Functionalization of 4-bromobenzo[c][2,7]naphthyridine via regioselective direct ring metalation. A novel approach to analogues of pyridoacridine alkaloids

• Benedikt C. Melzer,
• Alois Plodek and
• Franz Bracher

Beilstein J. Org. Chem. 2019, 15, 2304–2310, doi:10.3762/bjoc.15.222

• , phenolates), acyl anions (generated by umpolung of aldehydes with imidazolium salts) and by palladium-catalyzed cross-coupling reactions (Suzuki, Stille) [10]. A related Stille cross coupling of a benzo[c][2,7]naphthyridine bearing a triflate group at C-5 gave an intermediate for the total synthesis of

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

• candidates for amide bond surrogates. Interestingly, 1,2,3-triazole units can act as sensors for both anions and cations via different binding mechanisms [16][17]. The heterocyclic ring N2 and N3 atoms could realize the selective recognition of the cations whereas the C5–H···anions electrostatic interaction

• results in the sensing of anions. In fact, strictly speaking this interaction is not a hydrogen bonding interaction seen as there is no X···H–Y unit (X, Y = O, N, F) but these interactions are often referred to as such in the literature. The anion binding can be enhanced by the alkylation of 1,2,3

• -triazole units to more electrophilic 1,2,3-triazolium units by influencing both hydrogen bonding-like and anion–π interactions. Moreover, halogen bond (XB) and chalcogen bond (ChB) interactions (see Figure 1) also been applied for the selective detection of anions by exchanging C5–H protons with halogens

1,2,3,4-Tetrahydro-1,4,5,8-tetraazaanthracene revisited: properties and structural evidence of aromaticity loss

• Arnault Heynderickx,
• Sébastien Nénon,
• Olivier Siri,
• Vladimir Lokshin and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2019, 15, 2059–2068, doi:10.3762/bjoc.15.203

• -positions (Figure 3). The distances between both >N–H and =N–H groups from the chlorine anions are shortened (2.410 and 2.194 Å, respectively, Figure 2). Examination of the bond distances within the N2–C1–C14–C13–N12 and N5–C6–C7–C8–N9 atom chains of 6a reveals almost full delocalization of the positive

• : infinite chains of the N–H···N=C shortened distances (N(2)···N(3) distance 3.047 Å, (Figure 11). The iodine anions are not involved in the intermolecular interactions. Conclusion Unlike previously described, 1,2,3,4-tetrahydro-1,4,5,8-tetraazaanthracene (3) is a thermally stable compound and can be

Naphthalene diimides with improved solubility for visible light photoredox catalysis

• Barbara Reiß and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 2043–2051, doi:10.3762/bjoc.15.201

• fluorescence quantum yields are rather low and fluorescence lifetimes are rather short due to ISC into the triplet state [50][51]. NDIs are reversibly reducible and their stable radical anions absorb in the visible to NIR light range [37]. The aromatic core of NDIs can be easily modified by substituents in

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

• adopt the conformation in which three phthalimide units are cis,trans-orientated. Acting as electron-deficient macrocyclic hosts, the synthesized O6-corona[3]arene[3]tetrazines self-regulated conformational structures to complex anions in the gas phase and in the solid state owing to the anion–π

• 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

• cavities [22]. We have also shown that the combination of and the interplay between heteroatoms and para-(het)arylenes produce diverse macrocycles with coarse- and fine-tunable cavity shapes and sizes. The resulting coronarenes exhibit interesting molecular recognition properties towards anions, cations

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

• depiction of a single chain is provided in Figure 1, and a partial packing diagram is given in Figure 2. The asymmetric unit contains three alkali metal cations and three substituted allyl anions, all in general positions. Each of the three metal sites is modeled as a site disorder of atoms types K and Cs

• the only recoverable material; extracted with toluene, it crystallized from solution as the solvate. A single crystal X-ray study analysis reveals bent polymeric chains of alternating K+ cations and [A']− anions. Each potassium is capped with a toluene molecule, bonded through cation–π interactions

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• ) as a solvent without any additive (Scheme 43). A good yield of the product was obtained by using benzyl cyanide substituted with EDG (4-OMe) rather than with an EWG due to the favourable oxidative release of cyanide anions from benzyl cyanide that favored the substitution of the iodide ion

An azobenzene container showing a definite folding – synthesis and structural investigation

• Abdulselam Adam,
• Saber Mehrparvar and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2019, 15, 1534–1544, doi:10.3762/bjoc.15.156

• ][22]. Beside the usage of the side chains of the amino acids and the azole rings for molecular recognition, the functional groups of the scaffolds of these cyclopeptides have also been applied as receptors for Y-shaped anions [23] and as ligands for copper(II) complexes [24][25]. Of special interest

Synthesis of pyrrolo[1,2-a]quinolines by formal 1,3-dipolar cycloaddition reactions of quinolinium salts

• Anthony Choi,
• Rebecca M. Morley and
• Iain Coldham

Beilstein J. Org. Chem. 2019, 15, 1480–1484, doi:10.3762/bjoc.15.149

• types of products. Conclusion In conclusion, we have found that carboxylic ester and amide-stabilised anions derived from quinolinium salts react with arylidenemalononitriles and N-methylmaleimide to give adducts in good yields and with very high stereoselectivity (single isomer products were isolated

Borylation and rearrangement of alkynyloxiranes: a stereospecific route to substituted α-enynes

• Ruben Pomar Fuentespina,
• José Angel Garcia de la Cruz,
• Gabriel Durin,
• Victor Mamane,
• Jean-Marc Weibel and
• Patrick Pale

Beilstein J. Org. Chem. 2019, 15, 1416–1424, doi:10.3762/bjoc.15.141

• Shimizu [6][7], and our experience on the metalation of alkynyloxiranes and reactivity studies of the so-formed alkynyloxirane anions [12][13], we explored the reaction of such anions with various boron derivatives in order to produce stereodefined α-enynes after Matteson-type rearrangement [14] and

• avoid any silyl migration [12]. As already shown [12][13], n-butyllithium proved to be very efficient, although stronger or complex bases are usually required to produce oxiranyl anions [1][2][24][25][26][27][28]. Upon deprotonation, the corresponding oxiranyllithium was sufficiently stable at −78 °C

Reversible end-to-end assembly of selectively functionalized gold nanorods by light-responsive arylazopyrazole–cyclodextrin interaction

• Maximilian Niehues,
• Patricia Tegeder and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2019, 15, 1407–1415, doi:10.3762/bjoc.15.140

• , the high negative ζ-potential evidences electrostatic repulsion between the particles and thus good colloidal stability against uncontrolled aggregation. It is well known that PEGylated surfaces and particles show a negative ζ-potential in water due to the preferential absorption of hydroxide anions

Enantioselective Diels–Alder reaction of anthracene by chiral tritylium catalysis

• Qichao Zhang,
• Jian Lv and
• Sanzhong Luo

Beilstein J. Org. Chem. 2019, 15, 1304–1312, doi:10.3762/bjoc.15.129

• (Scheme 1b). In our further explorations, we noticed that the dissociation of trityl phosphate was generally sluggish, thus limiting its applicability. To expand its utility, we report herein a metal-complexed phosphate anion for chiral carbocation catalysis. Weakly coordinating anions [22][23] have been

• widely used in inorganic and organic chemistry [24][25][26][27] as well as in polymer chemistry [28][29][30][31][32][33]. Although tritylium salts with various types of these counter anions based on B(III), Al(III), Ga(III), Fe(III), Nb(III), Ta(III), Y(III) and La(III) centers and ligands have been

• investigated in Lewis acid catalysis over the past decades, a chiral counter anion [34][35] with metal elements as the central atom, however, was seldom reported. Typically, the tritylium salts with weakly coordinating anions can be synthesized through a simple halide abstraction from the trityl halide in the

Bambusuril analogs based on alternating glycoluril and xylylene units

• Tomáš Lízal and
• Vladimír Šindelář

Beilstein J. Org. Chem. 2019, 15, 1268–1274, doi:10.3762/bjoc.15.124

• bind inorganic anions with high binding affinity and selectivity in both organic media and water [13][14]. Previously we used bambusurils to recognize and quantify anions in their complex mixtures at sub-micromolar concentrations by means of NMR [15]. However, sensing of anions by less expensive UV–vis

• of one molecule and methine and methylene hydrogen atoms of neighboring macrocycles. Finally, we investigated the affinity of the newly prepared bambusuril analogs 1a and 1b towards anions. The addition of halide anions in form of their tetrabutylammonium salts to the solutions of 1a and 1b did not

• induced any change in the NMR spectra of the macrocycles. This indicates that these macrocycles do not bind the studied anions. We assume that the cavity of the macrocycles is too small to be able to include any anions. Indeed the conformer 1b-1 with two facing glycolurils resembles the bambus[4]uril

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

• 658.14 and 285.57, respectively, which correspond to the cationic fragments [1b − BF4]+ and [1b − 2BF4]2+ that are formed due to the loss of one and two units of counter anions from 1b. The experimental and theoretical peak patterns were found to be in agreement. The data of 1c and 1d are given in

• anions from 3a. The experimental and theoretical peak patterns were found to be in agreement. The ESIMS spectrum of 3b is provided in Supporting Information File 1, Figure S34. Complexation of bare palladium(II) with ligand L1 at a 3:4 metal-to-ligand ratio A solution containing three equivalents of

• of the trinuclear complex 4a. It is proposed that the anion is essential to avoid charge repulsion between the metal centers in the ensuing cavities. However, the anions should be of fitting sizes only to get accommodated in the cavities so that discrete architectures are formed. Larger anions such

SO₂F₂-mediated transformation of 2'-hydroxyacetophenones to benzo-oxetes

• Revathi Lekkala,
• Ravindar Lekkala,
• Balakrishna Moku,
• K. P. Rakesh and
• Hua-Li Qin

Beilstein J. Org. Chem. 2019, 15, 976–980, doi:10.3762/bjoc.15.95

• satisfactory yields from the functionalized acyclic precursors generally requires good leaving groups and anions. A large number of synthetic methods has been described for the formation of oxetane derivatives and among them, two common strategies are widely applied. The first strategy engages an

Halogen bonding and host–guest chemistry between N-alkylammonium resorcinarene halides, diiodoperfluorobutane and neutral guests

• Fangfang Pan,
• Mohadeseh Dashti,
• Michael R. Reynolds,
• Kari Rissanen,
• John F. Trant and
• Ngong Kodiah Beyeh

Beilstein J. Org. Chem. 2019, 15, 947–954, doi:10.3762/bjoc.15.91

• 79.45 Å3 in MeOH@1 and 101.17 Å3 in MeCN@1 (rprobe = 1.2 Å) [34]. The deformation also shifts the relative positions of the N-alkyl “arms” and the halide anions, which additionally change the relative orientation of DIOFB XB donors when directional halogen bonding forms. Two DIOFB linked two MeOH-MeCN@1

• inversion, the two conformations show different dimerization modes (Supporting Information File 1, Figure S3). In 1&DIOFB_A, the two hex-NARBrs are linked by two DIOFB molecules via four Br···I halogen bonds with average RXB of 0.86. The two participating bromide anions are on adjacent “arms”; the remaining

• two Br− counterions are covered by the bent hexyl “arms”. In 1&DIOFB_B, the two DIOFB molecules link the two hex-NARBrs using the diametrically opposed Br− anions. The average RXB of these XBs is 0.98. In this second conformer, a space was created between the hosts, thus the hexyl groups bend inwards

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

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

• [7] followed by the lock-and-key concept of Emil Fischer in 1894 [8]. Weak or non-covalent interactions had been used systematically in the early 1960s by Lehn, Cram and Pederson to create targeted supramolecular architectures [9]. Small molecules, anions or cations could be assembled spontaneously

Coordination chemistry and photoswitching of dinuclear macrocyclic cadmium-, nickel-, and zinc complexes containing azobenzene carboxylato co-ligands

• Jennifer Klose,
• Tobias Severin,
• Peter Hahn,
• Alexander Jeremies,
• Jens Bergmann,
• Daniel Fuhrmann,
• Jan Griebel,
• Bernd Abel and
• Berthold Kersting

Beilstein J. Org. Chem. 2019, 15, 840–851, doi:10.3762/bjoc.15.81

• blue, O red, S yellow, metals flesh (Zn, Cd) or green (Ni)). Space filling representation of the packing of two symmetry-related [Zn2L(μ-azo-NMe2)]+ cations in crystals of 5·1.5MeCN. The ClO4− anions and solvate molecules are omitted for clarity. Structure of the [Cd2L(μ-azo-NMe2)]+ cation in crystals

• )]+ cations in crystals of 6·0.5MeOH. H atoms, ClO4− anions and solvate molecules are omitted for clarity. The C atoms of the azobenzene moieties are in pale blue. Structures of the two crystallographically independent [Ni2L(μ-azo-NMe2)]+ cations A (left) and B (right) in crystals of [Ni2L(μ-azo-NMe2)]ClO4

• . Right: Space filling representation of the packing of two [Cd2L(μ-azo-CO2Me)]+ cations in crystals of 8·MeCN. H atoms, BPh4− anions and solvate molecules are omitted for clarity. Plots of the effective magnetic moment μeff for 2 (open circles), 4 (open squares), and 7 (open triangles) at H = 0.5 T (2, 7

Influence of per-O-sulfation upon the conformational behaviour of common furanosides

• Alexey G. Gerbst,
• Vadim B. Krylov,
• Dmitry A. Argunov,
• Maksim I. Petruk,
• Arsenii S. Solovev,
• Andrey S. Dmitrenok and
• Nikolay E. Nifantiev

Beilstein J. Org. Chem. 2019, 15, 685–694, doi:10.3762/bjoc.15.63

• approximation with 6-311++G** basis set was employed [31]. Sulfates in the studied structures were treated as anions without presence counterions. COSMO [32] model was applied with built-in parameters for water. Geometry optimizations were performed until the RMS gradient reached a value less than 10−4

Polyaminoazide mixtures for the synthesis of pH-responsive calixarene nanosponges

• Antonella Di Vincenzo,
• Antonio Palumbo Piccionello,
• Alberto Spinella,
• Delia Chillura Martino,
• Marco Russo and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2019, 15, 633–641, doi:10.3762/bjoc.15.59

• importance of electrostatic interactions in the sequestration process. In fact, anions 11–14 are sequestered nearly quantitatively from solution. By contrast, cationic 15 is absorbed much less effectively and, as expected, binding is favored under the most alkaline pH conditions. Conclusion In the present

Selective benzylic C–H monooxygenation mediated by iodine oxides

• Kelsey B. LaMartina,
• Haley K. Kuck,
• Linda S. Oglesbee,
• Asma Al-Odaini and
• Nicholas C. Boaz

Beilstein J. Org. Chem. 2019, 15, 602–609, doi:10.3762/bjoc.15.55

• dyes and transition metal complexes, hypohalous acids, and persulfate anions [12][34][35][36][37][38][39][40]. An important class of catalyzed benzylic C–H to C–O transformations are those catalyzed by N-oxyl radicals. Specifically, N-oxyl radical catalysts based upon the N-hydroxyphthalimide (NHPI

Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• salts are not considered as pharmaceutically acceptable in general, the triflate form of NR+ must be converted to salts with pharmaceutically acceptable counter anions, such as chloride, before becoming a consumable product. Ion exchange was used by Szczepankiewicz et al. [32] to generate the

Thiol-free chemoenzymatic synthesis of β-ketosulfides

• Adrián A. Heredia,
• Martín G. López-Vidal,
• Marcela Kurina-Sanz,
• Fabricio R. Bisogno and
• Alicia B. Peñéñory

Beilstein J. Org. Chem. 2019, 15, 378–387, doi:10.3762/bjoc.15.34

• ; sulfoxide; thiol-free; Introduction Throughout the years, several strategies have been developed to build up organic compounds bearing a sulfide moiety [1][2]. Often, thiols (or the corresponding thiolate anions) are employed as nucleophilic sulfur reagents in order to react with a suitable electrophile [3

First synthesis of cryptands with sucrose scaffold

• Patrycja Sokołowska,
• Michał Kowalski and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2019, 15, 210–217, doi:10.3762/bjoc.15.20

• convenient chiral platform for such macrocycles [9][10]. Several of them, such as 5 (Figure 1), are able to differentiate enantiomers of α-phenylethylammonium salt [11][12]. Sucrose dimers containing two urea or thiourea units (6 or 7) are able to complex anions [13][14]. More complex derivatives with

A simple and effective preparation of quercetin pentamethyl ether from quercetin

• Jin Tatsuzaki,
• Tomohiko Ohwada,
• Yuko Otani,
• Reiko Inagi and
• Tsutomu Ishikawa

Beilstein J. Org. Chem. 2018, 14, 3112–3121, doi:10.3762/bjoc.14.291

• to rotation of the OH group at 5 position destabilizes the system dramatically, as in 2C, by 9.7 kcal/mol (in the gas phase) and 5.4 kcal/mol (in DMSO); however, the hydrogen bond is not crucial for the overall planar structure. The structures and energies of all possible isomeric mono-anions derived

• . The relative energies of all isomeric oxyanions are shown in Figure 4. All the monoanions (anions 2A) derived from the stable neutral conformer 2A were more stable than those (anions 2B) from the conformer 2B. Among the oxyanions at the OH group at 3 position (3-anions), we calculated the species (3

• unstable species among the anions 2A, and the negative charge of the anionic oxygen is small (−0.679). While the thermodynamic stability (instability) and kinetic reactivity in methylation reaction do not always coincide, these features are consistent with the experimental finding that the OH group at 5