Synthesis of 2-Amino-4-arylazulenes from 8-Aryl-2-cyclohepta[]furan-2-ones and Transformation into 6-Aryl-7-naphth[3,2,1-]azulen-7-ones.

2-Amino-4-arylazulene derivatives were prepared from 8-aryl-2-cyclohepta[]furan-2-ones, which were converted into 6-aryl-7-naphth[3,2,1-]azulen-7-ones through a several step process. The reaction of 8-aryl-2-cyclohepta[]furan-2-ones bearing an ester group at the 3-position with malononitrile in the presence of triethylamine afforded 2-amino-4-arylazulenes. The prepared 2-amino-4-arylazulenes were converted to the corresponding 2-chloro derivatives by the Sandmeyer reaction, which were subsequently transformed into 2,4-diarylazulenes by Suzuki-Miyaura coupling with various aryl boronic acids.

Synthesis, Structural, and Optical Properties of Azuleno[1,2-]pyran-1-ones: Bro̷nsted Acid-Mediated Cyclization of 2-Azulenylalkynes.

Pyrones and their aromatic ring-fused derivatives have gained significant attention due to their diverse biological activities and potential as foundational frameworks for advanced materials. In this paper, we describe a proficient approach for the preparation of azuleno[1,2-]pyran-1-ones, which are difficult to produce by using conventional methods. The synthesis was achieved through Bro̷nsted acid-mediated cyclization of 2-azulenylalkynes.

Pyrrole-Fused Azacoronene Analog with Sulfur Embedded in the Outer Periphery.

The synthesis of sulfur-embedded hexapyrrolohexaazacoronene (HPHAC) analog and its corresponding desulfurized and rearranged compounds was achieved from tetrafluoroisothianaphthene. Structures of all the new π-skeletons were determined by X-ray crystallography. Comparison of the electronic spectrum of with those of its derivatives revealed less involvement of the sulfur atom in π-conjugation.

Construction of a 2,2'-biazulene framework Brønsted acid-promoted annulation of 2,3-di(1-azulenyl)benzofurans.

Dibenzofurans featuring a 2,2'-biazulene framework were prepared in good yields by Brønsted acid-promoted annulation of 2,3-di(1-azulenyl)benzofurans in 100% HPO. NMR, UV-Vis, and fluorescence spectroscopies were used to investigate the structural and optical properties of the products prepared. Remarkably, the annulated products exhibited fluorescence, with the longest wavelength of azulene derivatives reported to date, which extended into the near-infrared region under acidic conditions.

Synthesis, Reactivity, and Properties of Benz[]azulenes the [8 + 2] Cycloaddition of 2-Cyclohepta[]furan-2-ones with an Enamine.

Starting with the reaction of 2-cyclohepta[]furan-2-ones with an enamine, which was prepared from 4--butylcyclohexanone and pyrrolidine, benz[]azulenes having both formyl and -butyl groups were obtained in the three-step sequence. Subsequently, both the formyl and -butyl groups were eliminated by heating the benz[]azulene derivatives in 100% HPO to give benz[]azulenes without these substituents in high yields. In terms of product yield, this method is the best one ever reported for the synthesis of the parent benz[]azulene so far.

Tropo(thio)ne-embedded homoHPHACs: does the tropylium cation induce global antiaromaticity in expanded hexapyrrolohexaazacoronene?

Tropo(thio)ne-embedded homoHPHACs and their dications were synthesised by an electrophilic annulation of secoHPHAC and successive oxidation. C NMR spectra of the dications represented global 22π homoaromaticity homoconjugation, while alkylation of a thiocarbonyl-bridged homoHPHAC produced a 24π antiaromatic monocation.

Synthesis of Non- or Antiaromatic Dicarbaamethyrin: [24]Diazulihexaphyrin(0.1.0.0.1.0).

A "3+3" condensation reaction of 1,3-di(2-pyrrolyl)azulene with aryl aldehyde followed by an oxidative aromatization afforded diazuliamethyrin, [24]diazulihexaphyrin(0.1.0.

Cyclo[9]pyrrole: Selective Synthesis of [34]Nonaphyrin(0.0.0.0.0.0.0.0.0).

Cyclo[9]pyrrole, a ring-expanded porphyrin without -bridges and having an odd number of pyrroles, was synthesized via the oxidative coupling of 2,2':5',2″-terpyrrole. X-ray crystallography showed a -like symmetry with a large root-mean-square deviation. The optical properties and electronic structures were analyzed using magnetic circular dichroism spectroscopy and time-dependent density functional theory calculations.

Radially π-Extended Pyrrole-Fused Azacoronene: A Series of Crystal Structures of HPHAC with Various Oxidation States.

Radially π-extended hexapyrrolohexaazacoronene (HPHAC ) was synthesized in two steps with 2,5-di--butyl-acenaphtho[1,2-]pyrrole and hexafluorobenzene. Like its parent HPHAC , exhibited reversible oxidation behavior. Crystal structures of not only the neutral and dicationic compounds but also the radical cation were all revealed.

Manipulable Metal Catalyst for Nanographene Synthesis.

Performing bottom-up synthesis by using molecules adsorbed on a surface is an effective method to yield functional polycyclic aromatic hydrocarbons (PAHs) and nanocarbon materials. The intramolecular cyclodehydrogenation of hydrocarbons is a critical process in this synthesis; however, thus far, its elementary steps have not been elucidated thoroughly. In this study, we utilize the metal tip of a low-temperature noncontact atomic force microscope as a manipulable metal surface to locally activate dehydrogenation for PAH-forming cyclodehydrogenation.

Development of Heterocycle-Substituted and Fused Azulenes in the Last Decade (2010-2020).

Azulene derivatives with heterocyclic moieties in the molecule have been synthesized for applications in materials science by taking advantage of their unique properties. These derivatives have been prepared by various methods, involving electrophilic substitution, condensation, cyclization, and transition metal-catalyzed cross-coupling reactions. Herein, we present the development of the synthetic methods, reactivities, and physical properties for the heterocycle-substituted and heterocycle-fused azulenes reported in the last decade.

Synthesis and Aromaticity of Benzene-Fused Doubly N-Confused Porphyrins.

A bicyclo[2.2.2]octadiene(BCOD)-fused bis(dipyrromethane) derivative was reacted with methylal in the presence of trifluoroacetic acid followed by oxidation with chloranil to give a doubly N-confused phlorin derivative, which did not undergo the retro-Diels-Alder reaction extruding an ethylene molecule on heating.

Molecular Transformation to Pyrroles, Pentafulvenes, and Pyrrolopyridines by [2+2] Cycloaddition of Propargylamines with Tetracyanoethylene.

In this paper, we describe an efficient and atom-economical synthesis of highly functionalized pyrroles, pentafulvenes, and pyrrolopyridines by [2+2] cycloaddition-retroelectrocyclization of N-substituted propargylamines with tetracyanoethylene, followed by the treatment of the resulting tetracyanobutadiene derivatives with silica gel. In this reaction, silica gel plays an important role to promote the intramolecular cyclization to afford the heterocyclic products from the tetracyanobutadiene intermediates. The products were obtained selectively depending on the substituent on the nitrogen atom of the starting propargylamines.

Synthesis and Redox Properties of Pyrrole- and Azulene-Fused Azacoronene.

Synthesis of an azacoronene, in which both pyrrole and azulene moieties are circularly fused, was achieved just in three steps. This new azacoronene exhibited multistep reversible oxidations under electrochemical and chemical conditions. Formation of an aromatic 22π-electron conjugation and a tropylium cation (6π-electron conjugation) in the dicationic state was revealed by the single-crystal X-ray crystallographic analysis as well as the nucleus-independent chemical shift (NICS) and anisotropy of the induced current density (ACID) calculations.

Synthesis of 6-Amino- and 6-Arylazoazulenes via Nucleophilic Aromatic Substitution and Their Reactivity and Properties.

The nucleophilic aromatic substitution (SAr) reaction of diethyl 6-bromoazulene-1,3-dicarboxylate (1) with a variety of amines afforded the corresponding 6-aminoazulene derivatives 2a-2j in good-to-excellent yields. 6-Aminoazulene derivatives 3a-3f without the 1,3-diethoxycarbonyl functions were obtained by the deesterification of 2a-2f with 100% HPO. The reactivity of 6-aminoazulenes toward the bromination, SAr, and palladium-catalyzed cross-coupling reactions was also clarified.

Synthesis, Structures, and Properties of Core-Expanded Azacoronene Analogue: A Twisted π-System with Two N-Doped Heptagons.

A core-expanded, pyrrole-fused azacoronene analogue containing two unusual N-doped heptagons was obtained from commercially available octafluoronaphthalene and 3,4-diethylpyrrole in two steps as a heteroatom-doped nonplanar nanographene. Full fusion with the formation of the tetraazadipleiadiene framework and the longitudinally twisted structure was unambiguously confirmed by single-crystal X-ray diffraction analysis. The edge-to-edge dihedral angle along the acene moiety was 63°.

Synthesis of 2-Methyl-1-azulenyl Tetracyanobutadienes and Dicyanoquinodimethanes: Substituent Effect of 2-Methyl Moiety on the Azulene Ring toward the Optical and Electrochemical Properties.

We describe the comparative study of optical and electrochemical properties of tetracyanobutadienes (TCBDs) and dicyanoquinodimethanes (DCNQs) with a 2-methyl-1-azulenyl group and their derivatives with a 1-azulenyl substituent examined under the same conditions. TCBDs and DCNQs with a 2-methyl-1-azulenyl substituent have been prepared by the Sonogashira-Hagihara alkynylation of the 2-methyl-1-iodoazulene with arylalkyne derivatives, followed by the formal [2+2] cycloaddition-retroelectrocyclization (CA-RE) reaction with tetracyanoethylene and 7,7,8,8-tetracyanoquinodimethane. The optical properties of the TCBDs and DCNQs with a 2-methyl-1-azulenyl group were investigated through the comparison with those of TCBDs and DCNQs with a 1-azulenyl substituent by employing the UV/vis spectroscopy and theoretical calculations.

Benzene-fused bis(acenaphthoBODIPY)s, stable near-infrared-selective dyes.

Benzene-fused bis(acenaphthoBODIPY)s prepared by retro-Diels-Alder reaction of bicyclo[2.2.2]octadiene-fused precursors showed strong absorption bands in the near-infrared region and very weak absorptions in the visible region.

Synthesis of azulene-substituted benzofurans and isocoumarins via intramolecular cyclization of 1-ethynylazulenes, and their structural and optical properties.

The preparation of azulene-substituted benzofurans and isocoumarins was established by two types of intramolecular cyclization reaction of 1-ethynylazulenes. 2-(1-Azulenyl)- and 2,3-bis(1-azulenyl)benzofurans were prepared by the palladium-catalyzed cross-coupling reaction of 1-iodoazulenes with 2-ethynylphenol and that of 1-ethynylazulenes with 2-iodophenol under Sonogashira-Hagihara reaction conditions following the intramolecular nucleophilic addition of the oxygen nucleophile to the presumed 1-arylethynylazulenes. In contrast, 1-(phenylethynyl)azulenes bearing an o-methoxycarbonyl function on the substituted phenyl moiety exhibited intramolecular cyclization either in the presence of trifluoroacetic acid or N-iodosuccinimide (NIS) to afford azulene-substituted isocoumarins and 4-iodoisocoumarins, and the structures were clarified by single-crystal X-ray analysis.

Strain-induced skeletal rearrangement of a polycyclic aromatic hydrocarbon on a copper surface.

Controlling the structural deformation of organic molecules can drive unique reactions that cannot be induced only by thermal, optical or electrochemical procedures. However, in conventional organic synthesis, including mechanochemical procedures, it is difficult to control skeletal rearrangement in polycyclic aromatic hydrocarbons (PAHs). Here, we demonstrate a reaction scheme for the skeletal rearrangement of PAHs on a metal surface using high-resolution noncontact atomic force microscopy.

Synthesis of 2-amino- and 2-arylazoazulenes via nucleophilic aromatic substitution of 2-chloroazulenes with amines and arylhydrazines.

The SAr reaction of 2-chloroazulene derivative 1 with ethoxycarbonyl groups at the 1,3-positions of the azulene ring with several amines afforded the corresponding 2-aminoazulenes 3-9 in excellent yields. 2-Chloroazulene (2) without the electron-withdrawing groups reacted with highly nucleophilic cyclic amines (i.e.

Synthesis of 2-Aminofurans by Sequential [2+2] Cycloaddition-Nucleophilic Addition of 2-Propyn-1-ols with Tetracyanoethylene and Amine-Induced Transformation into 6-Aminopentafulvenes.

Synthesis of 2-aminofuran derivatives with an azulene or N,N-dimethylanilino substituent was established by the formal [2+2] cycloaddition-retroelectrocyclization of 3-(1-azulenyl or N,N-dimethylanilino)-2-propyn-1-ols with tetracyanoethylene, followed by intramolecular nucleophilic addition to the initially formed tetracyanobutadiene moiety of the internal hydroxyl group that come from 2-propyn-1-ol. The reaction proceeds under mild conditions with short reaction period. The products of the reaction are readily available through a simple purification procedure.

Synthesis of 2-Azulenyltetrathiafulvalenes by Palladium-Catalyzed Direct Arylation of 2-Chloroazulenes with Tetrathiafulvalene and Their Optical and Electrochemical Properties.

Tetrathiafulvalene (TTF) derivatives with 2-azulenyl substituents 5-11 were prepared by the palladium-catalyzed direct arylation reaction of 2-chloroazulenes with TTF in good yield. Photophysical properties of these compounds were investigated by UV-vis spectroscopy and theoretical calculations. Redox behavior of the novel azulene-substituted TTFs was examined by using cyclic voltammetry and differential pulse voltammetry, which revealed their multistep electrochemical oxidation and/or reduction properties.

Synthesis, Characterization, and Electronic Structures of Porphyrins Fused with Polycyclic Aromatic Ring Systems.

A series of porphyrins fused with acenaphthylene, phenanthroline, and benzofluoranthene polycyclic aromatic rings were prepared by means of a 3+1 porphyrin synthesis approach and subsequent retro-Diels-Alder reaction of bicyclo[2.2.2]octadiene-fused precursors.