Curcuminoid–BF₂ complexes: Synthesis, fluorescence and optimization of BF₂ group cleavage

• Henning Weiss,
• Jeannine Reichel,
• Helmar Görls,
• Kilian Rolf Anton Schneider,
• Mathias Micheel,
• Michael Pröhl,
• Michael Gottschaldt,
• Benjamin Dietzek and
• Wolfgang Weigand

Beilstein J. Org. Chem. 2017, 13, 2264–2272, doi:10.3762/bjoc.13.223

• known property for curcumin and its derivatives [32][33], we investigated the solvatochromism of 2b as an example compound in five different solvents (Figure 3). Solvents were chosen by their ET(30) values of polarity as determined by Reichardt [34]. With rising solvent polarity, the vibrational

Phosphonic acid: preparation and applications

• Charlotte M. Sevrain,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2017, 13, 2186–2213, doi:10.3762/bjoc.13.219

• first pKa ranging from 1.1 to 2.3 and the second acidity which features a pKa ranging from 5.3 to 7.2 [11]. The values strongly depend on the electronic properties induced by the substituent R. It must be noted that due to the high polarity of the phosphonic acid function, the purification of phosphonic

• with triphenylphosphine functionalized either by two or three phosphonic acid sodium salts; the former being more water soluble than the later [24]. This behavior is associated to the fact that the trisphosphonic acid sodium salt was already solvated at the solid state. The high polarity of the

• product since crystallization, precipitation and dialysis constitute the possible methods of purification. The purification by chromatography requires, due to the high polarity of phosphonic acids, reversed-phase chromatography and is therefore limited to preparative RP-HPLC [218]. Despites these

Enzymatic separation of epimeric 4-C-hydroxymethylated furanosugars: Synthesis of bicyclic nucleosides

• Neha Rana,
• Manish Kumar,
• Vinod Khatri,
• Jyotirmoy Maity and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2017, 13, 2078–2086, doi:10.3762/bjoc.13.205

• concentrated under reduced pressure to afford a colourless oil. The two products formed in the reaction had different polarity and were easily separated by column chromatography over silica gel in quantitative yields. The structure elucidation of the two products revealed that Novozyme®-435 exhibited exclusive

Remarkable functions of sn-3 hydroxy and phosphocholine groups in 1,2-diacyl-sn-glycerolipids to induce clockwise (+)-helicity around the 1,2-diacyl moiety: Evidence from conformation analysis by ¹H NMR spectroscopy

• Yoshihiro Nishida,
• Mengfei Yuan,
• Kazuo Fukuda,
• Kaito Fujisawa,
• Hirofumi Dohi and
• Hirotaka Uzawa

Beilstein J. Org. Chem. 2017, 13, 1999–2009, doi:10.3762/bjoc.13.196

• methanol-d4 and/or D2O around the 3-OH group as well as the increasing polarity of the mixed solvent. As judged from the chemical shift change in the H3 signals, the solvation is possibly saturated in the mixed solvent with 10% methanol-d4 (C/M = 10:1). In the solvent containing more than 33% methanol-d4

A novel application of 2-silylated 1,3-dithiolanes for the synthesis of aryl/hetaryl-substituted ethenes and dibenzofulvenes

• Grzegorz Mlostoń,
• Paulina Pipiak,
• Róża Hamera-Fałdyga and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 1900–1906, doi:10.3762/bjoc.13.185

• analysis in CDCl3 solution. The crude products were purified by column chromatography (petroleum ether/CH2Cl2, increasing polarity to CH2Cl2). Reactions of diphenyl and phenyl selenophen-2-yl thioketones with diazomethane (CH2N2; Sel = selenophen-2-yl). Reaction of diaryl thioketones with

Conformational impact of structural modifications in 2-fluorocyclohexanone

• Francisco A. Martins,
• Josué M. Silla and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2017, 13, 1781–1787, doi:10.3762/bjoc.13.172

• population of the equatorial conformer increased with the solvent polarity, as dipolar repulsion between Y and F decreases in solvents with increasing dielectric constants. Nuclear magnetic resonance (NMR) parameters, namely chemical shifts and coupling constants, can be useful to provide information on

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

New electroactive asymmetrical chalcones and therefrom derived 2-amino- / 2-(1H-pyrrol-1-yl)pyrimidines, containing an N-[ω-(4-methoxyphenoxy)alkyl]carbazole fragment: synthesis, optical and electrochemical properties

• Daria G. Selivanova,
• Alexei A. Gorbunov,
• Olga A. Mayorova,
• Alexander N. Vasyanin,
• Igor V. Lunegov,
• Elena V. Shklyaeva and
• Georgii G. Abashev

Beilstein J. Org. Chem. 2017, 13, 1583–1595, doi:10.3762/bjoc.13.158

• colourless (2a,b) to orange (7a,b). Under UV irradiation (λeх = 315–390 nm) the luminescence of solutions varies from blue (2a,b) to orange (7a,b). It has been found out that UV-irradiated solutions of the obtained chromophores 6a,b–8a,b change their colours in different solvents of various polarity; for

• ], which exhibit the redshift of a longwave absorption/emission maxima along with the increase of a solvent polarity. Maybe this is a result of a molecule symmetry breaking in its excited state [27]. Taking into account all the factors mentioned above, we have started the investigation of solvatochromic

• neighboring charge or dipole by virtue of nonspecific dielectric interactions [28]. This parameter was determined by Kamlet, Abboud and Taft [29]. The measurement results are displayed in Figure 2. The obtained data demonstrate that the increase of solvent polarity affords the redshift of the longwave UV

Base-promoted isomerization of CF₃-containing allylic alcohols to the corresponding saturated ketones under metal-free conditions

• Yoko Hamada,
• Tomoko Kawasaki-Takasuka and
• Takashi Yamazaki

Beilstein J. Org. Chem. 2017, 13, 1507–1512, doi:10.3762/bjoc.13.149

• . Polarity seemed to affect the reaction significantly, and aprotic MeCN, DMF, and DMSO (Table 2, entries 9, 10, and 12, respectively) showed a similar potency to THF with respect to chemical yields of 7a. Further investigation clarified that toluene was the best solvent from the standpoint of the material

Sustainable synthesis of 3-substituted phthalides via a catalytic one-pot cascade strategy from 2-formylbenzoic acid with β-keto acids in glycerol

• Lina Jia and
• Fuzhong Han

Beilstein J. Org. Chem. 2017, 13, 1425–1429, doi:10.3762/bjoc.13.139

• , as an environmentally friendly reaction medium, has received increasing interest for organic reactions because of its peculiar physical and chemical properties such as polarity, low toxicity, biodegradability, high boiling point, and ready availability from renewable feed stocks [31]. Many organic

An improved preparation of phorbol from croton oil

• Alberto Pagani,
• Simone Gaeta,
• Andrei I. Savchenko,
• Craig M. Williams and
• Giovanni Appendino

Beilstein J. Org. Chem. 2017, 13, 1361–1367, doi:10.3762/bjoc.13.133

• unclear. The use of THF was inspired by the work of Seebach on the solubility of peptides in ether-type organic solvents in the presence of certain alkaline cations [20], and it is not unconceivable that the interaction with sodium ions substantially diversifies the relative polarity of glycerol and

Cycloheximide congeners produced by Streptomyces sp. SC0581 and photoinduced interconversion between (E)- and (Z)-2,3-dehydroanhydrocycloheximides

• Li Yang,
• Ping Wu,
• Jinghua Xue,
• Huitong Tan,
• Zheng Zhang and
• Xiaoyi Wei

Beilstein J. Org. Chem. 2017, 13, 1039–1049, doi:10.3762/bjoc.13.103

• fractions, showing the activity against P. infestans, were combined and subjected to silica gel column chromatography (CC) eluted with CHCl3/MeOH mixtures of increasing polarity (100:0 to 70:30) to give twenty fractions including two antifungal fractions, Fr. 1 (CHCl3/MeOH, 95:5) and Fr. 6 (CHCl3/MeOH, 90

A strategic approach to [6,6]-bicyclic lactones: application towards the CD fragment of DHβE

• Tue Heesgaard Jepsen,
• Emil Glibstrup,
• François Crestey,
• Anders A. Jensen and
• Jesper Langgaard Kristensen

Beilstein J. Org. Chem. 2017, 13, 988–994, doi:10.3762/bjoc.13.98

• carboxylic acid 25 in these apolar solvents was the reason. However, addition of small amounts of MeOH in order to increase polarity was detrimental and led to decomposition upon heating. Since the desired cyclization could be also approached as an intramolecular Michael addition we attempted to mediate the

Opportunities and challenges for the sustainable production of structurally complex diterpenoids in recombinant microbial systems

• Katarina Kemper,
• Max Hirte,
• Markus Reinbold,
• Monika Fuchs and
• Thomas Brück

Beilstein J. Org. Chem. 2017, 13, 845–854, doi:10.3762/bjoc.13.85

• , combinatorial enzyme design and microbial engineering. Mutational engineering of terpene synthases Site-directed mutagenesis of diterpene cyclases is conventionally applied to elucidate structure–function relationships and mostly targets the active site of the enzyme in order to change the polarity or dimension

Fluorinated cyclohexanes: Synthesis of amine building blocks of the all-cis 2,3,5,6-tetrafluorocyclohexylamine motif

• Tetiana Bykova,
• Nawaf Al-Maharik,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2017, 13, 728–733, doi:10.3762/bjoc.13.72

• the molecular dipole is 5.2 D [2]. The motif has the unique property of inducing facial polarity to the ring system [2][7]. The nature of the interaction of this ring system with protein targets remains to be examined, and its incorporation into organic materials is in its infancy. Access to this

• . However suitable crystals were obtained from acetone/acetonitrile for X-ray structure analysis. The X-ray structures of 13, 14 and 15 are illustrated in Figure 2. It was assumed that the facial polarity of the tetrafluorocyclohexane rings would be apparent in the molecular ordering in the solid state

Membrane properties of hydroxycholesterols related to the brain cholesterol metabolism

• Malte Hilsch,
• Ivan Haralampiev,
• Peter Müller,
• Daniel Huster and
• Holger A. Scheidt

Beilstein J. Org. Chem. 2017, 13, 720–727, doi:10.3762/bjoc.13.71

• estradiol was found in the lipid water interface of the membrane with an orientation perpendicular to the membrane normal. By that, the molecules act disturbing rather than ordering. Notably, MD simulations found an opposite effect of the hydroxycholesterols [21]. The additional polarity of

Interactions between photoacidic 3-hydroxynaphtho[1,2-b]quinolizinium and cucurbit[7]uril: Influence on acidity in the ground and excited state

• Jonas Becher,
• Daria V. Berdnikova,
• Darinka Dzubiel,
• Heiko Ihmels and
• Phil M. Pithan

Beilstein J. Org. Chem. 2017, 13, 203–212, doi:10.3762/bjoc.13.23

• ]. Notably, the chromophore of the oxyanion-substituted quinolizinium derivative 2cB resembles the well-established solvatochromic pyridinium-N-phenolate betaine dyes that are employed as polarity probes [53]. Correspondingly, the derivative 2cB shows a similar positive solvatochromism, i.e., a blue shift of

• the absorption maximum with increasing solvent polarity (CH3CN: 457 nm, MeOH: 432 nm, H2O: 415 nm). The prototropic equilibrium between 2 and 2cB is significantly shifted to the deprotonated form 2cB in the excited state, as commonly observed for hydroxy-substituted arenes. As a result, the pKa* of 2

Organofluorine chemistry: Difluoromethylene motifs spaced 1,3 to each other imparts facial polarity to a cyclohexane ring

• Mathew J. Jones,
• Ricardo Callejo,
• Alexandra M. Z. Slawin,
• Michael Bühl and
• David O'Hagan

Beilstein J. Org. Chem. 2016, 12, 2823–2827, doi:10.3762/bjoc.12.281

• also rendered fluorine containing compounds important in the development of organic materials such as liquid crystals [8][9]. Strategic fluorination can add polarity to a molecule, however, such compounds do not generally increase in their hydrophilic capacity, thus selective fluorination leads to

• distortion is also observed for the 1,3-diaxial C–F bonds in the solid state structures of 2 [20] and 3 [21] consistent with electrostatic dipolar repulsion between these C–F bonds and indicative of the origin of the polarity of these molecules. In terms of intermolecular packing in the solid state there are

• interaction of the positive non-fluorous face with the π-system of an aromatic ring by single crystal X-ray diffraction and NMR experiments. Additionally, the polarity of 4c has been calculated by computational optimisations. It follows that functionalised cyclohexanes containing the 1,3-di-CF2 motif would

Benzothiadiazole oligoene fatty acids: fluorescent dyes with large Stokes shifts

• Lukas J. Patalag and
• Daniel B. Werz

Beilstein J. Org. Chem. 2016, 12, 2739–2747, doi:10.3762/bjoc.12.270

• -dipyrromethene) [11][12], BOIMPY- (bis(borondifluoride)-8-imidazodipyrromethene) [13] and pyrene-labeled fatty acids [14]. Of course, all these alterations might also affect the membrane structure and its dynamics. While the NBD-fluorophore suffers from unsuitable polarity, a pyrene motif disrupts the unpolar

Electron-transfer-initiated benzoin- and Stetter-like reactions in packed-bed reactors for process intensification

• Anna Zaghi,
• Daniele Ragno,
• Graziano Di Carmine,
• Carmela De Risi,
• Olga Bortolini,
• Pier Paolo Giovannini,
• Giancarlo Fantin and
• Alessandro Massi

Beilstein J. Org. Chem. 2016, 12, 2719–2730, doi:10.3762/bjoc.12.268

• heterogeneous continuous-flow procedure for the polarity reversal of aromatic α-diketones is presented. Propaedeutic batch experiments have been initially performed to select the optimal supported base capable to initiate the two electron-transfer process from the carbamoyl anion of the N,N-dimethylformamide

• ). Keywords: C–C coupling; continuos-flow; diketone; electron-transfer; umpolung; Introduction The polarity reversal (umpolung) of carbonyl compounds by N-heterocyclic carbene (NHC) or cyanide catalysis represents a straightforward strategy for the synthesis of valuable molecules such as, among the many

A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring

• John Andraos

Beilstein J. Org. Chem. 2016, 12, 2420–2442, doi:10.3762/bjoc.12.236

• greenness. In research practice, synthetic organic chemists rely on a combination of retrosynthetic analysis [91][92][93][94][95][96][97], similarity and analogy patterning to known reactions, bond dissociation energy and bond polarity analysis (forward and umpolung), chemical intuition, and random

Methylenelactide: vinyl polymerization and spatial reactivity effects

• Judita Britner and
• Helmut Ritter

Beilstein J. Org. Chem. 2016, 12, 2378–2389, doi:10.3762/bjoc.12.232

•  1). Since the polymerization kinetics are mainly controlled by steric effects and the polarity of the double bonds, we evaluated the electronic structure of the different monomers via 1H nuclear magnetic resonance (NMR) spectroscopy. As expected, the double bond protons of MLA at 5.77 and 5.56 ppm

• MLA are Q = 0.79 and e = 0.015 (see Figure S16 for Q and e value calculation, Supporting Information File 1) [19]. The constant Q reflects the resonance stabilization of the growing radical. Large Q values (>0.5) indicate stabilized monomers. The constant e reflects the polarity of the double bond and

Solvent-free, visible-light photocatalytic alcohol oxidations applying an organic photocatalyst

• Martin Obst and
• Burkhard König

Beilstein J. Org. Chem. 2016, 12, 2358–2363, doi:10.3762/bjoc.12.229

• avoided, making the process more environmentally friendly and sustainable. Furthermore, quantitative yields can be achieved, avoiding work-up and laborious purification [2]. Moreover, solubility problems, like insolubility of one reactant or the different polarity of two reactants, are solved. Examples

A chiral analog of the bicyclic guanidine TBD: synthesis, structure and Brønsted base catalysis

• Mariano Goldberg,
• Denis Sartakov,
• Jan W. Bats,
• Michael Bolte and
• Michael W. Göbel

Beilstein J. Org. Chem. 2016, 12, 1870–1876, doi:10.3762/bjoc.12.176

• -phenylmaleimide (22) which finally turned out to be the most complex one (Table 1). The best but still low ee values for cycloadduct 25 were obtained in CHCl3 (37% ee) and CH2Cl2 (34% ee). Much better enantioselectivities of the Michael product 28 were found for reactions in solvents of increased polarity

One-pot synthesis of tetracyclic fused imidazo[1,2-a]pyridines via a three-component reaction

• Bo Yang,
• Chuanye Tao,
• Taofeng Shao,
• Jianxian Gong and
• Chao Che

Beilstein J. Org. Chem. 2016, 12, 1487–1492, doi:10.3762/bjoc.12.145

• % yield. Performing the reaction under reflux conditions slightly improved the yield to 11%. We next examined solvent effects in this MCR reaction and various solvents were screened, as summarized in Table 1. We observed that protic solvents with medium polarity can facilitate the reaction by product