Skeletal reorganization of enynes into 1-vinylcycloalkenes in ionic liquids

The skeletal reorganization of enynes catalyzed by transition metal chlorides, such as PtCl(2), [RuCl(2)(CO)(3)](2), [RhCl(CO)(2)](2), and AuCl(3), in ionic liquids proceeds under milder conditions (at lower reaction temperatures and for shorter reaction times) than those needed for ordinary solvents. The products produced by the skeletal reorganization of enynes were easily removed from the catalyst by a simple extraction with Et(2)O or distillation. The PtCl(2) can be reused up to five times.     

Photoinduced ene-reaction of 9-methylene-9,10-dihydrophenanthrene with alkenes

Irradiation of 9-methylene-9,10-dihydrophenanthrene (1) in the presence of 1,1-diphenylethene or styrene in benzene afforded ene-reaction adduct in good yield. In the absence of arylalkenes, the dimerized product of 1, 9-[2-(9-phenanthryl)ethyl]-9,10-dihydrophenanthrene, and 9-methylphenanthrene were obtained as major products.     

A new ketone synthesis by palladium-catalyzed cross-coupling reactions of esters with organoboron compounds

[reaction: see text] The palladium-catalyzed coupling reaction of 2-pyridyl esters with organoboron compounds is described. The reaction is compatible with various functional groups and proceeds under mild reaction conditions. The coordination of the nitrogen atom to Pd is a key step for efficient reaction.     

Quantum versus Jahn-Teller orbital physics in YVO3 and LaVO3

We argue that the large Jahn-Teller (JT) distortions in YVO3 and LaVO3 should suppress the quantum orbital fluctuation. The unusual magnetic properties can be well explained based on local density approximation + Hubbard U calculations using experimental structures, in terms of the JT orbital. The observed splitting of the spin-wave dispersions for YVO3 in a C-type antiferromagnetic state is attributed to the inequivalent VO2 layers in the crystal structure, instead of the "orbital-Peierls state." Alternative stacking of ab-plane exchange couplings produces the c-axis spin-wave splitting; thus, the spin system is highly three dimensional rather than quasi-one-dimensional. Similar splitting is also predicted for LaVO3, although it is weak.     

Topological nature of polarization and charge pumping in ferroelectrics

Electric polarization in insulators is represented by the transferred charge through a shift of the Bloch wave functions induced by an adiabatic change of external parameters Q-->. It is found that this covalent/quantum contribution is determined nonlocally by the topological structure in the Q--> space. The condition for the charge pumping for a cyclic change of Q--> is also obtained. Applications of this picture to various organic ferroelectrics and BaTiO3 are discussed.     

Coexistence of solvated electrons and solvent valence anions in negatively charged acetonitrile clusters, (CH3CN)-n(n=10-100)

Anion photoelectron spectroscopy of acetonitrile cluster anions, (CH3CN)(-)(n) (n=10-100), successfully demonstrates the competitive coexistence of two different anionic species: a solvated electron and a solvent-bound valence anion. The distinctly different nature of these anions is revealed by hole-burning-type photoelectron spectroscopy and relative photodetachment cross section measurements. This unusual coexistence is attributed to the closely lying nature of their anionic states at just the number of solvent molecules sufficient to almost complete the first solvation layer.     

Competing orders and disorder-induced insulator to metal transition in manganites

Effects of disorder on the two competing phases, i.e., the ferromagnetic metal and the commensurate charge/lattice ordered insulator, are studied by Monte Carlo simulation. The disorder suppresses the charge/lattice ordering more strongly than the ferromagnetic order, driving the commensurate insulator to the ferromagnetic metal near the phase boundary in the pure case. Above the ferromagnetic transition temperature, on the contrary, the disorder makes the system more insulating, which might cause an enhanced colossal magnetoresistance as observed in the half-doped or Cr-substituted manganites. No indication of the percolation or the cluster formation is found, and there remains the charge/lattice fluctuations instead which are enhanced toward the transition temperature.     

Long-lived charge-separated state leading to DNA damage through hole transfer

The hole transfer causes the long-lived charge-separated state in DNA during the photosensitized one-electron oxidation of DNA. The combination of the transient absorption measurement and DNA damage quantification by HPLC clearly demonstrated that the yield of the DNA damage correlates well with the lifetime of the charge-separated state.     

Practical synthesis of a 1beta-methylcarbapenem, J-111,225, using 4-mercapto-2-[4-(N-methylaminomethyl)phenyl]pyrrolidine as a precursor

An effective and practical procedure for the synthesis of J-111,225 (1), a new 1beta-methylcarbapenem, was developed using 4-mercapto-2-14-(N-methylaminomethyl)phenyl]pyrrolidine (2a) as a precursor. The coupling reaction of 2a with p-nitrobenzyl (PNB)-protected 1beta-methylcarbapenem enolphosphate 3a and successive removal of PNB group afforded J-111,225 (1) in significantly increased yield compared to the ordinary procedure using a C-2 side-chain thiol with amino-protective groups.