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Ken Tanaka

Publications and source records attributed to Ken Tanaka.

30 records · Page 2Linked to original sources
PubMed2004

Rhodium-catalyzed intramolecular hydroacylation of 5- and 6-alkynals: convenient synthesis of alpha-alkylidenecycloalkanones and cycloalkenones.

A novel intramolecular hydroacylation of 5- and 6-alkynals leading to alpha-alkylidenecycloalkanones was accomplished by using cationic a rhodium(I)/BINAP complex. For all cyclizations described, a single (E)-olefin isomer was obtained. At elevated temperature, hydroacylation and double bond migration of 5- and 6-alkynals proceeded in a one-pot reaction to give cycloalkenones. An intramolecular hydroacylation of a 7-alkynal was unsuccessful. This method represents an attractive new route to highly functionalized alpha-alkylidenecycloalkanones and cycloalkenones.

Acylation↗
PubMed2003

Highly chemo- and regioselective intermolecular cyclotrimerization of alkynes catalyzed by cationic rhodium(I)/modified BINAP complexes.

[reaction: see text] Cationic rhodium(I)/modified BINAP complexes are effective catalysts for highly regioselective intermolecular cyclotrimerization of terminal alkynes and highly chemo- and regioselective intermolecular cocyclotrimerization of diethyl acetylenedicarboxylate (DEAD) and terminal alkynes. It is a noteworthy example of intermolecular cocyclotrimerization of two different alkynes in terms of catalytic activity, chemo- and regioselectivity, scope of substrates, and ease of operation. The wide applicability of this new cocyclotrimerization procedure is demonstrated in the one-step synthesis of [6]metacyclophane.

Journal Article↗
PubMed2003

Parallel kinetic resolution of 4-alkynals catalyzed by Rh(I)/Tol-BINAP: synthesis of enantioenriched cyclobutanones and cyclopentenones.

A Rh(I)/(R)-Tol-BINAP catalyst reacts with a racemic mixture of 4-alkynals to selectively furnish a cyclobutanone from the (R)-substrate and a cyclopentenone from the (S)-substrate. This method is noteworthy from several standpoints, including the scarcity of parallel kinetic resolutions (especially those that are catalyzed or that involve carbon-carbon bond formation) and the dearth of catalytic processes that generate enantioenriched cyclobutanones.

Journal Article↗
PubMed2003

Unusual hyperbilirubinemia associated with bacterial pneumonia and acute myeloid leukemia.

A 77-year-old man with pneumonia associated with acute myeloid leukemia was introduced to the hepatology unit at our hospital for hyperbilirubinemia. He had been suffering from a high fever because of pneumonia. He was icteric and his serum concentrations of total and direct bilirubin were 13.1 and 7.9 mg/dl, respectively. However, the other standard biochemical examinations for hepatic function, such as serum concentrations of aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transpeptidase and alkaline phosphatase were normal except for lactate dehydrogenase. Lactate dehydrogenase isoenzyme analysis revealed that the high concentration was derived from leukemia cells. Ultrasonography of the abdomen revealed no abnormality in the liver or biliary tract. Administration of antibiotics for pneumonia decreased the serum bilirubin concentration, however, he died because of respiratory failure caused by the progression of pneumonia at 33 days after the admission. It was suggested that a disturbance in the bilirubin metabolism without hepatocyte necrosis or mechanical cholestasis might be involved in the pathogenesis of hyperbilirubinemia in patients with infectious diseases.

Journal Article↗
PubMed2003

[A case of hemophagocytic syndrome associated with miliary tuberculosis].

We reported a case of a 76-year-female with hemophagocytic syndrome caused by military tuberculosis. The patients had complained high fever over 38.0 degrees C and anorexia. Her chest X-ray and computed tomography revealed disseminated miliary shadows in both lung fields. Laboratory examinations revealed anemia, thrombocytopenia and liver dysfunction. Bonemarrow aspirate revealed tuberculous granulomas and tubercle bacilli by acid-fast stains, and hemophagocytosis by macrophages. We diagnosed as miliary tuberculosis and tuberculosis-associated hemophagocytic syndrome, and started antituberculous and steroid therapy. After these therapy, fever, laboratory examinations dramatically improved. In this case, serum IL-18, sICAM-1, sVCAM-1 were elevated. These cytokines and adhesion molecules were reported to elevate in both hemophagocytic syndrome and tuberculosis correlating with disease activity. We conclude that IL-18, sICAM-1, sVCAM-1 may play important roles in pathogenesis of tuberculosis associated hemophagocytic syndrome.

Aged↗
PubMed2002

Practical asymmetric synthesis of the herbicide (S)-indanofan via lipase-catalyzed kinetic resolution of a diol and stereoselective acid-catalyzed hydrolysis of a chiral epoxide.

Racemic indanofan [(+/-)-1] was efficiently converted to enantiopure (S)-indanofan [(S)-1] by a combination of enzymatic resolution and chemical inversion techniques. An additional important technique is the use of an o-xylene complex of a hemiketal (S)-3c as a precursor, which can be quantitatively converted to (S)-indanofan and easily purified by recrystallization from o-xylene.

Catalysis↗
PubMed2002

Identification of impurities and statistical classification of methamphetamine tablets (Ya-Ba) seized in Thailand.

Impurity profiles of methamphetamine tablets seized in Thailand have been investigated. The samples are extracted with small amounts of ethyl acetate under alkaline condition and the extracts are analyzed by capillary gas chromatography. Nine compounds (1,2-dimethyl-3-phenylaziridine, ephedrine, methylephedrine, N-formylmethamphetamine, N-acetylmethamphetamine, N-formylephedrine, N-acetylephedrine, N,O-diacetylephedrie, methamphetamine dimer) are identified as impurities in methamphetamine tablet. Caffeine and ethyl vanillin are also detected as diluents and/or adulterants, and acetylcodeine monoacetylmorphine and diacetylmorphine are contained in many samples. In addition, trans-3,4-dimethyl-5-phenyl-2-oxazolidone is newly found as an impurity. For characterization and comparison of methamphetamine tablet exhibits, intensely and commonly detectable nine peaks are selected as the factor for multivariate analysis. The procedures reported here permit classification of 250 analyzed exhibits into five groups and characterization of classified groups.

Central Nervous System Stimulants↗
PubMed2002

A unique rhodium-catalyzed rearrangement process: isomerization of an alkyne to a 1,3-diene with concomitant migration of a formyl group. An expeditious route to dienals from readily available 4-alkynals.

In CH2Cl2, [Rh(BINAP)]BF4 catalyzes the isomerization of 4-alkynals to dienals with excellent regio- and stereoselectivity; this new process compares favorably with previously reported methods for the synthesis of this class of compounds; a possible pathway for this unusual rearrangement is provided.

Aldehydes↗
PubMed2002

Rhodium-catalyzed synthesis of cyclohexenones via a novel [4 + 2] annulation.

[reaction: see text] In the presence of a rhodium catalyst, 4-alkynals react with alkynes to furnish cyclohexenones, presumably via metalacycle 1; as far as we are aware, this is the first example of the generation of this class of compounds through such a transformation. In view of the easy accessibility of 4-alkynals (alkynylmetal + alpha,beta-unsaturated aldehyde) and alkynes, this [4 + 2] cyclization constitutes an interesting new approach to functionalized cyclohexenones.

Journal Article↗