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

The B & B approach: Ball-milling conjugation of dextran with phenylboronic acid (PBA)-functionalized BODIPY

• Patrizia Andreozzi,
• Lorenza Tamberi,
• Elisamaria Tasca,
• Gina Elena Giacomazzo,
• Marta Martinez,
• Mirko Severi,
• Marco Marradi,
• Stefano Cicchi,
• Sergio Moya,
• Giacomo Biagiotti and
• Barbara Richichi

Beilstein J. Org. Chem. 2020, 16, 2272–2281, doi:10.3762/bjoc.16.188

• properties of BODIPY and the biocompatibility of dextran. The BODIPY dextran nanoparticles were characterized regarding their size, morphology, polarity, and toxicity in vitro. We demonstrate the feasibility of mechanochemistry for boronic ester formation [23] to a glycan polymer as a route of conjugation

• assemblies of the conjugate Dex-1b a simple experiment with pyrene was conducted. It is well known that the fluorescence spectrum of pyrene is very sensitive to the polarity of the environment [37]. Indeed, the ratio (I1/I3) between the first (I1 = 372 nm) and the third bands (I3 = 383 nm) in the emission

• spectra of pyrene could be used to estimate the polarity of the environment of the dye in an empirical way. The ratio of the two bands in an environment of unknown polarity can be compared with the values of this ratio in solvents of known polarity. The spectrum of pyrene dissolved in a water dispersion

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

Regioselective cobalt(II)-catalyzed [2 + 3] cycloaddition reaction of fluoroalkylated alkynes with 2-formylphenylboronic acids: easy access to 2-fluoroalkylated indenols

• Tatsuya Kumon,
• Miroku Shimada,
• Jianyan Wu,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2020, 16, 2193–2200, doi:10.3762/bjoc.16.184

• to 2-fluoroalkylated indenols in good yield. Moreover, the side product was a small amount of 3-fluoroalkylated indanones, which was easily separated from the 2-fluoroalkylated indenols due to the lower polarity of indanones compared to indenols. Finally, 2-fluoroalkylated indenol was simply

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

• . Moreover, the inertness of C(sp3)–H bonds due to their high homolytic bond dissociation energy and low polarity necessitate highly reactive reagents/intermediates for their activation, which may encourage off-site activity with other functional groups present in the target molecule and lead to a poor

• ][51][52][53][54][55][56][57]. Accordingly, the reactivity and selectivity correlate with the homolytic C–H bond dissociation enthalpy and polarity matching principles [58][59][60][61][62][63][64]. One of the advantages of polarity matching is that it enables C(sp3)–H bond activations that are not

• dictated by the thermodynamic driving force of the hydrogen atom transfer step (which depends on the stability of the resulting radical) or by the relative BDE of C–H bonds. Thus, it is possible to homolytically cleave stronger C–H bonds in the presence of weaker C–H bonds if the polarity of the stronger C

Clustering and curation of electropherograms: an efficient method for analyzing large cohorts of capillary electrophoresis glycomic profiles for bioprocessing operations

• Ian Walsh,
• Matthew S. F. Choo,
• Sim Lyn Chiin,
• Amelia Mak,
• Shi Jie Tay,
• Pauline M. Rudd,
• Yang Yuansheng,
• Andre Choo,
• Ho Ying Swan and
• Terry Nguyen-Khuong

Beilstein J. Org. Chem. 2020, 16, 2087–2099, doi:10.3762/bjoc.16.176

• µm i.d. uncoated bare fused capillary, HR-NCHO separation gel buffer (Sciex). The applied electric field strength was 1500 V/cm with the cathode at the injection side and the anode at the detection side (reversed polarity). Samples were electrokinetically injected using 1kV for 5 s. For migration

Metal-free synthesis of phosphinoylchroman-4-ones via a radical phosphinoylation–cyclization cascade mediated by K₂S₂O₈

• Qiang Liu,
• Weibang Lu,
• Guanqun Xie and
• Xiaoxia Wang

Beilstein J. Org. Chem. 2020, 16, 1974–1982, doi:10.3762/bjoc.16.164

• sciences over the last few years [1][4][5]. In general, chroman-4-one derivatives could be obtained via a polarity reversal strategy enabled by the N-heterocyclic carbene (NHC)-catalyzed intramolecular Stetter reaction [6][7][8]. Besides, chroman-4-one derivatives were also constructed via intramolecular

Selective preparation of tetrasubstituted fluoroalkenes by fluorine-directed oxetane ring-opening reactions

• Clément Q. Fontenelle,
• Thibault Thierry,
• Romain Laporte,
• Emmanuel Pfund and
• Thierry Lequeux

Beilstein J. Org. Chem. 2020, 16, 1936–1946, doi:10.3762/bjoc.16.160

• the latter was not yet synthetized. It is expected that the introduction of fluorine into the carbon–carbon double bond, in a position equivalent to the ring oxygen of the naturally occurring nucleotide, will improve molecular recognition and activity. In addition, the polarity of the nucleotide and

Design, synthesis and application of carbazole macrocycles in anion sensors

• Alo Rüütel,
• Ville Yrjänä,
• Sandip A. Kadam,
• Indrek Saar,
• Mihkel Ilisson,
• Astrid Darnell,
• Kristjan Haav,
• Tõiv Haljasorg,
• Lauri Toom,
• Johan Bobacka and
• Ivo Leito

Beilstein J. Org. Chem. 2020, 16, 1901–1914, doi:10.3762/bjoc.16.157

• -life sensing, also influences binding [4]. Within an ion-selective electrode (ISE), lipophilicity is mostly contributed by the low polarity membrane, which is commonly based on plasticized PVC [5]. One possible receptor family for carboxylates is based on the biscarbazolylurea moiety (Figure 1). This

Polarity effects in 4-fluoro- and 4-(trifluoromethyl)prolines

• Vladimir Kubyshkin

Beilstein J. Org. Chem. 2020, 16, 1837–1852, doi:10.3762/bjoc.16.151

• the interplay between the substituents and the main chain groups of the amino acid residue. This study aims to showcase the polarity-related effects that arise from the interaction between the functional groups in molecular models. Properties such as conformation, acid–base transition, and amide-bond

• C4-exo conformation of the pyrrolidine ring. Keywords: amino acids; cis–trans isomerism; fluorine; polarity; proline; Introduction Polarity is among the key features essential for understanding the behavior of organic molecules of biological origin. In particular, there is a set of polarity-related

• hydrophobic, while the introduction of a polar or an ionizable group makes it hydrophilic. Two amino acids stand out from the dualistic hydrophilic/hydrophobic classification: glycine and proline (Figure 1A) [1]. The origin of their effect onto the structure polarity is not due to the presence of additional

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• catalysts and further cross-coupling-type reactivity provides a unique tool to solve this critical issue. Besides, dual catalytic systems enable also umpolung-type reactivity, thus promoting unique bond-forming reactions, inaccessible via standard approaches due to the polarity mismatch. Finally, the

Rearrangement of o-(pivaloylaminomethyl)benzaldehydes: an experimental and computational study

• Csilla Hargitai,
• Györgyi Koványi-Lax,
• Tamás Nagy,
• Péter Ábrányi-Balogh,
• András Dancsó,
• Gábor Tóth,
• Judit Halász,
• Angéla Pandur,
• Gyula Simig and
• Balázs Volk

Beilstein J. Org. Chem. 2020, 16, 1636–1648, doi:10.3762/bjoc.16.136

• close dielectric constant (ε = 4.7 for CHCl3 and 8.9 for DCM) [28], the similar polarity index (P = 2.7 for CHCl3 and 3.1 for DCM) [29][30][31], and the very close dipole moment (1.15 for CHCl3, 1.14 for DCM) [32], the conformation of the compounds should be almost the same in the NMR solvent and in the

Synthesis of new dihydroberberine and tetrahydroberberine analogues and evaluation of their antiproliferative activity on NCI-H1975 cells

• Giacomo Mari,
• Lucia De Crescentini,
• Serena Benedetti,
• Francesco Palma,
• Stefania Santeusanio and
• Fabio Mantellini

Beilstein J. Org. Chem. 2020, 16, 1606–1616, doi:10.3762/bjoc.16.133

• -bromohydrazones 1a–n (Scheme 2). All the hydrazono-DHBERs 2a–n directly precipitate as pure products in the reaction medium with yields ranging from poor to good (30–83%). Probably the low affinity of the iminium and hydrazone groups of compounds 2a–n with a medium-low polarity solvent such as DCM causes their

Mechanochemical green synthesis of hyper-crosslinked cyclodextrin polymers

• Alberto Rubin Pedrazzo,
• Fabrizio Caldera,
• Marco Zanetti,
• Silvia Lucia Appleton,
• Nilesh Kumar Dhakar and
• Francesco Trotta

Beilstein J. Org. Chem. 2020, 16, 1554–1563, doi:10.3762/bjoc.16.127

• allow them to act as polyfunctional monomers, permitting the crosslinking with bi- or multifunctional chemicals, such as dianhydrides, diisocyanates, diepoxides, and dicarboxylic acids, etc. The polarity and size of the polymer network can be easily tuned by varying the type of the crosslinker and

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

• generated with a yield of 43–75% (Scheme 13). Reductive dehalogenation reactions In 2013, Curran and co-workers reported a light-induced dehalogenative reduction with polarity reversion catalyzed by diphenyl disulfide or boryl bissulfide (diMe–Imd–BH(SPh)2) as the catalyst and 1,3-dimethylimidazol-2

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• -donating substituents present in the allenes enhanced the overall reaction rate. There was little effect of the solvent polarity on the reaction rate. The formation of thietanes involved the excited triplet thiones and the π-bond of allenes [66]. In 1984, Bos and co-workers realized the photocycloaddition

Activated carbon as catalyst support: precursors, preparation, modification and characterization

• Melanie Iwanow,
• Tobias Gärtner,
• Volker Sieber and
• Burkhard König

Beilstein J. Org. Chem. 2020, 16, 1188–1202, doi:10.3762/bjoc.16.104

• basic conditions, the pore size distribution and the chemical properties on the surface can be adjusted (polarity and hydrophobicity) according to the envisaged application. In addition, metal particles can be recovered simply by burning the carbon support [1][2]. Thus, porous carbon materials represent

Synthesis and properties of quinazoline-based versatile exciplex-forming compounds

• Rasa Keruckiene,
• Simona Vekteryte,
• Ervinas Urbonas,
• Matas Guzauskas,
• Eigirdas Skuodis,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 1142–1153, doi:10.3762/bjoc.16.101

• -transfer (CT) transitions [20]. The PLQY quantum yields of the dilute solutions did not exceed 2%. The dependence of the emission wavelengths of the derivatives on the solvent polarity was also tested. Figure 5 shows the emission spectra of the compounds dissolved in three solvents with increasing

• polarities, i.e., toluene (0.099), tetrahydrofuran (0.207) and dimethylformamide (0.4) (values in parentheses are the solvent polarities relative to water) [21]. The PL spectra of the solutions of compound 3 appeared to be solvent-polarity independent as only the structured emission band of the locally

• the 1LE transition at 375 nm. A 1CT state could be formed for compound 1 as evidenced by the PL spectrum of its solution in low-polarity toluene. A weak low energy 1CT band was also observed for the solution in THF with moderate polarity (see the zoomed spectrum of THF solution of compound 1, Figure

The charge-assisted hydrogen-bonded organic framework (CAHOF) self-assembled from the conjugated acid of tetrakis(4-aminophenyl)methane and 2,6-naphthalenedisulfonate as a new class of recyclable Brønsted acid catalysts

• Svetlana A. Kuznetsova,
• Alexander S. Gak,
• Yulia V. Nelyubina,
• Vladimir A. Larionov,
• Han Li,
• Michael North,
• Vladimir P. Zhereb,
• Alexander F. Smol'yakov,
• Artem O. Dmitrienko,
• Michael G. Medvedev,
• Igor S. Gerasimov,
• Ashot S. Saghyan and
• Yuri N. Belokon

Beilstein J. Org. Chem. 2020, 16, 1124–1134, doi:10.3762/bjoc.16.99

• , including the ring opening of epoxides by water and alcohols. A Diels–Alder reaction between cyclopentadiene and methyl vinyl ketone was also catalyzed by F-1 in heptane. Depending on the polarity of the solvent mixture, the CAHOF F-1 could function as a purely heterogeneous catalyst or partly dissociate

• efficiency of the reaction dropping as the size of the alcohol was increased and its polarity decreased (Table 2, runs 1–3). Water could also be used as the nucleophile (Table 2, runs 4 and 5) and led to the trans-cyclohexane diol 6 under the same experimental conditions used for the styrene oxide ring

• . Depending on the polarity of the solvent mixture, F-1 could function as a purely heterogeneous catalyst or as a reservoir, providing some soluble F-1 as the real catalyst. In all cases the catalyst could easily be recovered and recycled. The system has the potential for future elaboration, for example, by