Photochromic diarylethene ligands featuring 2-(imidazol-2-yl)pyridine coordination site and their iron(II) complexes

• Andrey G. Lvov,
• Max Mörtel,
• Anton V. Yadykov,
• Frank W. Heinemann,
• Valerii Z. Shirinian and
• Marat M. Khusniyarov

Beilstein J. Org. Chem. 2019, 15, 2428–2437, doi:10.3762/bjoc.15.235

• cyclohexenone bridges [32]. These methods utilize ethyl 4-(2,5-dimethylthiophen-3-yl)-3-oxobutanoate (Scheme 1) or its analogs as starting materials. To obtain novel diarylethenes with 2-(imidazol-2-yl)pyridine moiety, here we have synthesized a previously unknown imidazole derivative 1 by a one-pot

• good accordance with previous DFT calculations [37], the molecule shows exclusively antiparallel conformation [8] of the thiophene and imidazole groups of the photoactive diarylethene moiety, with the respective α-methyl groups pointing in different directions. The thiophene and imidazole rings are

• yield is lower [40]. The quantum yields for cyclohexenone derivatives 6 and 7 are in the 0.22–0.27 range. Similar to some other cyclopentene derivatives [41], diarylethene 4 possesses low cycloreversion quantum yields at 4–6%. However, in accordance with previous results on imidazole derivatives [42], 3

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

• Arylazopyrazoles represent a new family of molecular photoswitches characterized by a near-quantitative conversion between two states and long thermal half-lives of the metastable state. Here, we investigated the behavior of a model arylazopyrazole in the presence of a self-assembled cage based on Pd–imidazole

•  2 above). For example, E-1’s Ha protons at 1.07 ppm correlate with 2’s axial – but not equatorial – acidic imidazole H1 protons (cyan in Figure 2), which is in agreement with the close proximity of these two protons in the X-ray structure (da–1 = 3.68 Å). Conversely, Hc protons only correlate with

• of signals at 7.88–7.60 (all of which could be attributed to 2) correlate strongly with the protons of all three methyl groups of Z-1 (Ha, Hb, and Hc), in addition to exhibiting weaker NOE correlations with Hd, He, and Hf. Furthermore, the acidic imidazole protons correlate with most of Z-1’s protons

Click chemistry towards thermally reversible photochromic 4,5-bisthiazolyl-1,2,3-triazoles

• Chenxia Zhang,
• Kaori Morinaka,
• Mahmut Kose,
• Takashi Ubukata and
• Yasushi Yokoyama

Beilstein J. Org. Chem. 2019, 15, 2161–2169, doi:10.3762/bjoc.15.213

• (thiazole) [39], and 10c (imidazole) [40] in non-polar solvents, 1c has a much longer absorption maximum in toluene (Scheme 4, Table 2). It should also be noted that the absorption maximum wavelength is longer when the central ethene moiety is part of the aromatic ring than when it is an isolated ethene in

Synthesis of 1-azaspiro[4.4]nonan-1-oxyls via intramolecular 1,3-dipolar cycloaddition

• Yulia V. Khoroshunova,
• Denis A. Morozov,
• Andrey I. Taratayko,
• Polina D. Gladkikh,
• Yuri I. Glazachev and
• Igor A. Kirilyuk

Beilstein J. Org. Chem. 2019, 15, 2036–2042, doi:10.3762/bjoc.15.200

• 7c. 1,3-Dipolar cycloaddition of nitrones to alkenes is known to be reversible [13][14]. We recently reported a similar reversibility of the intramolecular cyclization of sterically hindered pent-4-enylnitrone of the 2H-imidazole series [15]. Treatment with Zn in an AcOH/EtOH/EDTA/Na2 mixture was

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

• , imidazo[2,1-b]selenoazoles, in which imidazole and selenophene are condensed, have been synthesized, and it was described in a patent that imidazo[2,1-b]benzoselenazole-3-acetamide derivatives have anticonvulsant activity [5]. Three ring closure reactions for the synthesis of imidazo[2,1-b]selenoazole

• -bromophenyl)imidazole (1i) with Se powder gave the corresponding tricyclic product 10 in low yield. Since the reaction conditions for the synthesis of the starting material 1 and the cyclization of 1 with Se powder are similar, we carried out a three-component reaction of benzimidazole, 1-bromo-2

• mechanism is as depicted in Scheme 3. The base deprotonates the imidazole ring giving an anion at the 2-position, which reacts with selenium by nucleophilic attack, resulting in C(Het)–Se bond formation. Next, the ring closure proceeds via the SNAr reaction by attack of the selenide anion on the phenyl

Reactions of 2-carbonyl- and 2-hydroxy(or methoxy)alkyl-substituted benzimidazoles with arenes in the superacid CF₃SO₃H. NMR and DFT studies of dicationic electrophilic species

• Dmitry S. Ryabukhin,
• Alexey N. Turdakov,
• Natalia S. Soldatova,
• Mikhail O. Kompanets,
• Alexander Yu. Ivanov,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2019, 15, 1962–1973, doi:10.3762/bjoc.15.191

• reaction [14]. Recently, several hydroxyalkylation reactions followed by alkylation of arenes have been reported involving heterocycle-based superelectrophiles: pyridines, thiazoles, quinolines, isoquinolines, pyrazines, pyrazoles, imidazole and furans, bearing a formyl (carbonyl) group [15][16][17][18][19

• , superelectrophilic activation of the carbonyl group was achieved for 5-formyl and 5-acetylimidazoles in triflic acid CF3SO3H (TfOH) by Klumpp [19]. It was proposed that the triflic acid initially protonated the imidazole ring and an equilibrium was established with the O-protosolvated form or the dicationic

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

An azobenzene container showing a definite folding – synthesis and structural investigation

• Abdulselam Adam,
• Saber Mehrparvar and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2019, 15, 1534–1544, doi:10.3762/bjoc.15.156

• the amino acid side chains, are described in the literature [49][50]. One example is the platform 4, which consists of two imidazole building blocks connected by two azobenzene units (Figure 2) [50]. Irradiation of the platform 4 with UV light results in a trans→cis isomerization accompanied by a

• reduction of the distance between the two isopropyl groups. As further example the chiral foldable container 5 should be mentioned [49]. Here, two imidazole-containing macrocycles are linked to each other by two azobenzene units (Figure 2). Irradiation with UV light causes two consecutive trans→cis

• the chiral switchable container we intended to use the imidazole-containing peptides 2a (R = R’ = iPr) and 3a (R = R’ = iPr) as macrocycles (see Figure 1 and Scheme 1). Both feature two imidazole units which should be used to attach the azobenzene groups. Additionally, platform 2a has two valine units

Synthesis and biological evaluation of truncated derivatives of abyssomicin C as antibacterial agents

• Leticia Monjas,
• Peter Fodran,
• Johanna Kollback,
• Carlo Cassani,
• Thomas Olsson,
• Maja Genheden,
• D. G. Joakim Larsson and
• Carl-Johan Wallentin

Beilstein J. Org. Chem. 2019, 15, 1468–1474, doi:10.3762/bjoc.15.147

• (2.0 equiv), imidazole (4.0 equiv), DMF, rt, 2 h, 95%. e) HF·pyridine, pyridine, THF, rt, 45 h, 75%. f) i: (COCl)2 (1.2 equiv), DMSO (2.4 equiv), CH2Cl2, −78 °C, 1.5 h; ii: Et3N (5.0 equiv), −78 °C to rt, 1 h, 91%. Synthesis of the building blocks 4 and 5. a) TFA (1.1 equiv), CH2Cl2, rt, 24 h, 84% (14

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• ] reported another example of a diastereoselective MCR between a 6-ketosteroid, 2-aminopyridines and an isocyanide, using propylphosphonic acid anhydride (TP3) as catalyst to afford a steroidal derivative with an imidazole-pyridine moiety attached to ring B. This moiety is present in several compounds

A three-component, Zn(OTf)₂-mediated entry into trisubstituted 2-aminoimidazoles

• Alexei Lukin,
• Anna Bakholdina,
• Anna Kryukova,
• Alexander Sapegin and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2019, 15, 1061–1064, doi:10.3762/bjoc.15.103

• co-workers describing Zn(OTf)2-catalyzed, microwave-promoted conversion of a mixture of a secondary propargylamide and an amine into a trisubstituted imidazole 1 [1][2] inspired us to explore several variants of this methodology. Last year, we described the synthesis of differently substituted

• which makes it a useful tool for library array synthesis. The investigation of other metal-catalyzed transformations of propargylureas is underway in our laboratories and will be reported in due course. Examples of imidazole (1 and 2) and oxazole (3) syntheses from propargylamides previously reported

Novel (2-amino-4-arylimidazolyl)propanoic acids and pyrrolo[1,2-c]imidazoles via the domino reactions of 2-amino-4-arylimidazoles with carbonyl and methylene active compounds

• Victoria V. Lipson,
• Tetiana L. Pavlovska,
• Nataliya V. Svetlichnaya,
• Anna A. Poryvai,
• Nikolay Yu. Gorobets,
• Erik V. Van der Eycken,
• Irina S. Konovalova,
• Svetlana V. Shiskina,
• Alexander V. Borisov,
• Vladimir I. Musatov and
• Alexander V. Mazepa

Beilstein J. Org. Chem. 2019, 15, 1032–1045, doi:10.3762/bjoc.15.101

• selectively led to the corresponding Knoevenagel–Michael adducts containing a free amino group in the imidazole fragment. The adducts derived from Meldrum’s acid have been smoothly converted into 1,7-diaryl-3-amino-6,7-dihydro-5H-pyrrolo[1,2-c]imidazol-5-ones and 3-(2-amino-4-aryl-1H-imidazol-5-yl)-3

• -arylpropanoic acids. The interaction of 2-amino-4-arylimidazoles with aromatic aldehydes or isatins and acyclic methylene active compounds has led to the formation of pyrrolo[1,2-c]imidazole-6-carbonitriles, pyrrolo[1,2-с]imidazole-6-carboxylates and spiro[indoline-3,7'-pyrrolo[1,2-c]imidazoles], which can be

• considered as the analogues of both 3,3’-spirooxindole and 2-aminoimidazole marine sponge alkaloids. Keywords: 2-amino-4-arylimidazole; (2-amino-4-arylimidazolyl)propanoic acid; isatin; Meldrum’s acid; multicomponent reactions; pyrrolo[1,2-c]imidazole; 3,3’-spirooxindoles; Introduction Heterocyclic

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• organocatalysis using PhI (10 mol %)–mCPBA at ambient conditions as well as under neat mixing [115]. The N1,N1-dibenzylbenzene-1,2-diamine (Figure 27) which is an integrated system by the combination of aniline and N,N-dibenzylaniline led to the successful formation of 1-benzyl-2-phenyl-benzo[d]imidazole 48 under

Synthesis of acylglycerol derivatives by mechanochemistry

• Karen J. Ardila-Fierro,
• Andrij Pich,
• Marc Spehr,
• José G. Hernández and
• Carsten Bolm

Beilstein J. Org. Chem. 2019, 15, 811–817, doi:10.3762/bjoc.15.78

• . Results and Discussion To commence, we focused on the synthesis of tert-butyldimethylsilyl glycidyl ether (2) by reacting glycidol (1; 0.67 mmol) and tert-butyldimethylsilyl chloride (TBDMSCl) in the presence of imidazole in a mixer mill (MM, Scheme 2) [32]. After 2 h of milling at 25 Hz full consumption

An efficient and concise access to 2-amino-4H-benzothiopyran-4-one derivatives

• Peng Li,
• Yongqi Wu,
• Tingting Zhang,
• Chen Ma,
• Ziyun Lin,
• Gang Li and
• Haihong Huang

Beilstein J. Org. Chem. 2019, 15, 703–709, doi:10.3762/bjoc.15.65

• -aminobenzothiopyranones containing 8-nitro and 6-trifluoromethyl substituents in low to moderate yields through the transformation of a 2-methylthio substituent under harsh conditions (method F, Scheme 1) [5]. In addition, the nucleophile imidazole could also react with 3-bromobenzothiopyranones to afford 2

Synthesis and SAR of the antistaphylococcal natural product nematophin from Xenorhabdus nematophila

• Frank Wesche,
• Hélène Adihou,
• Thomas A. Wichelhaus and
• Helge B. Bode

Beilstein J. Org. Chem. 2019, 15, 535–541, doi:10.3762/bjoc.15.47

• benzyl improves the in vitro antistaphylococcal activity. In contrast, the incorporation of smaller heterocycles like pyridine and imidazole as well as isosteric benzimidazole instead of the indole moieties lead to a loss of antibacterial activity. Kennedy et al. could synthesize a 2-phenyl derivative

Synthesis and selected transformations of 2-unsubstituted 1-(adamantyloxy)imidazole 3-oxides: straightforward access to non-symmetric 1,3-dialkoxyimidazolium salts

• Grzegorz Mlostoń,
• Małgorzata Celeda,
• Katarzyna Urbaniak,
• Marcin Jasiński,
• Vladyslav Bakhonsky,
• Peter R. Schreiner and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2019, 15, 497–505, doi:10.3762/bjoc.15.43

• solution in monomeric form. This product was used for reactions with α-hydroxyiminoketones leading to a new class of 2-unsubstituted imidazole 3-oxides bearing the adamantyloxy substituent at N(1). Their reactions with 2,2,4,4-tetramethylcyclobutane-1,3-dithione or with acetic acid anhydride occurred

• analogously to those of 1-alkylimidazole 3-oxides to give imidazol-2-thiones and imidazol-2-ones, respectively. Treatment of 1-(adamantyloxy)imidazole 3-oxides with Raney-Ni afforded the corresponding imidazole derivatives without cleavage of the N(1)–O bond. Finally, the O-alkylation reactions of the new

• imidazole N-oxides with 1-bromopentane or 1-bromododecane open access to diversely substituted, non-symmetric 1,3-dialkoxyimidazolium salts. Adamantyloxyamine reacts with glyoxal and formaldehyde in the presence of hydrobromic acid yielding symmetric 1,3-di(adamantyloxy)-1H-imidazolium bromide in good yield

Aqueous olefin metathesis: recent developments and applications

• Valerio Sabatino and
• Thomas R. Ward

Beilstein J. Org. Chem. 2019, 15, 445–468, doi:10.3762/bjoc.15.39

• nucleophilic attack at the chloromethyl moiety by the imidazole of His57, to afford the artificial metathase ArM 3 (Scheme 14). Matsuo et al. tested the RCM of three different substrates with the protein-free catalyst 66 as well as ArM 3 (Table 7). No RCM occurred with substrate 52 (<2 TON) with catalyst 66

Synthesis of C₃-symmetric star-shaped molecules containing α-amino acids and dipeptides via Negishi coupling as a key step

• Sambasivarao Kotha and
• Saidulu Todeti

Beilstein J. Org. Chem. 2019, 15, 371–377, doi:10.3762/bjoc.15.33

• tetrahydrofuran (THF) to obtain the N-Boc-serine methyl ester (5) in 93% yield [42]. Afterwards, the protected methyl ester 5 was subjected to iodination in the presence of iodine (I2), triphenylphosphane (PPh3) and imidazole in CH2Cl2 at 0 °C to deliver the iodo derivative 6 in 63% yield [43][44]. Finally, the

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• , reaction with pyrrolidine, imidazole, methanol, allyl alcohol, benzyl alcohol and 9-fluorenemethanol (FmOH) provided the corresponding urea 30, N-carbamoyl imidazole 31 and carbamates 32–35, respectively, in good yields (69–80%). The reaction of isocyanate 28 with tert-butanol was sluggish even by heating

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• ; f) Cs2CO3, MeOH; g) t-BuMe2SiCl, imidazole, DMF; h) NaIO4, KMnO4, then CH2N2, ether; i) TBAF; j) 6 M HCl. Synthesis of dimethyl ester of (2S,3R)-2 employing (1S)-2-exo-methoxyethoxyapocamphane-1-carboxylic acid as a chiral auxiliary. Reagents and conditions: a) PhSeCl, MeOH; b) H2C=CHCH2SnBu3, ether

• and conditions: a) BuLi, THF, then H2C=CHCHO; b) MeI, K2CO3, acetone; c) I2, THF; d) EtCOO– Cs+, DMF; e) K2CO3, EtOH; f) t-BuMe2SiCl, imidazole, DMAP, DMF; g) Na, liquid NH3; h) Boc2O, NaH, THF; i) KOH, MeOH/H2O; j) CH2N2, ether; k) TBAF, THF; l) O2, Pt. Synthesis of N-Boc-protected dimethyl ester of

• (2S,3R)-2 via Sharpless epoxidation. Reagents and conditions: a) TBHP, D-(−)-DIPT, Ti(OiPr)4, MS, CH2Cl2; b) t-BuMe2SiCl, imidazole, DMAP, DMF; c) NaIO4, RuO2, AcOEt/H2O. Synthesis of (2S,3S)-2 from the imide 51. Reagents and conditions: a) NaBH4, MeOH/CH2Cl2; b) Ac2O, pyridinium perchlorate; c) furan

Gold-catalyzed ethylene cyclopropanation

• Silvia G. Rull,
• Andrea Olmos and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2019, 15, 67–71, doi:10.3762/bjoc.15.7

• directly converted into ethyl 1-cyclopropylcarboxylate upon reaction with ethyl diazoacetate (N2CHCO2Et, EDA) in the presence of catalytic amounts of IPrAuCl/NaBArF4 (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene; BArF4 = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate). Keywords: carbene

• given our experience with group 11 metal-based catalysts for carbene-transfer reactions from diazoacetates [15][16], we have investigated this transformation and found that the gold complex IPrAuCl (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene) along with one equivalent of NaBArF4 (BArF4

Thermophilic phosphoribosyltransferases Thermus thermophilus HB27 in nucleotide synthesis

• Ilja V. Fateev,
• Ekaterina V. Sinitsina,
• Aiguzel U. Bikanasova,
• Maria A. Kostromina,
• Elena S. Tuzova,
• Larisa V. Esipova,
• Tatiana I. Muravyova,
• Alexei L. Kayushin,
• Irina D. Konstantinova and
• Roman S. Esipov

Beilstein J. Org. Chem. 2018, 14, 3098–3105, doi:10.3762/bjoc.14.289

• , acrylamide, N,N'-bisacrylamide, ATP, bromophenol blue, agarose, EDTA, IPTG, ampicillin, sodium dodecylsulfate, imidazole and DMF were purchased from Panreac (Spain, Barselona). Ethanol was purchased from MedChemProm. Coomassie Brilliant Blue R-250 was purchased from Bio-Rad (USA, CA). Bacto yeast extract

• -equilibrated with 50 mM Tris-HCl and 200 mM NaCl at pH 8.0. Ballast proteins were eluted with a solution, containing 50 mM Tris-HCl, 50 mM imidazole, and 200 mM NaCl, pH 8.0 (4 CV, flow rate 2 mL/min). The target enzyme was eluted with solution, contained 50 mM Tris-HCl, 250 mM imidazole, and 200 mM NaCl, pH

Mn-mediated sequential three-component domino Knoevenagel/cyclization/Michael addition/oxidative cyclization reaction towards annulated imidazo[1,2-a]pyridines

• Olga A. Storozhenko,
• Alexey A. Festa,
• Delphine R. Bella Ndoutoume,
• Alexander V. Aksenov,
• Alexey V. Varlamov and
• Leonid G. Voskressensky

Beilstein J. Org. Chem. 2018, 14, 3078–3087, doi:10.3762/bjoc.14.287

• promising anticancer activity [34], thereby showing the importance of this merged heterocyclic skeleton (Figure 1). The formation of the chromene and imidazole rings in a single-step procedure was independently discovered by us [35][36] and Proença et al. [37][38], who identified 2-iminochromene 3 to be the