Mechanochemical Friedel–Crafts acylations

• Mateja Đud,
• Anamarija Briš,
• Iva Jušinski,
• Davor Gracin and
• Davor Margetić

Beilstein J. Org. Chem. 2019, 15, 1313–1320, doi:10.3762/bjoc.15.130

• anthracene in 95% yield. This [4π + 4π] cycloreversion in mechanochemical conditions is analogous to previously described dissociation of labile anthracene/C60 cycloadduct [52]. When the reaction of 19 with 20 was carried out in solution (DCM, overnight), 60% of dimer was converted to anthracene, and traces

• ); aconversion from NMR analysis; bsolution reaction in flask, substrate/acylation reagent/AlCl3 ratio is 1:1:2.5; ball-milling details are given in Table 1. Scope of aromatic substrates in FCR under mechanochemical activation conditions. aIsolated yields. Mechanochemical regiodirected FCR of anthracene dimer

Switchable selectivity in Pd-catalyzed [3 + 2] annulations of γ-oxy-2-cycloalkenones with 3-oxoglutarates: C–C/C–C vs C–C/O–C bond formation

• Yang Liu,
• Julie Oble and
• Giovanni Poli

Beilstein J. Org. Chem. 2019, 15, 1107–1115, doi:10.3762/bjoc.15.107

• cycloaddition to form dimer 6 [45]. We next turned our attention to the [3 + 2] C–C/C–C annulation by using the conditions B and C in DMSO at 130 °C (Scheme 4). The 2-cyclohexenone 4-benzoate (2a) afforded the expected bicyclo[4.3.0]nonane-3,8-dione (5a) in 69% yield (64% from 1.0 mmol of 1a) under either

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

• nature of the halogen bond assembly. The crystal lattice of 1 contains two structurally different dimeric assemblies A and B, formally resulting in the mixture of a capsular dimer and a dimeric pseudo-capsule. 1H and 19F NMR analyses supports the existence of these halogen-bonded complexes and enhanced

• tube, only creating isolated pores in the cavity of the resorcinarene. Note that the two modes are present simultaneously in the crystal lattice, thus, the structure formally contains around 75% halogen bonded dimer, and 25% halogen bonded capsule. Additionally, the conformation difference could reveal

Diastereo- and enantioselective preparation of cyclopropanol derivatives

• Marwan Simaan and
• Ilan Marek

Beilstein J. Org. Chem. 2019, 15, 752–760, doi:10.3762/bjoc.15.71

• usually proceeds through single-electron transfer to dioxygen, leading to either a loss of stereoselectivity, degradation of the organocopper or to the formation of dimer as major products [71]. Therefore, it was clear that a different approach for the oxidation process was needed. Oxenoid, possessing the

Efficient synthesis of 4-substituted-ortho-phthalaldehyde analogues: toward the emergence of new building blocks

• Clémence Moitessier,
• Ahmad Rifai,
• Pierre-Edouard Danjou,
• Isabelle Mallard and
• Francine Cazier-Dennin

Beilstein J. Org. Chem. 2019, 15, 721–726, doi:10.3762/bjoc.15.67

• % yield. After completing the oxidation step with convincing results, the final step of the methoxy group removal was undertaken. Several studies showed that OPA reacts in the presence of water to form a cyclic 1,3-phthalandiol [21] or a dimer [22]. Taking this into account to access pure 4-HO-OPA, it was

Synthesis and selected transformations of 2-unsubstituted 1-(adamantyloxy)imidazole 3-oxides: straightforward access to non-symmetric 1,3-dialkoxyimidazolium salts

• Grzegorz Mlostoń,
• Małgorzata Celeda,
• Katarzyna Urbaniak,
• Marcin Jasiński,
• Vladyslav Bakhonsky,
• Peter R. Schreiner and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2019, 15, 497–505, doi:10.3762/bjoc.15.43

• isoamyl nitrate [35] or, as in the case of 2b, by oximation of 1,2-diphenylethane-1,2-dione [36]. 2,2,4,4-Tetramethylcyclobutane-1,3-dithione (11a) was prepared from the dimethylketene dimer (2,2,4,4-tetramethylcyclobutane-1,3-dione) by thionation using tetraphosphorus decasulfide [37]. Adamantan-1-yl

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• of the acid and the directionality of the hydrogen bond pattern of the acid dimer. Cross metathesis of monovinyl-substituted POSS with olefins has been reported for the first time by Marciniec [18]. It was demonstrated that monovinylheptaisobutyl-substituted octasilsesquioxane (monovinyl-POSS

Silanediol versus chlorosilanol: hydrolyses and hydrogen-bonding catalyses with fenchole-based silanes

• Falco Fox,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2019, 15, 167–186, doi:10.3762/bjoc.15.17

• chlorid stronger with two hydrogen bridges, than BIFOXSiCl(OH) (8) with just one hydrogen bridge. The BIFOXSi(OH)2 (9) dimer forms hydrogen bridges, which are stronger than hydrogen bridges with water, but less stronger than hydrogen bridges to chloride (50.97 kcal mol−1 vs 29.18 kcal mol−1 vs 19.88 kcal

• available (+)-fenchone has 98% enantiomeric purity, BIFOXSi(OH)2 can be further purified. rac-BIFOXSi(OH)2 crystallizes as a dimer from toluene (Figure 14). BIFOXSi(OH)2 (9) crystallizes as a tetramer from n-hexane (Figure 15), where six OH groups build a network of hydrogen bonds. Thus the polar core is

• points/transition states, as well as experimental details can be found in Supporting Information File 1. CCDC-1833170 (BIFOXSiCl2 (7)), CCDC-1833171 (BIFOXSiCl(OH) (8)), CCDC-1833172 (BIFOXSi(OH)2 (9, dimer)), CCDC-1833173 (BIFOXSi(OH)2 (9, tetramer)), CCDC-1833174 (BIFOXSiCl(OH) 8·acetone) and CCDC

Unexpected loss of stereoselectivity in glycosylation reactions during the synthesis of chondroitin sulfate oligosaccharides

• Teresa Mena-Barragán,
• José L. de Paz and
• Pedro M. Nieto

Beilstein J. Org. Chem. 2019, 15, 137–144, doi:10.3762/bjoc.15.14

• assays, deprotection of dimer 6 and tetramer 14β were accomplished (Scheme 5). Compound 14α was also submitted to the deprotection sequence to obtain a non-natural α-containing oligosaccharide. Basic hydrolysis using H2O2/LiOH and then NaOH followed by selective N-acetylation in MeOH afforded CS

Adhesion, forces and the stability of interfaces

• Robin Guttmann,
• Johannes Hoja,
• Christoph Lechner,
• Reinhard J. Maurer and
• Alexander F. Sax

Beilstein J. Org. Chem. 2019, 15, 106–129, doi:10.3762/bjoc.15.12

• , even today it is more often claimed than actually demonstrated that hydrogen-bonded complexes are predominantly stabilized by electrostatics [6]. If any other interaction but electrostatics is considered, it is “charge-transfer”, which suggests that the dimer stabilization is caused by an electron

• series starts with dipoles, whereas in non-polar molecules it starts with quadrupoles or higher multipoles. Accordingly, there will always be electrostatic interactions of different ranges between molecules with static multipoles. For example, the T-shaped equilibrium structure of the benzene dimer is

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

• ) inclusion complex, γ-CD dimer, and γ-CD monomer in HFIP. Interestingly the γ-CD–C60 (1:1) inclusion complex, which is the supposed intermediate, is not detected (Figure 2c in Supporting Information File 1). Therefore, we considered that all C60 molecules in the solution should be present as the 2:1 complex

The influence of the cationic carbenes on the initiation kinetics of ruthenium-based metathesis catalysts; a DFT study

• Magdalena Jawiczuk,
• Angelika Janaszkiewicz and
• Bartosz Trzaskowski

Beilstein J. Org. Chem. 2018, 14, 2872–2880, doi:10.3762/bjoc.14.266

• interesting phenomenon, despite its very limited impact on their propensity to form transition metal complexes (Scheme 2) [50]. Many works have been devoted to the study of carbene dimerization and present evidence that mechanism of monomer–dimer equilibrium depends on the balance between the electronic and

• Gibbs free energy difference for the symmetric dimer A. In the case of carbene 3, the Gibbs free energy of dimerization could not be estimated due to instability of the monomer during geometry optimization. Thus, the results indicate higher stability of dimers for all examined NHC, which are in

Dispersion-mediated steering of organic adsorbates on a precovered silicon surface

• Lisa Pecher,
• Sebastian Schmidt and
• Ralf Tonner

Beilstein J. Org. Chem. 2018, 14, 2715–2721, doi:10.3762/bjoc.14.249

• reflected in the Lewis structure is the tilting of the molecule upon adsorption leading to a chair-like conformer bending over the dimer rows on the surface [7]. Starting from this precovered surface (i.e., decorated with one adsorbate in the unit cell), we now investigate the adsorption of a second

• molecule of 1 on a neighbouring dimer leading to structure 3 (Figure 2). Although repulsive interactions might be expected for adsorption close to a rather large adsorbate, we find this mode to be the most stable adsorption mode for two molecules of 1 in the unit cell. Due to their conformational

• . This can be seen in the difference plot between the PES of the clean and precovered surface in Figure 5c. Only weak preference for the surface dimer adjacent to the already adsorbed molecule is found (less than 5 kJ·mol−1), which can be attributed to weak electrostatic attraction between the two

Non-native autoinducer analogs capable of modulating the SdiA quorum sensing receptor in Salmonella enterica serovar Typhimurium

• Matthew J. Styles and
• Helen E. Blackwell

Beilstein J. Org. Chem. 2018, 14, 2651–2664, doi:10.3762/bjoc.14.243

• [37]. Recently, two groups reported X-ray crystal structures of full-length EHEC SdiA as a homodimer in the presence of four naturally occurring AHLs (shown in Figure 1B) [21][22]. These studies reveal a structure for the SdiA dimer that incorporates LBD and DBD domains comparable to those of the

Synergistic approach to polycycles through Suzuki–Miyaura cross coupling and metathesis as key steps

• Sambasivarao Kotha,
• Milind Meshram and
• Chandravathi Chakkapalli

Beilstein J. Org. Chem. 2018, 14, 2468–2481, doi:10.3762/bjoc.14.223

• SM cross coupling followed by RCM as key steps [50]. To this end, dibromo compound 123 was subjected to diallylation by using allylboronate ester 12 to form the diallyl derivative 124 (73%). Treatment of compound 124 with G-I catalyst 1 gave unsaturated dimer 126 (30%) and monomer 125 (15

Efficient catalytic alkyne metathesis with a fluoroalkoxy-supported ditungsten(III) complex

• Henrike Ehrhorn,
• Janin Schlösser,
• Dirk Bockfeld and
• Matthias Tamm

Beilstein J. Org. Chem. 2018, 14, 2425–2434, doi:10.3762/bjoc.14.220

• ]. The desired hexakis(fluoroalkoxide) dimer [Mo2{OC(CF3)2Me}6] (Mo2F6) was first isolated by D. Rogers and his group by salt metathesis of [Mo2Cl6(dme)2] with 6 equiv of NaOC(CF3)2Me (Scheme 2) [73]. This reaction affords a red, sparingly soluble complex in moderate yield (28%). The bimetallic tungsten

Nucleoside macrocycles formed by intramolecular click reaction: efficient cyclization of pyrimidine nucleosides decorated with 5'-azido residues and 5-octadiynyl side chains

• Jiang Liu,
• Peter Leonard,
• Sebastian L. Müller,
• Constantin Daniliuc and
• Frank Seela

Beilstein J. Org. Chem. 2018, 14, 2404–2410, doi:10.3762/bjoc.14.217

• ) sulfate and ascorbic acid. TLC monitoring showed that the cyclization failed. Then, tris(benzyltriazoylmethyl)amine (TBTA) [40][41][42] was added as catalyst and macrocycle 4 was formed in 71% yield, which is extremely high for an intramolecular cyclization. The dimeric product 3 and the cyclic dimer 5

Dynamic light scattering studies of the effects of salts on the diffusivity of cationic and anionic cavitands

• Anthony Wishard and
• Bruce C. Gibb

Beilstein J. Org. Chem. 2018, 14, 2212–2219, doi:10.3762/bjoc.14.195

• − leads to an increase in the hydrodynamic diameter, with NaBr giving the largest increase to 2.6 nm. This corresponds to the formation of a dimer aggregate. Aggregation was even more extreme with the I− salts. All I− salts caused extensive aggregation of the host, and a determination of the maximum size

Selective formation of a zwitterion adduct and bicarbonate salt in the efficient CO₂ fixation by N-benzyl cyclic guanidine under dry and wet conditions

• Yoshiaki Yoshida,
• Naoto Aoyagi and
• Takeshi Endo

Beilstein J. Org. Chem. 2018, 14, 2204–2211, doi:10.3762/bjoc.14.194

• until 102 °C (i) and 173 °C (ii), respectively, and then the thermal decomposition of 2 has occurred completely around 270 °C (iii). This three-step behavior of weight loss suggested the dimer form of 2, which was constructed by the weak interaction between the anionic oxygen on the trapped CO2 and the

• active hydrogen on the nitrogen atom. Namely, one molecule of CO2 was released from the dimer of 2 in the first step, and then the intermediate complex was prepared from 1 and 2 due to the coordination between two anionic oxygens on the trapped CO2 and two active hydrogens on the guanidine moiety. Then

• , another CO2 molecule was released from the intermediate complex (2+1 dimer) and the dimer was decomposed into two molecules of 1 in the second step. The observed weight loss due to the released CO2 in each step agreed with the theoretical one (obs. (i) 10.3%, (ii) 10.6%, and (iii) 78.4%, theor. (i) 10.1

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

• strong absorption bands (≈450 and 800 nm), which yield an orange-brown solution. Initially, the low-energy band of 2●+ between 600–1000 nm was interpreted as a signature for an unusually stable TTF dimer [31]. However, later investigations showed that this band is an intrinsic SOMO-1→SOMO transition in

• so-called mixed-valence dimer (12) ●+. A mixed-valence dimer can be identified by splitting of the first TTF oxidation potential into two distinguishable waves. This change in redox behavior can be followed by electrochemical methods such as cyclic voltammetry. Another indication for a mixed-valence

• dimer interaction can be an emergent low-energy absorption band, usually in the NIR region. Both monomers show usually no absorption in this region. The radical-cation dimer (1●+)2 instead forms from two 1●+ radical cations and exhibits a very unusual binding situation. Whereas both monomers are

Evaluation of dispersion type metal···π arene interaction in arylbismuth compounds – an experimental and theoretical study

• Ana-Maria Preda,
• Małgorzata Krasowska,
• Lydia Wrobel,
• Philipp Kitschke,
• Phil C. Andrews,
• Jonathan G. MacLellan,
• Lutz Mertens,
• Marcus Korb,
• Tobias Rüffer,
• Heinrich Lang,
• Alexander A. Auer and
• Michael Mehring

Beilstein J. Org. Chem. 2018, 14, 2125–2145, doi:10.3762/bjoc.14.187

• the sum of the energies of all unrelaxed monomers (crystal structure geometry) included in the tetramer or dimer. Interaction energies of tetrameric, trimeric, and dimeric structures can yield information about the additivity of intermolecular interactions. Additionally, interaction energies of all Bi

• with this specific monomer are broken, which can involve contacts between neighboring molecules or long-range interactions. In tetramer 1a-1 the energy needed to remove one of the outer monomers (3 and 4) is almost equal to the interaction energy of one Bi···π arene dimer. This indicates that only one

• dimer breaks. To remove one of the inner monomers (2 or 1) an energy of 92 kJ mol−1 is required. This energy is very close to the sum of the interaction energies of two dimers. For example, Eremove of monomer 2 in tetramer 1a-1 is roughly the sum of the interaction energies of two Bi···π arene dimers

The phenyl vinyl ether–methanol complex: a model system for quantum chemistry benchmarking

• Dominic Bernhard,
• Fabian Dietrich,
• Mariyam Fatima,
• Cristóbal Pérez,
• Hannes C. Gottschalk,
• Axel Wuttke,
• Ricardo A. Mata,
• Martin A. Suhm,
• Melanie Schnell and
• Markus Gerhards

Beilstein J. Org. Chem. 2018, 14, 1642–1654, doi:10.3762/bjoc.14.140

• repetition rate of 64 Hz. For the spectrum of the PVE–MeOH dimer, 3 million FIDs were co-added. A resulting signal-to-noise ratio of about 500:1 to 600:1 for the stronger transitions of the dominant complex allowed us to determine the positions of the carbon atoms with respect to the center of mass of the

• are shown in Figure 3. Besides methanol monomer, methanol dimer and a signal clearly attributed to a larger cluster, only a single, reasonably narrow absorption at 3625 cm−1 is observed. It can be attributed to mixed dimers of MeOH with PVE and allows for a single rigorous conclusion, due to the

• linearity of the technique and the comparable IR absorption cross section of all predicted dimer conformations (cf. Table 1 and Table S1, Supporting Information File 1): the global minimum structure and any other, higher lying isomers which are initially formed and impeded from relaxation to the global

Drug targeting to decrease cardiotoxicity – determination of the cytotoxic effect of GnRH-based conjugates containing doxorubicin, daunorubicin and methotrexate on human cardiomyocytes and endothelial cells

• Livia Polgár,
• Eszter Lajkó,
• Pál Soós,
• Orsolya Láng,
• Marilena Manea,
• Béla Merkely,
• Gábor Mező and
• László Kőhidai

Beilstein J. Org. Chem. 2018, 14, 1583–1594, doi:10.3762/bjoc.14.136

• bifunctional daunorubicin-GnRH-III conjugates without spacer and modified in position 4 with Lys; (e) {GnRH-III(Dau=Aoa-C)}2 dimer and conjugates modified in position 4 with N-MeSer; (f) GFLG or YRRL spacer containing monomer and dimer conjugates (g) GnRH-III conjugates containing methotrexate and daunorubicin

• conjugates containing doxorubicin without spacer sequence; (c) with spacer sequence GFLG; (d) oxime bond-linked, mono- and bifunctional daunorubicin-GnRH-III conjugates without spacer and modified in position 4 with Lys; (e) {GnRH-III(Dau=Aoa-C)}2 dimer and conjugates modified in position 4 with N-MeSer; (f

• ) GFLG or YRRL spacer containing monomer and dimer conjugates; (g) GnRH-III conjugates containing methotrexate and daunorubicin. Comparative study of cytotoxic effects and cardiotoxicity elicited by GnRH-based antitumor compounds (1–15) and reference substances (AN-152, Dox, Dau, Mtx). IC50 values show

Steric “attraction”: not by dispersion alone

• Ganna Gryn’ova and
• Clémence Corminboeuf

Beilstein J. Org. Chem. 2018, 14, 1482–1490, doi:10.3762/bjoc.14.125

• not even a limit and stable diamondoid dimer with a central C–C bond as long as 1.71 Å has been achieved [7][8]. Bulky alkyl groups assist not only in achieving the longest C–C bonds, but also the shortest intermolecular H···H contacts [9], which are otherwise tackled by squeezing them inside the

• cages [10]. Intermolecular interactions in hydrocarbons are also subject to significant dispersion contribution. In the unsaturated systems, from benzene dimer to higher acenes and, ultimately, graphenes, dispersion is increasingly the key force behind the π–π stacking interactions [11]. Large and flat

• -tert-butylphenyl)methane dimer (the system mentioned above for its shortest intermolecular H···H contacts) comes from stabilizing electrostatics [9]. Similarly, the interaction energy difference between the all-meta-tert-butyl-hexaphenylethane and the bare hexaphenylethane features ≈14% electrostatic

Recent applications of chiral calixarenes in asymmetric catalysis

• Mustafa Durmaz,
• Erkan Halay and
• Selahattin Bozkurt

Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117

• reactions were compared to that of the model diphenylphosphino ferrocenes. When the allylpalladium chloride dimer was used as palladium precursor, good yields were obtained after 24 h. However, enantiomeric excesses for (S)-27 and (S)-28 (<5%) were lower than those obtained by using other phosphine-ether