- Loci of ceric cation mediated hydrolyses of dimethyl phosphate and methyl methylphosphonate
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(formula presented) Dimethyl phosphate and methyl methylphosphonate are cleaved by Ce(IV)-mediated hydrolysis with 91% and 88% P-O scission, respectively, and rate accelerations of ≥ 1010 relative to pH 7 P-O hydrolysis.
- Moss, Robert A.,Morales-Rojas, Hugo
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Read Online
- METHOD FOR PRODUCING PHOSPHOESTER COMPOUND
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PROBLEM TO BE SOLVED: To provide a method whereby, a phosphate compound selected from the group consisting of orthophosphoric acid, phosphonic acid, phosphinic acid, and anhydrides of them is used as raw material and, by one stage reaction, a corresponding phosphoester compound is produced. SOLUTION: To an aqueous solution of a phosphate compound, added is an organic silane or siloxane compound having an alkoxy group or an aryloxy group, and the mixture is subjected to a heating reaction, thereby producing a corresponding phosphoester compound without requiring a catalyst. SELECTED DRAWING: None COPYRIGHT: (C)2021,JPOandINPIT
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Paragraph 0023; 0026-0028
(2021/09/27)
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- Isomer of linker for NU-1000 yields a newshe-type, catalytic, and hierarchically porous, Zr-based metal-organic framework
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The well-known MOF (metal-organic framework) linker tetrakis(p-benzoate)pyrene (TBAPy4?) lacks steric hindrance between its benzoates. Changing the 1,3,6,8-siting of benzoates in TBAPy4?to 4,5,9,10-siting introduces substantial steric hindrance and, in turn, enables the synthesis of a new hierarchically porous,she-type MOF Zr6(μ3-O)4(μ3-OH)4(C6H5COO)3(COO)3(TBAPy-2)3/2(NU-601), where TBAPy-24?is the 4,5,9,10 isomer of TBAPy4?.NU-601shows high catalytic activity for degradative hydrolysis of a simulant for G-type fluoro-phosphorus nerve agents.
- Lu, Zhiyong,Wang, Rui,Liao, Yijun,Farha, Omar K.,Bi, Wentuan,Sheridan, Thomas R.,Zhang, Kun,Duan, Jiaxin,Liu, Jian,Hupp, Joseph T.
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p. 3571 - 3574
(2021/04/14)
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- An Unusual Two-Step Hydrolysis of Nerve Agents by a Nanozyme
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Organophosphate-based nerve agents irreversibly inhibit acetylcholinesterase enzyme, leading to respiratory failure, paralysis and death. Several organophosphorus hydrolases are capable of degrading nerve agents including pesticides and insecticides. Development of stable artificial enzymes capable of hydrolysing nerve agents is important for the degradation of environmentally toxic organophosphates. Herein, we describe a Zr-incorporated CeO2 nanocatalyst that can be used for an efficient capture and hydrolysis of nerve agents such as methyl paraoxon to less toxic monoesters. This unusual sequential degradation pathway involves a covalently linked nanocatalyst-phosphodiester intermediate.
- Khulbe, Kritika,Roy, Punarbasu,Radhakrishnan, Anusree,Mugesh, Govindasamy
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p. 4840 - 4845
(2018/09/27)
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- A Light-Releasable Potentially Prebiotic Nucleotide Activating Agent
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Investigations into the chemical origin of life have recently benefitted from a holistic approach in which possible atmospheric, organic, and inorganic systems chemistries are taken into consideration. In this way, we now report that a selective phosphate activating agent, namely methyl isocyanide, could plausibly have been produced from simple prebiotic feedstocks. We show that methyl isocyanide drives the conversion of nucleoside monophosphates to phosphorimidazolides under potentially prebiotic conditions and in excellent yields for the first time. Importantly, this chemistry allows for repeated reactivation cycles, a property long sought in nonenzymatic oligomerization studies. Further, as the isocyanide is released upon irradiation, the possibility of spatially and temporally controlled activation chemistry is thus raised.
- Mariani, Angelica,Russell, David A.,Javelle, Thomas,Sutherland, John D.
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supporting information
p. 8657 - 8661
(2018/07/15)
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- Intriguing structural chemistry of neutral and anionic layered monoalkylphosphates: Single-source precursors for high-yield ceramic phosphates
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Building up on an available synthetic methodology, phosphate monoesters ROPO3H2 have been synthesized in good yields. The synthetic procedure employed features acetic anhydride mediated activation of phosphoric acid in the presence of alcohols, leading to the formation of phosphate monoesters. The products have been isolated as their cyclohexyl amine salts, [CyNH3]2[(MeO)PO3]·3H2O (1) and [CyNH3][(RO)PO3H] (Cy = cyclohexyl; R = Et (2), iPr (3), or tBu (4)). Neutralization of 1-4 by readily available inexpensive ion exchange resin Amberlite produces monoalkylphosphates (RO)P(O)(OH)2 (R = Me (5), Et (6), iPr (7), or tBu (8)). Thermally labile 1-4 and 7 have been structurally characterized by single crystal X-ray diffraction studies. Due to their intrinsic thermal instability due to β-H elimination, these compounds can be used as ligands for the preparation of single-source precursors for ceramic phosphates by reacting them with suitable metals ions. It is also possible to isolate co-crystals of the anionic and neutral forms of these phosphates as it has been demonstrated in the isolation and structural characterization of [(iPrO)PO3H2]·{[CyNH3][(iPrO)PO3H]} (9). To demonstrate the utility of these monoalkylphosphates in the low-temperature synthesis of metal phosphate bioceramics, isopropyl phosphate 7 has been employed to prepare calcium phosphate [{Ca((iPrO)PO3)(OH2)}·H2O]n (10), which undergoes neat thermal decomposition in two stages to lose water and propene to yield β-Ca2P2O7 at low temperatures (280 °C).
- Bhat, Gulzar A.,Kalita, Alok Ch.,Murugavel, Ramaswamy
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p. 5390 - 5401
(2017/09/26)
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- Method for preparing monoalkyl hypophosphite
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The invention relates to a method for preparing monoalkyl hypophosphite. The method comprises the steps of oxidizing monoalkyl hydrogen phosphide halate solution by virtue of hydrogen peroxide, wherein the molar ratio of the monoalkyl hydrogen phosphide halate solution to hydrogen peroxide is 1 to 2 or 1 to 2.1, and the reaction temperature is between (-50)-(20) DEG C. The molecular formula of monoalkyl hypophosphite is RP(H)OOH, wherein R is C1-C10 straight-chain, branched-chain alkyl groups. The method for preparing monoalkyl hypophosphite has the beneficial effects that the reaction yield is more than 80%, and water and halogen hydride can be easily evaporated at a reduced pressure after the reaction is finished and can be recycled by virtue of a sodium hydroxide solution and are not the main content of the invention, so that the method described by the invention is safe, environment-friendly and economic.
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Paragraph 0035; 0036; 0037
(2017/09/18)
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- Reactions of phosphate and phosphorothiolate diesters with nucleophiles: Comparison of transition state structures
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A series of methyl aryl phosphorothiolate esters (SP) were synthesized and their reactions with pyridine derivatives were compared to those for methyl aryl phosphate esters (OP). Results show that SP esters react with pyridine nucleophiles via a concerted SN2(P) mechanism. Bronsted analysis suggests that reactions of both SP and OP esters proceed via transition states with dissociative character. The overall similarity of the transition state structures supports the use of phosphorothiolates as substrate analogues to probe mechanisms of enzyme-catalyzed phosphoryl transfer reactions. This journal is The Royal Society of Chemistry.
- Ye, Jing-Dong,Barth, Christofer D.,Anjaneyulu, Potluri S. R.,Tuschl, Thomas,Piccirilli, Joseph A.
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p. 2491 - 2497
(2008/02/14)
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- Regioselective phosphorylation of carbohydrates and various alcohols by bacterial acid phosphatases; probing the substrate specificity of the enzyme from Shigella flexneri
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Bacterial non-specific acid phosphatases normally catalyze the dephosphorylation of a variety of substrates. As shown previously the enzymes from Shigella flexneri and Salmonella enterica are also able to catalyze the phosphorylation of inosine to inosine monophosphate and D-glucose to D-glucose 6-phosphate (D-G6P) using cheap pyrophosphate as the phosphate donor. After optimization high yields (95%) are achieved in the latter reaction and we show here that it is possible to use these enzymes in a preparative manner. This prompted us to investigate by using 31P NMR and HPLC also the phosphorylation of a broad range of carbohydrates and alcohols. Many cyclic carbohydrates are phosphorylated in a regioselective manner. Non-cyclic carbohydrates are phosphorylated as well. Phosphorylation of linear alcohols, cyclic and aromatic alcohols is also possible. In all cases the acid phosphatase from Shigella prefers a primary alcohol function above a secondary one. We conclude that these enzymes are an attractive alternative to existing chemical and enzymatic methods in the phosphorylation of a broad range of compounds.
- Van Herk, Teunie,Hartog, Aloysius F.,Van Der Burg, Alida M.,Wever, Ron
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p. 1155 - 1162
(2007/10/03)
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- Amino acid N-carboxyanhydrides: Activated peptide monomers behaving as phosphate-activating agents in aqueous solution
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The hydrolysis of valine N-carboxyanhydride (NCA) in aqueous phosphate buffers was shown to proceed through nucleophilic catalysis via an aminoacyl phosphate intermediate that displays phosphorylating capabilities through a potentially prebiotic process that simulates modern biochemical metabolic pathways. Copyright
- Biron, Jean-Philippe,Pascal, Robert
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p. 9198 - 9199
(2007/10/03)
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- Activation of acyl phosphate monoesters by lanthanide ions: Enhanced reactivity of benzoyl methyl phosphate
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Acyl phosphate monoesters are intermediates in many biochemical acylation reactions, such as those involving aminoacyl adenylates. Benzoyl methyl phosphate, a typical acyl phosphate monoester, is slowly hydrolyzed in neutral solutions but reacts rapidly with amines. Since biochemical processes of acyl phosphate monoesters involve accelerated reactions with oxygen-centered nucleophiles, we sought catalysts for hydrolysis and methanolysis of benzoyl methyl phosphate to mimic the biochemical outcome. Lanthanide ions are particularly effective catalysts, accelerating reactions much more than comparable levels of magnesium ion. Detailed kinetic analysis of the hydrolysis reactions reveals formation of a 1:1 complex, followed by rapid reaction with a nucleophile. The hydroxide-dependent hydrolysis rate in the europium complex is about 105 times that of free substrate with hydroxide. A mechanism that accounts for the data and observed behavior involves bidentate coordination of the metal ion by the acyl phosphate through phosphate and carbonyl oxygens, lowering the energy of the tetrahedral addition intermediate and the associated transition states. The dependence of the metal ion catalyzed process on the concentration of hydroxide ion is consistent with coordinated hydroxide acting as a nucleophile. The reaction of benzoyl methyl phosphate with methanol to form methyl benzoate and methyl phosphate is 30 000 times more rapid in the presence of 0.0001 M lanthanum triflate (in the absence of the metal ion kobs = 2.1 × 10-7 s-1, at 25°C). Thus, the combination of acyl phosphate esters and lanthanide salts appears to be a promising method for biomimetic acylation of hydroxyl groups.
- Kluger, Ronald,Cameron, Lisa L.
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p. 3303 - 3308
(2007/10/03)
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- Thermocatalytic Oxidation of Dimethyl Methylphosphonate on Supported Metal Oxides
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Thermocatalytic oxidation of dimethyl methylphosphonate (DMMP) was carried out on nickel, iron, copper, and vanadium oxides supported on γ-Al2O3. The vanadium catalyst was found to exhibit exceptional catalytic activity, even better than platinum catalysts. Varying the vanadium loading from 1 to 15% by weight indicated that 10% vanadium on Al2O3 was an optimal content. In conjunction with XRD patterns, monolayer dispersion of V2O5 on Al2O3 was considered to be beneficial to the longevity of these catalysts. Different supports, including Al2O3, SiO2, and TiO2, were examined and SiO2 was the optimum support because of its large surface area and the ability to resist poisoning by P2O5. On 10% V/SiO2 catalysts, 100% (to our limit of detection of 0.1%) conversion of DMMP was reached for more than 100 h at 723 K. IR, X-ray powder diffraction, ion chromatography, and XPS results illustrated that the used catalysts contained phosphorus species. The presence of methylphosphonic acid on the catalyst surface and downstream of the packed bed reactor demonstrated the difficulty of P-CH3 cleavage. The deposition of coke in the catalyst bed and along the reactor wall resulted from the dehydration of methanol and DMMP on P2O5. Accumulation of phosphorus species and coke on catalysts gave rise to a tremendous loss of surface area. However, P2O5 itself was observed to catalyze the decomposition of DMMP. A mechanism for this reaction was proposed to explain these experimental observations.
- Cao, Lixin,Segal, Scott R.,Suib, Steven L.,Tang, Xia,Satyapal, Sunita
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- Fragmentation of methyl hydrogen α-hydroxyiminobenzyl-phosphonates-kinetics, mechanism and the question of metaphosphate formation
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The thermodynamics, pH dependency and solvent effects of the fragmentation reaction of a series of α-oxyiminobenzylphosphonate monomethyl esters [(E)-1a-f] were examined in water and other hydroxylic solvents by UV and by 31P NMR spectroscopy at pH 0-3.1. The fragmentation of compounds (E)-1a-f was found to be a first-order reaction in substrate over the acidity range studied, while the dependence on the acidity is more complex, with rate constants k1 and k2. The ρ values corresponding to the first and second order rate constants were -1.12 and -0.835, respectively, indicating that the reaction is facilitated by electron-donating substituents, which probably enhance the protonation of the oxime OH group. Activation parameters for k1 and k2 reactions were also calculated. The near-zero values of the entropies of activation obtained are consistent with a dissociative transition state with almost no bonding to a nucleophilic solvent. Monitoring the fragmentation reaction of (E)-1a in several binary alcohol-water mixtures at different acidities showed that the reaction rate is enhanced by the alcohol's acidity and not hampered by the steric requirements of the alcohol molecule. This rules out in our opinion, the likelihood for nucleophilic solvent assistance in the rate-determining step. On the other hand, product studies show that both the nucleophilicity and the steric requirements of the alcohol are of importance in determining the product formed in the fragmentation of (E)-1a. The highest selectivity (S) value was found for MeOH, while S values of a common transition state and that the reaction coordinate includes at least one reactive intermediate, probably methyl metaphosphate. The results are compatible with a dissociative mechanism (DN*AN or DN + AN), in which the solvating water molecules pull the departing water molecule into the hydration shell, while the solvated phosphonic group becomes a metaphosphate without nucleophilic assistance. The fragmentation of oxyiminobenzylphosphonates to metaphosphate is perceived as a special case of the abnormal Beckmann reaction.
- Katzhendler, Jehoshua,Schneider, Hava,Ta-Shma, Rachel,Breuer, Eli
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p. 1961 - 1968
(2007/10/03)
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- Study of the mechanism for the hydrolysis of alkoxy(aryl)(phenyl)-λ6- sulfanenitriles, ArPhS(OR)(?N)
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The hydrolysis of alkoxy(aryl)(phenyl)-λ6-sulfanenitriles in several buffer solutions was found to follow a good pseudo-first-order kinetic equation, giving the corresponding sulfoximides and alcohols (for the case of the hydrolysis of neopentyloxy-λ6-sulfanenitrile, giving a rearranged product, 2-methyl-2-butanol). The dependence of the rate of hydrolysis on the structure of the alkyl group showed the opposite trend to the usual S(N)2 character, i.e. Me +] at pH more than 6.08, and trends to saturate at low pH. According to these kinetic results, a two-step reaction mechanism was proposed which involves a pre-equilibrium protonation on the nitrogen atom of the alkoxy-λ6- sulfanenitriles, followed by a rate-determining C-O bond cleavage via an S(N)2 or S(N)1 mechanism on the alkyl carbon atom depending on the structure of the alkyl group. From a double-reciprocal plot of 1/k(obs) vs. 1/[H+], the pK(a) value and the rate constant of the second reaction of neopentyloxy(diphenyl)-λ6-sulfanenitrile were estimated to be 5.02 and 7.02x10-3 s-1, respectively. The substituent effects on the phenyl group of neopentyloxy(diphenyl)-λ6-sulfanenitrile afforded a large negative p- value (-1.88) for pK(a) and positive one (+1.66) for the second reaction at 25.2 °C. The small negative p-values observed at pH 6.27 for diphenyl(propoxy)-λ6-sulfanenitrile (-0.42) and neopentyloxy(diphenyl)- λ6-sulfanenitrile (-0.26) were found to be the results of a cancellation of those for the opposite trend of the reactions of the pre-equilibrium and the second step. The activation parameters for both the pre-equilibrium and the subsequent reactions were also estimated based on the parameters for the hydrolysis of neopentyloxy(diphenyl)-λ6-sulfanenitrile at pH 6.22 and 2.99. The buffer effect is due to a nucleophilic attack of the buffer base to the alkyl carbon atom of the protonated alkoxy-λ6-sulfanenitriles. The sulfoximide moiety in the protonated λ6-sulfanenitrile is revealed to be a very good leaving group.
- Yoshimura, Toshiaki,Dong, Tiaoling,Fujii, Takayoshi,Ohkubo, Masanori,Sakuta, Mikiko,Wakai, Youko,Ono, Shin,Morita, Hiroyuki,Shimasaki, Choichiro
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p. 957 - 965
(2007/10/03)
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- Synthesis of Trialkyl Phosphates from White Phosphorus
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A new method was proposed for preparing trialkyl phosphates directly from white phosphorus by its electrolysis in a mixture of acetonitrile, alcohol, and water with tetraethylammonium iodide as supporting electrolyte. To increase the amount of the product synthesized in the unit volume of the electrolyte solution and the productivity of the process, phosphorus and water are added to the electrolyte in portions, which allows synthesis of up to 1 mol of trialkyl phosphate in 1 1 of the electrolyte solution.
- Romakhin,Nikitin
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p. 1023 - 1026
(2007/10/03)
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- Oxidative bioactivation of methamidophos insecticide: Synthesis of N- hydroxymethamidophos (a candidate metabolite) and its proposed alternative reactions involving N → O rearrangement or fragmentation through a metaphosphate analogue
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The systemic insecticide methamidophos, MeO(MeS)P(O)NH2, is a very weak inhibitor of acetylcholinesterase (ACHE) in vitro relative to in vivo suggesting bioactivation. This hypothesis is supported by finding that brain AChE inhibition and poisoning signs from methamidophos are greatly delayed in mice and houseflies pretreated with oxidase inhibitors in an order for effectiveness of methimazole > N-benzylimidazole >> piperonyl butoxide. In contrast, the order for delaying parathion-induced AChE inhibition and toxicity is N-benzylimidazole >> piperonyl butoxide or methimazole, suggesting that different oxidases are involved in methamidophos and parathion activation. N-Hydroxylation is examined here as an alternative to the controversial S-oxidation proposed earlier for methamidophos activation. N-Hydroxymethamidophos [MeO(MeS)P(O)NHOH], synthesized by coupling MeO(MeS)P(O)Cl and Me3-SiNHOSiMe3 followed by desilylation, is unstable at pH 7.4 (t( 1/4 ) = 10 min at 37 °C) with decomposition by two distinct and novel mechanisms. The first mechanism (A) is N → O rearrangement to MeO(MeS)P(O)ONH2 and then hydrolysis to MeO(MeS)P(O)OH, a sequence also established in the analogous series of (MeO)2P(O)NHOH → (MeO)2P(O)ONH2 → (MeO)2P-(O)OH. The second mechanism (B) is proposed to involve tautomerism to the phosphimino form [MeO(MeS)P(OH)=NOH] that eliminates MeSH forming a metaphosphate analogue [MeOP(O)=NOH] trapped by water to give MeO(HO)P(O)NHOH that undergoes the N → O rearrangement as above and hydrolysis to MeOP(O)(OH)2. As a metaphosphate analogue, the metaphosphorimidate generated from MeO(MeS)P(O)NHOH in aqueous ethanol yields MeOP(O)(OH)2 and MeO(EtO)P(O)OH in the same ratio as the solvents on a molar basis. Reactions of the N- and O-methyl derivatives of MeO(MeS)P(O)NHOH and (MeO)2P(O)NHOH are consistent with proposed mechanisms A and B. N-Hydroxymethamidophos is less potent than methamidophos as an AChE inhibitor and toxicant possibly associated with its rapid hydrolysis. Bioactivation of methamidophos via a metaphosphate analogue would directly yield a phosphorylated and aged AChE resistant to reactivating agents, an intriguing hypothesis worthy of further consideration.
- Mahajna, Mahmoud,Casida, John E.
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- The mechanism of decomposition of N-methyl-N-nitrosourea (MNU) in water and a study of its reactions with 2'-deoxyguanosine, 2'-deoxyguanosine 5'-monophosphate and d(GTGCAC)
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The carcinogenicity of N-methyl-N-nitrosourea (MNU) arises, from its ability to methylate DNA, This occurs in an aqueous environment and therefore an appreciation of the mode of decomposition of MNU in water is essential to understanding the mechanism of DNA methylation and its base sequence dependence. The kinetics of MNU hydrolyses are shown to be first order in MNU with a steep rise in rate above pH 8. Using NMR for in situ monitoring of reaction intermediates and products from hydrolyses of [13CO]MNU, [15NH2]MNU and [13CH3]MNU, it is proved that base-induced hydrolysis of MNU is initiated by deprotonation at the carbamoyl group. The critical reactive species are shown to be the methyldiazonium ion (Me-N2+) and cyanate (NCO-). Investigations of reactions of [13CH3]MNU with 2'-deoxyguanosine (dGuo) and 2-deoxyguanosine 5'-monophosphate (dGuo-5P) showed that: a) the site of methylation of dGuo is highly pH-dependent (relatively more N-1 and O6-methylation compared to N-7 occurs at higher pH; b) the principal site of methylation of dGuo-5P by MNU is at phosphate; c) incorporation of deuterium into methyl groups occurs in D2O at higher pH. Methylation of the oligonucleotide d(GT[15N]GCAC) by MNU in D2O showed partial deuteriation of the N7-methyl groups of the guanines, whilst methylation by MNU in water indicated no significant preference for either guanine with respect to N7-methylation.
- Golding, Bernard T.,Bleasdale, Christine,McGinnis, Joseph,Mueller, Susanna,Rees, Hue Thu,Rees, Nicholas H.,Farmer, Peter B.,Watson, William P.
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p. 4063 - 4082
(2007/10/03)
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- Use of Bis N,N-Dialkylphosphoramidites for the Synthesis of Phosphate Monoesters
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The bis N,N-dialkylphosphoramidites 7a and b and bis N,N-dialkylphosphoramidites 6a and b have been prepared by reaction of the N,N-dialkylphosphorochloridites 5a and b with the appropriate 2-(trialkylsilyl)ethanol.In the presence of 1H-tetrazole, the phosphoramidites 6a, b and 7a, b phosphorylated MeOH, PhCH2OH, PhCH2CH2OH, Me(PhCH2CH2(CHOH, 2,3,4,5,6-penta-O-benzyl-myo-inositol and ButOH, to give the phosphites 8a-h.Without isolation, these were oxidized to the corresponding phosphate triesters 9a-h with m-chloroperbenzoic acid.Treatment of the triesters 9a-h with tetrabutylammonium fluoride removes only 2-(trialkylsilyl)ethyl group to give the diesters 10a-h, whereas treatment with a solution of hydrofluoric acid in acetonitrile-water gives the phosphate monoesters 11a-e.
- Ross, Kenneth C.,Rathbone, Daniel L.,Thompson, William,Freeman, Sally
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p. 421 - 426
(2007/10/02)
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- (E)-(Hydroxyimino)(hydroxymethoxyphosphinyl)acetic Acid: Synthesis and pH-Dependent Fragmentation
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In contrast to both its parent "troika" acid (E-1, a phosphorylating agent at pH 7 and 25 deg C) and its C-methyl isomer (E-2, which is stable at both acidic and neutral pH), (E)-(hydroxyimino)(hydroxymethoxyphosphinyl)acetic acid E-3 was unreactive at pH 7 and 25 deg C but at pH 1.5 fragmented to methyl phosphate 10 (15percent) and methyl phosphorocyanidate 11 (85percent).The minor product is consistent with solvent phosphorylation, the reaction exclusively observed with E-1.The non-phosphorylating fragmentation pathway is proposed to involve a preliminary E -> Z isomerization of 3 prior to Cα-Cβ cleavage.Dual fragmentation pathways were also detected (31P NMR) when the DCHA+ salt of E-3 (E-9) was heated in acetonitrile or EtOH; in addition to phosphorylation products (16-19percent), 11 was formed (81-84percent).Reaction of E-9 in refluxing EtOH:t-BuOH (1:1) showed low stereoselectivity in product formation (ca. 3:1 ethyl methyl phosphate : t-butyl methyl phosphate), supporting a dissociative phosphorylation process.
- Kashemirov, Boris A.,Fujimoto, Mari,McKenna, Charles E.
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p. 9437 - 9440
(2007/10/02)
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- Catalytic Oxidation of Dimethyl Methylphosphonate
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The catalytic oxidation in air of dimethyl methylphosphonate (DMMP), a nerve gas stimulant, has been studied over laboratory-prepared Pt/Al2O3 as a function of Pt loading (0.5 or 2.0percent) and temperature (150, 250, or 400 deg C).At 250 deg C and residence time of 0.69 s, carbon balances indicate that 90-95percent of the C atoms in the DMMP feed were completely oxidized to CO2 during the periods when DMMP destruction was > 99percent (50 h for the 0.5percent Pt catalyst and 76 h for the 2.0percent Pt catalyst).Only after the end of these protection periods was methanol detected in the gaseous effluent.HPLC analysis of a product liquid showed that four intermediate P-containing compounds were formed: dimethyl phosphate (DMP), monomethyl phosphate (MMP), monomethyl methylphosphonate (MMMP), and methylphosphonic acid (MPA).A reaction scheme is proposed to account for the production of these intermediates by a series of oxidative and hydrolytic reactions.Different behavior was observed at 400 deg C.Although the period of complete DMMP destruction was very long ( > 135 h) with 0.5percent Pt catalyst, oxidation as measured by CO2 production was incomplete and the oxidation activity decreased with time on stream.At 400 deg C the hydrolytic reactions apparently become sufficiently efficient to effect complete DMMP conversion for extended periods despite the drop in oxidation activity.Several methods of characterizing deactivated catalyst provide incremental evidence that catalyst alumina reacts with product phosphoric acid to give AlPO4.
- Tzou, T. Z.,Weller, S. W.
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p. 370 - 374
(2007/10/02)
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- Novel Triazenes and Triazolines from the Base-Catalyzed Hydrolysis of 1,3-Dialkyl-3-acyltriazenes
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The products and mechanism of hydrolytic decomposition of a series of 1,3-dialkyl-3-acyltriazenes were studied in alkaline buffers.In general the mechanism of decomposition involves deacylation leading to the formation of the parent 1,3-dialkyltriazene.The solvent deuterium isotope effect (kH2O/kD2O) is less than 1.0, indicating specific base catalysis.A plausible mechanistic explanation is rapid reversible attack by hydroxide ion, followed by rate-limiting heterolysis of the N(1)-acyl bond.The resultant, 1,3-dialkyltriazene is somewhat unstable under the reaction conditions and undergoes subsequent hydrolysis, a reaction previously shown to be specific acid-catalyzed.When the N(1) alkyl group is 2-chloroethyl, unusual products are obtained.For the 3-acetyl and 3-carbethoxy derivatives, the initial deacylation product, 1-(2-chloroethyl)-3-methyltriazene, efficiently cyclizes to form 1-methyltriazoline.The 3-(methylcarbamoyl) derivative does not deacylate, but instead undergoes dehydrohalogenation to 1-vinyl-3-methyl-3-(methylcarbamoyl)triazene.
- Smith, Richard H.,Wladkowski, Brian D.,Herling, Julie A.,Pfaltzgraff, Timothy D.,Taylor, Jesse E.,et al.
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p. 6448 - 6454
(2007/10/02)
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- CONVENIENT SYNTHETIC ROUTE TO MONO- OR DIAKLYL PHOSPHATE FROM INORGANIC PHOSPHORUS ACIDS
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Mono- or dialkyl phosphate was synthesized in a favorable yield by oxidation of phosphonic or phosphinic acid in alcohol with oxygen at the presence of a catalytic amount of copper(II)chloride.The reaction may proceed via the formation of corresponding phosphorochloridate or phosphorochloridite.
- Okamoto, Yoshiki,Kusano, Tetuya,Takamuku, Setsuo
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p. 195 - 200
(2007/10/02)
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- α-OXYIMINOPHOSPHONATES: CHEMICAL AND PHYSICAL PROPERTIES. REACTIONS, THEORETICAL CALCULATIONS, AND X-RAY CRYSTAL STRUCTURES OF (E) AND (Z)-DIMETHYL α-HYDROXYIMINOBENZYLPHOSPHONATES
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Dialkyl α-oxyiminoalkylphosphonates, obtained by treatment of dialkyl acylphosphonates with hydroxylamine or methoxylamine, are mostly mixtures of E and Z isomers.Structural assignments of the oximes were based on X-ray crystallographic analysis of representative compounds: (E)- and (Z)-dimethyl α-hydroxyiminobenzylphosphonates .The (31)P n.m.r. chemical shifts of the E isomers always appear at lower field than those of the corresponding Z isomers.Thermal fragmentation of (1a) affords benzonitrile and dimethyl hydrogen phosphate, with (Z)-(1a) reacting faster than the E isomer. α-Oxyiminophosphonates undergo EZ isomerisation catalysed either by acid or by base under certain conditions, the E isomer being the thermodinamically more stable one.An E + Z mixture of dialkyl α-oxyiminophosphonates can be mono-de-alkylated by non-basic nucleophiles (e.g.NaI) to afford monoalkyl oxyiminophosphonates of unchanged isomeric composition.The geometrical isomers of α-hydroxyiminophosphonates differ in their behaviour under basic conditions.While treatment of (E)-(1a) with NaOH in boiling methanol leads, by mono-de-alkylation, to sodium methyl α-hydroxyiminobenzylphosphonate , under the same conditions (Z)-(1a) undergoes fragmentation, by C-P bond cleavage, to benzonitrile and dimethyl hydrogen phosphate.Control experiments established that the fragmentation of (Z)-α-hydroxyiminophosphonates involves an intramolecular attack on the phosphorous atom by the ionized Z oriented oxime oxygen.Similar differences in behaviour are noted between the isomers of the monoanions of α-hydroxyiminophosphonates.MNDO/H Calculations demonstrate the feasibility of forming internal hydrogen bonds in Z isomers, and their possible contribution to conformational preferences.Single-crystal X-ray diffraction studies of (E)- and (Z)-(1a), and (E)-(2b), clearly identified the geometric isomers and correlated them with (1H) and (31)P n.m.r. resonances.
- Breuer,Eli,Karaman, Rafik,Goldblum, Amiram,Gibson, Dan,Leader, Haim,et. al.
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p. 3047 - 3058
(2007/10/02)
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- Phosphorylation with Pyrophosphoric Acid
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Dihydrogenphosphates of primary and secondary aliphatic alcohols as well as phenol were prepared by a very simple procedure with pyrophosphoric acid. t-Butyl and benzyl dihydrogenphosphates could be obtained by a slight modification of the reaction conditions.For the purpose of phosphorylation pyrophosphoric acid was more reactive than orthophosphoric acid.
- Yamaguchi, Hachiro,Ogura, Fumio,Otsubo, Tetsuo,Ikeura, Yasuhiro
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p. 1891 - 1892
(2007/10/02)
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- Synthesis of Chiral Phosphate Esters
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A stereospecific route for the synthesis of chiral phosphate monoesters of known absolute configuration is described.
- Cullis, Paul M.,Lowe, Gordon
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p. 2317 - 2321
(2007/10/02)
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- Monomeric Methyl Metaphosphate: Reactions with Carbonyl Groups
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Monomeric methyl metaphosphate, generated by fragmentation of methyl hydrogen erythro-1-phenyl-1,2-dibromopropylphosphonate in the presence of 2,2,6,6-tetramethylpiperidine, can be identified by its electrophilic attack on the aromatic rings of substituted anilines.The aromatic substitution reactions are quenched by pyridine, acetonitrile, dioxane, and dimethoxyethane but not by chloroform.Monomeric methyl metaphosphate attacks acetophenone to yield an enol phosphate; it converts a mixture of o-trifluoromethylaniline and acetophenone into N-(1-methylbenzylidene)-2-aminobenzotrifluoride and also converts aniline and ethyl benzoate into O-ethyl-N-phenylbenzimidate.These latter reactions mimic enzymatic reactions that require ATP.These facts introduce the possibility that ATP plays a kinetic role as well as a thermodynamic one in metabolic processes.
- Satterthwait, Arnold C.,Westheimer, F. H.
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p. 4464 - 4472
(2007/10/02)
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- PHOSPHORYL TRANSFER FROM PHENYL AND 4-NITROPHENYL PHOSPHATES IN APROTIC AND PROTIC SOLVENTS. AMINE CATALYSIS AND FORMATION OF OXYPHOSPHORANE AND METAPHOSPHATE INTERMEDIATES
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The behavior of 4-nitrophenyl dihydrogen phosphate, ArOPO3H2, and of its tetra-n-butylammonium and tetramethyl ammonium salts, ArOPO3H-R4N+, ArOPO32-2(R4N+), was studied in aprotic solvents, in the absence and in the presence of increasing amounts of alcohols or water.The reactions were investigated in the absence of amines, and in the presence of hindered and unhindered amines, diisopropylethylamine and quinuclidine.The course of the reactions was followed at 35 deg C or at 70 deg C by (31)P and (1)H NMR spectrometry.Values for the approximate half-times of the reactions were estimated (+/-25percent) from the times at which reactantsignal intensity becomes equal to product signal intensity.The mononitrophenyl ester transfers its phosphoryl group to alcohols and water from the diprotonated acid by the addition-elimination mechanism via oxyphosphorane intermediates, and from the monoanion and dianion by the elimination-addition mechanism via the monomeric metaphosphate intermediate, PO3-.Formation of PO3- is faster from dianion than from monoanion in acetonitrile and in alcohol solutions.Conversely, PO3- is generated at a faster rate from monoanion than from dianion in aqueous solution.This effect results from a decrease in the rate of formation of PO3- in the solvent series: acetonitrile > alcohols > water.The rate depression as a function of the medium is greater for the dianion than for the monoanion, and is attributed to greater solvation of the more polar phosphate ground state than of the less polar transition state in the more polar protic solvents.Unhindered amines add to 4-nitrophenyl phosphate monoanion, but not to the dianion.The oxyphosphorane intermediate thus formed collapses to aroxide ion and a protonated dipolar phosphoramide which is rapidly deprotonated by the relatively basic 4-nitrophenoxide: ArOPO3H- + CH(CH2CH2)3N(acetonitrileCH(CH2CH2)3N+P(O)(OH)O- + ArO-CH(CH2CH2)3N+PO32- + ArOHCH(CH2CH2)3N + PO3-.The postulated formation of PO3- by this route, explains why the addition of quinuclidine to an acetonitrile solution containing the monoanion salt, ArOPO3H-R4N+, and t-BuOH produces t-butyl phosphate at a faster rate than the addition of diisopropylethylamine to the same solution. 2,4-Dinitrophenyl phosphate, which was previously studied by the same techniques, reacts via oxyphosphorane intermediates from the diprotonated and the monoanion forms, and via monomeric metaphosphate, from the dianion form.
- Ramirez, Fausto,Marecek, James F.
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p. 3151 - 3160
(2007/10/02)
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