Reaction of bis(2,4-dinitrophenyl) phosphate with hydrazine and hydrogen peroxide. Comparison of O- and N- phosphorylation

Nonionic hydrazine reacts with anionic bis(2,4-dinitrophenyl) phosphate (BDNPP), giving 2,4-dinitrophenyl hydrazine and dianionic 2,4-dinitrophenyl phosphate by an S(N)2(Ar) reaction, and at the phosphoryl center, giving 2,4-dinitrophenoxide ion and a transient phosphorylated hydrazine that rearranges intramolecularly to N-(2,4-dinitrophenyl)-N-phosphonohydrazine. Approximately 58% of the reaction at pD = 10 occurs by N-phosphorylation, as shown by (31)P NMR spectroscopy. Reaction of HO(2)(-) is wholly at phosphorus, and the intermediate peroxophosphate reacts intramolecularly, displacing a second 2,4-dinitrophenoxide ion, or with H(2)O(2), giving 2,4-dinitrophenyl phosphate and O(2). Rate constants of O- and N-phosphorylation in reactions at phosphorus of NH(2)NH(2), HO(2)(-), and NH(2)OH and its methyl derivatives follow Bronsted relationships with similar slopes, but plots differ for oxygen and nitrogen nucleophiles. The reaction with NH(2)NH(2) has been probed by using both NMR spectroscopy and electrospray ionization mass and tandem mass spectrometry, with the novel interception of key reaction intermediates in the course of reaction.     

Mechanism of intramolecular catalysis in the hydrolysis of alkyl monoesters of 1,8-naphthalic acid

Hydrolysis of alkyl 1,8-naphthalic acid monoesters 1a-d is subject to highly efficient intramolecular nucleophilic catalysis by the neighboring COOH group. The reactivity for the COOH reaction depends on the leaving group pK(a), with values of β(LG) of -0.50, consistent with a mechanism involving rate determining breakdown of tetrahedral addition intermediates. The release of the steric strain of the peri-substitiuents in the highly reactive alkyl 1,8-naphthalic acid monoesters is fundamental to understand the observed special reactivity in this intramolecular reaction. DFT calculations show how the proton transfers involved in the cleavage of the neutral ester can be catalyzed by solvent water, thus facilitating the departure of poor alkoxide leaving groups.     

Ionic quenching of naphthalene fluorescence in sodium dodecyl sulfate micelles

Micellar effects on luminescense of organic compounds or probes are well established, and here we show that quenching is highly favored in aqueous sodium dodecyl sulfate (SDS) micelles, which concentrate a naphthalene probe and cations of lanthanides, transition metals, and noble metals. Interactions have been studied by steady state and time-resolved fluorescence in examining the fluorescence suppression of naphthalene by metal ions in anionic SDS micelles. The quenching is collisional and correlated with the unit charge and the reduction potential of the metal ion. The rate constants, calculated in terms of local metal ion concentrations, are close to the diffusion control limit in the interior of SDS micelles, where the microscopic viscosity decreases the transfer rate, following the Stokes-Einstein relation.     

1, 1, 1-Trichloropropanone: A Mild,Selective Acetylating Agent

The use of the title compound in the acetylation of primary and secondary amines i s described.     

Dephosphorylation reactions with deferoxamine, a potential chemical nuclease

We report a detailed kinetic and mechanistic study of the reaction of a widely used therapeutic agent, deferoxamine (DFO), which contains three nucleophilic hydroxamate groups, with the model phosphate diester bis-2,4-dinitrophenylphosphate BDNPP. We clarify the mechanism by detecting important phosphorylated intermediates in the model reaction and show that the mechanism can be extended to the reaction with DNA. The effectiveness of DFO in cleaving DNA was examined over a range of pH in the absence and presence of a biologically available metal (Zn(2+)). The results inform and complement ongoing studies involving DFO, which can act as a powerful nucleophile toward DNA and other targets susceptible to nucleophilic attack.     

Phosphorylimidazole derivatives: potentially biosignaling molecules

The phosphorylation of imidazole by two activated phosphate diesters and a triester gives phosphorylimidazole derivatives that are stable enough in aqueous solution to be observed and identified by ESI-MS/MS and NMR. Half-lives ranging from hours to days (in the case of the monoethyl ester) show that it is possible to design molecules with variable half-lives with potential to be used for biological intervention experiments as possible inhibitors of biosignaling processes or as haptens for the generation of antibodies.