- Microwave Spectrum, Molecular Structure and Dipole Moment of Pivalaldehyde
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The microwave spectra of eight isotopic species of pivalaldehyde have been studied in the frequency region 9-40 GHz.The zero-point average skeletal structure has been derived to be: r = 1.206(6) Angstroem, r = 1.130(5) Angstroem, r = 1.516(7) Angstroem, r = r = 1.537(2) Angstroem, C(1)C(2)C(3) = 110.5(4) deg, C(1)C(2)C(4),(5) = 107.4(3) deg, proj.C(4),(5)C(2)C(1) = 120.78(4) deg, CCO = 126.0(5) deg and CCH(1) = 113.0(3) deg.The tert-butyl group is found to be tilted 2 deg away from the C=O bond.Accurate Stark effect measurements have been performed on the main species, (CH3)3CCDO and (CD3)3CCHO.The ground-state dipole moment of (CH3)3CCHO was determined as μs = 2.618(5) D and μb = 0.728(2) D giving μtotal = 2.717(5) D at an angle of 13.6 deg to the C=O bond.
- Cox, Peter A.,Couch, Andrew D.,Hillig, Kurt W.,LaBarge, Marabeth S.,Kuczkowski, Robert L.
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Read Online
- Bioinspired Radical-Mediated Transition-Metal-Free Synthesis of N-Heterocycles under Visible Light
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A redox-active iminoquinone motif connected with π-delocalized pyrene core has been reported that can perform efficient two-electron oxidation of a class of substrates. The design of the molecule was inspired by the organic redox cofactor topaquinone (TPQ), which executes amine oxidation in the enzyme, copper amine oxidase. Easy oxidation of both primary and secondary alcohols happened in the presence of catalytic KOtBu, which could reduce the ligand backbone to its iminosemiquinonate form under photoinduced conditions. Moreover, this easy oxidation of alcohols under aerobic condition could be elegantly extended to multi-component, one-pot coupling for the synthesis of quinoline and pyrimidine. This organocatalytic approach is very mild (70 °C, 8 h) compared to a multitude of transition-metal catalysts that have been used to prepare these heterocycles. A detailed mechanistic study proves the intermediacy of the iminosemiquinonate-type radical and a critical hydrogen atom transfer step to be involved in the dehydrogenation reaction.
- K. Bains, Amreen,Ankit, Yadav,Adhikari, Debashis
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p. 324 - 329
(2020/11/30)
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- Kinetics and correlation analysis of reactivity in the oxidation of aliphatic primary alcohols by isoquinolinium dichromate in non-aqueous medium
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Mild oxidation in dimethyl sulfoxide (DMSO) medium by isoquinolinium dichromate (IQDC) of aliphatic primary alcohols produces corresponding carbonyl compounds. A Michaelis-Menten kind kinetics noticed as for alcohols while unit dependency on rate observed as for IQDC. At non-identical temperatures the formation constants and the rates of decomposition of alcohol-IQDC complexes have been evaluated. Thermodynamic parameters and activation parameters for formation of the complex and break down of the complexes have been determined respectively. The oxidation process accelerates with increase in proton concentration. An α-C-H bond fisson in the rate-controlling step suggested by the deuterium isotope effect. For oxidation of ethanol, kH/kD = 5.82 at 293 K, was observed. The oxidation rates have been evaluated in 19 organic solvents and greater role of solvating power of the cation is observed. Depended on the kinetic parameters, solvent effect analysis and the outcome of thermodynamic parameters, a mechanism in which rate-controlling break down of the complex is suggested, to give the resulting product through hydride-ion transfer with a cyclic transition state.
- Kalal, Reena,Panday, Dinesh
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- Solvent-free, microwave assisted oxidation of alcohols with 4-hydroxypyridinium chlorochromate functionalized silica gel
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4-Hydroxypyridinium chlorochromate functionalized silica gel was found to be an efficient and reusable oxidant for the very fast oxidation of primary and secondary alcohols to the corresponding carbonyl compounds under solventfree conditions and microwave irradiation in excellent yields.
- AHMADI, Sayed Ali,GHALEHBANDI, Shermineh Sadat,GHAZANFARI, Dadkhoda,SHEIKHHOSSEINI, Enayatollah
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p. 283 - 289
(2020/10/06)
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- A Multifunctional Microfluidic Platform for High-Throughput Experimentation of Electroorganic Chemistry
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Electroorganic synthesis is a promising tool to design sustainable transformations and discover new reactivities. However, the added setup complexity caused by electrodes in the system impedes efficient screening of reaction conditions. Herein, we present a microfluidic platform that enables automated high-throughput experimentation (HTE) for electroorganic synthesis at a 15-microliter scale. Two HTE modules are demonstrated: 1) the rapid electrochemical reaction condition screening for a radical–radical cross-coupling reaction on micro-fabricated interdigitated electrodes, and 2) measurements of kinetics for mediated anodic oxidations using the microliter-scale cyclic voltammetry. The presented modular approach could be deployed for a range of other electroorganic chemistry applications beyond the demonstrated functionalities.
- Jensen, Klavs F.,Mo, Yiming,Nambiar, Anirudh M. K.,Rughoobur, Girish,Zhang, Kara
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supporting information
p. 20890 - 20894
(2020/09/17)
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- Transfer hydrogenation of carbon dioxide: Via bicarbonate promoted by bifunctional C-N chelating Cp?Ir complexes
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Metal-ligand cooperative Cp?Ir(iii) complexes derived from primary benzylic amines effectively promote transfer hydrogenation of atmospheric CO2 using 2-propanol at 80 °C. Isotope-labelling experiments strengthen that active Ir species can preferentially reduce bicarbonate congeners formed from CO2. The powerful transfer hydrogenation catalyst exhibits remarkable activity for the conversion of bicarbonates into formate salts with a turnover number up to 3200, even without H2 and CO2.
- Sato, Yasuhiro,Kayaki, Yoshihito,Ikariya, Takao
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supporting information
p. 10762 - 10765
(2020/10/02)
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- A Strategy for Accessing Aldehydes via Palladium-Catalyzed C?O/C?N Bond Cleavage in the Presence of Hydrosilanes
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We report the catalytic reduction of both active esters and amides by selective C(acyl)?X (X=O, N) cleavage to access aldehyde functionality via a palladium-catalyzed strategy. Reactions are promoted by hydrosilanes as reducing reagents with good to excellent yields and with excellent chemoselectivity for C(acyl)?N and C(acyl)?O bond cleavage. Carboxylic acid C(acyl)?O bonds are activated by 2-chloro-4,6-dimethoxy-1,3,5-triazine (CDMT) to form triazine ester intermediates, which further react with hydrosilanes to yield aldehydes in one-pot two-step procedures. We demonstrate that C(acyl)?O cleavage/formylation offers higher yields and broader substrate scopes compared with C(acyl)?N cleavage under the same reaction conditions.
- He, Zhanyu,Liu, Tingting,Ru, Junxiang,Wang, Yulin,Wang, Zijia,Zeng, Zhuo
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p. 5794 - 5800
(2020/12/01)
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- Convenient synthesis of 2,3-dihydro-1,2,4-thiadiazoles, 4,5-dihydro-1,3-thiazoles, and 1,3-thiazoles through a [4+1]-type oxidative ring closure of 1,3-thiaza-1,3-butadienes
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1,3-Thiaza-1,3-butadienes bearing an N,N-dimethylamino group at the C-2 position were efficiently converted into 5H-1,2,4-oxathiazoles, 2,3-dihydro-1,2,4-thiadiazoles, 4,5-dihydro-1,3-thiazoles, and 1,3-thiazoles through an oxidative ring closure by treating with mCPBA, chloramine-T, metal carbenoids, or dichlorocarbene, respectively, via the ring closure of in situ generated heterocumulene-type reactive species involving thione S-oxides, thione S-imides, and thiocarbonyl ylides.
- Shimada, Kazuaki,Isogami, Megumi,Maeda, Kitami,Nishinomiya, Rei,Korenaga, Toshinobu
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p. 881 - 900
(2020/09/09)
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- The formyloxyl radical: Electrophilicity, C-H bond activation and anti-Markovnikov selectivity in the oxidation of aliphatic alkenes
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In the past the formyloxyl radical, HC(O)O, had only been rarely experimentally observed, and those studies were theoretical-spectroscopic in the context of electronic structure. The absence of a convenient method for the preparation of the formyloxyl radical has precluded investigations into its reactivity towards organic substrates. Very recently, we discovered that HC(O)O is formed in the anodic electrochemical oxidation of formic acid/lithium formate. Using a [CoIIIW12O40]5- polyanion catalyst, this led to the formation of phenyl formate from benzene. Here, we present our studies into the reactivity of electrochemically in situ generated HC(O)O with organic substrates. Reactions with benzene and a selection of substituted derivatives showed that HC(O)O is mildly electrophilic according to both experimentally and computationally derived Hammett linear free energy relationships. The reactions of HC(O)O with terminal alkenes significantly favor anti-Markovnikov oxidations yielding the corresponding aldehyde as the major product as well as further oxidation products. Analysis of plausible reaction pathways using 1-hexene as a representative substrate favored the likelihood of hydrogen abstraction from the allylic C-H bond forming a hexallyl radical followed by strongly preferred further attack of a second HC(O)O radical at the C1 position. Further oxidation products are surmised to be mostly a result of two consecutive addition reactions of HC(O)O to the CC double bond. An outer-sphere electron transfer between the formyloxyl radical donor and the [CoIIIW12O40]5- polyanion acceptor forming a donor-acceptor [D+-A-] complex is proposed to induce the observed anti-Markovnikov selectivity. Finally, the overall reactivity of HC(O)O towards hydrogen abstraction was evaluated using additional substrates. Alkanes were only slightly reactive, while the reactions of alkylarenes showed that aromatic substitution on the ring competes with C-H bond activation at the benzylic position. C-H bonds with bond dissociation energies (BDE) ≤ 85 kcal mol-1 are easily attacked by HC(O)O and reactivity appears to be significant for C-H bonds with a BDE of up to 90 kcal mol-1. In summary, this research identifies the reactivity of HC(O)O towards radical electrophilic substitution of arenes, anti-Markovnikov type oxidation of terminal alkenes, and indirectly defines the activity of HC(O)O towards C-H bond activation.
- Iron, Mark A.,Khenkin, Alexander M.,Neumann, Ronny,Somekh, Miriam
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p. 11584 - 11591
(2020/11/23)
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- Method for preparing trimethylacetaldehyde
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The invention discloses a method for preparing trimethylacetaldehyde. The method comprises the following steps: (1) firstly, carrying out a reduction reaction, namely taking pivaloyl chloride as a rawmaterial, palladium-carbon as a catalyst, acetonitrile as a reaction solvent and N,N-diisopropylethylamine as an acid-binding agent, and carrying out a reduction reaction with hydrogen; (2) secondly,carrying out filtration after the reduction reaction, namely filtering reaction liquid to obtain filtrate and a palladium-carbon catalyst, dissolving the generated organic salt into a solvent, and recycling the palladium-carbon catalyst; and (3) finally, carrying out distillation, namely distilling the filtrate, and collecting a fraction at 76-78 DEG C to obtain a trimethylacetaldehyde product, wherein the yield of the trimethylacetaldehyde product is up to 73%, and the content is greater than 98%. According to the method, common Pa/C available in the market is adopted to replace quinoline-sulfur poisoned Pa/C as a catalyst, organic tertiary amine is adopted as the acid-binding agent, and acetonitrile, DMF (Dimethyl Formamide) and lower fatty acid are adopted as solvents to replace aromatic solvents such as methylbenzene and the like, so that reaction steps and later treatment steps are simple.
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Paragraph 0025-0039
(2019/04/02)
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- Pd-Catalyzed Dehydrogenative Oxidation of Alcohols to Functionalized Molecules
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A dehydrogenative oxidation reaction of primary alcohols to aldehydes catalyzed by a simple Pd/Xantphos catalytic system was developed under an argon or nitrogen atmosphere without oxidizing agents or hydrogen acceptors. The reaction product could be easily changed: under aerobic conditions, esters were obtained in aprotic solvents, whereas the corresponding carboxylic acids were produced in aqueous media. These oxidizing processes were applicable to the efficient synthesis of useful nitrogen-containing heterocyclic compounds such as indole, quinazoline, and benzimidazole via intramolecular versions of this reaction from amino alcohols.
- Mori, Takamichi,Ishii, Chihiro,Kimura, Masanari
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supporting information
p. 1709 - 1717
(2019/09/04)
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- O→S Relay Deprotection: A General Approach to Controllable Donors of Reactive Sulfur Species
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Reactive sulfur species (RSS) are biologically important molecules. Among them, H2S, hydrogen polysulfides (H2Sn, n>1), persulfides (RSSH), and HSNO are believed to play regulatory roles in sulfur-related redox biology. However, these molecules are unstable and difficult to handle. Having access to their reliable and controllable precursors (or donors) is the prerequisite for the study of these sulfur species. Reported in this work is the preparation and evaluation of a series of O-silyl-mercaptan-based sulfur-containing molecules which undergo pH- or F?-mediated desilylation to release the corresponding H2S, H2Sn, RSSH, and HSNO in a controlled fashion. This O→S relay deprotection serves as a general strategy for the design of pH- or F?-triggered RSS donors. Moreover, we have demonstrated that the O-silyl groups in the donors could be changed into other protecting groups like esters. This work should allow the development of RSS donors with other activation mechanisms (such as esterase-activated donors).
- Kang, Jianming,Xu, Shi,Radford, Miles N.,Zhang, Wenjia,Kelly, Shane S.,Day, Jacob J.,Xian, Ming
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supporting information
p. 5893 - 5897
(2018/04/25)
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- Hexafluoroisopropanol as the Acid Component in the Passerini Reaction: One-Pot Access to β-Amino Alcohols
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A new Passerini-type reaction in which hexafluoroisopropanol functions as the acid component is reported. The reaction tolerates a broad range of isocyanides and aldehydes, and the formed imidates can be reduced toward β-amino alcohols under mild and metal-free conditions. In addition, the imidate products were shown to undergo an unprecedented retro-Passerini-type reaction under microwave conditions, providing valuable mechanistic information about the Passerini reaction and its variations.
- Saya, Jordy M.,Berabez, Rayan,Broersen, Pim,Schuringa, Imme,Kruithof, Art,Orru, Romano V. A.,Ruijter, Eelco
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supporting information
p. 3988 - 3991
(2018/07/15)
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- Enhancement of the Oxidizing Power of an Oxoammonium Salt by Electronic Modification of a Distal Group
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The multigram preparation and characterization of a novel TEMPO-based oxoammonium salt, 2,2,6,6-tetramethyl-4-(2,2,2-trifluoroacetamido)-1-oxopiperidinium tetrafluoroborate (5), and its corresponding nitroxide (4) are reported. The solubility profile of 5 in solvents commonly used for alcohol oxidations differs substantially from that of Bobbitt's salt, 4-acetamido-2,2,6,6-tetramethyl-1-oxopiperidinium tetrafluoroborate (1). The rates of oxidation of a representative series of primary, secondary, and benzylic alcohols by 1 and 5 in acetonitrile solvent at room temperature have been determined, and oxoammonium salt 5 has been found to oxidize alcohols more rapidly than does 1. The rate of oxidation of meta- and para-substituted benzylic alcohols by either 1 or 5 displays a strong linear correlation to Hammett parameters (r > 0.99) with slopes (ρ) of -2.7 and -2.8, respectively, indicating that the rate-limiting step in the oxidations involves hydride abstraction from the carbinol carbon of the alcohol substrate.
- Lambert, Kyle M.,Stempel, Zachary D.,Kiendzior, Sadie M.,Bartelson, Ashley L.,Bailey, William F.
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p. 11440 - 11446
(2017/11/10)
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- Metal-free one-pot α-carboxylation of primary alcohols
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An efficient metal-free procedure for the formal α-carboxylation of primary alcohols has been developed. The method involves a one-pot oxidation/Passerini/hydrolysis sequence and provides access to α-hydroxy acids bearing a broad range of functional groups. A minor modification to the reaction conditions extends the range of accessible products to α-hydroxy esters.
- Van Der Heijden, Gydo,Kraakman, Jasper,Biemolt, Jasper,Ruijter, Eelco,Orru, Romano V. A.
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supporting information
p. 9716 - 9719
(2016/10/31)
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- PROCESSES FOR CONVERSION OF BIOLOGICALLY DERIVED MEVALONIC ACID
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The invention relates to a process comprising reacting mevalonic acid, or a solution comprising mevalonic acid, to yield a first product or first product mixture, optionally in the presence of a solid catalyst and/or at elevated temperature and/or pressure. The invention further relates to a process comprising: (a) providing a microbial organism that expresses a biosynthetic mevalonic acid pathway; (b) growing the microbial organism in fermentation medium comprising suitable carbon substrates, whereby biobased mevalonic acid is produced; and (c) reacting said biobased mevalonic acid to yield a first product or first product mixture.
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Paragraph 0112-0115
(2016/06/13)
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- Further insights into the organocatalytic reaction of 2,2-dimethyl-1,3-dioxan-5-one with α-silyloxy aldehydes
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Proline-catalysed reactions of dihydroxyacetone isopropylidene acetal, 1, with enantiopure α-silyloxy aldehydes 2/4/6/8 afford 90–95% yields of cross-aldol products (only one stereoisomer in each case), provided that 15 ± 10 equiv of H2O are pr
- Sánchez, Dani,Carneros, Héctor,Castro-Alvarez, Alejandro,Llàcer, Enric,Planas, Ferran,Vilarrasa, Jaume
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p. 5254 - 5258
(2016/11/11)
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- Synthesis of N-(2,2,2-trichloro-1-hydroxyethyl)aldimines and their derivatives
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The preparative procedure for the synthesis of N-(2,2,2-trichloro-1-hydroxyethyl)aldimines from the corresponding aldehyde, chloral, and ammonium acetate was developed. Preparative silylation and acylation of their hydroxy groups were acomplished for the first time. The possibility to use the synthesized O-trimethylsilyl and O-acetyl derivatives as the synthetic equivalents of N-nonsubstituted imines in the reactions with cyclopropenone was investigated.
- Firsova, Yu. N.,Engel,Lozinskaya,Sosonyuk,Proskurnina,Zefirov
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- Selective isomerization of epoxides using magnetically recyclable ZSM-5 zeolite catalyst
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The application of magnetically recyclable ZSM-5 zeolite (MZZ) for epoxide isomerization reaction was presented. This catalyst exhibited a high catalytic efficiency for liquid phase rearrangement of 2-methyl-2,3-epoxybutane and styrene oxide, as well as high efficiency in separation, recycling with long lifetime and no significant loss of catalytic activity. The influences of reaction conditions such as solvent, reaction time, catalyst loading and temperature on the efficiency of epoxide isomerization were also investigated. Moreover, it was noticeable that for the epoxides investigated the high catalytic activity observed over the MZZ catalyst (conversion over 98% after 2 h reaction for both of two epoxides) was accompanied by the achievement of high selectivities, typically 79% and 82% for 2-methyl-2,3-epoxybutane and styrene oxide respectively, towards desired products with commercial applications.
- Hoang, Phan Huy,Nguyen Xuan, Bach
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p. 78441 - 78447
(2015/10/05)
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- Ozonolysis of a Series of Methylated Alkenes: Reaction Rate Coefficients and Gas-Phase Products
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The gas-phase ozonolysis of three methylated alkenes, i.e., trans-2,2-dimethyl-3-hexene (22dM3H), trans-2,5-dimethyl-3-hexene (25dM3H), and 4-methyl-1-pentene (4M1P), has been investigated in the presence of sufficient hydroxyl radical scavenger in a laminar flow reactor at ambient temperature (296 ± 2 K) and P = 1 atm of dry air (RH ≤ 5%). Ozone levels in the reactor were monitored by an automatic analyzer. Alkene and gas-phase product concentrations were determined via online sampling either on three-bed adsorbent cartridges followed by thermodesorption and GC/FID-MS analysis or on 2,4-dinitrophenylhydrazine (DNPH) cartridges for subsequent HPLC/UV analysis. Reaction rate coefficients of (3.38 ± 0.12) × 10-17 for 22dM3H and (2.71 ± 0.26) × 10-17 for 25dM3H, both in cm3 molecule-1 s-1 units, have been obtained under pseudo-first-order conditions. Primary carbonyl products have been identified for the three investigated alkenes, and branching ratios are reported. In the case of 4M1P ozonolysis, the yield of a Criegee intermediate was indirectly determined. Kinetics and product study results are compared to those of literature when available. This work represents the first investigation of reaction products in the ozonolysis of 22dM3H, 25dM3H, and 4M1P in a flow reactor.
- Braure, Tristan,Riffault, Vronique,Tomas, Alexandre,Olariu, Romeo Iulian,Arsene, Cecilia,Bedjanian, Yuri,Coddeville, Patrice
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p. 596 - 605
(2015/08/06)
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- Managing the retro-pathway in direct catalytic asymmetric aldol reactions of thioamides
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Thioamides are the preferred pronucleophiles for direct catalytic asymmetric aldol reactions in the context of soft Lewis acid/hard Bronsted base cooperative catalysis. In-depth investigation of this proton-transfer catalysis, which is virtually in equilibrium, revealed that the prominence of the retro-aldol reaction depended on the substrate combination. The retro-aldol reaction is a serious issue in direct aldol reactions because the product distribution, including enantiomers and diastereomers, is governed by thermodynamic parameters, and the aldol products are obtained in much lower stereoselectivity compared with the kinetically controlled process. Herein we report the beneficial effect of an additive with a functional group architecture similar to that of the aldol adduct that suppresses the retro-aldol reaction by competitively binding to the catalyst. Strategic use of the additive led to high stereoselectivity, even when the combination of substrates was prone to the retro-aldol reaction.
- Bao, Youmei,Kumagai, Naoya,Shibasaki, Masakatsu
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p. 6124 - 6132
(2015/10/28)
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- Reactions of hydroxyl-containing compounds with tert-butyl hydroperoxide in the presence of chromium tetra-tert-butoxide
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Primary and secondary aliphatic, alkylaromatic, cyclic, and organoelement alcohols are efficiently oxidized by tert-butyl hydroperoxide in the presence of both equimolar and catalytic quantities of chromium tetra-tert-butoxide (C6H6, 20°C). α-Diols containing tertiary hydroxyl groups interact with this system via oxidative splitting of the carbon scaffold. The oxidation includes the stages of formation and decomposition of chromium-containing peroxy compounds. Further transformations of the carbonyl compounds depend on the structure of radicals in the molecules.
- Stepovik,Zaburdaeva,Fukin,Karaghiosoff
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p. 2547 - 2559
(2015/12/30)
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- Iron oxide catalyzed reduction of acid chlorides to aldehydes with hydrosilanes
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Iron-catalyzed reduction of acid chlorides to the corresponding aldehydes with a hydrosilane as a reducing agent has been developed. A simple mixture of a commercially available iron oxide (FeO) and tris(2,4,6-trimethoxyphenyl) phosphine (TMPP) as a catalyst realized the reduction of acid chlorides to the corresponding aldehydes under mild reaction conditions.
- Cong, Cong,Fujihara, Tetsuaki,Terao, Jun,Tsuji, Yasushi
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- METHOD FOR THE CATALYTIC REDUCTION OF ACID CHLORIDES AND IMIDOYL CHLORIDES
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The present application relates to methods for the catalytic reduction of acid chlorides and/or imidoyl chlorides. The methods comprise reacting the acid chloride or imidoyl chloride with a silane reducing agent in the presence of a catalyst such as [Cp(Pri3P)Ru(NCMe)2]+[PF6]?.
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Paragraph 0104
(2014/08/19)
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- S-aroylthiooximes: A facile route to hydrogen sulfide releasing compounds with structure-dependent release kinetics
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We report the facile preparation of a family of S-aroylthiooxime (SATO) H2S donors, which are synthesized via a click reaction analogous to oxime formation between S-aroylthiohydroxylamines (SATHAs) and aldehydes or ketones. Analysis of cysteine-triggered H2S release revealed structure-dependent release kinetics with half-lives from 8-82 min by substitution of the SATHA ring. The pseudo-first-order rate constants of substituted SATOs fit standard linear free energy relationships (p = 1.05), demonstrating a significant sensitivity to electronic effects.
- Foster, Jeffrey C.,Powell, Chadwick R.,Radzinski, Scott C.,Matson, John B.
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p. 1558 - 1561
(2014/04/17)
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- Selective reduction of carboxylic acids to aldehydes catalyzed by B(C 6F5)3
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B(C6F5)3 efficiently catalyzes hydrosilylation of aliphatic and aromatic carboxylic acids to produce disilyl acetals under mild conditions. Catalyst loadings can be as low as 0.05 mol %, and bulky tertiary silanes are favored to give selectively the acetals. Acidic workup of the disilyl acetals results in the formation of aldehydes in good to excellent yields.
- Bezier, David,Park, Sehoon,Brookhart, Maurice
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supporting information
p. 496 - 499
(2013/03/29)
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- Oxidation of primary alcohols to aldehydes with N-halamine-containing polymers
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Polymeric N-halamines have been previously employed for organic reactions such as sulfide oxidation. In the present study, we employed polymeric N-halamines to oxidize primary alcohols selectively to the corresponding aldehydes in excellent yields. After reaction, the polymers can be recycled and then reused for the next reaction process. Georg Thieme Verlag Stuttgart, New York.
- Akdag, Akin,?ztürk, Perihan
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p. 2451 - 2453
(2013/11/06)
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- Ugi four-component reaction of alcohols: Stoichiometric and catalytic oxidation/MCR sequences
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A new, simple, and efficient procedure for the one-pot Ugi four-component reaction of alcohols instead of aldehydes is described. Using a stoichiometric amount of IBX or only 1-2% of sodium 2-iodobenzenesulfonate in the presence of Oxone, a wide range of primary alcohols were oxidized to the aldehyde that were directly engaged in the Ugi four-component reaction to afford α-acetamidoamides in good to excellent yields.
- Drouet, Fleur,Masson, Géraldine,Zhu, Jieping
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supporting information
p. 2854 - 2857
(2013/07/26)
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- Formation of an alkyne during degradation of metal-alkylidyne complexes
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The compound [(Ot-Bu)3WCt-Bu] (1) (t-Bu = C(CH3) 3) decomposes upon contact with water and several organic products are formed, including di-tert-butylacetylene, t-BuCCt-Bu. This process is reminiscent of the degradation of trinuclear metal-alkylidyne complexes in which free carbynes are ejected into solution, couple and form alkynes along with many other products. The reactivity pattern of the resulting t-BuC carbynes that includes extensive hydrogen abstraction, cleavage of alkynes and lack of reactivity towards alkenes is indicative of a quartet (S = 3/2) spin state. A similar spin state was assigned to other RC (R = alkyl) species that were produced by degrading M3-alkylidyne (M = transition metal) complexes in water. t-BuCCt-Bu is also produced during thermal decomposition of solid 1. In 1977 Fischer and co-workers reported a very similar process in which solids of Br(CO)4CrCR1 and Br(CO)4CrCR2 were co-thermolyzed to produce R1CCR2, R 1CCR1, and R2CCR2. Fischer had considered the involvement of free carbynes in the making of the alkynes but later resorted to other explanations. The current results suggest that his original proposal is indeed valid.
- Levy, Ophir,Musa, Sanaa,Bino, Avi
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p. 12248 - 12251
(2013/09/02)
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- Tunneling control of chemical reactions: C-H insertion versus H-tunneling in tert-butylhydroxycarbene
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Elusive tert-butylhydroxycarbene was generated in the gas phase via high-vacuum flash pyrolysis of tert-butylglyoxylic acid at 960 °C. The pyrolysis products were subsequently matrix isolated in solid Ar at 11 K and characterized by means of IR spectroscopy. While still being exposed to the harsh pyrolysis conditions, the hydroxycarbene undergoes CH-insertion to dimethylcyclopropanol, as well as a CC-insertion to novel methylbutenol, with activation barriers of 23.8 and 31.0 kcal mol-1, respectively. Once embedded in the cold Ar matrix, the carbene transforms to its isomer pivaldehyde not only by photolysis, but it also cuts through the barrier of 27.3 kcal mol-1 by quantum mechanical tunneling. The temperature independent half-life is measured as 1.7 h; the tunneling pathway was entirely blocked upon O-deuteration. The experimental half-life of tert-butylhydroxycarbene was verified by tunneling computations applying the Wentzel-Kramers-Brillouin formalism on the minimum energy path evaluated at the computationally feasible M06-2X/6-311++G(d,p) level of theory. Our experimental findings are supported by relative energy computations at the CCSD(T)/cc-pVDZ level of theory. The Royal Society of Chemistry 2013.
- Ley, David,Gerbig, Dennis,Schreiner, Peter R.
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p. 677 - 684
(2013/04/10)
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- Ketonic decarboxylation reaction mechanism: A combined experimental and DFT study
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The ketonic decarboxylation of carboxylic acids has been carried out experimentally and studied theoretically by DFT calculations. In the experiments, monoclinic zirconia was identified as a good catalyst, giving high activity and high selectivity when compared with other potential catalysts, such as silica, alumina, or ceria. It was also shown that it could be used for a wide range of substrates, namely, for carboxylic acids with two to eighteen carbon atoms. The reaction mechanism for the ketonic decarboxylation of acetic acid over monoclinic zirconia was investigated by using a periodic DFT slab model. A reaction pathway with the formation of a β-keto acid intermediate was considered, as well as a concerted mechanism, involving simultaneous carbon-carbon bond formation and carbon dioxide elimination. DFT results showed that the mechanism with the β-keto acid was the kinetically favored one and this was further supported by an experiment employing a mixture of isomeric (linear and branched) pentanoic acids. This way or that? Monoclinic zirconia has great potential as a catalyst for ketonic decarboxylation of carboxylic acids (see picture). A combined experimental and DFT study shows a route involving a β-keto acid intermediate as the kinetically preferred reaction pathway. Copyright
- Pulido, Angeles,Oliver-Tomas, Borja,Renz, Michael,Boronat, Mercedes,Corma, Avelino
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p. 141 - 151
(2013/03/14)
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- Chemoselective ruthenium-catalyzed reduction of acid chlorides to aldehydes with dimethylphenylsilane
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A variety of aromatic and alkyl acid chlorides can be selectively converted into aldehydes using dimethylphenyl silane (HSiMe2Ph) as the reducing reagent in the presence of the cationic ruthenium catalyst {Cp[(i-Pr)3P]Ru(NCMe)2}+ [PF6] -. The reactions proceed under very mild conditions and are tolerant to many functional groups. Copyright
- Gutsulyak, Dmitry V.,Nikonov, Georgii I.
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experimental part
p. 607 - 611
(2012/04/23)
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- Palladium-catalyzed reduction of acid chlorides to aldehydes with hydrosilanes
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An efficient synthesis of aldehydes from acid chlorides with hydrosilanes as a reducing agent in the presence of a palladium catalyst has been achieved. A simple mixture of commercially available Pd(dba)2 and Mes 3P as a catalyst realized the reduction of various acid chlorides including aliphatic acid chlorides and a, P-unsaturated acid chlorides to the corresponding aldehydes in good to high yields under mild reaction conditions. Georg Thieme Verlag Stuttgart ? New York.
- Fujihara, Tetsuaki,Cong, Cong,Iwai, Tomohiro,Terao, Jun,Tsuji, Yasushi
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supporting information
p. 2389 - 2392
(2013/07/19)
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- Selective oxoammonium salt oxidations of alcohols to aldehydes and aldehydes to carboxylic acids
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The oxidation of alcohols to aldehydes using stoichiometric 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate (1) in CH2Cl2 at room temperature is a highly selective process favoring reaction at the carbinol center best able to accommodate a positive charge. The oxidation of aldehydes to carboxylic acids by 1 in wet acetonitrile is also selective; the rate of the process correlates with the concentration of aldehyde hydrate. A convenient and high yield method for oxidation of alcohols directly to carboxylic acids has been developed.
- Qiu, Joseph C.,Pradhan, Priya P.,Blanck, Nyle B.,Bobbitt, James M.,Bailey, William F.
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supporting information; experimental part
p. 350 - 353
(2012/03/09)
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- Elucidating the mechanism of reversible oxiranations via magnetization transfer spectroscopy
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The reversible [2 + 1] cycloadditions between an N,N′-diamidocarbene (DAC) and eight aldehydes were examined using NMR spectroscopy. Variable temperature magnetization transfer experiments revealed higher exchange rates and lower activation barriers when electron-deficient aldehydes were employed. Likewise, competitive equilibrium studies indicated a thermodynamic preference for electron-deficient aryl and sterically unhindered alkyl aldehydes compared to more electron-rich or bulkier substrates. Collectively, these and other data collected were consistent with the oxiranation process proceeding in an asynchronous manner.
- Chase, Daniel T.,Moerdyk, Jonathan P.,Bielawski, Christopher W.
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supporting information
p. 5510 - 5513
(2013/01/15)
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- Development of a new flow reactor for kinetic studies. Application to the ozonolysis of a series of alkenes
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A new flow reactor has been developed to study ozonolysis reactions at ambient pressure and room temperature (297 ± 2 K). The reaction kinetics of O3 with 4-methyl-1-pentene (4M1P), 2-methyl-2-pentene (2M2P), 2,4,4-trimethyl-1-pentene (tM1P), 2,4,4-trimethyl-2-pentene (tM2P) and α-pinene have been investigated under pseudo-first-order conditions. Absolute measurements of the rate coefficients have been carried out by recording O3 consumption in excess of organic compound. Alkene concentrations have been determined by sampling adsorbent cartridges that were thermodesorbed and analyzed by gas-chromatography coupled to flame ionization detection. Complementary experimental data have been obtained using a 250 L Teflon smog chamber. The following ozonolysis rate coefficients can be proposed (in cm3 molecule-1 s-1): k4M1P = (8.23 ± 0.50) × 10-18, k2M2P = (4.54 ± 0.96) × 10-16, ktM1P = (1.48 ± 0.11) × 10-17, ktM2P = (1.25 ± 0.10) × 10 -16, and kα-pinene = (1.29 ± 0.16) × 10-16, in very good agreement with literature values. The products of tM2P ozonolysis have been investigated, and branching ratios of (21.4 ± 2.8)% and (73.9 ± 7.3)% have been determined for acetone and 2,2-dimethyl-propanal, respectively. Additionally, a new nonoxidized intermediate, 2-methyl-1-propene, has been identified and quantified. A topological SAR analysis was also performed to strengthen the consistency of the kinetic data obtained with this new flow reactor.
- Duncianu, Marius,Olariu, Romeo Iulian,Riffault, Veronique,Visez, Nicolas,Tomas, Alexandre,Coddeville, Patrice
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experimental part
p. 6169 - 6179
(2012/08/28)
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- Kinetics and mechanism of the oxidation of aliphatic primary alcohols by imidazolium fluorochromate
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The oxidation of nine aliphatic primary alcohols by imidazolium fluorochromate (IFC) in dimethylsulphoxide leads to the formation of corresponding aldehydes. The reaction is first order with respect to IFC. A Michaelis-Menten type kinetics is observed with respect to alcohols. The reaction is promoted by hydrogen ions; the hydrogen-ion dependence has the form : kobs = a + b [H+]. The oxidation of [1,1- 2H2]ethanol (MeCD2OH) exhibits a substantial primary kinetic isotope effect (kH/kD = 5.87 at 298 K). The reaction has been studied in nineteen different organic solvents. The solvent effect was analysed using Taft's and Swain's multiparametric equations. The rate of oxidation is susceptible to both polar and steric effects of the substituents. A suitable mechanism has been proposed.
- Gehlot,Gilla,Mishra,Sharma, Vinita
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experimental part
p. 685 - 692
(2012/04/04)
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- Synthesis of aliphatic aldehydes
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An easy procedure for synthesis of aliphatic aldehydes has been realized in heterogeneous medium from dimethyl sulfoxide, halides and bicarbonate anions. The mixture was irradiated with microwave for a short time and lead to desired products. A number of aliphatic aldehydes were obtained in mild conditions with a good yield.
- Bratulescu, George
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experimental part
p. 2233 - 2234
(2012/02/17)
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- Oxidation of aliphatic primary alcohols by morpholinium chlorochromate: A kinetic and mechanistic approach
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The oxidation of nine aliphatic primary alcohols by morpholinium chlorochromate (MCC) in dimethylsulfoxide leads to the transformation of alcohols to the corresponding aldehydes. The reaction is first order with respect to both MCC and the alcohol both. The reaction is catalysed by hydrogen ions. The hydrogen-ion dependence has the form: kobs = a + A[H +]. The oxidation of [1,1-2H2]ethanol (MeCD2OH) exhibits a substantial primary kinetic isotope effect. The reaction has been studied in nineteen different organic solvents. The solvent effect was analysed using Taft's and Swain's multiparametric equations. The rate of oxidation is susceptible to both polar and steric effects of the substituents. A suitable mechanism has been proposed.
- Choudhary,Yajurvedi,Soni,Agarwa,Sharma, Vinita
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experimental part
p. 1061 - 1066
(2011/05/05)
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- Nanocrystalline ZSM-5: A catalyst with high activity and selectivity for epoxide rearrangement reactions
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Nanocrystalline ZSM-5 (~20-50 nm) has been tested as a catalyst in the liquid phase rearrangement of 1,2-epoxyoctane, 2-methyl-2,3-epoxybutane and isophorone oxide together with a microcrystalline ZSM-5 sample (~5 μm) employed as a reference. Whereas this last material shows a low activity for the three epoxide rearrangement reactions considered, nanocrystalline ZSM-5 leads in all cases to high epoxide conversion. This different catalytic performance is attributed to the differences in the accessibility of the reactant molecules to the catalyst active sites. The smallest crystal size of the nanocrystalline zeolite contributes favourably to both the formation of a high external surface area, with no steric constraints, and to a faster intracrystalline diffusion of the epoxide molecules towards the acid sites located within the zeolite micropores. When sterically hindered epoxides are tested, the catalytic rearrangement occurs mainly on the external surface of the nanocrystalline zeolite. Moreover, it is remarkable that for the three epoxides investigated the high catalytic activity observed over nanocrystalline ZSM-5 is accompanied by the attainment of high selectivities, typically around or over 80%, towards products with commercial applications.
- Serrano, David P.,van Grieken, Rafael,Melero, Juan Antonio,García, Alicia,Vargas, Carolina
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scheme or table
p. 68 - 74
(2010/06/16)
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- Synthetic and mechanistic aspects of acid-catalyzed disproportionation of dialkyl diarylmethyl ethers: A combined experimental and theoretical study
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The disproportionation reactions of various dialkyl diarylmethyl ethers have been carried out in the presence of a catalytic amount (10 mol-%) of o-benzenedisulfonimide as a Bronsted acid catalyst; the reaction conditions were mild, and the yields of the diarylmethane target products were good. The catalyst was easily recovered and purified, ready to be used in further reactions. The theoretical study confirmed that the reaction proceeds in two steps: The formation of a carbocation from the protonated ether followed by hydride transfer. Although the hydride transfer is the rate-determining step, it is the stability of the carbocation that determines the reaction rate and therefore the yields.
- Barbero, Margherita,Bazzi, Stefano,Cadamuro, Silvano,Dughera, Stefano,Ghigo, Giovanni
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experimental part
p. 4346 - 4351
(2011/02/24)
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- Syntheses and15N NMR Spectra of Iminodiaziridines - Ring-Expansions of 1-Aryl-3-iminodiaziridines to 1H- and 3aH-Benzimidazoles, 2H-Indazoles, and 5H-Dibenzo[d,f] [1,3]diazepines
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Iminodiaziridines are synthesized, by (i) 1,3-dehydrochlorination with potassium, teri-butoxide of N-chloroguanidines, generated in situ from. N,N′,N″-substituted guanidines with tert-butyl hypochlorite, and (ii) base-mediated 1,3-elimination of sulfuric acid from N,N',N″- substituted hydroxyguanidine O-sulfonic acids. At elevated temperatures, (alkylimino)diaziridines undergo valence isomerization by 1,3shift, [2+1] cycloelimination to afford isocyanides and diazenes, and ring-opening elimination to yield alkylideneguanidines. N′-Aryl-N-hydroxyguanidine O-sulfonic acids furnish (N-arylimino)diaziridines, but no 1-aryl-3- iminodiaziridines, instead giving rearranged isomere. Precursors containing perdeuterated feri-butyl groups give rearranged products that show complete scrambling. This indicates that l-aryl-3iminodiaziridines are intermediates that undergo very rapid I degenerate valence isomerization. Provided that the ortho aryl positions are substituted, high yields of (arylimino)diaziridines are obtained, along with 2-imino-2,3-dihydro-3aHbenzimidazoles, Otherwise, 2-amino-lH-benzimidazoles and strongly fluorescent 3-amino-2H-indazoles, originating from rearrangements of the elusive l-aryl-3-iminodiaziridines, predominate. N',N″-Diaryl-N-hydroxyguanidine O-sulfonic acids give only rearranged products: a 2-amino-1H-benzimidazole and a 6-amino-5H-dibenzo[d,f][1. 3]diazepine if aryl = phenyl, or a 2-imino-2,3-dihydro-3aH-benzimidazole if aryl = mesityl. 3aH-Benzimidazoles slowly dimerize through Diels-Alder reactions. 15N NMR signals were assigned, to the syn and anti ring nitrogen atoms of iminodiaziridines with the help of a combination of homonuclear NOE and HNHMBC or HN-gHMBC experiments.
- Quast, Helmut,Ross, Karl-Heinz,Philipp, Gottfried,Hagedorn, Manfred,Hahn, Harald,Banert, Klaus
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supporting information; experimental part
p. 3940 - 3952
(2010/03/01)
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- Studies of 2-substituted 1,3-oxazolidin-5-ones and 1,3-oxazinan-6-ones as precursors for the synthesis of N-alkyl-β-amino acids
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1,3-Oxazolidin-5-ones and 1,3-oxazinan-6-ones have been shown to be useful precursors for the synthesis of N-methyl α- and β-amino acids, respectively. The methodology has now been expanded to allow for the synthesis of N-alkyl-β-amino acids. Copyright Ta
- Hughes, Andrew B.,Sleebs, Brad E.
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experimental part
p. 48 - 60
(2009/04/06)
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- DEAD-(cat)ZnBr2 an efficient system for the oxidation of alcohols to carbonyl compounds
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The combination of diethyl azodicarboxylate (DEAD) and a catalytic amount of ZnBr2 is an efficient system for the dehydrogenation of alcohols to the corresponding carbonyl compounds. The scope and limitations of this process have been studied.
- Cao, Hai Thuong,Grée, René
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experimental part
p. 1493 - 1494
(2009/06/18)
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- Synthesis and reactivity of an unprecedented osmium(VIII) alkylidene
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The synthesis of a family of Os(VIII) alkylidene complexes, the highest oxidation state alkylidenes known to date, and their reactivity toward small organic molecules are reported.
- Martin, Véronique,Blakey, Simon
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body text
p. 6800 - 6803
(2009/04/06)
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- Efficient and selective Al-catalyzed alcohol oxidation via oppenauer chemistry
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A highly active and selective Al-based catalytic Oppenauer (O) oxidation is reported. Quantitative and selective oxidations of a variety of benzylic, propargylic, allylic, and aliphatic primary and secondary alcohols were achieved using nitrobenzaldehyde derivatives as the oxidant and simple aluminum compounds as precatalysts. Copyright
- Graves, Christopher R.,Zeng, Bi-Shun,Nguyen, SonBinh T.
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p. 12596 - 12597
(2008/02/03)
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- Kinetics and mechanism of the oxidation of aliphatic primary alcohols by benzyltriethylammonium chlorochromate
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The oxidation of nine aliphatic primary alcohols by benzyltriethylammonium chlorochromate (BTEACC) in dimethylsulfoxide (DMSO) leads to the formation of corresponding aldehydes. The reaction is first order with respect to both BTEACC and the alcohol. The reaction is catalysed by hydrogen ions. The hydrogen-ion dependence has the form: kobs = a + b [H+]. The oxidation of [1,1-2H2]ethanol (MeCD2OH) exhibits a substantial primary kinetic isotope effect. The reaction has been studied in nineteen different organic solvents. The solvent effect was analysed using Taft's and Swain's multiparametric equations. The rate of oxidation is susceptible to both polar and steric effects of the substituents. A suitable mechanism has been proposed.
- Mishra,Sharma, Monica,Sharma, Vinita
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p. 364 - 368
(2007/10/03)
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- Process for cleaving thiazolidines
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Preparation of α-substituted cysteine derivatives takes place by acidic hydrolysis of thiazolidines, wherein the hydrolysis is effected in the presence of a further phase comprising an organic solvent and a vapor comprising water, acid, organic solvent and aldehyde is removed from the reaction mixture, or a vapor comprising water, acid and aldehyde is removed from the reaction mixture and the vapor or its condensate is subsequently contacted with a phase comprising an organic solvent. The process requires less hydrolysis time and allows for recycle and/or recovery of acid and by product aldehyde.
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Page/Page column 4
(2008/06/13)
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- Delayed autocatalytic behavior of Mn(II) ions at a critical ratio: The effect of structural isomerism on permanganic oxidation of L-norleucine
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The kinetics of the permanganic oxidation process of L-norleucine, L-leucine, L-isoleucine, and L-tert-leucine in strong acid medium has been investigated using a spectrophotometric technique. Conclusive evidences have proven autocatalytic activity of Mn(II) for these reactions in strong acid medium analogous to weak acid medium, but in the former, ratio of Mn(II) to amino acid concentration must reach a certain amount for autocatalytic phenomenon to emerge, which we call "critical ratio." This critical ratio depends on the nature of the amino acid employed. Thus considering "delayed autocatalytic behavior" of Mn(II) ions, rate equations satisfying observations for both catalytic and noncatalytic routes have been presented. Kinetic data in a noncatalytic pathway have been fitted to a biparametric equation including inductive, steric, and hyperconjugation correction effects, and it is determined that by shifting the side branch on a carbon chain toward an α-carbon atom (adjacent to amino acid's functional group) and also adding branches to the α-carbon atom, the reaction rate in the noncatalytic pathway decreases. Inductive and steric hindrance factors in amino acid's carbon chain are effective on processes' rate both in catalytic and noncatalytic pathways.
- Bahrami, Homayoon,Zahedi, Mansour
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- Technical production of aldehydes by continuous bleach oxidation of alcohols catalyzed by 4-hydroxy-TEMPO
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Aldehydes can be easily prepared from the corresponding alcohols in good to excellent yields by oxidation with technical bleach and catalytic amounts of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (1b, 4-hydroxy TEMPO, "HOT"). Whereas the well-known batch process performed on lab scale is not suitable for the technical synthesis especially of activated β-substituted aldehydes, this transformation can be performed continuously in a simple tube reactor. This layout meets all requirements necessary for the process, i.e., turbulent mixing of the biphasic mixture, removal of heat, short contact times, and high output. Thus, a single tube of 3 mm diameter renders about 60 mol of aldehyde per day.
- Fritz-Langhals, Elke
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p. 577 - 582
(2012/12/25)
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- Application of alkoxy-λ6-sulfanenitriles as strong alkylating reagents
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Alkoxy-λ6-sulfanenitriles were found to be versatile alkylating reagents toward various nucleophiles bearing at least one proton such as methanol, phenol, thiophenols, carboxylic acids, ptoluenesulfonic acid, hydrochloric acid, and primary and secondary amines. Reactivity of the alkoxy group of the λ6-sulfanenitriles showed an opposite trend to the usual SN2 character, i.e. Me (la), Pr (1b), and Bu (1d) ? i-Pr (1c). In the presence of p-TsOH, alkyl tosylates were predominantly formed instead of the alkylation products of nucleophiles. In addition, even a sterically hindered substrate, neopentyloxy-λ6-sulfanenitrile, was found to undergo an SN2 reaction toward thiophenol without any rearrangement product to give neopentyl phenyl sulfide in good yield.
- Hao, Wei,Fujii, Takayoshi,Dong, Tiaoling,Wakai, Youko,Yoshimura, Toshiaki
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p. 193 - 198
(2007/10/03)
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