Selective Formation of Spinel Iron Oxide in Thin Films by Complexing Agent-Assisted Sol-Gel Processing

The structure of iron oxide was controlled by regulating the hydrolytic polymerization of aquo iron complexes with organic polydentate ligands such as diols. Iron oxides were prepared by calcining the precursor polymers obtained from iron nitrate nonahydrate and diols. When the diols were 1,2-pentanediol, 1,2-hexanediol and 1,2-octanediol, α-Fe₂O₃ with corundum structure appeared exclusively or as the main crystalline phase, in spite of the amount of diol used and the calcination temperature. In the case of 1,2-decanediol and 1,2-dodecanediol, when five moles of the diols were used to one mole of iron nitrate and the calcination temperatures were below 400°C, ψ-Fe₂O₃ with spinel structure appeared as the main phase and, when less than five moles of the diols were used, α-Fe₂O₃ appeared exclusively or as the main phase, irrespective of the calcination temperature. This tendency was also observed in thin films. Thus, a transparent magnetic film composed of γ-Fe₂O₃ could be prepared by applying a benzene solution of the iron polymer, obtained with 5 equivalents of 1,2-decanediol, on quartz and calcining the gel film at 350°C.     

Optically active 1,2-bis(1-arylhydroxymethyl) ferrocene: a new, efficient chiral ligand for scandium-catalyzed asymmetric Diels-Alder reaction

[reaction: see text] The Sc(OTf)3/FERRODIOL (2) complex was prepared at -78 degrees C in CH2Cl2 in the presence of 2,6-lutidine and MS 4A. The chiral scandium Lewis acid-catalyzed asymmetric Diels-Alder reaction of cyclopentadiene (3) with 3-acyloxazolidin-2-ones (4) effectively produced the adduct (5) in a high yield with good selectivity, i.e., endo/exo = 90:10 up to 91% ee (endo).     

Ultra-stable Ni catalysts for methane reforming by carbon dioxide

Methane reforming by carbon dioxide has been studied over ultra-stable Ni catalysts. The catalyst was characterized by XRD, IR and TEM and temperature programmed hydrogenation. The nickel–magnesia solid solution catalyst containing low nickel has shown excellent stability (>3000 h) and no carbon deposition in the methane reforming by carbon dioxide. It was also found that the small nickel metal particle interaction with support surface is effective for the inhibition of carbon formation.     

Separation of Leucas aspera,a medicinal plant of Bangladesh,guided by prostaglandin inhibitory and antioxidant activities

According to the traditional usage of the plant for antiinflammation and analgesia, Leucas aspera was tested for its prostaglandin (PG) inhibitory and antioxidant activities. The extract showed both activities, i.e., inhibition at 3 x 10(-4) g/ml against PGE(1)- and PGE(2)-induced contractions in guinea pig ileum and a 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging effect. The separation guided by the activities in these dual assay methods provided eight lignans and four flavonoids, LA-1- -12, among which LA-1- -7 and LA-10- -12 were identified as nectandrin B, meso-dihydroguaiaretic acid, macelignan, acacetin, apigenin 7-O-[6"-O-(p-coumaroyl)-beta-D-glucoside], chrysoeriol, apigenin, erythro-2-(4-allyl-2, 6-dimethoxyphenoxy)-1-(4-hydroxy-3-methoxyphenyl)propan-1-ol, myristargenol B, and machilin C, respectively. LA-8 was determined to be (-)-chicanine, the new antipode of the (+) compound, by spectroscopic methods including CD and ORD. Chiral-HPLC analysis of LA-9 showed that it was a mixture of two enantiomers, (7R, 8R)- and (7S, 8S)-licarin A. All of these components were first isolated from L. aspera. PG inhibition was observed in LA-1, LA-2, and LA-5, and antioxidant activity in LA-1- -3 and LA-8- -12.     

Theoretical study of activation of oxirane by bidentate acids

The reaction of oxirane with amines in the presence of some bidentate and monodentate Bronsted acids has been studied theoretically by taking some simplified reaction models. Acids have been shown to serve as temporary reservoirs of electronic charge during the reaction to strengthen the nucleophilicity of the substrate. The shift of electronic charges and enhancement of the nucleophilicity of oxirane have been represented by means of paired interaction orbitals and projected reactive orbitals. The reason the transition state appears at an earlier stage in the reaction catalyzed by 1,8-biphenylenediol relative to the reactions catalyzed by monodentate phenols and alcohols has been clarified.     

The catalytic hydrogenolysis of 1-phenylbicyclo[4.1.0]heptane and the corresponding azidirine and epoxide

The hydrogenolysisof 1-phenylbicyclo[4.1.0]heptane (1a), cis-1-phenyl-2-methylbicyclo[4.1.0]heptane (1b), 1-phenyl-7-azabicyclo[4.1.0]heptane (2) and 1-phenyl-7-oxabicyclo[4.1.0]heptane (3) was studied using Ni, Pd, Rh and Pt as catalysts. The hydrogenolysis of the C₁C₇ bond of 1a and 1b led to the selective formation of trans-1-phenyl-2-methylcyclohexane (4a) with retention of configuration. Compound 1a gave not only 4a but also phenylcycloheptane (6a), which is the product of C₁C₆ bond fission, and the ratio of 6a to 4a increased in the sequence: Ni ? Pd, Rh < Pt. No C₁C₆ bond fission was observed in the hydrogenolysis of 1b. These results can be explained by a mechanism involving the formation of the π-benzyl complex.trans-2-Phenylcyclohexylamine (8) was obtained stereoselectively in the hydrogenolysis of 2 over Raney Ni. This selective formation can be ascribed to the competition of “SN i” and “radical” processes. The Pd catalysed hydrogenolysis gave cis-2-phenylcyclohexylamine (9) as the main product, while the presence of sodium hydroxide promoted the formation of 8.Raney Ni catalysed hydrogenolysis of 3 yielded a mixture of phenylcyclohexane (13) and 2-phenylcyclohexanols (10 and 11). trans-2-Phenylcyclohexanol (10) was the dominant isomer; the hydrogenolysis resulted in the predominant configurational retention. Compound 13 was confirmed to be produced via 1-phenylcyclohexene (12). This deoxygenation may be explained by a mechanism involving the radical cleavage reaction of 3. The presence of sodium hydroxide led to the formation of cis-2-phenylcyclohexanol (11). The Pd catalysed hydrogenolysis also gave mainly 11.The difference in behaviour of cyclopropane, azidirine and epoxide we ascribe to the differences in the affinity for the catalyst and differences in the electronegativity between C, N and O atoms.     

K-Mo基催化剂的表面酸性与其合成醇选择性

对500℃和800℃焙烧制得的氧化态K－MoO3／γ－AlO3，K－MoO3／SiO2及非负载K－Mo催化剂进行硫化后，测试其合成醇活性．结果表明500℃焙烧制得的负载型催化剂显示较高的合成低碳烃活性和较低的合成低磷醇选择性，经800℃焙烧后，合成低磷醇的选择性大幅度提高．500℃焙烧的非负载K－Mo催化剂显示较高的合成醇选择性，经800℃焙烧后，促碳醇的选择性保持不变．用氨的吸附及TPD方法测定了各样品的酸性，并与催化剂活性对照，发现催化剂酸性越强，酸量越大，则其合成醇选择性越低．催化剂上的乙醇分解实验证实，催化剂的酸量大小与它的醇分解活性成正变关系，这些结果说明催化剂酸性对其合成醇性能有直接的影响．