Solvent-free multicomponent synthesis of 2-arylpyridines using p-sulfonic acid calix[6]arene as a reusable catalyst

An efficient methodology for obtaining 2-arylpyrimidines based on the use of p-sulfonic acid calix[6]arene as an organocatalyst is proposed. The methodology involves the formation of 1,2-dihydropyridine intermediates using a variety of aromatic aldehydes with methyl or ethyl acetoacetate and ammonium acetate, which are the same starting materials as in the Hantzsch reaction, under solvent-free reaction conditions, at 25 °C, followed by air oxidation for 12 h. The catalyst efficiency is not compromised after its successive use in reactions. Eleven examples were obtained with very good to excellent yields of 2-arylpyridines (92–62%). This is the first report about the use of calixarenes as catalysts in the multicomponent synthesis of 2-arylpyridines (molecules with potential biological activity).     

Microwave-assisted multicomponent synthesis of julolidines using silica-supported calix[4]arene as heterogeneous catalyst

The application of immobilizing calixarene onto the surface of silica using a sol-gel method, as an efficient heterogeneous catalyst (CX4SO₃HSi(n)) for multicomponent Povarov reaction has been described. Catalytic activity of the CX4SO₃HSi(n) for the synthesis of julolidines under greener and environmentally benign conditions in simple and efficient method was explored. Notably, only 0.5 mol% of the catalyst is sufficient to catalyze the Povarov solvent-free reaction under microwave-assistance. Besides, this protocol allows the construction of four new C–C bonds and two C–N bonds in a single step. To the best of our knowledge, this consists the first silica support calix[4]arene as a heterogeneous catalyst for multicomponent synthesis of julolidines.     

p-Sulfonic acid calix[n]arenes as homogeneous and recyclable organocatalysts for esterification reactions

Esterification yields were significantly improved using calix[n]arenes catalysts under simple conditions. p-Sulfonic acid calix[4]arene and p-sulfonic acid calix[6]arene were powerful organocatalysts in several esterification reactions, which showed activity comparable or even superior to other well-established acids catalysts, such as, sulfuric acid, p-toluenesulfonic acid, and p-hydroxybezenesulfonic acid described in the literature.     

p-sulfonic acid calix[4]arene: An efficient reusable organocatalyst for the synthesis of bis(indolyl)methanes derivatives in water and under solvent-free conditions

In this work, a green, simple and highly efficient procedure for the synthesis of bis(indolyl)methanes is described. The condensation of indoles catalyzed by p-sulfonic acid calix[4]arene in water and under solvent-free conditions afford the title compounds in high yields and relatively short reaction times.     

Helical aquatubes of calix[4]arene di-methoxycarboxylic acid

Two trimeric units of calix[4]arene di-methoxycarboxylic acid form a six-pointed star architecture that, in turn, generates triple helical aquatubes which intermesh between themselves by aromatic-aromatic interdigitation of the macrocycle.     

Molecular iodine: An efficient and environment-friendly catalyst for the synthesis of calix[4]resorcinarenes

Iodine catalyzes the cyclocondensation of various aldehydes with resorcinol to give tetrameric cyclic products, resorcinarenes. Through the reaction of resorcinol with aromatic aldehydes, the product is obtained as a mixture of two isomers, the all-cis isomer (rccc) and the cis-trans-trans isomer (rctt), whereas a single diastereomer, the all-cis, is formed with aliphatic aldehydes. Besides excellent isolated yields, the use of iodine makes this procedure simple, convenient, cost-effective and practical.     

Supramolecular interaction between water-soluble calix[4]arene and ATP--the catalysis of calix[4]arene for hydrolysis of ATP

The catalysis effect of water-soluble calix[4]arene C[4] (calix[4]arene-5,11,17,23-tetrasulfonate) on hydrolysis of ATP in aqueous solution was studied by HPLC. Using laser photolysis and pulse radiolysis, the supramolecular interaction between water-soluble calix[4]arene and ATP was investigated.     

Proline-functionalised calix[4]arene: an anion-triggered hydrogelator

A water-soluble, chiral calix[4]arene has been found to form hydrogels when triggered by the presence of specific anions, with efficacy linked to the Hofmeister series; the gel properties are modified by the associated cations, and gelation can be reversibly switched off by increasing pH.     

Solid-phase synthesis of linear and cyclic peptides containing a calix[4]arene amino acid

Solid-phase synthesis is used to obtain new linear and cyclic N,C-linked peptidocalixarenes. The synthetic strategy allows, for the first time, the condensation of a calix[4]arene amino acid during the stepwise elongation sequence of the peptide. An important role is played by the lower rim functionalization of the calixarene since it modulates the flexibility of the calixarene scaffold and the conformational properties of the resulting non-natural peptide.     

Silver(I) N-heterocyclic carbene-bridged calix[4]arene analogues as efficient [60]fullerene receptors

Two silver(I) N-heterocyclic carbene-bridged calix[4]arene analogues 4 and 5 were synthesized by a fragment-coupling approach; the preliminary inclusion properties of 5 with [60]fullerene shows that it is a novel efficient [60]fullerene fluorescent sensor.     

Catalytic investigations of calix[4]arene scaffold based phase transfer catalyst

Calix[4]arene scaffold based quaternary ammonium salts as multi-site phase transfer catalysts were prepared and their catalytic activities were investigated for Darzens condensation, O/N-alkylation reactions and ethyl benzene oxidation. These calix[4]arene based multi-site phase transfer catalysts showed significant high catalytic activity as compared to single-site phase transfer catalysts.     

Chromogenic calix[4]arene as ionophore for potentiometric and optical sensors

Chromogenic calix[4]arene derivative was synthesized and tested as an ionophore for potentiometric and optical sensors. Distinct sodium selectivity was observed with this ionophore based, plasticized PVC membranes in potentiometric measurements suggesting their utility for biological applications. Optode membranes exhibited sodium sensitivity in the 5 x 10(-2) -10(-4)M concentration range. The optical sensitivity was improved by the use of an internal, lipophilic base (TDDA). The operation of the optical sensor is in accordance with the ion-exchange theory.     

l-proline as an efficient asymmetric induction catalyst in the synthesis of chromeno[2,3-d]pyrimidine-triones,xanthenes in water

The multi-component reactions involving aromatic aldehydes, dimethylcyclohexane-1, 3-dione/cyclohexane-1, 3-dione and barbituric acids were carried out in presence of the organo catalyst l-proline in aqueous medium at ambient temperature. The reactions afforded chromeno[2,3-d]pyrimidinones in excellent yields and with high enantioselectivities. The above reactions exhibited the efficient asymmetric induction property of the organo catalyst l-proline as reported earlier. In the absence of barbituric acid the method proved equally efficient when aromatic aldehydes readily condensed with 2 mol of cyclohexane-1, 3-dione in presence of l-proline to give Xanthenes derivatives in good yields. The protocol reported here is benign to the environment as water is used as the solvent and purification does not involve any chromatographic procedures. Selected compounds were further studied using DFT calculations in order to establish a clear picture about the geometric parameters and the electronic absorption spectra of the compounds.     

An efficient and eco-friendly synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes using H4[SiW12O40] as a heterogeneous and reusable catalyst under solvent-free conditions

A simple and efficient catalytic protocol for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes via the one-pot condensation ofβ-naphthol and aryl aldehydes using silicotungstic acid(H₄[SiW₁₂O₄₀]) is reported.The present method offers several advantages such as high to excellent yields,short reaction times,recovery and reusability of catalyst,mild reaction conditions and easy workup procedures.     

Controlled solvothermal synthesis of PbS quasi-nanorods by calix[4]arene

A new idea of the nanorods preparation and a novel application of calixarenes are presented. Calix[4]arene was introduced into solvothermal system to produce one-dimensional inorganic nanomaterial. The obtained product was characterized by XRD and TEM. Results of the XRD analysis showed that the product was pure cubic phase of PbS with high crystallinity. TEM images revealed that the diameter and length of the PbS nanorods were about 200 nm and up to 3.5 μm, respectively. Optical properties of the product were also studied. PL emission image showed that the product exhibited an emission peak at 308 nm in ultraviolet region showing a blue shift of 14 nm compared to the bulk material. The formation mechanism of PbS nanorods in the presence of calix[4]arene is discussed.     

Aminolysis reaction of calix [ 4 ] arene esters and crystal structures and conformational behaviors of calix[4]arene amides

We first make use of aminolysis of calix[4]arene esters to synthesize calix[4]arene amides. When the two ethyl esters of the calix[4]arene esters are aminolysized, the 1, 3-amide derivative is formed selectively. The crystal structures of the calix-[4]arene with two butyl amide (3b) and four butyl amide moieties (4b) were determined. The intermolecular hydrogen bonds make 4b form two-dimensional net work insolid state. The 1H NMR spectra prove that 3b is of a pinched cone conformation, while 4b and tetraheptylamide-calix[4]arene (6b) take fast interconversion between two C2v isomers in solution and appear an apparent cone conformation at room temperature. As decreasing temperature, the interconversion rate decreases gradually and, finally, the interconversion process is frozen at Tc = -10℃, which makes both conformations of 4b and 6b the pinched cone structures. The hydrogen bond improves the interconversion barrier, and the large different values of the potential barrier between 6b and 4b (or 6b) may     

杯芳烃衍生物的合成和性质的研究5

通过对特丁基杯(4)芳烃的酚羟基的选择性醚化制备了一系列一烃基,1,3-二烃基和四烃基醚,烃基分别含有缩醛、酰胺、氰基等活泼官能团。醚化反应的区域选择性主要取于使用的碱的种类和反应时间的长短。     

The synthesis and characterization of calix[4]arene based azo dyes

A series of azocalix[4]arene dyes (1–7) were prepared by linking 2,4-di-chloroaniline, 2,4,5-tri-chloroaniline, 2,4-di-nitroaniline, 2-nitro p-toluidin, 4-nitro o-toluidin, 5-nitro o-toluidin and sulfanilic acid, to calix[4]arene through a diazo-coupling reaction. These compounds were characterized by elemental analysis, FT-IR, ¹H NMR, ¹³C NMR, MALDI-TOF, UV–Vis., DSC, and DTA. The absorption properties of the synthesized dyes were studied and the application of the water soluble dye on cotton and wool was discussed. Solvent based inks were investigated and the fastness properties of formulated inks were also discussed.     

Synthesis of a novel fluorescent anthryl calix[4]arene as picric acid sensor

A novel and sensitive fluorescence sensor has been designed by click chemistry. Based on the obvious and selective fluorescence quenching of anthryl calix[4]arene, a sensitive and robust platform were developed for visual detection of picric acid (TNP) in the mixture of nitro aromatics. The computational calculations revealed the formation of host–guest complex driven by π–π stacking interactions.