Faculty Profiles - YAMAGUCHI, Shigehiro

Sequential Electrophilic and Photochemical Cyclizations from Bis(bithienyl)acetylene to a Tetrathienonaphthalene Core Reviewed

Borylated Dibenzoborepin Synthesized via Skeletal Rearrangement and its Photochromism Based on Bora-Nazarov Cyclization Reviewed

A. Iida, S. Saito, T. Sasamori, and S. Yamaguchi

Angew. Chem. Int. Ed. Vol. 52 page： 3760-3764 2013.2

Borylated Dibenzoborepin Synthesized via Skeletal Rearrangement and its Photochromism Based on Bora-Nazarov Cyclization Reviewed

A. Iida, S. Saito, T. Sasamori, S. Yamaguchi

Angew. Chem. Int. Ed. Vol. 52 page： 3760-3764 2013.2

Thiophene-Fused Bisdehydro[12]annulene That Undergoes Transannular Alkyne Cycloaddition by Either Light or Heat

Fukazawa Aiko, Oshima Hiroya, Shiota Yoshihito, Takahashi Shouya, Yoshizawa Kazunari, Yamaguchi Shigehiro

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Vol. 135 ( 5 ) page： 1731 - 1734 2013.2

Chuandong Dou, Shohei Saito, Libin Gao, Naoki Matsusumoto, Takashi Karasawa, Hongyu Zhang, Aiko Fukazawa, Shigehiro Yamaguchi

ORGANIC LETTERS Vol. 15 ( 1 ) page： 80 - 83 2013.1

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Photoirradiation of bis(bithienyl)acetylenes in the presence of iodine undergoes sequential electrophilic and photochemical cyclizations to produce tetrathienonaphthalenes (TTN) in one pot. The UN framework is readily transformed into cruciform pi-extended derivatives, which form ordered nano/microstructures.

DOI： 10.1021/ol303107y

Thermal 8 pi electrocyclic reaction of heteroarene tetramers: new efficient access to pi-extended cyclooctatetraenes Reviewed

Kazuhiro Mouri, Shohei Saito, Ichiro Hisaki, Shigehiro Yamaguchi

CHEMICAL SCIENCE Vol. 4 ( 12 ) page： 4465 - 4469 2013

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Bromo-substituted acyclic thiazole tetramers selectively underwent an 8 pi thermal electrocyclic reaction at high temperatures of 280-300 degrees C without solvent, producing p-extended thiazole-fused cyclooctatetraenes (COTs) in high yields. A quantum chemical study provided a rationale for the lower activation barrier and high selectivity of the 8 pi electrocyclic reaction mode over a competitive 6 pi electrocyclic reaction. The terminal bromine atom acts as a leaving group to trigger the rearomatization of the electrocyclized intermediate, which leads to the formation of the energetically stable COT products. This synthetic protocol enables us to synthesize a series of thiazole-fused COTs, including a derivative that can form loosely stacked columnar arrays in the crystalline state and shows fluorescence in the solid state.

DOI： 10.1039/c3sc52232f

S-Pechmann dye: a thiolactone-containing organic dye with a pronounced electron-accepting character and its solid-state photophysical properties Reviewed

Aiko Fukazawa, Makoto Adachi, Ken Nakakura, Shohei Saito, Shigehiro Yamaguchi

CHEMICAL COMMUNICATIONS Vol. 49 ( 64 ) page： 7117 - 7119 2013

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

A sulfur analogue of a Pechmann dye has been synthesized. In addition to long-wavelength absorption and fluorescence, it showed multiple redox processes with low reduction potentials in cyclic voltammetry. The size effect of sulfur is responsible for its enhanced electron-accepting character.

DOI： 10.1039/c3cc41007b

Dibenzopentalenes from B(C6F5)(3)-Induced Cyclization Reactions of 1,2-Bis(phenylethynyl)benzenes Reviewed

Chao Chen, Marcel Harhausen, Rene Liedtke, Kathrin Bussmann, Aiko Fukazawa, Shigehiro Yamaguchi, Jeffrey L. Petersen, Constantin G. Daniliuc, Roland Froehlich, Gerald Kehr, Gerhard Erker

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 52 ( 23 ) page： 5992 - 5996 2013

Benzene-fused BODIPY and fully-fused BODIPY dimer: impacts of the ring-fusing at the b bond in the BODIPY skeleton Reviewed

Atsushi Wakamiya, Takanori Murakami, Shigehiro Yamaguchi

CHEMICAL SCIENCE Vol. 4 ( 3 ) page： 1002 - 1007 2013

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

4,4-Difluoro-4-bora-3a, 4a-diaza-s-indacenes (BODIPYs) are fascinating dyes with great potentials for various applications. To establish the design principle for the modification of the BODIPY skeleton, we now investigate the electronic impacts of the introduction of ring-fused structures. The DFT calculations revealed that while the benzene-fusing at the a bond in the BODIPY skeleton increases the HOMO level, the benzene-fusing at the b bond leads to a decreased LUMO level. Based on these results, a benzo[b]fused BODIPY 1 and a fully-fused BODIPY dimer 2 were synthesized. X-ray crystal structure analysis demonstrated that the benzo[b]-fused structure significantly perturbs the pi-conjugation with enhancement of an electron-accepting azafulvene character. In the ring-fused BODIPY dimer 2, the central benzene ring is largely deviated from the aromatic benzene geometry. As a consequence, 2 has a significantly low-lying LUMO delocalized along the periphery. In cyclic voltammograms, the benzene-fused BODIPY 1 and fully-fused dimer 2 indeed showed reversible reduction waves at much less negative potentials (E-1/2 = -1.05 V vs. Fc/Fc(+) for 1, -0.85 V for 2), relative to a non-fused BODIPY 3 (E-1/2 = -1.40 V). In addition, the benzene-fused BODIPYs showed broad and intense absorption bands in the Vis-NIR region. In particular, the BODIPY dimer 2 showed an intense absorption at 629 nm with a broad shoulder band reaching 900 nm. Corresponding to the red-shifted absorption, compounds 1 and 2 showed weak fluorescence in the deep red region (lambda(em) = 690 nm, Phi(F) < 0.01) and in the near-infrared region (940 nm, Phi(F) < 0.01), respectively.

DOI： 10.1039/c2sc21768f

J-GLOBAL

Borylated Dibenzoborepin: Synthesis by Skeletal Rearrangement and Photochromism Based on Bora-Nazarov Cyclization Reviewed

Azusa Iida, Shohei Saito, Takahiro Sasamori, Shigehiro Yamaguchi

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 52 ( 13 ) page： 3760 - 3764 2013

Modulating the Photoisomerization of N,C-Chelate Organoboranes with Triplet Acceptors

Zachary M. Hudson, Soo-Byung Ko, Shigehiro Yamaguchi, Suning Wang

ORGANIC LETTERS Vol. 14 ( 21 ) page： 5610 - 5613 2012.11

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Triplet acceptors such as naphthalene, pyrene, and anthracene have been found to be highly effective in controlling the photoisomerization efficiency of N,C-chelate boryl chromophores, establishing the involvement of a photoactive triplet state in the isomerization of this class of photochromic compounds.

DOI： 10.1021/ol302742g

Boron-Containing PAH as a Substructure of Boron-Doped Graphene Reviewed

C. Dou, S. Saito, K. Matsuo, I. Hisaki, and S. Yamaguchi

Angew. Chem. Int. Ed. Vol. 51 page： 12206-12210 2012.10

TICT Fluorescence of N-borylated 2,5-Diarylpyrroles: A Gear Like Dual Motion in the Excited State Reviewed

T. Taniguchi, J. Wang, S. Irle, and S. Yamaguchi

Dalton Trans. Vol. 42 page： 620-624 2012.10

Polycyclic pi-Electron System with Boron at Its Center Reviewed

Shohei Saito, Kyohei Matsuo, Shigehiro Yamaguchi

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Vol. 134 ( 22 ) page： 9130 - 9133 2012.6

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

We disclose a new planarized triarylborane in which the tri-coordinated boron atom is embedded in a fully fused polycyclic pi-conjugated skeleton. The compound shows high stability toward oxygen, water, and silica gel, despite the absence of steric protection around the B atom. Reflecting the electron-donating character of the pi-skeleton and the electron-accepting character of the B atom, this compound shows broad absorption bands that cover the entire visible region and a fluorescence in the visible/near-IR region. In addition, this compound shows dramatic property changes upon formation of a tetra-coordinated borate, such as thermochromic behavior in the presence of pyridine.

DOI： 10.1021/ja3036042

Elucidation of p-Conjugation Modes in Diarene-Fused 1,2-Dihydro-1,2-diborin Dianions Reviewed

Takafumi Araki, Atsushi Wakamiya, Kenji Mori, Shigehiro Yamaguchi

CHEMISTRY-AN ASIAN JOURNAL Vol. 7 ( 7 ) page： 1594 - 1603 2012.6

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

A series of diarene-fused 1,2-dihydro-1,2-diborins were prepared as a new B?B-bond-embedded polycyclic p-electron system. The reduction of these compounds with metals produced their corresponding dianions, the p-conjugation modes of which varied from 6p-conjugation within the central 1,2-diborin skeleton to 14p peripheral conjugation over the tricyclic skeleton, depending on the nature of the reduced biaryl framework. Moreover, the countercation to the dianions had a significant effect on the absorption spectra, with a dramatic color change from yellow to deep blue, depending on the distance between the tricyclic dianion skeleton and the countercation.

DOI： 10.1002/asia.201200055

Polycyclic π-Electron System with Boron at Its Center Reviewed

S. Saito, K. Matsuo, and S. Yamaguchi

J. Am. Chem. Soc. Vol. 134 page： 9130-9133 2012.5

Preparation of Dihydroborole Derivatives by a Simple 1,1-Carboboration Route

Andreas Feldmann, Azusa Iida, Roland Froehlich, Shigehiro Yamaguchi, Gerald Kehr, Gerhard Erker

ORGANOMETALLICS Vol. 31 ( 6 ) page： 2445 - 2451 2012.3

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

2,3-Dihydroboroles are readily formed by treatment of dicyclopropylacetylene with the strongly electrophilic borane B(C6F5)(3). The reaction involves a sequence of 1,1-carboboration reactions and proceeds via dienylborane intermediates. Consistent with this, the reaction of the conjugated enyne 15c with B(C6F5)(3) leads to the formation of a dihydroborole.

DOI： 10.1021/om300065m

Planarized Triarylboranes: Stabilization by Structural Constraint and Their Plane-to-Bowl Conversion Reviewed

Zhiguo Zhou, Atsushi Wakamiya, Tomokatsu Kushida, Shigehiro Yamaguchi

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Vol. 134 ( 10 ) page： 4529 - 4532 2012.3

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Triphenylborane and 9,10-diphenyl-9,10-dihydro-9,10-diboraanthracene, constrained to a planar arrangement with methylene tethers, were synthesized by intramolecular multi-fold Friedel-Crafts cyclization. These compounds were stable toward air, water, and amines, despite the absence of steric protection in the vertical direction with respect to the B atoms, and showed characteristic structural, electronic, and photophysical properties. In addition, upon treatment with a fluoride ion, these compounds underwent a plane-to-bowl conversion in a controlled manner.

DOI： 10.1021/ja211944q

Synthesis and Photophysical Properties of Aryl-Substituted 2-Borylbenzaldimines and Their Extended pi-Conjugated Congeners Reviewed

Benedikt Neue, Roland Froehlich, Birgit Wibbeling, Aiko Fukazawa, Atsushi Wakamiya, Shigehiro Yamaguchi, Ernst-Ulrich Wuerthwein

JOURNAL OF ORGANIC CHEMISTRY Vol. 77 ( 5 ) page： 2176 - 2184 2012.3

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Novel N-aryl-substituted 2-borylbenzaldimines 6 and related systems with extended pi-framework 7 based on two borylbenzaldimine units linked by a spacer moiety were synthesized by condensation reactions of 2-(dimesitylboryl)benzaldehyde 3 with various amines 4 and diamines 5. All compounds were completely characterized including X-ray diffraction, especially in view of Lewis acid-base B-O and B-N interactions. The electronic as well as the photophysical properties of bisimines 7 were determined using cyclic voltammetry, UV/vis, and fluorescence spectroscopy and quantum chemistry. These compounds feature large Stokes shifts and reversible reduction waves. Interestingly, UV irradiation experiments unfold enhanced photostability for compounds 7 with an extended pi-skeleton. By use of 1,8-diaminonaphthalene we observed the formation of a hitherto unknown BN-heterocyclic compound 9 fused with a perimidine skeleton. Structural and energetic aspects were evaluated by high level quantum chemical methods (DFT and SCS-MP2-calculations).

DOI： 10.1021/jo202212s