- Hafnium inspired activation of highly hindered anhydrides in the acylation of alcohols and polyols
-
A novel and highly efficient method for activating highly hindered acid anhydrides towards the acylation of alcohols and carbohydrate-derived polyols has been developed. This new method relies on the capacity of the hafnium triflate catalyst Hf(OTf)2 to activate highly hindered acid anhydrides, and to direct the acylation reaction. This new acylation protocol is mild and proceed at room temperature with low catalyst loading. The method is versatile and has been extended to different alcohol substrates with different steric encumbrance as well as carbohydrate-derived polyols to afford the corresponding ester products in good to excellent yields.
- Mensah, Enoch,Day, Aaron,Thomas, Raven
-
-
Read Online
- Mixed Imidazolin-2-iminato-Cp? Thorium(IV) Complexes: Synthesis and Reactivity Toward Oxygen-Containing Substrates
-
The mixed pentamethylcyclopentadienyl thorium(IV) imidazolin-2-iminato complexes Cp?2Th(ImDippN)(Me) (2) and Cp?2Th(ImMesN)(Me) (3) were synthesized in quantitative yields via rapid protonolysis of Cp?2Th(Me)2 (1) with the respective neutral imidazolin-2-iminato ligand ImRNH. Cp?2Th(ImDippN)(Me) (2) and Cp?2Th(ImMesN)(Me) (3) display short Th-N bond lengths and large Th-N-C angles. The reactivity of complex 2 and 3 toward oxygen-containing substrates was studied, and the catalytic activity of 2 was compared to the dimethyl (bispentamethyl-cyclopentadienyl) thorium complex 1. Complex 2 was applied in the catalytic Tishchenko reaction with aromatic, heteroaromatic, and branched aliphatic aldehydes, displaying a higher catalytic activity than Cp?2Th(Me)2 and Cp?2Th(ImMesN)(Me). Furthermore, 2 was applied as a catalyst in the crossed Tishchenko reaction and in the oligomerization of bis(aldehydes), as well as in the ring-opening polymerization of ε-caprolactone. In all reactions, the activity of Cp?2Th(ImDippN)(Me) (2) and Cp?2Th(ImMesN)(Me) (3) was higher than that observed for Cp?2Th(Me)2 (1), which can be attributed to the increased electron density introduced by the coordination of the imidazolin-2-iminato ligand. (Chemical Equation Presented).
- Karmel, Isabell S. R.,Fridman, Natalia,Tamm, Matthias,Eisen, Moris S.
-
-
Read Online
- Thorium complexes possessing expanded ring N-heterocyclic iminato ligands: Synthesis and applications
-
Six and seven membered N-heterocyclic iminato ligands (L) are introduced allowing access a new class of Th(iv) complexes of the type Cp?2Th(L)(CH3). These complexes were studied in the Tishchenko reaction. Stoichiometric reactions together with kinetic and thermodynamic studies permit us to propose a plausible mechanism.
- Ghatak, Tapas,Drucker, Shani,Fridman, Natalia,Eisen, Moris S.
-
-
Read Online
- Pd/C-catalyzed chemoselective hydrogenation in the presence of diphenylsulfide
-
A Pd/C-catalyzed chemoselective hydrogenation using diphenylsulfide as a catalyst poison has been developed. This methodology selectively hydrogenates olefin and acetylene functionalities without hydrogenolysis of aromatic carbonyls and halogens, benzyl esters, and N-Cbz protective groups.
- Mori, Akinori,Miyakawa, Yumi,Ohashi, Eri,Haga, Tomoko,Maegawa, Tomohiro,Sajiki, Hironao
-
-
Read Online
- Development of a practical and scalable preparation using sonication of Pd/fibroin catalyst for chemoselective hydrogenation
-
A practical and efficient preparation method of palladium-fibroin (Pd/Fib), silk-fibroin-supported Pd(0) by means of sonication, has been developed. The Pd/Fib catalyst could be prepared within 12 h at room temperature starting from commercial silk-fibroin and Pd(OAc)2 in MeOH, whereas our previous preparation method required at least 4 days. The present improved process is applicable to a large-scale preparation of Pd/Fib. The Pd/Fib prepared by the present method also catalyzed chemoselective hydrogenation of acetylenes, olefins, and azides in the presence of aromatic ketones, aldehydes, and halides; N-Cbz protective groups; and benzyl esters, which are readily hydrogenated under the Pd/C- or Pd/C(en)-catalyzed hydrogenation conditions. Copyright Taylor & Francis Group, LLC.
- Kitamura, Yoshiaki,Tanaka, Asami,Sato, Mutsumi,Oono, Keiji,Ikawa, Takashi,Maegawa, Tomohiro,Monguchi, Yasunari,Sajiki, Hironao
-
-
Read Online
- Novel palladium-on-carbon/diphenyl sulfide complex for chemoselective hydrogenation: Preparation, characterization, and application
-
A diphenyl sulfide immobilized on palladium-on-carbon system, Pd/C[Ph 2S], was developed to achieve the highly chemoselective hydrogenation of alkenes, acetylenes, azides, and nitro groups in the presence of aromatic ketones, halides, benzyl esters, and N-Cbz protective groups. Instrumental analyses of the heterogeneous catalyst demonstrated that diphenylsul fide was embedded on Pd/C via coordination of its sulfur atom to palladium metal or physical interaction with graphite layers of the activated carbon. The catalyst could be recovered and reused at least five times without any significant loss of the reactivity.
- Mori, Akinori,Mizusaki, Tomoteru,Kawase, Masami,Maegawa, Tomohiro,Monguchi, Yasunari,Takao, Shinobu,Takagi, Yukio,Sajikia, Hironao
-
-
Read Online
- Steric effects in the uncatalyzed and DMAP-catalyzed acylation of alcohols - Quantifying the window of opportunity in kinetic resolution experiments
-
The kinetics of the reaction of several alcohols (benzyl alcohol, ethanol, 1-phenylethanol, cyclohexanol, and 1-methyl-1-phenylethanol) with a selection of anhydrides (acetic anyhydride, propionic anhydride, isobutyric anhydride, isovaleric anhydride, and pivalic anhydride) as catalyzed by 4-(N,N-dimethylamino)pyridine (DMAP)/triethyl amine have been studied in CH 2Cl2 at 20°C. In all cases the reaction kinetics can be described by rate laws containing a DMAP-catalyzed term and an uncatalyzed (back-ground) term. The rate constants for the background reaction respond sensi tively to changes in the steric demand of the alcohol and the anhydride substrates, making the reaction of cyclohexanol with acetic anhydride 526 times faster than the reaction with pivalic anhydride. Steric effects are even larger for the catalyzed reaction and the reactivity difference between acetic and pivalic anhydride exceeds a factor of 8000 for the reaction of cyclohexa nol. There is, however, no linear correlation between the steric effects on the catalyzed and the uncatalyzed part. As a consequence there are substrate combinations with dominating catalytic terms (such as the reaction of benzyl alcohol with isobutyric anhydride), while other substrate combinations (such as the reaction of cyclohexanol with pivalic anhydride) are characterized through a dominating background process. The implications of these findings for the kinetic resolution of alcohols are discussed.
- Fischer, Christian B.,Xu, Shangjie,Zipse, Hendrik
-
-
Read Online
- Novel Template Effects of Distannoxane Catalysts in Highly Efficient Transesterification and Esterification
-
The transesterification of carboxylic esters and the esterification of carboxylic acids are effected under mild conditions under catalysis by 1,3-disubstituted tetraalkyldistannoxanes 1.Various functional groups remain unaffected and otherwise difficult to obtain esters are accessible.An ester bearing a tertiary butyl group in the carboxylic acid moiety remained unchanged in competition experiments with a less bulky ester, which undergoes transesterification quantitatively.The unique features of the reactions are attributable to the template effects of the dimeric structure of 1.The facility with which compounds 1 can be converted into alkoxystannoxanes 2 and the synergistic effect of the proximate tin atoms of 2 play key roles in permitting smooth reactions and high selectivity.Another notable feature of compounds 1 is their unusually high solubility in organic solvents, even though the compounds have a metaloxane core as a major skeletal part.The double-layered structure of 1, in which the inorganic moiety is surrounded by eight alkyl groups, permits esterification to be driven to completion simply by heating a mixture of the carboxylic acid and the alcohol.The distannoxane-catalyzed esterification is irreversible, and thus, no hydrolysis of the product esters occurs when compounds 1 are used as catalysts.
- Otera, Junzo,Dan-oh, Nobushisa,Nozaki, Hitosi
-
-
Read Online
- Reductive esterification of aromatic aldehydes using Zn/Ac 2O/imidazole or Zn/Yb(OTf)3/(RCO)2O system
-
Benzaldehydes are reduced by metallic zinc in the presence of Ac 2O and imidazole, giving the corresponding benzyl acetates in good yields. Reductive esterification of aromatic aldehydes is also carried out via gem-diacetoxy compounds. Carbonyl compounds are readily converted to the gem-diacyloxy compounds in excellent yields on treatment with 2molar amounts of acid anhydride and 10mol% of Yb(OTf)3 in MeCN at room temperature. Thus-formed diacyloxy compounds derived from aromatic aldehydes are reduced in situ by metallic zinc to afford the corresponding esters.
- Hirao, Toshikazu,Santhitikul, Sirida,Takeuchi, Hiroki,Ogawa, Akiya,Sakurai, Hidehiro
-
-
Read Online
- Sol-gel derived LaFeO3/SiO2 nanocomposite: Synthesis, characterization and its application as a new, green and recoverable heterogeneous catalyst for the efficient acetylation of amines, alcohols and phenols
-
LaFeO3/SiO2 nanocomposite was synthesized by the sol-gel process from metal nitrates and tetraethyl orthosilicate (TEOS) as the SiO2 source. The nanocomposite product was characterized by XRD, FT-IR, SEM, and surface area measurements and was used as a heterogeneous catalyst for the efficient acetylation of amines, alcohols and phenols to the corresponding acetates using acetic anhydride under solvent-free conditions. Among the various substrates, acetylation of amines was preceded rapidly, so that an amine group could be selectively acetylated in the presence of alcoholic or phenolic hydroxyl groups by the appropriate choice of reaction time. The catalyst can also be reused several times without the loss of activity. In addition, the catalytic activity of the LaFeO3/SiO2 nanocomposite was higher than that of the pure LaFeO3 nanoparticles. The method is high yielding, clean, cost effective, compatible with the substrates having other functional groups and very suitable for the practical organic synthesis.
- Farhadi, Saeed,Jahanara, Kosar,Sepahdar, Asma
-
-
Read Online
- Reusable and efficient polyvinylpolypyrrolidone-supported triflic acid catalyst for acylation of alcohols, phenols, amines, and thiols under solvent-free conditions
-
Abstract: A triflic acid-functionalized polyvinylpolypyrrolidone was prepared and fully characterized by FT-IR, TGA, and SEM. This super acidic solid catalyst shows high catalytic activity for selective acylation of alcohols, phenols, amines, and thiols with anhydrides under solvent-free conditions at room temperature. In addition, this method features an easy to handle solid super acid catalyst and an operationally simple procedure, affording the desired acylated products in excellent yields. Graphical abstract: [Figure not available: see fulltext.].
- Tajbakhsh, Mahgol,Tajbakhsh, Mahmoud,Khaksar, Samad,Gazvini, Helia Janatian,Heidary, Marzieh
-
-
Read Online
- PH-Responsive Pickering emulsion stabilized by polymer-coated silica nanoaggregates and applied to recyclable interfacial catalysis
-
We first synthesized a diblock copolymer poly[tert-butyl methacrylate]-b-poly[3-(trimethoxysilyl)propyl methacrylate] (PtBMA-b-PTMSPMA) through reversible addition-fragmentation chain transfer (RAFT) living radical polymerization and grafted it onto fumed silica by converting the PTMSPMA segment to silanol and the PtBMA segment to polymethylacrylic acid (PMAA) in the presence of trifluoroacetic acid in order to obtain PMAA brush-coated silica nanoaggregates P-Si. TEM, DLS, FTIR, and TGA results confirmed the successful modification of the starting materials. The nanoaggregates flocculated and stabilized a toluene-in-water Pickering emulsion at low pH, while the nanoaggregates were well dispersed in water and broke the emulsion under both neutral and basic conditions. Alternatively, the addition of acid/base induced emulsification/demulsification cycles that were sustained for several cycles. Moreover, when the P-Si was mixed with Rh-loaded silica, Rh-Si, the mixture had the same pH-responsive Pickering emulsion behavior as the single P-Si. This Pickering emulsion system can be used in the biphasic interfacial catalytic hydrogenation of olefins and had excellent yields under a hydrogen atmosphere. The yield of Pickering emulsion catalysis rapidly reached more than 99% in 3 h, while that of the demulsified mixture failed to reach 20% in 4 h, which verified the promotion of catalysis by the Pickering emulsion. Base-induced demulsification can be used to separate the products and recycle the catalyst. This pH-responsive Pickering emulsion catalytic system was capable of several cycles of reuse, and there was no significant decrease in catalytic efficiency even after eight cycles. This journal is
- Dong, Jinfeng,Luo, Ruidong,Luo, Yunbai
-
-
Read Online
- Markedly chemoselective hydrogenation with retention of benzyl ester and N-Cbz functions using a heterogeneous Pd-fibroin catalyst
-
The chemoselective catalytic hydrogenation of acetylene, olefin and azido derivatives bearing benzyl ester and N-Cbz functionalities using a Pd-fibroin (Pd/Fib) catalyst was investigated. Perfect selectivity was accomplished, and the benzyl ester and N-Cbz functionalities are tolerated under the reaction conditions.
- Sajiki, Hironao,Ikawa, Takashi,Hirota, Kosaku
-
-
Read Online
- H6GeMo10V2O40·16H 2O nanoparticles prepared by hydrothermal method: A new and reusable heteropoly acid catalyst for highly efficient acetylation of alcohols and phenols under solvent-free conditions
-
A new Keggin-type heteropoly acid, namely decamolybdodivanadogermanic acid (H6GeMo10V2O40·16H 2O), with nanosized particles (5-8 nm), has been synthesized by a hydrothermal method and characterized by elemental analysis, thermogravimetric analysis (TGA), powder X-ray diffractometry (XRD), Fourier-transform infrared spectroscopy (FTIR), UV-Visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and potentiometric titration. H6GeMo10V2O40·16H 2O revealed high catalytic activity for acetylation of various alcohols and phenols with acetic anhydride at room temperature (298 ± 2 K) and under solvent-free conditions. The catalyst can be easily recovered and used repeatedly for five cycles with a slight loss of activity. The catalytic activity of H6GeMo10V2O40· 16H2O was higher than that of other Keggin-type heteropoly acids, such as H3PW12O40, H3PMo 12O40 and H4SiW12O40.
- Farhadi, Saeid,Zareisahamieh, Reza,Zaidi, Masoumeh
-
-
Read Online
- N-Heterocyclic Carbene/Carboxylic Acid Co-Catalysis Enables Oxidative Esterification of Demanding Aldehydes/Enals, at Low Catalyst Loading
-
We report the discovery that simple carboxylic acids, such as benzoic acid, boost the activity of N-heterocyclic carbene (NHC) catalysts in the oxidative esterification of aldehydes. A simple and efficient protocol for the transformation of a wide range of sterically hindered α- and β-substituted aliphatic aldehydes/enals, catalyzed by a novel and readily accessible N-Mes-/N-2,4,6-trichlorophenyl 1,2,4-triazolium salt, and benzoic acid as co-catalyst, was developed. A whole series of α/β-substituted aliphatic aldehydes/enals hitherto not amenable to NHC-catalyzed esterification could be reacted at typical catalyst loadings of 0.02–1.0 mol %. For benzaldehyde, even 0.005 mol % of NHC catalyst proved sufficient: the lowest value ever achieved in NHC catalysis. Preliminary studies point to carboxylic acid-induced acceleration of acyl transfer from azolium enolate intermediates as the mechanistic basis of the observed effect.
- Berkessel, Albrecht,Biswas, Animesh,Harnying, Wacharee,Sudkaow, Panyapon
-
supporting information
p. 19631 - 19636
(2021/08/09)
-
- Insight into the Mechanism of the Acylation of Alcohols with Acid Anhydrides Catalyzed by Phosphoric Acid Derivatives
-
Insight into the mechanism of a safe, simple, and inexpensive phosphoric acid (H3PO4)-catalyzed acylation of alcohols with acid anhydrides is described. The corresponding in situ-generated diacylated mixed anhydrides, unlike traditionally proposed monoacylated mixed anhydrides, are proposed as the active species. In particular, the diacylated mixed anhydrides act as efficient catalytic acyl transfer reagents rather than as Br?nsted acid catalysts simply activating acid anhydrides. Remarkably, highly efficient phosphoric acid (1-3 mol %)-catalyzed acylation of alcohols with acid anhydrides was achieved and a 23 g scale synthesis of an ester was demonstrated. Also, phosphoric acid catalyst was effective for synthetically useful esterification from carboxylic acids, alcohols, and acid anhydride. Moreover, with regard to recent developments in chiral 1,1′-bi-2-naphthol (BINOL)-derived phosphoric acid diester catalysts toward asymmetric kinetic resolution of alcohols by acylation, some phosphate diesters were examined. As a result, a 31P NMR study and a kinetics study strongly supported not only the acid-base cooperative mechanism as previously proposed by other researchers but also the mixed anhydride mechanism as presently proposed by us.
- Hayashi, Hiroyuki,Yasukochi, Shotaro,Sakamoto, Tatsuhiro,Hatano, Manabu,Ishihara, Kazuaki
-
supporting information
p. 5197 - 5212
(2021/04/12)
-
- Iridium-Catalyzed Alkene-Selective Transfer Hydrogenation with 1,4-Dioxane as Hydrogen Donor
-
The iridium-catalyzed transfer hydrogenation of alkenes using 1,4-dioxane as a hydrogen donor is described. The use of 1,2-bis(dicyclohexylphosphino)ethane (DCyPE), featuring bulky and highly electron-donating properties, led to high catalytic activity. A polystyrene-cross-linking bisphosphine PS-DPPBz produced a reusable heterogeneous catalyst. These homogeneous and heterogeneous protocols achieved chemoselective transfer hydrogenation of alkenes over other potentially reducible functional groups such as carbonyl, nitro, cyano, and imino groups in the same molecule.
- Zhang, Deliang,Iwai, Tomohiro,Sawamura, Masaya
-
supporting information
p. 5867 - 5872
(2019/08/26)
-
- Synthesis, characterization and catalytic performances of benzimidazolin-2-iminato actinide (IV) complexes in the Tishchenko reactions for symmetrical and unsymmetrical esters
-
A new family of benzimdazolin-2-iminato actinide?(IV) complexes [(Bim7-MeDipp/MeN)An(N(SiMe3)2)3] (An = U (3), Th (4)) and [(Bim4-MeDipp/MeN)An(N(SiMe3)2)3] (An = U (5), Th (6)) were synthesized and their solid state structures were established by single-crystal X-ray diffraction analysis. The catalytic performances of complexes 3–6 towards the homo- and cross-coupling of aldehydes (Tishchenko reaction) were studied and the thorium complexes 4 and 6 displayed moderate to high activities for the production of the corresponding symmetric and unsymmetrical esters. Coupling of aldehyde and alcohols, known as the tandem proton-transfer esterification, and the intermolecular coupling reaction between aldehyde and trifluoromethylketones were also investigated by these thorium complexes, indicating a complementary method to obtain unsymmetrical esters selectively. Plausible mechanisms for these reactions are proposed based on stoichiometric studies.
- Liu, Heng,Khononov, Maxim,Fridman, Natalia,Tamm, Matthias,Eisen, Moris S.
-
p. 123 - 137
(2017/10/25)
-
- Domino Methylenation/Hydrogenation of Aldehydes and Ketones by Combining Matsubara's Reagent and Wilkinson's Catalyst
-
The methylenation/hydrogenation cascade reaction of aldehydes or ketones through a domino process involving two ensuing steps in a single pot is realized. The compatibility of Matsubara's reagent and Wilkinson's complex give a combination that allows, under dihydrogen, the transformation of a carbonyl function into a methyl group. This new method is suitable to introduce an ethyl motif from aromatic and aliphatic aldehydes with total chemoselectivity and total retention of α-stereochemical purity. The developed procedure is also extended to the introduction of methyl groups from ketones.
- Maazaoui, Radhouan,Pin-Nó, María,Gervais, Kevin,Abderrahim, Raoudha,Ferreira, Franck,Perez-Luna, Alejandro,Chemla, Fabrice,Jackowski, Olivier
-
supporting information
p. 5732 - 5737
(2016/12/14)
-
- The scope and mechanism of palladium-catalysed Markovnikov alkoxycarbonylation of alkenes
-
Hydroesterification reactions represent a fundamental type of carbonylation reaction and constitute one of the most important industrial applications of homogeneous catalysis. Over the past 70 years, numerous catalyst systems have been developed that allow for highly linear-selective (anti-Markovnikov) reactions and are used in industry to produce linear carboxylates starting from olefins. In contrast, a general catalyst system for Markovnikov-selective alkoxycarbonylation of aliphatic olefins remains unknown. In this paper, we show that a specific palladium catalyst system consisting of PdX2/N-phenylpyrrole phosphine (X, halide) catalyses the alkoxycarbonylation of various alkenes to give the branched esters in high selectivity (branched selectivity up to 91%). The observed (and unexpected) selectivity has been rationalized by density functional theory computation that includes a dispersion correction.
- Li, Haoquan,Dong, Kaiwu,Jiao, Haijun,Neumann, Helfried,Jackstell, Ralf,Beller, Matthias
-
p. 1159 - 1166
(2016/11/28)
-
- Kinetic resolution of α-Methylene- β- Hydroxy esters catalyzed by Acyl transfer catalyst An -PIQ
-
A highly efficient nonenzymatic kinetic resolution of a series of structurally diverse racemic α-methylene-β-hydroxy esters utilizing the acyl transfer catalyst An-PIQ and propionic anhydride is reported. This procedure provides recovered alcohols with extremely high ee's (up to >99%) in reasonable conversions and excellent selectivity factors (S up to 108). Several synthetically important substrates were resolved in gram-scale reactions, and highly optically pure α-methylene-β-hydroxy esters were obtained with excellent S values and good yields.
- Jiang, Shan-Shan,Xu, Qin-Chang,Zhu, Ming-Yu,Yu, Xingxin,Deng, Wei-Ping
-
p. 3159 - 3169
(2015/03/30)
-
- ZnAl2O4@SiO2 nanocomposite catalyst for the acetylation of alcohols, phenols and amines with acetic anhydride under solvent-free conditions
-
A ZnAl2O4@SiO2 nanocomposite was prepared from metal nitrates and tetraethyl orthosilicate by the sol-gel process, and characterized by X-ray diffraction, Fourier transform infrared, transmission electron microscopy, and N2 adsorption-desorption measurements. The nanocomposite was tested as a heterogeneous catalyst for the acetylation of alcohols, phenols, and amines under solvent-free conditions. Under optimized conditions, efficient acetylation of these substrates with acetic anhydride over the ZnAl2O4@SiO2 nanocomposite was obtained. Acetylation of anilines and primary aliphatic amines proceeded rapidly at room temperature, while the reaction time was longer for the acetylation of alcohols and phenols, showing that an amine NH2 group can be selectively acetylated in the presence of alcoholic or phenolic OH groups. The catalyst can be reused without obvious loss of catalytic activity. The catalytic activity of the ZnAl2O4@SiO2 nanocomposite was higher than that of pure ZnAl2O4. The method gives high yields, and is clean, cost effective, compatible with substrates having other functional groups and it is suitable for practical organic synthesis.
- Farhadi, Saeed,Jahanara, Kosar
-
p. 368 - 375
(2014/04/03)
-
- Aniline mediated oxidative C-C bond cleavage of α-alkoxy aldehydes in air and a model reaction for the synthesis of α-(d)-amino acid derivatives
-
A metal-free and 4-methyl aniline mediated method for the oxidative C-C bond cleavage has been developed. The reaction proceeds in air using molecular oxygen as the oxidant, affording one-carbon shortened esters in moderate to good yields within a short time. Moreover, it provides a model reaction for the highly enantioselective synthesis of (d)-serine esters by combining with a l-proline catalyzed Mannich reaction.
- Hu, Bin,Li, Yunfeng,Li, Zhongjun,Meng, Xiangbao
-
supporting information
p. 4138 - 4141
(2013/07/05)
-
- Fluorous 4-N,N-dimethylaminopyridium iodide: Recyclable organocatalysts by precipitation for acylation reaction at room temperature
-
A novel fluorous DMAP quaternary ammonium iodide salt organocatalyst was prepared. This fluorous organocatalyst was successfully employed to the acylation reaction at room temperature without the use of a stoichiometric amount of external base. It could be recovered 3 times from the reaction mixture by simple precipitation with excellent purity for direct reuse.
- Yi, Wen-Bin,Zhu, Yi-Wei,Cai, Chun
-
-
- Chemoselective hydrogenation catalyzed by Pd on spherical carbon
-
We have developed a highly chemoselective hydrogenation method using a novel palladium catalyst supported on spherical carbon (0.5 % Pd/SC). The 0.5 % Pd/SC exhibited a novel catalytic activity and could achieve the chemoselective hydrogenation of alkynes, alkenes, azides, nitro groups, and aliphatic O-tert-butyldimethylsilyl (TBS) ethers without hydrogenolysis of benzyl esters, benzyl ethers, nitriles, aromatic ketones, N-carbobenzyloxy (N-Cbz) protective groups, and aromatic O-TBS ethers. Highly selective spheres: The chemoselective hydrogenation of C-C multiple bonds, azides, nitro groups, and aliphatic O-tert-butyldimethylsilyl (TBS) ethers is achieved in the presence of benzyl esters, benzyl ethers, nitriles, aromatic ketones, N-carbobenzyloxy (Cbz) protective groups, and aromatic O-TBS ethers by a novel heterogeneous palladium catalyst supported on spherical carbon (0.5 % Pd/SC). Copyright
- Esaki, Hiroyoshi,Hattori, Tomohiro,Tsubone, Aya,Mibayashi, Satoko,Sakata, Takao,Sawama, Yoshinari,Monguchi, Yasunari,Yasuda, Hidehiro,Nosaka, Kazuto,Sajiki, Hironao
-
p. 3629 - 3635
(2014/01/06)
-
- Chemoselective hydrogenation using molecular sieves-supported Pd catalysts: Pd/MS3A and Pd/MS5A
-
Palladium catalysts embedded on molecular sieves (MS3A and MS5A) were prepared by the adsorption of Pd(OAc)2 onto molecular sieves with its in situ reduction to Pd0 by MeOH as a reducing agent and solvent. 0.5% Pd/MS3A and 0.5% Pd/MS5A catalyzed the hydrogenation of alkynes, alkenes, and azides with a variety of coexisting reducible functionalities, such as nitro group, intact. It is noteworthy that terminal alkenes of styrene derivatives possessing electron-donating functionalities on the benzene nucleus were never hydrogenated under 0.5% Pd/MS5A-catalyzed conditions, while internal alkenes of 1-propenylbenzene derivatives were readily reduced to the corresponding alkanes.
- Takahashi, Tohru,Yoshimura, Masatoshi,Suzuka, Hiroyasu,Maegawa, Tomohiro,Sawama, Yoshinari,Monguchi, Yasunari,Sajiki, Hironao
-
experimental part
p. 8293 - 8299
(2012/09/21)
-
- One-step transformation of tetrahydropyranyl ethers using indium(III) triflate as the catalyst
-
A convergent one-step transformation of tetrahydropyranyl (THP) ethers is described. According to our earlier experiments, indium(III) triflate has proven to be an efficient catalyst for the transformation of THP ethers into their corresponding acetates.
- Mineno, Tomoko,Nikaido, Nana,Kansui, Hisao
-
scheme or table
p. 1167 - 1170
(2010/03/31)
-
- Development of molecular sieves-supported palladium catalyst and chemoselective hydrogenation of unsaturated bonds in the presence of nitro groups
-
The chemoselective hydrogenation of unsaturated bonds and azide functionalities is achieved in the presence of nitro groups by a heterogeneous palladium catalyst supported on molecular sieves (MS3A). The present method shows a widerange of applicability with regard to substrates and the catalyst can be easily prepared and reused at least three times without any loss of activity.
- Maegawa, Tomohiro,Takahashi, Tohru,Yoshimura, Masatoshi,Suzuka, Hiroyasu,Monguchi, Yasunari,Sajiki, Hironao
-
supporting information; experimental part
p. 2091 - 2095
(2009/12/26)
-
- Erbium(III) chloride: A very active acylation catalyst
-
Erbium(iii) chloride is a powerful catalyst for the acylation of alcohols and phenols. The reaction works well for a large variety of simple and functionalized substrates by using different kinds of acidic anhydrides (Ac 2O, (EtCO)2O, (PriCO)2O, (Bu tCO)2O, and (CF3CO)2), without isomerization of chiral centres. Moreover, the catalyst can be easily recycled and reused without significant loss of activity. CSIRO 2007.
- Dalpozzo, Renato,De Nino, Antonio,Maiuolo, Loredana,Oliverio, Manuela,Procopio, Antonio,Russo, Beatrice,Tocci, Amedeo
-
-
- Chemoselective hydrogenation method catalyzed by Pd/C using diphenylsulfide as a reasonable catalyst poison
-
While Pd/C is one of the most useful catalysts for hydrogenation, the high catalyst activity of Pd/C causes difficulty in its application to chemoselective hydrogenation between different types of reducible functionalities. In order to achieve chemoselective hydrogenation using Pd/C, we investigated catalyst poison as a controller of the catalyst activity. We found that the addition of Ph2S (diphenylsulfide) to the Pd/C-catalyzed hydrogenation reaction mixture led to reasonable deactivation of Pd/C. By the use of the Pd/C-Ph2S catalytic system, olefins, acetylenes, and azides can be selectively reduced in the coexistence of aromatic carbonyls, aromatic halides, cyano groups, benzyl esters, and N-Cbz (benzyloxycarbonyl) protecting groups. The present method is promising as a general and practical chemoselective hydrogenation process in synthetic organic chemistry.
- Mori, Akinori,Mizusaki, Tomoteru,Miyakawa, Yumi,Ohashi, Eri,Haga, Tomoko,Maegawa, Tomohiro,Monguchi, Yasunari,Sajiki, Hironao
-
p. 11925 - 11932
(2007/10/03)
-
- Highly chemoselective hydrogenation method using novel finely dispersed palladium catalyst on silk-fibroin: Its preparation and activity
-
A palladium-fibroin complex (Pd/Fib) was prepared by soaking silk-fibroin in MeOH solution of Pd(OAc)2 for 2 days (under Ar atmosphere) - 4 days (under air). Pd(OAc)2 was gradually absorbed by fibroin and the rapid reduction of fibroin conjugated Pd(OAc)2 proceeded with MeOH as a reductant at room temperature to be the Pd(0) complex. Pd/Fib catalyzed chemoselective hydrogenation of acetylenes, olefins and azides in the presence of aromatic ketones and aldehydes, halides, N-Cbz protective groups and benzyl esters which are readily hydrogenated using Pd/C or Pd/C(en) as a catalyst.
- Ikawa, Takashi,Sajiki, Hironao,Hirota, Kosaku
-
p. 2217 - 2231
(2007/10/03)
-
- New facile alkoxycarbonylating agent, alkyl pyrazole-1-carboxylates. The preparation and the utilities
-
Alkyl pyrazole-1-carboxylates (2), which were readily prepared from alkyl chloroformate or carbazate in good yields, were provided as the new facile alkoxycarbonylating agents toward the Grignard reagents for the synthesis of one carbon higher carboxylic esters. Also amines were alkoxycarbonylated by 2 to produce the corresponding urethanes even in an aqueous medium. Benzyl 3,5-dimethylpyrazole-1-carboxylate (2d) could be utilized for the Cbz-protection of amino acids and esters in good yield without any racemization.
- Kashima, Choji,Tsuruoka, Shiro,Mizuhara, Saori
-
p. 14679 - 14688
(2007/10/03)
-
- Heterogeneous catalytic transformation of isobutyl benzoate by inverse Tishchenko reaction
-
Using the catalytic transformation of isobutyl benzoate at 663 K in the presence of 12percent MnO2/γ-Al2O3 in a He atmosphere as an example, it has been shown that the inverse Tishchenko reaction can take place at a temperature above 600 K.Isobutyl benzoa
- Glebov, L. S.,Shuikin, A. N.,Kliger, G. A.
-
p. 1417 - 1419
(2007/10/02)
-
- CONVERSIONS OF ISOBUTYLBENZOATE ON HETEROGENEOUS CATALYSTS
-
For the case of isobutylbenzoate, a study has been made of the possibility of producing aldehydes from esters in the presence of heterogeneous catalysts of different composition.It has been shown that the best results (88percent ester conversion with an o
- Shuikin, A. N.,Glebov, L. S.,Kliger, G. A.,Zaikin, V. G.,Besprozvannyi, M. A.
-
p. 325 - 332
(2007/10/02)
-
- S,S-Bis Dithiocarbonate. A New Reactive Coupling Agent for the Direct Esterification of Carboxylic Acids
-
S,S-Bis dithiocarbonate, prepared from 4,6-dimethyl-2-pyrimidinethiol hydrochloride and phosgene in the presence of triethylamine in dichloromethane/toluene, is a new reactive coupling agent for the direct esterification of carboxylic acids with alcohols.
- Kim, Sunggak,Kim, Sung Soo
-
p. 1017 - 1019
(2007/10/02)
-
- Kinetics and Mechanism of the Lewis Acid-catalyzed Addition of Alcohols to Ketenes in Diethyl Ether Solution
-
A kinetic study is reported of the addition of alcohols to dimethyl- and diphenyl-ketene in diethyl ether solution at 25 deg in the presence of HgCl2, ZnCl2, SbCl3, and Bun2SnCl2.Except for HgCl2, which forms insoluble complexes with the reactants, the metal halides catalyse the addition to dimethylketene.The catalysed addition involves the reaction of metal halide-alcohol adducts with the ketene.In general, the stronger the adduct as a Broensted acid, The faster is the addition of the alcohol to the ketene, although C-O, as well as C-H, bond formation is propably significant kinetically.A cyclic transition state is suggested.For diphenylketene, strongly acidic adducts transfer alcohol to the ketene so slowly that inhibition of alcoholysis is observed.Inhibition arises because the spontaneous alcoholysis is reduced as free alcohol is removed as unreactive adduct.However, weak-metal halide acids probably lead to catalysis.It is concluded (a) that the different behaviour of the two ketenes in these reactions is in keeping with their behaviour observed when they react with carboxylic acids in ether, and (b) that metal halide-catalysed alcoholysis of ketenes is generally similar to that observed with aryl isocyanates, except that tin-based catalysts are relatively more effective with isocyanates.
- Poon, Nai L.,Satchell, Derek P. N.
-
p. 1551 - 1554
(2007/10/02)
-
- A Simple and Mild Esterification Method for Carboxylic Acids Using Mixed Carboxylic-Carbonic Anhydrides
-
A simple and mild esterification method using mixed carboxylic-carbonic anhydrides has been developed.Simple aliphatic carboxylic esters are prepared in high yields by the reaction of acids with equimolar amounts of chloroformates (2,2,2-trichloroethyl chloroformate is an exception) and triethylamine in the presence of a catalytic amount of 4-(dimethylamino)pyridine.Although aromatic acids give a mixture of the ester, the acid anhydride, and the carbonate under normal conditions utilized in this study, it is found that increasing the amount of 4-(dimethylamino)pyridine drastically decreases the formation of the acid anhydride and the carbonate, affording a satisfactory yield of the ester.This method reaches a limit with sterically hindered acids and the formation of the acid anhydride and the carbonate is favored.
- Kim, Sunggak,Lee, Jae In,Kim, Youn Chul
-
p. 560 - 565
(2007/10/02)
-
- A NEW CONVENIENT METHOD FOR THE ESTERIFICATION OF CARBOXYLIC ACIDS
-
Reaction of carboxylic acids with equimolar amounts of alkyl chloroformate and triethylamine in the presence of a catalytic amount of 4-dimethylaminopyridine affords the corresponding esters in high yields without the formation of the symmetrical anhydride in most carboxylic acids.
- Kim, Sunggak,Kim, Youn Chul,Lee, Jae In
-
p. 3365 - 3368
(2007/10/02)
-
- A CONVENIENT METHOD FOR THE PREPARATION OF CARBOXYLIC ESTERS
-
8-Quinolinesulfonyl tetrazolide (QS-t) was found to be a useful coupling agent for the preparation of carboxylic esters.KEYWORDS--esterification; carboxylic esters; coupling agent; coupling reaction; base; alcohols; carboxylic acids
- Takaku, Hiroshi,Sasaki, Naohiko,Morita, Kazuhiro
-
p. 2633 - 2634
(2007/10/02)
-