Constructing Multicomponent Materials Involving Inclusion of Mono- and Bis-Imidazolium Cations in Gadolinium(III)-p-sulfonatocalixarene Coordination Networks.
A novel p-tert-butylcalixarene trisferrocenoyl ester molecule L has been prepared; the X-ray crystal structure of the ethanol complex of L reveals the guest molecule bound deep in the cavity of the calixarene.
In this research, potential applicability of p-sulfonic acid calixarene (CSA) as a catalyst in the synthesis of pharmaceutically significant coumarin derivatives was evaluated. Efficient catalytic activity as well as recyclability makes CSA an exciting organocatalyst for researchers who are searching for more environmentally friendly catalysts with less harmful and more proficient capabilities. Moreover, herein, the earlier strategies in the synthesis of coumarin derivatives were developed using CSA as a catalyst in one-pot and solvent-free procedure. In this study we demonstrated especial and valuable organocatalyst for the synthesis of coumarins.
This thesis describes the successful synthesis of three nitrile functionalised calixarenes, mono-, distal- and tetra-, as bulky scaffolds to be used as precursors in the synthesis of dithiadiazolyl functionalised calixarenes.
Due to environmental concerns, in the last decade a variety of catalysts has been introduced in organic synthesis; among them are organocatalysts which have shown recyclability and nontoxicity as well as efficiency in producing key products. One of the most interesting supramolecular organic structures that have played so many roles in different areas especially in chemistry is calixarene and its derivatives.
Encouraged by the results obtained from the model reaction, the methodology was extended to a variety of aldehydes (aromatic, aliphatic, α,β-unsaturated) with ethyl acetoacetate and urea in the presence of 0.2 mol % calixarene sulfonic acid for the condensation reaction to give the products 4a–m. Thiourea has been used with similar success to provide corresponding 3,4-dihydropyrimidine-2(1)-thiones 4n–p. In , the reaction proceeded smoothly with aromatic aldehydes carrying either electron-donating or electron-withdrawing groups in the -, -, and -positions in moderate to high yields of 67−93%. However, the condensation reaction of aliphatic aldehydes (entries 4k, 4l) exhibited lower yields (of 46–57%) and longer reaction time compared with aromatic aldehydes, which was due to the decomposition or polymerization of aliphatic aldehydes under acidic conditions.
The same model reaction in the presence of 0.2 mol% calixarene sulfonic acid was carried out using different molar ratio of reagents. The best results were obtained with a 1 : 1 : 1.5 ratio of 4-cholorobenzaldehyde to ethyl acetoacetate and urea.
A mixture of aldehyde (1.0 mmol), ethyl acetoacetate (1.0 mmol) and urea or thiourea (1.5 mmol) in refluxing ethanol (3.0 mL) contained calixarene sulfonic acid (0.2 mol %) was assisted by ultrasonic irradiation for a specified period. Reactions were monitored by TLC. Then, the mixtures were allowed to be added into cooled water, the solid was filtered, and washed with few cold water, ethanol, and dried under vacuum to give the pure product.
Melting points were determined with capillaries with an YRT-3 microscope apparatus and were uncorrected. 1H-NMR spectra were recorded at 600 MHz on a Bruker AV-600 spectrometer. IR spectra were obtained on a Nicolet Fourier transform (FT)-IR 8400 spectrometer (KBr disc). All reagents and solvents were commercial reagents with analytical grade. Calixarene sulfonic acid was prepared according to the published method.) Reactions were monitored by TLC on 2.5 mm Merck silica gel F254 strips.
) Reaction conditions: aromatic aldehydes (1.0 mmol), ethyl acetoacetate (1.0 mmol), urea (1.5 mmol), calixarene sulfonic acid (0.2 mol%), in refluxing ethanol (3.0 mL) under ultrasonic irradiation.
However, the addition of lithium bis(trimethylsilyl)amide to mono-nitrile calixarene in the synthesis of the mono-dithiadiazolyl functionalised calixarene was unsuccessful.
The fine chemicals including p-tert-butylphenol, formaldehyde solution (37%), diphenyl ether, ethylacetate, methanol, and sodium hydroxide were purchased from Merck (Schuchardt, Germany). Ethyl acetoacetate, resorcinol, bisphenols, salicylic acid, 2,5-dihydroxy salicylic acid, phosphorus oxychloride, and silicagel were obtained from Fluka (Switzerland). Parent tert-butylcalixarene was synthesized according to Gutsche procedure published in . Then it was detertiobutylated and sulfonated simultaneously by Shinkai method using concentrated sulfuric acid () . After further purification described in the literature, the obtained product was applied as a proficient acidic organocatalysis (Figures and ). Melting points were determined with an Electrothermal 9100 Melting Point Apparatus. IR and 1H NMR spectra were recorded, respectively, on Bruker FTIR Spectrometer and Bruker Avance III 400MHz NMR Spectrometer. GC-MS analyses were carried out on Shimadzu GC 17A gas chromatograph coupled with MS-QP 5000 Shimadzu Mass Spectrometer (Tokyo, Japan). Elemental analyses were performed by CHN Rapid Heraeus Elemental Analyzer (Wellesley, MA).
One-pot and efficient protocol for preparation of some potent pharmaceutically valuable coumarin derivatives under solvent-free condition via direct coupling using biologically nontoxic organocatalyst, calixarene tetrasulfonic acid (CSA), was introduced. Calixarene sulfonic acid has been incorporated lately as a magnificent and recyclable organocatalyst for the synthesis of some organic compounds. Nontoxicity, solvent-free conditions, good-to-excellent yields for pharmaceutically significant structures, and especially ease of catalyst recovery make this procedure valuable and environmentally benign.