Ring transformation of 6-methyl-3,4-dihydro-2H-1,3-oxazine-2,4-diones

Ring transformation of 6-methyl-3,4-dihydro-2H-1,3-oxazine-2,4-dione (Ia) and its N-sub-stituted derivatives, such as 3-methyl (Ib), 3-ethyl (Ic), and 3-benzyl (Id) derivatives is described. Reaction of Ia with hydrazine hydrate gave 1-amino-6-methyluracil (II), while Id reacted with hydrazine hydrate to give 3-hydroxy-5-methylpyrazole (III). Reaction of Ia,b,d with ethyl acetoacetate in ethanol in the presence of sodium ethoxide afforded ethyl 3-acetyl-6-hydroxy-4-methyl-2(1H) pyridone-5-carboxylate derivatives (IVa,b,d). On the other hand, reaction of Ib,c,d with ethyl acetoacetate in tetrahydrofuran in the presence of sodium hydride did not give IV, but gave 3-acetyl-1-alkyl-5-(N-alkylcarbamoyl)-6-hydroxy4-methyl-2(1H) pyridone (VIb,c,d). Mechanisms for the formation of compounds IV and VI are discussed.     

Synthesis of chloropyrimidinylmethylenephosphoranes and their wittig reactions with aldehydes

Methylpyrimidines were treated with phosphorus pentachloride in phosphorus oxychloride to give trichloromethylpyrimidines, which reacted with two equivalent amounts of triphenylphosphine to yield chloropyrimidinylmethylenetriphenylphosphoranes as stable ylides in one step. These phosphorus ylides were subjected to the Wittig reaction with a variety of aldehydes to afford chloropyrimidinylolefins.     

Determination of ionic distributions of three sorts of oxygens in a few binary silicate glasses from molar refractivity

Ionic distributions of three sorts of oxygens in glasses in the systems Na₂OSiO₂K₂OSiO₂ and PbOSiO₂ were determined from molar refractivity. The distribution of these oxygen ions in PbOSiO₂ glasses was compared with that determined by the XPS method and with the theoretical calculation based on the athermal mixture model. The present result showed good agreement with that by the XPS method when the PbO content was 70 mol % or over, and showed a discrepancy when the PbO content was less than 70 mol %. It was indicated that a theoretical treatment based on a higher approximation that the athermal mixture model is required in order to enable the comparison with experiments for silica contents higher than 50 mol %.     

An electronically-driven volume transition in CeSi2−xGax

The pseudobinary compounds CeSi_2?xGa_x were prepared, and the lattice parameters and the susceptibilities were measured. At the Si-rich end, 0≦x<0.2, the system behaves as one with a high (～200K) Kondo temperature exhibiting no magnetic order. For 0.5<x≦1.3, the system shows the unit-cell volume 3% larger and orders ferromagnetically around 10K. The α-ThSi₂ structure is retained up to x=1.3, but one observes a two-phase region for 0.2≦x≦0.5, consisting of small- and large-volume phases. This volume transition is magnetically one of the most drastic compared to previously studied Ce-based pseudobinaries.     

rel-(1R,4R,5S)-5-hydroxy-3-oxo-2-azabicyclo[2.2.0]hexane,a stable synthetic equivalent of 4-(2-oxoethyl)azetidin-2-one

The title compound, a synthetic equivalent of 4-(2-oxoethyl)-azetidin-2-one, has been synthesized as a stable crystalline solid either from 4-($\text{t}$-butyldimethylsilyloxy)- or 4-benzyloxy-2-pyridone $\text{via}$ photopyridone formation, catalytic hydrogenation, and deblocking of the protecting group.     

A structural investigation of calcium fluorosilicate glasses

The structure of x CaF₂(1?x)CaOSiO₂ glasses was investigated by X-ray photoelectron, F K_α emission X-ray and infrared absorption spectroscopies and ionic refraction of fluorine. A maximum in F_1s binding energy and a minimum in chemical shift of F K_α X-ray were found in the region of 7–10 mol% CaF₂, indicating that the state of fluorine changes. The ionic refraction of fluorine increased with increasing CaF₂ content up to 7 mol% CaF₂ and was nearly constant for compositions with more than 7 mol% CaF₂. There was practically no change in $\text{Ca}{}_{\mathrm{<mtext>2</mtext><mtext>p</mtext><mtext>(</mtext><mtext>3</mtext><mtext>2</mtext><mtext>)</mtext>}}$ binding energy for compositions with less than 7 mol% CaF₂. These data suggest that the fluorine ion bonds with a silicon predominantly for a CaF₂ content of less than 7 mol% and bonds with a calcium ion for increased CaF₂ content. Further, partial charges of fluorine, calcium and silicon, calculated by the modified Sanderson method could explain the chance of F_1s and $\text{Ca}{}_{\mathrm{<mtext>2</mtext><mtext>p</mtext><mtext>3</mtext><mtext>2</mtext>}}$ binding energies with composition. It is suggested that when the CaF₂ content is more than 7 mol%, the coordination number of fluorine increases and that of calcium decreases with increasing CaF₂ content.     

Photoinduced change in the charge order pattern in the quarter-filled organic conductor (EDO-TTF)2PF6 with a strong electron-phonon interaction

The quasistable state in the photoinduced phase transition for the quasi-one-dimensional quarter-filled organic conductor (EDO-TTF)2PF6 has been examined by ultrafast reflective measurements and time-dependent model calculations incorporating both electron-electron and electron-phonon interactions. The transient optical conductivity spectrum over a wide probe photon-energy range revealed that photoexcitation induced a new type of charge-disproportionate state. Additionally, coherent and incoherent oscillations dependent on probe photon energies were found, as predicted by the calculation.