- Mononuclear versus dinuclear palladacycles derived from 1,3-bis(N,N-dimethylaminomethyl)benzene: Structures and catalytic activity
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Mononuclear and dinuclear palladacycles derived from 1,3-bis(N,N- dimethylaminomethyl)benzenes, [{Pd (Cl)}2,6-(Me2NCH2) 2C6H3] (1) and [1-{Pd(H2O)(Py)}-5- {Pd(OTf)(Py)-2,4-(Me2NCH2)2C6H 2]-(OTf) (2), were synthesized and their structures were fully characterized. Complex 1 is a pincer complex with η3-mer NCN phenyl backbone, complex 2 is a bispalladium(II) complex with 1,2- and 4,5- two C,N-ortho phenyl backbone. Whereas the pincer complex 1 acted as a poor catalyst on methanolysis of fenitrothion, complex 2 demonstrated high catalytic activity in the same reactions, but there is no synergetic effect between two palladium ions. The results clearly indicate that a dissociable co-ligand in the palladacycle compounds significantly promotes the catalytic methanolysis.
- Liu, Bian-Bian,Wang, Xue-Rui,Guo, Zhi-Fo,Lu, Zhong-Lin
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Read Online
- Reactions of Benzopentathiepin with Trialkyl Phosphites. A New Preparative Method for S-Aryl O,O'-Dialkyl Thiophosphates
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Benzopentathiepin readily reacted with trialkyl phosphites to give S--O,O'-dialkyl thiophosphates and/or O,O'-dialkyl S-(2-mercaptophenyl) thiophosphates.The selectivity for formation of these thiophosphates was dramatically affected by the reaction temperature and the solvent used.
- Sato, Ryu,Murata, Toshitaka,Chida, Shin-ichi,Ogawa, Satoshi
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Read Online
- SYNTHESIS OF THIOLATED OLIGONUCLEOTIDES WITHOUT A CAPPING STEP
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The invention herein describes a synthetic method for preparing thiolated oligonucleotides without needing a capping step, as the sulfurization agent caps the unreacted 5'-OH groups.
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Page/Page column 36
(2018/04/11)
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- 1,2,4-Dithiazole-5-ones and 5-thiones as efficient sulfurizing agents of phosphorus(iii) compounds - A kinetic comparative study
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The sulfurization efficiency of 25 3-substituted-1,2,4-dithiazole-5-ones and 5-thiones towards triphenyl phosphite in acetonitrile, DCM, THF and toluene at 25 °C was evaluated. All the 1,2,4-dithiazoles are much better sulfurizing reagents than commercially available agents (PADS, TETD, Beaucage's reagent). The most efficient sulfurizing agents in all solvents are 3-phenoxy (4), 3-phenylthio (5) and 3-ethoxy-1,2,4-dithiazole-5-one (1) whose reactivity is at least two orders of magnitude higher than that of other 1,2,4-dithiazoles. Contrary to a previous report, the sulfurization with 1 does not yield carbonylsulfide and ethyl cyanate as the additional reaction products but unstable ethoxythiocarbonyl isocyanate which has been trapped with 4-methoxyaniline. Similar trapping experiments have proven that the site of attack is at the sulfur adjacent to the CO group for compounds 4 and 5. The reaction pathway involves rate-limiting initial nucleophilic attack of the phosphorus at sulfur followed by decomposition of the phosphonium intermediate to the corresponding phosphorothioate and isocyanate/isothiocyanate species. The existence of the phosphonium intermediate during sulfurization of triphenyl phosphine with 3-phenyl-1,2,4-dithiazole-5-thione (7a) was proven using kinetic studies. From the Hammett and Bronsted correlations and from other kinetic measurements it was concluded that the transition-state structure is almost apolar for the most reactive 1,2,4-dithiazoles whereas a polar structure resembling a zwitter-ionic intermediate may be more appropriate for the least reactive 1,2,4-dithiazoles. The extent of P-S bond formation and S-S bond cleavage is very similar in all reaction series but it gradually decreases with the reactivity of the 1,2,4-dithiazole derivatives.
- Ponomarov, Oleksandr,Laws, Andrew P.,Hanusek, Ji?í
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supporting information
p. 8868 - 8876
(2013/01/15)
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- Mechanistic and computational study of a palladacycle-catalyzed decomposition of a series of neutral phosphorothioate triesters in methanol
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The methanolytic cleavage of a series of O,O-dimethyl O-aryl phosphorothioates (1a-g) catalyzed by a C,N-palladacycle, (2-[N,N- dimethylamino(methyl)phenyl]-C1,N)(pyridine) palladium(II) triflate (3), at 25 °C and sspH 11.7 in methanol is reported, along with data for the methanolytic cleavage of 1a-g. The methoxide reaction gives a linear log k2-OMe vs sspKa (phenol leaving group) Bronsted plot having a gradient of βlg = -0.47 ± 0.03, suggesting about 34% cleavage of the P-OAr bond in the transition state. On the other hand, the 3-catalyzed cleavage of 1 gives a Bronsted plot with a downward break at sspKa (phenol) ~ 13, signifying a change in the rate-limiting step in the catalyzed reaction, with the two wings having βlg values of 0.0 ± 0.03 and -1.93 ± 0.06. The rate-limiting step for good substrates with low leaving group sspKa values is proposed to be substrate/pyridine exchange on the palladacycle, while for substrates with poor leaving groups, the rate-limiting step is a chemical one with extensive cleavage of the P-OAr bond. DFT calculations support this process and also identify two intermediates, namely, one where substrate/pyridine interchange has occurred to give the palladacycle coordinated to substrate through the S - P linkage and to methoxide (6) and another where intramolecular methoxide attack has occurred on the P - S unit to give a five-coordinate phosphorane (7) doubly coordinated to Pd via the S- and through a bridging methoxide linked to P and Pd. Attempts to identify the existence of the phosphorane by 31P NMR in a d4-methanol solution containing 10 mM each of 3, trimethyl phosphorothioate (a very slow cleaving substrate), and methoxide proved unsuccessful, instead showing that the phosphorothioate was slowly converted to trimethyl phosphate, with the palladacycle decomposing to Pd0 and free pyridine. These results provide the first reported example where a palladacycle-promoted solvolysis reaction exhibits a break in the Bronsted plot signifying at least one intermediate, while the DFT calculations provide further insight into a more complex mechanism involving two intermediates.
- Liu, C. Tony,Maxwell, Christopher I.,Edwards, David R.,Neverov, Alexei A.,Mosey, Nicholas J.,Brown, R. Stan
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experimental part
p. 16599 - 16609
(2011/02/23)
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- An ortho-palladated dimethylbenzylamine complex as a highly efficient turnover catalyst for the decomposition of P=S insecticides. Mechanistic studies of the methanolysis of some P=S-containing phosphorothioate triesters
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An ortho-palladated complex Pd(dmba)(py)(OTf) (9), or Pd(N,N- dimethylbenzylamine)(pyridine)-(trifluoromethanesulfonate), was synthesized and its solution properties in methanol studied as a function of s spH. In neutral solution the triflate dissociates from the complex to give a dominant form Pd(dmba)(py)(HOCH3), and in acid the pyridine dissociates to give Pyr-H+ and Pd(dmba)(HOCH3)(HOCH 3). Under basic conditions, Pd(dmba)(py)(HOCH3) ionizes to give Pd(dmba)(py)(-OCH3) from which the pyridine can dissociate to yield a mixture of a bis-methoxy-bridged dimer (Pd(dmba)( -OCH3))2 (15-dimer), and its monomer Pd(dmba)(HOCH3)-(-OCH3). Kinetic studies under buffered conditions reveal that 9 is an effective catalyst for the methanolysis of fenitrothion and other P=S pesticides. The active form of the catalyst is a basic one having one associated methoxide generated with an apparent sspKa of 10.8. Analysis of the change in the UV/vis spectrum as a function of sspH generates a spectrophotometric ssKa of 10.8 ±0.1. This catalytic system is shown to promote the methanolysis of fenitrothion (3), diazinon (4), quinalphos (5), coumaphos (10) and dichlofenthion (11) at 0.05 mol dm-3 triethyl amine buffer, sspH 10.8, 25°C, under turnover conditions where the [phosphorothioate]/[9] ratio is 48.6, 13.4, 13.4, 18.6, and 48.6 respectively. In all cases, the products were derived from displacement of the leaving group by methoxide, the second-order turnover rate constants being 36.9, 0.45, 0.12, > 146.7 and 44.3 dm 3 mol-1 s-1 respectively. An associative mechanism for the catalyzed methanolysis of the P=S pesticides is proposed where a transiently coordinated S=P substrate is intramolecularly attacked by the PdII-coordinated methoxide. The Royal Society of Chemistry 2005.
- Lu, Zhong-Lin,Neverov, Alexei A.,Brown, R. Stan
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p. 3379 - 3387
(2007/10/03)
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- Method of decomposing organophosphorus compounds
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Methods and kits for decomposing organophosphorus compounds in non-aqueous media at ambient conditions are described. Insecticides, pesticides, and chemical warfare agents can be quickly decomposed to non-toxic products. The method comprises combining the organophosphorus compound with a non-aqueous solution, preferably an alcohol, comprising metal ions and at least a trace amount of alkoxide ions. In a first preferred embodiment, the metal ion is a lanthanum ion. In a second preferred embodiment, the metal ion is a transition metal.
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- Cu(II)-Mediated decomposition of phosphorothionate P=S pesticides. Billion-fold acceleration of the methanolysis of fenitrothion promoted by a simple Cu(II)-ligand system
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The kinetics of methanolysis of the title compound (3) were studied in the presence of Cu2+, introduced as Cu(OTf)2, in the presence of 0.5-1.0 eq. of methoxide and in the presence of 1.0 eq. of a ligand such as bipyridyl (5), phenanthroline (6) or 1,5,9-triazacyclododecane (4). In all cases the active species involve Cu2+(-OCH3). In the case of added strongbinding ligands 5 or 6, a plot of the observed rate constant for methanolysis of 3 vs. [Cu2+]total gives a curved line modelled by a process having a [Cu2+]1/2 dependence consistent with an active monomeric species in equilibrium with an inactive dirtier i.e. {LCu2+(-OCH3)} 2→2LCu2+(-OCH3). In the case of the added strong binding ligand 4, the plot of the observed rate constant for methanolysis of 3 vs. [Cu2+]total gives a straight line consistent with the catalytically active species being 4Cu 2+(OCH3) which shows no propensity to form inactive dimers. Turnover experiments where the [3] > [Cu2+] total indicate that the systems are truly catalytic. In the optimum case a catalytic system comprising 1 mM of the complex 4Cu2+( -OCH3) catalyzes the methanolysis of 3 with a t 1/2 of ~58 s accounting for a 1.7 × 109-fold acceleration relative to the background reaction at near neutral sspH (8.75).
- Neverov, Alexei A.,Brown, R. Stan
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p. 2245 - 2248
(2007/10/03)
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- Nucleoside H-Phosphonates. 13. Studies on 3H-1,2-Benzodithiol-3-one Derivatives as Sulfurizing Reagents for H-Phosphonate and H-Phosphonothioate Diesters
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Formation of O-oxidized products during sulfurization of H-phosphonothioate and H-phosphonate diesters with 3H-1,2-benzodithiol-3-one 1,1-dioxide (1) was found to be due to generation of the O-oxidizing agents, most likely 3H-2,1-benzoxathiol-3-one 1-oxide (4) and 3H-2,1-benzoxathiol-3-one (5), during the course of the reactions.Another source of the side products formation may be the disproportionation of 1 that occurs in the presence of triethylamine.To overcome these problems, a new sulfur-transferring reagent, 3H-1,2-benzodithiol-3-one (3), has been developed.Under aqueous reaction conditions, which are compartible with both solution and solid-phase synthesis of oligonucleotides, the reagent 3 furnished clean and fast conversion of H-phosphonothioate and H-phosphonate diesters into the corresponding phosphorodi- and phosphoromonothioates.
- Stawinski, Jacek,Thelin, Mats
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p. 5169 - 5175
(2007/10/02)
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- THIONO COMPOUNDS. 10. STRUCTURES AND REACTIONS OF INTERMEDIAATES FROM THE OXIDATION OF PHOSPHOROTHIOATES
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Intermediates from the oxidation of phosphorothioates, (RO)3PS, were studied previously at low temperature using 31P NMR, UV and Raman spectra.Now reported is further information about the structure of intermediates and about their reactions, both of which afford significant clues as to how phosphorothioates may produce adverse biological reactions after they have ben oxidized biologically.Mass spectra identified intermediates corresponding to (RO)3PSn with n up to 7 (although presence of some equivalent masses with two oxygens in place of a sulfur atom is possible).HPLC separated unstable intermediates for which UV and MS evidence again was consistent with the structure (RO)3PSn.That intermediates can react as nucleophiles is illustrated by reactions with Ellman's Reagent, which produced a maximum of thiolate ion at about the time 31P NMR and UV indicated a maximum of intermediates.A second illustration of nucleophilicity was reaction with N-ethylmaleimide (and other Michael acceptors), which led to thiiranes and thiirane 1-oxides.That the intermediates can react also as electrophiles is illustrated by reactions (followed by UV and 31P NMR) with trimethyl phosphite, hydroxyl ion, and water (perhaps to some extent); use of H2(18)O did not introduce (18)O into phosphate products, but exchange reactions with H2(18)O did indicate presence of oxygenated species among the intermadiates.Keywords: Ellman's Reagent; N-ethylmaleimide; 31P NMR spectra; Phosphorothioates; Thiiranes; UV spectra.
- Swinson, Joel,Field, Lamar,Heimer, Norman E.,Stone, Michael P.,Wazer, John R. Van
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- An efficient approach toward the synthesis of phosphorothioate diesters via the Schonberg reaction
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Easily accessible phenacetyl or benzoyl disulfide proved to be very conventional ragents for a rapid P-sulfurization of phosphite-triesters and H-phosphonate diesters, respectively.
- Kamer,Roelen,Van den Elst,Van der Marel,Van Boom
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p. 6757 - 6760
(2007/10/02)
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- Reaction of Carbodiimides with Phosphorothioic, Phosphorodithioic, and Phosphoroselenoic Acids: Products, Intermediates, and Steps
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The reaction of the title acids with dicyclohexylcarbodiimide (DDC) used in a 2:1 ratio was found to give a complex mixture of products consisting of thio(seleno)pyrophosphates, thiolo(selenolo)phosphates, thiono(selenono)phosphates, dicyclohexylthiourea (DCTU), and a polymeric alkyl metaphosphate.When both reaction components are mixed in a 1:1 ratio, N-phosphoryl-N,N'-dicyclohexylthio(seleno)ureas (B) were formed.The formation of equimolar adducts (B) was also observed with other dialkyl- and diarylcarbodiimides.The spectral properties (especially the value of 3JP-H) and reactivity of these adducts are strongly dependent on their conformation.The distinct conformational differences between the adducts B derived from DCC and diisopropylcarbodiimide (DiPC) and those obtained from dibenzylcarbodiimide (DBC) and diarylcarbodiimides were revealed by X-ray analysis of the selected N-phosphorylthioureas.By means of low temperature FT 31P NMR spectra it was demonstrated that the adducts (B) arise from the first formed unstable S(Se)-phosphorylisothio(seleno)ureas (A) as a result of S(Se)->N-phosphoryl migration.The differences in ability of the phosphoryl group to undergo S(Se)->N and O->N 1,3-shifts are briefly described.N-Phosphorylthio(seleno)ureas (B) obtained from DCC and DiPC, in contrast to those prepared from DBC and diarylcarbodiimides, reacted with a second thio(seleno)acid molecule.Crossover experiments and the use of O,O-diethyl phosphorothioate containing 35S-labeled sulfur showed that the adducts (B) are in equilibrium with their unstable isomers (A), the latter being active phosphorylating agents.The formation of the final reaction products was rationalized in terms of the threedirectional attack of the thioacid anion at the phosphorus, alkoxy carbon, and central carbon atoms of the protonated adduct (A).
- Mikolajczyk, Marian,Kielbasinski, Piotr,Basinski, Wlodzimierz
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p. 899 - 908
(2007/10/02)
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- Reactions of Group V Metal Compounds with Sulfur Trioxide
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Trialkylphosphines react with equimolar amounts of sulfuric trioxide to form the 1:1 adducts R3P(1+)-SO3(1-).Trialkylarsines and -stibines undergo sulfur trioxide insertion reaction across the metal-carbon bond to give the trisulfonates of the metal M(OSO2R)3 (M=As,Sb).The reactions of trialkyl phosphites, with sulfur trioxide yield trialkyl phosphonates, trialkyl thiophosates, dialkyl alkylphosphonates, dialkyl sulfates, and polymers which contain phosphorus atoms.The reactions of trialkoxyarsines and -stibines result in the insertion of sulfur trioxide across the metal-oxygen bond to form the alkoxymetal alkylsulfates (RO)3-nM(OSO3R)n (M=As,Sb; n=1,2,3) depending on the stoichiometric ratios of the reagents used.Pyrolysis of the metal sulfates gives dialkyl sulfates and undistillable residues containing the metals.
- Ando, Fumio,Koketsu, Jugo,Ishii, Yoshio
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p. 3495 - 3499
(2007/10/02)
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- DARSTELLUNG UND DESULFURIERUNG CYCLISCHER α,α-DICYANTHIOALLYLVERBINDUNGEN
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Thiomesoxalic acid diamide 1, obtained in situ by reaction of dibromomalonic acid diamide with potassium ethylxantogenate, adds to 1,3-dienes.The cycloadducts 2 upon dehydration yield the dicyanothioethers 3, with are desulfurized with trimethyl phosphite to give the vinylcyclopropane dicarbonitriles 5.
- Friedrich, Klaus,Gallmeier, Hans-Joachim
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p. 2971 - 2972
(2007/10/02)
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- Transformation of DAEP under Various Oxidative Conditions
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14C-DAEP was subjected to four different oxidative conditions, and the products were identified.On peracid oxidation in dichloromethane, DAEP gave the oxon (1) predominantly, and 2-acetylaminoethyl dimethoxyphosphinyl disulphide (3), N-acetylcysteamine (10), its oxidized dimer (11) and a further oxidation product of compound (11).This indicates that an unstable phosphorus oxythionate was initially formed, which lost sulfur, was rearranged, and hydrolyzed to give these products.Under other conditions, phosphinyl disulfide 3 was not found.DAEP was metabolized in vitro with a rat liver microsome-NADPH system via oxydation.The aqueous reaction condition prevented the formation of compound 3 from the intermediate, which predominated as well as the oxon formation under anhydrous or close conditions.The formation of various products with sunlight irradiation on glass plates or on bean leaves could be interpreted by oxidation at P=S, C1 and C2 positions, demethylation, and deacetylation, followed by further transformation.The initial formation of phosphorus oxythionate seems to play an important role in the oxidation of the organothionophosphorus compound.
- Miyamoto, Toru,Yamamoto, Izuru
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p. 1991 - 1998
(2007/10/02)
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- Properties and Reactions of Trimethyl Phosphite, Trimethyl Phosphate, Triethyl Phosphate, and Trimethyl Phosphorothionate by Ion Cyclotron Resonance Spectroscopy
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The gas-phase ion-molecule reactions occurring in trimethyl phosphite, trimethyl phosphate, triethyl phosphate, and trimethyl phosphorothionate have been investigated by ion cyclotron resonance spectroscopy.Protonated parent ions, tetracoordinated phosphonium ions, and cluster ions are the reaction products observed.The proton affinities of these compounds have been determined to be 222.9, 214.2, 218.7, and 216.6 kcal/mol, respectively (relative to PA(NH3) = 207.0 kcal/mol).Homolytic bond dissociation energies of the protonated species are calculated using adiabatic ionization potentials determined by photoelectron spectroscopy.The trends in these quantities are discussed.A reasonable value for the correlated homolytic bond dissociation energy of trimethyl phosphite indicates that the first ionization potential of this molecule should be assigned to the phosphorus lone pair.The application of chemical ionization mass spectrometry to the analysis of phosphorus esters is briefly discussed.
- Hodges, Ronald V.,McDonnell, T. J.,Beauchamp, J. L.
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p. 1327 - 1332
(2007/10/02)
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