- The Stereoselective Oxidation of para-Substituted Benzenes by a Cytochrome P450 Biocatalyst
-
The serine 244 to aspartate (S244D) variant of the cytochrome P450 enzyme CYP199A4 was used to expand its substrate range beyond benzoic acids. Substrates, in which the carboxylate group of the benzoic acid moiety is replaced were oxidised with high activity by the S244D mutant (product formation rates >60 nmol.(nmol-CYP)?1.min?1) and with total turnover numbers of up to 20,000. Ethyl α-hydroxylation was more rapid than methyl oxidation, styrene epoxidation and S-oxidation. The S244D mutant catalysed the ethyl hydroxylation, epoxidation and sulfoxidation reactions with an excess of one stereoisomer (in some instances up to >98 %). The crystal structure of 4-methoxybenzoic acid-bound CYP199A4 S244D showed that the active site architecture and the substrate orientation were similar to that of the WT enzyme. Overall, this work demonstrates that CYP199A4 can catalyse the stereoselective hydroxylation, epoxidation or sulfoxidation of substituted benzene substrates under mild conditions resulting in more sustainable transformations using this heme monooxygenase enzyme.
- Chao, Rebecca R.,Lau, Ian C.-K.,Coleman, Tom,Churchman, Luke R.,Child, Stella A.,Lee, Joel H. Z.,Bruning, John B.,De Voss, James J.,Bell, Stephen G.
-
p. 14765 - 14777
(2021/09/14)
-
- Amino Acid-Functionalized Metal-Organic Frameworks for Asymmetric Base–Metal Catalysis
-
We report a strategy to develop heterogeneous single-site enantioselective catalysts based on naturally occurring amino acids and earth-abundant metals for eco-friendly asymmetric catalysis. The grafting of amino acids within the pores of a metal-organic framework (MOF), followed by post-synthetic metalation with iron precursor, affords highly active and enantioselective (>99 % ee for 10 examples) catalysts for hydrosilylation and hydroboration of carbonyl compounds. Impressively, the MOF-Fe catalyst displayed high turnover numbers of up to 10 000 and was recycled and reused more than 15 times without diminishing the enantioselectivity. MOF-Fe displayed much higher activity and enantioselectivity than its homogeneous control catalyst, likely due to the formation of robust single-site catalyst in the MOF through site-isolation.
- Newar, Rajashree,Akhtar, Naved,Antil, Neha,Kumar, Ajay,Shukla, Sakshi,Begum, Wahida,Manna, Kuntal
-
supporting information
p. 10964 - 10970
(2021/03/29)
-
- Method for synthesizing secondary alcohol in water phase
-
The invention discloses a method for synthesizing secondary alcohol in a water phase. The method comprises the following steps: taking ketone as a raw material, selecting water as a solvent, and carrying out catalytic hydrogenation reaction on the ketone in the presence of a water-soluble catalyst to obtain the secondary alcohol, wherein the catalyst is a metal iridium complex [Cp * Ir (2, 2'-bpyO)(OH)][Na]. Water is used as the solvent, so that the use of an organic solvent is avoided, and the method is more environment-friendly; the reaction is carried out at relatively low temperature and normal pressure, and the reaction conditions are mild; alkali is not needed in the reaction, so that generation of byproducts is avoided; and the conversion rate of the raw materials is high, and the yield of the obtained product is high. The method not only has academic research value, but also has a certain industrialization prospect.
- -
-
Paragraph 0031-0032
(2021/07/14)
-
- Ambient-pressure highly active hydrogenation of ketones and aldehydes catalyzed by a metal-ligand bifunctional iridium catalyst under base-free conditions in water
-
A green, efficient, and high active catalytic system for the hydrogenation of ketones and aldehydes to produce corresponding alcohols under atmospheric-pressure H2 gas and ambient temperature conditions was developed by a water-soluble metal–ligand bifunctional catalyst [Cp*Ir(2,2′-bpyO)(OH)][Na] in water without addition of a base. The catalyst exhibited high activity for the hydrogenation of ketones and aldehydes. Furthermore, it was worth noting that many readily reducible or labile functional groups in the same molecule, such as cyan, nitro, and ester groups, remained unchanged. Interestingly, the unsaturated aldehydes can be also selectively hydrogenated to give corresponding unsaturated alcohols with remaining C=C bond in good yields. In addition, this reaction could be extended to gram levels and has a large potential of wide application in future industrial.
- Wang, Rongzhou,Yue, Yuancheng,Qi, Jipeng,Liu, Shiyuan,Song, Ao,Zhuo, Shuping,Xing, Ling-Bao
-
-
- Rhodium-Catalyzed Regiodivergent Synthesis of Alkylboronates via Deoxygenative Hydroboration of Aryl Ketones: Mechanism and Origin of Selectivities
-
Here, we report an efficient rhodium-catalyzed deoxygenative borylation of ketones to synthesize alkylboronates, in which the regioselectivity can be switched by the choice of the ligand. The linear alkylboronates were obtained exclusively in the presence of P(nBu)3, and PPh2Me favored the formation of branched alkylboronates. The protocol also allows access to 1,1,2-triboronates from the readily available ketones. Mechanistic studies suggest that this Rh-catalyzed deoxygenative borylation of ketones goes through an alkene intermediate, which undergoes regiodivergent hydroboration to afford linear and branched alkylboronates. The different steric effects of PPh2Me and P(nBu)3 were found to be responsible for product selectivity by density functional theory calculations. The alkene intermediate can alternatively undergo sequential dehydrogenative borylation and hydroboration to deliver the triboronates.
- Zhang, Bing,Xu, Xin,Tao, Lei,Lin, Zhenyang,Zhao, Wanxiang
-
p. 9495 - 9505
(2021/08/04)
-
- Iridium Azocarboxamide Complexes: Variable Coordination Modes, C-H Activation, Transfer Hydrogenation Catalysis, and Mechanistic Insights
-
Azocarboxamides, a special class of azo ligands, display intriguing electronic properties due to their versatile binding modes and coordination flexibility. These properties may have significant implications for their use in homogeneous catalysis. In the present report, half-sandwich Ir-Cp? complexes of two different azocarboxamide ligands are presented. Different coordination motifs of the ligand were realized using base and chloride abstracting ligand to give N∧N-, N∧O-, and N∧C-chelated monomeric iridium complexes. For the azocarboxamide ligand having methoxy substituted at the phenyl ring, a mixture of N∧C-chelated mononuclear (Ir-5) and N∧N,N∧C-chelated dinuclear complexes (Ir-4) were obtained by activating the C-H bond of the aryl ring. No such C-H activation was observed for the ligand without the methoxy substituent. The molecular identity of the complexes was confirmed by spectroscopic analyses, while X-ray diffraction analyses further confirmed three-legged piano-stool structure of the complexes along with the above binding modes. All complexes were found to exhibit remarkable activity as precatalysts for the transfer hydrogenation of carbonyl groups in the presence of a base, even at low catalyst loading. Optimization of reaction conditions divulged superior catalytic activity of Ir-3 and Ir-4 complexes in transfer hydrogenation over the other catalysts. Investigation of the influence of binding modes on the catalytic activity along with wide range substrates, tolerance to functional groups, and mechanistic insights into the reaction pathway are also presented. These are the first examples of C-H activation in azocarboxamide ligands.
- Albold, Uta,Chandra, Shubhadeep,Hazari, Arijit Singha,Kelm, Ola,Ko?mrlj, Janez,Sarkar, Biprajit,Urankar, Damijana
-
supporting information
p. 3907 - 3916
(2021/12/03)
-
- Transfer hydrogenation via generation of hydride intermediate and base-free alcohol oxidation activity studies on designed ruthenium complexes derived from NNN pincer type ligands
-
Ruthenium complexes(1–3) have been synthesized using pincer-type ligands L1 = (E)-2-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)pyridine, L2 = (E)-2-(1-phenyl-2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)pyridine, L3 = (E)-2-(phenyl(2-phenyl-2-(pyridin-2-yl)hydrazono) methyl)pyridine. The molecular structures of all the complexes 1, 2 and 3 were determined by using single crystal X-ray diffraction. These complexes showed excellent catalytic activities such as transfer hydrogenation and alcohol oxidation. Theoretical calculations have been performed to understand the electronic properties of all the complexes using B3LYP as a function and LANL2DZ as a basis set.
- Singh, Prasoon Raj,Maji, Ankur,Singh, Ovender,Singh, Udai P.,Ghosh, Kaushik
-
-
- Method for preparing alcohol compounds through hydrogenation reduction of ketone and aldehyde
-
The invention belongs to the technical field of medical and natural compound chemical intermediates and related chemistry, and provides a method for preparing alcohol compounds through a hydrogenationreduction of ketone and aldehyde. Ketone, aldehyde and derivatives thereof, which are used as raw materials, are subjected to hydrogenation reduction with nano-porous palladium as a catalyst and hydrogen as a hydrogen source, wherein the pressure of hydrogen is 0.1-0.5 MPa, the molar concentration of the ketone, aldehyde and derivatives thereof in the solvent is 0.01-2 mmol/m, the pore skeleton size of the adopted catalyst is 1-50 nm, and the molar ratio of ketone, aldehyde and derivatives thereof to the catalyst is 1:0.01 to 1:0.5. The method has the advantages of high product yield, very mild reaction conditions, simplicity in operation and post-treatment, good repeatability of the catalyst, no obvious reduction of the catalytic effect after the catalyst is used for many times, and provision of the possibility for industrialization.
- -
-
Paragraph 0007; 0055-0059
(2020/02/14)
-
- A facile and highly efficient transfer hydrogenation of ketones and aldehydes catalyzed by palladium nanoparticles supported on mesoporous graphitic carbon nitride
-
A novel transfer hydrogenation methodology for the reduction of ketones (14 examples) and benzaldehyde derivatives (12 examples) to the corresponding alcohols using Pd nanoparticles supported on mesoporous graphitic carbon nitride (mpg-C3N4/Pd) as a reusable catalyst and ammonia borane as a safe hydrogen source in an aqueous solution MeOH/H2O (v/v = 1/1) is described. The catalytic hydrogenation reactions were conducted in a commercially available high-pressure glass tube at room temperature, and the corresponding alcohols were obtained in high yields in 2–5 min. Moreover, the presented transfer hydrogenation protocol shows partial halogen selectivity with bromo-, fluoro-, and chloro-substituted carbonyl analogs. In addition, the present catalyst can be reused up to five times without losing its efficiency, and scaling-up the reaction enables α-methylbenzyl alcohol to be produced in 90% isolated yield.
- Ni?anc?, Bilal,Da?alan, Ziya
-
-
- Polymer supported N-heterocyclic carbene ruthenium complex catalyzed transfer hydrogenation of ketones
-
Polymer supported N-heterocyclic carbene ruthenium complex (Poly-Ru-1) was synthesized by free radical polymerization of Ru complex monomer and divinylbenzene. The structure of Poly-Ru-1 was characterized by 13C solid-state NMR spectroscopy, N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS). 13C solid-state NMR spectra indicated the complete polymerization of Ru complex monomer. Poly-Ru-1 had the high specific surface area of 286.7 m2 g?1 and ruthenium was in +2 oxidation state. Poly-Ru-1 showed higher catalytic activity than the corresponding homogenous catalyst in transfer hydrogenation of ketones, which was attributed to the high dispersion of the active sites.
- Wang, Rong,Qin, Li,Wang, Xin,Chen, Bihua,Zhao, Yun,Gao, Guohua
-
-
- Synthesis and characterization of Pd(II) and Ru(II) complexes of tetradentate N,N,N,N-(Diphosphinomethyl)amine ligands: Catalytic properties in transfer hydrogenation and heck coupling reactions
-
– Tetradentate N,N,N,N-(diphosphinomethyl)amine ligands and their Pd(II) and Ru(II) complexes were synthesized under a nitrogen atmosphere using Schlenk technique. The synthesized ligands and the complexes were characterized with 1H- and 31P-NMR, FT-IR, TG/DTA, and elemental analysis techniques. Pd(II) Complexes were used as catalysts in Heck coupling reactions and Ru(II) complexes were tried in transfer hydrogenation reactions of acetophenone derivatives. According to the results, L4-Pd(II) complex showed the best catalytic activity in the Heck coupling reaction of p-methylbromobenzene with o-chlorostyrene. It was confirmed that the reduction of bromo and chloroacetophenones in all catalysts the conversions were higher. The results showed that Ru(II) complexes as efficient catalysts and up to 99percent conversions was occurred with bromo and chloro acetophenones in K2CO3/isopropyl alcohol media at 80 °C.
- Akkaya, Seda K??ker,Kele?, Mustafa,Uru?, Serhan
-
-
- Selective hydrodeoxygenation of hydroxyacetophenones to ethyl-substituted phenol derivatives using a FeRu?SILP catalyst
-
The selective hydrodeoxygenation of hydroxyacetophenone derivatives is achieved opening a versatile pathway for the production of valuable substituted ethylphenols from readily available substrates. Bimetallic iron ruthenium nanoparticles immobilized on an imidazolium-based supported ionic liquid phase (Fe25Ru75?SILP) show high activity and stability for a broad range of substrates without acidic co-catalysts. This journal is
- Bordet, Alexis,Goclik, Lisa,Leitner, Walter,Offner-Marko, Lisa
-
supporting information
p. 9509 - 9512
(2020/09/02)
-
- Mont-K10 Supported Fe(II) Schiff-Base Complex as an Efficient Catalyst for Hydrogenation of Ketones
-
Abstract: A new Fe(II) Schiff base complex anchored on mont-K10 (Fe@imine-mont-K10) was synthesized and extensively characterized by FTIR, powder X-ray diffraction, SEM–EDX, TEM, ESR, X-ray photoelectron spectroscopy (XPS), BET surface area measurement, solid state 29Si NMR and ICP-AES analysis. The catalytic activity of the complex was investigated for hydrogenation of ketones. The results indicated that it exhibited good catalytic activity for hydrogenation of aromatic as well as aliphatic ketones in i-PrOH/CH3CN (1:1) using Na-i-OPr as base at 80?°C resulting in moderate to excellent isolated yields (51–99%) of their corresponding products. The catalyst shows good reusability. Graphical Abstract: [Figure not available: see fulltext.].
- Sultana, Samim,Borah, Geetika,Gogoi, Pradip. K.
-
p. 2142 - 2157
(2019/05/28)
-
- Synthesis of a novel magnetic nanocatalyst based on rhodium complex for transfer hydrogenation of ketone
-
A magnetic heterogeneous nanocatalyst based on novel rhodium complex is designed.?The transfer hydrogenation of ketones with 2-propanol as hydrogen donor and the rhodium complex as nanocatalyst was achieved. High yields of ketones under mild conditions were obtained from easily available precursors.
- Kooti,Nasiri
-
-
- Synthesis, Stability, and (De)hydrogenation Catalysis by Normal and Abnormal Alkene- And Picolyl-Tethered NHC Ruthenium Complexes
-
A series of p-cymene and cyclopentadienyl Ru(II)-aNHC complexes were synthesized from 2-methylimidazolium salts with either an N-bound alkenyl (1, 3) or picolyl tether (6, 7). The C(5)-Me substituted alkenyl-tethered analogues (2, 4) were also synthesized. Ag-mediated C(2)-dealkylation was a prominent side reaction that led to the formation of normally bound NHC Ru(II) complexes, which in selected cases were isolated (5, 8). A C(4)- over C(2)-selectivity for ruthenium binding was established by protecting the C(2)-position with an iPr group on the imidazolium precursor, for which unique p-cymene (9) and cyclopentadienyl (10) Ru(II)-aNHC derivatives were synthesized. All complexes were applied in the transfer hydrogenation of ketones and in secondary alcohol oxidation, with higher catalytic activity for the p-cymene over the cyclopentadienyl systems, as well as the alkenyl- over the picolyl-containing aNHC complexes.
- Malan, Frederick P.,Singleton, Eric,Van Rooyen, Petrus H.,Albrecht, Martin,Landman, Marilé
-
p. 2624 - 2635
(2019/07/03)
-
- Carbohydrate-functionalized N-heterocyclic carbene Ru(ii) complexes: Synthesis, characterization and catalytic transfer hydrogenation activity
-
Three Ru complexes containing carbohydrate/N-heterocyclic carbene hybrid ligands were synthesized that were comprised of a triazolylidene coordination site and a directly linked per-acetylated glucosyl (5Glc) or galactosyl unit (5Gal), or a glycosyl unit linked through an ethylene spacer (6). Electrochemical and UV-vis analysis indicate only minor perturbation of the electronic configuration of the metal center upon carbohydrate installation. Deprotection of the carbohydrate was accomplished under basic conditions to afford complexes that were stable in solution over several hours, but decomposed in the solid state. Complexes 5 and 6 were used as pre-catalysts for transfer hydrogenation of ketones under basic conditions, i.e. conditions that lead to in situ deprotection of the carbohydrate entity. The carbohydrate directly influences the catalytic activity of the metal center. Remotely linked carbohydrates (complex 6) induce significantly lower catalytic activity than directly linked carbohydrates (complexes 5Glc, 5Gal), while unfunctionalized triazolylidenes are an order of magnitude more active. These observations and substrate variations strongly suggest that substrate bonding is rate-limiting for transfer hydrogenation in these hybrid carbohydrate/triazolylidene systems.
- Byrne, Joseph P.,Musembi, Pauline,Albrecht, Martin
-
p. 11838 - 11847
(2019/08/13)
-
- Selective C-O Bond Cleavage of Lignin Systems and Polymers Enabled by Sequential Palladium-Catalyzed Aerobic Oxidation and Visible-Light Photoredox Catalysis
-
Lignin, which is a highly cross-linked and irregular biopolymer, is nature's most abundant source of aromatic compounds and constitutes an attractive renewable resource for the production of aromatic commodity chemicals. Herein, we demonstrate a practical and operationally simple two-step degradation approach involving Pd-catalyzed aerobic oxidation and visible-light photoredox-catalyzed reductive fragmentation for the chemoselective cleavage of the β-O-4 linkage - the predominant linkage in lignin - for the generation of lower-molecular-weight aromatic building blocks. The developed strategy affords the β-O-4 bond cleaved products with high chemoselectivity and in high yields, is amenable to continuous flow processing, operates at ambient temperature and pressure, and is moisture- and oxygen-tolerant.
- Magallanes, Gabriel,K?rk?s, Markus D.,Bosque, Irene,Lee, Sudarat,Maldonado, Stephen,Stephenson, Corey R. J.
-
p. 2252 - 2260
(2019/02/19)
-
- A Rational Active-Site Redesign Converts a Decarboxylase into a C=C Hydratase: "tethered Acetate" Supports Enantioselective Hydration of 4-Hydroxystyrenes
-
The promiscuous regio- and stereoselective hydration of 4-hydroxystyrenes catalyzed by ferulic acid decarboxylase from Enterobacter sp. (FDC-Es) depends on bicarbonate bound in the active site, which serves as a proton relay activating a water molecule fo
- Payer, Stefan E.,Pollak, Hannah,Glueck, Silvia M.,Faber, Kurt
-
p. 2438 - 2442
(2018/03/13)
-
- Synthesis, characterization, and organocatalytic application of chiral ionic liquids derived from (S,R)-noscapine
-
(S,R)-Noscapine, a phthalideisoquinoline alkaloid has been used as precursor for the synthesis of chiral ionic liquids (CILs). Noscapine based CILs have been synthesized from reaction between (S,R)-noscapine and methyl iodide in acetonitrile at room temperature. The synthesized CILs have been characterized by 1H NMR, 13C NMR, EI-MS, and polarimetry techniques. These CILs have been used as organocatalysts in the enantioselective reduction of prochiral ketones to produce optically active secondary alcohols. The optically active secondary alcohols have been obtained with excellent yields and low to moderate enantiomeric excess (ee); also the complete enantiomeric excess (100% ee) has been achieved in some cases.
- Kaur, Nirmaljeet,Chopra, Harish Kumar
-
-
- Visible-Light-Triggered C-C and C-N Bond Formation by C-S Bond Cleavage of Benzylic Thioethers
-
The cleavage of sulfidic C-S bonds under visible-light irradiation was harnessed to generate carbocations under neutral conditions and synthesize valuable di- and triarylalkanes as well as benzyl amines. To this end, photoredox catalysis and direct photoinduced C-S bond cleavage are used as complementary approaches and participate in the versatility of the general strategy. Extensive mechanistic studies have demonstrated the diversity of the reaction mechanism at work in these different reactions.
- Lanzi, Matteo,Merad, Jérémy,Boyarskaya, Dina V.,Maestri, Giovanni,Allain, Clémence,Masson, Géraldine
-
supporting information
p. 5247 - 5250
(2018/09/13)
-
- Multigram Scale Enzymatic Synthesis of (R)-1-(4′-Hydroxyphenyl)ethanol Using Vanillyl Alcohol Oxidase
-
The enantioselective oxyfunctionalisation of C?H bonds is a highly interesting reaction, as it provides access to chiral alcohols that are important pharmaceutical building blocks. However, it is hard to achieve using traditional methods. One way in which it can be achieved is through the action of oxidative enzymes. Although many reports of the oxyfunctionalisation capabilities of enzymes at an analytical scale have been published, reports on the use of enzymes to achieve oxyfunctionalisation on a synthetically relevant scale are fewer. Here, we describe the scale-up of the conversion of 4-ethylphenol to (R)-1-(4′-hydroxyphenyl)ethanol using the flavin-dependent enzyme vanillyl alcohol oxidase. The process was optimised by testing different reaction media and substrate and enzyme concentrations and by performing it under an oxygen atmosphere. Under optimised reaction conditions, 4.10 g (R)-1-(4′-hydroxyphenyl)ethanol at 97% ee was obtained from 10 g 4-ethylphenol (isolated yield 36%). These results highlight some of the challenges that can be encountered during scale-up of an enzymatic oxyfunctionalisation process to a synthetically relevant scale and will be of use for the development of enzymatic processes for the synthesis of industrially relevant compounds. (Figure presented.).
- Ewing, Tom A.,Kühn, Jasmin,Segarra, Silvia,Tortajada, Marta,Zuhse, Ralf,van Berkel, Willem J. H.
-
p. 2370 - 2376
(2018/06/20)
-
- Copper-Based Intermetallic Electride Catalyst for Chemoselective Hydrogenation Reactions
-
The development of transition metal intermetallic compounds, in which active sites are incorporated in lattice frameworks, has great potential for modulating the local structure and the electronic properties of active sites, and enhancing the catalytic activity and stability. Here we report that a new copper-based intermetallic electride catalyst, LaCu0.67Si1.33, in which Cu sites activated by anionic electrons with low work function are atomically dispersed in the lattice framework and affords selective hydrogenation of nitroarenes with above 40-times higher turnover frequencies (TOFs up to 5084 h-1) than well-studied metal-loaded catalysts. Kinetic analysis utilizing isotope effect reveals that the cleavage of the H-H bond is the rate-determining step. Surprisingly, the high carrier density and low work function (LWF) properties of LaCu0.67Si1.33 enable the activation of hydrogen molecules with extreme low activation energy (Ea = 14.8 kJ·mol-1). Furthermore, preferential adsorption of nitroarenes via a nitro group is achieved by high oxygen affinity of LaCu0.67Si1.33 surface, resulting in high chemoselectivity. The present efficient catalyst can further trigger the hydrogenation of other oxygen-containing functional groups such as aldehydes and ketones with high activities. These findings demonstrate that the transition metals incorporated in the specific lattice site function as catalytically active centers and surpass the conventional metal-loaded catalysts in activity and stability.
- Ye, Tian-Nan,Lu, Yangfan,Li, Jiang,Nakao, Takuya,Yang, Hongsheng,Tada, Tomofumi,Kitano, Masaaki,Hosono, Hideo
-
p. 17089 - 17097
(2017/12/06)
-
- Zinc-Mediated Efficient and Selective Reduction of Carbonyl Compounds
-
We herein describe for the first time that an optimized combination of Zn and NH4Cl can be used for the selective reduction of aldehydes and ketones to the corresponding alcohols. The aldehyde and keto groups are selectively reduced in the presence of azide, cyano, epoxy, ester, and carbon–carbon double-bond functional groups. A broad functional-group compatibility, chemoselective reduction of aldehydes in the presence of ketones, and selective reduction of isatins at the C3 carbonyl group are the highlights of the present method.
- Mandal, Tirtha,Jana, Snehasish,Dash, Jyotirmayee
-
p. 4972 - 4983
(2017/09/13)
-
- Syntheses, characterisation, and catalytic role of (η5-C5Me5)Rh(III) guanidinato complexes in transfer hydrogenation (TH) and TH-etherification
-
A family of air stable half sandwich meal guanidinato complexes ([(η5-Cp?)MCl{κ2(N,N′)((ArN)2C-N(H)Ar)}]) (M = Rh and Ir; Cp? = C5Me5; Ar = aryl) were synthesized in good yield and characterised by elemental analyses, IR, and NMR (1H, 13C, and 19F) spectroscopy. The geometry of the metal and the conformations of the guanidinate ligands in the complexes were studied by single crystal X-ray diffraction. The solution behaviour of representative complexes was investigated by detailed NMR studies including variable temperature and variable concentration 1H NMR measurements. The new complexes were screened as catalysts for transfer hydrogenation (TH) of acetophenone under basic and base free conditions and from these experiments, ([(η5-Cp?)RhCl{κ2(N,N′)((ArN)2C-N(H)Ar)}]) (Ar = 3,5-(CF3)2C6H3; 3) was chosen as the preferred catalyst due to its slightly better catalytic activity than other complexes. The utility of 3 in TH of a variety of carbonyl compounds was explored under basic and base free conditions. Tandem catalysis involving TH of a carbonyl group and etherification of the resulting -CH2OH group in reduction products of salicylaldehyde, 2-hydroxy-1-naphthaldehyde and 5-(hydroxymethyl)furfural was achieved in the presence of 3 under base free conditions. The role of the guanidinate ligands in the complexes for basic and base free TH of carbonyl compounds and TH-etherification tandem catalysis is discussed. Plausible mechanisms for TH and TH-etherification are outlined.
- Kumar, Robin,Thirupathi, Natesan
-
p. 33890 - 33904
(2017/07/17)
-
- Efficient and recyclable Ru(II) arene thioamide catalysts for transfer hydrogenation of ketones: Influence of substituent on catalytic outcome
-
Six cationic ruthenium(II) arene thioamide complexes with the general molecular formula [Ru(η6-p-cymene)(PPh3)(L)]+ [where, L = pyridine-2-thioamide and its derivatives] have been successfully synthesized from the reaction of [Ru(η6-p-cymene)Cl2]2 with chelating thioamide ligands and PPh3 in methanol in 1:2 M ratio respectively. All the complexes were isolated as their BPh4?salts and were fully characterized by analytical and spectral (FT-IR, UV-Vis and1H-NMR) methods. The solid-state structure of one of the complexes, [Ru(η6-p-cymene)(PPh3)(L4)]BPh4 (4) (L4 = N-(2, 4, 6-Trimethylphenyl)pyridine-2-thiocarboxamide) has been established by X-ray single crystal diffraction which indicates a pseudo-octahedral (piano-stool) coordination geometry is present in the complex. The ruthenium(II) complexes have been examined for the transfer hydrogenation of various aromatic, heterocycle and cyclic ketones. The formation of ruthenium(II) hydride is confirmed by 1H- NMR and is proposed as the catalytic intermediate in this reaction. Under the optimized conditions, these ruthenium complexes served as excellent catalyst precursors which smoothly reduce the ketones with conversion up to 100%. The influence of other variables on the transfer hydrogenation reaction such as solvent, base, temperature, time, catalyst loading and substrate scope is also reported. Furthermore, the catalyst could be easily recovered and reused at least three times without obvious loss of conversions.
- Kanchanadevi, Appukutti,Ramesh, Rengan,Semeril, David
-
-
- Deracemization of 1-phenylethanol via tandem biocatalytic oxidation and reduction
-
(R)-1-Arylethanols and other secondary alcohols were prepared at high ee (>90%) by oxidative kinetic resolution using resting cells of the yeast Candida albicans CCT 0776. The deracemization process of 1-phenylethanol 1a catalyzed by the yeast was elucidated by studying each step separately. It was determined that the reaction occurred via cyclic deracemization, to give (R)-1a in 89% yield and with 98% ee. Finally, deracemization by stereoinversion of rac-1a was studied using a tandem process of C. albicans followed by Lactobacillus brevis CCT 3745. Inverting the sequence of these microorganisms produced an enantiomerically pure antipode.
- Nasário, Fábio D.,Cazetta, Tarcila,Moran, Paulo J.S.,Rodrigues, J. Augusto R.
-
p. 404 - 409
(2016/05/19)
-
- Electrocatalytic hydrocarbon hydroxylation by ethylbenzene dehydrogenase from Aromatoleum aromaticum
-
We report the electrocatalytic activity of ethylbenzene dehydrogenase (EBDH) from the β-proteobacterium Aromatoleum aromaticum. EBDH is a complex 155 kDa heterotrimeric molybdenum/iron-sulfur/heme protein which catalyzes the enantioselective hydroxylation of nonactivated ethylbenzene to (S)-1-phenylethanol without molecular oxygen as cosubstrate. Furthermore, it oxidizes a wide range of other alkyl-substituted aromatic and heterocyclic compounds to their secondary alcohols. Hydroxymethylferrocenium (FM) is used as an artificial electron acceptor for EBDH in an electrochemically driven catalytic system. Electrocatalytic activity of EBDH is demonstrated with both its native substrate ethylbenzene and the related substrate p-ethylphenol. The catalytic system has been modeled by electrochemical simulation across a range of sweep rates and concentrations of each substrate, which provides new insights into the kinetics of the EBDH catalytic mechanism.
- Kalimuthu, Palraj,Heider, Johann,Knack, Daniel,Bernhardt, Paul V.
-
p. 3456 - 3463
(2015/04/27)
-
- Synthesis and characterization of rhodium(I) complexes with P-N donor ligands and their catalytic application in transfer hydrogenation of carbonyl group
-
Three rhodium(I) complexes of the types [Rh(COE)Cl(η2-L)] (1a,1b) and [RhCl(η2-L) (η1-L)] (1c), where L = P~N donor ligands 2-[2-(diphenylphosphino) ethyl]pyridine, (PPh2Etpy) (a), 2-(diphenylphosphino)pyridine
- Borah, Geetika,Sarmah, Podma Pollov,Boruah, Devajani
-
p. 1226 - 1230
(2015/07/15)
-
- Calcium-catalyzed carboarylation of alkynes
-
The first transition-metal-free carboarylation of alkynes with commercial and readily available alcohols as alkylating agents was realized in the presence of an environmentally benign calcium catalyst. Thereby, a novel protocol for the one-step synthesis of highly congested, all-carbon tetrasubstituted alkenes, as incorporated in potentially bioactive, complex dihydronaphthalene, chromene and dihydroquinoline structures, is provided. The reaction features an unprecedented, particularly wide substrate scope, good functional-group tolerance and simple experimental operation under mild reaction conditions. Finally free: The first transition-metal-free one-step synthesis of highly congested, all-carbon tetrasubstituted olefins has been realized by a calcium-catalyzed carboarylation reaction. Internal alkynes react with alcohols as alkylating reagent under mild reaction conditions, which provides access to a variety of useful structural scaffolds via highly reactive trisubstituted vinyl cations.
- Fu, Liang,Niggemann, Meike
-
supporting information
p. 6367 - 6370
(2015/04/22)
-
- Synthesis and molecular structure of ruthenium(III) benzoylhydrazone complexes: Substituents effect on transfer hydrogenation of ketones
-
An easy and convenient synthesis of a new series of octahedral ruthenium(III) complexes bearing benzoylhydrazone of general formula [Ru(L)Cl(PPh3)2] (where L = 2-hydroxy-1-naphthaldehyde benzoylhydrazone) has been reported. The composition of all the complexes has been unequivocally characterized by microanalysis, IR, electronic, magnetic and EPR spectroscopic techniques. The substituted benzoylhydrazone ligands behave as a dianionic tridentate O, N and O donors and coordinate to ruthenium via the phenolic oxygen, the azomethine nitrogen and the deprotonated amide oxygen. The complexes exhibit moderately strong ligand-to-metal charge transfer transitions in the visible region and intraligand transition in the UV region. Magnetic moment of the complexes (298 K) lies in the range 1.72-1.97 μB reveals the presence of one unpaired electron in the metal centre. The low spin mononuclear Ru(III) benzoylhydrazone complexes display rhombic EPR spectral pattern in frozen solution. The molecular structure of two of the complexes has been established by single crystal X-ray crystallography and indicates the presence of a distorted octahedral geometry in these complexes. Further, the complexes 1-5 have been proven to catalyse the transfer hydrogenation of linear, cyclic and aromatic ketones to their corresponding secondary alcohols in the presence of i-PrOH/KOH at 82 °C and the maximum conversion is up to 99%. The effect of other variables on the transfer hydrogenation reaction such as solvent, base, temperature, time and catalyst loading is also reported.
- Kanchanadevi, Appukutti,Ramesh, Rengan,Bhuvanesh, Nattamai
-
-
- Synthesis, structural characterization and catalytic transfer hydrogenation of ruthenium(II) carbonyl complexes bearing N,N,O pincer type benzoylhydrazone ligands
-
The convenient synthesis of four new octahedral ruthenium(II) carbonyl benzoylhydrazone complexes of the general molecular formula [Ru(L)Cl(CO)(PPh3)] (where HL = substituted 2-acetylpyridine benzoylhydrazones; the H represents the dissociable
- Suganthy, Pandimuni Kalpaga,Prabhu, Rupesh Narayana,Sridevi, Venugopal Shanmugham
-
-
- Ionic and Neutral Half-Sandwich Guanidinatoruthenium(II) Complexes and Their Solution Behavior
-
Ionic and neutral half-sandwich guanidinatoruthenium(II) complexes [(η6-C10H14)RuL(κ2(N,N′){(ArN)2C-N(H)Ar})][OTf] [Ar = 4-MeC6H4, L = 2-methylimidazole (1); Ar = 2-MeC6H4, L = 1,3,5-triaza-7-phosphaadamantane (PTA; 2)], [(ArNH)3C][(η6-C10H14)RuCl3] [Ar = 2-ClC6H4 (3)] and [(η6-C10H14)RuCl(κ2(N,N′){(ArN)2C-N(H)Ar})] [Ar = 2-ClC6H4 (4), 2-FC6H4 (5), 4-ClC6H4 (6), and 4-(NO2)C6H4 (7)] have been isolated and the molecular structures of all but 6 were determined by single-crystal X-ray diffraction. VT 31P{1H} NMR spectroscopy of complex 2 revealed the presence of a mixture of four isomers in a ratio of appproximately 1.4:11.0:1.6:0.1. Theoretical calculations were performed on the syn-syn, syn-anti, anti-syn, and anti-anti conformers of 2, which revealed syn-anti to be the most stable conformer, both in the gas phase and in solution. Furthermore, the energies relating to the interactions between the lone pairs of the nitrogen atoms of the CN3 unit and the antibonding orbital of the central carbon atom in the syn-anti conformer of 2 were investigated by NBO analysis. The 1H NMR spectrum of 3 reveals the presence of two species and their ratio is dependent upon the concentration of 3 in CDCl3 and on the amount of D2O in CD3CN. The two species have been ascribed to the presence of a monomer and a water-bridged dimer. The new complexes 1-7 were screened as pre-catalysts in the transfer hydrogenation of acetophenone and complex 3 was tested as a pre-catalyst in the transfer hydrogenation of a variety of ketones to explore the scope of the reaction.
- Kishan, Ram,Kumar, Robin,Baskaran, Sambath,Sivasankar, Chinnappan,Thirupathi, Natesan
-
p. 3182 - 3194
(2015/07/15)
-
- Ansa-Ruthenium(II) Complexes of R2NSO2DPEN-(CH2)n(η6-Aryl) Conjugate Ligands for Asymmetric Transfer Hydrogenation of Aryl Ketones
-
New 3rd generation designer ansa-ruthenium(II) complexes featuring N,C-alkylene-tethered N,N-dialkylsulfamoyl-DPEN/η6-arene ligands, exhibited good catalytic performance in the asymmetric transfer hydrogenation (ATH) of various classes of (het)aryl ketones in formic acid/triethylamine mixture. In particular, benzo-fused cyclic ketones furnished 98 to >99.9% ee using a low catalyst loading.
- Ki?ic, Andrea,Stephan, Michel,Mohar, Barbara
-
supporting information
p. 2540 - 2546
(2015/08/18)
-
- Synthesis, characterization and catalytic, cytotoxic and antimicrobial activities of two novel cyclotriphosphazene-based multisite ligands and their Ru(II) complexes
-
Two novel cyclotriphosphazene ligands (2 and 3) bearing 3-oxypyridine groups and their corresponding Ru(II) complexes (4 and 5) were synthesized and their structures were characterized using Fourier transform infrared, 1H NMR and 31P
- irali, Digdem Erdener,Uyar, Zafer,Koyuncu, Ismail,Haciolu, Nurcihan
-
p. 536 - 542
(2015/08/04)
-
- Stabilized Rh0-nanoparticles-Montmorillonite clay composite: Synthesis and catalytic transfer hydrogenation reaction
-
Rh0-nanoparticles of around 5 nm size distributed homogeneously into the nanopores of acid activated Montmorillonite clay were generated by incipient wetness impregnation of RhCl3, followed by reduction with ethylene glycol. Acid act
- Sarmah, Podma Pollov,Dutta, Dipak Kumar
-
p. 355 - 360
(2014/01/06)
-
- A ruthenium-grafted triazine functionalized mesoporous polymer: A highly efficient and multifunctional catalyst for transfer hydrogenation and the Suzuki-Miyaura cross-coupling reactions
-
A new ruthenium-grafted mesoporous organic polymer Ru-MPTAT-1 has been synthesized via simple and facile in situ radical polymerization of 2,4,6-triallyloxy-1,3,5-triazine (TAT) in aqueous medium in the presence of an anionic surfactant (sodium dodecyl sulfate) as a template, followed by grafting of Ru(ii) onto its surface. Ru-MPTAT-1 has been characterized by elemental analysis, powder XRD, HRTEM, FT-IR, UV-vis DRS, TG-DTA, FESEM and XPS characterization tools. The Ru-MPTAT-1 material showed very good catalytic activity in the Suzuki-Miyaura cross-coupling reaction for aryl halides and transfer hydrogenation reaction for a series of carbonyl compounds. The catalyst is easily recoverable from the reaction mixture and can be reused several times without appreciable loss of catalytic activity in the above reactions. Highly dispersed and strongly bound Ru(ii) sites at the mesoporous polymer surface could be responsible for the observed high activity of the Ru-MPTAT-1 catalyst in these reactions.
- Salam, Noor,Kundu, Sudipta K.,Roy, Anupam Singha,Mondal, Paramita,Ghosh, Kajari,Bhaumik, Asim,Islam
-
p. 7057 - 7068
(2014/05/06)
-
- Commutative reduction of aromatic ketones to arylmethylenes/alcohols by hypophosphites catalyzed by Pd/C under biphasic conditions
-
An efficient method is reported to reduce aromatic ketones selectively into arylmethylenes or alcohols with hypophosphites and Pd/C, depending on the selected conditions. This study could represent a promising alternative to the classical uses of standard hydrides or molecular hydrogen involved in reduction and deoxygenation procedures.
- Guyon, Carole,Baron, Marc,Lemaire, Marc,Popowycz, Florence,Métay, Estelle
-
p. 2088 - 2095
(2014/03/21)
-
- Asymmetric enzymatic hydration of hydroxystyrene derivatives
-
More than one activity: Owing to their hydratase activity, phenolic acid decarboxylases catalyze the regio- and stereoselective addition of H 2O across the C=C double bond of hydroxystyrene derivatives yielding (S)-4-(1-hydroxyethyl)phenols with up to 82 % conversion and 71 % ee. Based on structure analysis and molecular docking simulations, a catalytic mechanism for this novel enzymatic reaction is proposed. Copyright
- Wuensch, Christiane,Gross, Johannes,Steinkellner, Georg,Gruber, Karl,Glueck, Silvia M.,Faber, Kurt
-
supporting information
p. 2293 - 2297
(2013/04/10)
-
- Ruthenium(II) half-sandwich complexes containing thioamides: Synthesis, structures and catalytic transfer hydrogenation of ketones
-
A new family of cationic half-sandwich complexes of the type [(η6-cymene)Ru(PPh3)(L)]+ (L = bidentate monoanionic thioamide) have been synthesized and isolated as their tetraphenylborate salts. All the synthesized ruthenium(II) arene complexes are air stable and are fully characterized by elemental analysis, spectral and X-ray diffraction methods. In chloroform solution all the complexes exhibit characteristic metal to ligand charge transfer (MLCT) absorptions and ligand based transitions. Molecular structure of the complexes 2, 3 and 4 has been determined by single crystal X-ray crystallography indicates that the thioamide ligands are coordinated to ruthenium as a bidentate O, S donor and a typical piano stool geometry was observed around ruthenium(II) metal center. Complexes 1-5 were tested as catalysts in the transfer hydrogenation of aliphatic and aromatic ketones to secondary alcohols in the presence of 2-propanol/KOH. Further, the influence of base, reaction temperature and catalyst loading in this reaction was also evaluated to find out the most active catalyst.
- Pandiarajan, Devaraj,Ramesh, Rengan
-
-
- Highly active mesoporous chromium silicate catalysts in side-chain oxidation of alkylaromatics
-
We approach a green method in the production of alkylaromatic ketones over hexagonally ordered mesoporous CrSBA-15 catalysts, which were used, in green routes, in the liquid-phase oxidation of alkylaromatics. A promising chemical treatment method was used with ammonium acetate solution to remove the toxic nature of non-framework chromium oxides deposited on the surface of calcined CrSBA-15(8), and the obtained green mesoporous CrSBA-15(8) catalyst was used to find its catalytic activity while the recyclability of mesoporous CrSBA-15 catalysts was also studied. Particularly, the mesoporous CrSBA-15 catalysts synthesized with a variety of chromium contents were extensively used in the production of acetophenone (APO) with various reaction parameters. On the basis of all catalytic results, the mesoporous CrSBA-15(8) catalyst produced a higher selectivity of alkylaromatic ketones (76-100%) as compared to other CrSBA-15 catalysts and was found to be a highly active, recyclable and promising heterogeneous catalyst for selective synthesis of alkylaromatic ketones. The Royal Society of Chemistry 2012.
- Selvaraj,Park,Kim,Kawi,Ha
-
p. 14204 - 14210
(2013/01/15)
-
- Synthesis, structural characterization, electrochemistry and catalytic transfer hydrogenation of ruthenium(II) carbonyl complexes containing tridentate benzoylhydrazone ligands
-
Convenient synthesis of eight new octahedral ruthenium(II) carbonyl benzoylhydrazone complexes having the general molecular formula [Ru(L)(CO)(EPh3)2] (where E = P or As; H2L = benzoylhydrazone ligand, the two H's representing the two dissociable protons) has been described. The substituted benzoylhydrazone ligands behave as a dianionic tridentate O, N and O donors (L) and coordinates to ruthenium via the phenolate oxygen, the azomethine nitrogen and the deprotonated amide oxygen. The compositions of the complexes have been established by elemental analysis and spectral methods (FT-IR, 1H NMR, 13C NMR, UV-vis). The crystal structure of one of the complexes, [Ru(L2)(CO)(PPh3) 2] (2), has been solved by single crystal X-ray crystallography and it indicates the presence of a distorted octahedral geometry in these complexes. All the complexes exhibit metal-to-ligand charge transfer (MLCT) transitions in the visible region and display one quasi-reversible reduction and two irreversible oxidations. Further, the catalytic efficiency of the complexes has been investigated in the case of transfer hydrogenation of ketones to the corresponding secondary alcohols. The influence of base, reaction temperature and catalyst loading in transfer hydrogenation reaction was also evaluated. The complexes were found to be efficient catalysts with conversion up to 99.5% in presence of iso-propanol/KOH.
- Prabhu, Rupesh Narayana,Ramesh, Rengan
-
p. 43 - 51,9
(2012/12/12)
-
- A silica supported cobalt (II) Salen complex as efficient and reusable catalyst for the selective aerobic oxidation of ethyl benzene derivatives
-
A silica supported cobalt (II) Salen complex catalyst has been successfully employed in the aerobic oxidation of alkyl aromatics at atmospheric pressure in the presence of N-hydroxyphthalimide (NHPI). The reaction is particularly selective for the oxidation of the benzylic CH2 group and the major product obtained was ketone. The immobilized catalyst can be easily recovered and reused for at least four reaction cycles without any significant loss of its catalytic activity.
- Rajabi, Fatemeh,Luque, Rafael,Clark, James H.,Karimi, Babak,MacQuarrie, Duncan J.
-
experimental part
p. 510 - 513
(2011/12/15)
-
- C-O hydrogenolysis catalyzed by Pd-PMHS nanoparticles in the company of chloroarenes
-
Catalytic Pd(OAc)2 and polymethylhydrosiloxane (PMHS), in conjunction with aqueous KF, and a catalytic amount of an aromatic chloride, effects the chemo-, regio-, and stereoselective deoxygenation of benzylic oxygenated substrates at room temperature in THF. Preliminary mechanistic experiments suggest the process to involve palladium-nanoparticle-catalyzed hydrosilylation followed by C-O reduction. The chloroarene additive appears to facilitate the hydrogenolysis process through the slow controlled release of HCl.
- Rahaim, Ronald J.,Maleczka, Robert E.
-
supporting information; experimental part
p. 584 - 587
(2011/04/23)
-
- Candida tenuis xylose reductase catalysed reduction of acetophenones: The effect of ring-substituents on catalytic efficiency
-
The catalytic efficiencies of Candida tenuis xylose reductase catalysed reductions of mono-substituted acetophenones are in reasonable correlation with the σ-Hammett coefficients of the substituted phenyl groups. Variations of the substrate transformation rates are hence mainly caused by mesomeric and inductive effects of the substituents, while differences in substrate binding have a secondary relevance. Some substrate 1H NMR chemical shifts and carbonyl IR absorption bands are in reasonable accordance with the catalytic activities and allow the estimation of the transformation rates with good accuracy. The resulting substituted (S)-1-phenyl ethanols are generated in very high enantiomeric excess.
- Vogl, Michael,Kratzer, Regina,Nidetzky, Bernd,Brecker, Lothar
-
experimental part
p. 5863 - 5870
(2011/09/30)
-
- Novel iodine reagent system for regioselective cleavage of epoxides to alcohols
-
Epoxides are converted regioselectively to corresponding higher substituted alcohols with greater yields using diphosphorus tetraiodide (P 2I4) as a reducing agent and a catalytic amount of tetraethylammonium bromide at room temperature. Copyright Taylor & Francis Group, LLC.
- Telvekar, Vikas N.,Rane, Rajesh A.
-
scheme or table
p. 2108 - 2112
(2010/08/19)
-
- Deoxygenation of diarylmethanols with dilute mineral acid
-
A new mild and efficient method for the deoxygenation of diarylmethanols is reported. The reaction employs catalytic hydrochloric acid in ethanol at reflux for 48 h. This reaction works on a variety of diarylmethanol substrates and mitigates the need for expensive and toxic reagents such stannanes and silanes used in alternative procedures. In addition, this reaction can be used in tandem with the deprotection of acid-sensitive silyl ether protecting groups in a one-pot procedure.
- Hope-Ross, Kyle A.,Kadla, John F.
-
experimental part
p. 1003 - 1008
(2011/02/16)
-
- Sodium tetraalkoxyborates: Intermediates for the quantitative reduction of aldehydes and ketones to alcohols through ball milling with NaBH4
-
Stoichiometric molecular solid-state vibrational ball milling, solvent-free kneading ball milling, and mechanochemical ball milling of varied aldehydes and ketones with unmodified sodium borohydride under temperature control uses all hydrogen atoms of the reducing agent in fast reactions. It provides quantitative yields of thermally stable sodium tetraalkoxyborates. The easily isolated solids are extremely sensitive towards hydrolysis, leading to quantitative yields of the corresponding alcohols. The rapid syntheses are regiospecific and stereoselective. Varied substituents are not attacked, including the bromine of α-bromo ketones. Conjugated aldehydes and ketones provide quantitative yields of the allylic alcohols free of contamination by saturated alcohols that would occur by reaction in solution. Depending on the stoichiometric ratio, benzil is quantitatively reduced to benzoin (4:1 ratio) or dihydrobenzoin (2:1 ratio).
- Naimi-Jamal, M. Reza,Mokhtari, Javad,Dekamin, Mohammad G.,Kaupp, Gerd
-
experimental part
p. 3567 - 3572
(2009/10/26)
-
- Immobilized Manihot esculenta preparation as a novel biocatalyst in the enantioselective acetylation of racemic alcohols
-
The enzymatic preparation obtained from a discard of Manihot esculenta roots has been successfully immobilized on calcium alginate hydrogels. This preparation has been tested as a chiral biocatalyst in the enzymatic acylation of a set of racemic aromatic alcohols. Depending on the reaction conditions, excellent enantioselectivities can be achieved. Some parameters that can alter the biocatalytic properties of the enzyme, such as solvent, temperature, acyl donor and substrate structure have been studied exhaustively in order to establish a deeper knowledge of this novel biocatalyst.
- Machado, Luciana L.,Lemos, Telma L.G.,de Mattos, Marcos Carlos,de Oliveira, Maria da Conceicao F.,de Gonzalo, Gonzalo,Gotor-Fernandez, Vicente,Gotor, Vicente
-
p. 1418 - 1423
(2008/12/20)
-
- Clean and selective oxidation of aromatic alcohols using silica-supported Jones' reagent in a pressure-driven flow reactor
-
By exploiting the high surface to volume ratio obtained within continuous flow reactors, we are able to oxidise selectively an array of primary alcohols to either the aldehyde or carboxylic acid, depending on the flow rates employed, demonstrating a degree of reaction control unattainable in traditional stirred reactors.
- Wiles, Charlotte,Watts, Paul,Haswell, Stephen J.
-
p. 5261 - 5264
(2007/10/03)
-
- Direct coupling reaction between alcohols and silyl compounds: Enhancement of Lewis acidity of Me3SiBr using InCl3
-
The combination of InCl3 and Me3SiBr provided an enhanced Lewis acid system that can be used to promote a wide range of direct coupling reactions between alcohols and silyl nucleophiles in non-halogenated solvents, such as hexane or MeCN. The enhanced Lewis acidity of this system was measured by the 13C NMR in terms of the coordination to an alcohol. Moreover, the interaction between Me3SiBr and the In(III) species was revealed by 29Si NMR spectral analysis. Highly chemoselective allylations toward a hydroxyl moiety over ketone and acetoxy ones have been demonstrated.
- Saito, Takahiro,Nishimoto, Yoshihiro,Yasuda, Makoto,Baba, Akio
-
p. 8516 - 8522
(2007/10/03)
-