A chiral self-sorting photoresponsive coordination cage based on overcrowded alkenes

• Constantin Stuckhardt,
• Diederik Roke,
• Wojciech Danowski,
• Edwin Otten,
• Sander J. Wezenberg and
• Ben L. Feringa

Beilstein J. Org. Chem. 2019, 15, 2767–2773, doi:10.3762/bjoc.15.268

• formation of a new set of signals was observed. DOSY NMR confirmed the formation of an assembly with a hydrodynamic radius which was similar to that of the cage Pd2(stable Z-1)4. Precipitation of the metal centers in this assembly using tetrabutylammonium glutarate liberates the ligands and they were

• Pd2(stable Z-1)4, but to disassembly of the cage and formation of ill-defined complexes. Precipitation of the metal centers in these complexes identified the ligands as a mixture of both stable Z-1 and stable E-1 (originating from the PSS mixture), indicating that the THI does take place. A possible

AgNTf₂-catalyzed formal [3 + 2] cycloaddition of ynamides with unprotected isoxazol-5-amines: efficient access to functionalized 5-amino-1H-pyrrole-3-carboxamide derivatives

• Ziping Cao,
• Jiekun Zhu,
• Li Liu,
• Yuanling Pang,
• Laijin Tian,
• Xuejun Sun and
• Xin Meng

Beilstein J. Org. Chem. 2019, 15, 2623–2630, doi:10.3762/bjoc.15.255

• obtained in the reaction of ynamide 4a with 8a. Notably, after the completion of the reaction, a white precipitation was observed and filtered straightforwardly to afford the desired product 10aa in mostly quantitative yield. A tentative mechanism for the formation of 5-amino-1H-pyrrole-3-carboxamide 10aa

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

• solution of Ag(SbF6) (1 equiv) in DCM to a solution of 2a in DCM resulted in an immediate colour change from orange to dark green alongside with precipitation of a black solid, indicating the formation of elemental silver. A dark solid was isolated after filtration and evaporation of the solvent

A toolbox of molecular photoswitches to modulate the CXCR3 chemokine receptor with light

• Xavier Gómez-Santacana,
• Sabrina M. de Munnik,
• Tamara A. M. Mocking,
• Niels J. Hauwert,
• Shanliang Sun,
• Prashanna Vijayachandran,
• Iwan J. P. de Esch,
• Henry F. Vischer,
• Maikel Wijtmans and
• Rob Leurs

Beilstein J. Org. Chem. 2019, 15, 2509–2523, doi:10.3762/bjoc.15.244

• , which were commercially available or prepared as described in our previous communication [7]. A final methylation of the tertiary amine 12a–e with MeI in DCM and subsequent precipitation with MTBE (methyl tert-butyl ether) gave 2a–e as orange powders with ≥99% trans-isomer in moderate to high yield

• was selectively reduced with DIBAL-H to benzyl alcohols 23f–h, which were oxidized with Dess–Martin periodinane to the corresponding benzaldehyde 26f–h. Reductive amination of 26f–h with 7 gave the tertiary amines 13f–h. Methylation with iodomethane and subsequent precipitation gave 3f–h as orange

Self-assembled coordination thioether silver(I) macrocyclic complexes for homogeneous catalysis

• Zhen Cao,
• Aline Lacoudre,
• Cybille Rossy and
• Brigitte Bibal

Beilstein J. Org. Chem. 2019, 15, 2465–2472, doi:10.3762/bjoc.15.239

• slowly added to afford a precipitation. After filtration, the isolated solid was washed with diethyl ether and dried under vacuum. General procedure for the acetalization/cycloisomerization of alkyne 2: An oven-dried Schlenk tube was charged with the silver(I) catalyst (0.5–5 mol %), then degassed and

Indium-mediated C-allylation of melibiose

• Christian Denner,
• Manuel Gintner,
• Hanspeter Kählig and
• Walther Schmid

Beilstein J. Org. Chem. 2019, 15, 2458–2464, doi:10.3762/bjoc.15.238

• monosaccharides. Temperatures up to 65 °C led to elevated reaction rates (Table 1, entries 3, 5 and 6). However, higher temperatures caused concentration phenomena, which derived from the reflux of ethanol leading to precipitation of the starting material, which resulted in a significant decrease of the reaction

• resin followed by filtration and removal of the solvent under reduced pressure, led to precipitation of compound 3-syn, thereby causing problems during the ozonolysis. Thus, dichloromethane was added to the reaction mixture immediately after completed Zemplén-deprotection (as indicated by TLC) without

Photochromic diarylethene ligands featuring 2-(imidazol-2-yl)pyridine coordination site and their iron(II) complexes

• Andrey G. Lvov,
• Max Mörtel,
• Anton V. Yadykov,
• Frank W. Heinemann,
• Valerii Z. Shirinian and
• Marat M. Khusniyarov

Beilstein J. Org. Chem. 2019, 15, 2428–2437, doi:10.3762/bjoc.15.235

• cases, the mixing of in situ-prepared “Fe(H2B(pz)2)2“ with the ligands in MeOH resulted in the formation of red solutions. For ligand 6 bearing a CO2Et group, almost instant precipitation was observed. In contrast to 6, our attempts to obtain crystalline solids using 3, 4, and 7 were unsuccessful

• cyclohexenone moiety no longer forms the out-of-plane corner. Instead, the unsubstituted CH2 position twists out of the plane towards the thiophene moiety of another ligand 6. Long time precipitation of crystalline material resulted in a tetranuclear species [Fe2(H2B(pz)2)2Fe2(B(OMe)3(pz))2(6-H)2] (complex 9

Reversible switching of arylazopyrazole within a metal–organic cage

• Anton I. Hanopolskyi,
• Soumen De,
• Michał J. Białek,
• Yael Diskin-Posner,
• Liat Avram,
• Moran Feller and
• Rafal Klajn

Beilstein J. Org. Chem. 2019, 15, 2398–2407, doi:10.3762/bjoc.15.232

• precipitation and re-solubilization of 1 (Figure S25, Supporting Information File 1). Overall, the reaction taking place in the system can be written down as (E-1)22 → (Z-1)2 + Z-1. Interestingly, however, despite the existence of Z-1 as two distinct species (encapsulated and non-encapsulated), the NMR spectrum

• reported azobenzene complex, the photoisomerization was not accompanied by precipitation of the released Z-arylazopyrazole, which has good water solubility. The expulsion of the Z isomer was confirmed by diffusion-ordered NMR spectroscopy, which also showed that the released and the encapsulated Z

Cyclopropanation–ring expansion of 3-chloroindoles with α-halodiazoacetates: novel synthesis of 4-quinolone-3-carboxylic acid and norfloxacin

• Sara Peeters,
• Linn Neerbye Berntsen,
• Pål Rongved and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2019, 15, 2156–2160, doi:10.3762/bjoc.15.212

• fully consumed (judged by TLC) and gave a white precipitation. The white solid was centrifuged, the liquid carefully removed and the solid was washed with EtOAc and centrifuged 2–3 times to leave a pure off-white solid. Quinolone 3-carboxylate scaffold, norfloxacin (1) and ciprofloxacin (2). The effect

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

• analogous experiment was done with benzoate, due to the precipitation of an insoluble ferrocenium complex [40]. 2.4. Mechanically interlocked catenanes containing 1,2,3-triazolium macrocycles Mechanically interlocked molecules like rotaxane and catenane have attracted much attention in the field of

An overview of the cycloaddition chemistry of fulvenes and emerging applications

• Ellen Swan,
• Kirsten Platts and
• Anton Blencowe

Beilstein J. Org. Chem. 2019, 15, 2113–2132, doi:10.3762/bjoc.15.209

• irreversible precipitation of a product, and an inevitable shift in dynamic equilibrium. Several types of reversible reactions have been successfully employed in the formation of DCL, including transesterification, peptide bond exchange, disulphide exchange, olefin metathesis and boronic ester formation [189

Fluorinated azobenzenes as supramolecular halogen-bonding building blocks

• Esther Nieland,
• Oliver Weingart and
• Bernd M. Schmidt

Beilstein J. Org. Chem. 2019, 15, 2013–2019, doi:10.3762/bjoc.15.197

• Information File 1, Figure S17). This was also the key to being able to lower the temperature to characterize formation in the 1H NMR, where the solubility of the assemblies in benzene was improved by adding a solubilizing mesitylene group to the halogen bonding acceptor U1 to avoid precipitation of box A2

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

Identification of optimal fluorescent probes for G-quadruplex nucleic acids through systematic exploration of mono- and distyryl dye libraries

• Xiao Xie,
• Michela Zuffo,
• Marie-Paule Teulade-Fichou and
• Anton Granzhan

Beilstein J. Org. Chem. 2019, 15, 1872–1889, doi:10.3762/bjoc.15.183

• and Table 1), in order to achieve a satisfactory level of solubility in aqueous buffer (i.e., no visible precipitation at a dye concentration of 10 µM in K-100 buffer: 10 mM LiAsO2Me2, 100 mM KCl, pH 7.2). Dyes containing side-chain substituents (2a–6a) were obtained directly as bromide salts

• absorption bands of most dyes are blue-shifted by 10 to 30 nm and undergo a hypochromic effect, compared with organic solvents such as MeOH or DMSO. This behavior evidences a more or less significant aggregation propensity of dyes in aqueous medium, even though, in all tested cases, no visible precipitation

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

• in general a solvent is not required, in solution environments the formation of products is assisted if the solubility of MX or RnM' is limited, as their precipitation helps shift the equilibrium toward the product side. If ethers are used as solvents, for example, the low solubility of MX can be

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

• significant effect on the distribution of macrocycle homologues probably due to the non-reversible nature of the reaction. However, the salt was used as it facilitated precipitation of the crude product after aqueous work-up. The MALDI analysis (Supporting Information File 1, Figure S1) indicated that the

Ugi reaction-derived prolyl peptide catalysts grafted on the renewable polymer polyfurfuryl alcohol for applications in heterogeneous enamine catalysis

• Alexander F. de la Torre,
• Gabriel S. Scatena,
• Oscar Valdés,
• Daniel G. Rivera and
• Márcio W. Paixão

Beilstein J. Org. Chem. 2019, 15, 1210–1216, doi:10.3762/bjoc.15.118

• out with a concentrated basic solution. The use of a 1 M NaOH (5 mL) solution requires two washes of 10 min each but at the end of the reaction an emulsion may appear. In order to avoid this problem an excess of 0.1 M NaOH solution was used. Polymers were isolated by precipitation in petroleum ether

• , 175.5. PFA-supported catalyst 3. Compound 1 (476 mg, 1 mmol, 1.0 equiv), furfuryl alcohol (860 µL, 10 mmol, 10 equiv) and TFA (38 µL, 0.5 mmol) were reacted in CHCl3 (5 mL) according to the general procedure B. After precipitation in petroleum ether, polymer 3 was obtained as a black amorphous solid. IR

• , 0.5 mmol) were reacted in CHCl3 (5 mL) according to the general procedure B. After precipitation in petroleum ether, polymer 4 was obtained as a black amorphous solid. IR (KBr, cm−1): 3500, 3120, 2930, 1720, 1680, 1610, 1550, 1420, 1350, 1200, 1160, 1110, 1038, 780, 740, 600; microanalysis: N (1.36

Mechanochemical synthesis of hyper-crosslinked polymers: influences on their pore structure and adsorption behaviour for organic vapors

• Sven Grätz,
• Sebastian Zink,
• Hanna Kraffczyk,
• Marcus Rose and
• Lars Borchardt

Beilstein J. Org. Chem. 2019, 15, 1154–1161, doi:10.3762/bjoc.15.112

• interesting adsorbents with a dynamic adsorption behaviour. However, the low solubility of POPs is a main challenge in their synthesis protocols. Solution-based procedures, for example, suffer from almost instant precipitation and thus only produce materials with a low degree of polymerization [10]. In the

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

• those performed in DMSO were used for isolation of the complex by precipitation methods. The resulting complexes at specified ratios of the reactants are depicted in Scheme 1 and the details of the complexation behavior are described below. Complexation of cis-protected palladium(II) with ligand L1 at 1

• repeated in DMSO and the (PdL’)L-type complex [Pd(tmeda)(L1)](NO3)2 (1a, Scheme 1(i)) was isolated from the reaction mixture by a precipitation method that is described in the experimental section. The 1H NMR spectrum of the solution showed formation of a single discrete complex (Figure 2(ii)). Counter

• discrete complex. The reaction was repeated in DMSO and the PdL2-type complex [Pd(L1)2](NO3)2 (3a, Scheme 1c) was isolated from the reaction mixture by precipitation as described in the experimental section. Counter-anion (BF4−, ClO4− and OTf−) variation was also carried out to successfully prepare a

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• modified literature procedure (Scheme 3) [22]. The modification consists in the addition of a 10% molar excess of 4-(aza-15-crown-5)benzocarbaldehyde (3, Scheme 3) and usage of ethyl acetate as an additional solvent for product precipitation. Because of its better solubility in ethyl acetate the unreacted

• precipitation from ethanol/ethyl acetate 1:3 was needed to obtain analytically pure target dyes 4a–d. The dyes 4a and 4c were previously described [18][21] and were used as reference compounds. To the best of our knowledge dyes 4b and 4d are new compounds. The chemical structures of all dyes from the series

A chemically contiguous hapten approach for a heroin–fentanyl vaccine

• Yoshihiro Natori,
• Candy S. Hwang,
• Lucy Lin,
• Lauren C. Smith,
• Bin Zhou and
• Kim D. Janda

Beilstein J. Org. Chem. 2019, 15, 1020–1031, doi:10.3762/bjoc.15.100

• coating the protein’s surface (i.e., 10.0 copies). However, increasing the conjugation to a 1 mg scale caused the protein to precipitate immediately upon addition of HF-1 in 9:1 DMF/H2O solution, eliminating the possibility of conjugation. To mitigate this precipitation problem, glycerol was added to the

• ameliorate protein precipitation and conjugation issues. The linker placement at the phenethyl position greatly improved conjugation compared to the other phenylamide group; HF-4 had a hapten density of 21.1, drastically higher than HF-2 (hapten density: 12.6) and HF-3 (hapten density: 8.3). Gratifyingly, we

Fabrication, characterization and adsorption properties of cucurbit[7]uril-functionalized polycaprolactone electrospun nanofibrous membranes

• Changzhong Chen,
• Fengbo Liu,
• Xiongzhi Zhang,
• Zhiyong Zhao and
• Simin Liu

Beilstein J. Org. Chem. 2019, 15, 992–999, doi:10.3762/bjoc.15.97

• solvent for PCL. Turbidity/precipitation was observed when the volume ratio of the formic acid solution of CB[n] in the mixed solution was higher than 20% due to the poor solubility of PCL in formic acid solution. In order to keep the CB[n] content in the mixed solution as large as possible, the ratio of

Synthesis of polydicyclopentadiene using the Cp₂TiCl₂/Et₂AlCl catalytic system and thin-layer oxidation of the polymer in air

• Zhargolma B. Bazarova,
• Ludmila S. Soroka,
• Alex A. Lyapkov,
• Мekhman S. Yusubov and
• Francis Verpoort

Beilstein J. Org. Chem. 2019, 15, 733–745, doi:10.3762/bjoc.15.69

• , which reacts with R-olefin and a Lewis base to form stable crystalline titanacyclobutanes. Both titanium carbene and titanacycles are ROMP catalysts (Scheme 4). PDCPD polymers were obtained by precipitation in ethanol, dried and characterized by FTIR, NMR, and GPC. Figure 6 displays a typical infrared

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

• polymer was isolated by precipitation. As a result two block copolymers were obtained. The one containing 5% of POSS units was characterized by Mn = 26200 Da and PDI = 1.16 and the other one bearing 10% of POSS-substituted monomeric units, has a number average molecular weight Mn = 33200 Da and a

A convenient and practical synthesis of β-diketones bearing linear perfluorinated alkyl groups and a 2-thienyl moiety

• Ilya V. Taydakov,
• Yuliya M. Kreshchenova and
• Ekaterina P. Dolotova

Beilstein J. Org. Chem. 2018, 14, 3106–3111, doi:10.3762/bjoc.14.290

• ]. This compound was first obtained by Reid and Calvin in 1950 [15] by Claisen condensation of 2-acetylthiophene and ethyl trifluoroacetate in the presence of NaOEt in Et2O (Scheme 1). The purification procedure was laborious and included copper chelate precipitation and its subsequent acid decomposition

• optimization of reaction conditions was made for aliphatic esters. Since the Claisen condensation is accompanied by formation of side products, purification of a diketone is usually difficult. Steam distillation of the reaction mixture followed by precipitation of metal (Cu, Mg, Mn, Fe) chelates and their

• acidic decomposition [22][23] or preparative chromatography [33][34] were used to obtain a pure product. We have found that in most cases, simple vacuum distillation of the crude reaction mixture is sufficient to obtain pure β-diketones with fluorinated side-chain. Nevertheless, precipitation of the Cu