A combinatorial approach to improving the performance of azoarene photoswitches

• Joaquin Calbo,
• Aditya R. Thawani,
• Rosina S. L. Gibson,
• Andrew J. P. White and
• Matthew J. Fuchter

Beilstein J. Org. Chem. 2019, 15, 2753–2764, doi:10.3762/bjoc.15.266

• -fluoroazopyrazole as part of their study of the supramolecular chemistry of these systems. Irradiating their compound at 365 nm enables near quantitative E→Z conversion, however, the 520 nm PSS provides 55% of the E-isomer. In water, this compound possesses a thermal half-life of >11 days. Herein, we present

• supra) due to the ortho-methoxy groups, which likely explains the inaccuracy of the computational predictions for this compound. The experimental π–π* band for all compounds undergoes a blue shift upon isomerization E to Z, also in good accord with the theoretical predictions (Figure 8, Table S1 and S2

Synthetic terpenoids in the world of fragrances: Iso E Super^® is the showcase

• Alexey Stepanyuk and
• Andreas Kirschning

Beilstein J. Org. Chem. 2019, 15, 2590–2602, doi:10.3762/bjoc.15.252

• assigned as C13H20O [10]. In an attempt to recreate this compound by condensation of acetone with citral (28) a compound with “a strange but not very characteristic odour” was formed, later named pseudoionone (29, Scheme 1). It turned out not to be suited for further investigations. However, after cleaning

Formation of alkyne-bridged ferrocenophanes using ring-closing alkyne metathesis on 1,1’-diacetylenic ferrocenes

• Celine Bittner,
• Dirk Bockfeld and
• Matthias Tamm

Beilstein J. Org. Chem. 2019, 15, 2534–2543, doi:10.3762/bjoc.15.246

• examples that state the metathesis of internal propargylic systems being particularly challenging [13][96][97]. As the [10]ferrocenophane 2a can be obtained reliably and selectively from the RCAM reaction, additional electrochemical and chemical studies were performed on this compound. To resolve the

Effect of ring size on photoisomerization properties of stiff stilbene macrocycles

• Sandra Olsson,
• Óscar Benito Pérez,
• Magnus Blom and
• Adolf Gogoll

Beilstein J. Org. Chem. 2019, 15, 2408–2418, doi:10.3762/bjoc.15.233

• photodynamic properties of this compound have been reported previously [27]. The E- and Z-isomers give distinctively separated chemical shifts for the CH2 protons next to the double bond. This makes the determination of the Z/E ratio straightforward. The composition of the photostable mixtures as compared to

Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

• A. Lennart Schleper,
• Mariano L. Bossi,
• Vladimir N. Belov and
• Stefan W. Hell

Beilstein J. Org. Chem. 2019, 15, 2344–2354, doi:10.3762/bjoc.15.227

• switching cycles in acetonitrile solution while losing only ca. 15% of its absorption. The extrapolation of the change in absorption yielded about 340 switching cycles, until a 50% signal loss occurs. Thus, this compound is a good candidate for a marker applicable in STORM/PALM and MINFLUX super-resolution

Small anion-assisted electrochemical potential splitting in a new series of bistriarylamine derivatives: organic mixed valency across a urea bridge and zwitterionization

• Keishiro Tahara,
• Tetsufumi Nakakita,
• Alyona A. Starikova,
• Takashi Ikeda,
• Masaaki Abe and
• Jun-ichi Kikuchi

Beilstein J. Org. Chem. 2019, 15, 2277–2286, doi:10.3762/bjoc.15.220

• sides are almost coplanar with N···N distances between the NAr3 moieties of more than 13 Å (Figure S5 and Table S1 in Supporting Information File 1). Further investigations were not performed for 1c because the solubility of this compound in aprotic solvents including CH2Cl2 were extremely low. The

Aggregation-induced emission effect on turn-off fluorescent switching of a photochromic diarylethene

• Luna Kono,
• Yuma Nakagawa,
• Ayako Fujimoto,
• Ryo Nishimura,
• Yohei Hattori,
• Toshiki Mutai,
• Nobuhiro Yasuda,
• Kenichi Koizumi,
• Satoshi Yokojima,
• Shinichiro Nakamura and
• Kingo Uchida

Beilstein J. Org. Chem. 2019, 15, 2204–2212, doi:10.3762/bjoc.15.217

• is one of the examples which express the mechanisms of aggregation-induced emission (AIE). This compound emits orange fluorescence with a large Stokes shift derived from ESIPT in aprotic solvents such as THF or hexane, while it exhibits only a photochromic reaction in protic solvents such as methanol

1,2,3,4-Tetrahydro-1,4,5,8-tetraazaanthracene revisited: properties and structural evidence of aromaticity loss

• Arnault Heynderickx,
• Sébastien Nénon,
• Olivier Siri,
• Vladimir Lokshin and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2019, 15, 2059–2068, doi:10.3762/bjoc.15.203

• as the most convenient method of preparation (Scheme 1) [8]. This compound was described as yellow plates (from ethanol), which decomposed at about 300 °C giving a small amount of almost colorless crystalline sublimate identified as 1,4,5,8-tetraazaanthracene (5) [8]. The structure of 3 as the

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

• Withanolides are steroidal lactones widespread in Nightshade plants with often potent antiproliferative activities. Additionally, the structural diversity of this compound class holds much potential for the discovery of novel biological activity. Here, we report two newly characterised withanolides, named

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

• syntheses of this compound the general approach which employs the aziridine ester (2R,1'R)-5b as a starting material allows to also obtain its 5'-epimer and norfuranomycin (2S,2'R)-133 [87]. To construct the 2,5-dihydrofurane ring the aziridine alcohol (2R,1'R,1''R)-134 (Scheme 35) [88] was converted to the

Host–guest interactions in nor-seco-cucurbit[10]uril: novel guest-dependent molecular recognition and stereoisomerism

• Xiaodong Zhang,
• Wei Wu,
• Zhu Tao and
• Xin-Long Ni

Beilstein J. Org. Chem. 2019, 15, 1705–1711, doi:10.3762/bjoc.15.166

• designed and prepared the ADA-benzyl-based ammonium guest molecules G1. We synthesized this compound because ADA can form a highly stable complex with Q[7] (the highest reported K value for the ADA·Q[7] complex is 1012 M−1) [29]; while benzylammonium ions can be included in both cavities of Q[7] and Q[6

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

Different reactivity of phosphorylallenes under the action of Brønsted or Lewis acids: a crucial role of involvement of the P=O group in intra- or intermolecular interactions at the formation of cationic intermediates

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2019, 15, 1491–1504, doi:10.3762/bjoc.15.151

•  2). This compound in reaction with AlCl3 without benzene afforded a mixture of allyl alcohol Z-9 and diene E-10a after aqueous work-up (Table 2, entries 1 and 2). The amount of 2.1 equivalents of AlCl3 is sufficient for activation of this transformation (compared to the amount of AlCl3 in entries 1

Synthesis of pyrrolo[1,2-a]quinolines by formal 1,3-dipolar cycloaddition reactions of quinolinium salts

• Anthony Choi,
• Rebecca M. Morley and
• Iain Coldham

Beilstein J. Org. Chem. 2019, 15, 1480–1484, doi:10.3762/bjoc.15.149

• reaction of quinolinium salts bearing electron-withdrawing groups other than ketones, we prepared ester 4 [55] and amide 5 by alkylation of quinoline. Arylidenemalononitriles such as 6a are known to undergo related chemistry [41], so we heated this compound with the quinolinium salts in the presence of

Efficient resolution of racemic crown-shaped cyclotriveratrylene derivatives and isolation and characterization of the intermediate saddle isomer

• Sven Götz,
• Andreas Schneider and
• Arne Lützen

Beilstein J. Org. Chem. 2019, 15, 1339–1346, doi:10.3762/bjoc.15.133

• elaborated derivatives [58][59] and the ease of a recently established large-scale synthesis reported by Rousseau and co-workers [60]. Hence, we decided to revisit this compound in order to improve the separation in terms of both better resolution of the enantiomeric bowl-shaped conformers and isolation of

• details). Analysis of the data gave a racemization barrier of 114.3 kJ mol−1 which is in good agreement with the value of 114.0 kJ mol−1 reported by Collet for his experiments in dioxane [62]. Perhaps equally interesting for anyone planning to work with this compound this translates into the following

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

• coupling in a low yield of 10% alongside with phthalocyanine byproducts. The triisopropylsilyl-protected derivative 12b could be obtained in a slightly higher yield of 21%, presumably due to the bulkier TIPS-groups. A crystal structure of this compound was obtained (see Supporting Information File 2). To

Genomics-inspired discovery of massiliachelin, an agrochelin epimer from Massilia sp. NR 4-1

• Jan Diettrich,
• Hirokazu Kage and
• Markus Nett

Beilstein J. Org. Chem. 2019, 15, 1298–1303, doi:10.3762/bjoc.15.128

• -producing bacterium Massilia sp. NR 4-1 and predicted to direct the biosynthesis of a molecule that is structurally related to the thiazoline-containing siderophore micacocidin. In order to track this compound, we analyzed the metabolic profiles of Massilia cultures grown under different iron concentrations

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

• library of androstanic derivatives 21 (Figure 2B) and their reduced analogues bearing the 3β-hydroxy group were biologically tested showing antifungal activity against Fusarium virguliforme and Fusarium solani. The generation of this compound library suffered from the formation of the Passerini reaction

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

• (CYP11B2) and 11β-hydroxylase (CYP11B1), which is responsible for cortisol production [35]. This compound is under development for the treatment of Cushing's syndrome and pituitary ACTH hypersecretion [36]. From this point of view the approach to pyrrolo[1,2-c]imidazole moiety by using acyclic methylene

Mechanistic investigations on multiproduct β-himachalene synthase from Cryptosporangium arvum

• Jan Rinkel and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2019, 15, 1008–1019, doi:10.3762/bjoc.15.99

• comparison with commercially available standards (Figures S6–S9, Supporting Information File 1). The non-enzymatic degradation of GPP as a background reaction to 15 resulted in a substantial loss of stereoinformation for this compound (7% ee). Also the cyclised products 10, 11 and 13 where not obtained in

• most products. However, in the side product 7 C-1 remains untouched after 1,11-cyclisation, which allows to investigate the stereochemical course of the first cyclisation step for this compound. First, the absolute configuration of 7 was assigned as shown in Figure 2 from the incubation experiments

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

• of the wavelengths, the electron-withdrawing ALA-amide unit was electronically decoupled from the DAT chromophore by introducing a propylene spacer. Thus, diethyl DAT was first equipped with an N-Alloc-protected 3-aminopropyl side chain at one nitrogen function following a literature protocol. This

• compound, 5, was then submitted to reductive amination with para-(trifluoromethyl)benzaldehyde. After Alloc deprotection, the side chain was amidated with ALA following the same COMU–DIPEA protocol as described for 3. The second target compound 7 was obtained in 59% yield over three steps. Indeed, the

Towards the preparation of synthetic outer membrane vesicle models with micromolar affinity to wheat germ agglutinin using a dialkyl thioglycoside

• Dimitri Fayolle,
• Nathalie Berthet,
• Bastien Doumeche,
• Olivier Renaudet,
• Peter Strazewski and
• Michele Fiore

Beilstein J. Org. Chem. 2019, 15, 937–946, doi:10.3762/bjoc.15.90

• 8 showed the highest inhibitory effect of this study with an IC50 of 11 µM corresponding to a 3000-fold improvement compared to the monomer control. This result suggests a higher participation of sugar units in the lectin binding for this compound. Docking calculation for model glycolipids To

A diastereoselective approach to axially chiral biaryls via electrochemically enabled cyclization cascade

• Hong Yan,
• Zhong-Yi Mao,
• Zhong-Wei Hou,
• Jinshuai Song and
• Hai-Chao Xu

Beilstein J. Org. Chem. 2019, 15, 795–800, doi:10.3762/bjoc.15.76

• stereoselectivity of the reaction was not controlled by relative thermodynamic stability of the diastereomers. The major isomer of 3c, which contained a sterically less demanding Ph group at the R1 position (cf. Table 1), did not isomerize at room temperature for 1 year. However, heating a solution of this compound

Synthesis of polydicyclopentadiene using the Cp₂TiCl₂/Et₂AlCl catalytic system and thin-layer oxidation of the polymer in air

• Zhargolma B. Bazarova,
• Ludmila S. Soroka,
• Alex A. Lyapkov,
• Мekhman S. Yusubov and
• Francis Verpoort

Beilstein J. Org. Chem. 2019, 15, 733–745, doi:10.3762/bjoc.15.69

• . Indeed, as reported in previously published papers [15][16], the colored blue complex under these conditions is caused by a compound containing Ti(III) or Ti(IV). This compound corresponds to the final [Cp2TiEt]+·[AlEtCl3]− complex. The presence of an isosbestic point at 656 nm indicates the presence of

The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives

• Tilman Lechel,
• Roopender Kumar,
• Mrinal K. Bera,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2019, 15, 655–678, doi:10.3762/bjoc.15.61

• give α-methoxy carbonyl compound 7. The isolation of this compound supports our mechanistic proposal as shown in Scheme 2 and it shows that sterically very hindered carboxylic acids are probably poor components in the route to β-ketoenamides. A systematic study of this possible limitation was not

• (see Scheme 10). This compound was converted into PM59 by the standard cyclocondensation reaction (Scheme 15) leading to a pyridin-4-ol moiety that was converted to the nonaflate. Compound PM60 bears a pyrimidyl and a pyridinyl substituent at the 2,2’-position of the biphenyl part [41]. Synthesis of

• approach to complex heterocycles. The aldehyde PM69 was further converted into the terminal alkyne PM73 by employing the Bestmann–Ohira protocol (Scheme 21). After its Sonogashira reaction with iodobenzene to the intermediate disubstituted alkyne PM74 this compound was converted into furopyrimidine