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Kazunori Miyamoto

Publications and source records attributed to Kazunori Miyamoto.

14 recordsLinked to original sources
PubMed2006

Silver technology for stabilization of simple (Z)-enethiols: stereoselective synthesis and reaction of silver (Z)-enethiolates.

Reported here for the first time are the stereoselective synthesis and reaction of simple silver (Z)-enethiolates, which serve as stabilized (Z)-enethiol storage. In contrast to labile enethiols, silver (Z)-enethiolates are stable even in solutions, and their isolation and purification are very simple. The method for synthesis of silver (Z)-enethiolates involves an unusual vinylic SN2 reaction of (E)-vinyl-lambda3-iodanes with thiobenzamides yielding the inverted (Z)-S-vinylthioimidonium salts, followed by their regioselective C-S bond cleavage with silver acetate. Alkylation, arylation, and Michael addition of silver (Z)-enethiolates yielding (Z)-vinyl sulfides were dramatically accelerated by the addition of Bu4NI (LiI), which probably generates reactive ammonium (Z)-enethiolates with an increased nucleophilicity.

Journal Article↗
PubMed2005

Iodobenzene-catalyzed alpha-acetoxylation of ketones. in situ generation of hypervalent (diacyloxyiodo)benzenes using m-chloroperbenzoic acid.

Reported here for the first time is the iodobenzene-catalyzed alpha-oxidation of ketones, in which diacyloxy(phenyl)-lambda3-iodanes generated in situ act as real oxidants of ketones and m-chloroperbenzoic acid serves as a terminal oxidant. Oxidation of a ketone with m-chloroperbenzoic acid in acetic acid in the presence of a catalytic amount of iodobenzene, BF3.Et2O, and water at room temperature under argon affords an alpha-acetoxy ketone in good yield. p-Methyl- and p-chloroiodobenzene also serve as efficient catalysts in this direct oxidation. We found that when the reaction was carried out in the absence of a catalytic amount of iodobenzene, Baeyer-Villiger oxidation of a ketone took place. It is noted that use of water and BF3.Et2O is crucial to the success of this alpha-acetoxylation.

Journal Article↗
PubMed2005

Effects of complexation with 18-crown-6 on the hypernucleofugality of phenyl-lambda3-iodanyl groups. Synthesis of vinyl-lambda3-iodane.18-crown-6 complex.

[structure: see text] 4-tert-Butyl-1-cyclohexenyl(phenyl)(tetrafluoroborato)-lambda(3)-iodane forms a discrete supramolecular complex by the reaction with 18-crown-6. Solvolysis of the cyclohexenyl-lambda(3)-iodane in the presence of 18-crown-6 indicates that the complexation with 18-crown-6 tends to decrease the leaving group ability of hypervalent phenyl-lambda(3)-iodanyl groups.

Journal Article↗
PubMed2003

Isolation, characterization, and reaction of activated iodosylbenzene monomer hydroxy(phenyl)iodonium ion with hypervalent bonding: supramolecular complex PhI+OH.18-crown-6 with secondary I...O interactions.

The isolation, characterization, and reaction of the active species hydroxy(phenyl)iodonium ion with hypervalent bonding are reported. Reaction of iodosylbenzene with HBF(4)-Me(2)O in the presence of equimolar 18-crown-6 in dichloromethane afforded the hydroxy-lambda(3)-iodane complex PhI(OH)BF(4).18-crown-6 as stable yellow prisms. X-ray structure analysis indicated that both the close contacts between the iodine(III) and the three adjacent oxygen atoms of 18-crown-6, and the hydrogen bonding OH.O(crown ether) will be responsible for the increased stability of the complex as compared to the uncomplexed PhI(OH)BF(4). The crown ether complex is highly reactive and serves as a versatile oxidant even in water: thus, the complex undergoes oxidative transformations of a variety of functional groups such as olefins, alkynes, enones, silyl enol ethers, sulfides, and phenols under mild conditions.

Journal Article↗
PubMed2003

Solid state structures of pentacoordinated lambda3-iodanes with a trigonal bipyramidal geometry: synthesis of diphenyl- and alkynyl(phenyl)-lambda3-iodane complexes with 1,10-phenanthroline.

The single crystal X-ray structure of the supramolecular complex formed between diphenyl-lambda3-iodane (Ph2IBF4) or 1-alkynyl(phenyl)-lambda3-iodane [Bu(t)CCI(Ph)BF4] and 1,10-phenanthroline indicates a hitherto unknown distorted trigonal bipyramidal geometry around iodine(III), in which 1,10-phenanthroline acts as a bidentate ligand and occupies equatorial sites.

Journal Article↗
PubMed2003

Synthesis of 1-alkynyl(diphenyl)onium salts of group 16 elements via heteroatom transfer reaction of 1-alkynyl(phenyl)-lambda 3-iodanes.

1-Alkynyl(phenyl)-lambda 3-iodanes undergo selective transfer of the alkynyl groups over the phenyl group onto diphenyl chalcogens. Exposure of 1-alkynyl(phenyl)-lambda 3-iodanes to diphenyl chalcogens (S, Se, and Te) in dichloromethane or 1,2-dichloroethane affords 1-alkynyl(diphenyl)sulfonium, -selenonium, and -telluronium salts in high yields.

Journal Article↗
PubMed2003

Secondary hypervalent I(III)...O interactions: synthesis and structure of hypervalent complexes of diphenyl-lambda3-iodanes with 18-crown-6.

Reported here for the first time are the synthesis and characterization of supramolecular complexes between diaryl-lambda(3)-iodanes and 18-crown-6 (18C6). Slow evaporation of solvents afforded 1:1 and 2:1 complexes between Ph(2)IBF(4) and 18C6 as stable crystals, depending on the conditions. X-ray crystal structures of these complexes indicated that each iodine atom contacts with the three adjacent oxygen atoms of 18C6 through two hypervalent secondary bonding and a weak interaction. (1)H NMR analyses and CSI-MS spectra showed that, in dichloromethane solution, Ph(2)IBF(4) exclusively forms the 1:1 complex with 18C6 (binding constant K(a), 1.02 x 10(3) M(-)(1)). The binding constants decrease with the increased solvent donor ability (Gutmann's DN). Changing the heteroatom ligand from BF(4) to the less nucleophilic PF(6) and AsF(6) increased the binding constant by about six times. Substitution of an electron-withdrawing group onto the para position of Ph(2)IBF(4) tends to increase in the complex stability. A linear Hammett relationship (rho = 0.59) between log K(a) and sigma(p)(+) values of substituents indicates that the diaryl-lambda(3)-iodanes with electropositive iodine(III) interact more efficiently with 18C6. Decreased binding magnitude was measured with 15C5, dibenzo-18C6, dibenzo-21C7, and dibenzo-30C10.

Journal Article↗
PubMed2003

Clear cell ependymoma with a lipidized component that developed in the thoracic spinal cord.

The authors report a case of clear cell ependymoma with a lipidized component that developed in the thoracic spinal cord. A 59-year-old man was admitted to the hospital with an itchy pain in the left forearm to the left anterior and lateral chest for the past three years. Neurological findings on admission included dissociated sensory disturbance below the C8 level and increased deep tendon reflex in both lower extremities. An MRI scan of the spinal cord revealed an intramedullary tumor with a longer diameter of 3.5 cm at the T3-T4 level and a distended syrinx at the T2-T3 level. Surgery was performed after T1-T5 laminectomy. The gray, soft and well demarcated tumor was removed subtotally. Light microscopy revealed a portion where clear cells proliferated and a portion where foamy cells proliferated. In some tissue, there were a very few nuclear areas suggestive of a perivascular pseudorosette. Neither nuclear division nor necrosis was observed. Immunohistochemically, the tumor cells were positive for glial fibrillary acidic protein (GFAP), epithelial membrane antigen (EMA), vimentin, and negative for cytokeratin, synaptophysin. The MIB-1 staining index was 0.25%. Based on these findings, diagnosis of clear cell ependymoma with a lipidized component was made.

Ependymoma↗
PubMed2002

Production of cloned pigs from adult somatic cells by chemically assisted removal of maternal chromosomes.

The present study demonstrated that brief treatment of in vitro-matured porcine oocytes with demecolcine results in a membrane protrusion that contains a condensed chromosome mass, which can be easily removed by aspiration. This simple, chemically assisted method for removing maternal chromosomes enabled the production of a large number of nuclear-transferred porcine eggs. The development of eggs whose chromosomes were removed by this procedure following transfer of somatic cell nuclei to the blastocyst stage was not significantly different among groups activated using different procedures (6% to 11%) and was also not different among donor cells of different origins (3% to 9%), except for cumulus cells (0.4%). After transfer of 180 to 341 nuclear-transferred eggs that received somatic cells to 6 recipients, 2 of the recipients produced 8 healthy cloned piglets from the heart cells of a female pig. The chemically assisted method for removing maternal chromosomes was also effective for bovine and rabbit eggs.

Animals↗