Geometrical H/D isotope effect on hydrogen bonds in charged water clusters

To investigate the proton/deuteron geometrical isotope effect of positively and negatively charged water complexes, H5O2+ and H3O2-, we have carried out accurate ab initio path integral simulations considering the electron correlation effect. It has been found that the isotope effect on the hydrogen bond is different between these two species in that the oxygen separation becomes shorter in H5O2+ while longer in H3O2- by deuteron substitution. This behavior is ascribed to the change in the quantum effect of hydrogen bonds whether the shared hydrogen is on a single or double well potential surface.     

Phase equilibrium in the system Y-Fe-O at 1100°C

Phase equilibrium was established in the Y-Fe-O system at 1100°C by varying the oxygen partial pressure from −log(P_O2/atm)=15.00 to 0, allowing construction of a phase diagram at 1100°C for the system Y₂O₃-Fe-Fe₂O₃. In the system, two ternary compounds, YFeO₃ and Y₃Fe₅O₁₂, were stable and had nonstoichiometric composition, whereas YFe₂O₄ was not found to be stable. The present result was different from that of previous studies at 1200°C, in which YFe₂O₄ was stable, along with the above two ternary compounds. Lattice constants of YFeO₃ and Y₃Fe₅O₁₂, prepared in air by a quenching method, were determined and compared with previous values, and showed close agreement. The standard Gibbs energy changes of the reactions in the Fe-O system, Fe+1/2O₂=FeO, 3FeO+1/2O₂=Fe₃O₄, and 2/3Fe₃O₄+1/6O₂=Fe₂O₃, were determined, and the obtained values were compared with the previous values. The standard Gibbs energy changes of the reactions, Fe+1/2Y₂O₃+3/4O₂=YFeO₃, and 3YFeO₃+2/3Fe₃O₄+1/6O₂=Y₃Fe₅O₁₂, were calculated from the oxygen partial pressures in equilibrium.     

Novel Catalytic CO(2) Incorporation Reaction: Nickel-Catalyzed Regio- and Stereoselective Ring-Closing Carboxylation of Bis-1,3-dienes

Novel nickel-catalyzed carboxylation of bis-1,3-dienes using carbon dioxide (CO2) was investigated. In the presence of catalytic amounts of Ni(acac)2 and PPh3, various bis-1,3-dienes smoothly reacted with CO2 and an organozinc reagent (Et2Zn, Me2Zn, or Ph2Zn) under mild conditions. This catalytic carboxylation process was accompanied by carbocyclization of bis-1,3-diene followed by alkylation by an organozinc reagent to afford cyclic carboxylic acid derivatives in high yields with high regio- and stereoselectivities.     

Total synthesis of (-)-kaitocephalin

[reaction: see text] Total synthesis of the potent AMPA/KA receptor antagonist (-)-kaitocephalin (1) and its three diastereomers has been accomplished. The synthesis features strictly substrate-controlled operations to alpha-formylglutamate 3 starting with alpha-hydroxymethylglutamate 4. The requisite 2R,3S,7R-stereocenters were efficiently constructed by manipulation of stereoselective reactions: dihydroxylation of 7 followed by azide substitution of the corresponding thionocarbonate 10 and Cu-mediated allylation of an acyliminium ion 21. All of the protecting groups in 26 were removed simultaneously by AlCl3/Me2S to give 1.     

Photochemistry of 4-pyrimidinones in aqueous solution. Isolation of reversible photohydrates

Both the irradiation of 4-pyrimidinones ($\text{la-c}$) and the reaction of the isolated Dewar 4-pyrimidinones ($\text{2a-c}$) in aqueous solution gave the corresponding photohydrates ($\text{3a-c}$) which reverted spontaneously to the starting $\text{la-c}$ in the dark reaction. The photohydrates were isolated in crystalline form and their physical properties were determined.     

Phosphazene Base tBu-P4 Catalyzed Methoxy–Alkoxy Exchange Reaction on (Hetero)Arenes

The organic superbase tBu-P4 catalyzes methoxy-alkoxy exchange reactions on (hetero)arenes with alcohols. The catalytic reaction proceeded efficiently with electron-deficient methoxy(hetero)arenes as well as with a variety of alcohols, including 3-amino-1-propanol, β-citronellol, menthol, and cholesterol. An intramolecular version of this reaction furnished six- and seven-membered ring compounds.