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

Correlation of surface pressure and hue of planarizable push–pull chromophores at the air/water interface

• Frederik Neuhaus,
• Fabio Zobi,
• Gerald Brezesinski,
• Marta Dal Molin,
• Stefan Matile and
• Andreas Zumbuehl

Beilstein J. Org. Chem. 2017, 13, 1099–1105, doi:10.3762/bjoc.13.109

• fluorescent probes are an elegant solution to this problem but it requires first the establishment of a direct correlation between the membrane surface pressure and the induced color change of the probe. Here, we analyze planarizable dithienothiophene push–pull probes in a monolayer at the air/water interface

• ], and an indirect method of measuring the membrane pressure would only yield an averaged global value. What is needed is a probe that directly measures the local surface pressure in a single membrane leaflet. One solution to the problem are the planarizable push–pull probes that have been recently

• ]. Mechanical planarization in the ground state increases the conjugation of the push–pull system. As a result, the excitation (or absorption) maximum shifts up to 80 nm to the red [8]. An anionic headgroup is added to produce an amphiphile that self-assembles into monolayers and micelles and enters

Spectral and DFT studies of anion bound organic receptors: Time dependent studies and logic gate applications

• Srikala Pangannaya,
• Neethu Padinchare Purayil,
• Shweta Dabhi,
• Venu Mankad,
• Prafulla K. Jha,
• Satyam Shinde and
• Darshak R. Trivedi

Beilstein J. Org. Chem. 2017, 13, 222–238, doi:10.3762/bjoc.13.25

• oxygen atom. The enhancement of the ICT transition could be ascribed to a push–pull nature between the electron withdrawing –CN substituent and the conjugated system [39]. The appearance of a clear isosbestic point at 443 nm indicates the existence of a host–guest complex in the system. On the other hand

• efficient push–pull tendency existing in the host–guest interaction mechanism. The appearance of a clear isosbestic point at 500 nm clearly indicates the formation of the new complex. The complete disappearance of the absorbance at 459 nm at higher concentrations of fluoride and acetate ions is suggestive

Iodination of carbohydrate-derived 1,2-oxazines to enantiopure 5-iodo-3,6-dihydro-2H-1,2-oxazines and subsequent palladium-catalyzed cross-coupling reactions

• Michal Medvecký,
• Igor Linder,
• Luise Schefzig,
• Hans-Ulrich Reissig and
• Reinhold Zimmer

Beilstein J. Org. Chem. 2016, 12, 2898–2905, doi:10.3762/bjoc.12.289

• cyano group at the 5-position would lead to a push–pull system that could open new synthetic opportunities including the attack of nucleophiles at C-4. Metal cyanides such as KCN represent synthetically valuable C-1 building blocks that could efficiently be coupled by palladium catalysis to alkenyl

Effects of solvent additive on “s-shaped” curves in solution-processed small molecule solar cells

• John A. Love,
• Shu-Hua Chou,
• Ye Huang,
• Guilllermo C. Bazan and
• Thuc-Quyen Nguyen

Beilstein J. Org. Chem. 2016, 12, 2543–2555, doi:10.3762/bjoc.12.249

• ], where D1 is an electron-rich unit such as bithiophene, A is a benzothiadiazole derivative and D2 can be different electron-rich planar cores such as dithienosilol or silanindacenodithiophene. Utilizing this push–pull molecular approach, efficiencies up to 9.0% have been achieved [13] due to deep highest

Methylenelactide: vinyl polymerization and spatial reactivity effects

• Judita Britner and
• Helmut Ritter

Beilstein J. Org. Chem. 2016, 12, 2378–2389, doi:10.3762/bjoc.12.232

• polymerization of the cyclic push–pull-type monomer methylenelactide in comparison to the non-cyclic monomer α-acetoxyacrylate is described. The experimental results revealed that methylenelactide undergoes a self-initiated polymerization. The copolymerization parameters of methylenelactide and styrene as well

• -dimethylacrylamide was performed at 70 °C in 1,4-dioxane using AIBN as initiator and 2-(((ethylthio)carbonothioyl)thio)-2-methylpropanoic acid as a transfer agent. Keywords: copolymerization; kinetic study of the radical homopolymerization; push–pull monomer; reversible addition fragmentation chain transfer (RAFT

• donating (“pushing”) oxygen atom. Monomers with such substitution patterns are defined as captodative or push–pull monomers [1]. MLA was first synthesized in 1969 by Scheibelhoffer et al. through a bromination of L-lactide followed by a basic HBr elimination [2]. In 2008, the first Diels–Alder reaction

A selective and mild glycosylation method of natural phenolic alcohols

• Mária Mastihubová and
• Monika Poláková

Beilstein J. Org. Chem. 2016, 12, 524–530, doi:10.3762/bjoc.12.51

• major product. For example, the DDQ–I2-promoted reaction provided aldehyde 24 in 58% yield along with less than 5% of the desired product 23. This may be caused by the oxidative nature of the promoter and by the existence of a conjugated electronic push–pull system of coniferyl alcohol that is enhanced

An efficient synthesis of N-substituted 3-nitrothiophen-2-amines

• Sundaravel Vivek Kumar,
• Shanmugam Muthusubramanian,
• J. Carlos Menéndez and
• Subbu Perumal

Beilstein J. Org. Chem. 2015, 11, 1707–1712, doi:10.3762/bjoc.11.185

• methylmercaptan and water furnishes the product 3 (Scheme 4). Conclusion In conclusion, we have developed a very efficient synthesis of a synthetically and biologically relevant class of push–pull heterocyclic compounds under mild conditions and starting from simple acyclic substrates and catalysts. Previously

A new and convenient synthetic way to 2-substituted thieno[2,3-b]indoles

• Roman A. Irgashev,
• Arseny A. Karmatsky,
• Gennady L. Rusinov and
• Valery N. Charushin

Beilstein J. Org. Chem. 2015, 11, 1000–1007, doi:10.3762/bjoc.11.112

• compounds which can be applied in organic optoelectronic materials. Indeed, we have recently reported the synthesis of novel push–pull dyes IK-1,2 based on the thieno[2,3-b]indole ring system, as a donating part of dye-sensitized solar cells [8] (Figure 1). It should be noted that thieno[2,3-b]pyrrole and

• analogues. This two-step approach provides an easy access to compounds of the family of electron-rich thieno[2,3-b]indoles, which are regarded as promising building-blocks for the development of new photo- and electrosensitive molecules, e.g., novel push–pull dyes for dye-sensitized solar cells

Solution processable diketopyrrolopyrrole (DPP) cored small molecules with BODIPY end groups as novel donors for organic solar cells

• Diego Cortizo-Lacalle,
• Calvyn T. Howells,
• Upendra K. Pandey,
• Joseph Cameron,
• Neil J. Findlay,
• Anto Regis Inigo,
• Tell Tuttle,
• Peter J. Skabara and
• Ifor D. W. Samuel

Beilstein J. Org. Chem. 2014, 10, 2683–2695, doi:10.3762/bjoc.10.283

• derivatives (e.g., selenophene) [20][21][22][23], often in combination with other heterocyclic units; the best performing systems are push–pull molecules or dyes [14]. In the last few years the diketopyrrolopyrrole (DPP, 1, Figure 1) core has been widely incorporated in conjugated polymers for both OPVs and

Photoswitchable precision glycooligomers and their lectin binding

• Daniela Ponader,
• Sinaida Igde,
• Marko Wehle,
• Katharina Märker,
• Mark Santer,
• David Bléger and
• Laura Hartmann

Beilstein J. Org. Chem. 2014, 10, 1603–1612, doi:10.3762/bjoc.10.166

• phenylamine one for two reasons: first, its higher nucleophilicity allows for a smoother synthesis and second, the resulting Z-azobenzene exhibits a high thermal stability as compared to the fully conjugated push-pull azobenzene based on the phenylamine fragment. In total, five precision glycooligomers were

Use of activated enol ethers in the synthesis of pyrazoles: reactions with hydrazine and a study of pyrazole tautomerism

• Denisa Tarabová,
• Stanislava Šoralová,
• Martin Breza,
• Marek Fronc,
• Wolfgang Holzer and
• Viktor Milata

Beilstein J. Org. Chem. 2014, 10, 752–760, doi:10.3762/bjoc.10.70

• [30]. The small chemical shift for the quaternary alkene C-atom (δ 93.0 ppm) is characteristic for a polarized C=C bond in this push–pull configuration. One half of the isomer B shows the same characteristics as A , that is, the intramolecular hydrogen bond between NH and the ester C=O. However, the

One-pot three-component synthesis and photophysical characteristics of novel triene merocyanines

• Christian Muschelknautz,
• Robin Visse,
• Jan Nordmann and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 599–612, doi:10.3762/bjoc.10.51

• -substituted polyenes, has become increasingly interesting due to their fine-tunable electronic distribution [10]. For instance, merocyanines are perfectly suited for developing molecule-based non-linear optical materials and photovoltaic chromophores [11]. Classically, these push–pull chromophores always have

• convergent strategies paved the way to luminescent push–pull dienes 1–4 with conformationally flexible and fixed acceptor units (Figure 1) [30][31][32], pyrazoles [33][34], benzodiazepines [35], furans and pyrroles [36][37] by consecutive multicomponent reactions and to highly emissive spirocycles [38][39

• particular, the electrophilic enyne intermediate [32][40], which is trespassed in the three-component synthesis of solid-state luminescent push–pull indolones 4, intrigued our interest for accessing even triene push–pull systems and to study their electronic properties. Here we report our findings on the

A reductive coupling strategy towards ripostatin A

• Kristin D. Schleicher and
• Timothy F. Jamison

Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175

• hemiester generated in situ from the substrate and phenylboronic acid. It is proposed that complexation of the tertiary nitrogen to boron and coordination of the carbonyl act in a push/pull fashion, simultaneously enhancing the nucleophilicity of the boronate oxygen as well as imposing a chiral environment

An organocatalytic route to 2-heteroarylmethylene decorated N-arylpyrroles

• Alexandre Jean,
• Jérôme Blanchet,
• Jacques Rouden,
• Jacques Maddaluno and
• Michaël De Paolis

Beilstein J. Org. Chem. 2013, 9, 1480–1486, doi:10.3762/bjoc.9.168

• presents an ideal push–pull configuration tunable with the pH by protonation of the pyridine ring. This is likely to lead to applications of 10a such as for new water-soluble molecular probes. Conclusion A new catalytic and regioselective preparation of substituted N-arylpyrroles decorated with various 2

Homolytic substitution at phosphorus for C–P bond formation in organic synthesis

• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 1269–1277, doi:10.3762/bjoc.9.143

• , which utilizes diphosphines generated in situ from chlorophosphine and hydrophosphine in the presence of triethylamine [28]. A variety of terminal alkynes undergo the radical diphosphination (Table 1). The diphosphination was applicable to the synthesis of a new push–pull-type molecule that emits blue

Enhancement of efficiency in organic photovoltaic devices containing self-complementary hydrogen-bonding domains

• Rohan J. Kumar,
• Jegadesan Subbiah and
• Andrew B. Holmes

Beilstein J. Org. Chem. 2013, 9, 1102–1110, doi:10.3762/bjoc.9.122

• domains were incorporated as the electron deficient unit in “push–pull”, p-type small molecules for organic photovoltaic active layers. Such compounds were found to enhance the fill factor, compared with similar non-self-organized compounds reported in the literature, leading to higher device efficiencies

• -bonding domain has been incorporated as the electron-deficient moiety in a “push–pull” p-type molecule 2 for organic solar cells. Self-association of this domain could be monitored by 1H NMR, and at higher concentrations the compound was found to form nanostructures and organogels. In bulk heterojunction

Control over molecular motion using the cis–trans photoisomerization of the azo group

• Estíbaliz Merino and
• María Ribagorda

Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119

• with π→π* transition is shifted to red, changing the appearance order with respect to the band n→π*. The azocompounds of this type present donor substituents (X) and electron acceptors (Y) at the 4 and 4' positions, respectively (push/pull system) (red colour). The isomerization process normally

Recent advances towards azobenzene-based light-driven real-time information-transmitting materials

• Jaume García-Amorós and
• Dolores Velasco

Beilstein J. Org. Chem. 2012, 8, 1003–1017, doi:10.3762/bjoc.8.113

• -chromophore and the thermal cis-to-trans isomerisation, the kinetics and mechanism are also discussed as a key point for reaching azoderivatives endowed with fast thermal back-isomerisation kinetics. Keywords: kinetics; light-controlled materials; molecular switches; photochromic switches; push–pull

• substitution (type-I), that is, bearing a push–pull configuration. Secondly, kinetic studies of different azophenolic systems (type-II) will be presented, since these azoderivatives exhibit a fast thermal back reaction due to their capability to establish an azo-hydrazone tautomeric equilibrium. Both type-I

• the millisecond time scale, based on chromophores with a push–pull configuration The electronic spectra of the stable trans isomer of type-I azoderivatives 1–4, display a high-intensity band peaking at ca. 355 nm, corresponding to the π→π* transition, and a weak broad-band signal at ca. 450 nm

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

• Jiří Kulhánek and
• Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

• Jiri Kulhanek Filip Bures Institute of Organic Chemistry and Technology, Faculty of Chemical Technology, University of Pardubice, Studentská 573, Pardubice, CZ-53210, Czech Republic 10.3762/bjoc.8.4 Abstract Research activities in the field of imidazole-derived push–pull systems featuring

• made in the development and the investigation of new organic push–pull systems. In contrast to inorganic materials, the advent of dipolar (hetero)organic materials with readily polarizable structure was stimulated by their relative ease of synthesis, well-defined structure, chemical and thermal

• robustness, possibility for further modification, and facile property tuning. Hence, heteroaromatic push–pull chromophores have been targeted and investigated as active components of optoelectronic devices, organic light-emitting diodes (OLED), photovoltaic cells, semiconductors, switches, data-storage

Recent advances in the development of alkyne metathesis catalysts

• Xian Wu and
• Matthias Tamm

Beilstein J. Org. Chem. 2011, 7, 82–93, doi:10.3762/bjoc.7.12

• hexafluoro-tert-butoxide, OCCH3(CF3)2, proved to be essential for creating active catalysts [74], indicating that successful catalyst design in this system relies on establishing a push-pull situation in a similar fashion present in Schrock–Hoveyda olefin metathesis catalysts (Scheme 4) [10] and also in an