Synthesis and late stage modifications of Cyl derivatives

• Phil Servatius and
• Uli Kazmaier

Beilstein J. Org. Chem. 2022, 18, 174–181, doi:10.3762/bjoc.18.19

• , entry 1). Since the reaction seemed to stop after 30–40% conversion, it was speculated that the ester enolate chelate complex formation was incomplete due to consumption of the base. For instance, deprotonation of tyrosine residues in benzyl position has been observed previously in the derivatization of

1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

• Ruan Carlos B. Ribeiro,
• Patricia G. Ferreira,
• Amanda de A. Borges,
• Luana da S. M. Forezi,
• Fernando de Carvalho da Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 53–69, doi:10.3762/bjoc.18.5

• the presence of CuCl2 formed two isomers of 4-arylated-N-butylbenzo[c]carbazole-5,6-dione 60 and 4-amino-benzo[a]carbazol-5,6-dione 61 in 39% and 13% yields, respectively. These two reactions demonstrate the importance of the catalyst in complex formation with carbonyls of 18 that promote nucleophilic

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• derivative 127. The plausible mechanism for the formation of compound 127 proceeded consecutively with π-complex formation, Friedel–Crafts type addition, deprotonation, and finally protonation of alcohol for the elimination of water to get the final product [92]. A Hg(OTf)2-mediated cyclization was utilized

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• of N-heterocyclic compounds. In 2017, Wu and colleagues [58] uncovered the use of the bis(sulfur dioxide) adduct of DABCO, 1,4-diazabicyclo[2.2.2]octane·(SO2)2, as sulfone source in the EDA complex formation by 4-methyl-1-(p-tolyl)pentan-1-one O-(2,4-dinitrophenyl)oxime (11) towards the

• tetramethylethylenediamine (TMEDA) as additive in the EDA complex formation with perfluoroalkyl iodides 42 to afford 2-perfluoroalkylbenzothiazole products 43, employing blue LEDs (25 W) as irradiation source (Scheme 14). Notably, as (2-isocyanophenyl)(methyl)selane was exploited instead of substrate 41, new

• ; however, the presence of electron-donating substituents lowered the reactivity due to a negative impact on the EDA complex formation and led to a low yield. It is worth noting that the phase-transfer catalyst employed in this experiment is a suitable donor for the photosensitive EDA complex while at the

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

• IDPs upon tertiary and quaternary complex formation [79]. The Myc-Max heterodimer is a well-known oncogenic transcription factor complex able to bind to enhancer box (E-box) regions (5’-CACGTG-3’) of DNA with low-nanomolar affinity, what triggers its biological function as a transcriptional regulator

• tagging and PRE NMR spectroscopy to probe and trace the conformational changes experienced by disordered Myc upon Myc‐Max heterodimerization. Going beyond, they also employed 19F NMR to interrogate the changes induced in the Myc-Max heterodimer structure upon full quaternary complex formation in the

Molecular basis for protein–protein interactions

• Brandon Charles Seychell and
• Tobias Beck

Beilstein J. Org. Chem. 2021, 17, 1–10, doi:10.3762/bjoc.17.1

• knowledge of protein–protein interactions, common characterisation methods to characterise them, and their role in protein complex formation with some examples. A deep understanding of protein–protein interactions and their molecular interactions is important for a number of applications, including drug

• –protein complex formation. Finally, we will give a brief account of some examples for higher-order protein complexes and the PPIs involved. Review Characterisation methods for PPIs Particular PPIs can be relatively difficult to study since in vivo, any particular protein is present amongst a plethora of

• . Separately, the proteins that compose the complex are dyed, digested, and detected. The fragments that are detected in the painted complex but not detected in the painted protein monomers are the regions that were solvent accessible in the monomers but became inaccessible due to the complex formation, i.e

Synthesis and investigation of quadruplex-DNA-binding, 9-O-substituted berberine derivatives

• Jonas Becher,
• Daria V. Berdnikova,
• Heiko Ihmels and
• Christopher Stremmel

Beilstein J. Org. Chem. 2020, 16, 2795–2806, doi:10.3762/bjoc.16.230

• . Additional information about the complex formation between the ligands and the quadruplex DNA forms 22AG and a2 was provided by CD spectroscopy. The changes of the CD spectrum of 22AG upon the addition of derivatives 4a–e clearly indicate a shift of the equilibrium between the different quadruplex forms of

Optical detection of di- and triphosphate anions with mixed monolayer-protected gold nanoparticles containing zinc(II)–dipicolylamine complexes

• Lena Reinke,
• Julia Bartl,
• Marcus Koch and
• Stefan Kubik

Beilstein J. Org. Chem. 2020, 16, 2687–2700, doi:10.3762/bjoc.16.219

• ) and treating the solution with 50 equiv of zinc(II) nitrate per estimated number of DPA groups. An 1H NMR spectrum of the mixture was recorded after 30 min to confirm that complex formation had occurred and was complete. The solution was then evaporated and the nanoparticles redissolved in water

Thermodynamic and electrochemical study of tailor-made crown ethers for redox-switchable (pseudo)rotaxanes

• Henrik Hupatz,
• Marius Gaedke,
• Hendrik V. Schröder,
• Julia Beerhues,
• Arto Valkonen,
• Fabian Klautzsch,
• Sebastian Müller,
• Felix Witte,
• Kari Rissanen,
• Biprajit Sarkar and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2020, 16, 2576–2588, doi:10.3762/bjoc.16.209

• between the catechol ring of the crown ether and aromatic moieties of the secondary ammonium ion contribute to the complex formation [22][23][24][25]. Over the last 25 years, a detailed understanding of the thermodynamic and kinetic properties of crown ether/ammonium complexes has developed enabling the

• hand, additional π–π-interactions of the phenyl ring in A1·PF6 to the crown ether aromatic rings favor the complex formation. On the other hand, the flexibility of the alkyl substituent in A2·PF6 is diminished upon complexation, inducing a larger entropic penalty visible in the overall more negative

Hierarchically assembled helicates as reaction platform – from stoichiometric Diels–Alder reactions to enamine catalysis

• David Van Craen,
• Jenny Begall,
• Johannes Großkurth,
• Leonard Himmel,
• Oliver Linnenberg,
• Elisabeth Isaak and
• Markus Albrecht

Beilstein J. Org. Chem. 2020, 16, 2338–2345, doi:10.3762/bjoc.16.195

• ][17][18][19][20]. Enantioselectivities up to 25% ee at elevated temperature (32% ee at 0 °C) depending on the substrate were achieved in a Diels–Alder reaction by introducing two different substituted catechol ester ligands during the complex formation: (1) A diene-substituted ligand 1-H2 for the

Naphthalene diimide–amino acid conjugates as novel fluorimetric and CD probes for differentiation between ds-DNA and ds-RNA

• Annike Weißenstein,
• Myroslav O. Vysotsky,
• Ivo Piantanida and
• Frank Würthner

Beilstein J. Org. Chem. 2020, 16, 2032–2045, doi:10.3762/bjoc.16.170

• -induced emission quenching of acridine or 4,9-diazapyrene derivatives [43]. In order to confirm the fluorimetric data by an independent method, and also to characterise thermodynamic parameters of complex formation, ITC titrations were performed (Figure 6, Supporting Information File 1, Figures S28–S30

[3 + 2] Cycloaddition with photogenerated azomethine ylides in β-cyclodextrin

• Margareta Sohora,
• Leo Mandić and
• Nikola Basarić

Beilstein J. Org. Chem. 2020, 16, 1296–1304, doi:10.3762/bjoc.16.110

• , which changed from singlet to a multiplet (Figure S4 in Supporting Information File 1). Nonlinear regression analysis of the chemical shifts to the β-CD concentration did not provide a good quality of the fit to the model involving 1:1 complex formation (Figure S5 in Supporting Information File 1

• accordance with the formation of a ternary complex AN@2@β-CD (Scheme 2). However, they may also indicate that excess of AN added to the solution competitively binds to β-CD forming a complex AN@β-CD and inducing dissociation of the 2@β-CD. If we assume a model for the complex formation in the stoichiometry 1

• upfield shifts. Although the changes were small, we tried to process them using nonlinear regression analysis and model for the complex formation with 1:1:1 stoichiometry. The fit was of poor quality, but it provided an estimation of the constant with the value of K2 = 0–7 M−1 (Figure S9 in Supporting

Anion-driven encapsulation of cationic guests inside pyridine[4]arene dimers

• Anniina Kiesilä,
• Jani O. Moilanen,
• Anneli Kruve,
• Christoph A. Schalley,
• Perdita Barran and
• Elina Kalenius

Beilstein J. Org. Chem. 2019, 15, 2486–2492, doi:10.3762/bjoc.15.241

• capsules were originally assumed to encapsulate anionic guests inside their cavity due to the π-acidic character of the aromatic walls [7][8]. Mattey et al. detected 1:1 complex formation with PF6− and BF4− by mass spectrometry, however, without ion mobility mass spectrometry, the location of the anion

• the π-acidic character of pyridine rings, such as 2-oxo-6-oxypyridine, is rather weak [9][10]. Thus, pyridine[4]arenes may be expected to show a dual binding behavior towards anions and cations [8]. In addition to anion complexes also 2:1 complex formation with neutral carboxylic acids and amides have

• studies with ESI-Q-TOF mass spectrometry. Complex formation was tested with the following series of cationic guests: MeNH3+, Me2NH2+, Me3NH+, Me4N+, EtNH3+, Et2NH2+, Et4N+ and Pr4N+, which were used as the corresponding Cl− or Br− salts. None of the cations MeNH3+, Me2NH2+, Me3NH+, EtNH3+, Et2NH2+ or Pr4N

1,2,3-Triazolium macrocycles in supramolecular chemistry

• Mastaneh Safarnejad Shad,
• Pulikkal Veettil Santhini and
• Wim Dehaen

Beilstein J. Org. Chem. 2019, 15, 2142–2155, doi:10.3762/bjoc.15.211

• synthesized the novel tetra-1,2,3-triazolium zinc porphyrin cage 3 (Figure 4) and have probed its characteristics by using UV–visible spectroscopy, determining the association constants for complex formation in 5% water/acetone. This receptor has shown affinity toward all of the halide ions and especially

• chemistry. Different hydrogen bond donors such as pyrrole N–H and benzene C–H along with the triazolium C5–H have been successfully incorporated within a single macrocyclic framework. The complex formation of anions with the hydrogen bond donors varied according to the polarity of the solvent. It was found

Complexation of chiral amines by resorcin[4]arene sulfonic acids in polar media – circular dichroism and diffusion studies of chirality transfer and solvent dependence

• Bartosz Setner and
• Agnieszka Szumna

Beilstein J. Org. Chem. 2019, 15, 1913–1924, doi:10.3762/bjoc.15.187

• chiral multidentate amino compounds (Figure 1) in polar media (DMSO, methanol, aqueous media). RSA 1 features a hydrophobic cavity and a polar rim of sulfonic acid groups capable of forming electrostatic interactions. We will put a particular emphasis on ordering during complex formation that is

• quantitative. The kinetics of complex formation is fast on the NMR timescale. The complexes exhibit a high degree of ordering that is manifested by chirality transfer observed by diastereotopic splitting (Figure 6c, inset). In this case CD spectra are not diagnostic (CD bands are observed already for chiral

• disintegrates and the observed D is a result of a dynamic exchange between the complex 1(R)-2 with free components 1 and (R)-2. The addition of an extra portion of 1 to 1(R)-2 shifts the chemical equilibrium towards complex formation. Thus, in the mixture [1 + 1(R)-2]DMSO the component (R)-2 is fully consumed

Tautomerism as primary signaling mechanism in metal sensing: the case of amide group

• Vera Deneva,
• Georgi Dobrikov,
• Aurelien Crochet,
• Daniela Nedeltcheva,
• Katharina M. Fromm and
• Liudmil Antonov

Beilstein J. Org. Chem. 2019, 15, 1898–1906, doi:10.3762/bjoc.15.185

• intramolecular hydrogen bonding with the ionophore [7][8] is shown in Scheme 1. The complex formation ejects the tautomeric proton and stabilizes the keto tautomer. Several successful tautomeric ligands, based on 4-(phenyldiazenyl)naphthalen-1-ol (1) [8] (2 and 3, Scheme 2) as a tautomeric unit have been

• bonding between the tautomeric OH group and the carbonyl group in the ionophore part. The complex formation, depending on the size and charge of the metal ion, should shift the tautomeric equilibrium towards the keto tautomer and should provide stabilization of the complex. To the best of our knowledge

• complex and the deprotonated ligand, shown in Figure 4, indicates that the complex formation is not related to deprotonation. These results coincide with the results obtained for compound 3 [15]. The complexation abilities of 6 towards some alkaline-earth metal ions were studied and the obtained spectra

Halide metathesis in overdrive: mechanochemical synthesis of a heterometallic group 1 allyl complex

• Ross F. Koby,
• Nicholas R. Rightmire,
• Nathan D. Schley,
• Timothy P. Hanusa and
• William W. Brennessel

Beilstein J. Org. Chem. 2019, 15, 1856–1863, doi:10.3762/bjoc.15.181

• interactions, evidently help to drive the heterometallic complex formation. Conclusion Formally, halide metathesis as a synthetic technique depends strongly on the relative thermodynamic stabilities of the starting and final metal halide salts, M'X and MX. Practically, however, the reaction solvent is also a

Synthesis of a [6]rotaxane with singly threaded γ-cyclodextrins as a single stereoisomer

• Jason Yin Hei Man and
• Ho Yu Au-Yeung

Beilstein J. Org. Chem. 2019, 15, 1829–1837, doi:10.3762/bjoc.15.177

• further interlocking at the γ-CD. Results and Discussion Building block design and rotaxane synthesis To encourage complex formation with γ-CD, axle 1 was designed with a biphenylene core to bind to the macrocycle through hydrophobic effect. The axle is terminated by 2-aminoethyl azide for CB[6]-mediated

Water inside β-cyclodextrin cavity: amount, stability and mechanism of binding

• Stiliyana Pereva,
• Valya Nikolova,
• Silvia Angelova,
• Tony Spassov and
• Todor Dudev

Beilstein J. Org. Chem. 2019, 15, 1592–1600, doi:10.3762/bjoc.15.163

• structures possessing less elaborate hydrogen bond networks (compare ΔH1/ΔH78 for reaction 2 with those of reactions 1 and 3 in Table 1). Generally, increasing the polarity of the medium (higher dielectric constant) attenuates the energies of complex formation although the enthalpies remain negative. Adding

• , observed earlier for α-CD hydration, hold for β-CD as well: the hot spot of the host molecule with the highest affinity for water molecule(s) is the narrow rim. Interestingly, the α-CD–H2O and β-CD–H2O complex formation is characterized by very close ΔH78 values (−2.6 and −2.8 kcal mol−1, respectively

• complex formation, ∆Hε, in condensed medium (water, Equation 2): Basis set superposition errors (BSSE) were considered by following the counterpoise approach of Boys and Bernardi as implemented in Gaussian 09 package. The PyMOL software was used for creating the molecular graphics images [24]. M062X/6-31G

A heteroditopic macrocycle as organocatalytic nanoreactor for pyrroloacridinone synthesis in water

• Piyali Sarkar,
• Sayan Sarkar and
• Pradyut Ghosh

Beilstein J. Org. Chem. 2019, 15, 1505–1514, doi:10.3762/bjoc.15.152

• supramolecular assemblies like molecular rotors (pseudorotaxane, rotaxane, catenane), molecular switches, molecular shuttles, etc. [32][33][34][35][36][37][38][39][40][41][42][43]. Furthermore, macrocycles have been applied in the area of ion–ion pair recognition and heterometallic complex formation [44][45][46

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

• oxygen of the P=O group. The comparison of 1H, 13C, and 31P NMR spectra of starting 1a and its complex with AlCl3 13 is presented in Figure 3 (see full spectral data in Supporting Information File 1). It is clear that the complex formation led to significant broadening of NMR spectral lines and, mainly

Reaction of oxiranes with cyclodextrins under high-energy ball-milling conditions

• László Jicsinszky,
• Federica Calsolaro,
• Katia Martina,
• Fabio Bucciol,
• Maela Manzoli and
• Giancarlo Cravotto

Beilstein J. Org. Chem. 2019, 15, 1448–1459, doi:10.3762/bjoc.15.145

• especially useful when the crystalline complex formation with the guest is undesirable. The aggregation properties, by the ready-to-associate secondary rim, are considerably affected by these substituents. One of the most important reactions of CDs occurs with oxiranes (epoxides) under basic conditions to

• seen in Figure 2 and Figure 3. Although scaled-up β-CDP has somehow larger particles, complexation studies with methyl orange (MO) only showed small differences. Although complex formation with MO showed similar behaviour to previous reports [13], adsorption capacity seems to be considerably lower than

Host–guest interactions between p-sulfonatocalix[4]arene and p-sulfonatothiacalix[4]arene and group IA, IIA and f-block metal cations: a DFT/SMD study

• Valya K. Nikolova,
• Cristina V. Kirkova,
• Silvia E. Angelova and
• Todor M. Dudev

Beilstein J. Org. Chem. 2019, 15, 1321–1330, doi:10.3762/bjoc.15.131

• between biological receptors and small ions. The complex formation behavior of water-soluble p-sulfonatocalix[4]arene and thiacalix[4]arene and group IA, IIA and f-block metal cations has been investigated computationally by means of density functional theory computations in the gas phase and in aqueous

• environment. The calculated Gibbs free energy values of the complex formation reaction of these ligands with the bare metal cations suggest a spontaneous and energy-favorable process for all metal cations in the gas phase and only for Na+, Mg2+, Lu3+ cations in water environment. For one of the studied

• formation reactions. Keywords: complex formation; DFT; group IA; IIA and f-block metal cations; macrocycles; p-sulfonatocalix[4]arene; p-sulfonatothiacalix[4]arene; Introduction If macrocycles are pillars of the supramolecular chemistry, then calixarenes (“calix” = vase + “arene”) are the 3rd pillar after

Design of a double-decker coordination cage revisited to make new cages and exemplify ligand isomerism

• Sagarika Samantray,
• Sreenivasulu Bandi and
• Dillip K. Chand

Beilstein J. Org. Chem. 2019, 15, 1129–1140, doi:10.3762/bjoc.15.109

• with the ligand L1 at two different metal-to-ligand ratios (1:1 and 3:2). We also carried out the complexation of bare palladium(II) with the ligand L1 at two different metal-to-ligand ratios (1:2 and 3:4). The complexation reactions performed in DMSO-d6 allowed the monitoring of complex formation and

• to form (e.g., from 4a and L1) and prone to decomposition. As far as trinuclear complex formation is concerned the central pyridine ring of L1 is in a relatively favorable situation, thus the complex 4a could form and 3a was a kinetic product. Conclusion A set of mononuclear and trinuclear complexes