One-step synthesis of inherently chiral p-tert-butylcalix[4]azacrown

A one-step procedure is developed to synthesize inherently chiral p-tert-butylcalix[4]azacrown 1 through etherification between p-tert-butylcalix[4]arene and compound 3, which can be amplified to efficiently prepare more inherently chiral calix[4]arenes in ABHH substitution pattern.     

Facile synthesis and optical resolution of inherently chiral fluorescent calix[4]crowns: enantioselective recognition towards chiral leucinol

A series of tri-O-alkylated inherently chiral fluorescent calix[4]crowns in the cone conformations and a series of tetra-O-alkylated inherently chiral fluorescent calix[4]crowns in the partial cone conformations have been synthesized. By condensing with chiral auxiliary (S)-BINOL, the resulting diastereomers could be separated via preparative TLC. We found that the size of the crown moiety effected the separation of the diastereomers. Further, removal of the BINOL unit by hydrolysis furnished pairs of enantiomers with optical purity. Moreover, we found that a tetra-O-alkylated inherently chiral fluorescent calix[4]crown-6 in the partial cone conformation 6c showed considerable enantioselective recognition capability towards chiral leucinol.     

Proximal heteroalkylation of monoalkoxycalix[4]arenes in synthesis of inherently chiral molecules

Proximal heteroalkylation of monoalkyl ethers of calix[4]arenes or p-tert-butylcalix[4]arenes in NaH/CH₃CN or NaOH/DMSO, respectively, was applied for synthesis of inherently chiral calixarenes with ABHH substitution pattern. The introduction by the method of (R)- or (S)-N-(α-phenylethyl)acetamide chiral auxiliary group gives mixtures of diastereomeric derivatives of inherently chiral calixarenes, which were separated by column chromatography. The chiral calixarenes were thoroughly characterized by ¹H, ¹³C NMR, and X-ray diffraction methods.     

The synthesis of metallocene calix[4]arenes

The condensation of 1,1-bis(chlorocarbonyl)metallocenes andp-tert-butylcalix[4]arene in toluene leads to novel metallocene calix[4]arenes in which the metallocene subunit bridges the opposite hydroxy groups of the parent calixarene.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on cyclodextrins, Lancaster, U.K., 20–25 July 1986.     

Synthesis and structures of novel enantiopure inherently chiral calix[4]arene-derived salphen ligands and their transition-metal complexes

Synthesis and structures of two pairs of novel enantiopure inherently chiral calix[4]arene-derived salphen ligands were described. Several Zn²⁺, Ni²⁺, and Cu²⁺ complexes of the chiral ligands were also prepared, and their structures were characterized by NMR, IR, CD, and HRMS spectra.     

New preorganized calix[4]arenes. Part I. A doubly-crowned calix and a double-calixcrown derived from 4,6,10,12,16,18,22,24,25,26,27,28-Dodecamethyl-5,11,17,23-tetrahydroxycalix[4] arene

A doubly-crowned calix and a double-calixcrown derived from 4,6,10,12,16,18,22,24,25,26,27, 28-dodecamethyl-5,11,17, 23-tetrahydroxycalix[4]arene (1) have been prepared by reaction of appropriate oligoethylene glycol ditosylates with (1) in acetonitrile in the presence of potassium carbonate. A potassium template effect is observed during one of the double cyclizations.     

Inherently chiral calix[4]arene-based bifunctional organocatalysts for enantioselective aldol reactions

Two optical pure m-dimethylamino substituted inherently chiral calix[4]arene derivatives 8a and 8b bearing an l-prolinamido group have been synthesized by two routes, and structurally studied by the usual spectroscopic methods and X-ray crystallographic analysis. It was found that both of 8a and 8b could be utilized as bifunctional organocatalysts to efficiently promote the aldol reactions between aromatic aldehydes and ketones in the presence of acetic acid. Especially, with 8a as the catalyst, the reaction between 4-nitrobenzaldehyde and cyclopentanone at −20 °C gave the anti-aldol product up to 94% ee, while the anti-aldol product in up to 94:6 dr and 79% ee was obtained when 4-cyanobenzaldehyde was used as the aldol donor. Moreover, it was also demonstrated that the inherently chiral calixarene skeleton with (cS)-conformation in 8a was identified as the matched configuration of the stereogenic elements, and the inherently chiral moiety might play an important role in helping to stereocontrol the reaction.     

Synthesis of Macrocyclic Lactones Building on Double Calix[4]arenes

Naturalmacrocycliclactonesandlactamsastheionophoreshaveabsorbedextensiveinterestsbecauseoftheirveryhighselectiverecognitionforalkalimetals.rorexample,nactinslandvalinomycin'havethehighestselectivityforpotassiumamongalltheionopohores.Artificialmacrocycliclactonesalsoshowedselectivityforcanons,althoughthebindingstrengthwaslowerthanthatofcommoncrownethers3.Calixareneswereaveryimportantkindofartificialreceptors,whosederivativeshaveshowedthehighestselectivityforNa ,K andCs amongthesynthesizedmacro…     

Synthesis and Complexing Properties of Four New Tetraamido-type p-tert-Butyl Calix[4]arenes Presenting Two Proximal Binding Subunits

The synthesis of four new tetraamido-type p-tert-butylcalix[4]arenes presenting two proximal binding subunits is reported. Complexation of alkalimetals and zinc picrates with these ligands have been carried out and monitored by ¹H-NMR inCDCl₃. It is shown that hard cations are included in the tetraamido cavity while thezinc cation is chelated to the pyridine rings of one of the ligands. The formation of a 1:1:1heterobinuclear complex is also described     

Synthesis and characterization of an inherently chiral calix[6]arene in the 1,4-alternate conformation

An inherently chiral calix[6]arene possessing a C₂-symmetric A-B-H substitution pattern was synthesized via a two step process starting from the parent hexa-t-butylcalix[6]arene. The racemic, inherently chiral compound exists as a single isomer with the 1,4-alternate conformation. The inherent chirality was confirmed by treatment of the racemic compound with Pirkle’s reagent to form diastereomeric complexes in solution.     

A Facile Method to Synthesize Spiro-calix[4]arenes

Calixarenes have absorbed considerable interests for their outstanding abilities of recognition for cations, anions and organic molecules1. In order to include larger and more complex molecules, polytopic receptors were designed from two or more host macrocycles linked by one or several links. Therefore, double-calixarenes and oligocalixarenes have been synthesized and reviewed2. Among these polytopic receptors, double-calixarenes can be used as the mimic of ion channel or to self-organize koi…     

Synthesis and lead(II) sorption of silica gel-immobilized, di-ionizable calix[4]arenes

Di-ionizable calix[4]arenes with two lower-rim N-(X)sulfonyl carboxamide groups were covalently linked to silica gel via a single attachment on the upper rim. Both the acidity of the ionizable groups (X group variation) and the length of the spacer that joins the ligands to the silica gel matrix were varied. Preliminary evaluation of these new ion-exchange resins for sorption of lead(II) from aqueous solutions was conducted.     

25-Alkoxy-26-benzoyloxycalix[4]arenes: the reaction mechanism of benzoyl migration

In the presence of K₂CO₃ as reaction base, the 25-alkoxy-27-benzoyloxy-calix[4]arenes were converted into 25-alkoxy-26-benzoyloxy derivatives by benzoyl-migration. A benzoyl-migrated reaction mechanism with a cyclic orthobenzoate-like intermediate was proposed, and the mechanism was supported by the identical reaction results on the conversion of 25-ethoxy-27-benzoyloxycalix[4]arene to 25-ethoxy-26-benzoyloxycalix[4]arene, and vice versa.     

Synthesis of New Calix[4]arenes Functionalizated by Acetylhydrazide Groups

A series of new calix[4]phenols, calix[4]resorcinols and calix[4]pyrogallols with acetylhydrazide substitutes has been␣synthesized with high yields by hydrazinolysis of ester group containing calix[4]arenes. The synthesized calix[4]phenols adopt the cone conformation while the calix[4]resorcinol and calix[4]pyrogallol derivatives prefer the boat conformation. The amide fragment of the hydrazide groups predominantly exists in the trans-conformation. The binding ability of synthesized calix[4]arenes toward transition and alkali metals by solvent extraction has been investigated.     

Tetra-CMPO-derivatives of calix[4]arenes fixed in the 1,3-alternate conformation

Calix[4]arene derivatives fixed in the 1,3-alternate conformation and substituted at one side by four carbamoylmethylphosphine oxide (CMPO) residues were synthesised. Two CMPO groups are directly attached to the wide rim, while the second pair is bound to the narrow rim via a tri- or tetramethylene spacer. Similar compounds, in which two CMPO groups at the wide rim are combined with two picolinamide groups or two ionisable carboxylic groups at the narrow rim, were also prepared. Some of these calixarene derivatives were studied as extractants for lanthanides (La³⁺, Eu³⁺, Yb³⁺) and thorium (Th⁴⁺) from acidic solution into methylene chloride. For selected samples, stability constants in methanol were determined by spectrophotometric titrations. Three compounds (1b′, 13, 17) in the 1,3-alternate conformation and one intermediate in the cone conformation (18) were confirmed by a crystal structure.     

Synthesis and evaluation of neutral anion receptors based on acylhydrazide-appended calix[4]arenes

A new class of neutral receptors based upon acylhydrazide-appended calix[4]arenes was synthesised and evaluated for recognition of anions. Detailed NMR and single-crystal X-ray analyses of one of the synthesised compounds reveal that anion recognition in such derivatives is achieved through cooperative hydrogen bond interactions. The presence of three centred NH–O and two OH–O hydrogen bonds at the lower rim of the synthesised calixarene architecture apparently helps the molecular scaffold to retain cone conformation to enable deployment of intermolecular hydrogen bonds for selective recognition of HSO₄ ^? ion in preference to F^?, Cl^?, Br^?, I^?, ClO₄ ^?, AcO^? and PF₆ ^? ions.     

25-[(乙氧基羰基)甲氧基]-26,27,28-三丁氧基对叔丁基杯[4]芳烃的合成

以对叔丁基杯[4]芳烃为起始原料,合成了25-羟基-26,27,28-三丁氧基对叔丁基杯[4]芳烃(2)和25-[(乙氧基羰基)甲氧基]-26,27,28-三丁氧基对叔丁基杯[4]芳烃(3),2和3的结构经1HNMR和IR表征。通过正交实验[L16(45)和L9(33)]优化了实验条件,使3的总收率提高到60%。     

Synthesis of （p-Formylphenyl）azo Calix[4]arenes

Five novel azo calix[4]arenes were reported. The p-aminobenzaldehyde was diazotized with sodium nitrite in aqueous hydrochloride solution. Mono-, bis-, tris- and tetrakis(p-formylphenyl)azo calix[4]arenes (including proximal and distal isomers) were obtained respectively by diazo-coupling in different molar ratio to calix[4]arene(1) under pH=7.5--8.5 at 0-5℃. All (p-formylphenyl)azo calix[4]arenes were characterized by ^1H NMR, ^13C NMR, IR, MS (ESIMS) spectroscopies and elemental analysis.