Controlling the stereochemistry in 2-oxo-aldehyde-derived Ugi adducts through the cinchona alkaloid-promoted electrophilic fluorination

• Yuqing Wang,
• Gaigai Wang,
• Anatoly A. Peshkov,
• Ruwei Yao,
• Muhammad Hasan,
• Manzoor Zaman,
• Chao Liu,
• Stepan Kashtanov,
• Olga P. Pereshivko and
• Vsevolod A. Peshkov

Beilstein J. Org. Chem. 2020, 16, 1963–1973, doi:10.3762/bjoc.16.163

• -triggered complexation with boron trifluoride diethyl etherate. The resulting O,O-chelated boron complexes 11 turned out to be strong solid-state emitters featuring clear aggregation-induced emission (AIE) characteristics [61]. Encouraged by these results, we decided to attempt the reaction of 2-oxo

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

• enough to react due to it complexation by BF3·OEt2. To understand in more detail the competitive formation of linear versus cyclic products in the reaction, methanol was explored as the nucleophile instead of bromide ion (Scheme 3). The reaction (43 h, 20 °C) realized in MeOH as a solvent and in the

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

• “cyanostar” macrocycle [15][16]. Although not a macrocycle, a successful binding motif that is noteworthy for its ability to bind carboxylates in polar environments, is the guanidiniocarbonylpyrrole (GCP) moiety designed by Carsten Schmuck and Michael Schwegmann [17]. The transition from complexation studies

• . Conclusion To construct a functional chemical sensor, extensive interdisciplinary effort is required. A variety of problems must be addressed in several development stages, all of which were attended to in this work. The conceptual design of macrocyclic anion receptors led to in silico complexation studies

• of biscarbazolylurea-type ionophores. Eleven novel methylene-bridged macrocyclic receptor molecules were synthesized and characterized alongside a similar open-chain receptor and two additional macrocycles. Experimental complexation studies with different carboxylates were carried out in two

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• are poor substrates for the PKR as they are deactivated in the cobalt-complexation step, and the highest yields are usually obtained with terminal alkynes. The scenario is similar in the case of fluorinated substrates, with the intramolecular version being much more developed than the intermolecular

• and co-workers [73] allowed the efficient preparation of a small library of substrates bearing aryl, alkyl, and alkenyl substitutents. These were isolated after complexation to Co2(CO)8 as the corresponding adducts 64, due to difficulties in their isolation. Subsequent heating with norbornadiene

Models of necessity

• Timothy Clark and
• Martin G. Hicks

Beilstein J. Org. Chem. 2020, 16, 1649–1661, doi:10.3762/bjoc.16.137

• reactions. There is, however, a need to add non-covalent interactions to the model in order to take the importance of complexation and aggregation via non-covalent interactions into account. This could be done in a purely ad hoc fashion for each type of interaction. This is how force-field developers have

Synthesis of new fluorescent molecules having an aggregation-induced emission property derived from 4-fluoroisoxazoles

• Kazuyuki Sato,
• Akira Kawasaki,
• Yukiko Karuo,
• Atsushi Tarui,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2020, 16, 1411–1417, doi:10.3762/bjoc.16.117

• ]. Consequently, we examined several conditions for the ring opening of fluorinated isoxazoles 3, and found that using Mo(CO)6 gave the corresponding α-fluorinated enaminoketones 8 in moderate yields (Scheme 6). With the enaminoketones 8 at hand, the subsequent boron complexation with BF3·Et2O in the presence of

• 8 and their conversion to BKIs (yields refer to isolated yields; aboron complexation of 8a to 9a was not attempted). Attempted selective fluorination of BKI 6b. Ring-opening reaction of 4-fluoroisoxazoles 3 and their conversion into F-BKIs 9 (yields refer to isolated yields). UV–vis absorption and

[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

• of the phthalimide, which changed from a singlet to a multiplet (Figure S1 in Supporting Information File 1). The spectral changes are in accordance with the formation of an inclusion complex 2@β-CD, with the dynamics for the complexation faster than the NMR time-scale (millisecond). Nonlinear

• regression analysis of the chemical shifts depending on the β-CD concentration, to a complexation model with 1:1 stoichiometry, showed good correlation (Figure 2 and Figure S2 in Supporting Information File 1), with the stability constant for 2@β-CD K = 190 ± 50 M−1. Formation of the inclusion complex was

• values by the WINEQNMR program [51] according to the model for the formation of 1:1 stoichiometry of the inclusion complex 2@β-CD. Irradiation of 1 in the presence of acrylonitrile (AN). Complexation of 2 with β-CD, and formation of a ternary complex AN@2@β-CD. Photochemistry of 2 in the presence of AN

Synthesis, antiinflammatory activity, and molecular docking studies of bisphosphonic esters as potential MMP-8 and MMP-9 inhibitors

• Abimelek Cortes-Pacheco,
• María Adelina Jiménez-Arellanes,
• Francisco José Palacios-Can,
• José Antonio Valcarcel-Gamiño,
• Rodrigo Said Razo-Hernández,
• María del Carmen Juárez-Vázquez,
• Adolfo López-Torres and
• Oscar Abelardo Ramírez-Marroquín

Beilstein J. Org. Chem. 2020, 16, 1277–1287, doi:10.3762/bjoc.16.108

• = zinc complexation; highlighted in blue = most relevant residues; dashed pink lines = π–π interactions; grey = hydrophobic interactions. 2D schematic representations of the MMP-9 catalytic site, with 3–6 and the most relevant interactions. Red = hydrogen bonds; dotted bonds = zinc complexation

Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates

• Phil M. Pithan,
• Sören Steup and
• Heiko Ihmels

Beilstein J. Org. Chem. 2020, 16, 904–916, doi:10.3762/bjoc.16.82

• photochromism, i.e., a blue shift of the absorption maximum of the merocyanine form [5][19][27][28][29], and increased stability of the latter towards the thermal back reaction [21][28][30][31][32][33][34]. In this context, the complexation of metal cations has also been exploited to utilize this compound class

• ][80]. The reaction was apparently promoted by the complexation of the metal ions as such oxazole derivatives were originally only observed as intermediates during the photooxidation of spirooxazines in aerated solutions [78][81]. In another case, Uznanski et al. demonstrated that in the presence of

Rhodium-catalyzed reductive carbonylation of aryl iodides to arylaldehydes with syngas

• Zhenghui Liu,
• Peng Wang,
• Zhenzhong Yan,
• Suqing Chen,
• Dongkun Yu,
• Xinhui Zhao and
• Tiancheng Mu

Beilstein J. Org. Chem. 2020, 16, 645–656, doi:10.3762/bjoc.16.61

• equivalent RhCl3 complexation with three molecular PPh3 takes place forming Rh(PPh3)3Cl, which participated in the subsequent catalytic process. Herein, Rh(III) is reduced to Rh(I), with concomitant oxidation of PPh3 to PPh3=O. A quite interesting fact is that Rh(PPh3)3Br and Rh(PPh3)3I afforded much lower

Regioselectively α- and β-alkynylated BODIPY dyes via gold(I)-catalyzed direct C–H functionalization and their photophysical properties

• Takahide Shimada,
• Shigeki Mori,
• Masatoshi Ishida and
• Hiroyuki Furuta

Beilstein J. Org. Chem. 2020, 16, 587–595, doi:10.3762/bjoc.16.53

• prepared regioselectively, through the C–H alkynylation of 1 without any directing groups. In addition, the corresponding dipyrromethane 2, which is a precursor of BODIPY, was first transformed into the alkynylated form under catalytic conditions, and subsequent oxidation followed by boron complexation to

• mixture was treated with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to give the α,α'-diethynyl-substituted dipyrrin 7a. Subsequent boron complexation in the presence of trimethylsilyl chloride (TMSCl) as a fluoride scavenger afforded 4a in 16% yield over three steps. Separately, α-ethynyl

A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions

• Pezhman Shiri and
• Jasem Aboonajmi

Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52

• ligand was attached on reversed-phase 3-aminopropyl-functionalized silica gel (APSi) in dichloromethane as a solvent. The complexation reaction of the resulting Schiff base, named iminopropyl-functionalized silica gel (IPSi), with [Cu(CH3CN)4]PF6 and CuSO4 produced Cu(I)@IPSi (1a) and Cu(II)@IPSi (1b

• -functionalized nanosilica. Finally, the complexation reaction of Cu(II) with a supported ligand on propylamine-functionalized nanosilica, 10, was performed to produce a Cu(II) benzimidazole–salen complex supported by imine-functionalized silica (BS–Cu(II)@SiO2 (11), Scheme 2). The nanocatalyst 11 was used to

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• precursors. However, asymmetric synthesis can be used as strategy to introduce stereogenic P-atoms into the ligand’s backbone. The borane complexation approach is a unique stereoselective way for introducing a P-stereogenic center. Benoit et al. [2] reported on the synthesis of 2-phenyl-1,3,2

[1,3]/[1,4]-Sulfur atom migration in β-hydroxyalkylphosphine sulfides

• Katarzyna Włodarczyk,
• Piotr Borowski and
• Marek Stankevič

Beilstein J. Org. Chem. 2020, 16, 88–105, doi:10.3762/bjoc.16.11

• -carbon atom, which was quite straightforward under these acidic conditions. To understand the completely different selectivity in Lewis acid-catalyzed rearrangements, DFT was again applied to the reaction between 20 and AlCl3 (Scheme 10). Compound 20 underwent a complexation with an AlCl3 molecule

Preparation of anthracene-based tetraperimidine hexafluorophosphate and selective recognition of chromium(III) ions

• Qing-Xiang Liu,
• Feng Yang,
• Zhi-Xiang Zhao,
• Shao-Cong Yu and
• Yue Ding

Beilstein J. Org. Chem. 2019, 15, 2847–2855, doi:10.3762/bjoc.15.278

• + and the complex 3·Cr3+ are represented by εr and εc. The complexation stoichiometry between 3 and Cr3+ was established by using Job’s method (inset of Figure S5, Supporting Information File 1). When the molar fraction (χ) of 3 was 0.5, the ΔAχ value for 3·Cr3+ reached a maximum, which indicated that

• the complexation stoichiometry between 3 and Cr3+ was 1:1 in 3·Cr3+ [8][52][53]. To measure the selectivity of Cr3+ complexation by 3, displacement experiments were carried out (Supporting Information File 1, Figure S7). Firstly, 30 equiv of Cr3+ were added to solutions of 3 containing 30 equiv of K

• that Cr3+···π interactions are not uncommon, and they have been reported in diaryl chromium complexes [54][55]. Besides, Cr3+···N interactions in 3·Cr3+ did not appear relevant for complexation. The reasons were that (1) the signal m, corresponding to the CH2 fragment beside the nitrogen atom of the

Photoreversible stretching of a BAPTA chelator marshalling Ca²⁺-binding in aqueous media

• Aurélien Ducrot,
• Arnaud Tron,
• Robin Bofinger,
• Ingrid Sanz Beguer,
• Jean-Luc Pozzo and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

• in the UV, assigned to n–π* and π–π* transitions [38]. The calcium complexation studies of 1E and 1Z were performed under pseudo-intracellular conditions (100 mM KCl, 30 mM MOPS, pH 7.2). In the absence of ions, the spectra of 1E (Figure 6a) comprised absorption bands at 298 nm (ε: 5815 M−1 cm−1) and

• 359 nm (ε: 6728 M−1 cm−1). The complexation of Ca2+ (Figure 6a) induced a blue-shifting and a decrease of the absorption bands of 1E at 291 nm (ε: 4748 M−1 cm−1) and 355 nm (ε: 5230 M−1 cm−1). The spectrum of 1Z (Figure 6b) exhibited two absorption bands at 303 nm (ε: 5450 M−1 cm−1) and 348 nm (ε

• : 2700 M−1 cm−1). The complexation of Ca2+ (Figure 6b) induced blue-shifting and a decrease of the absorption band intensities of 1E at 297 nm (ε: 4900 M−1 cm−1) and 345 nm (ε: 3000 M−1 cm−1). After linearizing the spectral changes via a Hill plot, a 1:1 binding with a Kd of 0.102 μM in the case of 1E

Formation of alkyne-bridged ferrocenophanes using ring-closing alkyne metathesis on 1,1’-diacetylenic ferrocenes

• Celine Bittner,
• Dirk Bockfeld and
• Matthias Tamm

Beilstein J. Org. Chem. 2019, 15, 2534–2543, doi:10.3762/bjoc.15.246

• potentials recorded for the Ag+/Ag couple, which are strongly solvent dependent and vary from 0.04 V in acetonitrile to 0.65 V in DCM [98]. Therefore, oxidation should occur in the latter solvent, while silver(I) complexation could be expected in more coordinating solvents. Consequently, addition of a

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

• to the electron-poor nature of the pyridine ring. Herein, we demonstrate the encapsulation of Me4N+ cations inside a dimeric hydrogen-bonded pyridine[4]arene capsule, which contradicts with earlier assumptions. The complexation of a cationic guest inside the pyridine[4]arene dimer has been detected

• been previously detected by ESI-MS [7]. Very recently, with the help of ion mobility mass spectrometry (IM-MS), we showed that pyridine[4]arenes favor encapsulation of neutral molecules over anionic species and anions are in fact complexed in an exo-position (exclusion complexation) between the lower

• size are well-known for their ability to encapsulate small alkylammonium cations inside the dimer, especially quaternary ammonium cations [12][13][14]. As the cavity sizes of both pyridinearene and resorcinarene dimers are comparable, alkylammonium cations were chosen as the guests for complexation

Combining the Ugi-azide multicomponent reaction and rhodium(III)-catalyzed annulation for the synthesis of tetrazole-isoquinolone/pyridone hybrids

• Gerardo M. Ojeda,
• Prabhat Ranjan,
• Pavel Fedoseev,
• Lisandra Amable,
• Upendra K. Sharma,
• Daniel G. Rivera and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2019, 15, 2447–2457, doi:10.3762/bjoc.15.237

• peptides and the formation of isoquinolones; so it is expected that in intermediate B the substrate behaves as a tridentate ligand for the Rh(III) center [37][62][63][64][65]. However, such a complexation must be reversible to allow a further ligand exchange with the acetylene to form intermediate C. The

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

• literature there are still challenges to find selective iodide receptors due to its low basicity, large size and low charge density. There is an expectation that the combination of strong hydrogen-bonding sites and a large cavity could cause strong complexation with larger halide ions [55]. In 2016 a

• density of the triazolium derivative. Rigid macrocycles 12 display selective complexation with I− because of the complementary size of the cavity of the macrocyclic ring and the iodide ion. In addition, the acidity of the inner protons of 12 is higher than the corresponding neutral analogue which also

• helped to increase the ability of complexation of 12 with iodide [56]. 2.7. Functional molecular crystal and materials Combining anion–arene interactions and controlling the electron-transfer or charge-transfer process concerning an anionic guest by using a cyclophane is uncommon [57] but can be realized

Multiple threading of a triple-calix[6]arene host

• Veronica Iuliano,
• Roberta Ciao,
• Emanuele Vignola,
• Carmen Talotta,
• Patrizia Iannece,
• Margherita De Rosa,
• Annunziata Soriente,
• Carmine Gaeta and
• Placido Neri

Beilstein J. Org. Chem. 2019, 15, 2092–2104, doi:10.3762/bjoc.15.207

• dialkylammonium axles [17][18][19][20][21][22][23][24][25][26] by exploiting the inducing effect of the superweak tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (TFPB) anion that gives free ‘naked’ dialkylammonium cations. In addition, we have reported interesting examples of endo-cavity complexation of

α-Photooxygenation of chiral aldehydes with singlet oxygen

• Dominika J. Walaszek,
• Magdalena Jawiczuk,
• Jakub Durka,
• Olga Drapała and
• Dorota Gryko

Beilstein J. Org. Chem. 2019, 15, 2076–2084, doi:10.3762/bjoc.15.205

• ’ = ΔA/c × d, where c is the molar concentration of the chiral ligand, assuming 100% complexation (A = absorption; d = path length of the cell). Δε’ is expressed in [M−1 cm−1] units. Conformational analysis and ECD calculations The conformational search was performed with ComputeVOA [35] using the MMFF94

Synthesis and anion binding properties of phthalimide-containing corona[6]arenes

• Meng-Di Gu,
• Yao Lu and
• Mei-Xiang Wang

Beilstein J. Org. Chem. 2019, 15, 1976–1983, doi:10.3762/bjoc.15.193

• noncovalent interactions between anions and the tetrazine rings. Keywords: anion–π interactions; coronarenes; host–guest complexation; N-functionalized phthalimides; O6-corona[3]arene[3]tetrazines; Introduction Synthetic macrocycles [1][2] are always attractive and important because they are unique

• . Upon complexation with a halide, the planar aromatic ring adopted a heavily pinched boat conformation, a result consistent with theoretical prediction [49]. We also examined the host–guest interaction in solution phase employing NMR and UV–vis spectroscopy and fluorescence technology. Unfortunately

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

• complexation between 1 and (R or S)-2) or 1:5 stoichiometric ratio (for complexation between 1 and amino acids methyl esters). In all cases except monodentate amines (PheOMe, ValOMe) we observed precipitation of the complexes. Samples [1(PheOMe)2] and [1(ValOMe)2] were obtained by mixing of 1 with PheOMe∙HCl

• in methanol-d4. All complexes have 1:2 stoichiometry, consistent with formation of neutral salts, i.e., 1(LysOMe)2, 1(ArgOMe)2 and 1(HisOMe)2. The comparison of NMR spectra of the complexes with the spectra of the substrates reveals considerable complexation induced shifts, mainly for the guest

• splitting was noticed for [1(ʟ-, ᴅ/ʟ-LysOMe)2]MeOH (Figure S29, Supporting Information File 1). CD spectroscopy was further used to analyze complexation processes. For complexes 1(LysOMe)2, 1(ArgOMe)2, and 1(HisOMe)2 the CD effects are observed for bands at 300 nm – in the region where chiral components are

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

• developed by us. We found that compounds 2 and 3 exist in the neutral state solely as enol tautomers due to intramolecular hydrogen bonding involving the tautomeric hydroxy group and that the complexation shifts the equilibrium to the K form. Although 3 exhibits a 3D structure and as a result, shows high

• stability constants upon complexation, the selectivity is rather low, which can be attributed to the crown ether complexation features in general. Developing the system further, leads to modification of the ionophore part by replacing the crown ether with other ionophores, such as done in the case of 4 and

• achieved only when R’ = NMe2 (Scheme 2). Theoretical modelling of structures 4 and 5 have also shown that only one of the carbonyl groups from the ionophore unit really participates in the capturing of the metal ion upon complexation. Therefore, the aim of the current article is to estimate theoretically