- Microwave-assisted esterification of P-acids
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The possibilities for the preparation of dialky phenylphosphonates were evaluated. On the one hand, the oxidation of phenyl-H-phosphinates gave the corresponding phenylphosphonic acid monoesters. On the other hand, phenylphosphonates may be prepared by MW-assisted direct esterification of phenylphosphonic acid. The reaction with alcohols was performed under MW irradiation in the presence of an ionic liquid as the catalyst. The second ester function was established by alkylating esterification carried out with alkyl halides in the presence of triethylamine under MW conditions.
- ábrányi-Balogh, Péter,Harsági, Nikoletta,Keglevich, Gy?rgy,Kiss, Nóra Zsuzsa
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- Synthesis of phosphonates from phenylphosphonic acid and its monoesters
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Possibilities for the mono- and diesterification of phenylphosphonic acid were evaluated considering the microwave(MW)-assisted direct esterification, and the alkylating esterification. It was found that regarding the monoesterification, the reaction with 15-fold alcohol excess in the presence of [bmim][BF4] additive utilizing MWs is superior than the approach by alkylation. At the same time, for the conversion of the monoester intermediate to the diester, the reaction with alkyl halides in the presence of triethylamine as the base, again under MW irradiation, was found to be the method of choice. Phosphonates with both identical and different alkoxy groups were made available.
- Henyecz, Réka,Kiss, Adrienn,Mórocz, Virág,Kiss, Nóra Zsuzsa,Keglevich, Gy?rgy
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p. 2642 - 2650
(2019/08/08)
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- Synthesis of alkyl- and arylphosphonic acid monoesters by direct esterification of dibasic phosphonic acids in the presence of an arsonic acid catalyst
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Partial hydrolysis of a diester, hydrolysis of the monochloro monoester, or alcoholysis of a phosphonic acid anhydride generally is used to prepare monoesters of alkyl- and arylphosphonic acids. Limited cases have been reported for the esterification of a dibasic phosphonic acid to yield the monoester, and none of these methods are as simple as the analogous method for preparing carboxylic acid esters, in which the carboxylic acid is esterified with an alcohol in the presence of an acid catalyst. Described is a method for preparing monoesters of alkyl- and arylphosphonic acids by direct esterification with an alcohol in the presence of a catalytic amount of phenylarsonic acid. The water formed during the reaction is removed azeotropically. For example, methylphosphonic acid was esterified in good yield to give its isopropyl, butyl, cyclohexyl, bornyl, and octadecyl monoesters. Similarly prepared are the ethyl, butyl, hexyl, and 2-(ethylthio)ethyl monoesters of phenylphosphonic acid, as well as 2-isopropoxyethyl hydrogen ethylphosphonate and 2-methoxyethyl hydrogen benzylphosphonate.
- Crenshaw, Michael D.
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p. 1509 - 1516
(2007/10/03)
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- The Mechanistic Diversity of the Thermal and Photochemical Decomposition of Bis(phenylphosphonoyl)Peroxides: Concerted Polar, Homolytic and Electron-Transfer Processes. On the Reactivity of (Phenylphosponoyl)oxyl Radicals
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The thermal and photochemical decomposition of the first bis(phenylphosphonoyl)peroxides, dioxybis (5), and dioxybis (6) has been studied in various solvents by 1H-, 13C-, and 31P-NMR spectroscopy, laser flash photolysis (LFP), and ESR spin-trapping experiments.Kinetic studies reveal at 20 deg C a ca. 270 times slower thermal decay for 5 than for 6, which primarily results from a lower A factor rather than differences in the activation energies.The thermal decay of 5 occurs predominantly by a novel, presumably concerted polar rearrangement with formation of a thermally unstable, mixed phosphonoyl-phosphoryl anhydride.Photolysis of 5 induces homolytical cleavage of the peroxy bond with release of oxyl radicals 7.Radical 7 is characterized by a broad, transient UV/Vis absorption spectrum in the 400 to >700 nm range (λmax ca. 580 nm), as has been demonstrated by 248-nm LFP of 5 in acetonitrile solution.The short lifetime of this absorption indicates an extremely high reactivity (in hydrogen abstraction and addition) of this electrophilic radical.The thermal and photochemical decomposition of peroxide 6 leads to a virtually identical product distribution, suggesting O-O bond cleavage to be the major initial reaction under both conditions.LFP at 248 and 308 nm of a solution of 6 in acetonitrile initially produces a weak, broad absorption at ca. 500 nm and stronger bands at 280 and 400 nm.The highly transient 500-nm absorption is assigned to the oxyl radical 8, the other bands are attributed to the phosphonoyloxy-substituted benzene radical cation 8Z.The formation of this species can be explained in terms of electron transfer in the first-formed oxyl radical 8 and/or the intact peroxide 6, followed by cleavage of the peroxy bond.The decay of 8Z is accompanied by the build-up of the absorption spectrum of a 1,4-dioxy-substituted biphenyl radical cation.Key Words: Oxyl radicals / Phosphonoyl peroxides / Laser flash photolysis /ESR-Spin trapping / Electron transfer
- Korth, Hans-Gert,Lommes, Petra
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p. 2419 - 2438
(2007/10/02)
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- PHOSPHORORGANISCHE VERBINDUNGEN. 115. WEGE ZUM ANALYTISCHEN NACHWEIS VON VERBINDUNGEN MIT DER P(O)F- UND P(O)SR-GRUPPE
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Acridine-9-hydroxamic acid 5 is suitable for the analytical detection of the model phosphorylfluorides 7 by fluorescence.The model compounds are rearranged according to Lossen and degradated to the fluorescent 9-aminoacridine 6 using defined reaction conditions.Thiophospho-S-esters (with diethylthiophosphinic acid-S-butylester 8 as a model compound) are cleaved to the corresponding phosphorylfluorides (a) and mercaptanes (b) by fluorolysis. (a) is identified qualitatively with acridine-9-hydroxamic acid 5, (b) by the Ellman-reaction.
- Horner, Leopold,Hallenbach, Werner
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p. 301 - 312
(2007/10/02)
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- PHOSPHORORGANISCHE VERBINDUNGEN 95. Beschleunigte Hydrolyse von Organophosphorverbindungen durch Phasentransferkatalyse und H2O2 als Supernucleophil
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The alkaline hydrolyses of the physiologically active phosphor compounds: butyl-phenylfluorophosphonate 1 and di-isopropyl-fluorophosphate were studied under phase-transfer (PT) conditions.The influence of pH, the structure of the phase-transfer catalyst, the nature of the organic phase and the use of the supernucleophile HO2- on the hydrolysis was investigated.The hydrolysis of 1 is accelerated by a factor of ca. 550 (toluene) resp. ca. 520 (tetrachloroethylene) compared with the uncatalysed reaction.In concrete terms, the compound 1 can be completely hydrolysed in three (tuloene) resp. in one minute (tetrachloroethylene) under optimal conditions.
- Horner, Leopold,Kappa, H. Wilfried
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p. 339 - 348
(2007/10/02)
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