Junko Ichihara

Sonochemical switching of reaction pathways in slid–liquid two-phase reactions

Ultrasonic irradiation of a mixture of benzyl bromide, potassium cyanide, and alumina in an aromatic solvent yields benzyl cyanide, whereas mechanical agitation gives the Friedel–Crafts type product; sonication changes the main reaction pathway from aromatic electrophilic to aliphatic nucleophilic substitution.

Fluoride-alumina reagents: the active basic species

Abstract Comparison of KF and NaF impregnated on active alumina shows that the formation of strong base by fluoride reaction with alumina cannot totally explain the extremely high reactivity of KF-alumina as a heterogeneous base for catalytic as well as non-catalytic reactions. At least three mechanisms apparently give rise to the high basicity.

The combination of ammonium hydrogen fluoride and aluminium fluoride an efficient solid fluoride source for halofluorination of alkenes

Abstract The combination of ammonium hydrogen fluoride and porous aluminium fluoride (NH 4 HF 2 -AlF 3 ) is a useful solid reagent for introducing fluorine to simple alkenes with N-halosuccinimide under sonication to afford the halofluorinated compounds.

Keggin-type polyacid clusters on apatite: characteristic catalytic activities in solvent-free oxidation

We found that Keggin-type phosphometalates are effective catalysts for solvent-free oxidation with urea–H2O2 by dispersing on fluorapatite solid phase. In the solid phase system the phosphomolybdate (NH4)3PMo12O40 was more effective than the phosphotungstate (NH4)3PW12O40, whereas the latter was much superior to the former in the liquid-phase reaction with aqueous H2O2. In situ formation of novel peroxo-type species from (NH4)3PMo12O40/FAp and urea–H2O2, which may lead to the high catalytic activity in the solid phase system, was observed by 31P solid-state NMR.

Solvent-free epoxidation using a tungstic acid catalyst on fluoroapatite

Abstract Tungstic acid dispersed on fluoroapatite solid phase (H2WO4/FAp) catalyzed the epoxidation of cycloalkenes and allylic alcohols with a solid urea–hydrogen peroxide complex (urea–H2O2) without a solvent.

Catalytic properties of holmiumdecatungstate modified with cetylpyridinium cation [{C5H5N(CH2)15CH3}7H2Ho(III)W10O36; Cetyl-HoW10] for H2O2-oxidation of alcohols and olefins and its working states under an organic-solvent-free condition

Catalytic properties of holmiumdecatungstate modified with cetylpyridinium cations [Cetyl-Ho(III)W10] for H2O2-oxidations of alcohols and olefins were investigated under various organic solvents-aqueous H2O2 biphasic conditions. Generally, secondary alcohols and benzyl alcohols and internal olefins such as cyclooctene were efficiently catalyzed by Cetyl-Ho(III)W10, while primary alcohols and terminal olefins were almost not. The activity for 2-octanol grew much by using a smaller amount of nonpoler solvents such as CHCl3. Especially, in an organic-solvent-free condition as a limited case, Cetyl-Ho(III)W10 was elucidated to be workable as a highly active but quite mild catalyst in comparison with the other heteropolyoxometalates well known. A schematical model on the working states was successfully presented. The present H2O2-Cetyl-Ho(III)W10 catalyst system will be insisted, finally, to be responsible for industrial oxidation processes such as being performed in a non-organic solvent system as environmental concerns.

Catalytic behavior of a series of lanthanide decatungstates [Ln(III)W10O369−; Ln: LaYb] for H2O2-oxidations of alcohols and olefins. Some chemical effects of the 4fn-electron in the lanthanide(III) ion on the catalyses

Abstract The catalytic activities of a series of lanthanide decatungstates [Ln(III)W 10 O 36 9 ; Ln(III)W10, Ln: LaYb] modified with cetyl-pyridinium cations for H 2 O 2 -oxidation of both cyclooctene to epoxycyclooctane and benzyl alcohol to benzaldehyde were investigated in a CHCl 3 -aqueous H 2 O 2 biphasic system. The activity for the former reaction decreased almost linearly along with the contraction of the Ln(III) ion in Ln(III)W10, and on the contrary, that for the latter tended to increase. The activity for the alcohol correlated, additionally, with the physicochemical parameters of LN(III)W10. A chemical effect of the 4f n -electrons in the lanthanide(III) ion on such catalytic behavior will be discussed from a mechanistic viewpoint.

Shape-controlled synthesis of hydroxyapatite from α-tricalcium bis(orthophosphate) in organic-aqueous binary systems

Hydrolyses of α-tricalcium bis(orthophosphate) Ca3(PO4)2 (α-TCP) were carried out in a heterogeneous solvent system (hydrophobic organic solvent-water). The hydroxyapatites (HAp) formed were deficient in calcium (Ca/P = 1.56–1.61, a-axis = 0.9440 nm, c-axis = 0.6880 nm) and contained acid phosphate (and sometimes carbonate depending on the organic solvent used). The HAp was in the form of needles with a length (1–4 μm) that depended on the polarity of the hydrophobic organic solvent. The aspect ratio was highest in 1-octanol with a polarity of ET = 48.3. On the other hand, in a hydrophobic organic solvent system without OH groups such as n-octane (ET = 31.1), HAp formed fine particles that are similar to HAp prepared in a system without an organic solvent. Thus, hydrophobicity and OH groups of organic solvents affect the crystal growth of HAp.

Fluoride ion-promoted reaction of β-tricalcium phosphate to fluoridated hydroxyapatite

Abstract Solvothermal reaction of β-tricalcium phosphate (β-TCP) [Ca 3 (PO 4 ) 2 ] with ammonium fluoride in water-1-octanol biphase proceeds to afford fluoridated hydroxyapatite (FHAp) [Ca 10 (PO 4 ) 6 (OH) 2(1− x ) F 2 x ] quantitatively. It was found that FHAps with various fluoride contents were more easily prepared under mild reaction conditions and that higher crystallinity of FHAp was obtained, compared with the reaction of α-TCP with fluoride ions. The solvolysis reaction of β-TCP did not proceed without fluoride ions, whereas the reaction of α-TCP proceeded with or without fluroide ions. This indicates that the former reaction is promoted by fluoride ions.

Alumina-supported fluoride reagents for organic synthesis: optimisation of reagent preparation and elucidation of the active species

Reagent loading and drying conditions have been compared for alkali metal fluride (MF)–alumina supported reagents, by reaction studies and a series of analytical techniques. The reaction studies indicate that whereas a combination of low MF loadings and highly efficient drying procedures give the best reagents for catalytic reactions, somewhat higher loadings and more moderate drying conditions give the best reagents for non-catalytic reactions. The analytical studies enable some rationalisation of the reaction results as well as providing important clues concerning the nature of the active-basic species. The formation of OH– on the reagent surface cannot be entirely responsible for the high basicity of the reagents and it seems that co-ordinately unsaturated F– ions on the reagent surface play an important role in the behaviour of the reagents. High MF loadings and high drying temperatures result in significant structural damage to the reagents with resulting loss in activity.