Regioselective N-alkylation of the 1H-indazole scaffold; ring substituent and N-alkylating reagent effects on regioisomeric distribution

• Ryan M. Alam and
• John J. Keating

Beilstein J. Org. Chem. 2021, 17, 1939–1951, doi:10.3762/bjoc.17.127

• solubility of Cs2CO3 in toluene and 1,4-dioxane [24]. Using K2CO3 in MeCN, Longworth et al. have obtained 10 with a similar degree of N-1 regioselectivity (ratio N-1:N-2 = 2.8:1) [26]. However, altering solvent polarity when employing 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a base (Table 1, entries 15–17

2,4-Bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridines: synthesis and photophysical properties

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli,
• Noureddine Chaaben,
• Kamel Alimi,
• Stefan Jopp and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 1629–1640, doi:10.3762/bjoc.17.115

• polarity difference. In fact, derivative 4f shows the highest dipole moment of 4.276 D as compared to 4a (0.698 D). As shown in Table 5, the ionization potential (IP) and electron affinity (EA) of tetrahydroacridines are almost identical. In addition, EHOMO and ELUMO do not change notably and the

Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation

• Premansh Dudhe,
• Mena Asha Krishnan,
• Kratika Yadav,
• Diptendu Roy,
• Krishnan Venkatasubbaiah,
• Biswarup Pathak and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2021, 17, 1453–1463, doi:10.3762/bjoc.17.101

• absorption maximum (λmax) was observed at 230 nm for 3ac in DMSO (Figure 3, left side). The fluorescence studies carried out for 3ac in four different solvents revealed that the emission maxima shifted bathochromically by almost 40 nm upon changing the solvent polarity, for instance, from non-polar hexane to

A new glance at the chemosphere of macroalgal–bacterial interactions: In situ profiling of metabolites in symbiosis by mass spectrometry

• Marine Vallet,
• Filip Kaftan,
• Veit Grabe,
• Fatemeh Ghaderiardakani,
• Simona Fenizia,
• Aleš Svatoš,
• Georg Pohnert and
• Thomas Wichard

Beilstein J. Org. Chem. 2021, 17, 1313–1322, doi:10.3762/bjoc.17.91

• single Ulva individuals were targeted visually and ablated with a laser spot size of approximately 10 μm in positive and negative polarity in a mass range from m/z 100 to m/z 1000. The other parameters stayed like for the MSI mode. In profiling, the same area of the rhizoid and the tip of the thallus of

• Ulva samples. In the late exponential stage, bacterial monoculture was recovered from agar plates with a 10 µL loop and diluted in 100 µL of sterile water. Five microliters of the solution were spotted onto a glass slide and analysed in AP-SMALDI-HRMS mode in positive and negative polarity. The data

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

• . Furthermore, it usually displays a high polarity and consequently good aqueous solubility. These features render biguanides an attractive chemical function in medicinal chemistry, where it tends to establish as a valuable pharmacophore for drug discovery. Currently, seven biguanide drugs are commercially

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• enantioselectivity varied with the polarity of the solvent. The optimization study disclosed that the enantioselectivity increases with the decrease of the polarity of the solvent (Scheme 68). Yu and co-workers reported a novel segment-coupling Prins cyclization involving sequential benzylic/allylic C–H bond

A chromatography-free and aqueous waste-free process for thioamide preparation with Lawesson’s reagent

• Ke Wu,
• Yichen Ling,
• An Ding,
• Liqun Jin,
• Nan Sun,
• Baoxiang Hu,
• Zhenlu Shen and
• Xinquan Hu

Beilstein J. Org. Chem. 2021, 17, 805–812, doi:10.3762/bjoc.17.69

• the LR upon thio-substitution [11][12][13]. It has been observed that the polarity of compound A is generally similar to the desired products, thus making the purification of the desired products by extraction operations less efficient. Therefore, the purification is rather difficult and usually a

• separation by careful column chromatography is necessary because of both the similar polarity and the stoichiometric amount of the formed compound A. With regard to this, the use of LR was always limited to small-scale preparations [6][8]. Other than the exploration of potential surrogates of LR for the

• temperature and a new spot with a much higher polarity was observed on the TLC plate. With a mixed solvent of ethyl acetate/petroleum ether 1:3 as the eluent, the Rf of compound A was around 0.5, while the Rf of the newly generated compound was at around 0.05 either from MeOH or EtOH treatment. Later, the new

Biochemistry of fluoroprolines: the prospect of making fluorine a bioelement

• Vladimir Kubyshkin,
• Rebecca Davis and
• Nediljko Budisa

Beilstein J. Org. Chem. 2021, 17, 439–460, doi:10.3762/bjoc.17.40

• containing fluorine have been particularly well characterized for their use as spectroscopic probes, mainly in 19F NMR applications [12][13][14][15]. It is typical that the incorporation of fluorine into certain molecular fragments changes the local polarity as well as the electronic and conformational

• based on the recognition of fluoroprolines by the native enzyme aminoacyl-tRNA synthetase (vide infra) proves this assumption. 2.2 Local polarity Another important feature of fluoroprolines is their local electrostatic potential (local polarity). In proline, position 4 contains a positive surface

• Lipophilicity The impact of fluorine substitution on the global polarity of the molecule is another parameter that should be considered. The global polarity can be typically analyzed by measurements of the molecular partitioning, e.g., the lipophilicity index logP. For aliphatic organofluorine compounds, this

Coupling biocatalysis with high-energy flow reactions for the synthesis of carbamates and β-amino acid derivatives

• Alexander Leslie,
• Thomas S. Moody,
• Megan Smyth,
• Scott Wharry and
• Marcus Baumann

Beilstein J. Org. Chem. 2021, 17, 379–384, doi:10.3762/bjoc.17.33

• biocatalyzed process for the tagging of residual benzyl alcohol. Initially the removal of benzyl alcohol proved challenging due to its high boiling point (205 °C) and its co-polarity with many of the carbamate products. As this rendered evaporation and column chromatography ineffective, an alternative approach

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• solvolysis rate for derivatives 13f or 13g and the solvent polarity parameter YOTs [45]. The solvent participation in the solvolysis of these tertiary benzylic tosylates was thus defined as “unimportant” by the authors. Gassman and Harrington successfully measured the solvolysis kinetics of CF3-substituted

¹⁹F NMR as a tool in chemical biology

• Diana Gimenez,
• Aoife Phelan,
• Cormac D. Murphy and
• Steven L. Cobb

Beilstein J. Org. Chem. 2021, 17, 293–318, doi:10.3762/bjoc.17.28

Total synthesis of decarboxyaltenusin

• Lucas Warmuth,
• Aaron Weiß,
• Marco Reinhardt,
• Anna Meschkov,
• Ute Schepers and
• Joachim Podlech

Beilstein J. Org. Chem. 2021, 17, 224–228, doi:10.3762/bjoc.17.22

• product, but purification and isolation of the product by column chromatography was not possible ‒ neither with conventional nor with reversed phase methods. It turned out that the high polarity of the triol complicated its separation from other polar side products. To circumvent this problem, we decided

Supramolecular polymers with reversed viscosity/temperature profile for application in motor oils

• Jan-Erik Ostwaldt,
• Christoph Hirschhäuser,
• Stefan K. Maier,
• Carsten Schmuck and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2021, 17, 105–114, doi:10.3762/bjoc.17.11

• concentration of the solution and on the polarity of the solvent. This effect can counteract the loss of viscosity of the solvent at elevated temperatures, thus opening an application of our systems as viscosity index improvers (VIIs) in working fluids. This was tested for different motor oils and led to the

Progress in the total synthesis of inthomycins

• Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

• at room temperature to give (E,E,E)-(+)-11 in 79% yield. This compound was then transformed successfully to (inthomycin C ((−)-3) in a four-step sequence (Scheme 10). The difference in Hatakeyama’s approach to inthomycin C ((–)-3) is the polarity reversal of the Stille coupling components relative to

Amine–borane complex-initiated SF₅Cl radical addition on alkenes and alkynes

• Audrey Gilbert,
• Pauline Langowski,
• Marine Delgado,
• Laurent Chabaud,
• Mathieu Pucheault and
• Jean-François Paquin

Beilstein J. Org. Chem. 2020, 16, 3069–3077, doi:10.3762/bjoc.16.256

• ). However, the latter led to a full conversion, which is not the case with the reaction in hexane, with a conversion of 93%. Considering the similar polarity of the starting material 1 and the final product 2a, we chose the reaction conditions in MTBE as the optimal conditions, in order to facilitate the

Metal-free nucleophilic trifluoromethylselenolation via an iodide-mediated umpolung reactivity of trifluoromethylselenotoluenesulfonate

• Kevin Grollier,
• Alexis Taponard,
• Arnaud De Zordo-Banliat,
• Emmanuel Magnier and
• Thierry Billard

Beilstein J. Org. Chem. 2020, 16, 3032–3037, doi:10.3762/bjoc.16.252

• that trifluoromethanesulfenamides, electrophilic trifluoromethylthiolation reagents, could also perform nucleophilic trifluoromethylthiolations through the transient formation of a CF3SI species which presented an inverted polarity [49][50]. Based on a similar approach, we hypothesized that the CF3SeI

• species could also possess the CF3Seδ−–Iδ+ inverted polarity. Thus, based on the previously developed conditions, reagent 1a was reacted with benzyl bromide (2a) in the presence of tetrabutylammonium iodide (TBAI) in acetone at 40 °C (Table 1, entry 1). The observed result was moderate (Table 1, entry 1

• of iodide (from TBAI) reacts with the reagent 1a to produce the transient species CF3SeI with an inverted polarity on the selenium atom. This compound then undergoes the attack of the second equivalent of iodide to generate the CF3Se− anion with releasing of I2. Finally, the nucleophilic CF3Se− can

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

• mixture (Table 2). All the compounds exhibited an up-down tendency in intensity upon increasing the water fraction. Compounds H, Me and t-Bu showed a progressive red-shift with growing water content, owing to the increased solvent polarity and dielectric constant favoring the CT character of the emissive

• , 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

Fluorine effect in nucleophilic fluorination at C4 of 1,6-anhydro-2,3-dideoxy-2,3-difluoro-β-D-hexopyranose

• Danny Lainé,
• Vincent Denavit,
• Olivier Lessard,
• Laurie Carrier,
• Charles-Émile Fecteau,
• Paul A. Johnson and
• Denis Giguère

Beilstein J. Org. Chem. 2020, 16, 2880–2887, doi:10.3762/bjoc.16.237

• groups by fluorine atoms arise from their similarities in term of polarity and isosteric relationship [3][8]. For a long time, fluorinated carbohydrates have been used as a method to stabilize glycosidic bonds [9][10][11] or for epitope mapping [12][13]. More recently, heavily fluorinated carbohydrates

Dirhamnolipid ester – formation of reverse wormlike micelles in a binary (primerless) system

• David Liese,
• Hans Henning Wenk,
• Xin Lu,
• Jochen Kleinen and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2020, 16, 2820–2830, doi:10.3762/bjoc.16.232

• polarity. An unusual behavior was observed when the dirhamnolipid esters were added to toluene. The more polar short chain length dirhamnolipid esters and 7 form a gel-like texture in toluene, indicating the formation of a network structure of the surfactant molecules. With increasing chain length of the

Selective recognition of ATP by multivalent nano-assemblies of bisimidazolium amphiphiles through “turn-on” fluorescence response

• Rakesh Biswas,
• Surya Ghosh,
• Shubhra Kanti Bhaumik and
• Supratim Banerjee

Beilstein J. Org. Chem. 2020, 16, 2728–2738, doi:10.3762/bjoc.16.223

• reported lifetimes for monomeric pyrenes [66][67]. In aqueous buffer, the lifetime of the 395 nm band decreased (≈15–35 ns, Supporting Information File 1, Table S3) probably owing to the increment in the solvent polarity [68]. The average lifetime values (τavg) of the excimeric bands of PBIm10, PBIm12 and

Vicinal difluorination as a C=C surrogate: an analog of piperine with enhanced solubility, photostability, and acetylcholinesterase inhibitory activity

• Yuvixza Lizarme-Salas,
• Alexandra Daryl Ariawan,
• Ranjala Ratnayake,
• Hendrik Luesch,
• Angela Finch and
• Luke Hunter

Beilstein J. Org. Chem. 2020, 16, 2663–2670, doi:10.3762/bjoc.16.216

• F–C–C=O motifs have shown that the rotamer populations can change, depending on the polarity of the solvent [22][23]. The rotamers I and IV (Figure 1, boxed) would appear to provide the closest structural match with compound 1, but in a highly polar medium the more polar rotamers II and V might

NMR Spectroscopy of supramolecular chemistry on protein surfaces

• Peter Bayer,
• Anja Matena and
• Christine Beuck

Beilstein J. Org. Chem. 2020, 16, 2505–2522, doi:10.3762/bjoc.16.203

Conformational preferences of fluorine-containing agrochemicals and their implications for lipophilicity prediction

• Daniela Rodrigues Silva,
• Joyce K. Daré and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2020, 16, 2469–2476, doi:10.3762/bjoc.16.200

• Daniela Rodrigues Silva Joyce K. Dare Matheus P. Freitas Department of Chemistry, Federal University of Lavras, 37200–900, Lavras–MG, Brazil 10.3762/bjoc.16.200 Abstract Molecular polarity governs lipophilicity, which in turn determines important agrochemical and environmental properties, such as

• soil sorption and bioconcentration of organic compounds. Since the C–F bond is the most polar in organic chemistry, the orientation of fluorine substituents originating from the rotation around C–C(F) bonds should affect the polarity and, consequently, the physicochemical and biological properties of

• substituents originated from the rotation of fluorine-containing C–C bonds should affect the polarity and, therefore, the physicochemical and biological properties of organofluorine compounds. However, there is a lack of studies that explain how these well-known conformational effects directly alter

Formation of an exceptionally stable ketene during phototransformations of bicyclo[2.2.2]oct-5-en-2-ones having mixed chromophores

• Asitanga Ghosh

Beilstein J. Org. Chem. 2020, 16, 2297–2303, doi:10.3762/bjoc.16.190

• spectrum of the crude reaction mixture. Since the polarity of the two methyl esters is very similar, we could not separate them through column chromatography. However, 11a was separated in a trace amount through repeated preparative TLC. Moreover, when a degassed solution of 7a in methanol was irradiated

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

• with different polarities and showed absorption in the visible region and green-red emission with low quantum yields. The absorption and the emission maxima were shifted bathocromically by increasing the solvent’s polarity. However, there was no correlation with the polarity parameters of the solvents

• , Figures S41 and S42 in Supporting Information File 1). Absorption and emission properties To assess the effect of the solvent on the absorption and emission spectra of 3–7 and 8–12 (c = 10 μM for absorption, and c = 1 μM for emission), various solvents with different polarity were employed at room

• –Reichardt polarity parameters (ET30, Dimroth–Reichardt polarity parameter in kcal mol−1 of MeOH = 55.4, ACN = 45.6, DMSO = 45.1, DCM = 40.7, THF = 37.4, and PhMe = 33.9) were used in the study [38]. In addition, the absorption spectra of all dyes were obtained by TD-DFT calculations using the PCM model. The