cas 2425-28-7, alpha-(bromomethyl)benzyl alcohol

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Buckles,Maurer
p. 1585,1587
(1953)
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An 18O-Labeling Study of the β-(Nitroxy)alkyl and β-(Trifluoroacetoxy)alkyl Radical Migrations: Further Examples of a 1,2-Shift Mechanism
The results of an 18O labeling study of the β-(nitroxy)alkyl and β-(trifluoroacetoxy)alkyl radical migrations are presented.Phenacyl bromide dimethyl acetal was hydrolyzed with H2(18)O water to give labelled phenacyl bromide and, following borohydride reduction, 18O labeled styrene bromohydrin.Nitration and trifluoroacetylation gave the radical precursors which were allowed to react with tributyltin hydride and AIBN in benzene at reflux.After cleavage to 2-phenylethanol, the rearrangement products were examined by GC-MS.The β-(nitroxy)alkyl migration is found to occur, in benzene to the extent of 64percent through a 1,2-, as opposed to a 2,3-shift, mechanism.The β-(trifluoroacetoxy)alkyl migration occurs 7percent by the 1,2-pathway.It is suggested that, in general, faster ester migrations occur to a greater extent through the 1,2-shift pathway.
Crich, David,Filzen, G. Frederick
p. 4834 - 4837
(1995)
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Metalated Ir–CNP Complexes Containing Imidazolin-2-ylidene and Imidazolidin-2-ylidene Donors – Synthesis, Structure, Luminescence, and Metal–Ligand Cooperative Reactivity
The iridium complex 1 based on a metalated CNP ligand containing an imidazolin-2-ylidene fragment has been prepared by treatment of the ligand precursor 4 with Ag2O followed by reaction with [IrCl(COE)2]2. The chlorohydride imidazolidin-2-ylidene complex 6, which is isostructural to 1, was synthetized by reaction of the previously reported dihydride derivative 3 with CH2Cl2. Complexes 1 and 6 exhibit luminescence arising from a 3MLCT/ILCT state involving the metalated CNP ligand, which is particularly intense for 1 in the solid state at 298 K. Furthermore, the reactivity of complexes 1 and 6 towards bases was compared. Deprotonation of 1 with KOtBu produced the selective formation of the dinuclear complex 7; meanwhile, the reaction of 6 led to a complex mixture of products. The same reactions carried out in the presence of PPh3 produced the selective deprotonation of the P-bonded methylene bridges of 1 and 6, yielding the isostructural derivatives 9 and 10. DFT calculations performed on the uNHC-containing tautomers I and II, and the sNHC-based isomers III and IV, showed that the NHC-deprotonated derivatives II and IV are more stable by 3.20 and 2.73 kcal mol–1, respectively, than their P-deprotonated counterparts (I and III). However, a reverse stability order was observed for hexacoordinated tautomers I·L and II·L, and III·L and IV·L (L = PPh3, CO, MeCN). Finally, the catalytic activity of complex 3 in the transfer hydrogenation of ketones has been assessed.
Hernández-Juárez, Martín,Sánchez, Práxedes,López-Serrano, Joaquín,Lara, Patricia,González-Herrero, Pablo,Rendón, Nuria,álvarez, Eleuterio,Paneque, Margarita,Suárez, Andrés
p. 3944 - 3953
(2020)
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A vanadium-dependent bromoperoxidase in the marine red alga Kappaphycus alvarezii (Doty) Doty displays clear substrate specificity
Bromoperoxidase activity was initially detected in marine macroalgae belonging to the Solieriaceae family (Gigartinales, Rhodophyta), including Solieria robusta (Greville) Kylin, Eucheuma serra J. Agardh and Kappaphycus alvarezii (Doty) Doty, which are important industrial sources of the polysaccharide carrageenan. Notably, the purification of bromoperoxidase was difficult because due to the coexistence of viscoid polysaccharides. The activity of the partially purified enzyme was dependent on the vanadate ion, and displayed a distinct substrate spectrum from that of previously reported vanadium-dependent bromoperoxidases of marine macroalgae. The enzyme was specific for Br- and I- ions and inactive toward F- and Cl-. The Km values for Br- and H2O2 were 2.5 × 10-3 M and 8.5 × 10-5 M, respectively. The halogenated product, dibromoacetaldehyde, that accumulated in K. alvarezii was additionally determined.
Kamenarska, Zornitsa,Taniguchi, Tomokazu,Ohsawa, Noboru,Hiraoka, Masanori,Itoh, Nobuya
p. 1358 - 1366
(2007)
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In situ NMR study of asymmetric borane reduction reaction - An abnormal factor in the temperature effect on the bis-oxazaborolidine catalyst and the relationship between the catalyst structure and selectivity
The relationship between the structure of the catalyst and the selectivity in the asymmetric borane reduction reaction of prochiral ketones is discussed. The variation of the catalyst itself at low temperature is observed by the in situ NMR method and the origin of the temperature effect of the reaction is proposed. It is concluded that the amount of the effective component of the catalyst present has an important effect on the enantioselectivity. Copyright (C) 2000 Elsevier Science Ltd.
Zhao, Jinkai,Bao, Xinhe,Liu, Xiumei,Wan, Boshun,Han, Xiuwen,Yang, Caiguang,Hang, Jiangfeng,Feng, Yan,Jiang, Biao
p. 3351 - 3359
(2000)
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A highly regio- and chemoselective synthesis of vicinal bromohydrins by ring opening of terminal epoxides with dibromoborane-dimethyl sulfide
Dibromoborane-dimethyl sulfide (BHBr2-SMe2) displays high degrees of chemo- and regioselectivity during the brominative cleavage of the epoxy group into vicinal bromohydrins in the presence of alkene, alkyne, allene, ether, acetal and acetonide, besides its hydroborating ability. Several reducible functional groups, such as chloride, aldehyde, ketone, azide, ester, nitrile and tert-amino ester, have been successfully accommodated during the epoxide opening process.
Roy, Chandra D.,Brown, Herbert C.
p. 1608 - 1613
(2007)
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New chiral borohydride based reducing agent: Asymmetric reduction of 9-anthryl trifluoromethyl ketone and other carbonyl compounds
(S)-(+)-2-(α-Hydroxybenzyl)benzimidazole and (S)-(-)-2-benzimidazole-1-ethanol were synthesised and converted to chiral borohydrides which reduced prochiral ketones to the corresponding chiral alcohols in high yields (80 to 100%, e.e. 42 to 95%). This is the first report of sodium borohydride modified by 1,2-amino alcohol.
Maiti, Dilip K.,Bhattacharya, Pranab K.
p. 99 - 108
(1998)
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Asymmetric hydrolysis of (dl)-1-acyloxy-2-halo-1-phenylethanes with lipases
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Kutsuki,Sawa,Hasegawa,Watanabe
p. 2369 - 2373
(1986)
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Enantioselective borane reduction of aromatic ketones catalyzed by chiral aluminum alkoxides
The asymmetric borane reduction of prochiral ketones with an alkoxide catalyst prepared in situ from aluminum tri-iso-propoxide and (R)-binaphthol was examined. Using these conditions, alcohols were obtained in high yield and e.e.'s of up to 83%.
Fu, I.-Pin,Uang, Biing-Jiun
p. 45 - 48
(2001)
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Unmasking the Hidden Carbonyl Group Using Gold(I) Catalysts and Alcohol Dehydrogenases: Design of a Thermodynamically-Driven Cascade toward Optically Active Halohydrins
A concurrent cascade combining the use of a gold(I) N-heterocyclic carbene (NHC) and an alcohol dehydrogenase (ADH) is disclosed for the synthesis of highly valuable enantiopure halohydrins in an aqueous medium and under mild reaction conditions. The meth
Escot, Lorena,González-Granda, Sergio,Gotor-Fernández, Vicente,Lavandera, Iván
p. 2552 - 2560
(2022/02/16)

Regio- and stereoselective synthesis of bromoalkenes by homolytic hydrobromination of alkynes with hydrogen bromide
Homolytic hydrobromination of terminal and internal alkynes with a commercially available solution of hydrogen bromide in acetic acid has been investigated for regio- and stereoselective synthesis of bromoalkenes. Under an aerobic atmosphere at room temperature, the reaction of ethynylarenes with a small excess of HBr efficiently gave (2-bromoethenyl)arenes with good to high E-selectivity. (Alk-1-ynyl)arenes, or internal alkynes bearing both phenyl and alkyl groups at the sp-carbons also underwent the air-initiated hydrobromination to exhibit high Z-selectivity under kinetic conditions using a half equivalent of HBr.
Kumaki, Wataru,Kinoshita, Hidenori,Miura, Katsukiyo
supporting information

(2022/03/07)

A General Method for the Dibromination of Vicinal sp3C-H Bonds Exploiting Weak Solvent-Substrate Noncovalent Interactions
A general procedure of 1,2-dibromination of vicinal sp3 C-H bonds of arylethanes using N-bromosuccinimide as the bromide reagent without an external initiator has been established. The modulation of the strength of the intermolecular noncovalent interactions between the solvent and arylethane ethanes, quantitatively evaluated via quantum chemical calculations, allows us to circumvent the fact that arylethane ethane cannot be dibrominated through traditional methods. The mechanism was explored by both experiments and quantum chemical calculations, revealing a radical chain with HAA process.
Qi, Zaojuan,Li, Weihe,Niu, Yanning,Benassi, Enrico,Qian, Bo
supporting information
p. 2399 - 2404
(2021/03/03)

Ruthenium complex based on [N,N,O] tridentate -2-ferrocenyl-2-thiazoline ligand for catalytic transfer hydrogenation
A method for the synthesis of a new phosphine-free [N,N,O]-tridentate Schiff base ligand L1 using the 2-Ferrocenyl-2-thiazoline as scaffold was developed. The 1,2-disubstituted ferrocene-based ligand was assembled using as key strategy the directed ortho-metalation (DoM) in 2-ferrocenyl-2-thiazoline. L1 was successfully obtained in 83% of overall yield after two-step synthesis. The coordination ability of L1 towards Ru(II) was evidenced and the resulting complex was characterized by IR, UV-vis and EPR. Its catalytic performance was tested in transfer hydrogenation of a variety of substrates giving moderate to excellent conversions.
Badillo-Gómez,Sánchez-Rodríguez,Toscano,Gouygou,Ortega-Alfaro,López-Cortés
(2020/12/14)

Chiral guanidine catalyzed acylative kinetic resolution of racemic 2-bromo-1-arylethanols
In this study, chiral guanidine catalyzed acylative kinetic resolution of racemic 2-bromo-1-arylethanols was achieved with high selectivity. Irrespective of the electronic nature and the substitution patterns on the aromatic rings, a variety of substrates were suitable for this reaction. The branched acyl component was considered to be optimal for obtaining high s-values. The transition state of the reaction was proposed based on the absolute configuration of the obtained product.
Sawada, Erika,Nakata, Kenya
supporting information
p. 371 - 373
(2021/03/16)

CeO2-nanocubes as efficient and selective catalysts for the hydroboration of carbonyl groups
The CeO2-nanoparticle catalysed hydroboration of carbonyl compounds with HBpin (pin = OCMe2CMe2O) is reported to afford the corresponding borate esters in excellent yield. A series of aromatic and aliphatic aldehydes and ketones having synthetically important functional groups were well-Tolerated under mild reaction conditions. Further, chemoselective hydroboration of aldehydes over other reducible functional groups such as ketone, nitrile, hydroxide, alkene, alkyne, amide, ester, nitro, and halides was achieved. Importantly the catalyst can be recycled up to ten runs with slight loss in activity. This journal is
Bhawar, Ramesh,Bose, Shubhankar Kumar,Patil, Kiran S.
p. 15028 - 15034
(2021/09/04)

Electrochemical bromofunctionalization of alkenes in a flow reactor
The bromination of organic molecules has been extensively studied to date, yet there is still a demand for safe and sustainable methodologies. Hazardous reagents, selectivity, low atom economy and waste production are the most persisting problems of brominating reagents. The electrochemical oxidation of bromide to bromine is a viable strategy to reduce waste by avoiding chemical oxidants. Furthermore, thein situgeneration of reactive intermediates minimizes the risk of hazardous reagents. In this work, we investigate the electrochemical generation of bromine from hydrobromic acid in a flow electrochemical reactor. Various alkenes could be converted to their corresponding dibromides, bromohydrines, bromohydrin ethers and cyclized products in good to excellent yields.
Seitz, Jakob,Wirth, Thomas
supporting information
p. 6892 - 6896
(2021/08/20)

Preparation method of styrene oxide
The invention discloses a preparation method of styrene oxide. Styrene is used as an initial raw material, and is subjected to bromination and saponification to obtain styrene oxide. According to the method, hydrogen peroxide is used as a main oxidant, and a hydrogen peroxide/sodium chlorate mixed oxidant is adopted, so that the situation that sodium chlorate is too strong in oxidability, and a large amount of phenyl-1, 2-dibromoethane, acetophenone and benzaldehyde byproducts are generated is avoided; in addition, a catalyst is added in the bromination process, so that the selectivity is improved, and the generation of phenyl glycol is reduced; the method is simple and convenient to operate, high in selectivity, few in side reaction, high in yield, high in product purity and suitable for domestic industrial production. The total yield reaches 89.0% or above, and the product purity reaches 99.0% or above.
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Paragraph 0017; 0031-0036; 0043-0045

(2021/06/06)

Alkene, Bromide, and ROH – How To Achieve Selectivity? Electrochemical Synthesis of Bromohydrins and Their Ethers
Bromohydrins and their ethers were electrochemically synthesized via hydroxy- and alkoxybromination of alkenes using potassium bromide and water or alcohols. High selectivity of bromohydrins formation was achieved only with the use of DMSO as the solvent and an acid as the additive. The proposed combination of starting reagents, additives, and solvents allowed to form bromohydrins or their ethers selectively despite the variety of side-products (epoxides, dibromides, diols). Bromohydrins were obtained in high yields, up to 96%, with a broad substrate scope in an undivided electrochemical cell equipped with glassy carbon and platinum electrodes at high current density. (Figure presented.).
Bityukov, Oleg V.,Nikishin, Gennady I.,Terent'ev, Alexander O.,Vil', Vera A.
supporting information
p. 3070 - 3078
(2021/05/10)

Visible light-mediated metal-free double bond deuteration of substituted phenylalkenes
Various bromophenylalkenes were reductively photodebrominated by using 1,3-dimethyl-2-phenyl-1H-benzo-[d]imidazoline (DMBI) and 9,10-dicyanoanthracene. With deuterated DMBI analogs (the most effective was DMBI-d11), satisfactory to excellent isotopic yields were obtained. DMBI-d11 could also be regenerated from the reaction mixtures with a recovery rate of up to 50%. The combination of the photodebromination reaction with conventional methods for bromoalkene synthesis enables sequential monodeuteration of a double bond without the necessity of a metal catalyst. This journal is
Iakovenko, Roman,Hlavá?, Jan
supporting information
p. 440 - 446
(2021/01/28)

Chiral salen - Ni (II) based spherical porous silica as platform for asymmetric transfer hydrogenation reaction and synthesis of potent drug intermediate montekulast
Heterogeneous catalyst has an edge over homogeneous systems in terms of recyclability, activity, stability and recovery. Silica has evolved as a good support material in heterogeneous systems due to its stability and ability to get modified as per the end application. Herein, we report a novel chiral Ni-Schiff base derived catalyst and its immobilization into mesoporous silica which was synthesized by post-grafting process. The chiral catalyst demonstrated remarkably high catalytic activity, enantioselectivity (up to 99 % enantiomers excess) for heterogeneous asymmetric transfer hydrogenation of various ketones. The developed catalyst was characterized by Ultraviolet-visible spectroscopy (UV–vis), Fourier-Transform Infrared spectroscopy (FT-IR), X-ray Powder Diffraction (XRD), Brunauer-Emmett-Teller (BET isotherm), Scanning Electron Microscopy – Energy Dispersive X-ray Spectroscopy (SEM-EDX), High Resolution – Transmission Electron Microscopy (HR-TEM), Vibrating Sample Magnetometer (VSM), X-ray Photoelectron Spectroscopy (XPS) and elemental analysis. The catalyst could be recovered and reused for multiple consecutive runs without losing the enantioselectivity. The chiral catalyst was used in asymmetric transfer hydrogenation reaction for synthesizing enantiomerically pure drug intermediate Montekulast.
Shukla, Meenakshi,Barick,Salunke,Chandra, Sudeshna
(2021/02/05)

Biomimetic Oxidative Bromination by cis-Dioxidotungsten(VI) Complexes of Salan Type N,N’-Capped Linear Tetradentate Amino Bisphenol
Reaction of [WVIO2(acac)2] (Hacac=acetylacetone) with salan-type dibasic tetradentate ONNO donor Mannich bases derived from ethylenediamine, formaldehyde and 2,4-di-tert-butylphenol (H2L1), 2-tert-butyl-4-methylphenol (H2L2), 2,4-dimethylphenol (H2L3) and 2,4-dichlorophenol (H2L4) in a 1 : 1 ([WVIO2(acac)2] : H2L) molar ratio in refluxing MeOH gave the corresponding cis-dioxidotungsten(VI) complexes [WVIO2L1] (1), [WVIO2L2] (2), [WVIO2L3] (3) and [WVIO2L4] (4), respectively. Characterization by elemental analysis, various spectroscopic (FT-IR, UV-vis, 1H and 13C NMR) studies, DFT calculations and single-crystal X-ray analysis of 2 and 3 suggest six-coordinated octahedral α-cis (symmetric) isomeric form of the complexes where ligands coordinate through the two phenolate oxygen and two amine nitrogen atoms (in a cis-α type symmetric binding mode) with one of the N atoms of the ligand and one of the terminal O atoms of the cis-WO2 group in the axial position. These complexes are potential catalyst precursors for the oxidative bromination of thymol and styrene. Thymol upon bromination gave three products, namely, 2-bromothymol, 4-bromothymol, and 2,4-dibromothymol; later one being the major product. Oxidative bromination of styrene resulted in 2-bromo-1-phenylethanol and 1-phenylethane-1,2-diol; the later one is the result of nucleophilic attack of water on the α as well as β carbons both of the initially formed 1,2-dibromo-1-phenylethane.
Maurya, Mannar R.,Maurya, Shailendra K.,Kumar, Naveen,Gupta, Puneet
p. 2724 - 2738
(2021/06/18)

Lipase mediated enzymatic kinetic resolution of phenylethyl halohydrins acetates: A case of study and rationalization
Racemic phenylethyl halohydrins acetates containing several groups attached to the aromatic ring were resolved via hydrolysis reaction in the presence of lipase B from Candida antarctica (Novozym 435). In all cases, the kinetic resolution was highly selective (E > 200) leading to the corresponding (S)-β-halohydrin with ee > 99 %. However, the time required for an ideal 50 % conversion ranged from 15 min for 2,4-dichlorophenyl chlorohydrin acetate to 216 h for 2-chlorophenyl bromohydrin acetate. Six chlorohydrins and five bromohydrins were evaluated, the latter being less reactive. For the β-brominated substrates, steric hindrance on the aromatic ring played a crucial role, which was not observed for the β-chlorinated derivatives. To shed light on the different reaction rates, docking studies were carried out with all the substrates using MD simulations. The computational data obtained for the β-brominated substrates, based on the parameters analysed such as NAC (near attack conformation), distance between Ser-O and carbonyl-C and oxyanion site stabilization were in agreement with the experimental results. On the other hand, the data obtained for β-chlorinated substrates suggested that physical aspects such as high hydrophobicity or induced change in the conformation of the enzymatic active site are more relevant aspects when compared to steric hindrance effects.
Fonseca, Thiago de Sousa,Vega, Kimberly Benedetti,da Silva, Marcos Reinaldo,de Oliveira, Maria da Concei??o Ferreira,de Lemos, Telma Leda Gomes,Contente, Martina Letizia,Molinari, Francesco,Cespugli, Marco,Fortuna, Sara,Gardossi, Lucia,de Mattos, Marcos Carlos
(2020/02/18)

Characterization of a robust glucose 1-dehydrogenase, SyGDH, and its application in NADPH regeneration for the asymmetric reduction of haloketone by a carbonyl reductase in organic solvent/buffer system
To realize coenzyme regeneration in the reduction of haloketones, a codon-optimized gene Sygdh encoding glucose 1-dehydrogenase (SyGDH) was synthesized based on the putative GDH gene sequence (Ta0897) in Thermoplasma acidophilum genomic DNA, and expressed in E. coli BL21(DE3). Recombinant SyGDH was purified to homogeneity by affinity chromatography with the specific activity of 86.3 U/mg protein towards D-glucose at the optimum pH and temperature of 7.5 and 40 °C. It was highly stable in a pH range of 4.5–8.0 and at 60 °C or below, and resistant to various organic solvents. The Km and catalytic efficiency (kcat/Km) of SyGDH towards NADP+ were 0.67 mM and 104.0 mM?1 s?1, respectively, while those towards NAD+ were 157.9 mM and 0.64 mM?1 s?1, suggesting that it preferred NADP+ as coenzyme to NAD+. Additionally, using whole cells of E. coli/Sygdh-Sys1, coexpressing SyGDH and carbonyl reductase (SyS1), as the biocatalyst, the asymmetric reduction of 60 mM m-chlorophenacyl chloride coupled with the regeneration of NADPH in situ was conducted in DMSO/phosphate buffer (2:8, v/v) system, producing (R)-2-chloro-1-(3-chlorophenyl)ethanol with over 99.9% eep and 99.2% yield. Similarly, the reduction of 40 mM α-bromoacetophenone in n-hexane/buffer (6:4, v/v) biphasic system produced (S)-2-bromo-1-phenylethanol with over 99.9% eep and 98.3% yield.
Hu, Die,Wen, Zheng,Li, Chuang,Hu, Bochun,Zhang, Ting,Li, Jianfang,Wu, Minchen
p. 55 - 62
(2019/11/26)

Asymmetric Catalytic Meerwein-Ponndorf-Verley Reduction of Ketones with Aluminum(III)-VANOL Catalysts
We report herein an efficient aluminum-catalyzed asymmetric MPV reduction of ketones with broad substrate scope and excellent yields and enantiomeric inductions. A variety of aromatic (both electron-poor and electron-rich) and aliphatic ketones were converted to chiral alcohols in good yields with high enantioselectivities (26 examples, 70-98percent yield and 82-99percent ee). This method operates under mild conditions (-10 °C) and low catalyst loading (1-5 mol percent). Furthermore, this process is catalyzed by the earth-abundant main-group element aluminum and employs 2-propanol as the hydride source.
Guan, Yong,Mohammadlou, Aliakbar,Staples, Richard,Sullivan, Ryan P.,Wulff, William D.,Yin, Xiaopeng,Zheng, Li
p. 7188 - 7194
(2020/07/21)

One-pot synthesis of 4-aryl-2-aminothiazoles from styrenes and thioureas promoted by tribromoisocyanuric acid
A simple and efficient one-pot protocol has been developed for the conversion of styrenes into 4-aryl-2-aminothiazoles using readily available starting materials. Tribromoisocyanuric acid was successfully used for the co-bromination and oxidation of styrenes to give phenacyl bromides, which in the presence of thioureas produced the corresponding 4-aryl-2-aminothiazoles in 48–70% yield. The protocol involves three reactions in one process: a tandem (formation of phenacyl bromides from styrenes) followed by a telescoped (conversion to thiazole) reaction.
de Andrade, Vitor S.C.,de Mattos, Marcio C.S.
supporting information

(2020/07/03)

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
(2019/05/16)

Formate Oxidase (FOx) from Aspergillus oryzae: One Catalyst Enables Diverse H2O2-Dependent Biocatalytic Oxidation Reactions
An increasing number of biocatalytic oxidation reactions rely on H2O2 as a clean oxidant. The poor robustness of most enzymes towards H2O2, however, necessitates more efficient systems for in situ H2O2 generation. In analogy to the well-known formate dehydrogenase to promote NADH-dependent reactions, we here propose employing formate oxidase (FOx) to promote H2O2-dependent enzymatic oxidation reactions. Even under non-optimised conditions, high turnover numbers for coupled FOx/peroxygenase catalysis were achieved.
Tieves, Florian,Willot, Sébastien Jean-Paul,van Schie, Morten Martinus Cornelis Harald,Rauch, Marine Charlène Renée,Younes, Sabry Hamdy Hamed,Zhang, Wuyuan,Dong, JiaJia,Gomez de Santos, Patricia,Robbins, John Mick,Bommarius, Bettina,Alcalde, Miguel,Bommarius, Andreas Sebastian,Hollmann, Frank
supporting information
p. 7873 - 7877
(2019/05/10)

Cascade bio-hydroxylation and dehalogenation for one-pot enantioselective synthesis of optically active β-halohydrins from halohydrocarbons
A stereoselective hydroxylation and enantioselective dehalogenation cascade reaction was developed for the synthesis of optically active β-haloalcohols from halohydrocarbons. This cascade system employed P450 and halohydrin dehalogenase as two compatible biocatalysts, allowing a straightforward, greener and efficient access to β-halohydrins with excellent enantioselectivities (98-99%).
Cui, Hai-Bo,Xie, Ling-Zhi,Wan, Nan-Wei,He, Qing,Li, Zhi,Chen, Yong-Zheng
supporting information
p. 4324 - 4328
(2019/08/21)

Asymmetric synthesis of α-bromohydrins by carrot root as biocatalyst and conversion to enantiopure β-hydroxytriazoles and styrene oxides using click chemistry and SN2 ring-closure
In this study we have combined the bioreduction of α-bromoketones using carrot root as biocatalyst and click chemistry for the preparation of enantiopure β-hydroxytriazoles in excellent enantiomeric excesses and yields. Moreover, we have utilized chiral α-halohydrins for the synthesis of enantiopure styrene oxides in very good yields and enantiomeric excesses. Structural assignments of the products were based on their 1H and 13C NMR data and their optical rotations. The enantiomeric excess of the chiral products was obtained by HPLC analysis.
Hosseinzadeh, Rahman,Mohadjerani, Maryam,Mesgar, Sakineh
p. 583 - 591
(2019/02/17)

Asymmetric transfer hydrogenation of ketones using Ru(0) nanoparticles modified by Chiral Thiones
The catalytic asymmetric transfer hydrogenation (ATH) of acetophenone in isopropanol by Ru(0) nanoparticles (NPs) obtained by the in-situ reduction of Ru (II) half-sandwich complexes of chiral 2-oxazolidinethiones and 2-thiozolidinethiones was examined and compared with the catalytic activity of Ru(0) NPs formed in-situ by the reduction of [Ru(p-cymene)(Cl)2]2 in presence of optically active ligands such as (S)-4-isobutylthiazolidine-2-thione, (S)-4-Isopropyl-2(?2-pyridinyl)-2-oxazoline, (8S, 9R)-(?)-cinchonidine, (S)-leucinol, (S)-phenylalaninol, and (S)-leucine. Three of the best catalytic systems were then examined for ATH of thirteen aromatic ketones with different electronic and steric properties. A maximum of 24% ee was obtained using NPs generated from the Ru (II) half-sandwich complex with (S)-4-isobutylthiazolidine-2-thione in the TH of acetophenone. The NPs were characterized by TEM and DLS measurements. Kinetic studies and poisoning experiments confirmed that the reaction is catalyzed by the chiral NPs formed in-situ. Complete characterization of the complexes, including the X-ray crystallographic characterization of two complexes, was also carried out.
Din Reshi, Noor U.,Senthurpandi, Dineshchakravarthy,Samuelson, Ashoka G.
(2019/03/21)

Two enantiocomplementary ephedrine dehydrogenases from arthrobacter sp. TS-15 with broad substrate specificity
The recently identified pseudoephedrine and ephedrine dehydrogenases (PseDH and EDH, respectively) from Arthrobacter sp. TS-15 are NADH-dependent members of the oxidoreductase superfamily of short-chain dehydrogenases/reductases (SDRs). They are specific for the enantioselective oxidation of (+)-(S) N-(pseudo)ephedrine and (-)-(R) N-(pseudo)ephedrine, respectively. Anti-Prelog stereospecific PseDH and Prelog-specific EDH catalyze the regio- A nd enantiospecific reduction of 1-phenyl-1,2-propanedione to (S)-phenylacetylcarbinol and (R)-phenylacetylcarbinol with full conversion and enantiomeric excess of >99%. Moreover, they perform the reduction of a wide range of aryl-aliphatic carbonyl compounds, including ketoamines, ketoesters, and haloketones, to the corresponding enantiopure alcohols. The highest stability of PseDH and EDH was determined to be at a pH range of 6.0-8.0 and 7.5-8.5, respectively. PseDH was more stable than EDH at 25 °C with half-lives of 279 and 38 h, respectively. However, EDH is more stable at 40 °C with a 2-fold greater half-life than at 25 °C. The crystal structure of the PseDH-NAD+ complex, refined to a resolution of 1.83 ?, revealed a tetrameric structure, which was confirmed by solution studies. A model of the active site in complex with NAD+ and 1-phenyl-1,2-propanedione suggested key roles for S143 and W152 in recognition of the substrate and positioning for the reduction reaction. The wide substrate spectrum of these dehydrogenases, combined with their regio- A nd enantioselectivity, suggests a high potential for the industrial production of valuable chiral compounds.
Shanati, Tarek,Lockie, Cameron,Beloti, Lilian,Grogan, Gideon,Ansorge-Schumacher, Marion B.
p. 6202 - 6211
(2019/08/15)

In vitro cytotoxicity and catalytic evaluation of dioxidovanadium(v) complexes in an azohydrazone ligand environment
Three new anionic dioxidovanadium(v) complexes (HNEt3)[VO2(L)1-3] (1-3) of tridentate binegative aroylhydrazone ligands containing the azobenzene moiety were synthesized and structurally characterized. The aroylhydrazone ligands (H2L1-3) were derived from the condensation of 5-(arylazo) salicylaldehyde derivatives with the corresponding aroyl hydrazides. All the synthesized ligands and metal complexes were successfully characterized by several physicochemical techniques, namely, elemental analysis, electrospray ionization mass spectrometry, spectroscopic methods (IR, UV-vis and NMR), and cyclic voltammetry. Single-crystal X-ray diffraction crystallography of 1-3 revealed five-coordinate geometry, where the ligand coordinates to the metal centre in a binegative tridentate O, N, O coordinating anion and two oxido-O atoms, resulting in distortion towards the square pyramidal structure. The complexes were further evaluated for their in vitro cytotoxicity against HeLa and HT-29 cancer cell lines. All the complexes manifested a cytotoxic potential that was found to be comparable with that of clinically referred drugs, while complex 3 proved to be the most cytotoxic among the three complexes for both cell lines, which may be due to the synergistic effect of the naphthyl substituent in the azohydrazone ligand environment coordinated to the vanadium metal. The synthesized complexes 1-3 were probed as catalysts for the oxidative bromination of thymol and styrene as a functional mimic of vanadium haloperoxidases (VHPOs). All the reactions provided high percentages of conversion (>90%) with a high turnover frequency (TOF) in the presence of the catalysts 1-3. In particular, for the oxidative bromination of thymol, the percentage of conversion and TOF were in the ranges of 98-99% and 5380-7173 (h-1), respectively. Besides, 3 bearing the naphthyl substituent showed the highest TOF among all the complexes for the oxidative bromination of both thymol and styrene.
Mohanty, Monalisa,Maurya, Shailendra K.,Banerjee, Atanu,Patra, Sushree Aradhana,Maurya, Mannar R.,Crochet, Aurélien,Brzezinski, Krzysztof,Dinda, Rupam
supporting information
p. 17680 - 17695
(2019/11/26)

Synthesis, characterization and catalytic activity of dioxidouranium(VI) complexes of ONNO tetradentate Mannich bases
The reaction of dibasic tetradentate ONNO donor Mannich bases, derived from ethylenediamine and 2,4–di–tert–butylphenol (H2L1) (I), 2,4–di–methylphenol (H2L2) (II), 2–tert–butyl–4–methylphenol (H2L3) (III) and 2,4–di–chlorophenol (H2L4) (IV), with UVIO2(MeCOO)2·2H2O in a 1:1 M ratio in refluxing MeOH gave the corresponding mononuclear trans-dioxidouranium(VI) complexes of the type trans-[UVIO2L(MeOH)] (H2L = H2L1 to H2L4) (1–4). The synthesized complexes are stable in air, reddish-brown in color and soluble in most solvents. These complexes are characterized by elemental analysis, various spectroscopic (FT-IR, UV/Vis, 1H and 13C NMR) techniques and single-crystal X-ray analysis of 3 and 4. The complexes adopt distorted pentagonal bipyramidal geometry around the metal centre. The ligand acts as tetradentate, coordinating through two phenolato oxygen and two imino nitrogen atoms; two oxido groups are trans to each other. These complexes are used as catalysts to study the oxidative bromination of thymol and styrene. The catalytic oxidative bromination of thymol resulted in the formation of three products namely, 2-bromothymol, 4-bromothymol and 2,4-dibromothymol while oxidative bromination of styrene gave two products, 2-bromo-1-phenylethane-1-ol and 1-phenylethane-1,2-diol. In order to find out the optimized reaction conditions for the fixed concentration (10 mmol) of substrate, effects of different amounts of catalyst, KBr, HClO4, and oxidant (H2O2) have been investigated. Under the optimized reaction conditions, all the complexes have shown good catalytic potentials for the oxidative bromination of substrates, establishing the functional similarity to vanadium dependent haloperoxidases. Changes in the UV–visible absorption spectra of dioxidouranium(VI) complexes upon addition of H2O2 suggest the formation of the corresponding oxidoperoxidouranium(VI) complexes.
Avecilla, Fernando,Maurya, Mannar R.,Maurya, Shailendra K.,Mengesha, Bekele
supporting information
p. 118 - 126
(2019/06/28)

Exploring the Biocatalytic Scope of a Novel Enantioselective Halohydrin Dehalogenase from an Alphaproteobacterium
A gene encoding halohydrin dehalogenase from an alphaproteobacterium (AbHHDH) was identified, cloned and over-expressed in Escherichia coli. AbHHDH was able to catalyze the stereoselective dehalogenation of prochiral and racemic halohydrins. It showed the highest enantioselectivity in the dehalogenation of 20?mM (R,S)-2-bromo-1-phenylethanol, which yielded (S)-2-bromo-1-phenylethanol with 99% ee and 34.5% yield. Moreover, AbHHDH catalyzed the azidolysis of epoxides with low to moderate (S)-enantioselectivity. The highest enantioselectivity (E = 18.6) was observed when (R,S)-benzyl glycidyl ether was used as the substrate. A sequential kinetic resolution catalyzed by HHDH was employed for the synthesis of chiral 1-chloro-3-phenoxy-2-propanol. We prepared enantiopure (S)-isomer with a high enantiopurity of ee > 99% and a yield of 30.7% (E-value: 21.3) by kinetic resolution of 20?mM substrate. The (S)-isomer with 99% ee readily obtained from 40 to 150?mM (R,S)-1-chloro-3-phenoxy-2-propanol. Taken together, the results of this study demonstrate the applicability of this HHDH for the production of optically active compounds. [Figure not available: see fulltext.].
Xue, Feng,Ya, Xiangju,Xiu, Yuansong,Tong, Qi,Wang, Yuqi,Zhu, Xinhai,Huang, He
p. 629 - 637
(2019/01/25)

Tandem transfer hydrogenation-epoxidation of ketone substrates catalysed by alkene-tethered Ru(ii)-NHC complexes
A series of nine cyclopentadienyl Ru(ii)-NHC complexes (1-9) have been synthesised by systematically varying the ligand and/or ligand substituents: η5-C5H4R′ (R′ = H, Me), EPh3 (E = P, As), NHC (Im, BIm), where NHC = Im(R)(R′) (R, R′ = Me, Bn, 4-NO2Bn, C2H4Ph, C4H7). Each of the Ru(ii)-NHC complexes features an N-alkenyl tether to attain bidentate NHC ligands. All complexes found application as catalysts in the tandem transfer hydrogenation and epoxidation reactions of carbonyl substrates. The catalytic activity of the complexes was shown to be similar, with efficiencies of up to 69% conversion after 18 hours and varying alcohol:epoxide selectivity for a variety of electronically diverse carbonyl substrates. Complex 3, with a nitro-containing substituent on the NHC ligand, was the only complex that showed preference for the alcohol product over the epoxide after 18 hours of reaction time.
Malan, Frederick P.,Singleton, Eric,Van Rooyen, Petrus H.,Landman, Marilé
supporting information
p. 8472 - 8481
(2019/06/14)

Oxidative β-Halogenation of Alcohols: A Concise and Diastereoselective Approach to Halohydrins
β-Halohydrins bearing transformable halo- and hydroxyl groups, are easily converted into various valuable blocks in organic and pharmaceutical synthesis. A diastereoselective β-halogenation of benzylic alcohols was achieved under simple and low-cost conditions, which provided a direct synthesis of β-halohydrins. The simple reaction conditions, easily available reagents, high diastereoselectivities, and additional oxidant-free make this reaction very attractive and practical.
Ai, Lingsheng,Wang, Weijin,Wei, Jialiang,Li, Qing,Song, Song,Jiao, Ning
p. 437 - 441
(2019/02/26)

A new entry of highly selective and nucleophilic BrH2C-and CLH2c-titanium complexes for carbonyl coupling
The direct coupling of various aldehydes and ketones with CH2Br2 or CH2Cl2 promoted by TiCl4-Mg bimetallic complex provides an extremely simple, practical, and efficient approach for the construction of bromomethyl or chloromethyl carbinols. The high chemoselectivity of this chemistry is illus-trated by the TiCl4-Mg-promoted selective coupling of CH2Br2 or CH2Cl2 with an aldehyde in the presence of ketone and selective transfer of CH2Br or CH2Cl to saturated carbonyl moiety. This protocol is also suitable for sterically hindered and enoliza-ble carbonyl compounds.
Yan, Tu Hsin,Ananthan, Bakthavachalam,Chang, Su Haur
p. 778 - 787
(2019/01/24)

A mechanistic study of transfer hydrogenation catalyzed by cyclometallated ruthenium half-sandwich complexes
Transfer hydrogenation of aromatic ketones catalyzed by eight cyclometallated ruthenium half-sandwich complexes, including three new complexes, was examined. The catalytic process was studied using different ratios of substrate to base and base to catalyst and using a deuterated reductant. Optimum conditions for catalysis were shown to be in the presence of higher amounts of base in refluxing isopropanol. Under these conditions, the complexes were reduced in situ to give Ru(0) nanoparticles invisible to the naked eye. The nanoparticles were characterized by TEM, DLS and XPS. The catalytic transfer hydrogenation, under conditions in which nanoparticles were generated, was found to be far greater than the transfer hydrogenation by the molecular catalyst. Complete characterization of the three new complexes, including the X-ray crystallographic characterization of these complexes was carried out.
Din Reshi, Noor U.,Senthurpandi, Dineshchakravarthy,Samuelson, Ashoka G.
p. 189 - 199
(2018/05/04)

Efficient hydroboration of carbonyls by an iron(II) amide catalyst
An easily prepared iron(ii) amide precatalyst enables the selective hydroboration of carbonyls with HBpin (pinacolborane) in the absence of any additive. The reactions proceed with low catalytic loading (1-3 mol%) under mild reaction conditions and display wide functional group compatibility. Aldehydes are selectively hydroborated in the presence of other reducible functional groups, such as ketones, alkenes, nitriles, esters, amides, acids and halides.
Baishya, Ashim,Baruah, Swavalina,Geetharani
p. 9231 - 9236
(2018/07/29)

Mild and Efficient Vicinal Dibromination of Olefins Mediated by Aqueous Ammonium Fluoride
A mild and efficient vicinal dibromination of olefins has been developed by using saturated aqueous ammonium fluoride solution as the promoter. Inexpensive and commercially available N -bromosuccinimide (NBS) was used as the brominating reagent. The corresponding vicinal dibromoalkanes could be obtained in good to excellent yields.
Ng, Wing Hin,Shing, Tony K. M.,Yeung, Ying-Yeung
supporting information
p. 419 - 424
(2018/02/23)

Immobilized and free cells of geotrichum candidum for asymmetric reduction of ketones: Stability and recyclability
Marine-derived fungus Geotrichum candidum AS 2.361 was previously reported by our group as an active strain for the enantioselective reduction of ketones. Although some other Geotrichum strains were also found from the terrestrial sources, information on their stability and reusability is scarce. Herein, the stabilities—in terms of pH tolerance, thermostability, and storage stability, and reusability—of G. candidum AS 2.361 were described for the asymmetric reduction of a series of aromatic ketones. Two differently immobilized cells (agar immobilization and calcium alginate immobilization) as well as free cells were prepared. For three substrates (1-(3-bromophenyl) ethan-1-one (1b), 1-(2-chlorophenyl) ethan-1-one (1d), and acetophenone (1g)) immobilized cells on agar showed a great improvement in the bioreduction activities compared to the free cells, increasing yields up to 97% with ee values of 99%. Cells immobilized on agar/calcium alginate could maintain more than 90% of the original activities within the assayed pH ranges of 3.5–11, while free cells were highly sensitive to alkaline and acidic conditions. Concerning thermostability, immobilized cells on agar kept 99% of their original activities after incubation at 60?C for 1 h, while almost no activity was detected for the free cells under the same condition. Immobilized cells were stable at 4?C for 80 days without any activity loss, while free cells started to decrease the activity after storage at 4?C for six days. The immobilized cells retained almost 99% activity after four reuse cycles, while free cells lost almost all the activities at on the third cycle.
Liu, Hui,de Souza, Fayene Zeferino Ribeiro,Liu, Lan,Chen, Bi-Shuang
(2018/09/10)

OsXCl(phosphine)2(diamine) and OsXCl(diphosphine)(diamine) (X = Cl, H) Complexes for Ketone Hydrogenation
The osmium complex trans-[OsCl2(PPh3)2(en)] (2) was prepared by reaction of [OsCl2(PPh3)3] (1a) with ethylenediamine (en), whereas the diphosphine derivatives trans-[OsCl2(dppf)(NN)] (NN = en (3), bn (4; bn = 1,4-butanediamine)) and trans-[OsCl2(dpbp)(en)] (5) were obtained from 1a, dppf or dpbp, and the corresponding NN ligand in CH2Cl2 or toluene. An X-ray diffraction study has been provided for 3. The isolation of the chiral derivatives trans-[OsCl2(diphosphine)((R,R)-dpen)] (diphosphine = dppf (6), dpbp (7), (R,R)-skewphos (8)) was achieved by reacting 1a with the diphosphine and (R,R)-dpen in toluene. Treatment of the precursor [Os2Cl4(P(m-tolyl)3)5] (1b) with en afforded [OsCl2(P(m-tolyl)3)2(en)] (9), while reaction of 1b with dppb and N,N-dmen gave [OsCl2(dppb)(N,N-dmen)] (10). The chiral derivatives [OsCl2(diphosphine)(NN)] (11-21; diphosphine = (S)-MeObiphep, (R)-MeObiphep, (R)-xylMeObiphep, (R)-binap, (S)-xylbinap, (R)-xylbinap, (R,S)-Josiphos NN = en, (R,R)-dpen, (R)-daipen, (R,R)-dppn) were prepared from 1b and the corresponding diphosphine and NN ligands in toluene. The monohydride trans-[OsHCl(P(m-tolyl)3)2(en)] (22) was synthesized by reaction of 1b with H2 (1 atm) in the presence of NEt3, followed by addition of en in toluene. Similarly, trans-[OsHCl(dppf)(en)] (23) was synthesized from 1a, H2, and NEt3, followed by treatment with dppf and en. Complexes 2-5, 9, 10, 22, and 23 efficiently catalyzed the hydrogenation of acetophenone with H2 under low pressure (5 atm) at 60-70 °C in ethanol (1-2 mol % of NaOEt) with the ratio S/C = 5000-10000. The chiral derivatives 6-8 and 11-21 afforded the asymmetric hydrogenation of acetophenone with up to 90% ee by combining bulky xylyl-substituted MeObiphep or binap-type ligands with (R)-daipen or (R,R)-dpen ligands. Catalytic transfer hydrogenation of acetophenone was observed with 3, 6, and 7 (S/C = 2000) in 2-propanol and in the presence of NaOiPr (2 mol %) at 60-82 °C.
Barbato, Cinzia,Baldino, Salvatore,Ballico, Maurizio,Figliolia, Rosario,Magnolia, Santo,Siega, Katia,Herdtweck, Eberhardt,Strazzolini, Paolo,Chelucci, Giorgio,Baratta, Walter
p. 65 - 77
(2018/01/17)

Molecular Basis for the High Activity and Enantioselectivity of the Carbonyl Reductase from Sporobolomyces salmonicolor toward α-Haloacetophenones
In an effort to develop a practical method for the synthesis of optically pure 2,2,2-trifluoro-1-phenylethanol, we found that the carbonyl reductase (SSCR) from Sporobolomyces salmonicolor showed excellent activity and enantioselectivity toward the halogenated acetophenones. Especially, SSCR exhibited more than 1000 times higher activity toward α,α,α-trifluoroacetophenone than unsubstituted acetophenone, a strikingly different observation from the previously well-studied alcohol dehydrogenase (LBADH) from Lactobacillus brevis. Enzyme-substrate docking and site-directed mutagenesis studies revealed the molecular basis for the high enzyme activity and enantioselectivity of SSCR toward the α-halogenated acetophenones. The hydrogen bond of the Asn207 side chain with the substrate halogen atom and the XH/π interaction of the substrate phenyl group with the side chains of Ser222/Thr223 resulted in the formation of the highly reactive conformation of α-halogenated acetophenones in the active site of the enzyme. (S)-2,2,2-Trifluoro-1-phenylethanol was prepared in excellent isolated yield and enantiomeric excess from the reduction of α,α,α-trifluoroacetophenone with mutant T209A. These results suggest that tuning the interactions between the halogen atoms/phenyl group of the substrate and the amino acid residues of the enzyme would lead to valuable mutants for the practical synthesis of β-haloalcohols.
Chen, Xi,Zhang, Hongliu,Feng, Jinhui,Wu, Qiaqing,Zhu, Dunming
p. 3525 - 3531
(2018/04/14)

Iridium-Catalyzed Asymmetric Hydrogenation of Halogenated Ketones for the Efficient Construction of Chiral Halohydrins
Iridium-catalyzed asymmetric hydrogenation of prochiral halogenated ketones was successfully developed to prepare various chiral halohydrins with high reactivities and excellent enantioselectivities under basic reaction condition (up to >99% conversion, 99% yield, >99% ee). Moreover, gram-scale experiment was performed well in the presence of just 0.005 mol% (S/C=20 000) Ir/f-amphox catalyst with 99% yield and >99% ee. (Figure presented.).
Yin, Congcong,Wu, Weilong,Hu, Yang,Tan, Xuefeng,You, Cai,Liu, Yuanhua,Chen, Ziyi,Dong, Xiu-Qin,Zhang, Xumu
supporting information
p. 2119 - 2124
(2018/04/30)

Immobilization of Amano lipase from Pseudomonas fluorescens on silk fibroin spheres: an alternative protocol for the enantioselective synthesis of halohydrins
The search for a new, efficient, cheaper and sustainable matrix for lipase immobilization is a growing area in biotechnology. Amano lipase from Pseudomonas fluorescens was immobilized on silk fibroin spheres and used in the enzymatic kinetic resolution of halohydrins, to obtain optically active epoxides (up to 99% ee), important precursors in the synthesis of derivative antifungal azoles. This paper reinforces the versatility of silk fibroin as a support for heterogeneous catalysts.
Ferreira, Irlon M.,Yoshioka, Sergio A.,Comasseto, Jo?o V.,Porto, André L. M.
p. 12650 - 12658
(2017/03/11)

Extreme halophilic alcohol dehydrogenase mediated highly efficient syntheses of enantiopure aromatic alcohols
Enzymatic synthesis of enantiopure aromatic secondary alcohols (including substituted, hetero-aromatic and bicyclic structures) was carried out using halophilic alcohol dehydrogenase ADH2 from Haloferax volcanii (HvADH2). This enzyme showed an unprecedented substrate scope and absolute enatioselectivity. The cofactor NADPH was used catalytically and regenerated in situ by the biocatalyst, in the presence of 5% ethanol. The efficiency of HvADH2 for the conversion of aromatic ketones was markedly influenced by the steric and electronic factors as well as the solubility of ketones in the reaction medium. Furthermore, carbonyl stretching band frequencies ν (CO) have been measured for different ketones to understand the effect of electron withdrawing or donating properties of the ketone substituents on the reaction rate catalyzed by HvADH2. Good correlation was observed between ν (CO) of methyl aryl-ketones and the reaction rate catalyzed by HvADH2. The enzyme catalyzed the reductions of ketone substrates on the preparative scale, demonstrating that HvADH2 would be a valuable biocatalyst for the preparation of chiral aromatic alcohols of pharmaceutical interest.
Alsafadi, Diya,Alsalman, Safaa,Paradisi, Francesca
p. 9169 - 9175
(2017/11/15)

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)

Activation of (salen)CoI complex by phosphorane for carbon dioxide transformation at ambient temperature and pressure
We report the activation of (salen)CoI complex 3g by a phosphorane to form a bifunctional catalyst for the reaction of carbon dioxide with terminal epoxides or aziridines at ambient temperature and 1 bar carbon dioxide pressure. Only 1.0 mol% of both (salen)CoI 3g and phosphorane 4d are required for cyclic carbonate synthesis, and the catalyst loading could even be lowered down to 0.1 mol%. Under these conditions, no polycarbonate formation is detected by NMR analysis. It is proposed that the high efficiency originates from the activation of (salen)CoI by a phosphorane to form a phosphorane-salen Co(iii) complex with enhanced Lewis acidity for the electrophilic activation while generating an iodide anion as a Lewis base co-catalyst to facilitate the ring-opening of epoxides. Further investigation revealed that the phosphorane-(salen)CoI complex could also successfully catalyze the coupling of CO2 with aziridines under ambient conditions at a catalyst loading of 2.5 mol%.
Zhou, Feng,Xie, Shi-Liang,Gao, Xiao-Tong,Zhang, Rong,Wang, Cui-Hong,Yin, Guang-Qiang,Zhou, Jian
supporting information
p. 3908 - 3915
(2017/08/22)

One-pot syntheses of α,α-dibromoacetophenones from aromatic alkenes with 1,3-dibromo-5,5-dimethylhydantoin
A novel method for the preparation of α,α-dibromoacetophenones from aromatic alkenes was reported. This procedure was mediated by 1,3-dibromo-5,5-dimethylhydantoin, which served as bifunctional reagent, proceeding oxidation and bromination in one-pot.
Wu, Ping,Xu, Senhan,Xu, Hao,Hu, Haiyan,Zhang, Wei
supporting information
p. 618 - 621
(2017/01/25)

Halofunctionalization of alkenes by vanadium chloroperoxidase from: Curvularia inaequalis
The vanadium-dependent chloroperoxidase from Curvularia inaequalis is a stable and efficient biocatalyst for the hydroxyhalogenation of a broad range of alkenes into halohydrins. Up to 1 200 000 TON with 69 s-1 TOF were observed for the biocatalyst. A bienzymatic cascade to yield epoxides as reaction products is presented.
Dong, Jia Jia,Fernández-Fueyo, Elena,Li, Jingbo,Guo, Zheng,Renirie, Rokus,Wever, Ron,Hollmann, Frank
supporting information
p. 6207 - 6210
(2017/07/10)

Halohydrin and its derivatives low priced high-efficient synthetic method (by machine translation)
The invention discloses a halohydrin low priced high-efficient synthetic method, the organic solvent of formula I shown in the olefin compound with a halide, sulfoxide and additive mixing, by the olefin of hydroxy halogenate reaction, can be a high selectivity of the halohydrin the system results in the type II shown, wherein R1 , R2 , R3 , R4 , R5 And R6 Are selected from hydrogen, halogen, alkyl, hydroxyalkyl, alkoxy, ester, acyl, amido, dialkyl amino, aryl, substituted aromatic, heterocyclic aromatic group or substituted heterocyclic aromatic, R1 , R2 , R3 , R4 , R5 And R6 The presence of the respective independent may be identical or different; or R1 And R2 , R1 And R3 , R2 And R4 , R3 And R4 , R5 And R6 Combining to form a cycloalkyl or substituted cycloalkyl, benzo ring alkyl or substituted cycloalkyl, heterocycle or substituted heterocycle; M selected from hydrogen, lithium, sodium, potassium, cesium, beryllium, magnesium, calcium, strontium, barium, zinc, copper, iron, ammonium or tetraalkyl ammonium; X chlorine, bromine or iodine. (by machine translation)
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Paragraph 0036; 0037; 0038; 0039

(2017/08/25)

One-pot synthesis of α-bromo- and α-azidoketones from olefins by catalytic oxidation with in situ-generated modified IBX as the key reaction
Simple one-pot protocols for the syntheses of α-bromoketones and α-azidoketones starting from olefins have been developed by employing catalytic oxidation of the intermediary bromohydrins with in situ-generated modified IBX as the key reaction. The improved procedure involves initial formation of bromohydrin by the reaction of olefin with NBS in acetonitrile-water mixture (1:1) at rt followed by oxidation with in situ-generated 3,4,5,6-tetramethyl-2-iodoxybenzoic acid (TetMe-IBX), produced in catalytic amounts from 3,4,5,6-tetramethyl-2-iodobenzoic and Oxone. α-Bromoketones are further converted in the same pot to the corresponding α-azidoketones using NaN3/NaHCO3. The one-pot conversions are versatile for a variety of olefins that include cyclic as well as acyclic aliphatic olefins and electron-rich and electron-deficient styrenes. Chemoselective bromohydroxylation of electron-rich double bond and subsequent oxidation to the α-bromoketone is demonstrated for a substrate that contains both electron-rich and deficient double bonds.
Chandra, Ajeet,Parida, Keshaba Nanda,Moorthy, Jarugu Narasimha
supporting information
p. 5827 - 5832
(2017/09/09)

One-pot synthesis of optically pure β-hydroxy sulfones: Via a heterogeneous ruthenium/diamine-promoted nucleophilic substitution-asymmetric transfer hydrogenation tandem process
A mesoporous silica-based ruthenium/diamine-functionalized heterogeneous catalyst is prepared through the co-condensation of chiral 4-((trimethoxysilyl)ethyl)phenylsulfonyl-1,2-diphenylethylene-diamine and tetraethoxysilane, followed by complexation with a ruthenium/diamine complex. Its solid-state carbon cross-polarization/magic angle spinning NMR spectrum demonstrates well-defined single-site ruthenium/diamine species, whereas the scanning and transmission electron microscopy images confirm the highly distributed ruthenium active centers on uniformly mesostructured nanoparticles. This heterogenous catalyst displays high catalytic and enantioselective performance in the nucleophilic substitution-asymmetric transfer hydrogenation one-pot enantioselective tandem reactions of α-bromoketones and sodium sulfonates, resulting in various chiral β-hydroxy sulfones with up to 99% enantioselectivity. Furthermore, the recycled heterogeneous catalyst can be reused repeatedly for at least six times, providing a practical approach for the one-pot preparation of chiral β-hydroxy sulfones in an environmentally friendly medium.
Wang, Jinyu,Wu, Liang,Hu, Xiaoying,Liu, Rui,Jin, Ronghua,Liu, Guohua
p. 4444 - 4450
(2017/10/13)

Catalytic asymmetric Meerwein-Ponndorf-Verley reduction of glyoxylates induced by a chiral N,N′-dioxide/Y(OTf)3 complex
An asymmetric Meerwein-Ponndorf-Verley (MPV) reduction of glyoxylates was for the first time accomplished via an N,N′-dioxide/Y(OTf)3 complex with aluminium alkoxide and molecular sieves (MSs) as crucial additives. A variety of optically active α-hydroxyesters were obtained with excellent results. A possible reaction mechanism was proposed based on the experiments.
Wu, Wangbin,Zou, Sijia,Lin, Lili,Ji, Jie,Zhang, Yuheng,Ma, Baiwei,Liu, Xiaohua,Feng, Xiaoming
supporting information
p. 3232 - 3235
(2017/03/20)

New polymeric, dimeric and mononuclear dioxidomolybdenum(VI) complexes with an ONO donor ligand: Crystal structures, DFT calculations, catalytic performance and protein binding study of the ligand
Reaction of [MoO2(acac)2] with a new ONO donor Schiff base ligand (H2L), derived from 2-aminobenzoylhydrazide and benzoyl acetone in methanol under refluxing conditions, yields polymeric [MoO2L]n (1) and dimeric [MoO2L]2·THF (2) dioxidomolybdenum(vi) complexes. Complexes 1 and 2 undergo reaction with monodentate Lewis bases forming mononuclear complexes [MoO2L(3-pic)] (3), [MoO2L(1-allylimz)] (4) and [MoO2L(DMSO)] (5). In these complexes, the ligand is coordinated to the cis-[MoO2]2+ cores through enolic oxygens and an azomethine nitrogen. In complexes 3 and 4 the remaining sixth coordination site is occupied by the nitrogen atoms and in complex 5 by the oxygen atom of the Lewis base. The crystal structures of these complexes (1-5) have been determined by single crystal X-ray diffraction. The molybdenum atom exhibits a distorted octahedral coordination sphere. In complex 1, a 1D zigzag polymeric chain is formed through OMo-O interactions. In complex 2, a centrosymmetric dimer is formed through weak interaction of the non-coordinating amine nitrogen with the molybdenum centre. In contrast complexes 3, 4 and 5 are monomeric. The investigated complexes have also been characterized by elemental analysis, various spectroscopic techniques, thermogravimetric analysis and cyclic voltammetry. Supportive DFT calculations on the complexes have been carried out. The dioxidomolybdenum(vi) complexes have been tested for catalytic epoxidation and oxidative bromination of styrene. Fluorescence spectral measurements carried out by varying the concentration of the ligand indicate strong fluorescence resonance energy transfer (FRET) from BSA to the ligand and from the binding studies it is revealed that BSA has two binding sites for the ligand.
Biswal, Debanjana,Pramanik, Nikhil Ranjan,Chakrabarti, Syamal,Drew, Michael G. B.,Sarkar, Bithikax,Maurya, Mannar R.,Mukherjee, Sanjib K.,Chowdhury, Pramit
p. 4116 - 4137
(2017/07/12)

Exploiting a beast in carbenoid chemistry: Development of a straightforward direct nucleophilic fluoromethylation strategy
The first direct and straightforward nucleophilic fluoromethylation of organic compounds is reported. The tactic employs a fleeting lithium fluorocarbenoid (LiCH2F) generated from commercially available fluoroiodomethane. Precise reaction conditions were developed for the generation and synthetic exploitation of such a labile species. The versatility of the strategy is showcased in ca. 50 examples involving a plethora of electrophiles. Highly valuable chemicals such as fluoroalcohols, fluoroamines, and fluoromethylated oxygenated heterocycles could be prepared in very good yields through a single synthetic operation. The scalability of the reaction and its application to complex molecular architectures (e.g., steroids) are documented.
Parisi, Giovanna,Colella, Marco,Monticelli, Serena,Romanazzi, Giuseppe,Holzer, Wolfgang,Langer, Thierry,Degennaro, Leonardo,Pace, Vittorio,Luisi, Renzo
supporting information
p. 13648 - 13651
(2017/11/06)

Complexes of cis-dioxomolybdenum(VI) with a chiral tetradentate tripodal-like ligand system: Syntheses, structures and catalytic activities
Racemic complexes with the general formula cis-[MoO2(bzacLn)] (1–4) (H2bzacLn?=?2-((4/5-R-2-hydroxyphenylamino)(pyridin-2-yl)methyl)-1-phenylbutane-1,3-dione, where n?=?1–4 for R?=?H, 5-Me, 5-Cl and 4-Me, respectively and 2Hs represent the dissociable phenolic proton and the active tertiary CH proton) have been synthesized in 75–82% yields by reacting [MoO2(bzac)2] (Hbzac?=?benzoylacetone) with the potentially N2O-donor 5,5-membered fused chelate rings forming Schiff bases 4/5-R-2-(2-pyridylaldimine)phenols (HLn; n?=?1–4 for R?=?H, 4-Me, 4-Cl and 5-Me, respectively) in hot methanol. The chiral ligand system (bzacLn)2?in 1–4 is formed via metal assisted Mannich-type addition of benzoylacetonate methine to the azomethine fragment of HLn. All four complexes have been characterized by elemental (CHN) analysis, solution conductivity, magnetic susceptibility, spectroscopic (IR, UV–Vis and NMR) and electrochemical measurements. The molecular structures of 1–3 have been established by single crystal X-ray crystallography. In each complex, the chiral (bzacLn)2?acts as a tetradentate, N2O2-donor, tripodal-like ligand system and along with the two mutually cis oxo groups forms a distorted octahedral N2O4coordination environment around the molybdenum(VI) center. All four complexes are diamagnetic and non-electrolytic. The infrared spectra are generally consistent with the structural formulas of 1–4. The electronic spectra of 1–4 in dimethylformamide display two strong absorption bands in the range 245–300?nm. The cyclic voltammograms of 1–4 in dimethylformamide exhibit a metal centered one-electron reduction response within ?0.64 to ?0.74?V. All these complexes (1–4) and the analogous cis-[MoO2(acacL1–4)] (5–8) synthesized from [MoO2(acac)2] (Hacac?=?acetylacetone) and HL1–4have been evaluated for their bromoperoxidase activities.
Ghosh, Sabari,Kurapati, Sathish Kumar,Pal, Samudranil
p. 26 - 33
(2017/03/07)

Cis-Dioxomolybdenum(VI) complexes with unsymmetric linear tetradentate ligands: Syntheses, structures and bromoperoxidase activities
Reactions of [MoO2(acetylacetonate)2], 2-((2-(2-hydroxyethylamino)ethylamino)methyl)-4-R-phenols (H2Ln, n = 1-5 for R = H, Me, OMe, Cl and Br, respectively) and KOH in 1:1:2 mole ratio in methanol afford a series of complexes having the general formula cis-[MoO2(Ln)] (1, 2, 3, 4, 5) in 81-86% yields. The complexes have been characterized using elemental analysis, spectroscopy (infrared, UV-visible, and 1H NMR, 13C NMR and 13C-DEPT NMR) and electrochemical measurements. The molecular structures of 1, 2, 3, 4 have been determined using single-crystal X-ray crystallography. In each of 1, 2, 3, 4, the ONNO-donor 6,5,5-membered fused chelate rings forming (Ln)2- and the two mutually cis oxo groups assemble a distorted octahedral N2O4 coordination sphere around the metal centre. In the crystal lattice, each of 1, 2, 3, 4 forms a one-dimensional infinite chain structure via intermolecular N-H...O hydrogen bonding interactions. In cyclic voltammograms, the diamagnetic complexes display an irreversible metal-centred reduction in the potential range -0.73 to -0.88 V (vs Ag/AgCl). The physicochemical data are consistent with a very similar gross molecular structure for all of 1, 2, 3, 4, 5. All the complexes exhibit decent bromoperoxidase activities and are also able to effectively catalyse benzoin and methyl(phenyl)sulfide oxidation reactions.
Kurapati, Sathish Kumar,Pal, Samudranil
p. 116 - 124
(2016/02/18)