Kinetic Isotope Effects on Ethyl Metaphosphate Transfer from a Phosphoramidate to Ethanol
摘要:
Kinetic isotope effects of nitrogen and hydrogen on thermolysis of O-ethyl N-mesityl- (1) and O-ethyl N-phenylphosphoramidates (2) in anhydrous ethanol at 80 degrees C are reported. The solvent hydrogen effect k(EtOH)/k(EtOD) is equal to 0.62 +/- 0.03 for 1 and 0.67 +/- 0.05 for 2. The kinetic nitrogen isotope effect k(14)/k(15) was found to be equal to 1.0056 +/- 0.0011 for 1 and 0.9925 +/- 0.0024 for 2. These results are consistent with a mechanism which involves proton transfer from the OH group to the nitrogen moiety. The recalculated nitrogen kinetic effect for the second step (amine departure) is equal to 1.021 for 1 and 1.008 for 2. On this basis a metaphosphate-like transition state or ''exploded'' S(N)2(P) transition state is proposed for solvolysis of 1. With its less bulky substituent, an earlier transition state in the unimolecular process or a change into the addition-elimination mechanism is considered for phosphoramidate 2.
Solid substrates with free hydroxyl groups are phosphorylated by thermolysing a solution of phosphoramidate of the formula ##STR1## in the presence of the substrate, whereby metaphosphate is generated which phosphorylates the substrate.
Kasparek, Frantisek; Mollin, Jiri, Collection of Czechoslovak Chemical Communications, 1980, vol. 45, # 2, p. 386 - 396
作者:Kasparek, Frantisek、Mollin, Jiri
DOI:——
日期:——
O-Ethyl Phosphoramidic Acids with Sterically Demanding N-Substituents: Useful Precursors of Ethyl Metaphosphate on Thermolysis
作者:Louis D. Quin、Stefan Jankowski
DOI:10.1021/jo00095a013
日期:1994.8
Kinetics of the thermal fragmentation of four N-substituted derivatives of O-ethyl phosphoramidic acids, (EtO-P(O)(NRR')(OH), were examined. When N contained either of the sterically demanding mesityl or 1-adamantyl groups, the reaction followed first-order kinetics, both in the absence and presence of an alcohol trapping reagent. In the former case, the product was a pyrophosphate (RR'N(EtO)(O)P-O-P(O)(OEt)OH). In the latter case, phosphorus was trapped as a dialkyl phosphate. Both reactions are therefore indicated to follow an elimination-addition mechanism, with ethyl metaphosphate as transient intermediate. The pyrophosphate is derived from reaction of the metaphosphate with unreacted phosphoramidic acid. With less bulky substituents (N-phenyl or N,N-diethyl), mixed first- and second-order kinetics were followed in the absence of a trapping agent; some bimolecular interaction of the substrate to form the pyrophosphate product is indicated by the second-order kinetics. Product analyses and quantitative measurements were made with P-31 NMR spectroscopy. From all phosphoramidic acids, the intermediate metaphosphate was effectively trapped by reaction with the OH group on the surface of solid silica gel. The presence of covalently bonded phosphate on the surface was shown by P-31 and Si-29 CP/MAS NMR spectroscopy.
US5334741A
申请人:——
公开号:US5334741A
公开(公告)日:1994-08-02
[EN] PHOSPHORYLATION WITH MONOMERIC METAPHOSPHATES<br/>[FR] PHOSPHORYLATION A L'AIDE DE METAPHOSPHATES MONOMERES
申请人:——
公开号:WO1994002226A1
公开(公告)日:1994-02-03
[EN] Solid substrates with free hydroxyl groups as phosphorylated by thermolysing a solution of phosphoramidate of formula (I), in the presence of the substrate, whereby metaphosphate is generated which phosphorylates the substrate. [FR] Des substrats solides à groupes hydroxyles libres sont phosphorylés par la thermolyse d'une solution de phosphoramidate de la formule (I) en présence du substrat, ce qui produit du métaphosphate qui phosphoryle le substrat.