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Fumitoshi Kakiuchi

Publications and source records attributed to Fumitoshi Kakiuchi.

12 recordsLinked to original sources
PubMed2006

Direct observation of the oxidative addition of the aryl carbon-oxygen bond to a ruthenium complex and consideration of the relative reactivity between aryl carbon-oxygen and aryl carbon-hydrogen bonds.

When RuH2(CO)(PPh3)3 was reacted with 2,2-dimethyl-1-(2-p-tolylphenyl)propan-1-one (2), the ruthenium-aryloxy complex 3 was obtained in 76% yield. The structure of this complex was determined from 1H and 31P NMR and X-ray data. Complex 3 showed the catalytic activity for the coupling of 2 with the phenylboronate 4. The 1H and 31P NMR studies of the reaction of Ru(CO)(PPh3)3 with o-aryloxy pivalophenone revealed that the C-H bond cleavage is a kinetically favorable process but the C-O bond cleavage is a thermodynamic one. The reaction of 2'-methoxyacetophenone with vinylsilane and organoboronate resulted in chemoselective C-C bond formation.

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PubMed2005

A RuH(2)(CO)(PPh(3))(3)-catalyzed regioselective arylation of aromatic ketones with arylboronates via carbon-hydrogen bond cleavage.

When the reaction of aromatic ketones with arylboronates (arylboronic acid esters) using RuH(2)(CO)(PPh(3))(3) (3) as a catalyst was conducted in toluene, the corresponding arylation product was obtained in moderate yields. In this case, a nearly equivalent amount of a benzyl alcohol derived from a reduction of an aromatic ketone was also formed. The use of aliphatic ketones, such as pinacolone and acetone, as an additive or a solvent dramatically suppressed the reduction of the aromatic ketones and, as a result, ortho-arylation products were obtained in high yield based on the aromatic ketones. In these reactions, the aliphatic ketone functioned as a scavenger of ortho-hydrogens of the aromatic ketones and the B(OR)(2) moiety of the arylboron compound (HB species). A variety of aromatic ketones, such as acetophenones, acetonaphthones, tetralones, and benzosuberone, could also be used in this coupling reaction. Several arylboronates containing electron-donating (NMe(2), OMe, and Me) and -withdrawing (CF(3) and F) groups were also applicable to this coupling reaction. Intermolecular competitive reaction using pivalophenone-d(0)() and -d(5) and intramolecular competitive reaction using pivalophenone-d(1) were carried out using 3 as a catalyst. The k(H)/k(D) value for the intermolecular competitive reaction was substantially different, compared with intramolecular competitive reaction. This strongly suggests the production of an intermediate where the ketone carbonyl is coordinated to the ruthenium involved in this catalytic reaction. (1)H and (11)B NMR studies using 2'-methylacetophenone, phenylboronate (2), and pinacolone (6) indicate that 6 functions effectively as a scavenger of the HB species.

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PubMed2004

Ru3(CO)12-catalyzed silylation of benzylic C-H bonds in arylpyridines and arylpyrazoles with hydrosilanes via C-H bond cleavage.

Ruthenium-catalyzed silylation of sp3 C-H bonds at a benzylic position with hydrosilanes gave benzylsilanes. For this silylation reaction, Ru3(CO)12 complex showed high catalytic activity. This silylation proceeded at the methyl C-H bond selectively. For this silylation reaction, pyridyl and pyrazolyl groups, and the imino group in hydrazones, can function as a directing group. Several hydrosilanes involving triethyl-, dimethylphenyl-, tert-butyldimethyl-, and triphenylsilanes can be used as a silylating reagent. Coordination of an sp2 nitrogen atom to the ruthenium complex is important for achieving this silylation reaction.

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PubMed2004

Catalytic cross-coupling reaction of esters with organoboron compounds and decarbonylative reduction of esters with HCOONH4: a new route to acyl transition metal complexes through the cleavage of acyl-oxygen bonds in esters.

The Ru3(CO)12-catalyed cross-coupling reaction of esters with organoboron compounds leading to ketones is described. A wide variety of functional groups can be tolerated under the reaction conditions. Aromatic boronates function as a coupling partner to give aryl ketones. Acyl-alkyl coupling to dialkyl ketones is also achieved by the use of 9-alkyl-9-BBN in place of boronates. The Ru3(CO)12-catalyzed decarbonylative reduction of esters with ammonium formate (HCOONH4) leading to hydrocarbons is also described. No expected aldehydes are produced, and controlled experiments indicate that aldehydes are not intermediate for the transformation. A hydrosilane can also be used as a reducing reagent in place of HCOONH4. A wide variety of functional groups are compatible for both reactions. The key step for both catalytic reactions is the directing group-promoted cleavage of an acyl carbon-oxygen bond in esters, leading to the generation of acyl transition metal alkoxo complexes.

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PubMed2004

Ruthenium- and rhodium-catalyzed direct carbonylation of the ortho C-H bond in the benzene ring of N-arylpyrazoles.

The direct carbonylation of C-H bonds in the benzene ring of N-phenylpyrazoles via catalysis by ruthenium or rhodium complexes is described. The reaction of N-phenylpyrazoles with carbon monoxide and ethylene in the presence of Ru(3)(CO)(12) or Rh(4)(CO)(12) resulted in the site-selective carbonylation of the ortho C-H bonds in the benzene ring to give the corresponding ethyl ketones. A variety of functional groups on the benzene ring can be tolerated. N-Phenylpyrazoles have higher reactivities than would be expected, based on the pK(a) values of the conjugate acid of pyrazole. The choice of solvent for this reaction is significant, and N, N-dimethylacetamide (DMA) gives the best result.

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PubMed2004

Ruthenium-catalyzed functionalization of aryl carbon-oxygen bonds in aromatic ethers with organoboron compounds.

The ruthenium-catalyzed reaction of aryl ethers having a carbonyl group at the ortho position to the ether group with organoboronates (R-B(OCH2CMe2CH2O), R = aryl, alkenyl, and alkyl) resulted in site-selective C-C bond formation. Among the transition metal complexes screened, the RuH2(CO)(PPh3)3 complex showed the highest activity. Several aromatic ketones having methoxy or phenoxy groups at the ortho position can also be used in this coupling reaction. A variety of arylboronates containing electron-donating (NMe2, OMe, methyl, and vinyl) and -withdrawing (F and CF3) groups reacted with methoxy ketones to give the corresponding coupling products in high yields.

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PubMed2003

Ruthenium-catalyzed C-H/CO/Olefin coupling reaction of N-arylpyrazoles. Extraordinary reactivity of N-arylpyrazoles toward carbonylation at C-H bonds.

The reaction of 1-arylpyrazoles with CO and ethylene in the presence of Ru(3)(CO)(12) resulted in regioselective carbonylation at the ortho C-H bonds. While it is found that the pyrazole ring also functions as the directing group for C-H bond cleavage, the efficiency of the reaction depends on the position of the pyrazole ring.

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PubMed2003

A ruthenium-catalyzed reaction of aromatic ketones with arylboronates: a new method for the arylation of aromatic compounds via C-H bond cleavage.

The ruthenium-catalyzed reaction of aromatic ketones with arylboronic acid esters (arylboronates) gave the ortho arylation product. For this coupling reaction, a RuH2(CO)(PPh3)3 complex exhibited the highest catalytic activity among the complexes screened. Several aromatic ketones, for example, acetophenones, acetonaphthone, alpha-tetralone, and benzosuberone, can be used in this coupling reaction. A variety of arylboronates containing electron-donating (OMe and NMe2) and -withdrawing (F and CF3) groups were found to react with aromatic ketones to give the corresponding aylation products. The corresponding arylboronic acids could be used in this coupling reaction, but the yields were slightly lower, as compared to those of the reaction using the corresponding arylboronates.

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PubMed2002

Ru3(CO)12-catalyzed C-H/CO/olefin coupling of N-pyridylindolines. Direct carbonylation at a C-H bond delta to the pyridine nitrogen.

The reaction of N-pyridylindolines with CO and ethylene in the presence of Ru3(CO)12 results in direct carbonylation at a C-H bond delta to the pyridine sp2 nitrogen, which represents a new type of C-H/CO/olefin coupling. The presence of a pyridine ring as a directing group on the substrates is essential for the reaction to proceed. The choice of N,N-dimethylacetamide (DMA) as the solvent is crucial for the reaction to proceed efficiently.

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PubMed2002

Catalytic C-h/olefin coupling.

The cleavage and addition of ortho C-H bonds in various aromatic compounds such as ketones, esters, imines, imidates, nitrile, and aldehydes to olefins and acetlylenes can be achieved catalytically with the aid of ruthenium catalysts. The reaction is generally highly efficient and useful in synthetic methods. The coordination to the metal center by a heteroatom in directing groups such as carbonyl and imino groups is the key. The reductive elimination to form a C-C bond is the rate-determining step.

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PubMed1997

Ru(3)(CO)(12)-Catalyzed Reaction of Pyridylbenzenes with Carbon Monoxide and Olefins. Carbonylation at a C-H Bond in the Benzene Ring.

A ruthenium-catalyzed carbonylation at a C-H bond in a benzene ring is described. The reaction of pyridylbenzenes with CO (20 atm) and ethylene in toluene at 160 degrees C in the presence of a catalytic amount of Ru(3)(CO)(12) results in propionylation at an ortho C-H bond in the benzene ring. Carbonylation does not occur at the pyridine ring, although this is necessary as a directing group to promote the reaction. Olefins such as trimethylvinylsilane and tert-butylethylene in place of ethylene can also be used in this reaction, however 1-hexene, cyclohexene, allyltrimethylsilane, styrene, methyl methacrylate, vinyl acetate, triethoxyvinylsilane, and isopropenyltrimethylsilane do not afford the coupling products. Transition metal complexes, other than ruthenium carbonyl, examined thus far, do not show catalytic activity. In the reaction of meta-substituted pyridylbenzenes, such as those having Me, OMe, CF(3), and COOMe group at the meta position in the benzene ring, carbonylation takes place at the less hindered C-H bond exclusively, irrespective of the electronic nature of the substituents. It is apparent that steric factors are more important for the control of regioselectivity. The reaction is also applicable to naphthyl and thienyl rings. Six-membered heterocycles, such as 2-pyrimidine and 4-pyrimidine, are also effective directing groups for carbonylation at a C-H bond in the benzene ring. The present reaction represents the first, effective catalytic carbonylation reaction involving cleavage of the benzene C-H bond.

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