Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes

• Michio Yamada

Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13

• Michio Yamada Department of Chemistry, Tokyo Gakugei University, Nukuikitamachi 4-1-1, Koganei, Tokyo 184-8501, Japan 10.3762/bjoc.20.13 Abstract Various push–pull chromophores can be synthesized in a single and atom-economical step through [2 + 2] cycloaddition–retroelectrocyclization (CA–RE

• ) reactions involving diverse electron-rich alkynes and electron-deficient alkenes. In this review, a comprehensive investigation of the recent and noteworthy advancements in the research on push–pull chromophores prepared via the [2 + 2] CA–RE reaction is conducted. In particular, an overview of the

• physicochemical properties of the family of these compounds that have been investigated is provided to clarify their potential for future applications. Keywords: click chemistry; donor–acceptor conjugate; intramolecular charge transfer; photoluminescence; photoinduced electron transfer; Introduction Push–pull

Multi-redox indenofluorene chromophores incorporating dithiafulvene donor and ene/enediyne acceptor units

• Christina Schøttler,
• Kasper Lund-Rasmussen,
• Line Broløs,
• Philip Vinterberg,
• Ema Bazikova,
• Viktor B. R. Pedersen and
• Mogens Brøndsted Nielsen

Beilstein J. Org. Chem. 2024, 20, 59–73, doi:10.3762/bjoc.20.8

• –acceptor “push–pull” system is present (albeit a broad tail to the absorption is observed), in contrast to 22 and 23. The absorption maxima of compound 26 are significantly blueshifted, presumably due to the smaller conjugated system. The same trend with a shorter longest-wavelength absorption maximum that

A deep-red fluorophore based on naphthothiadiazole as emitter with hybridized local and charge transfer and ambipolar transporting properties for electroluminescent devices

• Suangsiri Arunlimsawat,
• Patteera Funchien,
• Pongsakorn Chasing,
• Atthapon Saenubol,
• Taweesak Sudyoadsuk and
• Vinich Promarak

Beilstein J. Org. Chem. 2023, 19, 1664–1676, doi:10.3762/bjoc.19.122

• . It has been reported that the performance of HLCT fluorophores greatly depends on the strength of donors, acceptors, and π spacers and the building blocks of HLCT should be carefully selected to regulate appropriate electron push–pull strength [32][35][47][48]. Here, a novel chromophore, 4,9-bis(9-(4

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• atom(s) or another heteroatom into the vacant p-orbital (LUMO) at the carbene carbon atom (Figure 2). In fact, the donation of lone pair electrons to the carbenic center leads to an ylidic structure which induces a “push–pull” effect thereby enhancing the stability of the NHC. The cyclic structure of

Synthesis, structure, and properties of switchable cross-conjugated 1,4-diaryl-1,3-butadiynes based on 1,8-bis(dimethylamino)naphthalene

• Semyon V. Tsybulin,
• Ekaterina A. Filatova,
• Alexander F. Pozharskii,
• Valery A. Ozeryanskii and
• Anna V. Gulevskaya

Beilstein J. Org. Chem. 2023, 19, 674–686, doi:10.3762/bjoc.19.49

• ]. In the present work we describe the synthesis of a new family of proton sponge-based butadiynes 5 bearing arylethynyl substituents of different electronic nature. Oligomers 5 having electron-withdrawing groups on the aryl termini are interesting as push–pull A–π–D–π–D–π–A systems, whereas the

• monomers 6d and 6e are typical rod-like D–π–A systems. In such molecules, a photon absorption induces a shift from a D–π–A ground state to a D+–π–A− excited state. It is obvious that the actual electron transfer depends on all three components of the push–pull molecule. However, the study on the through

• , Figure 9). However, unlike salts 11a,c,d, methoxy derivative 11b demonstrates end absorption up to 415 nm and, thus, the lowest optical band gap in the series (2.99 eV). Evidently, protonation of 5b gives rise to a push–pull D–π–A–π–A–π–D system, in which the π-conjugation between the donating

Functionalization of imidazole N-oxide: a recent discovery in organic transformations

• Koustav Singha,
• Imran Habib and
• Mossaraf Hossain

Beilstein J. Org. Chem. 2022, 18, 1575–1588, doi:10.3762/bjoc.18.168

• perfluoroaryl-substituted 2H-imidazole products, a push–pull fluorophore system was discovered, which can be useful for the preparation of fluorometric sensor materials because of the solvent-dependent intramolecular charge transfer effect (ICT). Here, two reaction pathways were designed: (A) addition

Syntheses of novel pyridine-based low-molecular-weight luminogens possessing aggregation-induced emission enhancement (AIEE) properties

• Masayori Hagimori,
• Tatsusada Yoshida,
• Yasuhisa Nishimura,
• Yukiko Ogawa and
• Keitaro Tanaka

Beilstein J. Org. Chem. 2022, 18, 580–587, doi:10.3762/bjoc.18.60

• molecules, indicating that fluorescence properties of N-methyl-4-((pyridin-2-yl)amino)-substituted maleimides could be modulated by the electron push–pull effect of substituents. The AIEE properties of products 3a,b, and 4a–e were evaluated in different EtOH/H2O (v/v) solvent mixtures (Table 3 and Figure

Chemistry of polyhalogenated nitrobutadienes, 17: Efficient synthesis of persubstituted chloroquinolinyl-1H-pyrazoles and evaluation of their antimalarial, anti-SARS-CoV-2, antibacterial, and cytotoxic activities

• Viktor A. Zapol’skii,
• Isabell Berneburg,
• Ursula Bilitewski,
• Melissa Dillenberger,
• Katja Becker,
• Stefan Jungwirth,
• Aditya Shekhar,
• Bastian Krueger and
• Dieter E. Kaufmann

Beilstein J. Org. Chem. 2022, 18, 524–532, doi:10.3762/bjoc.18.54

• synthesized, push–pull-substituted pyrazoles with the monosubstituted parent system, 11 was synthesized in 34% yield according to the literature [18] (Scheme 8). This proceeding corresponds well with our earlier publications on the microbiological activity of highly substituted pyrazoles [30][31][32][33

Photophysical, photostability, and ROS generation properties of new trifluoromethylated quinoline-phenol Schiff bases

• Inaiá O. Rocha,
• Yuri G. Kappenberg,
• Wilian C. Rosa,
• Clarissa P. Frizzo,
• Nilo Zanatta,
• Marcos A. P. Martins,
• Isadora Tisoco,
• Bernardo A. Iglesias and
• Helio G. Bonacorso

Beilstein J. Org. Chem. 2021, 17, 2799–2811, doi:10.3762/bjoc.17.191

• = Ph, R1 = 4-NO2) were analyzed, a significant difference was observed compared to the other compounds in the series 3. Thus, we can say that these characteristics exist because there is more stabilization of the excited state in a polar environment (DMSO and MeOH), adding to a possible push–pull

• electron-donating groups (push–pull system). As in the aminoquinolines described in the literature [14], the Schiff base derivatives present emission spectra in a different region to the amino derivatives (blue to green region), but with higher quantum fluorescence yields and Stokes shifts, a fact

Silica gel and microwave-promoted synthesis of dihydropyrrolizines and tetrahydroindolizines from enaminones

• Robin Klintworth,
• Garreth L. Morgans,
• Stefania M. Scalzullo,
• Charles B. de Koning,
• Willem A. L. van Otterlo and
• Joseph P. Michael

Beilstein J. Org. Chem. 2021, 17, 2543–2552, doi:10.3762/bjoc.17.170

• enaminone acts as an intramolecular nucleophile towards the phenacyl substituent, even though the nucleophilic character of the enamine component is expected to be suppressed by the “push–pull” effect arising from the electron-withdrawing carbonyl group [19][20][21][22][23]. The dual properties of

• prior to acid-promoted cyclization cannot be ruled out, since conjugation in the push–pull system should weaken the C=C bond and lower its rotational barrier [20]. Similar enaminone isomerizations have been detected even at room temperature [48]. If thermal isomerization indeed takes place, then one

[2 + 1] Cycloaddition reactions of fullerene C₆₀ based on diazo compounds

• Yuliya N. Biglova

Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55

• such an electron-enriched metal-containing system to C60 can result in push–pull blocks with new electronic and photochemical properties, as demonstrated by complexes 63, 64 [103], and 65 [104] in Figure 6. The syntheses of new types of N-containing fullerene ligands for metal complexes 66–68 are

Naphthalonitriles featuring efficient emission in solution and in the solid state

• Sidharth Thulaseedharan Nair Sailaja,
• Iván Maisuls,
• Jutta Kösters,
• Alexander Hepp,
• Andreas Faust,
• Jens Voskuhl and
• Cristian A. Strassert

Beilstein J. Org. Chem. 2020, 16, 2960–2970, doi:10.3762/bjoc.16.246

• easy conversion into naphthalocyanines. Hence, peripherally substituted naphthalocyanines with push–pull character found widespread applications in non-lineal-optics (NLO) [36], photodynamic therapy [37] and photoacoustic imaging [38]. However, up to date, the literature reveals that there are no

• ) character (n–π*) of the excited state. Due to sterical hindrance, the two adjacent phenyl rotors restrict their molecular rotation in solution. The increasing push–pull (D–A) character progressively enhances the coupling with solvent molecules and sensitivity to changes in the dielectric constant when going

• , we observe a drastic drop in quantum yield when the water fractions are raised from 0% to 30%. As NMe2 is a pure push–pull system, the excited state can interact strongly with the solvent and due to the high polarity of water, a solvent quenching (SQ) effect is expected and also explains the observed

Styryl-based new organic chromophores bearing free amino and azomethine groups: synthesis, photophysical, NLO, and thermal properties

• Anka Utama Putra,
• Deniz Çakmaz,
• Nurgül Seferoğlu,
• Alberto Barsella and
• Zeynel Seferoğlu

Beilstein J. Org. Chem. 2020, 16, 2282–2296, doi:10.3762/bjoc.16.189

• Optics and Nanophotonics, IPCMS, UMR CNRS, 7504, 67034 Strasbourg Cedex 2, France 10.3762/bjoc.16.189 Abstract Herein we report the synthesis and characterization of a new series of styryl-based push-pull dyes containing a free amino group and their Schiff base derivatives. The dyes include the

• all dyes were evaluated by thermogravimetric analysis (TGA). The TGA data showed that all dyes were thermally stable up to 250 °C. Keywords: DFT calculations; NLO; pH sensitive dyes; Schiff base; solvent effect; styryl dyes; Introduction Push-pull organic molecules are a class of organic dyes

• ][12][13][14]. Among dyestuffs classes, the push-pull fluorescent dyes are renowned to own such special behaviors. The push-pull dyes generate higher charge delocalization upon excitation, thus enhance both polarizability and fluorescence emission [12][13][14][18]. The charge delocalization upon

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• : a biradical capable of abstracting an H atom from C–H bonds. Recently, Martin exploited this feature in a nickel-catalyzed process for the alkylation of arenes (Scheme 8) [57]. In this report, the excited state of a push–pull benzophenone OD10 can abstract an H atom from the substrate

Reversible switching of arylazopyrazole within a metal–organic cage

• Anton I. Hanopolskyi,
• Soumen De,
• Michał J. Białek,
• Yael Diskin-Posner,
• Liat Avram,
• Moran Feller and
• Rafal Klajn

Beilstein J. Org. Chem. 2019, 15, 2398–2407, doi:10.3762/bjoc.15.232

• (Figure 8c, step i). Coordination of Pd2+ to the azo moiety, combined with the strongly electron-donating pyrazole moiety, affords (Figure 8c, step ii) a system akin to push–pull azobenzenes, whose Z isomers can back-isomerize rapidly due to a reduced order of the N=N bond [52][53][54] (Figure 8c, step

Isolation and characterisation of irinans, androstane-type withanolides from Physalis peruviana L.

• Annika Stein,
• Dave Compera,
• Bianka Karge,
• Mark Brönstrup and
• Jakob Franke

Beilstein J. Org. Chem. 2019, 15, 2003–2012, doi:10.3762/bjoc.15.196

• -oxidative Grob fragmentation could make use of a push–pull mechanism between C-17 and C-22, building on acid–base catalysis. Alternatively, an enzyme could cleave the C17–C20 diol oxidatively. Several P450 enzymes have been reported to be capable of cleaving diols, presumably via a ferric peroxo

Functional panchromatic BODIPY dyes with near-infrared absorption: design, synthesis, characterization and use in dye-sensitized solar cells

• Quentin Huaulmé,
• Cyril Aumaitre,
• Outi Vilhelmiina Kontkanen,
• David Beljonne,
• Alexandra Sutter,
• Gilles Ulrich,
• Renaud Demadrille and
• Nicolas Leclerc

Beilstein J. Org. Chem. 2019, 15, 1758–1768, doi:10.3762/bjoc.15.169

• phthalocyanines [10][11], organic push–pull compounds [12], and boron-dipyrromethene [13] (BODIPY®). BODIPY dyes are one of the most extensively studied class of fluorophores due to their unique properties, including high absorption coefficients in the visible and NIR ranges, high fluorescence quantum yields, and

Synthesis of ([1,2,4]triazolo[4,3-a]pyridin-3-ylmethyl)phosphonates and their benzo derivatives via 5-exo-dig cyclization

• Aleksandr S. Krylov,
• Artem A. Petrosian,
• Julia L. Piterskaya,
• Nataly I. Svintsitskaya and
• Albina V. Dogadina

Beilstein J. Org. Chem. 2019, 15, 1563–1568, doi:10.3762/bjoc.15.159

• ; Introduction Due to the high polarization of the push–pull triple bond, haloacetylenes show high reactivity in nucleophilic substitution reactions. Our systematic studies of the reactions of chloroethynylphosphonates with various nucleophilic reagents have recently revealed a new direction of this reaction

Synthesis of dipolar molecular rotors as linkers for metal-organic frameworks

• Sebastian Hamer,
• Fynn Röhricht,
• Marius Jakoby,
• Ian A. Howard,
• Xianghui Zhang,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1331–1338, doi:10.3762/bjoc.15.132

• molecules. Four rotors are fluorescent in the visible region. The linker designs are based on push–pull-substituted phenylene cores with ethynyl spacers as rotational axes, functionalized with carboxylic acid groups for implementation in MOFs. The substituents at the phenylene core are chosen to be small to

• , conversion into the respective dicarboxylic acids 4 and 5 took place by reaction with cesium fluoride under a carbon dioxide atmosphere. Conclusion In summary, we reported here the synthesis of five dipolar rotors consisting of a push–pull-substituted phenylene core, with two ethynyl units in para-position

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• . First of all, the azacrown nitrogen atom is linked directly to the dye and it is part of the chromophore system, responsible for the “push–pull” effect and the photophysical properties of the dye. This provides control over the “push–pull” effect in the chromophore by switching on and off states (i.e

Diaminoterephthalate–α-lipoic acid conjugates with fluorinated residues

• Leon Buschbeck,
• Aleksandra Markovic,
• Gunther Wittstock and
• Jens Christoffers

Beilstein J. Org. Chem. 2019, 15, 981–991, doi:10.3762/bjoc.15.96

• primary amine 8 was coupled with ALA in the presence of COMU–DIPEA to furnish the second title compound 7 in 68% yield. Indeed, a bathochromic shift of the spectral data was observed (absorption at 514 nm and emission at 566 nm). Spectroscopy. Being typical push–pull aromatic systems, all DAT derivatives

Synthesis and fluorescent properties of N(9)-alkylated 2-amino-6-triazolylpurines and 7-deazapurines

• Andrejs Šišuļins,
• Jonas Bucevičius,
• Yu-Ting Tseng,
• Irina Novosjolova,
• Kaspars Traskovskis,
• Ērika Bizdēna,
• Huan-Tsung Chang,
• Sigitas Tumkevičius and
• Māris Turks

Beilstein J. Org. Chem. 2019, 15, 474–489, doi:10.3762/bjoc.15.41

• transformed into the title compounds by CuAAC reaction. The designed compounds belong to the push–pull systems and possess promising fluorescence properties with quantum yields in the range from 28% to 60% in acetonitrile solution. Due to electron-withdrawing properties of purine and 7-deazapurine

• to increased fluorescence quantum yield (74%) in THF solution. The compounds exhibit low cytotoxicity and as such are useful for the cell labelling studies in the future. Keywords: 7-deazapurines; fluorescence; nucleophilic aromatic substitution; purines; push–pull systems; pyrrolo[2,3-d]pyrimidines

• ; Introduction Purine [1][2][3][4][5][6][7] and 7-deazapurine (IUPAC name: pyrrolo[2,3-d]pyrimidine) [8][9][10][11] derivatives have been progressively studied for decades due to their wide range of biological activities and photophysical properties. Currently, the synthesis of push–pull systems is a promising

Development of a fluorogenic small substrate for dipeptidyl peptidase-4

• Futa Ogawa,
• Masanori Takeda,
• Kanae Miyanaga,
• Keita Tani,
• Ryuji Yamazawa,
• Kiyoshi Ito,
• Atsushi Tarui,
• Kazuyuki Sato and
• Masaaki Omote

Beilstein J. Org. Chem. 2017, 13, 2690–2697, doi:10.3762/bjoc.13.267

• push–pull system, which has a single benzene ring substituted by both electron-donating and electron-withdrawing groups [15][16][17]. We focused on the 3,3,3-trifluoropropenyl (TFPE) group, which is an electron-withdrawing substituent that is free of oxygen atoms, which would form hydrogen bonds in

• fluorescence push–pull system would be destroyed. To confirm this, we modified 1 to provide a peptidic substrate for an enzyme. The serine protease DPP-4 was used as the test enzyme because its substrate specificity is clear: it hydrolyses the C-terminal of proline or alanine second to the N-terminal of the

Structure–property relationships and third-order nonlinearities in diketopyrrolopyrrole based D–π–A–π–D molecules

• Jan Podlesný,
• Lenka Dokládalová,
• Oldřich Pytela,
• Adam Urbanec,
• Milan Klikar,
• Numan Almonasy,
• Tomáš Mikysek,
• Jaroslav Jedryka,
• Iwan V. Kityk and
• Filip Bureš

Beilstein J. Org. Chem. 2017, 13, 2374–2384, doi:10.3762/bjoc.13.235

• generation. The experimental data were completed by quantum-chemical calculations and structure–property relationships were elucidated. Keywords: calculations; diketopyrrolopyrrole; electrochemistry; electronic spectra; push–pull; third-harmonic generation; Introduction Known for more than 40 years

• investigated for DPP derivatives. The most common applications of organic molecules with THG activity are directed towards all-optical signal processing and optical imaging [30][31]. Hence, as a continuation of our research activity on incorporating heteroaromatic moieties in push–pull molecules [9][10], we

• -N,N’-dimethylaniline tetrathiafulvalene derivatives showed third-order nonlinear optical susceptibilities within a range of 20–32 pm2/V2 [40], whereas quinoline push-pull derivatives embedded in polymethylmethacrylate matrix possess a THG susceptibility equal to 46 pm2/V2 [41]. Reference inorganic

Syntheses of 3,4- and 1,4-dihydroquinazolines from 2-aminobenzylamine

• Jimena E. Díaz,
• Silvia Ranieri,
• Nadia Gruber and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2017, 13, 1470–1477, doi:10.3762/bjoc.13.145

• analogous reaction had been previously reported for 3,4-dihydroquinazolines upon exposure to air (Scheme 3, (b)) [19][24][40][66]. The fact that quinazolin-4(1H)-ones 6, which are fully conjugated push–pull molecules, are more resonance stabilized than their isomeric counterparts quinazolin-4(3H)-ones 7