Kenichi Komura

ZrOCl2·8H2O catalysts for the esterification of long chain aliphatic carboxylic acids and alcohols. The enhancement of catalytic performance by supporting on ordered mesoporous silica

ZrOCl2·8H2O is an efficient catalyst for the esterification of long chain carboxylic acids with long chain primary and secondary alcohols. Supporting ZrOCl2·8H2O on ordered mesoporous silica enhances the catalytic activity of the esterification. The esters of C10–C18 normal acid and alcohol are obtained in high yield by supported ZrOCl2·8H2O on MCM-41 although the yield of the esters decreases with the chain length of acids and alcohols. The esterification of less reactive branched acids and secondary alcohols gives excellent to good yield of the corresponding esters over supported catalysts. Zirconium cation cluster [Zr4(OH)8(H2O)16]8+ is suggested as the catalytic active species. The enhancement of catalytic performance by supporting on MCM-41 is due to increased contact between substrate and catalyst because the cation cluster is highly dispersed over MCM-41 with high surface area. The hydrophobic properties of mesoporous silica accelerate the removal of water during the esterification by controlling hydrated water in the cluster. The catalyst is recyclable without significant loss of activity.

Antitermite Activities of Coumarin Derivatives and Scopoletin from Protium javanicum Burm. f.

The antitermite (termiticidal and antifeedant) activity of Protium javanicum Burm. f. extract was investigated. The ethyl acetate fraction was active. Scopoletin (1), quercetin, and stigmasterol were isolated by bioassay-guided fractionation. Scopoletin had the highest activity among the three compounds. In order to investigate the structure-activity relationship (SAR) of the methoxy and hydroxy groups at the C-6 and C-7 positions of the coumarin skeleton, we synthesized several coumarin derivatives whose chemical structures are similar to scopoletin. Scopoletin exhibited the strongest termiticidal activity among the 10 compounds tested, followed by 6-methoxycoumarin (3), 6-hydroxycoumarin (7), and umbelliferone (8). All compounds except coumarin (9) showed antifeedant activity.

Mesoporous silica MCM-41 as a highly active, recoverable and reusable catalyst for direct amidation of fatty acids and long-chain amines

Direct amidation of fatty acids with long-chain amines was successfully performed by mesoporous silica MCM-41, which showed the highest catalytic activity among other used homo- and heterogeneous catalysts. It was found that MCM-41 can be easily recovered from the reaction mixture followed by simple calcination treatment and reused without loss of its catalytic activity.

H-ZSM-5 modified with lanthanum and cerium oxides in shape-selective ethylation of ethylbenzene. The deactivation of external acid sites and the control of pore entrance

The ethylation of ethylbenzene (EB) was examined over H-ZSM-5 modified with La 2 O 3 and CeO 2 . The selectivities for p -diethylbenzene ( p -DEB) were enhanced by the modification with these oxides. The enhancement of the selectivities for p -DEB over these oxides is due to the prevention of the isomerization of p -DEB by the deactivation at external acid sites. The para -selectivity for H-ZSM-5 modified with La 2 O 3 is enhanced due to the reactant selectivity by preferential diffusion of p -DEB from the zeolite by narrowing of its pore entrance in addition to the deactivation of external acid sites.

Asymmetric Synthesis of (αR)-Polyfluoroalkylated Prolinols Based on the Perfluoroalkyl-Induced Highly Stereoselective Reduction of Perfluoroalkyl N-Boc-pyrrolidyl Ketones

Reduction of the obtained chiral (S)- tert-butyl 2-(perfluoroalkanoyl)pyrrolidine-1-carboxylate with sodium borohydride or lithium aluminum hydride proceeded smoothly to give the corresponding (S)- tert-butyl 2-((R)-perfluoro-1-hydroxyalkyl)pyrrolidine-1-carboxylate in yields of 73-97% with excellent diastereoselectivities (up to >98% de), compared with the reduction of nonfluorinated (S)-tert-butyl 2-pentanoylpyrrolidine-1-carboxylate.

The isopropylation of biphenyl over H-mordenite: roles of 3- and 4-isopropylbiphenyls

The isopropylation of biphenyl (BP) and 3- and 4-isopropylbiphenyls (3- and 4-IPBPs) was examined over H-mordenites (MOR) to elucidate the mechanism of shape-selective formation of 4,4′-diisopropylbiphenyl (4,4′-DIPB). The isopropylation of BP occurred predominantly to form 4-isopropylbiphenyl (4-IPBP) from BP and 4,4′-DIPB from 4-IPBP. However, 3-IPBP, a minor isomer from BP, cannot participate effectively in the formation of 3,4′-DIPB due to steric restriction of its isopropyl moiety with MOR channels. Selective formation of 4,4′-DIPB was observed at low to moderate temperatures: 225–275 °C. However, the selectivities for 4,4′-DIPB were decreased at high temperatures, 300–350 °C under propene pressure, 0.8MPa, by the isomerization of 4,4′-DIPB at external acid sites. The isomerization of 4,4′-DIPB occurred under low propene pressure even at 250 °C. The roles of 3- and 4-IPBPs in the formation of DIPB isomers were examined in the isopropylation of their mixtures. 4-IPBP was consumed much faster than 3-IPBP in all cases examined. 4-IPBP was an exclusive precursor to DIPB isomers, particularly 4,4′-DIPB. 4,4′-DIPB was also found as a predominant isomer in encapsulated products at all conditions examined. These results show that 4-IPBP can preferentially establish active transition state with propene and acid site in MOR channels, resulting in selective formation of 4,4′-DIPB. It is concluded that the isopropylation of BP over MOR occurs through reactant selectivity mechanism and restricted transition state mechanism, but not through product selectivity mechanism.

Na-Y zeolite as a versatile heterogeneous catalyst for the hydroamination of methyl acrylate with amines

Hydroamination of methyl acrylate with various aromatic, aliphatic, cyclic and heterocyclic amines was examined over Na-Y zeolite as a solid catalyst. Among the typical zeolites, Na-Y zeolite effectively catalyzed the reaction to give the corresponding β-amino acid esters in moderate to excellent yields. The catalytic activity was strongly affected by nature of amine. The reactions using recovered catalyst also occurred without significant decrease in the catalytic activity during four recycles. The regeneration of used Na-Y zeolite can be performed by the calcination in air stream.

Synthesis, crystal structure and characterization of novel open framework CHA-type aluminophosphate involving a chiral diamine

A highly crystalline new precursor of CHA-type zeolite AlPO4-34 was obtained by using an aluminophosphate gel with a chiral diamine [(S)-(+)-1-(2-pyrrolidinylmethyl)pyrrolidine; C9H18N2] as an organic structure directing agent under hydrothermal synthesis conditions. This precursor (called GAM-1) was changed into the zeolite AlPO4-34 which had a high porosity (the Brunauer-Emmett-Teller (BET) surface area is approximately 700 m3 g-1) using calcination. The GAM-1 obtained was characterized by various measurements, e.g., powder X-ray diffraction, scanning electron microscopy, and solid-state nuclear magnetic resonance spectroscopy, and so on. Structure determination from powder diffraction data revealed that the new precursor GAM-1 has triclinic symmetry [space group P1[combining macron], a = 9.16535(11) Å, b = 9.23042(11) Å, c = 9.29228(11) Å, α = 79.8243(7)°, β = 87.4593(7)°, γ = 86.5365(7)°] and the chemical formula was estimated to be: |Al6P6O24H2F2|(C9H18N2)·2.5(H2O). It also revealed that a two edge sharing AlO4F2 octahedron with an [triple bond, length as m-dash]Al-F-Al[triple bond, length as m-dash] bridge was included in the framework. GAM-1 was transformed into AlPO4-34 with rhombohedral symmetry (R3[combining macron]) by elevating temperature to over 400 °C. At high temperatures, AlO4F2 octahedron connectivity was changed into an AlO4 tetrahedron. The crystal structure of the dehydrated AlPO4-34 changed back to a triclinic symmetry (P1) model again after rehydration in the atmosphere.

Synthesis of Cyclohexylbenzene by Hydroalkylation of Benzene over Pd/Hβ Binary Catalyst

Abstract The Pd/Hβ binary catalyst was prepared by the impregnation method and was used for the hydroalkylation of benzene to cyclohexylbenzene. The effects of reaction temperature, reaction time, hydrogen pressure, Hβ acidity, and metal loading were investigated. The results indicated that the conversion of benzene and the selectivity for cyclohexylbenzene approached 24.3% and 88.0%, respectively, under the conditions of 2.5 MPa H2, 200°C, and 3 h. The preferable balance between metal active sites and acidic sites in the catalyst was the key to the hydroalkylation of benzene. The mechanism of the reaction was discussed.

Multi-Valent Metal Salt Hydrates as Catalysts for the Esterification of Fatty Acids and Alcohols

Some typical multi-valent metal salt hydrates, such as chloride, nitrate, sulfate, and acetate of Fe3+, Al3+, Ga3+, In3+, ZrO2+, HfO2+, Zn2+, Co2+, Ni2+, Mn3+, Cr3+, and Cu2+ have catalytic activities for the esterification of saturated and unsaturated fatty acids and alcohols. Supporting these metal salt hydrates on ordered mesoporous silica such as MCM-41 enhanced the catalytic activity of the esterification. The esters of C10-C18 normal acid and alcohol were obtained in high yield by some of supported metal salt hydrates on MCM-41; however, the yield of the esters decreased with their chain length of acids and alcohols although the activities depended on type of metal salt hydrates. The catalyst is recyclable although some loss of activity was observed.