 3-oxo-3-arylpropanenitriles and substituted acetaldehydes. The generality of the reaction was explored, and a plausible mechanism is proposed.
- Zhou, Jie,Zhu, Xinhai,Huang, Manna,Wan, Yiqian
-
supporting information
p. 2317 - 2321
(2017/05/01)
-
- Sonochemical synthesis and DFT studies of nano novel Schiff base cadmium complexes: Green, efficient, recyclable catalysts and precursors of Cd NPs
-
Novel asymmetric (N4) Schiff bases (Ln, n = 1–3) and their nanosized cadmium complexes derived of 4,4'-(pentylazanediyl) dibenzaldehyde and aminobenzaldehyde are synthesized by sonochemical method and characterized based on physicochemical analysis including 1H NMR, 13C NMR, SEM, TGA, Mass, FT-IR, UV–Vis spectroscopy, elemental analysis, magnetic moment and molar conductance measurements. According to the analytic results of the NMR, UV–Vis and magnetic moment studies, it is found that the geometrical structures of these complexes [CdII2LnCl4], (L = C45H40N5X, X = CH3, Cl, OH) are square planer. The synthesized complexes were so effective as nanocatalyst on the oxidation of primary and secondary alcohols. The oxidation reactions were carried out in ethyl-methyl-imidazolium ionic liquid in presence of NaOCl. In addition Cd NPs were synthesized through the thermal decomposition of mentioned complexes and characterized by using FT-IR, SEM, TEM, EDX and XRD methods, which indicated close accordance to the standard pattern of CdO nanoparticles and an acceptable size at the nanorange (22–27 nm). Furthermore geometrical optimization of the Cd2LnCl4 calculated using DFT/B3LYP with LanL2DZ/6-311+G (d,p) level. The electronic parameter including HOMO–LUMO orbitals, bond gap, chemical hardness–softness, electronegativity, electrophilicity, NMR chemical shifts and IR frequencies were calculated. The calculated NMR shifts and vibrational frequencies showed excellent agreement with experimental data.
- Parsaee, Zohreh
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p. 644 - 659
(2017/06/20)
-
- Burgess Reagent Facilitated Alcohol Oxidations in DMSO
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The Burgess reagent ([methoxycarbonylsulfamoyl]triethylammonium hydroxide) has historically found utility as a dehydrating agent. Herein we show that, in the presence of dimethyl sulfoxide, the Burgess reagent efficiently and rapidly facilitates the oxidation of a broad range of primary and secondary alcohols to their corresponding aldehydes and ketones in excellent yields and under mild conditions, and can be combined with other transformations (e.g., Wittig olefinations). A mechanism similar to those described for the Pfitzner-Moffatt and Swern oxidations is proposed.
- Sultane, Prakash R.,Bielawski, Christopher W.
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p. 1046 - 1052
(2018/06/18)
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- PRODUCTION OF 2-SUBSTITUTED 4-METHYL-TETRAHYDROPYRANS FROM STARTING MATERIALS CONTAINING 2-ALKYL-4,4-DIMETHYL-1,3-DIOXANES
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The invention relates to a method for producing 2-substituted 4-methyltetrahydropyrans of general formula (I) from starting materials containing at least one 2-substituted 4,4-dimethyl-1,3-dioxane of general formula (II).
- -
-
Paragraph 0257
(2017/04/13)
-
- PRODUCTION OF 2-SUBSTITUTED 4-HYDROXY-4-METHYL-TETRAHYDROPYRANS FROM STARTING MATERIALS CONTAINING 2-ALKYL-4,4-DIMETHYL-1,3-DIOXANES
-
The present invention relates to a method for preparing 2-substituted 4-hydroxy-4-methyltetrahydropyrans from starting materials comprising at least one 2-alkyl-4,4-dimethyl-1,3-dioxane.
- -
-
Paragraph 0266
(2017/06/15)
-
- Method for producing aldehydes through olefin hydroformylation reaction
-
The invention relates to a method for producing aldehydes through an olefin hydroformylation reaction, and mainly solves the problems that in the prior art, olefins or olefins containing side-chain radicals are poor in reactivity, and a catalytic system is not stable under weak acidic conditions. The method for producing the aldehydes through the olefin hydroformylation reaction comprises the step that under the conditions that the temperature is 60-130 DEG C and the reaction pressure is 1.0-6.0 MPa, an aldehyde serves as a solvent, olefin hydroformylation is catalyzed with a rhodium compound, a phosphorus compound containing o-methyl and phenyl groups, a hard base pentavalent phosphorus-containing oxide and a bidentate phosphite ester compound to synthesize the aldehydes; according to the technical scheme, the olefin is at least one of isobutene, cis-2-butene, 2,5-dihydrofuran, 1-butene, propylene and ethylene, the problem is well solved, and the olefin can be used for the process of producing the aldehydes through the olefin hydroformylation reaction.
- -
-
Paragraph 0021; 0022; 0023; 0024; 0025; 0026; 0037-0052
(2017/04/03)
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- Method for synthesis of aldehydes by hydroformylation of alkenes on one same set of production equipment
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The invention relates to a method for synthesis of aldehydes by hydroformylation of alkenes on one same set of production equipment, and mainly aims to solve the problem of reaction activity decreasing and catalyst poisoning caused by cross of catalyst ligands in the switching process of different catalysts in the prior art. According to the method, at 60-130 DEG C under the reaction pressure of 1.0-6.0MPa in the switching process of different hydroformylation catalysts, a ruthenium compound is added, so that a rhodium compound, a phosphine compound and a bidentate phosphite composition can catalyze the hydroformylation for synthesis of different aldehydes; the alkenes are at least one of isobutene, cis-2-Butene, trans-2-Butene, 1-Butene, propylene and ethylene, by use of the method, the problem of reaction activity decreasing and catalyst poisoning can be well solved, and the method can be used for synthesis of the aldehydes by hydroformylation of the alkenes on one same set of production equipment.
- -
-
Paragraph 0024; 0025; 0026; 0027; 0028; 0029; 0036-0047
(2017/08/26)
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- Novel Schiff base Mn(III) and Co(II) complexes supported on Co nanoparticles: Efficient and recyclable magnetic nanocatalysts for alcohol oxidation
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In this study, efficient and highly selective heterogeneous catalysts were developed by immobilization of manganese and cobalt Schiff base complexes on Co magnetite nanoparticles (MNPs). Firstly, Co@SiO2 core-shell nanoparticles were synthesized through a one-pot reaction. Secondly, the Co@SiO2 was amino-functionalized using 3-aminopropyl triethoxysilane and then Schiff base ligand Co@SiO2[(EtO)3Si-L2] was obtained by the reaction of the amino-functionalized nanoparticles with the dialdehyde of 1,2-bis(2-formyl naphthoxy methyl)benzene. Finally, Co@SiO2[(EtO)3Si-L2]/M (M = Mn(iii) and Co(ii)) were successfully synthesized. These surface-modified nanoparticles were characterized using various techniques such as TEM, XRD, TGA, SEM, VSM, XPS, EDX and FT-IR. The catalytic activities of the prepared catalysts were investigated by employing them in the oxidation of various aromatic alcohols with an environmentally friendly oxidant under mild conditions. The catalysts can be readily recovered and reused in at least 5 consecutive cycles without significant leaching and loss their catalytic activity.
- Keypour, Hassan,Saremi, Shokoufeh Ghahri,Veisi, Hojat,Azadbakht, Reza
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p. 77020 - 77029
(2016/08/31)
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- Highly dispersible and magnetically recyclable poly(1-vinyl imidazole) brush coated magnetic nanoparticles: An effective support for the immobilization of palladium nanoparticles
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A heterogeneous recoverable catalyst was prepared via the complexation of palladium onto the surface of magnetic nanoparticles coated by a poly(1-vinyl imidazole) brush. The stable, active and reusable catalyst was proven to be highly active in aerobic oxidation of primary and secondary alcohols with excellent yields. Only 0.1 mol% of the catalyst was used to oxidize 1 mmol of primary and secondary alcohols. The catalyst was readily recovered and reused up to 10 times under the described reaction conditions without significant loss of activity.
- Pourjavadi, Ali,Safaie, Niloofar,Hosseini, Seyed Hassan,Bennett, Craig
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p. 1729 - 1736
(2016/02/19)
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- A polar reversibilities changing solvent used in the hydroformylation reaction of the isobutene
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The invention belongs to the field of chemical industry, relates to solvents with different polarities used in different steps of the chemical reaction process, and in particular relates to a polar reversible transformation solvent for an isobutylene hydroformylation reaction. According to the reaction, N,N-dimethyl cyclohexyl amine (CyNMe2) serves as a solvent for generating isovaleraldehyde in the isobutylene hydroformylation reaction, and the polarity of the CyNMe2 is increased in a production separation tower under the actions of water and CO2 so as to realize separation of the product from the solvent; in a solvent recycling tower, CyNMe2 is dissociated from the aqueous phase by virtue of the gas stripping action of inert gases such as N2, and the solvent is recovered so as to be recycled. The traditional solvent and product separation process needs to be finished by distillation, and therefore the problems such as high energy consumption, solvent volatilization and loss and the like are caused. By utilizing the polar reversible transformation properties of the solvent under the normal temperature and normal pressure conditions, the aims of separating the solvent from the product and recycling the solvent are achieved, the energy consumption is reduced, and the solvent loss is avoided.
- -
-
Paragraph 0017-0018
(2017/03/24)
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- Isoprene synthesis from formaldehyde and isobutene over Keggin-type heteropolyacids supported on silica
-
Gas phase Prins condensation of isobutene with formaldehyde has been studied over different Keggin-type heteropolyacids supported on amorphous silica. The catalysts were characterized by elemental analysis, X-ray diffraction, low temperature nitrogen adsorption, TPD of ammonia, FTIR of adsorbed pyridine and NMR spectroscopy. The activity of the supported heteropoly compounds was found to increase in the following order: H4SiMo12O40 3PMo12O40 4SiW12O40 ≈ H3PW12O40. The lower activity of the supported molybdenum heteropolyacids was attributed to their low thermal stability and partial decomposition during catalyst activation, which resulted in lower acidity. The variation of HPA content from 5 to 33 wt% was also shown to increase catalyst activity. Based on the relationship between the content of weak Br?nsted sites, the amount and type of carbonaceous deposits and the catalytic activity, it was concluded that the generation of working active sites over HPA catalysts involves the formation of unsaturated branched surface species over weak Br?nsted sites. These active carbonaceous species are responsible for selective isoprene synthesis. The best catalyst performance is observed over the catalyst with 20 wt% of H3PW12O40, which shows an isoprene yield of 48% with a selectivity of 63%.
- Sushkevich,Ordomsky,Ivanova
-
p. 6354 - 6364
(2016/08/18)
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- Method for preparing 3-methyl butyraldehyde from isobutylene
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The invention discloses a method for preparing 3-methyl butyraldehyde from isobutylene. According to the method, the isobutylene and synthesis gas are utilized as raw materials, acetylacetonatocarbonyltriphenylp hosphinerhodium(I) is utilized as the catalyst, triphenylphosphine is utilized as a ligan, and n-decane is utilized as a solvent, thereby performing a hydroformylation reaction. According to the method for preparing the 3-methyl butyraldehyde from the isobutylene, performances of the catalyst can be greatly exerted, the conversion rate of the isobutylene is high, and the selectivity of the isovaleraldehyde is high; and side reactions are a few, side products, such as pivaldehyde, isoamyl alcohol and the like, are not detected in products; furthermore, subsequent separation process for the products is simplified.
- -
-
Paragraph 0025
(2016/12/26)
-
- A novel Schiff base of Mn(III) complex supported on magnetic cobalt nanoparticles as a highly efficient retrievable heterogeneous catalyst in oxidation of alcohols and sulfides compounds
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Abstract A novel Schiff base Mn(III) complex was successfully synthesized and covalently immobilized on silica-coated magnetic cobalt nanoparticles as a support. The prepared heterogeneous catalyst showed a high catalytic activity in the oxidation of alcohols with high yield and in a milder conditions. The synthesized hybrid nanomaterials were fully characterized by FT-IR spectra, XRD and EDAX analysis. Morphology of the nanomaterials was determined by SEM and TEM. Also, the metallic magnetic cobalt and silica in the core-shell structure were determined by XPS analyses. The synthesized catalyst shows a high catalytic activity in the oxidation of alcohols and sulfides to the corresponding aldehydes and sulfoxides. Also the magnetic properties of the magnetic support and hybrid nanomaterials were measured by AGFM analysis.
- Judy Azar, Amir Reza,Safaei, Elham,Mohebbi, Sajjad
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p. 753 - 761
(2015/06/17)
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- 1H-pyrrole-2,4-dicarbonyl-derivatives and their use as flavoring agents
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The present invention primarily relates to 1H-pyrrole-2,4-dicarbonyl-derivatives of Formula (I) wherein R1, R2, R3, Z. Z' and J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) or of a mixture of compounds of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
- -
-
-
- Imidazo[1,2-a]pyridine-ylmethyl-derivatives and their use as flavoring agents
-
The present invention primarily relates to imidazo[1,2-a]pyridine-ylmethyl-derivatives of Formula (I) wherein R1, R2, X, W e J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
- -
-
-
- BISPHOSPHITE MIXTURE AND USE THEREOF AS A CATALYST MIXTURE IN HYDROFORMYLATION
-
The invention relates to a mixture of bisphosphites, to a process for preparation thereof, and to the reaction thereof with metals to give mixtures comprising complexes of the constitutionally isomeric bisphosphites and the metal, and to the use thereof as a catalytically active composition in hydroformylation reactions, and also to the hydroformylation reaction itself.
- -
-
Paragraph 0218; 0219
(2015/12/20)
-
- Importance of the Electron Correlation and Dispersion Corrections in Calculations Involving Enamines, Hemiaminals, and Aminals. Comparison of B3LYP, M06-2X, MP2, and CCSD Results with Experimental Data
-
While B3LYP, M06-2X, and MP2 calculations predict the δG° values for exchange equilibria between enamines and ketones with similar acceptable accuracy, the M06-2X/6-311+G(d,p) and MP2/6-311+G(d,p) methods are required for enamine formation reactions (for example, for enamine 5a, arising from 3-methylbutanal and pyrrolidine). Stronger disagreement was observed when calculated energies of hemiaminals (N,O-acetals) and aminals (N,N-acetals) were compared with experimental equilibrium constants, which are reported here for the first time. Although it is known that the B3LYP method does not provide a good description of the London dispersion forces, while M06-2X and MP2 may overestimate them, it is shown here how large the gaps are and that at least single-point calculations at the CCSD(T)/6-31+G(d) level should be used for these reaction intermediates; CCSD(T)/6-31+G(d) and CCSD(T)/6-311+G(d,p) calculations afford δG° values in some cases quite close to MP2/6-311+G(d,p) while in others closer to M06-2X/6-311+G(d,p). The effect of solvents is similarly predicted by the SMD, CPCM, and IEFPCM approaches (with energy differences below 1 kcal/mol).
- Castro-Alvarez, Alejandro,Carneros, Héctor,Sánchez, Dani,Vilarrasa, Jaume
-
p. 11977 - 11985
(2016/01/09)
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- METHOD FOR PRODUCING BRANCHED CHAIN ALDEHYDE
-
A method for producing a branched chain aldehyde, comprising: reacting an aliphatic olefin having a double bond at an end with carbon monoxide and hydrogen using an iodide of a Group 9 metal as a catalyst and at least one or more selected from the group consisting of hydrogen iodide and alkyl iodides as a promoter.
- -
-
Paragraph 0047; 0048; 0053
(2015/03/28)
-
- Acceleration of acetal hydrolysis by remote alkoxy groups: Evidence for electrostatic effects on the formation of oxocarbenium ions
-
In contrast to observations with carbohydrates, experiments with 4-alkoxy-substituted acetals indicate that an alkoxy group can accelerate acetal hydrolysis by up to 20-fold compared to substrates without an alkoxy group. The acceleration of ionization in more flexible acetals can be up to 200-fold when compensated for inductive effects.
- Garcia, Angie,Otte, Douglas A. L.,Sanzone, Jillian R.,Woerpel, K. A.,Salamant, Walter A.
-
supporting information
p. 3061 - 3064
(2015/05/05)
-
- Influence of Alkoxy Groups on Rates of Acetal Hydrolysis and Tosylate Solvolysis: Electrostatic Stabilization of Developing Oxocarbenium Ion Intermediates and Neighboring-Group Participation to Form Oxonium Ions
-
The hydrolysis of 4-alkoxy-substituted acetals was accelerated by about 20-fold compared to that of sterically comparable substrates that do not have an alkoxy group. Rate accelerations are largest when the two functional groups are linked by a flexible cyclic tether. When controlled for the inductive destabilization, an alkoxy group can accelerate acetal hydrolysis by up to 200-fold. The difference in rates of acetal hydrolysis between a substrate where the alkoxy group was tethered to the acetal group by a five-membered ring compared to one where it was tethered by an eight-membered ring was less than 100-fold, suggesting that fused-ring intermediates were not formed. By comparison, the difference in rates of solvolysis of structurally related tosylates were nearly 106-fold between the five- and eight-membered ring series. This observation implicates neighboring-group participation in the solvolysis of tosylates but not in the hydrolysis of acetals. The acceleration of acetal hydrolysis by an alkoxy group is better explained by electrostatic stabilization of intermediates that accumulate positive charge at the acetal carbon atom. (Chemical Presented).
- Garcia, Angie,Otte, Douglas A. L.,Salamant, Walter A.,Sanzone, Jillian R.,Woerpel
-
p. 4470 - 4480
(2015/05/13)
-
- Ozonolysis of a Series of Methylated Alkenes: Reaction Rate Coefficients and Gas-Phase Products
-
The gas-phase ozonolysis of three methylated alkenes, i.e., trans-2,2-dimethyl-3-hexene (22dM3H), trans-2,5-dimethyl-3-hexene (25dM3H), and 4-methyl-1-pentene (4M1P), has been investigated in the presence of sufficient hydroxyl radical scavenger in a laminar flow reactor at ambient temperature (296 ± 2 K) and P = 1 atm of dry air (RH ≤ 5%). Ozone levels in the reactor were monitored by an automatic analyzer. Alkene and gas-phase product concentrations were determined via online sampling either on three-bed adsorbent cartridges followed by thermodesorption and GC/FID-MS analysis or on 2,4-dinitrophenylhydrazine (DNPH) cartridges for subsequent HPLC/UV analysis. Reaction rate coefficients of (3.38 ± 0.12) × 10-17 for 22dM3H and (2.71 ± 0.26) × 10-17 for 25dM3H, both in cm3 molecule-1 s-1 units, have been obtained under pseudo-first-order conditions. Primary carbonyl products have been identified for the three investigated alkenes, and branching ratios are reported. In the case of 4M1P ozonolysis, the yield of a Criegee intermediate was indirectly determined. Kinetics and product study results are compared to those of literature when available. This work represents the first investigation of reaction products in the ozonolysis of 22dM3H, 25dM3H, and 4M1P in a flow reactor.
- Braure, Tristan,Riffault, Vronique,Tomas, Alexandre,Olariu, Romeo Iulian,Arsene, Cecilia,Bedjanian, Yuri,Coddeville, Patrice
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p. 596 - 605
(2015/08/06)
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- Chloral hydrate as a water carrier for the efficient deprotection of acetals, dithioacetals, and tetrahydropyranyl ethers in organic solvents
-
The efficient deprotection of several acetals, dithioacetals, and tetrahydropyranyl (THP) ethers under ambient conditions, using chloral hydrate in hexane, is described. Excellent yields were realized for a wide range of both aliphatic and aromatic substrates. The method is characterized by mild conditions (room temperatures or below), simple workup, and the ready availability of chloral hydrate. High chemoselectivity was also observed in the deprotection, acetonides, esters, and amides being unaffected under the reaction conditions. Products were generally purified chromatographically and identified spectrally. These results constitute a novel addition to current methodology involving a widely employed deprotection tactic in organic synthesis. It seems likely that the mechanism of the reaction involves adsorption of the substrate on the surface of the sparingly soluble chloral hydrate.
- Chandrasekhar, Sosale,Shrinidhi, Annadka
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p. 1904 - 1913
(2014/07/07)
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- 3,4-Dihydroisoquinolinium trichloroacetatochromate: A mild and effective new reagent for oxidation of alcohols to carbonyl compounds and arenes to their quinones
-
A new chromium(VI) reagent, 3,4-dihydroisoqinolinium trichloroacetatochromate was prepared by reacting trichloroacetic acid with CrO3in water. This reagent is suitable to oxidize various primary and secondary alcohols to the corresponding carbonyl compounds and anthracene to antraquinone in a good yields.
- Ozen, Recep
-
p. 6081 - 6083
(2015/02/19)
-
- A highly efficient and recyclable silica-supported palladium catalyst for alcohol oxidation reaction
-
A silica supported palladium catalyst (SiO2@APTES-Pd) showed excellent activity and reusability for selective oxidation of alcohols to corresponding carbonyl compounds with H2O2 as oxidant under base free environment. A wide range of alcohols including aliphatic alcohols are tolerated as substrates with a low loading of palladium (0.1 mol %).
- Sahu, Debojeet,Sarmah, Chandan,Das, Pankaj
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p. 3422 - 3425
(2014/06/09)
-
- An efficient and reusable vanadium based catalytic system for room temperature oxidation of alcohols to aldehydes and ketones
-
A simple and efficient vanadium based catalyst system for the oxidation of primary and secondary alcohols to aldehydes or ketones is reported using tert-butyl hydroperoxide as oxidizing agent and vanadyl sulfate as catalyst at room temperature. The versatility of the catalytic protocol is studied with wide variety of substrates.
- Sarmah, Gayatri,Bharadwaj, Saitanya K.,Dewan, Anindita,Gogoi, Ankur,Bora, Utpal
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p. 5029 - 5032
(2015/01/08)
-
- Palladium supported on magnetic core-shell nanoparticles: An efficient and reusable catalyst for the oxidation of alcohols into aldehydes and ketones by molecular oxygen
-
In continuing our efforts to develop economical and ecofriendly synthetic protocols, we present a proline-palladium catalyst supported on magnetic nanoparticles (0.5 mol %) for oxidation by molecular oxygen. The supported Pd catalyst shows high activity in the oxidation of alcohols into the corresponding carbonyl compounds where easy catalyst recovery and excellent recycling efficiency are observed. It is possible to recover and reuse the grafted palladium catalysts at least eight times without significant loss of its catalytic activity. Copyright
- Zhang, Lei,Li, Pinhua,Yang, Jin,Wang, Min,Wang, Lei
-
p. 217 - 222
(2014/03/21)
-
- Asymmetric α-oxyamination of aldehydes by synergistic catalysis of imidazolethiones and metal salts
-
Novel and efficient imidazolethione catalysts combined with metal salts were successfully introduced to the asymmetric α-oxyamination of aldehydes. The desired products with high yields and good to excellent enantioselectivities were obtained via a one-pot oxidation-oxyamination reaction system.
- Liang, Xianrui,Li, Na,Chen, Xinlei,Su, Weike
-
p. 44039 - 44042
(2014/12/11)
-
- Dehydrogenation of primary aliphatic alcohols to aldehydes over Cu-Ni bimetallic catalysts
-
The catalytic conversion of non-activated primary aliphatic alcohols to aldehydes is a challenge, and monometallic Cu-based catalysts loaded on different supports have often been used for these reactions. Cu-Ni/γ-Al2O3 bimetallic catalysts were prepared and used for anaerobic dehydrogenation of 3,3-dimethyl-1-butanol to 3,3-dimethyl-1-butanal. These catalysts exhibited higher activity than Cu/γ-Al2O3 under the same reaction conditions, and a wide range of primary aliphatic alcohols were efficiently converted to the corresponding aldehydes over Cu-Ni/γ-Al2O3 under mild conditions.
- Lu, Tianliang,Du, Zhongtian,Liu, Junxia,Chen, Chen,Xu, Jie
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p. 1911 - 1916
(2015/09/28)
-
