Synthesis of azulenic compounds substituted in the 1-position with heterocycles

Razus, Alexandru C.; Bîrzan, Liviu

doi:10.1007/s00706-018-2294-8

Cited by 11 publications

(10 citation statements)

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“…Two reviews on the synthesis of azulenes substituted with heterocyclic moieties were recently published [33,34]. Consequently, in this chapter only the syntheses of compounds with charged heterocycles will be briefly examines and attention will be paid to the consequences of their substitution with azulen-1-yl moieties.…”

Section: Charged Hetero-aryls Stabilized By Azulen-1-yl Moietiesmentioning

confidence: 99%

“…The reaction started from 2H-pyran-2-one and occurred as shown in Scheme 12 with good yields when R = Ph (36-45%) and only with 17% for R = Me [37,38]. The pyranylium salts were then used as valuable synthons for obtaining a series of pyridines and pyridinium salts [34]. The general pathway for the synthesis of pyridinium salts in two steps [39] was applied to the generation of salts substituted with azulen-1-yl moieties (Scheme 13) [38,40,41].…”

Section: Charged Hetero-aryls Stabilized By Azulen-1-yl Moietiesmentioning

confidence: 99%

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Azulene Moiety as Electron Reservoir in Positively Charged Systems; A Short Survey

Razus

2021

Symmetry

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The non-alternant aromatic azulene, an isomer of alternant naphthalene, differs from the latter in peculiar properties. The large polarization of the π-electron system over the seven and five rings gives to azulene electrophile property a pronounced tendency to donate electrons to an acceptor, substituted at azulene 1 position. This paper presents cases in which azulene transfers electrons to a suitable acceptor as methylium ions, positive charged heteroaromatics and examples of neutral molecules that can accept electrons. The proposed product synthesis was outlined and the expected electron transfer was highlighted by analyzing the NMR, UV-Vis spectra and the pKR+ values.

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Section: Charged Hetero-aryls Stabilized By Azulen-1-yl Moietiesmentioning

confidence: 99%

Section: Charged Hetero-aryls Stabilized By Azulen-1-yl Moietiesmentioning

confidence: 99%

Azulene Moiety as Electron Reservoir in Positively Charged Systems; A Short Survey

Razus

2021

Symmetry

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“…It has been assumed that the known synthesis steps of 2,6-disubstituted 4-(azulen-1-yl)pyrylium salts [2,3] could be adapted for the corresponding chalcogenopyrylium salts. The generation of these pyrylium salts includes the obtaining of 2,6-disubstituted pyran-4-ones, their transformation in the corresponding 4-chloropyrylium salts and finally the electrophilic reaction with azulenes.…”

Section: Synthesismentioning

confidence: 99%

4-(azulen-1-yl)-2,6-diphenylchalcogenopyrylium Perchlorates; Synthesis and Characterization

Bîrzan¹,

Cristea²,

Drăghici³

et al. 2020

Rev. Chim.

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2,6-Diphenyl substituted thio- and seleno-pyrylium salts with azulen-1-yl moieties in 4-position were prepared from phenylacetylene going through chalcogenopyrones and 4-chloro-chalcogenopyrylium salts as intermediates. The final step of synthesis involves the electrophile substitution in 1-position of azulenes with the obtained chloro-derivatives and the products isolation as stable perchlorates. The electronic and magnetic spectra of products are presented and compared with those of the corresponding pyrylium salts.

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“…Azulene, which is an isoelectronic isomer of naphthalene, is a parent nonalternant, nonbenzenoid aromatic hydrocarbon with 10 π electrons and a fused pentagon−heptagon (5−7 sides) ring‐pair structure. [ 1 ] As displayed in Figure a, the resonance structure of azulene comprises: 1) a negative pentagon structure with six π electrons and 2) a positive heptagon structure with six π electrons to achieve Hückel aromatic stabilization. Azulene has a large dipole moment of 1.08 D. [ 2 ] By contrast, naphthalene, which only contains two fused six‐membered rings, has a dipole moment of 0 D. Azulene, which was discovered and named by Piesse in 1863, has attracted considerable interest since its discovery in petroleum exploitation.…”

Section: Introductionmentioning

confidence: 99%

Azulene‐Based Molecules, Polymers, and Frameworks for Optoelectronic and Energy Applications

Huang

Zhao

et al. 2020

Small Methods

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has a large dipole moment of 1.08 D. [2] By contrast, naphthalene, which only contains two fused six-membered rings, has a dipole moment of 0 D. Azulene, which was discovered and named by Piesse in 1863, has attracted considerable interest since its discovery in petroleum exploitation. [3] In 1937, Plattner and Pfau published their pioneering report on the synthesis of azulene. [4] However, their method was not practical due to its low azulene yield. In the 1950s, Ziegler and Hafner formulated a highly efficient and practical method for synthesizing azulene and its derivatives. [5] Because azulene is difficult to synthesize and has a low natural abundance, research on azulene-based molecules and materials is less advanced relative to research on its isomer. Direct functionalization of 1-and/ or 3-positions is a common and effective method of producing azulene derivatives. However, direct functionalization of other positions is much harder, e.g., bromination of 6-and 1,3-positions, [6] nucleophilic addition to obtain 6-subsituted azulene, [7] borylation at 2-position, [8] arylation at the 2-position, [9] and so on. The electron distribution in the front-line molecular orbitals (MOs) must usually be considered when functionalizing azulene. Because of resonance delocalization, the oddnumbered position of azulene, which is electron-rich, easily reacts with electrophilic compounds. Among the odd-numbered azulene varieties, 1-and 3-azulene have the highest activity. [10] By Azulene has a considerably larger dipole moment than its isomer naphthalene; it also has unique physicochemical properties, including different reactivities on five-and seven-membered rings, a dark color, a narrow gap between the highest occupied molecular orbital and lowest unoccupied molecular orbital, and stimulus response. Although azulene was discovered more than 100 years ago, the use of azulene-based derivatives can be traced back to five centuries ago. Due to its unusual structure, azulene-based molecules and materials are widely used in various fields. However, studies on azulene-based materials have long been hindered by difficulties in the synthesis. Considerably fewer studies have been conducted on azulene-based derivatives than on naphthalene-based derivatives. This perspective paper mainly introduces recent reports on the synthesis of azulene-based aromatic molecules, conjugated polymers, and coordination polymers, in addition to azulene-based frameworks. The structure-property relationship, optoelectronic applications, and energy-related applications of azulene-based derivatives are reviewed, including their use in near-infrared absorption, organic field-effect transistors, organic solar cells, and microsupercapacitors.

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Synthesis of azulenic compounds substituted in the 1-position with heterocycles

Cited by 11 publications

References 53 publications

Azulene Moiety as Electron Reservoir in Positively Charged Systems; A Short Survey

Azulene Moiety as Electron Reservoir in Positively Charged Systems; A Short Survey

4-(azulen-1-yl)-2,6-diphenylchalcogenopyrylium Perchlorates; Synthesis and Characterization

Azulene‐Based Molecules, Polymers, and Frameworks for Optoelectronic and Energy Applications

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