- Catalytic activity and anion activation in SN2 reactions promoted by complexes of silicon polypodands. Comparison with traditional polyethers
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The catalytic activity of silicon polypodands was evaluated in anion-promoted reactions under solid-liquid phase-transfer catalysis (SL-PTC) conditions and compared with that exhibited by common PTC agents. Results showed that these many-armed ligands are
- Maia, Angelamaria,Landini, Dario,Betti, Cecilia,Leska, Boguslawa,Schroeder, Grzegorz
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Read Online
- OH-radical-induced oxidation of methanesulfinic acid. The reactions of the methanesulfonyl radical in the absence and presence of dioxygen
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Hydroxyl radicals were generated radiolytically in N2O-saturated solutions. As shown by pulse radiolysis, methanesulfinic acid reacts with·OH (k = 5.3 × 109 dm3 mol-1 s-1) and N3· giving rise to an intermediate which has an absorption maximum at 330 nm (Gε ≈ 5.2 × 10-5 m2 mol-1). This is attributed to the methanesulfonyl radical, CH3S(O)O·. Pulse radiolysis with conductometric detection indicates that CH3S(O)O· is formed in only ～80% yield. This is confirmed by scavenging experiments with Fe(CN)64-, ascorbate and sulfite, which are oxidised by CH3S(O)O· with rate constants of ～2 × 109 dm3 mol-1 s-1. Steady-state radiolysis of methanesulfinic acid shows that methanesulfonic acid is the major product (G = 2.1 × 10-7 mol J-1). Further products are sulfate (0.7 × 10-7 mol J-1), methane (0.3 × 10-7 mol J-1), ethane (0.08 × 10-7 mol J-1) and dimethyl sulfone (not quantified). It is suggested that an OH-adduct is formed initially which mainly eliminates OH-, but also decomposes yielding ·CH3 and bisulfite. The formation of methanesulfonic acid can be explained by a disproportionation of the methanesulfonyl radicals via recombination and subsequent hydrolysis. In the presence of dioxygen, a chain reaction occurs whereby 2 mol methanesulfonic acid are formed per 1 mol dioxygen consumed. G(methanesulfonic acid) ≈ 250 × 10-7 mol J-1 was found to be independent of dose rate (0.011-0.165 Gy s-1), methanesulfinic acid concentration [(0.1-4) × 10-3 mol dm-3] and dioxygen concentration. An efficient chain process was also observed upon electron beam irradiation [G(methanesulfonic acid) ≈ 200 × 10-7 mol J-1 at 0.8 Gy per pulse and 75 × 10-7 mol J-1 at 9 Gy per pulse (pulse duration 2 μs)]. It is proposed that the oxidation of the substrate by the methylsulfonylperoxyl radical, CH3S(O2)OO·, to give the strongly oxidising CH3S(O2)O· radical, initiates the chain reaction, with the latter propagating the chain by reacting with a substrate molecule to give methanesulfonic acid and the methanesulfonyl radical. Branching and partial removal of the chain-carrying CH3S(O2)O· radicals by H-abstraction from the substrate is suggested as the likely path leading to chain termination. Oxidation of methanesulfinate by ozone (k = 2 × 106 dm3 mol-1 s-1) occurs only by O-atom transfer, and an electron transfer that would start a chain reaction was not observed.
- Flyunt, Roman,Makogon, Oksana,Schuchmann, Man Nien,Asmus, Klaus-Dieter,Von Sonntag, Clemens
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Read Online
- Predicting the hydrolytic breakdown rates of organophosphorus chemical warfare agent simulants using association constants derived from hydrogen bonded complex formation events
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Organophosphorus (OP) chemical warfare agents (CWAs) represent an ongoing global threat, through either purposeful environmental release or the need to dispose of historic stockpiles. This presents a need for the development of novel decontamination technologies. Due to the toxic nature and legal limitations placed on OP CWAs, the use of appropriate OP simulants that mimic the reactivity but not the toxicity of the agents themselves is vital to decontamination studies. Herein, we show that association constants derived from non-specific hydrogen bonded complexation events may be used as parameters within models to predict simulant reactivity. We also discuss the limitations that should be placed on such data.
- Chu, Dominique F.,Clark, Ewan R.,Ellaby, Rebecca J.,Hiscock, Jennifer,Pépés, Antigoni
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- Discovery, Synthesis and Evaluation of a Ketol-Acid Reductoisomerase Inhibitor
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Ketol-acid reductoisomerase (KARI), the second enzyme in the branched-chain amino acid biosynthesis pathway, is a potential drug target for bacterial infections including Mycobacterium tuberculosis. Here, we have screened the Medicines for Malaria Venture Pathogen Box against purified M. tuberculosis (Mt) KARI and identified two compounds that have Ki values below 200 nm. In Mt cell susceptibility assays one of these compounds exhibited an IC50 value of 0.8 μm. Co-crystallization of this compound, 3-((methylsulfonyl)methyl)-2H-benzo[b][1,4]oxazin-2-one (MMV553002), in complex with Staphylococcus aureus KARI, which has 56 % identity with Mt KARI, NADPH and Mg2+ yielded a structure to 1.72 ? resolution. However, only a hydrolyzed product of the inhibitor (i.e. 3-(methylsulfonyl)-2-oxopropanic acid, missing the 2-aminophenol attachment) is observed in the active site. Surprisingly, Mt cell susceptibility assays showed that the 2-aminophenol product is largely responsible for the anti-TB activity of the parent compound. Thus, 3-(methylsulfonyl)-2-oxopropanic acid was identified as a potent KARI inhibitor that could be further explored as a potential biocidal agent and we have shown 2-aminophenol, as an anti-TB drug lead, especially given it has low toxicity against human cells. The study highlights that careful analysis of broad screening assays is required to correctly interpret cell-based activity data.
- Bayaraa, Tenuun,Kurz, Julia L.,Patel, Khushboo M.,Hussein, Waleed M.,Bilyj, Jessica K.,West, Nicholas P.,Schenk, Gerhard,McGeary, Ross P.,Guddat, Luke W.
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p. 8958 - 8968
(2020/07/04)
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- Methanesulfonyl Iodide
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Methanesulfonyl iodide is produced in aqueous solutions from the reaction of triiodide with methanesulfinate. Dichroic crystals of (CH3SO2I)4·KI3·2I2 are formed from KI/I2 solutions with high concentrations of CH3SO2-, while dichroic crystals of (CH3SO2I)2·RbI3 are formed from RbI/I2 solutions. X-ray crystallography of these two compounds shows that the CH3SO2I molecules coordinate through their oxygen atoms to the metal cations and that the S-I bond length is 2.44 ?. At low concentrations of CH3SO2-, the solutions remain homogeneous and the sulfonyl iodide is formed in a rapid equilibrium: CH3SO2- + I3- ? CH3SO2I + 2I-, KMSI = 1.07 ± 0.01 M at 25 °C (μ = 0.1 M, NaClO4). The sulfonyl iodide solutions display an absorbance maximum at 309 nm with a molar absorptivity of 667 M-1 cm-1. Stopped-flow studies reveal that the equilibrium is established within the dead time of the instrument (～2 ms). Solutions of CH3SO2I decompose slowly to form the sulfonate: CH3SO2I + H2O → CH3SO3- + I- + 2H+, khyd. In dilute phosphate buffer, this decomposition occurs with khyd = 2.0 × 10-4 s-1 the decomposition rate shows an inverse-squared dependence on [I-] because of the KMSI equilibrium.
- Rajakaruna, Pradeepa,Gorden, John D.,Stanbury, David M.
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supporting information
p. 14752 - 14759
(2019/11/11)
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- Scaled-up electrochemical reactor with a fixed bed three-dimensional cathode for electro-Fenton process: Application to the treatment of bisphenol A
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In this study, we report on the development of an open undivided electrochemical reactor with a compact fixed bed of glassy carbon pellets as three-dimensional cathode for the application of electro-Fenton process. Bisphenol A (BPA) was chosen as model molecule in order to improve its efficiency to the treatment of persistent pollutants. The study of the BPA removal efficiency in function of the applied current intensity was investigated in order to determine the limiting current of O2 reduction (optimal conditions of H2O2 production at flow rate of 0.36?m3.h?1) which was 0.8?A (0.5?A/100?g of glassy carbon pellets). Many parameters have been carried out using this electro-Fenton reactor namely degradation kinetics, influence of anodic reactions on DSA, effect of initial pollutant concentration. In the optimal current condition, the global production rate of H2O2 and [rad]OH was investigated. The yield of electro-Fenton reaction (conversion of H2O2 to [rad]OH) was very high (>?90%). The absolute rate of BPA degradation was determined as 4.3?×?109?M?1?s?1. COD, TOC and BOD5 measurements indicated that only few minutes of treatment by electro-Fenton process were needed to eliminate BPA for dilute solutions (10 and 25?mg.L?1). In this case, the biodegradability of the treated solutions occurred rapidly. For higher concentration levels, an efficient removal of BPA appeared for treatment time higher than 1?hour and more than 90?minutes were necessary to obtain the biodegradability of BPA solutions. In optimum conditions, the scale-up of the electrochemical reactor applied to electro-Fenton process was suggested and depended on the concentration level of the pollutant. The operating parameters of the scaled-up reactor might be deduced from the new section of each fixed bed exposed to the flow, from values of liquid flow velocity and from the corresponding limiting current density obtained with the reactor at laboratory scale. The compact fixed bed cathode in an open undivided electrochemical reactor appears as an appropriate solution as pre-treatment electro-Fenton process followed by the biological treatment of persistent pollutant.
- Chmayssem, Ayman,Taha, Samir,Hauchard, Didier
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p. 435 - 442
(2017/01/09)
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- The reduced flavin-dependent monooxygenase SfnG converts dimethylsulfone to methanesulfinate
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The biochemical pathway through which sulfur may be assimilated from dimethylsulfide (DMS) is proposed to proceed via oxidation of DMS to dimethylsulfoxide (DMSO) and subsequent conversion of DMSO to dimethylsulfone (DMSO2). Analogous chemical oxidation processes involving biogenic DMS in the atmosphere result in the deposition of DMSO2 into the terrestrial environment. Elucidating the enzymatic pathways that involve DMSO2 contribute to our understanding of the global sulfur cycle. Dimethylsulfone monooxygenase SfnG and flavin mononucleotide (FMN) reductase MsuE from the genome of the aerobic soil bacterium Pseudomonas fluorescens Pf0-1 were produced in Escherichia coli, purified, and biochemically characterized. The enzyme MsuE functions as a reduced nicotinamide adenine dinucleotide (NADH)-dependent FMN reductase with apparent steady state kinetic parameters of Km = 69 μM and kcat/Km = 9 min?1 μM ?1 using NADH as the variable substrate, and Km = 8 μM and kcat/Km = 105 min?1 μM ?1 using FMN as the variable substrate. The enzyme SfnG functions as a flavoprotein monooxygenase and converts DMSO2 to methanesulfinate in the presence of FMN, NADH, and MsuE, as evidenced by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The results suggest that methanesulfinate is a biochemical intermediate in sulfur assimilation.
- Wicht, Denyce K.
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p. 159 - 166
(2016/07/22)
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- Chloride triggered reversible switching from a metallosupramolecular [Pd2L4]4+ cage to a [Pd2L2Cl4] metallo-macrocycle with release of endo- and exo-hedrally bound guests
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A metallosupramolecular [Pd2L4]4+ cage can be cleanly converted into a [Pd2L2Cl4] metallo-macrocycle upon addition of chloride ions. The process is reversible, treatment of the [Pd2L2Cl4] macrocycle with silver(i) ions regenerates the [Pd2L4]4+ cage. Additionally, it is shown that guest molecules could be released on chloride triggered cage dis-assembly and taken up anew on re-assembly. This journal is
- Preston, Dan,Fox-Charles, Alyssa,Lo, Warrick K. C.,Crowley, James D.
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supporting information
p. 9042 - 9045
(2015/05/27)
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- POLYMYXIN DERIVATIVES AND USES THEREOF
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The present invention relates to a polymyxin derivative and to a combination product comprising at least two such derivatives. The invention further relates to a method for treating, alleviating or ameliorating an infection in a subject caused by a Gram-negative bacterium, by administering a therapeutically effective amount of a derivative according to the present invention to said subject; to a method for sensitizing Gram-negative bacteria to an antibacterial agent by administering, simultaneously or sequentially in any order a therapeutically effective amount of said antibacterial agent and a derivative according to the present invention to said subject; to methods for developing novel antibiotics; for reducing the nephrotoxicity, for improving the pharmacokinetic properties of natural polymyxins and octapeptins; and for sensitizing clinically important bacteria to a host defense mechanism complement present in serum. Finally, the invention relates to a process for preparing such polymyxin derivatives.
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(2014/06/24)
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- POLYMYXIN DERIVATIVES AND USES THEREOF
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The present invention relates to a polymyxin derivative wherein R1, R2 and R3 are optional and R1, R2, R3, R5, R8 and R9 are cationic or neutral amino acid residues selected so that the total number of positive charges at physiological pH is at least two but no more than three; and to a combination product comprising at least two such derivatives. The invention further relates to a method for treating, alleviating or ameliorating an infection in a subject, caused by a Gram-negative bacterium by administering a therapeutically effective amount of a derivative according to the present invention to said subject; to a method for sensitizing Gram-negative bacteria to an antibacterial agent by administering, simultaneously or sequentially in any order a therapeutically effective amount of said antibacterial agent and a derivative according to the present invention to said subject; to methods for developing novel antibiotics; for reducing the nephrotoxicity, for improving the pharmacokinetic properties of natural polymyxins and octapeptins; and for sensitizing clinically important bacteria to a host defense mechanism complement present in serum. Finally, the invention relates to a process for preparing such polymyxin derivatives.
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- SHORT FATTY ACID TAIL POLYMYXIN DERIVATIVES AND USES THEREOF
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The present invention relates to a polymyxin derivative wherein the derivative has a total of three positive charges at physiological pH and wherein the terminal moiety (D) of the derivative comprises a total of 1 to 5 carbon atoms; and to a combination product comprising at least two such derivatives. The invention further relates to a method for sensitizing Gram-negative bacteria to an antibacterial agent by administering, simultaneously or sequentially in any order a therapeutically effective amount of said antibacterial agent and a derivative according to the present invention to said subject; to methods for developing novel antibiotics; and for sensitizing clinically important bacteria to a host defense mechanism complement present in serum. The invention also relates to a method of treating a subject for a gram-negative bacterial infection by administering a polymyxin derivative of the invention in combination with a second antibacterial agent. Finally, the invention relates to a process for preparing such polymyxin derivatives.
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- PREPARATION OF A SATURATED ALDEHYDE
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The invention relates to a compound according to Formula (IX) and salts thereof, wherein R1, R2 and R5 are each independently selected from H and hydrocarbon moieties, which hydrocarbon moieties optionally comprise one or more heteroatoms, and which hydrocarbons optionally comprise substituents, or when the compound according to formula (IX) is a salt, R1 and/or R2 may be a cation, R3, and R4 each independently selected from hydrocarbon moieties, which hydrocarbon moieties optionally comprise one or more heteroatoms, and which hydrocarbons optionally comprise substituents, and wherein any two of R1, R2, R3, R4 and R5 are optionally linked together to form a ring structure. The invention further relates to the preparation of such a compound and to the use of such a compound for preparing a pharmaceutical compound, an agrochemical compound, an intermediate for a pharmaceutical compound or an intermediate for an agrochemical compound.
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(2009/03/07)
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- ALPHA-SUBSTITUTED α,β-UNSATURATED E- OR Z-ALDEHYDES, USE THEREOF, AND PROCESSES FOR THEIR PREPARATION α,β
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This invention relates to novel alpha-substituted α,β-unsaturated E- or Z-aldehydes, or isomer mixture thereof, of the formula (I) in which R1 and R2 may be identical or different and are each H or a hydrocarbon, in which the hydrocarbon may have one or more heteroatoms and R3 and R4 may be identical or different and are each a hydrocarbon, in which the hydrocarbon may have one or more heteroatoms, and R5 may be identical or different and is H or a hydrocarbon, in which the hydrocarbon may have one or more heteroatoms, to the use thereof, and to processes for their preparation. The invention further relates to the preparation of further intermediates for pharmaceuticals and to the preparation of the pharmaceuticals.
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(2009/03/07)
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- Photochemical cleavage reactions of 8-quinolinyl sulfonates in aqueous solution
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Photochemical cleavage reactions of 8-quinolinyl benzenesulfonate derivatives and related sulfonates in aqueous solutions are reported. The 8-quinolinyl benzenesulfonates undergo photolysis upon photoirradiation at 300-330 nm to give the corresponding 8-quinolinols and benzenesulfonic acids with the production of only negligible amounts of byproducts. The effects of substituent groups of the 8-quinolinyl moiety and the benzene ring on the photolysis reactions were examined. Based on steady-state mechanistic studies using a triplet sensitizer, a triplet quencher, and electron donors, it was suggested that the photolysis proceeds mainly via the homolytic cleavage of S-O bonds in the excited triplet state.
- Kageyama, Yoshiyuki,Ohshima, Ryosuke,Sakurama, Kazusa,Fujiwara, Yoshihisa,Tanimoto, Yoshifumi,Yamada, Yasuyuki,Aoki, Shin
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experimental part
p. 1257 - 1266
(2010/05/02)
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- Removal of alkyl alkanesulfonate esters from alkanesulfonic acids and other organic media
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Methods of removing alkyl alkanesulfonate esters from aqueous or anhydrous compositions are provided. The invention provides methods for the conversion of alkyl alkanesulfonate esters of the formula RSO3R′ to the corresponding acids of the formula RSO3H. The alkyl alkanesulfonate esters are present in an organic medium, which may contain significant amounts of water or which may be anhydrous or substantially anhydrous. In some embodiments, the invention provides methods for purifying aqueous or anhydrous alkanesulfonic acids by removing alkyl alkanesulfonate esters.
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Page/Page column 6; 7
(2008/06/13)
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- Kinetics of radical heterolysis reactions forming alkene radical cations
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Rate constants for heterolytic fragmentation of β-(ester)alkyl radicals were determined by a combination of direct laser flash photolysis studies and indirect kinetic studies. The 1,1-dimethyl-2-mesyloxyhexyl radical (4a) fragments in acetonitrile at ambient temperature with a rate constant of khet > 5 × 109 s-1 to give the radical cation from 2-methyl-2-heptene (6), which reacts with acetonitrile with a pseudo-first-order rate constant of k = 1 × 106 s-1 and is trapped by methanol in acetonitrile in a reversible reaction. The 1,1-dimethyl-2-(diphenylphosphatoxy)hexyl radical (4b) heterolyzes in acetonitrile to give radical cation 6 in an ion pair with a rate constant of khet = 4 × 106 s-1, and the ion pair collapses with a rate constant of k ≤ 1 ± 109 s -1. Rate constants for heterolysis of the 1,1-dimethyl-2-(2,2- diphenylcyclopropyl)-2-(diphenylphosphatoxy)ethyl radical (5a) and the 1,1-dimethyl-2-(2,2-diphenylcyclopropyl)-2-(trifluoroacetoxy)ethyl radical (5b) were measured in various solvents, and an Arrhenius function for reaction of 5a in THF was determined (log k = 11.16-5.39/2.3RT in kcal/mol). The cyclopropyl reporter group imparts a 35-fold acceleration in the rate of heterolysis of 5a in comparison to 4b. The combined results were used to generate a predictive scale for heterolysis reactions of alkyl radicals containing β-mesyloxy, β-diphenylphosphatoxy, and β-trifluoroacetoxy groups as a function of solvent polarity as determined on the ET(30) solvent polarity scale.
- Horner, John H.,Bagnol, Laurent,Newcomb, Martin
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p. 14979 - 14987
(2007/10/03)
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- Characterization of species present in aqueous solutions of [hydroxy(mesyloxy)iodo]benzene and [hydroxy(tosyloxy)iodo]benzene
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Upon solution in water, both [hydroxy(mesyloxy)iodo]benzene and [hydroxy(tosyloxy)iodo]benzene undergo complete ionization to give the hydroxy(phenyl)iodonium ion (PhI+OH) and the corresponding sulfonate ion (RSO2O-) as fully solvated species, i.e., 'free' ions. The phenyliodonium solution species do not form ion pairs with the organosulfonate ions. The hydroxy(phenyl)iodonium ion is presumed to be ligated with at least one water molecule at an apical site of the iodine(m) atom originally occupied by the sulfonate ion. In view of the relative basicities of HO- and H2O, the hydroxy ligand of the [hydroxy(aquo)iodo]benzene ion (PhI+(OH2)OH) is expected to be strongly bound and the water ligand is expected to be weakly bound to the iodine(m) center. This species has a pK(A) at (4.30 ± 0.05). PhI+(OH2)OH and its conjugate base are present in equilibrium with the [hydroxy(auqo)]-μ-oxodiphenyldiiodine cation (Ph(HO)I-O-I+(OH2)Ph). This μ-oxo dimer is present at significant levels even in relatively dilute solutions as the combination equilibrium constant is (540 ± 50). This dimer can be protonated, and the pK(A) of the conjugate acid is ~2.5. The equilibrium constant for dimerization of [oxo(aquo)iodo]benzene (PhI+(OH2)O-), the most important monomer in acidic solutions, is ~8.6.
- Richter, Helen Wilkinson,Cherry, Brian R.,Zook, Teresa D.,Koser, Gerald F.
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p. 9614 - 9623
(2007/10/03)
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- Alkyl β-Oxoalkanesulfonates. I. Synthesis and Structure
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The esters of β-oxoalkanesulfonic acids were shown by UV and 1H NMR spectroscopy to exist only in keto-form unlike b-oxocarboxylic acids. However, the possibility of existence of the enol form is manifested in the reaction of the ester of benzoylmethanesulfonic acid with diazomethane leading to the formation of O-methyl ester. In alkaline solutions of β-oxosulfoesters a reversible enolization is observed, and their salts have the enolate structure. The capacity to such enolization is retained also in the salts of β-oxoalkanesulfonic acids though it requires more rigid conditions. In an alkaline medium the esters suffer "acidic" splitting on storage.
- Efimova,Lipina,Berkova,Pozdnyakov
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p. 1424 - 1428
(2007/10/03)
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- Relative Reactivities in Aminolysis Reactions of Alkyl Alkenesulfonates
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It is found that N-methylbutylamine is ten times more selective than N-methylaniline for the reaction at a methyl group than at a higher alkyl group, and that the greater reactivity of N-methylbutylamine than N-methylaniline is due to differences in entropy of activation rather than differences in activation energy.
- Roberts, David W.,Ward, Robert S.,Hughes, Paul J.
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- Mechanisms of Hydrolysis of (Trimethylsilyl)methanesulfonyl Chloride. Sulfene-Enamine Reactions in Water
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Kinetic, product analysis, and deuteration experiments are consistent with the following mechanisms of hydrolysis of (trimethylsilyl)methanesulfonyl chloride (1) (in 0.01 M KCl at 1 deg C): (a) pH /= 10.0, attack of hydroxide anion (i) at silicon to yield sulfene (5) and (ii) at an α-hydrogen to form (trimethylsilyl)sulfene (4), in each case followed by trapping of the sulfene to give either methanesulfonate (3) or (trimethylsilyl)methanesulfonate (6) salts.Aqueous potassium fluoride catalyzes the hydrolysis of 1 with formation of the methanesulfonate 3, evidently by way of silicophilic attack of fluoride anion on 1 with formation of sulfene (5).Reaction of 1 with an enamine 7 in water (at pH 8 or 9), with or without fluoride, gives two characteristic sulfene-enamine products, (i) the four-membered cycloadduct 8 and (ii) the methylsulfonyl aldehyde 9.The same or related products are also obtained from methanesulfonyl, 2-propanesulfonyl, and phenylmethanesulfonyl chlorides and enamines in water (at pH 9).Hydrolysis of 1 is also catalyzed by aniline or triethylamine evidently giving 5.
- King, James F.,Lam, Joe Y. L.
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p. 3429 - 3434
(2007/10/02)
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- Mechanism and Anion Activation in Solid-Liquid Phase-transfer Reactions Catalysed by Cyclophosphazenic Polypodands. Comparison with Cyclic Analogue Crown Ethers
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A kinetic study of the nucleophilic substitution of the methanesulfonic group by anions (Cl-, Br-, I-, SCN-, C6H5O-, C6H5CH2COO-) catalysed by cyclophosphazenic polypodands has been performed under solid-liquid phase-transfer conditions.The results obtained show that the mechanism of PTC previously found for cyclic ligands (crown ethers, cryptands) also operates in the case of these open-chain ligands: the attack by the anionic nucleophile on the substrate occurs in the organic phase and is rate determining of the overall process.The nucleophilicity scales found (I- > C6H5O- ca.SCN- > C6H5CH2COO-; I- > Br- > Cl-) as well as the anion activation are comparable with those found for cyclic crown ethers.This indicates that the anionic reactive species involved are similar in the complexes of both ligands.
- Landini, Dario,Maia, Angelamaria,Podda, Gianni,Secci, Daniela,Yan, Yong Ming
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p. 1721 - 1724
(2007/10/02)
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- Sulfonyl esters. 3. The formation of sulfone-sulfonates in the reactions of aryl methanesulfonates with sodium borohydride
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Sodium hydride reductions of aryl methanesulfonates afford dimeric sulfone-sulfonate esters as well as products arising from SO bond rupture.SO bond rupture becomes more competitive as the LUMO energy of the sulfonate ester declines.Exploration of the chemistry of a sulfone-sulfonate ester revealed a complex novel reaction that resulted in the formation of, inter alia, a dichloromethanesulfonate ester and a trichloromethanesulfonate aster.The first succesful approaches to the synthesis of the heretofore unknown trichloromethanesulfonates and dichloromethanesulfonates are reported.Key words: sodium hydride reductions, sulfenes, sulfone-sulfonate esters.
- Baum, James Clayton,Durkin, Kathleen Anne,Precedo, Laura,O'Blenes, Stacy Brian,Goehl, John Edward,et al.
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p. 2127 - 2135
(2007/10/02)
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- Rearrangement of Substituted Bicyclohex-2-yl Mesylates Under Solvolytic Conditions
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When heated in formic acid, methyl 2-mesyloxybicyclohexane-2-carboxylate (3) ionizes significantly faster than expected and yields the rearranged isomer (6) essentially quantitatively.The latter, on the other hand, solvolyses at a much reduced rate.These data are interpreted as evidnce for the presence in the ester of a favourable mesomeric interaction which largely offsets an otherwise destabillizing inductive effect when the ester is attached to a carbocationic centre.The corresponding cyano mesylates (8) and (29) were found to behave in an analogous manner when exposed to the solvolytic conditions.Heating the related acid mesylate (25) in an aqueous medium leads to the 1,2 hydroxy acid (24), whereas its sodium salt (26) is considerably more reactive and gives the 2,2-hydroxy acid (11).These observations are rationalized on the basis of the greatly enhanced ability of the COO- group relative to a COOH to stabilize an adjacent positively charged centre.The methyl substituent is also found to exert a profound effect on the nature of the solvolysis products, in hot formic acid, for example, 1-methylbicyclohex-2-yl mesylate (31) produces the formate (32) in which the substitution pattern is retained.Under milder conditions, however, the ester (31) solvolyses with rearrangement to give the 2,2-formate (33).
- Della, Ernest W.,Elsey, Gordon M.,Skouroumounis, George
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p. 1231 - 1244
(2007/10/02)
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- Chiral phenylether compound
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A chiral phenylether compound having the formula STR1 wherein X is a halogen atom; m is an integer from 3 to 5, n is an integer from 3 to 12 and * designates an asymmetric carbon is disclosed. The chiral phenylether compounds are useful to prepare chiral smectic phase pyrimidine phenylether liquid crystal compounds of the formula. STR2 The reaction is carried by reacting (I) with butylithium, dissolving in ether and reacting with a 1-bromoalkane to yield (IV). Compounds (IV) are particularly well suited to broaden the useful temperature range of ferroelectric liquid crystal materials.
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- Micellar Effects upon Substitutions by Nucleophilic Anions
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Micellar effects upon of OH- with p-nitrophenyl diphenyl phosphate or 2,4-dinitro-1-chloronaphthalene have been examined with cetyltrimethylammonium surfactants, (CTAX, X=Cl, Br, (SO4)1/2).Demethylations of methyl benzene- or naphthalene-2-sulfonate by halide ion have been examined. in micelles of CTACl, CTABr, CTA(SO4)1/2, or cetyltrimethylammonium mesylate (CTAOMs) and for demethylation by OH- or SO32- in CTA(SO4)1/2 or CTAOMs.The rate enhancements have been treated in terms of concentrations of the substrates and the nucleophilic anion at the micellar surface.The anion concentrations depended upon nonspecific Coulombic and specific interactions that were calculated by solving the Poisson-Boltzmann equation.The same structural parameters were used in fitting data for reactions with Cl- or Br- as nucleophiles and for systems with Cl- or Br- as inert anions that were competing with OH- or SO32-.The treatment is applicable to mixtures of database to mixtures of dilute mono- and dianions.
- Bunton, Clifford A.,Moffat, John R.
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p. 2896 - 2902
(2007/10/02)
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- Group Transfers III. Consequences of the Application of the Marcus Equation
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The rates of many group transfers are well described by the Marcus equation.Alkyl transfers in the solvent sulfolane, the formal transfers of R+ from one nucleophile to another, fit almost within experimental error.In these fairly slow reactions the Marcus quadratic term is negligible.Neglect of this term leads to absence of Reactivity Selectivity principle correlations.It leads to a scale of nucleophilicities and one of methylating power.In contrast, many nonalkyl transfers have much lower intrinsic barriers, and neglect of the quadratic term is unjustifiable.For alkyl transfers there is no general correlation between rate and equilibrium constants.When closely related series, such as a Hammett variation in the leaving group or nucleophile are studied, there is generally a rate-equilibrium LFER.From the slope of this rate-equilibrium LFER, the charge, δ, on the transferring group is calculated.The variation in this charge, which is structurally plausible, gives a new perspective on the rates of SN2 reactions, including benzylic, and α-halocarbonyl systems.
- Lewis, Edward S.
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p. 259 - 262
(2007/10/02)
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- Hydrolysis of Di- and Trimesylhydroxylamines and their Methylated Derivatives
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The mesylhydroxylamines (CH3SO2)2NOH, (CH3SO2)2NOCH3, CH3SO2N(H)OSO2CH3, CH3SO2N(CH3)OSO2CH3 (1-4) and (CH3SO2)2NOSO2CH3 (5) were treated with basic, neutral, and acidic aqueous solutions.The reaction products were identified.Possible decomposition mechanisms were discussed.
- Brink, Klaus,Mattes, Rainer
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p. 351 - 354
(2007/10/02)
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- An Assessment of the Causes of the "Cesium Effect"
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Cesium alkanoates (chiefly the propionate) have been investigated for their solubility, nucleophilic, reactivity and degree of ion pairing in dimethylformamide (DMF) and, in some cases, dimethyl sulfoxide (DMSO) solutions. 133Cs NMR has been used to establish the degree of ion pairing.From the data obtained it is concluded that the cesium ion is virtually completely solvated and that the carboxylates are essentially free and highly reactive.The consequences of this effect on macrocyclization by means of nucleophilic substitution are discussed.
- Dijkstra, Gerard,Kruizinga, Wim H.,Kellogg, Richard M.
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p. 4230 - 4234
(2007/10/02)
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- Micellar Effects on the Reaction of (Arylsulfonyl)alkyl Arenesulfonates with Hydroxide Ion. 2. The Absence of Substrate Orientational Effects in a Series of Sulfonates of Different Hydrophobicities
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Second-order rate constants for nucleophilic attack of hydroxide ion at the sulfonate sulfur atom of a series of sulfonates R1SO2CH2OSO2R2 (1a-g) in the presence of CTAB micelles (at 50 deg C) have been analyzed in terms of the pseudophase ion-exchange (PPIE) model.It is shown that the catalysis by the micelles is caused by the increased reactant concentrations in the micellar reaction volume.Large variations in the hydrophobicities of the substituents R1 and R2 (alkylaryl, alkyl) had only a minor influence on the rate constant for reaction in the micellar pseudophase (km).The same conclusion holds if the rate constants km are corrected for the different propensities of the sulfonates to respond to changes in the polarity of the reaction medium as expressed in the dielectric constant.Therefore there is no evidence that the depth of penetration and/or the orientation of the sulfonates 1a-g bound to the cetyltrimethylammonium bromide micelles is significantly affected by the hydrophobicities of R1 and R2.These findings are reconcilable with recent views cincerning the morphology of micelles.
- Witte, Frank M.,Engberts, Jan B. F. N.
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p. 4130 - 4134
(2007/10/02)
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- Alkylaminodesoxy-1.4;3.6-dianhydrohexitol nitrates substituted by purine bases and pharmaceutical compositions
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Alkylaminodesoxy-1.4;3.6-dianhydrohexitol nitrates substituted by purine bases of the general formula I, STR1 wherein R1 signifies a hydrogen atom or a lower alkyl group with 1 to 4 C-atoms, X a straight-chained or branched alkyl or hydroxyalkyl group with 1 to 7 C-atoms, Y a 1,3-dialkylxanthin-7-yl or a 3,7-dialkylxanthin-1-yl group, each with straight or branched-chained alkyl groups with 1 to 5 C-atoms, or an adenin-9-yl group, as well as their physiologically acceptable acid-addition salts. Process for the preparation of said compounds and pharmaceutical compositions containing said compounds.
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- Optionally N-substituted aminodesoxy-1.4;3.6-dianhydrohexitol derivatives
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Aminodesoxy-1.4;3.6-dianhydrohexitol derivatives of the general formula I, STR1 wherein R1 and R2, in each case independently of one another, signifies a hydrogen atom or a lower alkyl group with 1 to 4 C-atoms or wherein R1 signifies a hydrogen atom and R2 an adamant(1)yl radical or wherein R1 and R2, together with the nitrogen atom to which they are attached, (a) signify the residue of a cyclic, non-aromatic secondary amine possibly containing a further hetero atom or (b) the aden(9)yl radical possibly mono- or disubstituted on the 6-amino group or (c) the 6-alkylmercaptopurin(9)yl radical or (d) the theophyllin(7)yl radical or (e) the 6-chloropurin-9-yl radical or wherein R1 signifies a hydrogen atom or a lower alkyl group with 1 to 4 C-atoms and R2 an ω-theophyllin(7)ylalkyl radical or an ω-theobromin-1-ylalkyl radical or an ω-(N,N'-di-lower alkyl-substituted xanthin-N"-yl)alkyl radical, whereby "lower alkyl" signifies an alkyl group with 1 to 5 C-atoms, or an ω-adenin-9-ylalkyl radical, whereby the alkyl radical has 2 to 7 C-atoms and can be straight-chained or branched, and wherein R3 signifies a hydrogen atom, a methanesulphonyl or toluenesulphonyl group, as well as their acid-addition salts. Processes for the preparation of said compounds and use of said compounds as reactive intermediate products for the preparation of the corresponding pharmacologically-effective amino-desoxy-1.4;3.6-dianhydrohexitol nitrates.
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- Aminodesoxy-1.4;3.6-dianhydrohexitol nitrates and pharmaceutical composition
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Aminodesoxy-1.4;3.6-dianhydrohexitol nitrates of the general formula I, STR1 wherein R1 and R2 possess the meanings given in claim 1, as well as their pharmacologically acceptable acid-addition salts; processes for the preparation of said compounds, and pharmaceutical compositions containing at least one of said compounds.
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- Nonhydrated Anion Transfer from the Aqueous to the Organic Phase: Enhancement of Nucleophilic Reactivity in Phase-Transfer Catalysis
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A systematic study of how the nature and concentration of the inorganic salt affect hydration and reactivity of anions transferred into the organic phase under conditions of phase-transfer catalysis (PTC) has been performed.The inorganic salt concentration in the aqueous phase up to saturated solution (= or > 6 M), does not affect the hydration and hence the reactivity of the anion in aliphatic nucleophilic substitutions.On the other hand, in concentrated aqueous alkaline solutions (50percent NaOH or 60percent KOH) unhydrated anions are transferred from the aqueous to the organic phase.The anionic reactivity thus becomes identical with that found under anhydrous homogeneous conditions, the rate enhancement being 13.0, 4.0, 2.6, and 1.4 times for Cl(1-), N3(1-), Br(1-), and I(1-), respectively.The same dehydrating effect was not observed with less concentrated alkaline solutions or with 50percent aqueous NaF.These data show the unique property of OH(1-) in producing conditions of virtually null water activity under PTC conditions.
- Landini, Dario,Maia, Angelamaria,Podda, Gianni
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p. 2264 - 2268
(2007/10/02)
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- Mesylhydroxylamines, V. Polysubstituted N-Mesylhydroxylamines
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The preparation and characterization of the following N-mesylhydroxylamines are reported: (CH3SO2)2NOSO2CH3 (1), (CH3SO2)2NOCH3 (2), CH3SO2N(CH3)OSO2CH3 (3), CH3SO2N(H)OCH3 (4), Na(1+)*CH3SO2NOCH3(1-)*1/2H2O (5), CH3SO2N(CH3)OCH3 (6). - Keywords: Methane Sulfonic Acid Derivatives, Hydroxylamines
- Boldhaus, Michael,Bliefert, Claus,Brink, Klaus,Mattes, Rainer
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p. 1673 - 1674
(2007/10/02)
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- Studies on Sulphochlorination of Paraffins. VIII. Studies on the Hydrolysis of Individual Alkane Sulphochlorides by Sodium Hydroxide
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The hydrolysis of individual C1-C5 alkane sulphochlorides by sodium hydroxide in dioxane/water (1:1) was kinetically studied at 25 deg C by means of stopped-flow technique, measuring the change of electric conductivity.The rate constants were influenced by steric hindrance, but in all cases were higher than the rate constant for alkaline hydrolysis of benzene sulphochloride, which cannot react according to the elimination-addition (sulphene) mechanism.The reaction enthalpy of the alkaline hydrolysis of four individual alkane sulphochlorides was determined by a simple calorimetric apparatus; the average value amounts to ΔRH = -239 kJ mol-1.
- Hampel, M.,Just, G.,Krebes, W.,Pritzkow, W.
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p. 987 - 990
(2007/10/02)
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- ALUMINIUMALKYLE MIT HETEROATOMEN. XI. UEBER DIE UMSETZUNG VON SCHWEFELTRIOXID MIT TRIS(SILYLALKYL)ALUMINIUM-VERBINDUNGEN ZU SILYLALKANSULFONATEN
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Treatment of sulphur trioxide with tris(silylalkyl)aluminium compounds followed by hydrolysis and extraction with ethyl alcohol is a new method for preparation of substituted sodium silylalkane sulphonates.Weak donor-acceptor complexes of the starting compounds react selectively with insertion at the aluminium-carbon bond without cleavage of the silicon-carbon bond.The structure of the silylalkane sulphonates is determined by 1H NMR and IR spectroscopy.
- Sonnek, Georg,Mueller, Gisela,Baumgarten, Karl-Guenther
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- Synthesis of S-Sulfonyl-Phosphinothioates and Phosphinodithioates, a Novel Organophosphorus-sulphur Structure
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Racemic and optically active S-sulphonylphosphinothioates R-SO2-S-P(O)ButPh and dithioates R-SO2-S-P(S)ButPh (R = Me, p-tolyl) have been prepared for the first time by the reaction of the corresponding acids ButPhP(S)SH(X = O,S) of their salts with sulphonylating reagents RSO2-Y (Y = Cl, O-SO2R, triazolide).
- Dabkowski, Wojciech,Lopusinski, Andrzej,Michalski, Jan,Radziejewski, Czeslaw
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p. 375 - 378
(2007/10/02)
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