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

• rim is the preferred mode of coordination (n = 2; Figure 2, structure a). In this construct the water dimer not only connects two oppositely located OH groups from the rim, but additionally interacts with four other OH groups and forms an elaborate hydrogen-bond network that almost occludes the

• against experimental data (dissociation energy, D0, in the gas phase) on water dimer. Frequency calculations for each M062X/6-31G(d,p) optimized construct were performed at the same level of theory. No imaginary frequency was found for the lowest energy configurations of any of the optimized structures

Synthesis of 9-O-arylated berberines via copper-catalyzed C_Ar–O coupling reactions

• Qiaoqiao Teng,
• Xinhui Zhu,
• Qianqian Guo,
• Weihua Jiang,
• Jiang Liu and
• Qi Meng

Beilstein J. Org. Chem. 2019, 15, 1575–1580, doi:10.3762/bjoc.15.161

• 9-O-phenylene-bridged berberine dimer (5) was synthesized by copper-catalyzed cross-coupling of tetrahydroberberrubine and aryl iodides, followed by oxidation with I2. Keywords: arylation; berberines; cross-coupling; copper; lipophilicity; structural modification; Introduction Berberine (BBR) is a

• were subsequently converted back to the respective 9-O-arylated berberines and 9-O-phenylene-bridged berberine dimer. Oxidation with DMSO-d6 was first attempted with 2a. It showed good stability at ambient temperature and only 16% conversion to the 9-O-Ph berberine 3a was noted after 72 h of heating at

• backbone was observed as with Br2 [5]. This makes I2 a better oxidant for the oxidation of tetrahydroberberines. Compounds 3a–o are yellow solids, which are soluble in CH2Cl2, CH3CN, DMSO and MeOH. In contrast, the phenylene-bridged dimer 5 is only sparingly soluble in DMSO and MeOH. The formation of the

2,3-Dibutoxynaphthalene-based tetralactam macrocycles for recognizing precious metal chloride complexes

• Li-Li Wang,
• Yi-Kuan Tu,
• Huan Yao and
• Wei Jiang

Beilstein J. Org. Chem. 2019, 15, 1460–1467, doi:10.3762/bjoc.15.146

• values for (TBA)2[PtCl4] and (TBA)2[PdCl4] were 189 ± 36 M−1 and 198 ± 15 M−1, respectively. It should be noted that PdCl42− is relatively labile at high concentrations and is in equilibrium with the palladate dimer (Pd2Cl62−) and chloride ions [32][39]. The formation of Pd2Cl62− was supported by an ESI

Introduction of an isoxazoline unit to the β-position of porphyrin via regioselective 1,3-dipolar cycloaddition reaction

• Xiujun Liu,
• Xiang Ma and
• Yaqing Feng

Beilstein J. Org. Chem. 2019, 15, 1434–1440, doi:10.3762/bjoc.15.143

• longer than the distance when MeOH coordinated to the Zn2+ ions [49]. This may attribute to the larger volume of the C6H4CO2Me group than MeOH when closing to the Zn2+ center. In the dimer structure, two planes defined by porphyrin macrocycles are parallel with a distance of 7.11 Å. The bulky substituent

• trimethylphenyl group) in CDCl3 (500 MHz, 25 °C). The representative dimeric structure of 3a according to the crystal structure (a) and enantiomeric dimer structure in crystal (b–d, the phenyl group at meso-positions and 2,6-dichlorophenyl group were omitted for the sake of clarity). The distances of Zn–O (c) and

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

• occurred upon oxygen-directed metalation. The resulting oxiranyllithium probably exists as a dimer in solution, as it has been nicely evidenced by structural characterization and NMR studies of the lithiated o-trifluoromethylstyrene oxide [37]. Such dimerization obviously stabilizes the oxiranyllithium

• species. Applied to oxiranyllithium derived from cis or trans-alkynyloxiranes, such dimer may easily form from the cis-oxirane (Scheme 2, entry 4), but not from the trans-isomer, or at least the large steric constrain present in it may hamper its stability. Indeed, the long oxirane C–O bond adjacent to

• lithium observed by X-ray diffraction in the lithiated o-trifluoromethylstyrene oxide [37] may be further elongated due to hindrance introduced by the trans-substituent adjacent to the lithium atom of the second oxirane in the dimer (Scheme 2, entry 5). Such effect may facilitate the formation of the

Selenophene-containing heterotriacenes by a C–Se coupling/cyclization reaction

• Pierre-Olivier Schwartz,
• Sebastian Förtsch,
• Astrid Vogt,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2019, 15, 1379–1393, doi:10.3762/bjoc.15.138

• formed dimers showed some differences: in DTT 1 the molecules overlap in a parallel orientation whereas in DST 3 an antiparallel orientation of the molecules in the dimer was found. The degree of overlap was determined to 73% and 64% for DTT 1 and DST 3, respectively. Less degree of overlap (43–53% and

Selective detection of DABCO using a supramolecular interconversion as fluorescence reporter

• Indrajit Paul,
• Debabrata Samanta,
• Sudhakar Gaikwad and
• Michael Schmittel

Beilstein J. Org. Chem. 2019, 15, 1371–1378, doi:10.3762/bjoc.15.137

• , 3, and 4 and of the resulting products, i.e., rectangle 5, sandwich 6 and rhodium porphyrin dimer 7. Comparison of partial 1H NMR spectra (400 MHz, CD2Cl2, 298 K) of (a) ligand 2; (b) ligand 1; (c) porphyrin 3; (d) complex 7 = [(3)2(4)]; (e) rectangle 5 = [Cu4(1)2(2)2]4+]; (f) sandwich complex 6

• ); (c) after addition of 4.0 equiv of rhodium porphyrin 3, leading to formation of rectangle 5 and rhodium porphyrin dimer 7. (d) Further addition of 2.0 equiv of DABCO furnishes state II; (e) finally, addition of 4.0 equiv of rhodium porphyrin 3 recovered rectangle 5 along with 4.0 equiv of complex 7

One-pot activation–alkynylation–cyclization synthesis of 1,5-diacyl-5-hydroxypyrazolines in a consecutive three-component fashion

• Christina Görgen,
• Katharina Boden,
• Guido J. Reiss,
• Walter Frank and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 1360–1370, doi:10.3762/bjoc.15.136

• dimer of compound 5r (thermal ellipsoids at 30% probability). Glyoxylation–alkynylation (GA) and activation–alkynylation (AA) synthesis of alkynediones in a one-pot fashion. Consecutive three-component synthesis to give 5-benzoyl-3-phenyl-1H-pyrazole (6a) after alkaline deacylation of intermediate 5a

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