The Chemistry of Azaazulenes

Abe, Noritaka; Gunji, Takahiro

doi:10.3987/rev-10-sr(e)1

Cited by 32 publications

(14 citation statements)

References 94 publications

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“…In recent years, azulene has received increasing attention because of its unique electronic and optical properties, and the synthesis of azulene-based π-functional materials has become an active field of study. − Azulene derivatives have been used in many fields such as electrochromic materials, anion sensors, charge-transfer complexes, organic conductors, nonlinear optical materials, and near-infrared resonance materials . Moreover, azulene derivatives have also been applied in organic field-effect transistors (OFETs) and solar cells. − However, the development of azulene-based organic materials is limited by molecular design and synthesis difficulties.…”

Section: Introductionmentioning

confidence: 99%

Azulene-Based π-Functional Materials: Design, Synthesis, and Applications

2021

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Conspectus Azulene, an isomer of naphthalene, is a molecule of historical interest for its unusual photophysical properties, including a beautiful blue color derived from the narrow HOMO–LUMO energy gap and anti-Kasha fluorescence from S2 to S0. More recently, it has attracted increasing attention for its novel electronic structure, including an electron-rich five-membered ring and an electron-deficient seven-membered ring with a dipole moment of 1.08 D resulting from resonance delocalization, its different reactivities at odd and even positions, and its stimuli-responsive behavior. As a key building block, azulene has been used in various fields because of its unique physicochemical properties. Recent studies have demonstrated the great potential of azulene for constructing advanced organic materials. However, exploring azulene-based materials has long been hindered by challenges in molecular design and synthesis. Most of the reported azulene-based materials have the azulene unit incorporated through the five-membered ring or seven-membered ring. Creating azulene-based novel building blocks for optoelectronics and using 2,6-connected azulene units to construct conjugated polymers that can adequately utilize the “donor–acceptor” structure of azulene remained underexplored before our contributions. Besides, for most azulene-fused polycyclic aromatic hydrocarbons (PAHs) and heteroaromatics, the azulene substructures were created during later synthesis stages, and the use of azulene derivatives as starting materials to design and synthesize PAHs and heteroaromatics intelligently is still limited. In this Account, we summarize our efforts on the design, synthesis, and applications of azulene-based π-functional materials. Our studies start with the creation of novel π-conjugated structures based on azulene. The design strategy, synthesis, and optoelectronic performance of the first class of azulene-based aromatic diimides, 2,2′-biazulene-1,1′,3,3′-tetracarboxylic diimide (BAzDI) and its π-extended and π-bridged derivatives, are presented. Notably, antiparallel stacking between adjacent azulene units derived from azulene’s dipole was observed in single crystals of BAzDI and its derivatives. Besides, we developed an azulene-fused isoindigo analogue, azulenoisoindigo, which combines the merits of both isoindigo and azulene, including reversible redox behavior and reversible proton responsiveness. Then we discuss our contributions to the design and synthesis of 2,6-azulene-based conjugated polymers. By incorporation of 2,6-connected azulene units into the polymeric backbone, two conjugated polymers with high organic field-effect transistor (OFET) performance were developed. Two 2,6-azulene-based polymers with proton responsiveness and high electrical conductivity upon protonation were also provided. We also discuss our recent studies on azulene-based heteroaromatics. Two azulene-fused BN-heteroaromatics were designed and synthesized, and they exhibited a selective response to fluoride ion and unexpected deboronization upo...

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Section: Introductionmentioning

confidence: 99%

Azulene-Based π-Functional Materials: Design, Synthesis, and Applications

2021

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“…Sugimura et al pointed out that the pyridinium ylide formed under the conditions added not only to tropone (6) to lead the azazulene product via several reaction intermediates but also added to the intermediates to reduce yield of the 1-azaazulene product. Therefore, slow addition of 7 to a reaction mixture was applied in order to prevent the unfavorable second addition of the ylide.…”

Section: Scheme 1 Synthesis Ofmentioning

confidence: 99%

“…[5] Meanwhile, we have synthesized various 1-azaazulene derivatives (1)(2)(3)(4), shown in Fig. 1, and studied ability of 1-azaazulenes [6][7][8][9] as a ligand for metal ions and as a base for Brønsted acids. [10][11][12] It was found that 2-(pyrid-2-yl)-1-azaazulene (1) chelated with metal ions and bound with proton and, then, showed the enhanced emission upon photoexcitation.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Properties of 2,6-Bis(1-Azaazulen-2-yl)-Pyridine

Oda

Yamaga²,

Kumai³

et al. 2015

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The title compound, 2,6-bis(1-azaazulen-2-yl)pyridine (5), was synthesized by condensation between tropone (6) and 2,6-bis(pyridinioacetyl)pyridinium salt (7) in the presence of ammonium acetate. By slow addition of an acetic acid solution of the pyridinium salt 7 to a mixture of 6 and ammonium acetate the yield of 5 was improved. Physical properties of 5 were investigated. It is worthy to note that upon irradiation 5 shows strong emission in acidic media in contrast to very weak emission in neutral media.

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“…of CuI, and 2.0 equiv. of K 2 CO 3 in THF at 80 °C for 24 h gave 2‐chloro‐3‐(2‐pyridyl)‐1‐azaazulene ( 152 ) and (2‐chloro‐1‐azaazulen‐3‐yl)‐(2‐pyridyl)‐[ N (2‐hydroxyethyl)]‐( N ‐phenyl)aminoethylborate ( 153 ) in 50 and 3% yields, respectively (Scheme ) 66,67…”

Section: Cross‐coupling Reactions Of Polyhalogenated Five‐membered mentioning

confidence: 99%

Selective Palladium‐Catalyzed Suzuki–Miyaura Reactions of Polyhalogenated Heteroarenes

2012

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The palladium-catalyzed Suzuki-Miyaura reaction of multiply halogenated, electron-rich and electron-deficient heteroarenes is one of the most reliable and environmentally friendly tools for installing a wide range of non-functionalized and functionalized carbon substituents onto heteroaromatic systems with exquisite chemo-and site-selectivity. For substrates with different halogen groups the chemoselectivity of the Suzuki-Miyaura reactions has been found to be dependent on the reactivity difference between the halogens. However, the hardest achievement of selectivity in Suzuki-Miyaura monocouplings involving polyhalogenated heteroarenes with identical halogen atoms has been shown to be dominated by steric and electronic effects and the presence of directing groups at positions neighbouring the reaction sites. Moreover, in the case of symmetrically substituted dihaloheteroarenes with identical halogen atoms, highly selective monocoupling reactions have often been achieved only after a careful optimization of reaction parameters including the catalyst precursor, base, solvent, and the molar ratio between electrophile and organoboron reagent. This critical review with 341 references covers developments on the chemo-and site-selective Suzuki-Miyaura monocoupling reactions of polyhalogenated heteroarenes with different or identical halogen atoms. It also includes the synthesis of polysubstituted heteroarenes, not easily accessible by other means, via consecutive monocoupling reactions and/ or a more synthetically valuable approach involving one-pot polycoupling reactions.

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The Chemistry of Azaazulenes

Cited by 32 publications

References 94 publications

Azulene-Based π-Functional Materials: Design, Synthesis, and Applications

Azulene-Based π-Functional Materials: Design, Synthesis, and Applications

Synthesis and Properties of 2,6-Bis(1-Azaazulen-2-yl)-Pyridine

Selective Palladium‐Catalyzed Suzuki–Miyaura Reactions of Polyhalogenated Heteroarenes

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