Yuki Taniguchi

Palladium(II)-catalyzed carboxylation of benzene and other aromatic compounds with carbon monoxide under very mild conditions

Abstract Aromatic compounds such as benzene, toluene, chlorobenzene, anisole, and naphthalene were carboxylated by palladium(II) acetate catalyst with carbon monoxide in the presence of potassium peroxodisulfate in trifluoroacetic acid (TFA) at room temperature under atmospheric pressure. The aromatic carboxylic acids were formed in good yields; for example, the carboxylation of benzene with carbon monoxide proceeds quantitatively under the optimal conditions.

Halogenation and butylation of diamond surfaces by reactions in organic solvents

Abstract Hydrogenated diamond powder was chlorinated by treatment with sulfuryl chloride in chloroform at 50 °C. The disappearance of Cue5f8H stretching peaks showed that most of the hydrogen was substituted by chlorine in this procedure. The chlorinated diamond was then reacted with butyllithium dissolved in tetrahydrofuran at 30 °C. Butyl groups incorporated onto the diamond surface were decomposed by flash pyrolysis at temperatures between 255 and 1040 °C, and all organic fragments were recovered. The fraction of butylated surface carbons to total surface carbons was calculated to be 0.055.

An efficient partial oxidation of methane in trifluoroacetic acid using vanadium-containing heteropolyacid catalysts

Abstract The new catalytic system has been examined for the partial oxidation of methane in liquid phase. It was found that the vanadium containing heteropolyacids/K 2 S 2 O 8 /(CF 3 CO) 2 O/CF 3 COOH catalyst system converts methane to methyl trifluoroacetate along with a trace amount of methyl acetate in a 95% yield based on methane. The activation energy of the reaction was estimated to be 27.9 kcal mol −1 .

Palladium-catalyzed acetic acid synthesis from methane and carbon dioxide

Publisher Summary Carbon dioxide is one of the natural C1-resources that is being watched with keenest interest as a substitute of toxic CO in the C1-chemistry. The chemical fixation of CO2, a process which is appealing for both scientific and environmental reasons since methane and CO2 are well known as the greenhouse gases, is an important task for the human being though it is difficult because of low reactivity of CO2. Alkane activation/functionalization by transition metals under mild conditions is also one of the most challenging problems in modern chemistry since small alkanes including methane, ethane, and propane are the most abundant natural resources of hydrocarbons.

Direct carboxylation reaction of methane with CO by a Yb(OAc)3/Mn(OAc)2/NaClO/H2O catalytic system under very mild conditions

A new method of synthesis of acetic acid in water has been developed from the carboxylation of methane with carbon monoxide using lanthanide catalysts. Ytterbium(III) acetate has been found to be the most active catalyst among the compounds of the lanthanide series in the carboxylation reaction of methane with carbon monoxide. Sodium hypochlorite or hydrogen peroxide was used as the oxidant in this reaction. Sodium hypochlorite exhibited more favorable activity than hydrogen peroxide in the reaction. The catalytic activity was improved by the addition of transition-metal salts such as manganese(II) acetate. The best result has been found at a ratio of manganese(II) acetate to ytterbium(III) acetate of 1:10. The optimum reaction conditions (reaction temperature, 40u2009°C; time, 20u2009h; methane, 20u2009atm; carbon monoxide, 5u2009atm) have been obtained.

End‐to‐End Self‐Assembly of Semiconductor Nanorods in Water by Using an Amphiphilic Surface Design

One-dimensional (1D) self-assemblies of nanocrystals are of interest because of their vectorial and polymer-like dynamic properties. Herein, we report a simple method to prepare elongated assemblies of semiconductor nanorods (NRs) through end-to-end self-assembly. Short-chained water-soluble thiols were employed as surface ligands for CdSeu2005NRs having a wurtzite crystal structure. The site-specific capping of NRs with these ligands rendered the surface of the NRs amphiphilic. The amphiphilic CdSeu2005NRs self-assembled to form elongated wires by end-to-end attachment driven by the hydrophobic effect operating between uncapped NR ends. The end-to-end assembly technique was further applied to CdSu2005NRs and CdSe tetrapods (TPs) with a wurtzite structure.

Cobalt catalyzed carboxylation reaction of saturated hydrocarbons with CO in the presence of K2S2O8 and TFA under mild conditions

Abstract Cobalt(II) acetate (Co(OAc) 2 ) has been found to be an efficient catalyst for the carboxylation reaction of saturated hydrocarbons with CO to yield the corresponding carboxylic acids in high yields in the presence of K 2 S 2 O 8 and CF 3 COOH. About 89.5% conversion of propane is obtained in this reaction. The activation parameters of the reaction of propane have been determined by Arrhenius and Eyring plots.

LANTHANOID-CATALYZED RING-OPENING REACTION OF EPOXIDES WITH ACYL HALIDES

Abstract Eu(dpm)3 [dpm: dipivaloylmethanate] catalyzes the ring-opening reaction of epoxides with acyl halides affording the corresponding 2-haloalkyl esters. The stereochemical course was confirmed as trans-addition in the case of the reaction of cyclohexene oxide.

One-step carboxylation reaction of saturated hydrocarbons with CO by Co(OAc)2 catalyst under mild conditions

Abstract Direct carboxylation reaction of saturated hydrocarbons with carbon monoxide to afford the corresponding carboxylic acids has been investigated in the presence of cobalt catalysts such as Co(OAc) 2 and K 2 S 2 O 8 in CF 3 COOH (TFA). Alkyl trifluoroacetates were also formed in this reaction in different quantities, depending on the reaction conditions. Methane and ethane gave very low yields of the corresponding carboxylic acids only. The conversion of propane is about 89.5% (based on propane) when 1xa0bar (0.76xa0mmol) of propane reacted with 30xa0bar of carbon monoxide in the presence of 0.1xa0mmol of Co(OAc) 2 and 10xa0mmol of K 2 S 2 O 8 in 5xa0ml of TFA at 70°C for 15xa0h. In this reaction, iso -butyric acid is the major product and n -butyric acid and iso -propyl trifluoroacetate are the by-products. The maximum selectivity of iso -butyric acid obtained in this reaction is 62%. Cyclopentane and cyclohexane underwent this reaction under the same reaction conditions; the carboxylated product of cyclopentane is the minor product but, in the case of cyclohexane the carboxylated product is the major one. On the other hand, cycloheptane did not undergo the carboxylation reaction. The activation energies of the reaction of propane (7xa0bar) with carbon monoxide (30xa0bar) in the presence of Co(OAc) 2 (0.1xa0mmol), K 2 S 2 O 8 (10xa0mmol) and TFA (5xa0ml) for 3xa0h at the temperature range of 65–80°C have been determined to be 9.7, 13.4 and 20.3xa0kcal/mol for the formation of iso - and n -butyric acids and iso -propyl trifluoroacetate, respectively.

Generation of allenic samarium complexes from propargylic ethers and (C5Me5)2Sm(thf)2, and their electrophilic trapping

Allenic samarium complexes are readily generated in high yields by the reaction of propargylic benzyl ethers with (C5Me5)2Sm(thf)2. Electrophilic trapping of the complexes derived from the secondary and tertiary ethers with cyclohexanone and dimethylphenylsilyl chloride gives the corresponding propargylic products selectively, whereas α-allenic alcohols are predominantly obtained in the reaction of the complexes, generated from the primary ethers, with cyclohexanone.