- Method and device for the production of phosgene from diphosgene and/or triphosgene
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The invention concerns a method for preparing phosgene from diphosgene and/or triphosgene, by reaction on a catalyst comprising one or several compounds with one or several nitrogen atoms with a pair of deactivated electrons. The invention further concerns a device for preparing phosgene from diphosgene and/or triphosgene, for implementing said method.
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- Water-mediated proton transfer: A mechanistic investigation on the example of the hydration of sulfur oxides
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We outline general mechanistic features of "water-mediated proton transfer" in the example of the isomerization reaction in hydrogen-bonded sulfur oxide-water supermolecules containing up to three water molecules. The nucleophilic attack of a water oxygen on the sulfur atom occurs concertedly with the (multiple) protontransfer event(s). The protons are transferred according to the well-known hydrogen-bond compression mechanism. However, contrary to "pure" multiple proton-transfer reactions, the protons are transferred asynchronously. These mechanistic features force the reaction to be classical rather than quantum-tunneling-dominated down to rather low temperatures. In the quantum-dominated temperature region, tunneling takes place only if all protons tunnel through the barrier. Straight line corner cutting (large curvature tunneling) does not dominate at any temperature, as the reduced mass corresponding to reaction coordinate motion does not drop to values low enough in the reaction barrier region. The asymmetric nature of the potential energy surface even allows different mechanisms involving transient H3O+ rotation termed "molecular swing" and a H2SO3 isomerization to be favorable compared to water-mediated triple proton transfer in the case of three participating water molecules.
- Loerting, Thomas,Liedl, Klaus R.
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p. 5137 - 5145
(2007/10/03)
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- Process for preparing cyclopropylacetylene
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The invention relates to a process for the halogenation of cyclopropylmethyl ketone with at least one dihalo-triorganophosphorane of the general formula I R3PHal2??(I), in which the radicals R can be the same or different and denote a saturated or unsaturated aliphatic C1-C20hydrocarbon radical, a phenyl or (C1-C4alkyl)phenyl radical, which may be optionally substituted by one or two fluorine, chlorine and/or nitro groups, P stands for phosphorus and Hal denotes chlorine, bromine, or iodine, at a temperature of from 800° to 130° C., where the dihalo-triorganophosphane of the general formula (I) is synthesized in situ from triorganophosphane oxide or triorganophosphane sulfide of the general formula II R3PA ??(II), in which R is as defined above with respect to formula I and A denotes oxygen or sulfur, using a halogenating agent, wherein the triorganophosphane oxide or triorganophosphane sulfide is used in catalytic amounts, to the halogenation product of cyclopropylmethyl ketone obtained in said process, and to a process for the conversion of said halogenation product to cyclopropylacetytene.
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- Conversion of bis(trichloromethyl), carbonate to phosgene and reactivity of triphosgene, diphosgene, and phosgene with methanol
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Triphosgene was decomposed quantitatively to phosgene by chloride ion. The reaction course was monitored by IR spectroscopy (React-IR), showing that diphosgene was an intermediate. The methanolysis of triphosgene in deuterated chloroform, monitored by proton NMR spectroscopy, gave methyl chloroformate and methyl 1,1,1-trichloromethyl carbonate in about a 1:1 ratio, as primary products. The reaction carried out in the presence of large excess of methanol (0.3 M, 30 equiv) was a pseudo-first-order process with a k(obs) of 1.0 x 10-4 s-1. Under the same conditions, values of k(obs) of 0.9 x 10-3 s-1 and 1.7 x 10-2 s-1 for the methanolysis of diphosgene and phosgene, respectively, were determined. The experimental data suggest that, under these conditions, the maximum concentration of phosgene during the methanolysis of triphosgene and diphosgene was lower than 1 x 10-5 M. Methyl 1,1,1-trichloromethyl carbonate was synthesized and characterized also by the APCI-MS technique.
- Pasquato,Modena,Cotarca,Delogu,Mantovani
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p. 8224 - 8228
(2007/10/03)
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- 5'-O-Dans EOC modified nucleosides and methods for preparing same
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Dansylethoxycarbonyl (Dans-EOC) groups which can be employed as base-labile 5'hydroxyl protective groups in chemical oligonucleotide synthesis are disclosed. These groups allow the preparation of a compound of the formula (I) STR1 which comprises reacting the compound of the formula (II) STR2 with a chlorocarbonyl donor.
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- Acyloxymethyl carbonochloridates. New intermediates in prodrug synthesis
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The synthesis of a number of stable acyloxymethyl carbonochloridates 7 has been accomplished in four steps from chloromethyl carbonochloridate 3. Each step has been optimized with propanoyl-oxymethyl carbonochloridate 7c as a model compound (64% overall yield). Diethyl ether-boron trifluoride catalyzes the conversion of carbonothioate 6cc to the carbonochloridate 7c by chlorination with sulfuryl chloride. Acylation of a few compounds containing hydroxy or amino groups by 7c is described.
- Folkmann,Lund
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p. 1159 - 1166
(2007/10/02)
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