Divalent metal ion catalyzed reactions of acyl phosphates

Abstract

The reaction of atomic bromine with several arylcyclopropanes has been investigated. For systems where the aryl moiety is phenyl or a-or yS-naphthyl, the expected SH2 pathway leading to cyclopropane ring cleavage is observed. In the case of 9-cyclopropylanthracene, however, an unprecedented hydrogen atom abstraction reaction is observed. These observations are explicable on stereoelectronic grounds. For the 9-anthryl system, the lowest energy perpendicular conformation finds the -C-H bond aligned with the -system, and consequently hydrogen abstraction is facile. In this conformation, the a-C-C bonds are deactivated toward bromine atom attack. For phenyl-and /3-naphthylcyclopropane, the bisected conformation is preferred and ring opening predominates. The ground-state conformation of -cyclopropylnaphthalene is unique in that it is midway between bisected and perpendicular. Although cyclopropane ring opening is the only detected process, quantitative data are presented which demonstrate that the rate of this process is diminished because of unfavorable stereoelectronic factors.Analysis of this reaction system with the Curtin-Hammett principle leads to a general statement of the requirements for a-hydrogen abstraction from cyclopropylarenes by bromine atom.

Coordinative Amphiphiles as Tunable siRNA Transporters

“…Several divalent metal complexes have been reported for their ability to hydrolyze phosphate esters. ,− To investigate activities of compounds for hydrolysis of siRNAs, we simply incubated them with siRNAs at the physiological condition (37 °C, pH 7.4) (Figure S6). As other divalent metal complexes, Zn/DPAs possibly hydrolyzed phosphodiester linkages of siRNAs.…”

Alkali‐Metal Ion Catalysis and Inhibition in SNAr Displacement: Relative Stabilization of Ground State and Transition State Determines Catalysis and Inhibition in SNAr Reactivity

“…[1][2][3][4][5][6][7][8][9] Since Lewis acidity increases with increasing charge density of metal ions, studies have focused mostly on reactions involving multivalent metal ions (e.g., La 3 + , Eu 3 + , Co 3 + , Zn 2 + , Cu 2 + , etc.). [1][2][3][4][5][6][7][8][9] Since Lewis acidity increases with increasing charge density of metal ions, studies have focused mostly on reactions involving multivalent metal ions (e.g., La 3 + , Eu 3 + , Co 3 + , Zn 2 + , Cu 2 + , etc.).…”

“…Metal ions (as Lewis acids) have often been reported to catalyze nucleophilic substitution reactions of esters bearing various electrophilic centers. [1][2][3][4][5][6][7][8][9] Since Lewis acidity increases with increasing charge density of metal ions, studies have focused mostly on reactions involving multivalent metal ions (e.g., La 3 + , Eu 3 + , Co 3 + , Zn 2 + , Cu 2 + , etc.). [1][2][3][4][5] It is well known that alkalimetal ions are ubiquitous in nature and play important roles in biological processes (e.g., a Na + pump to maintain high K + and low Na + concentrations in mammalian cells).…”

Metal Ion Catalysis in the Hydrolysis of Esters of 2-Hydroxy-1,10-phenanthroline: The Effects of Metal Ions on Intramolecular Carboxyl Group Participation

“…Rate enhancements in metal ionpromoted OH Ϫ reactions of acyl derivatives are very large (19,20,23,(25)(26)(27)(28)(29)(30)(31), ranging up to 10 8 -fold with Cu 2ϩ (10 10 -fold with an acyl phosphate) (31). In contrast, a significant effect (10 2 -to 10 4 -fold) has only been observed in metal ion-promoted carboxyl nucleophilic reactions in cases where the leaving group is an aliphatic alcohol and the metal ion can complex the leaving group oxygen in the transition state (24,25).…”

“…The 1,10-phenanthrolyl ligand has advantages for the study of metal ion effects, among which is the very strong complexing ability of the phenanthroline nitrogens (23,(31)(32)(33)(34). The position of the metal ion in a 1:1 complex can often be specified.…”