18264-30-7Relevant academic research and scientific papers
Leaving group assistance in the La3+-catalyzed cleavage of dimethyl (o-methoxycarbonyl)aryl phosphate triesters in methanol
Edwards, David R.,Liu, C. Tony,Garrett, Graham E.,Neverov, Alexei A.,Brown, R. Stan
supporting information; experimental part, p. 13738 - 13748 (2010/01/06)
The catalytic methanolysis of a series of dimethyl aryl phosphate triesters where the aryl groups contain an o-methoxycarbonyl (o-CO2Me) substituent (4a-i) was studied at 25°C in methanol containing La 3+ at various concentrations and sspH. Determination of the second-order rate constant for La3+ 2-catalyzed cleavage of substrate 4a (dimethyl (o-methoxycarbonyl) phenyl phosphate) as a function of sspH was assessed in terms of a speciation diagram that showed that the process was catalyzed by La3+ 2(-OCH3)x dimers, where x = 1-5, that exhibit only a 5-fold difference in activity between all the species. The second-order catalytic rate constants (k2La) for the catalyzed methanolysis of 4a-i at sspH 8.7 fit a Bronsted relationship of log k2La= (-0.82 ± 0.11)sspKalg + (11.61 ± 1.48), where the gradient is shallower than that determined for a series of dimethyl aryl phosphates that do not contain the o-CO2Me substituent, log k2La = (-1.25 ± 0.06)s spKalg + (16.23 ± 0.75). Two main observations are that (1) the o-CO2Me group preferentially accelerates the cleavage of the phosphate triesters with poor leaving groups relative to those with good leaving groups and (2) it provides an increase in cleavage rate relative to those of comparable substrates that do not have that functional group, e.g., k2La(dimethyl o-(methoxycarbonyl) phenyl phosphate)/k2La(dimethyl phenyl phosphate) = 60. Activation parameters for the La3+2-catalyzed methanolysis of 4a and dimethyl 4-nitrophenyl phosphate show respective ΔH? (ΔS?) values of 3.3 kcal/mol (-47 cal/mol·K) and 0.7 kcal/mol (-46.5 cal/mol·K). The data are analyzed in terms of a concerted reaction where the catalytic complex (La3+2( -OCH3)x-1) binds to the three components of a rather loose transition state composed of a nucleophile CH3O -, a nucleofuge -OAr, and a central (RO)2P 2+-O- in a way that provides leaving group assistance to the departing aryloxy group.
Electronic Structure and 31P NMR Chemical Shift of Substituted Triaryl, Diaryl Methyl and Dimethyl Aryl Phosphates - a Semi-empirical Molecular Orbital Approach
Silva, J. F. Cajaiba da,Pedrosa, M. S.,Nakayama, H. T.,Neto, C. Costa
, p. 97 - 106 (2007/10/03)
The 31P NMR chemical shift of triaryl phosphate, diaryl methyl phosphate and dimethyl aryl phosphate series was determined.The δ31P values exhibit an increasing downfield trend when aryl substituents are exchanged for alkyl groups and δ31P values show an increasing upfield trend as the electron withdrawing ability of the substituent in the aromatic ring is increased.Semi-empirical calculations showed an increasing positive charge on phosphorus atom and an increasing phosphoryl bond order when δ31P values go upfield.These results are in good agreement with the effect of "back bonding" from the phosphoryl oxygen to the phosphorus atom. - Keywords: 31P NMR chemical shifts; structural effects; molecular orbitals; triaryl phosphates; diaryl alkyl phosphates; dialkyl aryl phosphates
A CONVENIENT SYNTHETIC ROUTE TO PHOSPHATE ESTERS FROM PHOSPHITES
Purnanand,Batra, B. S.,Pant, B. P.
, p. 1687 - 1688 (2007/10/02)
Dialkyl arylphosphate esters have been synthesized in improved yields by the reaction of dicyclohexylamine salts of substituted phenols with dialkyl hydrogen phosphite and carbon tetrachloride.The reaction proceeds through the corresponding phosphorochloridates.
NEW PHOSPHORYLATING AGENTS FOR GENERAL SYNTHESIS OF MIXED PHOSPHATE ESTERS
Nagamatsu, Tomohisa,Kunieda, Takehisa
, p. 2375 - 2378 (2007/10/02)
An effective procedure has been developed for the general synthesis of mixed alkyl or aryl phosphate esters by metal-catalyzed phosphorylation of alcohols with aryl bis(2-oxo-3-oxazolinyl)phosphinate.Among metallic acetylacetonates examined as catalysts, the zirconium complex was the most effective as in activity order of Zr(IV)> Ce(III)> Zn(II)> Mn(III)> Mn(II)-complexes.
Selective phosphorylation process
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, (2008/06/13)
A one step process for the preparation of phosphate esters of phenol comprising reacting phenol with a dimethyl disulfide and a trialkyl phosphite.
