Synthesis and properties of quinazoline-based versatile exciplex-forming compounds

• Rasa Keruckiene,
• Simona Vekteryte,
• Ervinas Urbonas,
• Matas Guzauskas,
• Eigirdas Skuodis,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 1142–1153, doi:10.3762/bjoc.16.101

• . After completion of the reaction, water was added to the mixture until precipitation appeared. The precipitate was collected by filtration and washed with plenty of water to remove excess CuCl2, NH4OAc, and reduced copper salt. Compound Q1 (1.4 g, 78%) was obtained as yellowish crystals. 1H NMR (400 MHz

Synthesis of esters of diaminotruxillic bis-amino acids by Pd-mediated photocycloaddition of analogs of the Kaede protein chromophore

• Esteban P. Urriolabeitia,
• Pablo Sánchez,
• Alexandra Pop,
• Cristian Silvestru,
• Eduardo Laga,
• Ana I. Jiménez and
• Carlos Cativiela

Beilstein J. Org. Chem. 2020, 16, 1111–1123, doi:10.3762/bjoc.16.98

• of the organometallic core, precipitation of black Pd0 and concomitant formation of the cyclobutanes 5, as represented in Scheme 3. The methoxycarbonylation reaction to give 5 was not as general as the previous steps to give oxazolones 2 or cyclopalladated 3 and 4. In the case of para- or meta-aryl

Efficient synthesis of dipeptide analogues of α-fluorinated β-aminophosphonates

• Marcin Kaźmierczak and
• Henryk Koroniak

Beilstein J. Org. Chem. 2020, 16, 756–762, doi:10.3762/bjoc.16.69

• (TFE) as a solvent [34][35]. The free amines 13 were converted into stable oxalate salts 14 with quantitative yields. The precipitation reactions proceeded in the presence of 1 equiv of oxalic acid in diethyl ether (Scheme 3) [36]. Unlike amines 13, salts 14 are very stable and can be stored for months

Visible-light-induced addition of carboxymethanide to styrene from monochloroacetic acid

• Kaj M. van Vliet,
• Nicole S. van Leeuwen,
• Albert M. Brouwer and
• Bas de Bruin

Beilstein J. Org. Chem. 2020, 16, 398–408, doi:10.3762/bjoc.16.38

• under the applied reaction conditions. The photoredox activation of monochloroacetic acid leads to the formation of precipitate during the reaction (see Figure 4), again indicating catalyst precipitation/deactivation. Works in the group of Noël and others have revealed that flow chemistry can increase

• acid group seems to be advantageous for the activation of monochloroacetic acid, but the apolar solvent in combination with formation of HCl is likely to cause catalyst deactivation/precipitation. This effect is more pronounced if electron-poor styrenes are used. We also found indications that a

Photocontrolled DNA minor groove interactions of imidazole/pyrrole polyamides

• Sabrina Müller,
• Jannik Paulus,
• Jochen Mattay,
• Heiko Ihmels,
• Veronica I. Dodero and
• Norbert Sewald

Beilstein J. Org. Chem. 2020, 16, 60–70, doi:10.3762/bjoc.16.8

• ]. Strikingly, no positive ICD effect on the CD spectrum was observed upon addition of the E-configured polyamides to the same dsDNA sequences, which indicates that they did not bind to the minor groove of the short dsDNA. Importantly, no precipitation was observed during the measurement. We hypothesize that

Design, synthesis and investigation of water-soluble hemi-indigo photoswitches for bioapplications

• Daria V. Berdnikova

Beilstein J. Org. Chem. 2019, 15, 2822–2829, doi:10.3762/bjoc.15.275

• of the dimethylamino-substituted hemi-indigo Z-1a was observed in water with 10% DMSO, i.e., only irradiation with violet light (420 nm) led to the residual isomerization (Figure 1A). Additionally, the hemi-indigo Z-1a was hardly soluble in aqueous medium and rather fast precipitation took place even

• irradiation after which the isosbestic point was lost and the absorption intensity started decreasing due to slow precipitation of the compound from the aqueous solution (Figure 1B). The presence of the second methoxy group ensured a better stability of aqueous solutions of the dimethoxy derivative Z-1c. In

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