Toshikazu Kitagawa

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Organization: Mie University

Department: Institute for Chemical Research

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Chemicals
References

Solvolysis of 2-adamantyl p-toluenesulfonate in ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate

Co-reporter:Takao Okazaki, Koji Ito, Toshikazu Kitagawa

Tetrahedron Letters 2015 Volume 56(Issue 44) pp:6066-6068

Publication Date(Web):28 October 2015

DOI:10.1016/j.tetlet.2015.09.056

The solvolytic rate constants of 2-adamantyl p-toluenesulfonate were determined in [BMIM][BF4] in the presence/absence of 2,6-lutidine by NMR measurements. The activation parameters suggest that the reaction proceeded by kc mechanism. The solvolysis quantitatively gave 2-adamantanol as a product by the reaction with the water present in the ionic liquid. The solvent ionizing power of [BMIM][BF4] was found to be similar to that of ethanol.

Ideal Redox Behavior of the High-Density Self-Assembled Monolayer of a Molecular Tripod on a Au(111) Surface with a Terminal Ferrocene Group

Co-reporter:Toshikazu Kitagawa, Hiroaki Matsubara, Koichi Komatsu, Katsuyuki Hirai, Takao Okazaki, and Takahiro Hase

Langmuir 2013 Volume 29(Issue 13) pp:4275-4282

Publication Date(Web):March 7, 2013

DOI:10.1021/la305092g

A dyad consisting of a tripod-shaped trithiol with an adamantane core and a terminal ferrocenyl group linked through ap-phenyleneethynylene bridge was synthesized. The trithiol formed a stable self-assembled monolayer (SAM) on Au(111), wherein each molecule is bound to the surface by three-point adsorption using all sulfur atoms, with confirmation by PM-IRRAS and XPS analyses. Cyclic voltammetry of the SAM showed a line shape typical of an ideal adsorbed system, that is, a monolayer with negligible electrostatic interaction among the terminal ferrocenyl groups. Thus, a rare SAM was achieved, in which the component molecules were isolated from adjacent molecules without the coadsorption of nonelectroactive molecules.

Allyl Radical Nature of a Phenylcyclopentadienyl Radical Annelated with Two Homoadamantene Frameworks

Co-reporter:Kohei Ogawa, Koichi Komatsu, and Toshikazu Kitagawa

The Journal of Organic Chemistry 2011 Volume 76(Issue 15) pp:6095-6100

Publication Date(Web):June 23, 2011

DOI:10.1021/jo200748m

1-Phenylcyclopentadiene fused with two homoadamantene units at the 2,3- and 4,5-positions (4) was deprotonated with KH to lead to the quantitative formation of the corresponding cyclopentadienyl (Cp) anion 3–. This anion was oxidized by AgCl to afford an orange crystalline solid consisting of Cp radical 3• and cyclopentadiene 4. The ESR spectrum in hexane exhibited approximately 15 lines, demonstrating that the two homoadamantene frameworks were equivalent and that the C1–C2(Ph)–C3 moiety of the five-membered ring formed a symmetrical allyl-like radical in agreement with the prediction by DFT calculation. The reaction of the Cp radical 3• with an oxygen molecule in the presence of Ag+SbF6– afforded the SbF6– salt of a phenylpyrylium ion annelated with two homoadamantene frameworks (8+SbF6–).

Cyclobutadieneiron Tricarbonyl Annelated with Homoadamantene Frameworks

Co-reporter:Shinya Minegishi, Koichi Komatsu, and Toshikazu Kitagawa

Organometallics 2011 Volume 30(Issue 5) pp:1002-1007

Publication Date(Web):February 16, 2011

DOI:10.1021/om101054d

Cyclobutadieneiron tricarbonyl annelated with homoadamantene 2 was synthesized from the corresponding 3,4-dibromocyclobutene 8. As a stable cationic analogue of 2, the dicarbonyl nitrosyl complex 3+ was also prepared. X-ray crystallographic studies revealed that the homoadamantene units of both 2 and 3+ are highly bent out of the cyclobutadiene ring plane away from Fe. The cyclobutadiene units in 2 and 3+ are significantly distorted to a rectangular shape, which made the transannular carbon−carbon bonds shorter than the other two. An enhanced donor ability of the cyclobutadiene unit was suggested by X-ray crystallography, infrared spectra, and DFT calculations. In accordance with this, reversible oxidation waves were observed in the cyclic voltammogram of 2, reflecting an enhanced stability of the oxidized form.

Self-Sensitized Photooxygenation of a C60Cycloheptatriene Dyad to Form Norcaradiene-Derived Endoperoxides

Co-reporter:Masaaki Hanamura;Jun Kamada;Akiyo Amano;Ken'ichi Takeuchi;Takao Okazaki;Katsuyuki Hirai

European Journal of Organic Chemistry 2010 Volume 2010( Issue 17) pp:3257-3264

Publication Date(Web):

DOI:10.1002/ejoc.200901453

Abstract

The [60]fullerene–cycloheptatriene dyad 1 readily underwent [4+2] cycloaddition of molecular oxygen at the cycloheptatriene moiety to give endoperoxides 5-exo and 5-endo. The involvement of singlet oxygen was verified by the complete inhibition of oxygenation on addition of 1,4-diazabicyclo[2.2.2]octane (DABCO), which is an efficient singlet-oxygen quencher. The observed facile oxygenation was attributed to both the strong photosensitizing ability of the fullerene cage and to the valence isomerization of 1 to the norcaradiene form, which was facilitated by the bulky tert-butyl groups. Competitive oxygenation of 1 and a related cycloheptatriene lacking the fullerenyl group (2) resulted in the formation of endoperoxides of the two molecules in comparable yields. This result demonstrates that the cycloaddition is not an in-cage reaction but occurs after the singlet oxygen has diffused from the solvent cage.