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Search for "precipitation" in Full Text gives 321 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
New metathesis catalyst bearing chromanyl moieties at the N-heterocyclic carbene ligand
Beilstein J. Org. Chem. 2015, 11, 2795–2804, doi:10.3762/bjoc.11.300
- . Imidazolinium salt 14 was obtained by treatment of 13 with trimethyl orthoformate in 73% yield. It is worth noting that ethylenediamine 13 and imidazolinium salt 14 were sufficiently pure after precipitation, thus chromatographic purification was not necessary. Some specific effects are observed in the NMR
- (35 mg, 0.65 mmol) was added in a similar manner as described in [40]. The reaction mixture was refluxed for 2 h. Solids were filtered off and the filtrate was evaporated to dryness. The resulting oil was stirred overnight with diethyl ether causing precipitation of a white solid (160 mg, 73% yield
Assembly of synthetic Aβ miniamyloids on polyol templates
Beilstein J. Org. Chem. 2015, 11, 2646–2653, doi:10.3762/bjoc.11.284
- are known to form fibrils and there is no way to stop the process until complete precipitation. Intermediate soluble oligomers were identified as neurotoxic agents, but they are difficult to study because of their heterogeneous composition and transient character due to the onset of amyloid formation
- , such as those forming amyloids. The solubility of the assembly should be maintained throughout the experiment and precipitation strictly avoided to reach the thermodynamic equilibrium with the formation of the most stable miniamyloid in solution. Not all functional groups listed above for the
Inclusion complexes of 2-methoxyestradiol with dimethylated and permethylated β-cyclodextrins: models for cyclodextrin–steroid interaction
Beilstein J. Org. Chem. 2015, 11, 2616–2630, doi:10.3762/bjoc.11.281
- approximate unit cell dimensions (a ≈ 19.2, b ≈ 24.4, c ≈ 32.8 Å), results which were subsequently confirmed by a single crystal X-ray diffraction study of the same phase obtained via the co-precipitation method. (Relevant PXRD traces and single crystal data are provided in Supporting Information File 1
- employed for preliminary investigation of single crystals of a putative inclusion complex between 2ME and DIMEB, prepared using the co-precipitation method. (Details of the thermal analysis of the DIMEB complex of 2ME are provided in the Supporting Information File 1). The crystals, immersed in silicone
- complex between 2ME and the fully methylated host TRIMEB was prepared by the co-precipitation method and initially examined by HSM. (Details of the thermal analysis of the TRIMEB complex of 2ME are provided in Supporting Information File 1). Upon heating the crystals under silicone oil, no dehydration was
Size-controlled and redox-responsive supramolecular nanoparticles
Beilstein J. Org. Chem. 2015, 11, 2388–2399, doi:10.3762/bjoc.11.260
- avoid precipitation. Wintgens et al. showed the formation of SNPs by controlling the host–guest ratio and the total concentration of components with a neutral polymer backbone [13]. Recently, our group [2][14][15] formed SNPs by varying the ratio of neutral monovalent stoppers and multivalent
- synthesized by a reaction of 1-(chlorocarbonyl)ferrocene with the terminal amino group of methoxypoly(ethylene glycol)amine (Mw = 5000 g/mol) in dichloromethane, using an excess of triethylamine as a base, followed by precipitation from diethyl ether. To evaluate the association constant of the Fc moiety with
- over paper, the solvent was removed by evaporation and the remaining precipitate was redissolved in 2 mL chloroform. The chloroform solution was added dropwise to 40 mL of diethyl ether, giving immediate precipitation of a yellow solid, which was filtrated and dried in a vacuum oven at 40 °C overnight
Easy access to heterobimetallic complexes for medical imaging applications via microwave-enhanced cycloaddition
Beilstein J. Org. Chem. 2015, 11, 2202–2208, doi:10.3762/bjoc.11.239
- obtained by precipitation from a concentrated methanolic solution by slow addition of diethyl ether. Compound 3 was reacted with Ga(NO3)3 to lead to 10b in 94% yield after flash chromatography. The IR spectrum of 10b exhibits the characteristic band of the carbonyl stretching vibration from 1722 cm−1 to
- propargyl NOTA was performed by precipitation in diethyl ether in 94% yield. To prepare the gallium complex 12b, propargyl NOTA 4 and Ga(NO3)3 were dissolved, at pH 3, in water and then refluxed for 30 min. The pH of the reaction was adjusted (AcONa 0.5 M), in each case, to optimize the complexation kinetic
Olefin metathesis in air
Beilstein J. Org. Chem. 2015, 11, 2038–2056, doi:10.3762/bjoc.11.221
- exctraction with water or precipitation with ether. With a catalyst loading of 10 mol % in refluxing nondegassed dichloromethane, very high conversions were achieved in less than 1 hour for di- and trisubstituted olefins. Towards the end of 2009, the Meier group reported the use of Grubbs (15), Hoveyda–Grubbs
New aryloxybenzylidene ruthenium chelates – synthesis, reactivity and catalytic performance in ROMP
Beilstein J. Org. Chem. 2015, 11, 1910–1916, doi:10.3762/bjoc.11.206
- corresponding phosphine in order to bind the HCl liberated during the reaction, which resulted in a significant increase in the reaction yield. Complexes 8–10 were easily isolated by precipitation with methanol or hexane from concentrated solution in methylene chloride (isolated yields = 86–90%). 1H NMR spectra
- chloride anion into the coordination sphere of ruthenium. Exposition of complex 8 to one equivalent of HCl brought a change in the solution colour from green to light-green. The fine-crystalline light-green precipitate was isolated from the post-reaction mixture by precipitation with hexane with 95
Synthesis and structures of ruthenium–NHC complexes and their catalysis in hydrogen transfer reaction
Beilstein J. Org. Chem. 2015, 11, 1786–1795, doi:10.3762/bjoc.11.194
- volatiles were evaporated under reduced pressure. The residue was washed with water and dried in vacuo. The yellow residue was dissolved in MeCN and concentrated to about 2 mL. The addition of Et2O induced precipitation of the product as a yellow solid. Yield: 190 mg, 53%. Anal. calcd for C16H20F12N8P2Ru: C
A facile synthetic route to benzimidazolium salts bearing bulky aromatic N-substituents
Beilstein J. Org. Chem. 2015, 11, 1656–1666, doi:10.3762/bjoc.11.182
- triethyl orthoformate at almost reflux temperature (145 °C) for reaction times between 10 and 20 min. Then TMSCl was added in large excess all at once leading to precipitation of greyish products, which indicated the formation of the benzimidazolium chlorides. In this way not only the known compound 1-Cl
Dicarboxylic esters: Useful tools for the biocatalyzed synthesis of hybrid compounds and polymers
Beilstein J. Org. Chem. 2015, 11, 1583–1595, doi:10.3762/bjoc.11.174
- obtaining high molecular weight polyesters by lipase catalysis. This problem can be circumvented by the synthesis of telechelics, oligomers with functional ends. The synthesis of oligomers avoids the precipitation of polymers during the synthesis. The functional ends of the telechelics can be used in a
Preparation of a disulfide-linked precipitative soluble support for solution-phase synthesis of trimeric oligodeoxyribonucleotide 3´-(2-chlorophenylphosphate) building blocks
Beilstein J. Org. Chem. 2015, 11, 1553–1560, doi:10.3762/bjoc.11.171
- phosphorylated with bis(benzotriazol-1-yl) 2-chlorophenyl phosphate. The “outdated” phosphotriester strategy, based on coupling of PV building blocks in conjunction with quantitative precipitation of the oligodeoxyribonucleotide with MeOH is applied. Subsequent release of the resulting phosphate and base
- -protected oligodeoxyribonucleotide trimer 3’-pTpdCBzpdGibu-5’ as its 3’-(2-chlorophenyl phosphate) was achieved by reductive cleavage of the disulfide bond. Keywords: disulfide linker; oligodeoxyribonucleotides; phosphotriester chemistry; precipitation; soluble support; Introduction Synthetic nucleic
- -hydroxybenzotriazole promoted phosphotriester coupling [11][22][23] and efficient purification of the support bound product by precipitation from MeOH after each deprotection and coupling step. Results and Discussion The synthesis of the disulfide tethered tetrakis-O-({4-[(2-hydroxyethyldisulfanyl)methyl]-1H-1,2,3
Pyridine-promoted dediazoniation of aryldiazonium tetrafluoroborates: Application to the synthesis of SF5-substituted phenylboronic esters and iodobenzenes
Beilstein J. Org. Chem. 2015, 11, 1494–1502, doi:10.3762/bjoc.11.162
- excess of KI) [14]. The side-product in the iodination of 3 was bis(pyridine)iodonium tetrafluoroborate, which can be easily isolated from the reaction mixture by precipitation upon addition of diethyl ether. This iodonium salt was first synthetized by Barluenga [85] and later used for mild iodination of
Synthesis and evaluation of the biostability and cell compatibility of novel conjugates of nucleobase, peptidic epitope, and saccharide
Beilstein J. Org. Chem. 2015, 11, 1352–1359, doi:10.3762/bjoc.11.145
- conjugates exhibit excellent solubility in water without resulting in hydrogelation or precipitation. We observed that only the mixture of a proper pair of TTPV-containing (e.g., 5) and LGFNI-containing (8) conjugates self-assembles to form nanofibers and results in a supramolecular hydrogel. Moreover, the
The synthesis of active pharmaceutical ingredients (APIs) using continuous flow chemistry
Beilstein J. Org. Chem. 2015, 11, 1194–1219, doi:10.3762/bjoc.11.134
- ) and hexane were combined with the crude reaction product followed by passage through a membrane separator. The hexane layer was subsequently collected and treated with hydrochloric acid (5 M in IPA) leading to the precipitation of diphenhydramine hydrochloride (92) in high yield (~90%) and purity (~95
- precipitation and clogging problems, thus a pressure chamber was developed [94] that would act as a pressure regulator allowing this step to be scaled up in flow in order to provide 114 on multigram scale (134 g/h). A Knorr pyrazole formation between 114 and commercially available hydrazine 115 had previously
Advances in the synthesis of functionalised pyrrolotetrathiafulvalenes
Beilstein J. Org. Chem. 2015, 11, 1112–1122, doi:10.3762/bjoc.11.125
- the cyclised product 14. Crude material of sufficient purity for the following step can be isolated by precipitation (see the Experimental section in the Supporting Information File 1). Transchalcogenation of crude 14 affords 15 and aromatisation of crude 15 using 2,3-dichloro-5,6-dicyano-1,4
Synthesis of photoresponsive cholesterol-based azobenzene organogels: dependence on different spacer lengths
Beilstein J. Org. Chem. 2015, 11, 1089–1095, doi:10.3762/bjoc.11.122
- (precipitation), respectively. Insoluble systems in which the potential gelator could not be dissolved even at the boiling point of the solvent were designated as insoluble (I). Conclusion In summary, we have synthesized seven cholesterol-based compounds with azobenzene groups. The compounds with different
Tuning the size of a redox-active tetrathiafulvalene-based self-assembled ring
Beilstein J. Org. Chem. 2015, 11, 966–971, doi:10.3762/bjoc.11.108
- % yield after precipitation in ethyl acetate. In contrast with assembly M4L2 for which the presence of through-space interactions (Figure 4a) between the coligand phenyl units (dppf) and pyridyl groups result in an upfield shift of their signals (Figure 2b) compared to L1, the pyridyl protons are in this
Peptide–polymer ligands for a tandem WW-domain, an adaptive multivalent protein–protein interaction: lessons on the thermodynamic fitness of flexible ligands
Beilstein J. Org. Chem. 2015, 11, 837–847, doi:10.3762/bjoc.11.93
- precipitation. Experimental results were compared with parameters obtained from molecular dynamics simulations in order to understand the observed differences between the three carrier materials. In summary, the more rigid and condensed peptide–polymer conjugates based on the dextran scaffold seem to be
- multivalency of binding and/or the degree of crosslinking. Thus, the method enables the identification of polymer–protein aggregates containing several polymers and proteins in a complex. No precipitation of the multicomponent aggregates that interfered with ITC measurements was observed during the experiments
Orthogonal dual-modification of proteins for the engineering of multivalent protein scaffolds
Beilstein J. Org. Chem. 2015, 11, 784–791, doi:10.3762/bjoc.11.88
- successful glycan attachment was provided by tryptic digest and MS/MS-analysis of Gal-3, which showed functionalization of two specific Aha residues (see Table S5 in Supporting Information File 1). It should be noted that higher concentrations of Cu2+ also led to precipitation and loss of protein material
Multivalent polyglycerol supported imidazolidin-4-one organocatalysts for enantioselective Friedel–Crafts alkylations
Beilstein J. Org. Chem. 2015, 11, 730–738, doi:10.3762/bjoc.11.83
- loss of activity due to immobilization, albeit moderate enantioselectivities were observed. Moreover, easy recovery by selective precipitation allowed the reuse of the catalyst for three cycles. Keywords: Friedel–Crafts; homogeneous catalysis; hyperbranched polyglycerol; imidazolidin-4-one
- such as high loading capacity combined with the solubility characteristics of the respective dendrimers [20][21]. As a macromolecule, the supported catalyst can be recovered from the reaction media by selective precipitation, dialysis or filtration techniques, depending on its particular physical
- and 4b showed poor solubility in solvents with low polarity, thus allowing for an easy recovery in 60–70% yield after selective precipitation using Et2O. The utility of our soluble support was examined in the catalytic efficiency of recovered PG-57 (4b) (Table 7). Catalyst 4b was used three times in
Probing multivalency in ligand–receptor-mediated adhesion of soft, biomimetic interfaces
Beilstein J. Org. Chem. 2015, 11, 720–729, doi:10.3762/bjoc.11.82
- Recently, we introduced micrometer-sized SCPs composed of crosslinked PEG-diacrylamide hydrogels as probes [15]. Here, we used the ability of PEG-diacrylamide to phase separate from an aqueous solution to form microscopic droplets by means of precipitation using sodium sulfate as a kosmotrope. At
- for the synthesis of carboxylated PEG SCPs PEG microparticles were synthesized by precipitation polymerization in a similar manner as described in ref. [9]. Briefly, PEG-diacrylamide (Mn = 8000 Da) [26] (50 mg, 6.3 µmol) was dispersed in a 1 M sodium sulfate solution (10 mL). The UV photoinitiator
Trifluoromethyl-substituted tetrathiafulvalenes
Beilstein J. Org. Chem. 2015, 11, 647–658, doi:10.3762/bjoc.11.73
- were not able to determine the magnetic response of the FeCl4− salt as the crystals are polluted with the starting electrolyte, due to the precipitation technique used to recover these highly soluble salts. Conclusion Compared with other EWG such as –CN or –CO2Me, the CF3 substituent plays on the TTF
Highly selective generation of vanillin by anodic degradation of lignin: a combined approach of electrochemistry and product isolation by adsorption
Beilstein J. Org. Chem. 2015, 11, 473–480, doi:10.3762/bjoc.11.53
- acidification and precipitation of remaining lignin. The latter represents a significant advantage compared with conventional work-up protocols of lignin solutions. Keywords: adsorption; electrochemistry; lignin; nickel; renewable resources; Introduction The biopolymer lignin is one of the most abundant and
- electrolysis the electrolyte contains large amounts of unreacted, respectively chemically modified lignin. A conventional approach for product recovery includes acidification of the mixture, which leads to precipitation of lignin. Filtration followed by liquid–liquid extraction results in the clean product 1
- solution and the moderate yields of 1 which can be achieved by these processes. Consequently, alternative concepts are necessary to allow product removal without precipitation of lignin and acidification of the whole reaction mixture. For this purpose the applicability of strongly basic anion exchange
A procedure for the preparation and isolation of nucleoside-5’-diphosphates
Beilstein J. Org. Chem. 2015, 11, 469–472, doi:10.3762/bjoc.11.52
- (triphenylphosphoranylidene)ammonium] pyrophosphate (PPN pyrophosphate) was used in the SN2 displacements of the tosylate ion from 5’-tosylnucleosides to afford nucleoside-5’-diphosphates. Selective precipitation permitted the direct isolation of nucleoside-5’-diphosphates from crude reaction mixtures. Keywords: NDP
- ’-tosylnucleosides 1b–d were then exposed to the same reaction conditions and reaction progress was monitored by 31P NMR spectroscopy (Table 1). In order to remove inorganic pyrophosphate from the crude reaction mixtures we developed selective precipitation procedures. To ensure that these procedures were readily
- acetone, where acetone served as the precipitating solvent. A systematic study of conditions was performed in order to allow selective precipitation of pyrophosphate ions. Variables included; TEAB buffer concentration and volume, the concentration of the sodium iodide solution in acetone and the volume of
Chemoselective O-acylation of hydroxyamino acids and amino alcohols under acidic reaction conditions: History, scope and applications
Beilstein J. Org. Chem. 2015, 11, 446–468, doi:10.3762/bjoc.11.51
- , thus enabling direct chemoselective conversion of the hydroxyamino acid to the O-acyl derivative. Precipitation of the reaction product as a (preferably) crystalline amine salt would further aid the convenience and attractiveness of this methodology. But, such methodology has in fact existed for a
- dissolved in a mixture of hydrochloric acid and glacial acetic acid and acetylated in a few minutes by slow addition of a large excess of acetyl chloride at 0 °C. The product was obtained as the crystalline hydrochloride salt through precipitation by addition of Et2O. The O-acetyl hydrochlorides of hydroxy
- HCl, addition of more acetic anhydride and heating of the reaction mixture to 54 °C for 30 min, the mixture was subsequently concentrated under reduced pressure, quenched with EtOH, and the product was isolated at the >10 g scale, as the hydrochloride salt, by precipitation with Et2O. Such O,O
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