- Classic and multivariate modeling treatment of the kinetics and mechanism of isomerization of 5-cholesten-3-one catalyzed by sodium ethoxide
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A classic kinetic methodology including the treatment of the steady-state method and a multivariate modeling kinetic treatment were applied to the kinetics and mechanism of the isomerization reaction of 5-cholesten-3-one to 4-cholesten-3-one catalyzed by EtO- in ethanol absolute. The rate constants, thermodynamic parameters of activation, equilibrium constant, and the isomerization enthalpy were determined. The multivariate modeling kinetic treatment allows us to calculate the concentrations of the species, in which the 3,5-dienolate is included as a highly reactive intermediate species and was able to discriminate among several applicable mechanisms validating the one comprising two reversible steps.
- Gonzalez-Hernandez,Canedo,Grande
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- Cr(VI) Oxidation of Cholesterol—A Kinetic Study Using N-Cetylpicolinium Dichromates, A Class of Novel Phase Transfer Oxidants
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Abstract: Kinetic study of cholesterol oxidation has been studied using a series of N-cetylpicolinium dichromates (CPDC), a class of phase transfer oxidants, in acetic acid medium under first order conditions with respect to oxidant. Rate constants were calculated in the temperature range 290–300 K. The kinetics was followed spectrophotometrically; cholest-5-en-3-one is found to be the only oxidation product. Unlike the previously reported lipopathic oxidant containing cetyltrimethylammonium ions, these oxidants show a direct variation of rate with the oxidant concentration ruling out any reversed micellar organization of the oxidant molecules. From the experimental data formation of an unstable cyclic transition state followed by intra-molecular proton transfer has been proposed. Solvent isotope effect for the cholesterol oxidation (Formula Presented.) indicated a carbon-hydrogen cleavage rather than a carbon-carbon cleavage. Variation of solvent polarity is found to impose a remarkable impact on the rate of oxidation: more polar reaction environment favours the oxidation by β-CPDC oxidant to a higher extent, compared to the other two oxidant isomers, α-CPDC and γ-CPDC.
- Priyadarshini,Guru,Ds,Dash
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- Annelation of the pyrrole to the steroid skeleton using the Trofimov reaction
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The product of annelation of the N-vinyl pyrrole ring with steroid skeleton of 5-cholestene was obtained in a single regioselective step by the reaction of 5-cholesten-3-one oxime with acetylene in KOH-DMSO by the Trofimov reaction.
- Vasil'tsov,Zaitsev,Mikhaleva,Shmidt,Afonin
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- Synthesis and characterisation of steroidal inhibitors of α-amylase, α-glucosidase and oxidative species
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BACKGROUND: Management of cellular metabolism and blood glucose levels are significant in the treatment of diabetes mellitus and oxidative diseases. Consequently, steroid and peptide hormone-based drugs such as methylprednisolone and insulin have been the most effective and safe methods of treatment. OBJECTIVE: Our study investigated the digestive enzymes and oxidative species inhibitory potentials of seven derived biologically important steroids. METHODS: Syntheses of the steroidal inhibitors (SIs) were accomplished by functional group transformations. Characterisation of SIs was achieved by spectroscopic techniques; followed by in-vitro enzyme and oxidative suppression studies. RESULTS: NMR data revealed the presence of a steroid backbone, azomethine, carbonyl, and oxymethine peaks while the vibrational bands were further confirmed by the FTIR. The enzyme suppression activities of the SIs were influenced by the presence of histidine residue and free proton groups. However, the antioxidant activities were solely dependent on the free proton groups on the steroid backbone or the number of the histidine side chain. SIs [3, 4, and 6] exhibited a potent inhibitory effect on the enzyme activities compared to SIs [1, 2, 5, and 7], while a potent antioxidant activity was reported by SI [5]. CONCLUSIONS: Generally, SIs with hydroxyl and α-amino acid functionalities have a strong affinity for the enzyme active site than the substrate; hence, the hydrolysis of the α-1,4-glycosidic bonds of saccharide was hindered. In vivo administration of SIs [3, 4, and 6] should take into cognizance the suppression effect at doses ≤939.49 μg/mL as well as the potential to induce abnormal bacterial fermentation of undigested carbohydrates in the colon at high concentration.
- Fanyana, Mthunzi,Habila, James D.,Modise, Johannes S.,Ndukwe, Iloegbulam G.,Okoli, Bamidele J.,Olaniyan, Olugbemi T.,Rachael, Ayo G.
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- Syntheses and antiproliferative activity of some sulfated hydroximinosterols
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Four new sulfated steroidal compounds, sodium 3-hydroxy-6- hydroximinocholestane 3-sulfate (7a), sodium 3-hydroxy-6-hydroximinostigmastane 6-sulfate (7b), sodium 3-hydroxy-6-hydroximinocholest-4-ene 3-sulfate (10a), and sodium 6-hydroxy-3-hydroximinocholestane 6-sulfate (16) had been synthesized using cholesterol or stigmasterol as starting materials by different synthetic methods. The synthetic compounds were characterized by their analytical and spectral data, and their antiproliferative activity against MGC 7901 (human gastric carcinoma cell line), HeLa (human cervical carcinoma cell line), and SMMC 7404 (human liver carcinoma cell line) were investigated. The results showed that the compounds exhibited a remarkable cytotoxicity against HeLa tumor cells in vitro and 7a displayed a better cytotoxicity than cisplatin (a positive contrast).
- Huang, Yanmin,Cui, Jianguo,Li, Ying,Fan, Lei,Jiao, Yanxiao,Su, Shaoyang
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- Alteration of Membrane Cholesterol Content Plays a Key Role in Regulation of Cystic Fibrosis Transmembrane Conductance Regulator Channel Activity
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Altered cholesterol homeostasis in cystic fibrosis patients has been reported, although controversy remains. As a major membrane lipid component, cholesterol modulates the function of multiple ion channels by complicated mechanisms. However, whether cholesterol directly modulates cystic fibrosis transmembrane conductance regulator (CFTR) channel function remains unknown. To answer this question, we determined the effects of changing plasma membrane cholesterol levels on CFTR channel function utilizing polarized fischer rat thyroid (FRT) cells and primary human bronchial epithelial (HBE) cells. Treatment with methyl-β-cyclodextrin (MβCD) significantly reduced total cholesterol content in FRT cells, which significantly decreased forskolin (FSK)-mediated activation of both wildtype (WT-) and P67L-CFTR. This effect was also seen in HBE cells expressing WT-CFTR. Cholesterol modification by cholesterol oxidase and cholesterol esterase also distinctly affected activation of CFTR by FSK. In addition, alteration of cholesterol increased the potency of VX-770, a clinically used potentiator of CFTR, when both WT- and P67L-CFTR channels were activated at low FSK concentrations; this likely reflects the apparent shift in the sensitivity of WT-CFTR to FSK after alteration of membrane cholesterol. These results demonstrate that changes in the plasma membrane cholesterol level significantly modulate CFTR channel function and consequently may affect sensitivity to clinical therapeutics in CF patients.
- Cui, Guiying,Cottrill, Kirsten A.,Strickland, Kerry M.,Mashburn, Sarah A.,Koval, Michael,McCarty, Nael A.
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- Photochemical oxidation of benzylic primary and secondary alcohols utilizing air as the oxidant
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A mild and green photochemical protocol for the oxidation of alcohols to aldehydes and ketones was developed. Utilizing thioxanthenone as the photocatalyst, molecular oxygen from air as the oxidant and cheap household lamps or sunlight as the light source, a variety of primary and secondary alcohols were converted into the corresponding aldehydes or ketones in low to excellent yields. The reaction mechanism was extensively studied.
- Nikitas, Nikolaos F.,Tzaras, Dimitrios Ioannis,Triandafillidi, Ierasia,Kokotos, Christoforos G.
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supporting information
p. 471 - 477
(2020/02/13)
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- NiH-Catalyzed Proximal-Selective Hydroamination of Unactivated Alkenes
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Reported herein is a modular, NiH-catalyzed system capable of proximal-selective hydroamination of unactivated alkenes with diverse amine sources. The key to the successful implementation of this approach is the promotion of NiH insertion into even highly substituted olefins via coordination of the bidentate directing group to the nickel complex. A wide range of primary and secondary amines can be installed in both internal and terminal unactivated alkenes with excellent regiocontrol under the optimized reaction conditions. This protocol is flexible and general for the preparation of a variety of valuable β- and γ-amino acid building blocks that would otherwise be difficult to synthesize. The utility of this transformation was further demonstrated by the site-selective late-stage modification of complex and medicinally relevant molecules. Combined experimental and computational studies illuminate the detailed reaction mechanism.
- Jeon, Jinwon,Lee, Changseok,Seo, Huiyeong,Hong, Sungwoo
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supporting information
p. 20470 - 20480
(2020/11/27)
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- Synthesis of [18 F]-γ-Fluoro-α,β-unsaturated Esters and Ketones via Vinylogous 18 F-Fluorination of α-Diazoacetates with [18 F]AgF
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This communication reports a method for the vinylogous radiofluorination of α-diazoacetates to generate [18 F]-γ-fluoro-α,β-unsaturated esters and ketones in moderate to good radiochemical yields. The method uses no-carrier-added [18 F]AgF and is compatible with aromatic and non-aromatic substrates and a number of different functional groups. The labeling method is showcased in the synthesis of a fluorinated cholest-5-en-3-one derivative as well as a difluorinated product pertinent to drug discovery.
- Brooks, Allen F.,Ichiishi, Naoko,Jackson, Isaac M.,Lee, So Jeong,Sanford, Melanie S.,Scott, Peter J. H.,Thompson, Stephen
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supporting information
p. 4401 - 4407
(2019/11/21)
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- Highly Efficient Abnormal NHC Ruthenium Catalyst for Oppenauer-Type Oxidation and Transfer Hydrogenation Reactions
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The ruthenium complex [Ru(OAc)(a-PC)2]Br (3) containing two abnormal NHC ligands is obtained by reaction of Ru(OAc)2(PPh3)2 (1) with 1-(2-diphenylphosphinoethyl)-3-mesitylimidazolium bromide in the presence of NaOAc. Complex 3 catalyzes the Oppenauer-type oxidation of a number of alcohols at unrivalled reaction rates reaching TOFs up to 550 000 h-1, at low catalyst loadings (S/C higher than 10 000) and using acetone in stoichiometric amounts. Complex 3 is also highly active in the reverse transfer hydrogenation of several ketones with 2-propanol, displaying TOFs up to 600 000 h-1
- Pardatscher, Lorenz,Hofmann, Benjamin J.,Fischer, Pauline J.,H?lzl, Sebastian M.,Reich, Robert M.,Kühn, Fritz E.,Baratta, Walter
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p. 11302 - 11306
(2019/11/21)
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- UV light promoted 'Metal'/'Additive'-free oxidation of alcohols: Investigating the role of alcohols as electron donors
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UV light promoted selective oxidation of primary and secondary alcohols has been demonstrated under 'metal-free' and 'additive-free' conditions. Under the optimized conditions, a variety of aromatic, heteroaromatic, and alicyclic alcohols have been examined for their transformations to the corresponding carbonyl compounds. The mechanistic studies emphasize the important role of substrate (alcohol) and solvent (DMSO) in the generation of superoxide radical which is a vital intermediate for the transformation. This study also highlights the role of air as the oxidant in the oxidation process. Further, the practical application of the strategy has also been demonstrated for the oxidation of the alcoholic moiety in cholesterol.
- Walia, Preet Kamal,Sharma, Manik,Kumar, Manoj,Bhalla, Vandana
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p. 36198 - 36203
(2019/11/20)
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- SYNTHESIS OF HYPERVALENT IODINE REAGENTS WITH DIOXYGEN
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Methods of synthesis of hypervalent iodine reagents and methods for oxidation of organic compounds are disclosed.
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Paragraph 0114-0117; 0142-0143
(2019/01/15)
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- Oxidation Catalysis by an Aerobically Generated Dess–Martin Periodinane Analogue
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Hypervalent iodine(V) reagents, such as Dess–Martin periodinane (DMP) and 2-iodoxybenzoic acid (IBX), are broadly useful oxidants in chemical synthesis. Development of strategies to generate these reagents from dioxygen (O2) would immediately enable use of O2 as a terminal oxidant in a broad array of substrate oxidation reactions. Recently we disclosed the aerobic synthesis of I(III) reagents by intercepting reactive oxidants generated during aldehyde autoxidation. In this work, aerobic oxidation of iodobenzenes is coupled with disproportionation of the initially generated I(III) compounds to generate I(V) reagents. The aerobically generated I(V) reagents exhibit substrate oxidation chemistry analogous to that of DMP. The developed aerobic generation of I(V) has enabled the first application of I(V) intermediates in aerobic oxidation catalysis.
- Maity, Asim,Hyun, Sung-Min,Wortman, Alan K.,Powers, David C.
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supporting information
p. 7205 - 7209
(2018/05/29)
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- DABCO-bis-CC: An efficient alternative to PCC
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We have developed a new chromium based reagent ‘DABCO?bis-CC’ for the straightforward oxidation of alcohols to corresponding carbonyl compounds with high efficiency. The present results demonstrate a broad range of alcohols including primary, secondary, aliphatic, benzylic and heterocyclic alcohols are tolerated as substrates at room temperature.
- Saikia, Bishwajit
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p. 583 - 586
(2018/06/26)
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- Synthesis and spectroscopic studies of Ru(II) complexes of steroidal thiosemicarbazones by multi step reaction: As anti-bacterial agents
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Ru(II) steroidal metal complexes were synthesized by the reaction of dichlorodicarbonyl ruthenium(II) [Ru(CO)2Cl2]n with Steroidal thiosemicarbazones. Coordination via the thionic sulfur and the azomethine nitrogen atom of
- Khan, Salman A.,Asiri, Abdullah M.
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- Secondary Phosphine Oxides as Multitalented Preligands En Route to the Chemoselective Palladium-Catalyzed Oxidation of Alcohols
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Secondary phosphine oxides O=PHR2 (SPOs) were identified as multitalented preligands for the chemoselective Pd-catalyzed oxidation of alcohols by a hydrogen-abstracting methodology. SPOs were found to promote the hydrogen-abstraction step as well as hydrogen transfer to a Michael acceptor by generating a putative active H?Pd species. The catalytic system operates under neutral conditions and was proven to be compatible with various electrophilic and nucleophilic functionalities within the substrates as well as water- and air-sensitive functional groups.
- Vasseur, Alexandre,Membrat, Romain,Gatineau, David,Tenaglia, Alphonse,Nuel, Didier,Giordano, Laurent
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p. 728 - 732
(2017/03/13)
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- Copper(II) and cobalt(II) tetrazole-saccharinate complexes as effective catalysts for oxidation of secondary alcohols
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Mononuclear Cu(II) and Co(II) complexes comprising 2-methyltetrazole-saccharinate bidentate N,N-chelating ligand have been synthesized for the first time and tested as homogeneous catalysts for oxidation of secondary alcohols in a solvent-free and microwave assisted protocol using aqueous tert-butyl hydroperoxide (TBHP) as oxidant. The developed catalytic system exhibits broad functional group compatibility, allowing efficient and selective conversion of a variety of secondary alcohols, including allylic ones, into the corresponding ketones. With typical 0.2 mol% content of the catalyst and under 20–50 W microwave irradiation, most reactions are complete within 10 min, presenting TONs up to 5.5 × 102 and TOFs up to 1.1 × 104 h?1. No additives and co-oxidants have been used, while TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxyl) acts as inhibitor in most cases. A plausible reaction mechanism involving the new catalytic systems is outlined.
- Frija, Luís M.T.,Alegria, Elisabete C.B.A.,Sutradhar, Manas,Cristiano, M. Lurdes S.,Ismael, Amin,Kopylovich, Maximilian N.,Pombeiro, Armando J.L.
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p. 283 - 290
(2016/11/04)
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- Structural elucidation, density functional calculations and contribution of intermolecular interactions in cholest-4-en-3-one crystals: Insights from X-ray and Hirshfeld surface analysis
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The foremost objective of the present work is systematic analysis of intermolecular interactions in crystal structure of cholest-4-en-3-one (2) molecule. It is accomplished by Hirshfeld surface analysis and fingerprint plot. Hirshfeld surface analysis has been used to visualize the fidelity of the crystal structure. This method permitted for the identification of individual types of intermolecular contacts and their impact on the complete packing. Molecules are linked by a combination of CO - -H, CH - -H, and C - -H contacts, which have clear signatures in the fingerprint plots. The theoretical study was attempted to predict the optimized geometry and computed spectra by the Density Functional Theory (DFT) using the B3LYP function with the 6-311++G(d,p) basis set. Atomic charges, MEP mapping, HOMO-LUMO, various thermodynamic and molecular properties have been reported. In addition thermal stability, optical, morphological, and microstructral properties of the title compound (2) have also been explored.
- Khanam, Hena,Mashrai, Ashraf,Siddiqui, Nazish,Ahmad, Musheer,Alam, Mohammad Jane,Ahmad, Shabbir,Shamsuzzaman
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p. 274 - 283
(2015/07/27)
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- Synthesis of γ-acetoxy β-keto esters through regioselective hydration of γ-acetoxy-α,β-alkynoates
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The Au(I)-catalyzed regioselective hydration of γ-acetoxy-α,β-acetylinic ester by the assistance of a neighboring carbonyl group has been developed. Varieties of simple primary, secondary, and tertiary γ-acetoxy-α,β-acetylinic esters, even those bearing sensitive functional group in the remote reaction sites, are selectively hydrated to the corresponding β-keto esters. The reaction tolerates a wide variety of other carboxylates, such as benzoates, propionates, acrylates, and pivalates, including chiral carboxylates with retention of the configuration. The broad substrate scope, including the derivatization of complex natural products and neutral and open air conditions, makes this atom economical approach very practical. 18O labeling experiments disclose that the oxygen transposition occurs from the carboxylate group to the triple bond, not from water.
- Pradhan, Tapas R.,Mendhekar, Kishor L.,Mohapatra, Debendra K.
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p. 5517 - 5531
(2015/06/16)
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- A Single Nickel Catalyst for the Acceptorless Dehydrogenation of Alcohols and Hydrogenation of Carbonyl Compounds
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A single homogeneous nickel(II) complex, supported by the tris(3,5-dimethylpyrazolyl)borate ligand and 2-hydroxyquinoline ancillary ligand, is shown to catalyze both acceptorless dehydrogenation of alcohols and hydrogenation of carbonyl compounds under mild conditions. Products from the catalytic reactions were isolated with good yields. A mechanistic investigation highlights the critical role of the 2-hydroxyquinoline ligand in the catalysis and argues against a stepwise dehydrogenation pathway.
- Chakraborty, Sumit,Piszel, Paige E.,Brennessel, William W.,Jones, William D.
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supporting information
p. 5203 - 5206
(2015/11/18)
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- 3,4-Dihydroisoquinolinium trichloroacetatochromate: A mild and effective new reagent for oxidation of alcohols to carbonyl compounds and arenes to their quinones
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A new chromium(VI) reagent, 3,4-dihydroisoqinolinium trichloroacetatochromate was prepared by reacting trichloroacetic acid with CrO3in water. This reagent is suitable to oxidize various primary and secondary alcohols to the corresponding carbonyl compounds and anthracene to antraquinone in a good yields.
- Ozen, Recep
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p. 6081 - 6083
(2015/02/19)
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- An efficient and reusable vanadium based catalytic system for room temperature oxidation of alcohols to aldehydes and ketones
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A simple and efficient vanadium based catalyst system for the oxidation of primary and secondary alcohols to aldehydes or ketones is reported using tert-butyl hydroperoxide as oxidizing agent and vanadyl sulfate as catalyst at room temperature. The versatility of the catalytic protocol is studied with wide variety of substrates.
- Sarmah, Gayatri,Bharadwaj, Saitanya K.,Dewan, Anindita,Gogoi, Ankur,Bora, Utpal
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p. 5029 - 5032
(2015/01/08)
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- Role of sterically demanding chiral dirhodium catalysts in site-selective C-H functionalization of activated primary C-H bonds
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The influence of sterically demanding dirhodium tetracarboxylate catalysts on the site selectivity of C-H functionalization by means of rhodium carbene-induced C-H insertion is described. The established dirhodium tetraprolinate-catalyzed reactions of aryldiazoacetates cause preferential C-H functionalization of secondary C-H bonds as a result of competing steric and electronic effects. The sterically more demanding dirhodium tetrakis(triarylcyclopropanecarboxylate) catalysts, exemplified by dirhodium tetrakis[(R)-(1-(biphenyl)-2,2-diphenylcyclopropanecarboxylate)] [Rh 2(R-BPCP)4], favor C-H functionalization of activated primary C-H bonds. Highly site-selective and enantioselective C-H functionalization of a variety of simple substrates containing primary benzylic, allylic, and methoxy C-H bonds was achieved with this catalyst. The utility of this approach has been demonstrated by the late-stage primary C-H functionalization of (-)-∝-cedrene and a steroid.
- Qin, Changming,Davies, Huw M. L.
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supporting information
p. 9792 - 9796
(2014/07/22)
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- Silver-catalyzed vinylogous fluorination of vinyl diazoacetates
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A silver-catalyzed vinylogous fluorination of vinyl diazoacetates to generate γ-fluoro-α,β-unsaturated carbonyls is presented. Application of this method to the fluorination of farnesol and steroid derivatives was achieved.
- Qin, Changming,Davies, Huw M. L.
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supporting information
p. 6152 - 6154
(2014/01/17)
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- Electrochemical synthesis of glycoconjugates of 3β-hydroxy- Δ5-steroids by using non-activated sugars and steroidal thioethers
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A new protocol for the electrochemical synthesis of glycoconjugates is presented. Thioether derivatives of cholesterol and other sterols were subjected to anodic oxidation in the presence of a sugar alcohol affording glycoconjugates with the sugar linked to a steroid moiety by an ether bond. The isomeric 6β-3α,5α-cyclo-steroidal thioethers proved to be better sterol donors than the normal 3β-Δ5-steroidal thioethers.
- Tomkiel, Aneta M.,Brzezinski, Krzysztof,?otowski, Zenon,Siergiejczyk, Leszek,Wa?ejko, Piotr,Witkowski, Stanis?aw,Kowalski, Jan,P?oszyn?ska, Jolanta,Sobkowiak, Andrzej,Morzycki, Jacek W.
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p. 8904 - 8913
(2013/09/23)
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- MCl2(ampy)(dppf) (M = Ru, Os): Multitasking catalysts for carbonyl compound/alcohol interconversion reactions
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The easily accessible complexes [MCl2(dppf)(ampy)] (M = Ru (cis-1), Os (trans-2); dppf = 1,1′-bis(diphenylphosphino)ferrocene; ampy = 2-aminomethylpyridine) in the presence of base (NaOiPr, KOtBu) are efficient catalysts for several reactions involving carbonyl compounds and alcohols. The derivatives 1 and 2 catalyze the selective transfer hydrogenation of aldehydes and ketones to alcohols with 2-propanol using 0.1-0.005 mol % of catalyst at 82 °C with TOF values up to 3.0 × 105 h-1. These compounds (0.1-0.02 mol %) promote the hydrogenation of aldehydes and ketones in EtOH or a MeOH/EtOH mixture at 30-90 °C (5 atm of H2) and the acceptorless dehydrogenation of alcohols to ketones in tBuOH at 130-145 °C (0.4 mol %). Complexes 1 and 2 (0.5 mol %) catalyze the racemization of chiral alcohols at 70 °C in 2-propanol and the isomerization of allylic alcohols to ketones in tBuOH at 70-120 °C (1 mol %). In addition, 1 and 2 (0.5 mol %) promote the α alkylation of α-tetralone with primary alcohols (EtOH, nPrOH, and nBuOH) at 120 °C in a tBuOH/toluene mixture (1/2 v/v). Complex 2 is easily obtained in 93% yield from [OsCl2(PPh3) 3], dppf, and ampy in toluene.
- Putignano, Elisabetta,Bossi, Gianluca,Rigo, Pierluigi,Baratta, Walter
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experimental part
p. 1133 - 1142
(2012/04/04)
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- Iron-catalyzed oppenauer-type oxidation of alcohols
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A (hydroxycyclopentadienyl)iron dicarbonyl hydride catalyzes the Oppenauer-type oxidation of alcohols with acetone as the hydrogen acceptor. Many functional groups are tolerant to the oxidation conditions. The same complex also catalyzes the dehydrogenation of diols to lactones. A mechanism involving the formation of iron-alcohol complexes and their rapid ligand exchange with free alcohols is proposed. The trimethylsilyl groups on the cyclopentadienyl ligand of the catalyst play a critical role in stabilizing the iron hydride and increasing the catalyst lifetime.
- Coleman, Michael G.,Brown, Alec N.,Bolton, Brett A.,Guan, Hairong
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scheme or table
p. 967 - 970
(2010/06/17)
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- Synthesis, spectral studies and in vitro antibacterial activity of steroidal thiosemicarbazone and their palladium (Pd (II)) complexes
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We investigated the antibacterial activity of some new steroidal thiosemicarbazone and their Pd(II) metal complexes. Metal complexes were prepared from the reaction of steroidal thiosemicarbazone with [Pd(DMSO)2Cl2]. Coordination via
- Khan, Salman Ahmad,Yusuf, Mohamad
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scheme or table
p. 2270 - 2274
(2009/09/30)
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- Synthesis and evaluation of some steroidal oximes as cytotoxic agents: Structure/activity studies (I)
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The side chain of a compound plays an important role in its biological function. In our studies, we have found that hydroximinosteroid derivatives with different side chains and position of hydroximino on ring A and B displayed remarkable distinct cytotoxicities against a diversity of cancer cell types. Presence of an oxime group on ring B and a hydroxy on ring A or B resulted in a higher cytotoxicity than other structural motifs. In addition, a cholesterol-type side chain at position 17 was required for the biological activity. Our findings provide new evidence showing the relationship between the chemical structure and biological function. The information obtained from the studies may be useful for the design of novel chemotherapeutic drugs.
- Cui, Jian-Guo,Fan, Lei,Huang, Li-Liang,Liu, Hong-Li,Zhou, Ai-Min
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experimental part
p. 62 - 72
(2009/04/10)
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- Expedient method for oxidation of alcohol by hydrogen peroxide in the presence of amberlite IRA 400 resin (basic) as phase-transfer catalyst
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Amberlite IRA 400 (strongly basic), a classical polymer imparts phase-transfer catalysis in the oxidation of primary and secondary alcohols by hydrogen peroxide to give excellent yields of the corresponding carbonyl compounds or carboxylic acids in acetonitrile solvent at reflux temperature in 4-6 h. The catalytic system is inert to other susceptible oxidation sites such as carbon-carbon double bonds. Copyright Taylor & Francis Group, LLC.
- Bhati, Nishi,Sarma, Kuladip,Goswami, Amrit
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p. 1416 - 1424
(2008/09/20)
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- Binuclear ruthenium(III) Schiff base complexes bearing N4O4 donors and their catalytic oxidation of alcohols
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An interesting series of binuclear ruthenium(III) Schiff base complexes bearing bis-salophen/bis-naphophen units of the general composition [(EPh3)(X)Ru-L-Ru(X)(EPh3)] (where E = P or As; X = Cl or Br; L = binucleating dianionic tetradentate ligands) have been synthesized and characterized by analytical (elemental analysis, magnetic susceptibility measurements), spectral (FT-IR, UV-vis and EPR) and electrochemical methods. These ruthenium(III) complexes have two N2O2 metal binding sites, which are linked to each other with a biphenyl bridge and acts as potential catalyst for oxidation of wide range of primary and secondary alcohols to corresponding aldehydes or ketones with moderate to high conversion in the presence of N-methylmorpholine-N-oxide (NMO). The formation of high-valent RuV = O species as a catalytic active intermediate is proposed for the catalytic processes.
- Venkatachalam,Raja,Pandiarajan,Ramesh
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experimental part
p. 884 - 891
(2009/02/06)
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- Deprotection of thioacetals using K2S2O 8/[bmim]Br as a mild and efficient reagent under solvent-free conditions
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A straightforward and effective procedure for the deprotection of thioacetals to the corresponding carbonyl compounds using potassium persulfate and the ionic liquid [bmim]Br under solvent-free conditions is reported. A variety of aliphatic and aromatic 1,3-dithiolanes or 1,3-dithanes was deprotected to the corresponding carbonyl derivatives by this procedure. Springer-Verlag 2007.
- Hajipour, Abdol R.,Mostafavi, Majid,Ruoho, Arnold E.
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p. 569 - 572
(2008/02/03)
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- Epoxidation and oxidation reactions using divinyl benzene crosslinked polystyrene supported t-butyl hydroperoxide
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Divinyl benzene (DVB) crosslinked polystyrene supported t-butyl hydroperoxide resin has been prepared and employed in the epoxidation of olefins and oxidation of alcohols. The reagent is found to be efficient as the low molecular weight t-butyl hydroperoxide. Presence of catalyst enhanced the reaction efficiency remarkably. Influence of various reaction parameters such as solvent, temperature and molar excess of the reagent on the reactivity of the polymeric reagent is also being investigated.
- Sheela,Sreekumar
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p. 943 - 950
(2007/10/03)
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- Oxidation of alcohols to carbonyl compounds, benzylic carbons to their ketones, and arenes to their quinones with molecular oxygen in subcritical water
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Molecular oxygen is used as an efficient oxidant for the conversion of alcohols into carbonyl compounds, benzylic carbons to their ketones, and arenes to their quinones in subcritical water in the absence of catalysts. The procedure utilizes water and does not require support materials and metal salts. Springer-Verlag 2006.
- Ozen, Recep,Kus, Nermin S.
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p. 1597 - 1600
(2007/10/03)
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- Oxidation of cholesterol by a biomimetic oxidant, cetyltrimethylammonium dichromate
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The oxidation of cholesterol by cetyltrimethylammonium dichromate (CTADC) in dichloromethane (DCM) yielded 7-dehydrocholesterol, while with addition of acetic acid in DCM the product was found to be 5-cholesten-3-one. The kinetics of oxidation of cholesterol by CTADC in DCM, in the presence of acid, was investigated with change in [acid], [cholesterol], [CTADC], [surfactant], temperature, and solvents. The reaction was found to be first order with acetic acid and fractional order with CTADC and cholesterol. Michaelis-Menten-type kinetics was observed with respect to cholesterol. The solvent isotope effect was found to be k(D2O)/k(H2O) = 0.72. The observed experimental data suggest that the reaction occurs in reversed micellar system, akin to an enzymatic environment, and the reaction path involves the intermediate formation of an ester complex, which undergoes decomposition to give the product.
- Patel, Sabita,Mishra
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p. 3522 - 3526
(2007/10/03)
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- Stereoselective debromination and selective reduction of vic-dibromides with nickel boride
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A simple procedure is reported for the stereoselective debromination of vic-dibromides with nickel boride at ambient temperature. Debromination with concomitant reduction of vic-dibromides to give dihydro products in a one-pot reaction is also reported. α,β-Dibromoketones can also be converted to their corresponding alcohols.
- Khurana, Jitender M.,Kandpal, Bhaskar M.,Kukreja, Gagan,Sharma, Purnima
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p. 1019 - 1023
(2007/10/03)
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- Oxidative deprotection of trimethylsilyl ethers with hexamethylenetetramine-bromine supported onto silica gel under microwave irradiation in solventless system
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Hexamethylenetetramine-bromine supported onto silica gel rapidly converts trimethylsilyl ethers to their corresponding carbonyl compounds under microwave irradiation in solventless system.
- Dehkordi, Mahboobeh Behnam,Heravi, Mojid M.,Khosrofar, Parviz,Ziafat, Ahmad,Ghassemzadeh, Mitra
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p. 2595 - 2598
(2007/10/03)
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- Oxidative deprotection of oximes, phenylhydrazones and semicarbazones using pyridinium chlorochromate in catalytic amount with t-butyl hydroperoxide and in the solid state on montmorillonite K-10 clay support under microwave irradiation
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Pyridinium chlorochromate (FCC) and other oxochromium(VI) reagents have been extensively employed in excess of the stoichiometric amount (2 equivalents or more) for efficient cleavage of oximes to carbonyl compounds. The aim of this study is to replace excess use of toxic chromium(VI) reagents and develop cleaner environment-friendly general methods of cleavage of imine derivatives such as oximes, phenylhydrazones and semicarbazones using PCC in catalytic or stoichiometric amount. Two approaches of greening the deprotection process with PCC are conceived of which the first one is based on the catalytic use of the reagent (0.1 equiv.) in combination with an excess of 70% t-butyl hydroperoxide as the cooxidant. Mild selective regeneration of carbonyl compounds from oximes, phenylhydrazones and semicarbazones has been accomplished in good-to-excellent yields (70-98%) by this method. With focus on rate enhancement coupled with efficiency of cleavage, an alternative microwave-assisted solid-state solventiess protocol of deprotection employing a stoichiometric amount of PCC dispersed on montmorillonite K-10 clay is also evaluated. It offers an expeditious efficient (74-98% yields) general route of cleavage of these procarbonyl compounds. Absence of overoxidation, particularly for oxidation-prone aryl aldehydes, is the key advantage of both these methods.
- Ganguly, Nemai C.,Datta, Mrityunjoy,De, Prithwiraj
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p. 308 - 312
(2007/10/03)
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- Novel polyaniline-supported molybdenum-catalyzed aerobic oxidation of alcohols to aldehydes and ketones
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(Chemical Equation Presented) Oxidation of alcohols to aldehydes and ketones has been studied in high yields using molecular oxygen and a catalytic amount of 1 in toluene under stirring (ca. 100°C). The reactions of primary alcohols are faster compared to secondary alcohols and the catalyst 1 can be recycled without loss of activity.
- Velusamy, Subbarayan,Ahamed, Muneer,Punniyamurthy
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p. 4821 - 4824
(2007/10/03)
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- Mild and selective oxidation of alcohols and deoximation of oximes over supported quinolinium fluorochromate
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Quinolinium fluorochromate supported over silica gel selectively brings about the oxidation of a wide variety of alcohols and oxidative deoximation of certain aldoximes and ketoximes to the corresponding carbonyl compounds in good yield. The reagent selectively oxidises primary hydroxyl group in the presence of secondary hydroxyl group. The selectivity is also exhibited in the oxidation of axial hydroxyl group of the cis-4-t-butyl cyclohexanol in preference to equitorial hydroxyl group. Further the reagent is stable even after a period of twelve weeks of its storage.
- Rajkumar, G. Abraham,Sivamurugan,Arabindoo, Banumathi,Murugesan
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p. 936 - 946
(2007/10/03)
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- Synthetic mimics of small mammalian cell surface receptors
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Receptors on the surface of mammalian cells promote the uptake of cell-impermeable ligands by receptor-mediated endocytosis. To mimic this process, we synthesized small molecules designed to project anti-dinitrophenyl antibody-binding motifs from the surface of living Jurkat lymphocytes. These synthetic receptors comprise N-alkyl derivatives of 3β-cholesterylamine as the plasma membrane anchor linked to 2,4-dinitrophenyl (DNP) and structurally similar fluorescent 7-nitrobenz-2-oxa-1,3-diazole (NBD) headgroups. Insertion of two β-alanine subunits between a DNP derivative and 3β- cholesterylamine yielded a receptor that avidly associates with cell surfaces (cellular t1/2 ~ 20 h). When added to Jurkat cells at 10 μM, this receptor enhanced uptake of an anti-DNP IgG ligand by ~200-fold in magnitude and ~400-fold in rate within 4 h (ligand internalization t 1/2 ~ 95 min at 37°C). This non-natural receptor mimics many natural receptors by dynamically cycling between plasma membranes and intracellular endosomes (recycling t1/2 ~ 3 min), targeting of protein ligands to proposed cholesterol and sphingolipid-enriched lipid raft membrane microdomains, and delivery of protein ligands to late endosomes/lysosomes. Quantitative dithionite quenching of fluorescent extracellular NBD headgroups demonstrated that other 3β-cholesterylamine derivatives bearing fewer β-alanines in the linker region or N-acyl derivatives of 3β-cholesterylamine were less effective receptors due to more extensive trafficking to internal membranes. Synthetic cell surface receptors have potential applications as cellular probes, tools for drug delivery, and methods to deplete therapeutically important extracellular ligands.
- Boonyarattanakalin, Siwarutt,Martin, Scott E.,Dykstra, Sheryl A.,Peterson, Blake R.
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p. 16379 - 16386
(2007/10/03)
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- A rapid method for oxidative deprotection of trimethylsilyl ether with wet alumina supported Dess-Martin periodinane in solventless system under microwave irradiation
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Primary and secondary trimethylsilyl ethers have been rapidly coverted to the corresponding carbonyl compounds using Dess-Martin periodinance supported on to wet alumina in a solventless system under microwave irradiation.
- Oskooie, S. Hossein Abdi,Heravi, Majid M.,Sarmad, Noohshin,Saedniab, Akbar,Ghassemzadeh, Mitra
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p. 2890 - 2891
(2007/10/03)
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- Oxidation of alcohols using (NH4)2Cr 2O4 in the presence of Al(HSO4)3 and wet SiO2
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A mild and efficient method for the oxidation of alcohols by ammonium dichromate in the presence of Al(HSO4)3 and wet SiO 2 in solution or under solvent-free conditions is reported.
- Shirini, Farhad,Zolfigol, Mohammad A.,Abedini, Masoumeh,Salehi, Peyman
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p. 265 - 266
(2007/10/03)
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- N-tert-Butylbenzenesulfenamide-catalyzed oxidation of alcohols to the corresponding carbonyl compounds with N-chlorosuccinimide
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N-tert-Butylbenzenesulfenamide (1)-catalyzed oxidation of various primary and secondary alcohols to the corresponding aldehydes and ketones was efficiently carried out by using N-chlorosuccinimide (NCS) in the coexistence of potassium carbonate and molecular sieves 4? at easy-to-control temperatures ranging from 0°C to room temperature. The present catalytic oxidation was performed without giving any damage to the functional groups in alcohols, and was particularly effective in the oxidation of alcohols that formed labile aldehydes because of its mild reaction conditions. Further, selective oxidation of primary hydroxy groups took place in 1-catalyzed oxidation of several diols. Mechanistic investigation suggested that the chlorination of the sulfenamide 1 by NCS led to the formation of a key species, N-tert-butylbenzenesulfinimidoyl chloride (2), which in turn oxidized alcohols in the presence of potassium carbonate to afford carbonyl products by accompanying regeneration of the catalyst 1.
- Matsuo, Jun-Ichi,Iida, Daisuke,Yamanaka, Hiroyuki,Mukaiyama, Teruaki
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p. 6739 - 6750
(2007/10/03)
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- The Mn(acac)3-RCN-CCl4 system as a new efficient reagent for the oxidation of secondary alcohols into ketones
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The Mn(acac)3-RCN-CCl4 system was found to be efficient for the oxidation of secondary alcohols into the corresponding ketones in 80-93% yields. The oxidation proceeds through the formation of alkyl hypochlorites, which are generated from CCl4 and the alcohols in the presence of the Mn(acac)3-RCN catalytic system (R = Me, Et, and Ph).
- Khusnutdinov,Schadneva,Baiguzina,Dzhemilev
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p. 1065 - 1067
(2007/10/03)
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- The Characteristics and Applications of Recombinant Cholesterol Dehydrogenase
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Mass production of an r-CDH derived from Nocardia species was made possible by gene technology. (Horinouchi et al., Applied and Environmental Microbiology, 57, 1386-1393 (1991)). However, the characteristics of the r-CDH have not been studied in detail and have not been improved enough for industrial use. We accordingly characterized both the native-CDH and the r-CDH prepared from Streptomyces lividans. Both CDHs were monomers with molecular masses of 37 kDa. The Km of r-CDH was 2.50×10-3M for cholesterol and 2.33 × 10-4M for NAD. The activators of CDHs were TritonX-100 and cholate. TritonX-405, Ag+, and Zn2+ inhibited both enzymes. The residual activity of native CDH after heat treatment was 32% (37°C, 60 min), while the r-CDH showed a residual activity of 87% (37°C, 60 min). The r-CDH is an enzyme with high substrate specificity for cholesterol as well as native CDH and higher thermal stability than native CDH. We have developed a novel serum cholesterol assay using the r-CDH, which permits the direct measurement of cholesterol by measuring NADH reaction products. We conclude that this r-CDH enzyme is useful and can be used to measure cholesterol in a clinical chemistry setting.
- Kishi, Koji,Watazu, Yoshifumi,Katayama, Yoshiaki,Okabe, Hiroaki
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p. 1352 - 1358
(2007/10/03)
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- Microwave thermolysis VI: A rapid and general method for dethioacetalization using 'Clayan' in dry media
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A variety of thioacetals, dithiolanes and dithianes are deprotected into their carbonyl compounds using clay supported ammonium nitrate 'Clayan' under microwave irradiation. The present method avoids the use of toxic oxidants and excess of solvent.
- Meshram,Reddy, Gondi Sudershan,Sumitra,Yadav
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p. 1113 - 1119
(2007/10/03)
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- Efficient and selective oxidative deprotection of tetrahydropyranyl ethers, ethylene acetals and ketals with silver and sodium bromates in the presence of aluminum chloride
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Primary and secondary tetrahydropyranyl (THP) ethers are efficiently transformed to their carbonyl compounds with AgBrO3 and NaBrO3/AlCl3. Ethylene acetals and ketals are transformed to their carboxylic acids and ketones respectively with AgBrO3/AlCl3 in refluxing acetonitrile. AgBrO3/AlCl3 is also able to transform ethylene acetals to aldehydes in refluxing carbon tetrachloride in high yields. In refluxing acetonitrile, ethylene acetals and ketals are transformed to aldehydes and ketones with NaBrO3/AICI3. We have also found that tetrahydropyranyl ethers are oxidized selectively in the presence of ethylene acetals and ketals with these reagents.
- Mohammadpoor-Baltork, Iraj,Nourozi, Ali Reza
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p. 487 - 490
(2007/10/03)
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