- Reactions of diazoacetates with phosphate triesters and thiophosphate triester: >P+-O-C-P+-S-C-< intermediacy formation
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Diazoacetates 1a,b undergo BF3 · OEt2 catalyzed carbenoid attack on the oxygen of the phosphoryl double bond of phosphate triesters 2a-c or on the sulfur of thiophosphoryl double band of thiophosphate 9 to form corresponding O-alkoxycarbonylmethylphosphates 3a-c or S-alkoxycarbonylmethylphosphate 13.
- Popov, Konstantin A.,Polozov, Alexander M.,Tcherezov, Sergei V.
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- S-methylation of O,O-dialkyl phosphorodithioic acids: O,O,S-trimethyl phosphorodithioate and phosphorothiolate as metabolites of dimethoate in mice
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O,O,S-Trimethyl phosphorodithioate and phosphorothiolate [(MeO)2P(S)SMe and (MeO)2P-(O)SMe, respectively] are known from earlier studies to be impurities, delayed toxicants, and detoxication inhibitors in several major O,O-dimethyl phosphorodithioate insecticides. Our recent studies show extensive S-methylation of mono- and dithiocarbamic acids in mice, suggesting the possibility that phosphorodithioic acids such as (MeO)2P(S)SH might also undergo S-methylation. This possibility was examined in ip-treated mice with emphasis on the metabolites of dimethoate [(MeO)2P(S)SCH2C(O)NHMe], one of the most important organophosphorus insecticides. The urinary metabolites of dimethoate, which contains no P-SMe substituent, were found to include four compounds with P-SMe moieties identified by 31P NMR spectroscopy as MeO(HS)P(O)SMe, MeO(HO)P(O)SMe, (MeO)2P(S)SMe, and (MeO)2P-(O)SMe; the latter two compounds are also established by GC-MS as dimethoate metabolites in mouse urine, liver, kidney, and lung. Several approaches verified unequivocally that the previously unknown P-SMe metabolites in urine and tissues are due to in vivo S-methylation rather than to impurities. Studies with other O,O-dimethyl and O,O-diethyl phosphorodithioate insecticides established the analogous S-methylation pathway for ethion, malathion, phenthoate, phosalone, and phosmet in mice. Thus, metabolism of O,O-dialkyl phosphorodithioate insecticides in mammals is shown here for the first time to yield S-methyl phosphorodithioates and phosphorothiolates from in vivo S- methylation of the intermediate O,O-dialkyl phosphorodithioic acids.
- Mahajna, Mahmoud,Quistad, Gary B.,Casida, John E.
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- Synthesis, characterization and photocatalytic activity of Ag-TiO2 nanoparticulate film
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Ag-TiO2 nanoparticulate film was synthesized by dip coating followed by adsorption and photoreduction in UVA light, characterized by transmission electron microscopy, scanning electron microscopy, energy dispersive analysis of X-rays, glancing angle X-ray diffractometry and UV-Vis absorption spectrophotometry techniques. The data indicated the presence of TiO2 particles of anatase phase of size varying from 5-15 nm, Ag nanoparticles of size varying from 10-20 nm, and also indicated the added visible light activity in Ag-TiO2 nanoparticle films. Photocatalytic degradation of methyl parathion (O,O-dimethyl O-(4-nitrophenyl) phosphorothioate), a well known pesticide in aqueous solution was studied using Ag-TiO2 nanoparticulate film and the data was compared with TiO2 nanoparticulate film. Photocatalytic degradation reactions demonstrated pseudo first order behaviour. Methyl parathion was found to be degraded initially to paraoxon which further was degraded to p-nitrophenol, trimethyl ester of phosphoric acid, trimethyl ester of phosphothioic acid, and finally to phosphate ion. Minute amounts of carbon dioxide and acetaldehyde were also detected. This journal is
- Ramacharyulu,Praveen Kumar,Prasad,Srivastava
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p. 1309 - 1314
(2015/02/02)
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- A new method of introducing SCH3 and SCD3 groups to phosphorothioates
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A new synthesis of phosphorothioates starting from phosphites and cyanuric chloride (TCT)-activated DMSO is reported herein. This method enables the incorporation of SCH3 and SCD3 groups into phosphorothioates in good yields. The labeling purities of the products are excellent.
- Liu, Tianzhen,Cui, Xiaoxue,Yu, Zhifang,Li, Chunbao
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experimental part
p. 606 - 611
(2012/06/01)
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- Photolysis of methyl-parathion thin films: Products, kinetics and quantum yields under different atmospheric conditions
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The present study focuses on the photodegradation of methyl-parathion thin films, an organophosphate insecticide, under different atmospheric conditions. The latter include nitrogenated, oxygenated and ozonated atmospheres, under low and high relative humidity conditions. Addition of oxygen to the atmospheric mixture did not seem to affect the reaction rates and quantum yields. Relative humidity affect was minor, with a small enhancement in reaction rate under 254. nm radiation. The addition of ozone (to either dry or humid atmosphere), at all concentrations tested, largely enhanced degradation rates. In the absence of ozone, the obtained quantum yields for photolysis of methyl-parathion thin films under 254 and 313. nm were 0.024 ± 0.007 and 0.012 ± 0.005, respectively. These values are higher than the values previously reported for solutions of methanol and water. Although the presence of molecular oxygen and water vapors did not seem to affect much the reaction rates, it did have a certain effect on the resulted products. More polar products were obtained under oxygenated and ozonated atmospheres, as well as dimers under ozone conditions. The reaction on thin films has yielded more toxic products than usually found in solutions, adding alkylphosphate esters in addition to the oxons formed normally.
- Segal-Rosenheimer, Michal,Dubowski, Yael
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scheme or table
p. 193 - 202
(2010/10/01)
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- Reduction of dichlorvos and omethoate residues by O2 plasma treatment
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A practical, inexpensive, and green chemical process is greatly needed for degrading pesticides in food and environmental water. In this work, the impact of O2 plasma treatment on reduction of dichlorvos (DDVP) and omethoate in maize was determ
- Bai, Yanhong,Chen, Jierong,Mu, Hui,Zhang, Chunhong,Li, Baoping
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experimental part
p. 6238 - 6245
(2010/07/06)
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- Process for Preparing Malathion for Pharmaceutical Use
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The present invention provides a process for preparing a highly pure form of malathion having a reduced level of toxic impurities. In addition, the malathion prepared by the process of this invention is storage stable. The level of toxic impurities in the malathion, e.g., isomalathion, O,O,S-trimethyl phosphorodithioate (MeOOSPS), O,O,S-trimethyl phosphorothioate (MeOOSPO), O,S,S-trimethyl phosphorodithioate (MeOSSPO), malaoxon, isomalathion, diethyl fumarate, methyl malathion, dimethyl malathion, O,O-methyl,ethyl-S-(1,2-dicarboethoxy)ethyl-phosphorodithioate are lower than that of any other commercial preparation of malathion that may be used for pharmaceutical purposes.
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Page/Page column 12
(2008/06/13)
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- Preparation of organohalosilanes
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In an industrial process for preparing organohalosilanes by reacting metallic silicon particles with an organohalide in the presence of a copper catalyst, a contact mass composed of the metallic silicon and the catalyst further contains an effective amount of a phosphine chalcogenide compound. The invention drastically increases the silane formation rate and the utilization of silicon without lowering the selectivity of useful silane.
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- Stereoselective and chemoselective oxidation of phosphorothionates using MMPP
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MMPP (monoperoxyphthalic acid, magnesium salt) converts phosphorothionates to the corresponding oxons in good yields with excellent chemoselectivity and stereoselectivity.
- Jackson,Berkman,Thompson
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p. 6061 - 6064
(2007/10/02)
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- Solvolysis of allylic isoprene phosphorothioate esters. A mechanistic study of the thiono → thiolo rearrangement
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The reactions of O,O-dimethyl O-geranyl phosphorothionate (1-OPS(OMe)2), O,O-dimethyl S-geranyl phosphorothiolate (1-SPO(OMe)2), and O,O-dimethyl S-lianlyl phosphorothiolate (2-SPO(OMe)2) were studied in 65:35 TFE/water. Solvolysis of 1-OPS(OMe)2 at 20°C gave substantial amounts of thiolo isomers 1-SPO(OMe)2 and 2-SPO(OMe)2, along with smaller quantities of solvent addition products. At 40-65deg;C, rearrangement of linalyl phosphorothiolate 2-SPO(OMe) to geranyl phosphorothiolate 1-SPO(OMe)2 reacted at 90-120°C to give substitution products and 1-SPO2(OMe)2, formed by hydrolysis of a methyl. The relative reactivities of 1-OPS(OMe)2, 1-SPO(OMe)2, 2-SPO(OMe)2 are 1:(3 × 10-7):(6 × 10-3), respectively. From a combination of kinetic and trapping experiments, we estimate that 1-OPS(OMe)2 is 11 kcal/mol less stable than its thiolo isomer. A dissociative mechanism with ion-paired intermediates is proposed for the thiono → thiolo rearrangements, and the utility of the phosphorothioate moiety as a tool for studying reactions involving ion pairs is discussed.
- Poulter, C. Dale,Mautz, Douglas S.
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p. 4895 - 4903
(2007/10/02)
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- ALKOXYPHOSPHONIUM SALT INTERMEDIATES IN THE THIONO-THIOLO REARRANGEMENT OF PHOSPHYLTHIONATES IN PROTIC ACID MEDIA
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The thiono-thiolo rearrangement reaction of phosphonylthionates 1 catalyzed by protic acids proceeds with the formation of two types of intermediate alkoxyphosphonium salts 2 and 3.The first of these is formed by the protonation of the substrate 1 at the sulfur atom.Formation of 2 is evident from the changes in chemical shifts in 31P NMR spectroscopy of phosphylthionates upon their interaction with trifluoroacetic acid and also from the appearance of electrical conductivity in the solutions of substrates in TFA.The extent of protonation is consistent with the expected substituent effect on the basicity of thiophosphoryl sulfur.The second type of alkoxyphosphonium salt is formed by the alkylation of neutral esters with 2.The formation of 3 is observed in both 1H and 31P NMR spectra 3 were identified by their spectroscopic comparison with alkoxyphosphonium salts produced by alkylation of 1 with strong alkylation agents.The relative reactivity of a model alkoxyphosphonium salt towards a neutral ester and a phosphylthioate anion was investigated.In the absence of acid the rate of alkylation of the anion exceeds that of the alkylation of a neutral ester by three orders of magnitude.The protonation of phosphylthioate anion under acidic conditions results in a dramatic decrease in the rate of alkylation thereby leading to accumulation of 3 in the acidic reaction media.
- Bruzik, K. S.,Stec, W. J.
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p. 229 - 240
(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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- 1,3,2-Oxazaphospholidine-2-thiones from (+)-Norephedrine: Stereospecific Ring Opening, Possibly by an Elimination-Addition Mechanism
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1,3,2-Oxazaphospholidine-2-thiones derived from (+)-norephedrine react with alkoxide to give a product of kinetic control, formed by endocyclic P-O cleavage with inversion of configuration, and one of thermodynamic control, formed by endocyclic P-N cleavage also with inversion of configuration.It is suggested that the product of kinetic control is formed by an elimination-addition process involving a metaphosphorimidate intermediate, and that of thermodynamic control by a mechanism involving nucleophilic attack opposite endocyclic nitrogen.
- Hall, C.Richard,Inch, Thomas D.,Williams, Nancy E.
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p. 639 - 644
(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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