- Development of selective colorimetric probes for hydrogen sulfide based on nucleophilic aromatic substitution
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Hydrogen sulfide is an important biological signaling molecule and an important environmental target for detection. A major challenge in developing H2S detection methods is separating the often similar reactivity of thiols and other nucleophiles from H2S. To address this need, the nucleophilic aromatic substitution (SNAr) reaction of H2S with electron-poor aromatic electrophiles was developed as a strategy to separate H2S and thiol reactivity. Treatment of aqueous solutions of nitrobenzofurazan (7-nitro-1,2,3-benzoxadiazole, NBD) thioethers with H 2S resulted in thiol extrusion and formation of nitrobenzofurazan thiol (λmax = 534 nm). This reactivity allows for unwanted thioether products to be converted to the desired nitrobenzofurazan thiol upon reaction with H2S. The scope of the reaction was investigated using a Hammett linear free energy relationship study, and the determined ρ = +0.34 is consistent with the proposed SN2Ar reaction mechanism. The efficacy of the developed probes was demonstrated in buffer and in serum with associated submicromolar detection limits as low as 190 nM (buffer) and 380 nM (serum). Furthermore, the sigmoidal response of nitrobenzofurazan electrophiles with H2S can be fit to accurately quantify H2S. The developed detection strategy offers a manifold for H2S detection that we foresee being applied in various future applications.
- Montoya, Leticia A.,Pearce, Taylor F.,Hansen, Ryan J.,Zakharov, Lev N.,Pluth, Michael D.
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p. 6550 - 6557
(2013/07/26)
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- Catalytic transfer hydrogenation of aryl sulfo compounds
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A new method to reduce aryl sulfo compounds via transfer hydrogenation was investigated, using Pd/C as a catalyst, and 2-propanol or formic acid as hydrogen sources. This new process is simple and clean.
- Chen, Xinzhi,Zhou, Shaodong,Qian, Chao
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experimental part
p. 179 - 185
(2012/05/21)
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- Solvent-free synthesis of thiophenol using uncatalyzed transfer hydrogenation
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Clean and sustainable transfer hydrogenation for aryl sulfonamides and sulfonyl chlorides is described. The protocol is chemoselective and uses neither catalyst nor solvent.
- Zhou, Shaodong,Qian, Chao,Chen, Xinzhi
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experimental part
p. 2432 - 2439
(2012/06/18)
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- Palladium catalyzed synthesis of aryl thiols: Sodium thiosulfate as a cheap and nontoxic mercapto surrogate
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A Pd-catalyzed coupling reaction of ArBr/ArCl/ArOTf with sodium thiosulfate takes place in presence of Cs2CO3 at 80 °C. The reaction mixture is directly treated with Zn/HCl to afford aryl thiols in good to excellent yields.
- Yi, Jun,Fu, Yao,Xiao, Bin,Cui, Wei-Chen,Guo, Qing-Xiang
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experimental part
p. 205 - 208
(2011/02/26)
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- A study of the kinetics of La3+-promoted methanolysis of S-aryl methylphosphonothioates: Possible methodology for decontamination of EA 2192, the toxic byproduct of VX hydrolysis
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The kinetics of the La3+-catalyzed methanolysis of a series of S-aryl methylphosphonothioates (4a-e, phenyl substituents = 3,5-dichloro, 4-chloro, 4-fluoro, 4-H, 4-methoxy) were studied at 25 °C with ss pH control. The reaction involves saturation binding of the anionic substrates to dimeric La3+/methoxide catalysts formulated as La2 3+(-OCH3)x, where x = 2-5 depending on the solution ss pH. Cleavage of the La3+-bound methylphosphonothioates is fast, ranging from 5 × 10-3 s -1 to 5.5 × 10-5 s-1 for substrates 4a-e at a ss pH of 8.4 and 1.6 × 10-1 s-1 to 4 × 10-3s-1 at a ss pH of 11.7. The rate accelerations for the methanolysis of substrates 4a-e, relative to their background methoxide-promoted reactions, average 7 × 1010 and 1.5 × 109, respectively, at sspH's of 8.4 and 11.7. The catalytic system is predicted to cleave EA 2192 (S-2(N,N-di-iso-propylaminoethyl) methylphosphonothioate), a toxic byproduct of the hydrolysis of VX, with a t1/2 between 4 and 8 min at a ss pH of 8.4, and 27 min at a ss pH of 11.7.
- Dhar, Basab B.,Edwards, David R.,Brown, R. Stan
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p. 3071 - 3077
(2011/05/09)
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- Copper-catalyzed coupling of thiourea with aryl iodides: The direct synthesis of aryl thiols
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A general, economical and efficient protocol for the direct copper-catalyzed coupling of thiourea with aryl iodides is developed and it will be potentially applied in large-scale industry as a preferred process.
- Qiao, Shu,Xie, Kun,Qi, Junsheng
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scheme or table
p. 1441 - 1443
(2011/01/04)
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- A general and efficient approach to aryl thiols: Cul-catalyzed coupling of aryl iodides with sulfur and subsequent reduction
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A Cul-catalyzed coupling reaction of aryl iodides and sulfur powder takes place in the presence of K2CO3 at 90 °C. The coupling mixture is directly treated with NaBH4 or triphenylphosphine to afford aryl thiols in good to
- Jiang, Yongwen,Qin, Yuxia,Xie, Siwei,Zhang, Xiaojing,Dong, Jinhua,Ma, Dawei
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supporting information; scheme or table
p. 5250 - 5253
(2009/12/28)
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- Catalytic decomposition of simulants for chemical warfare V agents: Highly efficient catalysis of the methanolysis of phosphonothioate esters
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(Chemical Equation Presented) As good as the original: Extremely effective methanolysis of phosphonothioates using metal-containing systems (e.g., 1) was achieved. The catalytic methanolysis of a SCH2CH2NEt 2 derivative, an analogue of the organophosphorus chemical warfare material VX, was predicted, and the catalyzed methanolysis of S-(3,5-dichlorophenyl) O-ethyl methylphosphonothioate was shown to involve a concerted displacement of the aryl thioate (transition state 2)
- Melnychuk, Stephanie A.,Neverov, Alexei A.,Brown, R. Stan
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p. 1767 - 1770
(2007/10/03)
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- Mechanistic studies of la3+- And Zn2+-catalyzed methanolysis of aryl phosphate and phosphorothioate triesters. Development of artificial phosphotriesterase systems
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The methanolyses of a series of O,O-diethyl O-aryl phosphates (2,5) and O,O-diethyl S-aryl phosphorothioates (6) promoted by methoxide and two metal ion systems, (La3+)2(-OCH3)2 and 4:Zn2+:-OCH3 (4 = 1,5,9- triazacyclododecane) has been studied in methanol at 25°C. Bronsted plots of the log k2 values vs. sspKa for the phenol leaving groups give βlg values of -0.70. -1.43 and -1.12 for the methanolysis of the phosphates and -0.63, -0.87 and -0.74 for the methanolysis of the phosphorothioates promoted by the methoxide, La 3+ and Zn2+ systems respectively. The kinetic data for the metal-catalyzed reactions are analyzed in terms of a common mechanism where there is extensive cleavage of the P-XAr bond in the rate-limiting transition state. The relevance of these findings to the mechanism of action of the phosphotriesterase enzyme is discussed. The Royal Society of Chemistry 2005.
- Liu, Tony,Neverov, Alexei A.,Tsang, Josephine S.W.,Brown, R. Stan
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p. 1525 - 1533
(2007/10/03)
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- An efficient synthetic route to aryl thiocyanates from arenesulfinates
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An efficient procedure for the conversion ot the inexpensive and readily available arenesulfinate (sodium) salts in three steps into the corresponding aryl thiocyanates is described. Overall yields are high, and the presence of both electron-with drawing and electron-donating substituents is well tolerated.
- Still,Watson
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p. 1355 - 1359
(2007/10/03)
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- One-step arylthiolation of aromatic compounds by disulfide radical cations generated from oxidation of diaryl disulfides with aluminium chloride
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Reactions of di(phenyl and 4-tolyl) disulfides 1a and 1b with PhX 3a-e (X = H, Me, Et, Ph and Cl) in the presence of AlCl3 at 25°C give diaryl sulfides 4-6 by aromatic arylthiolation via the disulfide radical cations 2, along with thiophenols 7 formed in the incomplete reactions. Competitive intramolecular reactions of 2a also yield diphenyl sulfide 4a or/and thianthrene 8. However, the reactions of bis(4-chlorophenyl and 4-fluorophenyl) disulfides 1c and 1d selectively lead to the aromatic arylthiolation in high yields. The Hammett ρ = -8.8 at 25°C for the phenylthiolation in the reactions of 1a is more negative than that (ρ = -7.0 at -30°C) using SbCl5 instead of AlCl3, and the value ρ = -8.0 for the arylthiolation using 1d is less negative than that using 1a. These and the other mechanistic aspects support the arylthiolations via 2.
- Takeuchi, Hiroshi,Suga, Keisuke
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p. 1803 - 1808
(2007/10/03)
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- Direct gas-phase synthesis of 4-fluorothiophenol and bis(4-fluorophenyl) sulfide
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The gas-phase reaction of 4-chlorofluorobenzene with a 4-fold excess of hydrogen sulfide at 700°C allows simultaneous one-stage synthesis of 4-fluothiorophenol and bis(4-fluorophenyl) sulfide. The low yield of the reaction products is compensated for by the facility of their synthesis and isolation.
- Deryagina,Sukhomazova,Levanova,Papernaya,Dolenko
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- Oxidative cleavage of S-Arylmercaptoacetic acids by pyridinium chlorochromate: Kinetic and correlation analysis
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Kinetics of oxidation of 24 S-Arylmercaptoacetic acids (SAMA) by pyridinium chlorochromate (PCC) have been studied in acid medium. The product of oxidation is the corresponding thiophenol. The rate data of meta- and para-substituted acids have been correlated well with σI, σ°R values and the meta-compounds correlate well with F,R values. The reaction constants are negative and of smaller magnitudes. Further, the ortho-substituted acids show a good correlation with triparametric equation involving Taft's σI and σ°R and charton's steric parameter v. There is no considerable steric contribution to the total orthosubstituent effect. Based on these observations, the mechanism involving the formation of protonated arylsulfinylacetic acid intermediate, followed by an intramolecular rearrangement leading to the product thiophenol has been proposed.
- Kabilan,Girija,Rajagopal
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p. 683 - 688
(2007/10/03)
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- Process for the preparation of 4-fluorothiophenol
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4-Fluorothiophenol is obtained in outstanding purifies and yields if 4-fluorobenzenesulphonyl chloride is reacted with sodium hydrogen sulphite solution to give a solution of sodium 4-fluorobenzenesulphinate, this solution is reduced with sulphur dioxide to give 4,4'-difluorodiphenyl disulphide and finally this is reacted with sodium borohydride in a water-miscible inert organic solvent to give 4-fluorothiophenol (sodium salt). Free 4-fluorothiophenol can be isolated from the sodium salt solution by acidification.
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- Certain isoquinoline derivatives having anti-tumor properties
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Compounds are described of general formula (I) STR1 and salts and solvates thereof, including physiologically acceptable salts and solvates thereof, in which: Z represents either Het, STR2 Het represents an optionally substituted bicyclic or tricyclic ring selected from acricine isoquinolin-1-yl, isoquinolin-3-yl, The novel compounds of formula (I) can sensitize multi-drug resistant cancer cells to chemotherapeutic agents and may be formulated for use in therapy, particularly to improve or increase the efficacy of an anti-tumour drug.
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- Oxidative Cleavage of S-Arylmercaptoacetic Acids by Sodium Perborate: Kinetic and Correlation Study
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Kinetics of oxidation of twenty six S-arylmercaptoacetic acids (SAMA) (I) by sodium perborate (PB) have been studied in acid medium.The product of oxidation is the corresponding thiophenol.The rate data of meta- and para-substituted acids have been correlated with DSP equations.While the para-compounds correlate well with ?I and ?0R values, the meta-compounds correlate well with ?I and ?-R values.The reaction constants are negative and of smaller magnitudes.Further, the ortho-substituted acids show a good correlation with a triparametric equation involving Taft's ?I and ?0R and Charton's steric parameter ν.There is a considerable steric contribution to the total ortho-substituent effect.Based on these observations, mechanism involving the formation of protonated arylsulfinylacetic acid intermediate, followed by an intramolecular rearrangement leading to the product thiophenol has been proposed.
- Kabilan, S.,Pandiarajan, K.,Krishnasamy, K.,Sankar, P.
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p. 443 - 452
(2007/10/02)
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- Triphenylphosphine Decomposition of Sulfenyl Thiocarbonates
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Several sulfenyl thiocarbonates (RSSCO2CH3) have been decomposed with triphenylphosphine.In the case of R = alkyl, desulfurization takes place to give the S-alkyl thiocarbonate while in the case of R = aryl, a phosphonium salt is likely formed which on chromatographic workup on silica gel is converted to a thiol and triphenylphosphine oxide and sulfide.A mechanistic interpretation is offered.
- Harpp, David N.,Granata, Alessandro
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p. 271 - 273
(2007/10/02)
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- Cephalosporin displacement reaction
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The present invention is directed to a process for the displacement of the acetoxy group of a cephalosporanic acid by a sulfur nucleophile, in an organic solvent and under essentially anhydrous conditions.
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- Pesticidal compositions containing phosphoric esters and divalent sulphur compounds
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Pesticidal composition comprising: a pesticidal, phosphoric ester the molecule of which has at least one alkyl group of 1 to 3 carbon atoms, 0.05 to 10% of an agent stabilizing the said ester against decomposition by protonisation, together with adjuvants characterized in that the stabilizing agent comprises at least one sulphur compound containing per molecule at least one divalent sulphur atom of which one valence is bonded to an atom chosen from sulphur, carbon, nitrogen, hydrogen, and metals capable of giving a salt, the other valence being bonded to an atom chosen from hydrogen, the carbon atom already noted, a second carbon atom, the nitrogen atom already noted, a second nitrogen atom, the metal atom already noted in the case of a metal of valence greater than one, a second atom of metal and oxygen when the first valence is not attached to an atom of hydrogen, the proportion of sulphur calculated with reference to the weight of the sulphur compound being between 5 and 99%. Process for stabilizing a phosphoric ester of which the molecule possesses at least one alkyl group containing 1 to 3 carbon atoms characterized in that there is added to the phosphoric ester or to a mixture which contains it, 0.05 to 10% calculated on the weight of the phosphoric acid ester of an agent capable of stabilizing the said phosphoric ester against protonisation and comprising at least one sulphur compound such as that defined thereupon.
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