Unexpected polymorphism during a catalyzed mechanochemical Knoevenagel condensation

• Sebastian Haferkamp,
• Andrea Paul,
• Adam A. L. Michalchuk and
• Franziska Emmerling

Beilstein J. Org. Chem. 2019, 15, 1141–1148, doi:10.3762/bjoc.15.110

• triclinic product. Inclusion of catalyst in the final product, as evidenced by mass spectrometric analysis, suggests this complex polymorphic pathway may be due to seeding effects. Multivariate analysis for the in situ Raman spectra supports this complex formation pathway, and offers a new approach to

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• chromoionophore and the spectra in Figure 1 were assigned to the formation of the trans-dye–Ba2+ complex [19]. For all dye solutions, a distinct isosbestic point upon titration was observed, indicating only one kind of complex formation even at the highest Ba2+ concentration. To determine the optimal Ba2

• , which is true for the simplest form of complexation [18]: where A0 and A∞ are the absorptions of the chromoionophore at zero and infinite concentration of the metal ion, respectively; A is the absorption at the concentration cM of the metal ion; K is the stability constant of complex formation, and L

• and LM are the ligand and the metal ion complex, respectively. A∞ and K were found by approximation of Equation 1. The stability constant for the complex formation was estimated to be K = 100 ± 15 M−1, 49.4 ± 7.6 M−1 and 44.7 ± 10 M−1 for dyes 4b, 4c and 4d, respectively. For dye 4a the stability

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• similar way to that described in Scheme 3. In this case, the coupled alkyne moiety is again activated by Cu(I) and then base-promoted cyclization occurs. A new copper complex formation with the alkene analogue to 13 (see Scheme 3) facilitates the aromatic nucleophilic substitution by indole or pyrrole

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

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

• salen-type ligand followed by metal-complex formation in the same pot [55]. Otera’s solvent-free approach by which the formation of self-assembled supramolecules could be accelerated [56]. Synthesis of a Pd-based metalla-supramolecular assembly through mechanochemical activation for C–H-bond activation

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

• near various carbon atoms in the main polymer chain. Apart from this, the intensity of the bending vibrations of carboxyl groups at 1700 cm−1 and of ether groups at 1030–1080 cm−1 increases as well. Results and Discussion Study of the complex formation between Cp2TiCl2 and AlEt2Cl It is known that the

• only at Ti/Al ratios above 1:1, therefore, the ratio of Ti/Al equal to 1:1.5 was further used. During this complex formation, generation of cyclopentadiene (CPD) trimers, resulting from the interaction between the cyclopentadiene ring of bis(cyclopentadienyl)titanium dichloride and dicyclopentadiene

Fabrication of supramolecular cyclodextrin–fullerene nonwovens by electrospinning

• Hiroaki Yoshida,
• Ken Kikuta and
• Toshiyuki Kida

Beilstein J. Org. Chem. 2019, 15, 89–95, doi:10.3762/bjoc.15.10

• form γ-CD–C60 complexes. Our electrospinning system employs a highly volatile solvent, HFIP. We initially examined γ-CD–C60 complex formation in HFIP. C60 (16 mg/mL, pre-ground by an agate mortar) was added into 15 w/v % γ-CD/HFIP and kept under sonication for a few days. After removing the residual

• –36 h (Figure 2b and Figure S1 in Supporting Information File 1). Although complex formation occurs without sonication, the color of the obtained solution was fairly weak (data not shown). Shortening of the time to reach equilibrium in the γ-CD–C60 inclusion complex formation was reported by

Protein–protein interactions in bacteria: a promising and challenging avenue towards the discovery of new antibiotics

• Laura Carro

Beilstein J. Org. Chem. 2018, 14, 2881–2896, doi:10.3762/bjoc.14.267

• to interact with the crucial residues in the basic ridge which are known to be essential for the in vitro complex formation of ExoI with SSB [73], a finding that supports the low IC50 value exhibited by this molecule. Remarkably, these four compounds were also able to disrupt the complex formation of

Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

• Hendrik V. Schröder and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190

• complexes π-electron-rich aromatic compounds such as dihydroxynaphthalenes or dihydroxybenzenes. The π-donor TTF (1) also forms a 1:1 complex 13 with this host molecule as shown in solution experiments and by crystallography. The complex formation is immediately visible by an emergent green color of these

Chiral bisoxazoline ligands designed to stabilize bimetallic complexes

• Deepankar Das,
• Rudrajit Mal,
• Nisha Mittal,
• Zhengbo Zhu,
• Thomas J. Emge and
• Daniel Seidel

Beilstein J. Org. Chem. 2018, 14, 2002–2011, doi:10.3762/bjoc.14.175

• linkers. In addition, each amide moiety, upon deprotonation (a requirement for complex formation), would provide a formal negative charge on the ligand, thus resulting in increased complex stability while reducing the number of spectator anions associated with the two metals. Different combinations of

• ligand with three nitrogen donor atoms per metal center. Ligand 16-H2 was found to undergo complex formation with various copper, zinc, palladium and nickel salts. Figure 3 shows the X-ray crystal structure of 16·Ni2(OAc)2, obtained from ligand 16-H2 and two equivalents of nickel(ΙΙ) acetate. The

• obtained, preliminary experiments have shown that ligand 22-H2 undergoes complex formation with various nickel and palladium salts [58]. Pyrazole-bridged bisoxazoline ligands. The synthesis of an analog of bisoxazoline ligand 16-H2 in which the naphthyridine bridge is replaced with a pyrazole linker is

Synthesis of new p-tert-butylcalix[4]arene-based polyammonium triazolyl amphiphiles and their binding with nucleoside phosphates

• Vladimir A. Burilov,
• Guzaliya A. Fatikhova,
• Mariya N. Dokuchaeva,
• Ramil I. Nugmanov,
• Diana A. Mironova,
• Pavel V. Dorovatovskii,
• Victor N. Khrustalev,
• Svetlana E. Solovieva and
• Igor S. Antipin

Beilstein J. Org. Chem. 2018, 14, 1980–1993, doi:10.3762/bjoc.14.173

• complex formation was calculated as a difference between free energy of calix[4]arene + ADP/ATP complex and isolated calix[4]arene and ADP/ATP dianion. The complex structures corresponding to the minimum energy as well as supramolecular binding motif of ADP and ATP are presented in Figure 4. As can be

Rational design of boron-dipyrromethene (BODIPY) reporter dyes for cucurbit[7]uril

• Mohammad A. Alnajjar,
• Jürgen Bartelmeß,
• Robert Hein,
• Pichandi Ashokkumar,
• Mohamed Nilam,
• Werner M. Nau,
• Knut Rurack and
• Andreas Hennig

Beilstein J. Org. Chem. 2018, 14, 1961–1971, doi:10.3762/bjoc.14.171

• -dipyrromethene (BODIPY) dyes as a new class of fluorophores for the design of reporter dyes for supramolecular host–guest complex formation with cucurbit[7]uril (CB7). The BODIPYs contain a protonatable aniline nitrogen in the meso-position of the BODIPY chromophore, which was functionalized with known binding

• too slow to equilibrate during the titration within reasonable time (Figure S19, Supporting Information File 1). The pKa values of the host–dye complex were independently determined by pH titrations in presence of excess CB7 and analysed assuming quantitative complex formation (Figure 4). Overall, the

• complex formation of the BODIPY core, the photostability of the dyes was not affected by CB7 complex formation (Figure S20, Supporting Information File 1). The compatibility of BODIPYs with common excitation sources and filter sets also enables their use in fluorescence microscopy. To demonstrate, we have

An amphiphilic pseudo[1]catenane: neutral guest-induced clouding point change

• Tomoki Ogoshi,
• Tomohiro Akutsu and
• Tada-aki Yamagishi

Beilstein J. Org. Chem. 2018, 14, 1937–1943, doi:10.3762/bjoc.14.167

• other pillar[5]arenes [17][20], and were assigned as the proton signals from the methylene protons of the 1,4-dicyanobutane in the cavity of pillar[5]arene 3. The complex formation of 3 and 1,4-dicyanobutane indicates the displacement of the alkyl chain ring from the inside to the outside of the cavity

DFT calculations on the mechanism of copper-catalysed tandem arylation–cyclisation reactions of alkynes and diaryliodonium salts

• Tamás Károly Stenczel,
• Ádám Sinai,
• Zoltán Novák and
• András Stirling

Beilstein J. Org. Chem. 2018, 14, 1743–1749, doi:10.3762/bjoc.14.148

• preferred to the one where the oxazoline ring formation occurs first (the barriers of the ring closure are consistently higher than those of the aryl transfers). It is also interesting to note that in some cases the initial complex formation is the rate determining step along the aryl-transfer path although

• in most cases the differences in the two barrier heights are very small. The full set of reactions also shows that the aryl transfer as the first step after the complex formation with the catalyst is preferred over the route where the ring closure precedes the aryl transfer. Only three cases from the

A conformationally adaptive macrocycle: conformational complexity and host–guest chemistry of zorb[4]arene

• Liu-Pan Yang,
• Song-Bo Lu,
• Arto Valkonen,
• Fangfang Pan,
• Kari Rissanen and
• Wei Jiang

Beilstein J. Org. Chem. 2018, 14, 1570–1577, doi:10.3762/bjoc.14.134

• in plots of ΔH versus temperature from 283 to 313 K (Figure 5). The release of solvent molecules upon complex formation may account for the negative heat capacity change and similar heat capacity changes were also reported for the fullerenes recognition [40]. Meanwhile, the changes of ΔG for the

Oligonucleotide analogues with cationic backbone linkages

• Melissa Meng and
• Christian Ducho

Beilstein J. Org. Chem. 2018, 14, 1293–1308, doi:10.3762/bjoc.14.111

• of a mixture of 18 with DNA-APoly in thermal melting studies, as compared to the non-hybridized, single-stranded oligonucleotides [41]. This indicated a successful complex formation with ordered base stacking of the positively charged oligonucleotide analogue and its native DNA counterstrand. When

• -pairing fidelity of the pentameric thymidinyl DNmt. No increase in hyperchromicity was observed for combinations of DNmt-T5 with either DNA-GPoly, DNA-CPoly or DNA-TPoly, over a temperature range from 5 to 93 °C, thus ruling out complex formation with these fully mismatched native DNA counterstrands

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

• ). This has been attributed to strong self-association (dimerization) in an antiparallel, head-to-tail orientation in aqueous solution during complex formation with duplex DNA oligomers verified via NOE experiments [61]. They further reported several structurally diverse MGBs, derived from distamycin, in

• . designed novel polyamides, which were able to bind adjacent to the recognition sites of a broad-range of transcription factors TBP, Ets-1, LEF-1 and NF-κB [69], thereby inhibiting binding of these transcription factors to DNA and ternary complex formation [70]. Dervan et al. has further introduced a novel

•  10. Minor groove complex formation between DNA duplex and Hoechst 33258 is shown in Figure 7b [82]. X-ray crystallographic and NMR studies confirmed that Hoechst 33258 binds to the A·T-rich sequences in minor groove with the planar benzimidazole groups are oriented parallel to the direction of the

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• : specifically, solid solutions, cocrystals, polymorph transitions, carbon nanotube dissolution and inclusion complex formation. Keywords: DNA; green chemistry; mechanochemistry; nucleoside; nucleotide; Introduction Several definitions of mechanochemistry have been attempted since Ostwald included it as one of

• using mechanochemistry [94] and Rajamohan and co-workers described using a mortar and pestle to effect LAG of β-cyclodextrin with either inosine [95] or cytidine [96] in the presence of water. Weak complex formation was inferred by powder XRD for cytidine. Conclusion Access to reliable and reproducible

Crystal structure of the inclusion complex of cholesterol in β-cyclodextrin and molecular dynamics studies

• Elias Christoforides,
• Andreas Papaioannou and
• Kostas Bethanis

Beilstein J. Org. Chem. 2018, 14, 838–848, doi:10.3762/bjoc.14.69

• of cholesterol and the secondary rim protons of β-CD were indicated by NMR concluding to a probable 2:1 host/guest inclusion formation [26]; the formation of 1:1 stoichiometric complexes pointed out by phase solubility [25] or MD studies [29]; favorable inclusion complex formation with β-CD dimer was

Phosphodiester models for cleavage of nucleic acids

• Satu Mikkola,
• Tuomas Lönnberg and
• Harri Lönnberg

Beilstein J. Org. Chem. 2018, 14, 803–837, doi:10.3762/bjoc.14.68

Polarization spectroscopy methods in the determination of interactions of small molecules with nucleic acids – tutorial

• Tamara Šmidlehner,
• Ivo Piantanida and
• Gennaro Pescitelli

Beilstein J. Org. Chem. 2018, 14, 84–105, doi:10.3762/bjoc.14.5

• approach as it monitors changes of only one species involved in the complex formation and thus the interpretation of results is simple and straightforward. However, to design the polarization spectroscopy experiment accurately, it is essential that solutions of both the polynucleotide and the ligand are

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

Binding abilities of polyaminocyclodextrins: polarimetric investigations and biological assays

• Marco Russo,
• Daniele La Corte,
• Annalisa Pisciotta,
• Serena Riela,
• Rosa Alduina and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2017, 13, 2751–2763, doi:10.3762/bjoc.13.271

• consequent unfavourable effect on the complex formation entropy [43][50]. A further unfavourable contribution may also come from the increasingly difficult desolvation of the charged host. These combined effects cause the observed decrease of K values for the neutral guest 1. By contrast, for the anionic

Binding abilities of a chiral calix[4]resorcinarene: a polarimetric investigation on a complex case of study

• Marco Russo and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2017, 13, 2698–2709, doi:10.3762/bjoc.13.268

• [41][42][43][44][45], this indicates the occurrence of severer and severer dynamic-conformational changes upon complex formation. Therefore, we can conclude that the overall bell-shaped trend for K1 values on passing from CAP−1 to CAP−4 is the outcome of a fine interplay between favourable

• complex formation. Interestingly, a fair upfield shift is observed also for the signals at 0.82 and 1.14 ppm (passing to 0.71 and 1.03 ppm, respectively) relevant to the propyl pendant groups linked at the 2, 8, 14 and 20 positions of the calixarene scaffold. Assuming for CAP the occurrence of an “all

• occurring in host–guest complex formation processes involving calixarenes in general. This can be particularly useful, even because CAP and structurally related ligands might find various interesting applications, due to their amphiphilic character, chirality and coordination ability towards metal cations

Metal-mediated base pairs in parallel-stranded DNA

• Jens Müller

Beilstein J. Org. Chem. 2017, 13, 2671–2681, doi:10.3762/bjoc.13.265

• glycosidic bonds, parallel-stranded duplexes have been investigated. In many cases, such as the well-established cytosine–Ag(I)–cytosine base pair, metal complex formation is more stabilizing in parallel-stranded DNA than in antiparallel-stranded DNA. This review presents an overview of all metal-mediated

Structural diversity in the host–guest complexes of the antifolate pemetrexed with native cyclodextrins: gas phase, solution and solid state studies

• Magdalena Ceborska,
• Magdalena Zimnicka,
• Aneta Aniela Kowalska,
• Kajetan Dąbrowa and
• Barbara Repeć

Beilstein J. Org. Chem. 2017, 13, 2252–2263, doi:10.3762/bjoc.13.222

• methods – FTIR–ATR and Raman were used for describing the way of PTX-CD interactions. The IR spectroscopy in the region characteristic for δ-HOH bending of water molecules attached to CDs (1600–1700 cm−1) is usually employed for tracking of the inclusion complex formation, however, Raman spectra of this

• identification of guest–host interactions is possible [17][18]. Any changes in the band position as well as increasing or decreasing of its intensity indicate complex formation. In that sense Raman spectroscopy emerges as an important technique for studying host–guest interactions, in particular for verifying if

• affinity toward PTX (Ka = 4 M−1). Findings from FTIR–ATR and Raman experiments demonstrate that the region of C=C bond vibrations of the guest is an excellent indicator of complex formation. The observed changes in this band (position and intensity), together with the information about possible appearance