Shin-ichi Takekuma

A facile preparation, the crystal structure, the chemical and electrochemical properties of [4-(dimethylamino)phenyl]-3-guaiazulenylmethylium tetrafluoroborate

Reaction of guaiazulene (1) with p-dimethylaminobenzaldehyde in methanol in the presence of tetrafluoroboric acid gives the title monocarbocation compound, [4-(dimethylamino)phenyl]-3-guaiazulenylmethylium tetrafluoroborate (2), in 90% yield. The title investigations of compound 2 compared with those of two other monocarbocations stabilized by a 3-guaiazulenyl group (i.e. phenyl-3-guaiazulenylmethyl and [4-(isopropyl)phenyl]-3-guaiazulenylmethyl cations) are reported.

The crystal structure and characteristic chemical property of 1,2-bis(3-guaiazulenylmethylium)benzene bishexafluorophosphate

Reaction of guaiazulene ( 1 ) with a 0.5 molar amount of phthalaldehyde in a mixed solvent of acetonitrile and diethyl ether in the presence of hexafluorophosphoric acid at 25°C under aerobic conditions rapidly gives the title dicarbocation compound, 1,2-bis(3-guaiazulenylmethylium)benzene bishexafluoro-phosphate ( 2 ) in 98% yield. Reduction of 2 with a large excess of NaBH 4 in a mixed solvent of acetonitrile and ethanol at 25°C quantitatively affords a unique intra -molecular cycloaddition compound 9 via the intermediate 8 . The crystal structure and characteristic chemical property of 2 are reported.

An efficient preparation, the structure and the properties of 1-isopropyl-4-(3-guaiazulenylmethylium)benzene hexafluorophosphate and tetrafluoroborate

Abstract Reactions of guaiazulene ( 1 ) with 4-isopropylbenzaldehyde in acetic acid in the presence of hexafluorophosphoric acid (and tetrafluoroboronic acid) at 25°C for 2 h under aerobic conditions quantitatively give the new title monocarbocation compounds, 1-isopropyl-4-(3-guaiazulenylmethylium)benzene hexafluorophosphate ( 4 ) and the tetrafluoroborate ( 5 ), which upon reaction with sodium methoxide dissolved in methanol in acetonitrile at 0°C for 20 min, respectively, afford as high as 92% isolated yield of 1-isopropyl-4-(3-guaiazulenylmethoxymethyl)benzene ( 8 ). The crystal structure of 5 , as the first example of carbocations stabilized by azulenyl groups, and the characteristic and chemical properties of 4 and 5 are reported.

An efficient preparation and the properties of 1,2-bis(3-guaiazulenylmethylium)benzene bishexafluorophosphate

Abstract Reaction of guaiazulene ( 1 ) with a 0.5 molar amount of phthalaldehyde in acetic acid in the presence of hexafluorophosphoric acid at 25°C for 2 h under aerobic conditions quantitatively gives the title new dicarbocation compound, 1,2-bis(3-guaiazulenylmethylium)benzene bishexafluorophosphate ( 3 ), which upon reduction with zinc powder in acetonitrile at 0°C under aerobic conditions rapidly affords a unique rearrangement product, 6,11-dimethyl-12-(3-guaiazulenyl)-9-isopropylnaphtho[2,3- a ]azulene ( 5 ), as a major product.

A highly efficient generation of γ-cyclodextrin-bicapped C601− in aqueous solution

Abstract The successive treatment of γ-cyclodextrin-bicapped C 60 complex ( 1 ) with FeCl2 and NaOH in aqueous solution at ambient temperature produces rapidly its C 60 1− complex in quantitative yield. The C 60 1− complex formation is quantitative, even in the contact with O 2 , if Na 2 S 2 O 4 is present. Plausible electron transfer mechanism is discussed.

Influence of metal complexes on the formation of γ-cyclodextrin-bicapped C60n− (n: 1 and 2) in aqueous solution

Abstract A facile electron transfer from a reducing agent, Na2S2O4 to C60 in γ-cyclodextrin-bicapped C60-complex (1) in aqueous solution at ambient temperature under argon, leading to the simultaneous formation of ‘C601−’ and ‘C602−’ has been accomplished by using excess (18-crown-6):iron(II) chloride (1:1) complex as mediator for the electron transfer.

A highly selective generation of γ-cyclodextrin-bicapped C60n− (n: 1 and 2) in DMSO

Abstract Highly selective generation of the supramolecular C 60 1− and C 60 2− species from γ-cyclodextrin-bicapped C 60 in DMSO has been achieved for the first time even in the presence of oxygen by using a large excess of NaH and excess NaBH 4 , respectively.

An Efficient Preparation, Spectroscopic Properties, and Crystal Structure of 1,1-Bis(4-[2-(dimethylamino)ethoxy]phenyl)-2-(3-guaiazulenyl)ethylene

Reaction of 2-(3-guaiazulenyl)-1,1-bis(4-hydroxyphenyl)ethylene with 2-chloroethyldimethylammonium chloride in acetone in the presence of K2CO3 at reflux temperature for 24 hours gives a new title compound in 89% yield. Spectroscopic properties and crystal structure of the target molecule are reported.

Reducing ability of supramolecular C60 dianion toward C=O, C=C and N-N bonds

Different from C60 dianion which readily reacts with electrophiles, supramolecular C60 dianion (2) generated from gamma-cyclodextrin-bicapped C60 (1) and NaBH4 (or diborate) in DMSO-H2O (9:1, v/v) is able to reduce N-N+, C=C-EWG and C=O bonds to provide the respective dihydro derivatives; 1-mediated reduction of acetophenone with NaBH4 in the presence of (Me2N)2CH2 and EtONa gives turn over frequency (TOF)/h of 400.

Electrochemical Oxidation of Methyl Abietate.

アビエチン酸メチルエステル(1)の電極酸化を種々の条件下で行った.その結果,1を酢酸に溶解し,水と支持電解質Et3Nを添加し,陽,陰両極に炭素棒を備えた無隔膜セル中,定電流50mA(電流密度4mA/cm2),通電量4F/mol,反応温度18℃ で電極酸化を行った場合に選択性が認められ,7α-acetoxy-13(βandα)-hydroxy-8(14)-abieten-18-oicacidmethylester[(2)および(3)]の混合物が86%の収率で得られた.2および3は新規化合物であり,それらの性状および各種スペクトルデータさらには2と3の生成機構の考察についても述べる.