Synthesis, electrochemical properties, and antioxidant activity of sterically hindered catechols with 1,3,4-oxadiazole, 1,2,4-triazole, thiazole or pyridine fragments

• Daria A. Burmistrova,
• Andrey Galustyan,
• Nadezhda P. Pomortseva,
• Kristina D. Pashaeva,
• Maxim V. Arsenyev,
• Oleg P. Demidov,
• Mikhail A. Kiskin,
• Andrey I. Poddel’sky,
• Nadezhda T. Berberova and
• Ivan V. Smolyaninov

Beilstein J. Org. Chem. 2024, 20, 2378–2391, doi:10.3762/bjoc.20.202

• , Leninskii prosp., 31, 119991, Moscow, Russia Institute of Inorganic Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany 10.3762/bjoc.20.202 Abstract A series of new RS−, RS−CH2− and R2N−CH2-functionalized сatechols with heterocyclic fragments such as 1,3,4-oxadiazole, 1,2,4

• corresponding thiols. The starting reagents such as substituted 1,3,4-oxadiazole-2-thiols and 4H-triazole-3-thiols are characterized by thiol–thione tautomerism, therefore their reactions with 3,5-di-tert-butyl-6-methoxymethylcatechol can proceed at the sulfur or nitrogen atom. In the case of mercapto

• -derivatives of thiazole or pyridine, this process leads to the formation of the corresponding thioethers with a methylene linker. At the same time, thiolated 1,3,4-oxadiazole or 1,2,4-triazole undergo alkylation at the nitrogen atom in the reaction with 3,5-di-tert-butyl-6-methoxymethylcatechol to form the

Tandem diazotization/cyclization approach for the synthesis of a fused 1,2,3-triazinone-furazan/furoxan heterocyclic system

• Yuri A. Sidunets,
• Valeriya G. Melekhina and
• Leonid L. Fershtat

Beilstein J. Org. Chem. 2024, 20, 2342–2348, doi:10.3762/bjoc.20.200

• agents contain a 1,2,3-triazine ring [37][38][39]. The structures of some bioactive 1,2,3-triazin-4-one derivatives are shown in Figure 1. Hence, one can assume that molecular hybridization of the 1,2,3-triazin-4-one moiety with the 1,2,5-oxadiazole core can lead to a significant modification of the

• synthesized via the reaction of the readily available 4-amino-3-(azidocarbonyl)-1,2,5-oxadiazole 2-oxide (3) with various amines, following a previously described procedure (see Supporting Information File 1 for details) [40][41]. Subsequently, we investigated the possibility of tandem diazotization/azo

• low yield of 4-(mesityldiazenyl)-3-(p-tolylcarbamoyl)-1,2,5-oxadiazole 2-oxide (4) is likely due to the moderate solubility of the starting amide 2a in TFA. To improve the solubility of compound 2a, we tested mixtures of acids as solvent (Table 1, entries 5–8). Thus, the best yield of product 4 was

Heterocycle-guided synthesis of m-hetarylanilines via three-component benzannulation

• Andrey R. Galeev,
• Maksim V. Dmitriev,
• Alexander S. Novikov and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2024, 20, 2208–2216, doi:10.3762/bjoc.20.188

• amines with different nucleophilicity, namely benzylamine (primary alkylamine), morpholine (secondary alkylamine) and aniline (aromatic amine). We first examined the reaction of 1,2,4-oxadiazole-1,3-diketone 1a (σm/σp 0.463/0.575, which is quite close to the constants of the CO2Me group, so a successful

• reaction was expected, Figure 2) with morpholine under previously found conditions (Scheme 2). To our delight, the meta-1,2,4-oxadiazole aniline 3ab, formed by the sequence of aldol-type reactions, was isolated in 80% yield and its structure was confirmed by NMR and single crystal X-ray analysis (CCDC

• diketone 1b, bearing the less electron-withdrawing 1,3,4-oxadiazole moiety (σm/σp 0.335/0.443), with alkylamines proceeded well (73–74% yields), but required the addition of CHCl3 as co-solvent due to the low solubility of the starting 1,3-diketone 1b. On the other hand, the reaction of 1,3-diketone 1b

Harnessing the versatility of hydrazones through electrosynthetic oxidative transformations

• Aurélie Claraz

Beilstein J. Org. Chem. 2024, 20, 1988–2004, doi:10.3762/bjoc.20.175

• undergo deprotonation delivering the oxadiazole 24a. Alternatively, from 23b (R2 ≠ H), nucleophilic addition of methanol to oxycarbenium 26b yielded the oxadiazoline 24b (Scheme 6) [41][42]. In 2020, Lei, Zhang and Gao et al. described the electrooxidative cyclization of in situ-generated α-keto acid

• -derived NH-acylhydrazones to build 1,3,4-oxadiazole derivatives in good yields. The electrolysis was conducted under galvanostatic conditions in methanol using a carbon graphite anode and a platinum cathode. From a mechanistic point of view, in situ condensation of acylhydrazines 28 with α-keto acids 27

• 30. Importantly, a control experiment using benzaldehyde-derived N-benzoylhydrazone delivered the corresponding 1,3,4-oxadiazole in only 25% yield. This result indicates that benzaldehyde-derived hydrazone is a less probable reaction intermediate, thereby supporting the proposed mechanism (Scheme 7

2-Heteroarylethylamines in medicinal chemistry: a review of 2-phenethylamine satellite chemical space

• Carlos Nieto,
• Alejandro Manchado,
• Ángel García-González,
• David Díez and
• Narciso M. Garrido

Beilstein J. Org. Chem. 2024, 20, 1880–1893, doi:10.3762/bjoc.20.163

• 1-[2-thiazol-4-yl-(2-aminoethyl)]-4-N-propylpiperazine derivatives as substrates for acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Compounds 106 and 107 showed good inhibitory potency as multitarget-directed ligands (MTD, Scheme 15). Oxadiazole: In their seminal work, Chiaramonte

• and co-workers [41] also tested 1,3,4-oxadiazole 108 and 1,2,4-oxadiazole 109 histamine congeners towards carbonic anhydrase isoforms, finding moderate potencies among them, with 109 3 times more potent than histamine in CA type VII (Scheme 16). Oxolamine (110, Scheme 16) is a cough suppressant

Cholyl 1,3,4-oxadiazole hybrid compounds: design, synthesis and antimicrobial assessment

• Anas J. Rasras,
• Mohamed El-Naggar,
• Nesreen A. Safwat and
• Raed A. Al-Qawasmeh

Beilstein J. Org. Chem. 2022, 18, 631–638, doi:10.3762/bjoc.18.63

• exhibited selective activity against fungi only. Keywords: antibacterial; cholic acid; heterocyclic; Mannich reaction; oxadiazole; Introduction Microbial infections caused by Gram-negative and Gram-positive bacteria embarrass the health care system worldwide [1]. Pathogens such as Escherichia coli

• the development of multidrug resistant bacteria due to excessive use of antibiotics [2][4]. Heterocyclic compounds are the key components for drug design and synthesis. Among them, 1,3,4-oxadiazole derivatives are attractive and have been investigated for decades. This is due to their promising

• MCF7) [13]. In 2008, Muhi-eldeen et al, synthesized a hybrid compound with 1,3,4-oxadiazole moiety and pyrrolidine connected with propargylic moiety showed antibacterial activity against Staphylococcus aureus and E. coli [14]. On the other hand, the coupling of piperazine with heterocyclic compounds

Synthesis of 3,4,5-trisubstituted isoxazoles in water via a [3 + 2]-cycloaddition of nitrile oxides and 1,3-diketones, β-ketoesters, or β-ketoamides

• Md Imran Hossain,
• Md Imdadul H. Khan,
• Seong Jong Kim and
• Hoang V. Le

Beilstein J. Org. Chem. 2022, 18, 446–458, doi:10.3762/bjoc.18.47

• chlorides to form furoxans also known as 1,2,5-oxadiazole 2-oxides, a class of structures with important biological activities due to their unique electronic nature and coordination ability. Keywords: environmentally friendly; furoxans; 1,2,5-oxadiazole 2-oxides; trifluoromethyl-substituted isoxazoles

• expected 3,4,5-trisubstituted isoxazole 3a and 55% of a compound that we identified as furoxan 4 (a 1,2,5-oxadiazole 2-oxide) which formed through homo-coupling of substrate 1a (Table 1, entry 3). Na2CO3 in 98% water, 2% methanol produced 52% of the isoxazole 3a and 33% of compound 4 after 3 hours (Table 1

• with 95% yield (5% water, 95% methanol, room temperature, 2 hours; see Table 1, entry 15), which adds another method for the synthesis of furoxans to the current literature. The synthesis of furoxans or 1,2,5-oxadiazole-2-oxides was first reported by Kekulé in 1857 [36]. Since then, these nitric oxide

Flow synthesis of oxadiazoles coupled with sequential in-line extraction and chromatography

• Kian Donnelly and
• Marcus Baumann

Beilstein J. Org. Chem. 2022, 18, 232–239, doi:10.3762/bjoc.18.27

• an integrated quenching and extraction step. Lastly, the use of an automated in-line chromatography system was exploited to realise a powerful flow platform for the generation of the heterocyclic targets. Keywords: chromatography; flow synthesis; in-line purification; oxadiazole; reaction

• -oxadiazole unit [28][29][30][31][32][33]. In 2012, Guin and co-workers described the iodine-mediated cyclodesulphurisation of thiosemicarbazides, yielding the corresponding 1,3,4-oxadiazoles [32]. Subsequently, Yu and co-workers reported the iodine-mediated oxidative cyclisation of acyl hydrazones to form

• ]pentane (BCP) building blocks [36], we investigated their use in the oxadiazole-forming reaction. The BCP acid chloride 5 was synthesised from [1.1.1]propellane (3) via the photochemical reaction with isopropyl 2-chloro-2-oxoacetate (Scheme 4). The corresponding BCP acyl hydrazone was then obtained

Synthesis of 5-arylacetylenyl-1,2,4-oxadiazoles and their transformations under superelectrophilic activation conditions

• Andrey I. Puzanov,
• Dmitry S. Ryabukhin,
• Anna S. Zalivatskaya,
• Dmitriy N. Zakusilo,
• Darya S. Mikson,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2021, 17, 2417–2424, doi:10.3762/bjoc.17.158

• ; triflic acid; Introduction 1,2,4-Oxadiazoles have a great importance in chemistry, biology and medicine. Many drugs contain an 1,2,4-oxadiazole ring, such as butalamine [1], libexin [2], ataluren [3], oxolamine [4], and pleconaril [5]. Various oxadiazole derivatives show different kinds of activity

• against cancer [6][7], tuberculosis [8], Gram-positive bacteria [9], and they are used in treatment of epilepsy [10] and Alzheimer disease [11][12][13]. The synthesis of compounds of the 1,2,4-oxadiazole series is an actual task in organic and medicinal chemistry (see selected reviews on this topic [14

• ][15][16][17][18][19][20][21][22]). However, among all the varieties of 1,2,4-oxadiazoles, their acetylenic derivatives are quite rare. To the best of our knowledge, there is only one example of 1,2,4-oxadiazole conjugated with an acetylene bond, which is 3-phenylethynyl-1,2,4-oxadiazole [23]. Up to

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• ], 6,7-dihydro-6-oxo-5H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazine [17], 1,2,4-triazino[5,6-b]indole [18], 1,3,4-thiadiazoline [19], 1,3,4-oxadiazoline [19], 1,2,4-triazoline [19], 3-mercapto-1H-1,2,4-triazole [20], 1,3,4-oxadiazole-2(3H)-thione [20], 4-amino-5-mercapto-4H-1,2,4-triazole [20], and 1,2,4

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• addition of dimethylcyanoguanidine occurred in an acceptable 66% yield (Scheme 19, top) [49]. Interestingly, the addition of hydroxylamine hydrochloride under the same conditions led to the formation of unexpected 3,5-diamino-1,2,4-oxadiazole. This could be explained by the cyclization of the N5

• -hydroxybiguanide intermediate, and subsequent dimethylamine evolution. The synthesis of this oxadiazole was then optimized by using triethylamine and room temperature, which resulted in a 78% yield of the desired product (Scheme 19, bottom). Another interesting example of a ring closure by the intramolecular

• 90% yield. A Lewis acid-promoted cyclization (boron trifluoride etherate at 60 °C) avoided the use of high temperatures, while providing the products in comfortable yields. Dicyanamide has also been shown to react with hydroxylamine hydrochloride to form [1,2,4]oxadiazole-3,5-diamine (Scheme 29A) [49

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

• either 1,2,4-oxadiazoles 72 or quinazolinones 73 (Scheme 26), depending on the reaction conditions. The 1,2,4-oxadiazole ring was selectively obtained in DMF at 60 °С under oxygen atmosphere (1 atm) in the presence of an excess of K3PO4, whereas in DMSO at 100 °С under air and in the presence of Cs2CO3

• intermediate, 4,5-dihydro-1,2,4-oxadiazole. An example of such intermediate 74 is shown in Scheme 27. Oxidative aromatization of 74 leads to 1,2,4-oxadiazole 72a (Scheme 26). The second pathway, hydrogen abstraction followed by β-scission presumably leads to iminyl radical, which forms the observed

Synthesis, liquid crystalline behaviour and structure–property relationships of 1,3-bis(5-substituted-1,3,4-oxadiazol-2-yl)benzenes

• Afef Mabrouki,
• Malek Fouzai,
• Armand Soldera,
• Abdelkader Kriaa and
• Ahmed Hedhli

Beilstein J. Org. Chem. 2020, 16, 149–158, doi:10.3762/bjoc.16.17

• moments were also investigated. Keywords: dipole moment; fluorine; liquid crystal; oxadiazole; Introduction Liquid-crystalline (LC) materials have been known for over a century [1]. It is clear that architecture and functionalization are essential aspects in molecular engineering of liquid crystals [2

• , while their hydrocarbon counterparts are non-mesomorphic [20]. On the other hand, many heterocyclic-based liquid crystals have been designed and then synthesised due to their large scope of applications [21]. In this context, the 1,3,4-oxadiazole group was of a particular interest from a synthetic

• viewpoint, considering the numerous ways to introduce this group into a molecule [22][23]. So, it was established that the introduction of a 1,3,4-oxadiazole ring as terminal group on a biphenyl provides liquid crystalline materials [24][25]. However, when the oxadiazole unit is incorporated in the aromatic

Synthesis of benzo[d]imidazo[2,1-b]benzoselenoazoles: Cs₂CO₃-mediated cyclization of 1-(2-bromoaryl)benzimidazoles with selenium

• Mio Matsumura,
• Yuki Kitamura,
• Arisa Yamauchi,
• Yoshitaka Kanazawa,
• Yuki Murata,
• Tadashi Hyodo,
• Kentaro Yamaguchi and
• Shuji Yasuike

Beilstein J. Org. Chem. 2019, 15, 2029–2035, doi:10.3762/bjoc.15.199

• Figure S2 in Supporting Information File 1). Cs2CO3-mediated C(Het)–S bond formations of a heteroazole such as imidazo[1,2-a]pyridine, oxadiazole, and benzimidazole with diaryl disulfides without a transition metal catalyst have previously been developed [18][19]. The key step in these reactions is

Reactions of 3-(p-substituted-phenyl)-5-chloromethyl-1,2,4-oxadiazoles with KCN leading to acetonitriles and alkanes via a non-reductive decyanation pathway

• Akın Sağırlı and
• Yaşar Dürüst

Beilstein J. Org. Chem. 2018, 14, 3011–3017, doi:10.3762/bjoc.14.280

• compounds were identified by means of IR, 1H NMR, 13C NMR, 2D NMR spectra, TOF–MS and X-ray measurements. Keywords: decyanation; KCN; 1,2,4-oxadiazole; Introduction Heterocyclic scaffolds bearing 1,2,4-oxadiazole rings have been the subject of an increasing and remarkable attention due to their various

• crystals, and solar cells [7][8][9][10]. Taking into account the above considerations, new synthetic protocols to develop 1,2,4-oxadiazole-based heterocycles have gained an increasing attention over the recent decades [11][12][13]. On the other hand, arylacetonitriles are known as valuable intermediates

• exploited by providing very limited structural data [19]. Interestingly, increasing the reaction temperature to 100 °C yielded 1,2,4-oxadiazole-substituted propanes 4 as the major products which can only be interpreted via a decyanation pathway of cyanated oxadiazoles 3 (Figure 2). Up to date, various

Targeting the Pseudomonas quinolone signal quorum sensing system for the discovery of novel anti-infective pathoblockers

• Christian Schütz and
• Martin Empting

Beilstein J. Org. Chem. 2018, 14, 2627–2645, doi:10.3762/bjoc.14.241

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• the anti-configuration in all cases. In addition, the option for oxidation to the oxazole or thiazole is always enticing as a way of easily accessing a diverse set of molecules. Immediately akin to the oxazole moiety is the oxadiazole heterocycle, which exhibits similar properties. There are several

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

• Cristina Cebrián and
• Matteo Mauro

Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124

• value dropping to 2% at a practical brightness of 500 cd m−2. Nevertheless, this work opens the door for a novel design of highly efficient deep-blue phosphors. More complex structures based on dinuclear platinum(II) complexes have also been recently described [20]. Upon using two 1,3,4-oxadiazole-2

• that leads to severe roll-off efficiency of OLEDs [64]. In particular, carbazole-based donor moieties and either phenylbenzimidazole (PBI) or oxadiazole (OXD) accepting units were selected as the hole-transporting and electron-transporting moiety, respectively. Two linkage fashions were explored

Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)

• Thanh-Tuân Bui,
• Fabrice Goubard,
• Malika Ibrahim-Ouali,
• Didier Gigmes and
• Frédéric Dumur

Beilstein J. Org. Chem. 2018, 14, 282–308, doi:10.3762/bjoc.14.18

One-pot sequential synthesis of tetrasubstituted thiophenes via sulfur ylide-like intermediates

• Jun Ki Kim,
• Hwan Jung Lim,
• Kyung Chae Jeong and
• Seong Jun Park

Beilstein J. Org. Chem. 2018, 14, 243–252, doi:10.3762/bjoc.14.16

• . Thiophene could not generate the desired intermediate because of the lower electronegativity and a weaker inductive effect of sulfur (Table 1, entry 8). Among 1,2,4-oxadiazole moieties, the 3-trifluoromethyloxadiazole group afforded the desired thiophene 8i (Table 1, entry 9), whereas the 5

• ]: among isomeric benzylpyridines, the 4-isomer is more acidic than the 2-isomer, and the 4- and 2-isomers are much more acidic than the 3-isomer. In the case of the oxadiazole-substituted compound 7i, inductive and mesomeric effects facilitated its sulfur ylide-like intermediate formation [71]. For

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

• Grzegorz Mlostoń and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221

• ; cyclopropanations Dimethoxycarbene (6), generated in situ by thermal decomposition of 2,2-dimethoxy-2,5-dihydro-1,3,4-oxadiazole 7, reacts with E-1b yielding a mixture of the trans-configured tetramethoxycyclobutane 8 and 2,3-dihydrofuran 9 [21][22] (Scheme 3). The latter reacts further with dimethoxycarbene and

• , and in both cases pyrazol-3-ones 68 were obtained in ca. 35% yield (Scheme 22). The heterocyclization leading to 68 occurs in the intermediate enehydrazide 69 through the nucleophilic attack of the N-atom onto the ester group. The second product was postulated either as a 2,3-dihydro-1,3,4-oxadiazole

New tricks of well-known aminoazoles in isocyanide-based multicomponent reactions and antibacterial activity of the compounds synthesized

• Maryna V. Murlykina,
• Maryna N. Kornet,
• Sergey M. Desenko,
• Svetlana V. Shishkina,
• Oleg V. Shishkin,
• Aleksander A. Brazhko,
• Vladimir I. Musatov,
• Erik V. Van der Eycken and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2017, 13, 1050–1063, doi:10.3762/bjoc.13.104

• with 2-amino-1,3,4-thiadiazoles [71][83][84][89][90], 2-aminoimidazoles [71][72][91][92], 2-aminoxazoles [71] and 1,2,5-oxadiazole-3,4-diamine [93] with the formation of imidazoazoles. Among the pyrazoles only 5-amino-3-methylpyrazole, 5-aminopyrazole-4-carbonitrile and ethyl 5-aminopyrazole-4

Metal-free hydroarylation of the side chain carbon–carbon double bond of 5-(2-arylethenyl)-3-aryl-1,2,4-oxadiazoles in triflic acid

• Anna S. Zalivatskaya,
• Dmitry S. Ryabukhin,
• Marina V. Tarasenko,
• Alexander Yu. Ivanov,
• Irina A. Boyarskaya,
• Elena V. Grinenko,
• Ludmila V. Osetrova,
• Eugeniy R. Kofanov and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2017, 13, 883–894, doi:10.3762/bjoc.13.89

• been paid to their synthesis and to the studies of their chemical, physical and biological properties (see numerous reviews [1][2][3][4][5][6][7][8]). The oxadiazole ring represents an essential part of the pharmacophore in many drugs. These compounds possess different kinds of biological activities

• , such as analgesic [9], anti-inflammatory [10], antimicrobial [11], antidiabetic [12], and anticancer [13] to name a few. Some representatives of 1,2,4-oxadiazole-based drugs are shown in Figure 1. Libexin and oxolamine are used as antitussive (cough) agents [14], butalamine is a coronary vasodilator

• and local anesthetic [15], and ataluren finds application for the treatment of fibrosis [16]. Often, oxadiazole derivatives act as inhibitors of bacterial phenylalanyl-tRNA-synthetase [17], phosphodiesterase 4B2 [18], y-secretase [19] and phenol-substituted 1,2,4-oxadiazoles exhibit powerful anti

Energy down converting organic fluorophore functionalized mesoporous silica hybrids for monolith-coated light emitting diodes

• Markus Börgardts and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2017, 13, 768–778, doi:10.3762/bjoc.13.76

• fluorophore derivatives 4 and 5 were accessible by Williamson ether synthesis [24]. The alkyne-functionalized green benzofurazane derivate 6 was obtained by nucleophilic aromatic substitution of 4-chloro-7-nitrobenzo[c][1,2,5]oxadiazole (3) with propargylamine. The alkyne-functionalized derivatives 4, 5 and 6

Synthesis and optical properties of new 5'-aryl-substituted 2,5-bis(3-decyl-2,2'-bithiophen-5-yl)-1,3,4-oxadiazoles

• Anastasia S. Kostyuchenko,
• Tatyana Yu. Zheleznova,
• Anton J. Stasyuk,
• Aleksandra Kurowska,
• Wojciech Domagala,
• Adam Pron and
• Alexander S. Fisyuk

Beilstein J. Org. Chem. 2017, 13, 313–322, doi:10.3762/bjoc.13.34

• by quantum chemical DFT/TDDFT calculations carried out for these new molecules. Keywords: bithiophene; donor–acceptor; luminescence; 1,3,4-oxadiazole; palladium-catalyzed coupling; Introduction π-Conjugated donor–acceptor (D-A) compounds are of significant scientific interest because they

• enables the preparation of linear D–A–D compounds with one or two 1,3,4-oxadiazole [16][17][18][19], 1,3,4-thiadiazole [16][18][19][20][21][22] or 1,2,4-triazole [16][18] central rings symmetrically disubstituted with alkylbithiophene 1, 2 as well as star-shaped molecules with D–A arms 3 (Figure 1) [23

• oxadiazole central ring symmetrically functionalized with bithiophene end-capped with various aryl groups. Our preliminary studies show that these compounds can be used as electroluminophores in LEDs, which show superior performance as compared to the devices fabricated from 1 or 2 [18]. Results and