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22 pages, 11901 KiB

Open AccessArticle

Towards Asymmetrical Methylene Blue Analogues: Synthesis and Reactivity of 3-N′-Arylaminophenothiazines

by Alena Khadieva, Mansur Rayanov, Ksenia Shibaeva, Alexandr Piskunov, Pavel Padnya and Ivan Stoikov

Molecules 2022, 27(9), 3024; https://doi.org/10.3390/molecules27093024 - 8 May 2022

Cited by 6 | Viewed by 3769

Abstract

The search for new ways to obtain analogues of the well-known Methylene Blue dye is an important synthetic task. Herein, we proposed and developed an approach to the synthesis of 3-N′-arylaminophenothiazines and asymmetrical 3,7-di(N′-arylamino)phenothiazines. This approach included the optimization [...] Read more.

The search for new ways to obtain analogues of the well-known Methylene Blue dye is an important synthetic task. Herein, we proposed and developed an approach to the synthesis of 3-N′-arylaminophenothiazines and asymmetrical 3,7-di(N′-arylamino)phenothiazines. This approach included the optimization of synthetic strategy by quantification analysis of the positive charge distribution in the cation of 3-N′-arylaminophenothiazine derivative. The obtained experimental data are confirmed by DFT studies. Two synthetic routes for asymmetrical phenothiazine diarylamino derivatives were suggested and verified. The developed convenient and versatile synthetic approach makes it easy to obtain aromatic Methylene Blue isostructural analogues with various substituents. As a result, a series of novel 3-N′-arylaminophenothiazines and asymmetrical 3,7-di(N′-arylamino)phenothiazines containing ester, tert-butoxycarbonyl, sulfonic acid, hydroxyl and amine groups were obtained in high yields. Full article

(This article belongs to the Special Issue Modern Trends in Heterocyclic Chemistry)

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16 pages, 2897 KiB

Open AccessArticle

New Unsymmetrically Substituted Benzothiadiazole-Based Luminophores: Synthesis, Optical, Electrochemical Studies, Charge Transport, and Electroluminescent Characteristics

by Pavel S. Gribanov, Dmitry A. Loginov, Dmitry A. Lypenko, Artem V. Dmitriev, Sergey I. Pozin, Alexey E. Aleksandrov, Alexey R. Tameev, Igor L. Martynov, Andrey Yu. Chernyadyev and Sergey N. Osipov

Molecules 2021, 26(24), 7596; https://doi.org/10.3390/molecules26247596 - 15 Dec 2021

Cited by 9 | Viewed by 3298

Abstract

Three new benzothiadiazole (BTD)-containing luminophores with different configurations of aryl linkers have been prepared via Pd-catalyzed cross-coupling Suzuki and Buchwald–Hartwig reactions. Photophysical and electroluminescent properties of the compounds were investigated to estimate their potential for optoelectronic applications. All synthesized structures have sufficiently high [...] Read more.

Three new benzothiadiazole (BTD)-containing luminophores with different configurations of aryl linkers have been prepared via Pd-catalyzed cross-coupling Suzuki and Buchwald–Hartwig reactions. Photophysical and electroluminescent properties of the compounds were investigated to estimate their potential for optoelectronic applications. All synthesized structures have sufficiently high quantum yields in film. The BTD with aryl bridged carbazole unit demonstrated the highest electrons and holes mobility in a series. OLED with light-emitting layer (EML) based on this compound exhibited the highest brightness, as well as current and luminous efficiency. The synthesized compounds are not only luminophores with a high photoluminescence quantum yield, but also active transport centers for charge carriers in EML of OLED devices. Full article

(This article belongs to the Special Issue Modern Trends in Heterocyclic Chemistry)

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15 pages, 19548 KiB

Open AccessArticle

4-Azidocinnoline—Cinnoline-4-amine Pair as a New Fluorogenic and Fluorochromic Environment-Sensitive Probe

by Natalia A. Danilkina, Ekaterina V. Andrievskaya, Anna V. Vasileva, Anna G. Lyapunova, Andrey M. Rumyantsev, Andrey A. Kuzmin, Elena A. Bessonova and Irina A. Balova

Molecules 2021, 26(24), 7460; https://doi.org/10.3390/molecules26247460 - 9 Dec 2021

Cited by 5 | Viewed by 2885

Abstract

A new type of fluorogenic and fluorochromic probe based on the reduction of weakly fluorescent 4-azido-6-(4-cyanophenyl)cinnoline to the corresponding fluorescent cinnoline-4-amine was developed. We found that the fluorescence of 6-(4-cyanophenyl)cinnoline-4-amine is strongly affected by the nature of the solvent. The fluorogenic effect for [...] Read more.

A new type of fluorogenic and fluorochromic probe based on the reduction of weakly fluorescent 4-azido-6-(4-cyanophenyl)cinnoline to the corresponding fluorescent cinnoline-4-amine was developed. We found that the fluorescence of 6-(4-cyanophenyl)cinnoline-4-amine is strongly affected by the nature of the solvent. The fluorogenic effect for the amine was detected in polar solvents with the strongest fluorescence increase in water. The environment-sensitive fluorogenic properties of cinnoline-4-amine in water were explained as a combination of two types of fluorescence mechanisms: aggregation-induced emission (AIE) and excited state intermolecular proton transfer (ESPT). The suitability of an azide–amine pair as a fluorogenic probe was tested using a HepG2 hepatic cancer cell line with detection by fluorescent microscopy, flow cytometry, and HPLC analysis of cells lysates. The results obtained confirm the possibility of the transformation of the azide to amine in cells and the potential applicability of the discovered fluorogenic and fluorochromic probe for different analytical and biological applications in aqueous medium. Full article

(This article belongs to the Special Issue Modern Trends in Heterocyclic Chemistry)

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17 pages, 4862 KiB

Open AccessArticle

Convenient Synthesis of Benziodazolone: New Reagents for Direct Esterification of Alcohols and Amidation of Amines

by Michael T. Shea, Gregory T. Rohde, Yulia A. Vlasenko, Pavel S. Postnikov, Mekhman S. Yusubov, Viktor V. Zhdankin, Akio Saito and Akira Yoshimura

Molecules 2021, 26(23), 7355; https://doi.org/10.3390/molecules26237355 - 3 Dec 2021

Cited by 4 | Viewed by 2893

Abstract

Hypervalent iodine heterocycles represent one of the important classes of hypervalent iodine reagents with many applications in organic synthesis. This paper reports a simple and convenient synthesis of benziodazolones by the reaction of readily available iodobenzamides with m-chloroperoxybenzoic acid in acetonitrile at [...] Read more.

Hypervalent iodine heterocycles represent one of the important classes of hypervalent iodine reagents with many applications in organic synthesis. This paper reports a simple and convenient synthesis of benziodazolones by the reaction of readily available iodobenzamides with m-chloroperoxybenzoic acid in acetonitrile at room temperature. The structure of one of these new iodine heterocycles was confirmed by X-ray analysis. In combination with PPh₃ and pyridine, these benziodazolones can smoothly react with alcohols or amines to produce the corresponding esters or amides of 3-chlorobenzoic acid, respectively. It was found that the novel benziodazolone reagent reacts more efficiently than the analogous benziodoxolone reagent in this esterification. Full article

(This article belongs to the Special Issue Modern Trends in Heterocyclic Chemistry)

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16 pages, 1766 KiB

Open AccessArticle

Amination of 5-Spiro-Substituted 3-Hydroxy-1,5-dihydro-2H-pyrrol-2-ones

by Ekaterina E. Khramtsova, Ekaterina A. Lystsova, Evgeniya V. Khokhlova, Maksim V. Dmitriev and Andrey N. Maslivets

Molecules 2021, 26(23), 7179; https://doi.org/10.3390/molecules26237179 - 26 Nov 2021

Cited by 2 | Viewed by 1997

Abstract

The 3-hydroxy-1,5-dihydro-2H-pyrrol-2-one motif is a valuable scaffold in drug discovery. The replacement of the 3-oxy fragment in 3-hydroxy-1,5-dihydro-2H-pyrrol-2-ones-based compounds with a 3-amino one (3-amino analogs of 3-hydroxy-1,5-dihydro-2H-pyrrol-2-ones, 3-amino-1,5-dihydro-2H-pyrrol-2-ones) can play a crucial role in their [...] Read more.

The 3-hydroxy-1,5-dihydro-2H-pyrrol-2-one motif is a valuable scaffold in drug discovery. The replacement of the 3-oxy fragment in 3-hydroxy-1,5-dihydro-2H-pyrrol-2-ones-based compounds with a 3-amino one (3-amino analogs of 3-hydroxy-1,5-dihydro-2H-pyrrol-2-ones, 3-amino-1,5-dihydro-2H-pyrrol-2-ones) can play a crucial role in their biological effect. Thus, approaches to 3-amino-1,5-dihydro-2H-pyrrol-2-ones are of significant interest. We developed an approach to 5-spiro-substituted 3-amino-1,5-dihydro-2H-pyrrol-2-ones that could not be obtained using previously reported approaches (reactions of 3-hydroxy-1,5-dihydro-2H-pyrrol-2-ones with amines). The developed approach is based on the thermal decomposition of 1,3-disubstituted urea derivatives of 5-spiro-substituted 3-hydroxy-1,5-dihydro-2H-pyrrol-2-ones, which were prepared via their reaction with carbodiimides. Full article

(This article belongs to the Special Issue Modern Trends in Heterocyclic Chemistry)

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14 pages, 4165 KiB

Open AccessArticle

Hetero-Type Benzannulation Leading to Substituted Benzothio-Phenes

by Taro Kono, Ryosuke Sasaki, Hideki Goto, Masatoshi Kakuno and Yoo Tanabe

Molecules 2021, 26(22), 7008; https://doi.org/10.3390/molecules26227008 - 19 Nov 2021

Viewed by 2052

Abstract

TiCl₄ (or SnCl₄)-promoted hetero-type benzannulation reactions using various (2,2-dichlorocyclopropyl)(thiophen-2-yl)methanols proceeded smoothly to produce uniquely substituted 4-chlorobenzothiophenes (five examples). The present approach involves the first distinctive thiophene formation from thiophene cores, in contrast to traditional methods of thiophene formation from benzene [...] Read more.

TiCl₄ (or SnCl₄)-promoted hetero-type benzannulation reactions using various (2,2-dichlorocyclopropyl)(thiophen-2-yl)methanols proceeded smoothly to produce uniquely substituted 4-chlorobenzothiophenes (five examples). The present approach involves the first distinctive thiophene formation from thiophene cores, in contrast to traditional methods of thiophene formation from benzene cores. The stereocongested (less reactive) Cl position in the obtained 4-chlorobenzothiophenes functioned successfully as the partners of three cross-coupling reactions: (i) a Suzuki–Miyaura cross-couplings using Pd(OAc)₂/SPhos/K₃PO₄ catalysis (seven examples; 63–91%), (ii) a hydroxylation using KOH/Pd(dba)₂/tBu-XPhos catalysis (85%), and (iii) a borylation using a B₂(pin)₂/Pd(dba)₂/XPhos/NaOAc catalysis-provided 4-(pin)B-benzothiophene (58%). Full article

(This article belongs to the Special Issue Modern Trends in Heterocyclic Chemistry)

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14 pages, 3076 KiB

Open AccessArticle

Design and Synthesis of New 5-aryl-4-Arylethynyl-1H-1,2,3-triazoles with Valuable Photophysical and Biological Properties

by Mariia M. Efremova, Anastasia I. Govdi, Valeria V. Frolova, Andrey M. Rumyantsev and Irina A. Balova

Molecules 2021, 26(9), 2801; https://doi.org/10.3390/molecules26092801 - 10 May 2021

Cited by 13 | Viewed by 2464

Abstract

Cu-catalyzed 1,3-dipolar cycloaddition of methyl 2-azidoacetate to iodobuta-1,3-diynes and subsequent Suzuki-Miyaura cross-coupling were used to synthesize new triazoles derivatives: 5-aryl-4-arylethynyl-1H-1,2,3-triazoles. Investigation of their optical properties by using UV absorption and fluorescence emission spectroscopies revealed that all molecules possess fluorescence properties with [...] Read more.

Cu-catalyzed 1,3-dipolar cycloaddition of methyl 2-azidoacetate to iodobuta-1,3-diynes and subsequent Suzuki-Miyaura cross-coupling were used to synthesize new triazoles derivatives: 5-aryl-4-arylethynyl-1H-1,2,3-triazoles. Investigation of their optical properties by using UV absorption and fluorescence emission spectroscopies revealed that all molecules possess fluorescence properties with the values of the Stokes shift more than 100 nm. The photophysical behavior of the two most promising triazoles in polar and non-polar solvents was also studied. Full article

(This article belongs to the Special Issue Modern Trends in Heterocyclic Chemistry)

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11 pages, 2656 KiB

Open AccessCommunication

Stereoselective Synthesis of Selenium-Containing Glycoconjugates via the Mitsunobu Reaction

by Luigia Serpico, Mauro De Nisco, Flavio Cermola, Michele Manfra and Silvana Pedatella

Molecules 2021, 26(9), 2541; https://doi.org/10.3390/molecules26092541 - 27 Apr 2021

Cited by 4 | Viewed by 2872

Abstract

A simple and efficient route for the synthesis of new glycoconjugates has been developed. The approach acts as a model for a mini-library of compounds with a deoxy-selenosugar core joined to a polyphenolic moiety with well-known antioxidant properties. An unexpected stereocontrol detected in [...] Read more.

A simple and efficient route for the synthesis of new glycoconjugates has been developed. The approach acts as a model for a mini-library of compounds with a deoxy-selenosugar core joined to a polyphenolic moiety with well-known antioxidant properties. An unexpected stereocontrol detected in the Mitsunobu key reaction led to the most attractive product showing a natural d-configuration. Thus, we were able to obtain the target molecules from the commercially available d-ribose via a shorter and convenient sequence of reactions. Full article

(This article belongs to the Special Issue Modern Trends in Heterocyclic Chemistry)

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13 pages, 2584 KiB

Open AccessArticle

Structure, Z′ = 2 Crystal Packing Features of 3-(2-Chlorobenzylidene)-5-(p-tolyl)furan-2(3H)-one

by Vyacheslav S. Grinev, Oksana A. Mayorova, Tatyana V. Anis’kova, Alexandra S. Tikhomolova and Alevtina Yu. Yegorova

Molecules 2021, 26(8), 2137; https://doi.org/10.3390/molecules26082137 - 8 Apr 2021

Cited by 1 | Viewed by 1871

Abstract

3-(2-Chlorobenzylidene)-5-(p-tolyl)furan-2(3H)-one (1), C₁₈H₁₃ClO₂, crystallizes with Z = 8 and Z′ = 2, and the structure at 100 K has orthorhombic (Pna2₁) symmetry. Each kind of molecule takes [...] Read more.

3-(2-Chlorobenzylidene)-5-(p-tolyl)furan-2(3H)-one (1), C₁₈H₁₃ClO₂, crystallizes with Z = 8 and Z′ = 2, and the structure at 100 K has orthorhombic (Pna2₁) symmetry. Each kind of molecule takes part in π–π stacking interactions to form infinite chains parallel to the c axis. We believe that the existence of two forms can be explained by the probable rotation around a single C–C bond. The quantum chemical modeling reveals that these molecules are almost equivalent energetically, and they can be described as the two most stable conformers (rotamers) with a minor rotational barrier of about 0.67 kcal/mol. Full article

(This article belongs to the Special Issue Modern Trends in Heterocyclic Chemistry)

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11 pages, 1762 KiB

Open AccessCommunication

Synthesis, Structural Characterization, and Optical Properties of Benzene-Fused Tetracyclic and Pentacyclic Stiboles

by Mio Matsumura, Yuki Matsuhashi, Masato Kawakubo, Tadashi Hyodo, Yuki Murata, Masatoshi Kawahata, Kentaro Yamaguchi and Shuji Yasuike

Molecules 2021, 26(1), 222; https://doi.org/10.3390/molecules26010222 - 4 Jan 2021

Cited by 12 | Viewed by 3679

Abstract

The expectation that antimony (Sb) compounds should display phosphorescence emissions based on the “heavy element effect” prompted our interest in the introduction of antimony to a biaryl as the bridging atom in a fused heterole system. Herein, the synthesis, molecular structures, and optical [...] Read more.

The expectation that antimony (Sb) compounds should display phosphorescence emissions based on the “heavy element effect” prompted our interest in the introduction of antimony to a biaryl as the bridging atom in a fused heterole system. Herein, the synthesis, molecular structures, and optical properties of novel benzene-fused heteroacenes containing antimony or arsenic atoms are described. The stiboles and arsole were prepared by the condensation of dibromo(phenyl)stibane or dichloro(phenyl)arsine with dilithium intermediates derived from the corresponding dibromo compounds. Nuclear magnetic resonance (NMR) spectroscopy and X-ray crystal analysis revealed that the linear pentacyclic stibole was highly symmetric in both the solution and crystal states. In contrast, the curved pentacyclic stibole adopted a helical structure in solution, and surprisingly, only M helical molecules were crystallized from the racemate. All synthesized compounds produced very weak or no emissions at room temperature or in the solid state. In contrast, the linear penta- and tetracyclic stiboles exhibited clear phosphorescence emissions in the CHCl₃ frozen matrix at 77 K under aerobic conditions. Full article

(This article belongs to the Special Issue Modern Trends in Heterocyclic Chemistry)

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12 pages, 4471 KiB

Open AccessArticle

Sterically Facilitated Intramolecular Nucleophilic NMe₂ Group Substitution in the Synthesis of Fused Isoxazoles: Theoretical Study

by Alexander S. Antonov, Elena Yu Tupikina, Valerii V. Karpov, Valeriia V. Mulloyarova and Victor G. Bardakov

Molecules 2020, 25(24), 5977; https://doi.org/10.3390/molecules25245977 - 17 Dec 2020

Cited by 2 | Viewed by 2653

Abstract

The influence of steric repulsion between the NMe₂ group and a second ortho-(peri-)substituent in the series of 1-dimethylaminonaphthalene and N,N-dimethylanilene ortho-oximes on the ease of the NMe₂ group’s intramolecular nucleophilic substitution is studied. Possible [...] Read more.

The influence of steric repulsion between the NMe₂ group and a second ortho-(peri-)substituent in the series of 1-dimethylaminonaphthalene and N,N-dimethylanilene ortho-oximes on the ease of the NMe₂ group’s intramolecular nucleophilic substitution is studied. Possible reaction intermediates for three mechanisms are calculated (ωB97xd/def-2-TZVP), and their free Gibbs energies are compared to model reaction profiles. Supporting experiments have proved the absence of studied reactivity in the case of simple 2-dimethylaminobenzaldoxime, which allowed us to establish reactivity limits. The significant facilitation of NMe₂ group displacement in the presence of bulky substituents is demonstrated. The possibility of fused isoxazoles synthesis via the intramolecular nucleophilic substitution of a protonated NMe₂ group in the aniline and naphthalene series is predicted. Full article

(This article belongs to the Special Issue Modern Trends in Heterocyclic Chemistry)

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Review

Jump to: Research

35 pages, 11553 KiB

Open AccessReview

Heteroelement Analogues of Benzoxaborole and Related Ring Expanded Systems

by Krzysztof Nowicki, Piotr Pacholak and Sergiusz Luliński

Molecules 2021, 26(18), 5464; https://doi.org/10.3390/molecules26185464 - 8 Sep 2021

Cited by 6 | Viewed by 3095

Abstract

The review covers the chemistry of organoboron heterocycles structurally related to benzoxaboroles where one of the carbon atoms in a boracycle or a fused benzene ring is replaced by a heteroelement such as boron, silicon, tin, nitrogen, phosphorus, or iodine. Related ring expanded [...] Read more.

The review covers the chemistry of organoboron heterocycles structurally related to benzoxaboroles where one of the carbon atoms in a boracycle or a fused benzene ring is replaced by a heteroelement such as boron, silicon, tin, nitrogen, phosphorus, or iodine. Related ring expanded systems including those based on naphthalene and biphenyl cores are also described. The information on synthetic methodology as well as the basic structural and physicochemical characteristics of these emerging heterocycles is complemented by a presentation of their potential applications in organic synthesis and medicinal chemistry, the latter aspect being mostly focused on the promising antimicrobial activity of selected compounds. Full article

(This article belongs to the Special Issue Modern Trends in Heterocyclic Chemistry)

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31 pages, 20925 KiB

Open AccessReview

New Trends in Diaziridine Formation and Transformation (a Review)

by Zetryana Puteri Tachrim, Lei Wang, Yuta Murai and Makoto Hashimoto

Molecules 2021, 26(15), 4496; https://doi.org/10.3390/molecules26154496 - 26 Jul 2021

Cited by 7 | Viewed by 6695

Abstract

This review focuses on diaziridine, a high strained three-membered heterocycle with two nitrogen atoms that plays an important role as one of the most important precursors of diazirine photoaffinity probes, as well as their formation and transformation. Recent research trends can be grouped [...] Read more.

This review focuses on diaziridine, a high strained three-membered heterocycle with two nitrogen atoms that plays an important role as one of the most important precursors of diazirine photoaffinity probes, as well as their formation and transformation. Recent research trends can be grouped into three categories, based on whether they have examined non-substituted, N-monosubstituted, or N,N-disubstituted diaziridines. The discussion expands on the conventional methods for recent applications, the current spread of studies, and the unconventional synthesis approaches arising over the last decade of publications. Full article

(This article belongs to the Special Issue Modern Trends in Heterocyclic Chemistry)

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