Describes a method for obtaining substantially pure chloromethyl chloroformate from a chloroformate mixture comprising chloromethyl chloroformate and methyl chloroformate by heating the chloroformate mixture in a reaction zone at temperatures ranging from at least 50° C. to the reflux temperature of the chloroformate mixture in the reaction zone while simultaneously removing volatile gaseous decomposition products from the reaction zone. Dichloromethyl chloroformate may also be present in the chloroformate mixture.
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Page 7
(2008/06/13)
Water-mediated proton transfer: A mechanistic investigation on the example of the hydration of sulfur oxides
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.
p. 5137 - 5145
(2007/10/03)
Acyloxymethyl carbonochloridates. New intermediates in prodrug synthesis
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
p. 1159 - 1166
(2007/10/02)
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