Synthesis and cationic selectivity studies of novel calix[4]arene derivatives containing heteroatom at the lower rim

A series of calixarene derivatives 2―5 containing heteroatom at the lower rim have been synthesized. 1H NMR studies and crystallographic structures demonstrated that the calix[4]arene derivatives adopted cone conformations. Their cationic binding abilities and selectivities towards heavy and tran- sition metal ions have been evaluated by solvent extraction of aqueous metal picrates. The obtained results indicated that the introduction of nitrogen, sulfur, and/or phosphor atoms to the calix[4]arene framework could effectively enhance their binding ability and selectivity for heavy and transition metal ions, such as Pb2 or Ag .     

Design of the novel calix[n]BODIPY molecules (n = 4–8): TDDFT and AIM study

Journal of Inclusion Phenomena and Macrocyclic Chemistry - In this study, based on BODIPY molecule, new calix-like structures with significant electrical and optical properties were designed. These...     

Synthesis and characterisation of a calix[4]pyrrole functional polystyrene via ‘click chemistry’ and its use in the extraction of halide anion salts

A polystyrene with pendant calix[4]pyrroles was prepared via ‘click reaction’ strategy. First, a poly(styrene-co-chloromethylstyrene) with approximately 12% of chloro groups was prepared by conventional free radical polymerisation. The chloro groups were then converted to azido groups using NaN₃ in N,N-dimethylformamide. An alkyne-functionalised calix[4]pyrrole was then coupled to the azido-functionalised polystyrene by click chemistry with high efficiency. The resulting polystyrene with pendant calix[4]pyrroles was used to extract fluoride and chloride anions (as their tetrabutylammonium salts) from their aqueous solutions to organic media.     

Experimental and Theoretical Structure Elucidation of the [2 : 1] Complex Ion of Carbo[n]helicene with n=6, 7 and 8 and Ag+

Gas-phase complexes of [n]helicenes with n=6, 7 and 8 and the silver(I) cation are generated utilizing electrospray ionization mass spectrometry (ESI-MS). Besides the well-established [1 : 1] helicene/Ag⁺-complex in which the helicene provides a tweezer-like surrounding for the Ag⁺, there is also a [2 : 1] complex formed. Density functional theory (DFT) calculations in conjunction with energy-resolved collision-induced dissociation (ER-CID) experiments reveal that the second helicene attaches via π-π stacking to the first helicene, which is part of the pre-formed [1 : 1] tweezer complex with Ag⁺. For polycyclic aromatic hydrocarbons (PAHs) of planar structure, the [2 : 1] complex with silver(I) is typically structured as an Ag⁺-bound dimer in which the Ag⁺ would bind to both PAHs as the central metal ion (PAH–Ag⁺–PAH). For helicenes, the Ag⁺-bound dimer is of similar thermochemical stability as the π-π stacked dimer, however, it is kinetically inaccessible. Coronene (Cor) is investigated in comparison to the helicenes as an essentially planar PAH. In analogy to the π-π stacked dimer of the helicenes, the Cor−Ag⁺−Cor−Cor complex is also observed. Competition experiments using [n]helicene mixtures reveal that the tweezer complexes of Ag⁺ are preferably formed with the larger helicenes, with n=6 being entirely ignored as the host for Ag⁺ in the presence of n=7 or 8.     

Structural and metallo selectivity in the assembly of [2 × 2] grid-type metallosupramolecular species: mechanisms and kinetic control

An unsymmetrical bis(tridentate) ligand LH in which one binding site can be readily deprotonated forms a kinetically inert [Co(III)L(2)](+) complex which can be used as a "corner" species for the "Coupe du Roi" assembly of trans,trans-[Co(2)M(2)L(4)](6+) metallogrids (M = Fe(II), Co(II), Cu(II), Zn(II)). In the mixed Co(III)/Co(II) species, the oxidation states appear to be localised. In solution, the ligand LH forms octacationic, homometallic [2 × 2] grids with the individual labile metal ions Fe(II), Co(II), Cu(II), Zn(II), seemingly as mixtures of all possible isomers arising from the unsymmetrical nature of the ligand. In the solid state, however, [Zn(4)L(4)](CF(3)SO(3))(8)·4CH(3)CN crystallises as a single species where the cation has S(4) symmetry. This stereoselectivity in the crystalline lattice is associated with interactions between the cation and triflate anions which can again be analysed in terms of the Coupe du Roi concept.     

Complexes of TETROL with selected heterocyclics: unconventional host–guest hydrogen bonding and the correlation with host selectivity

Here we investigate and compare the more salient characteristics of host–guest complexes of (+)-(2R,3R)-1,1-4,4-tetraphenylbutane-1,2,3,4-tetraol (TETROL) with four heterocyclic guests, morpholine, piperidine, pyridine and dioxane. These guests each formed inclusion compounds with TETROL, and host:guest ratios were either 1:2 or 1:1. Single crystal diffraction experiments revealed unprecedented host behaviour in the presence of both piperidine and dioxane with respect to the mode of host–guest hydrogen bonding employed. Furthermore, by utilizing ¹H-NMR spectroscopy or gas chromatography (as applicable) as methods for analysing complexes obtained from competition experiments, we were able to identify the host selectivity order, and were gratified to discover that this order correlated precisely with host–guest hydrogen bond distance.     

Theoretical investigation of the complexation,structural, and electronic properties of complexes between oseltamivir drug and cucurbit[n = 6–9]urils

Structural Chemistry - The structural geometries of cucurbit[n]uril CB[n] with n?=?6–9 and their complexes with oseltamivir (OST) drug were obtained using the density...     

Novel redox receptors for ion-pair and α-amino acid: synthesis and complexation properties of calix[4]arene derivatives bearing large conjugated ferrocene groups

By reacting calix[4]arene 1,3-bi-hydrazide derivative (2) with formacylferrocene in “1?+?2” condensation mode, novel calix[4]arene derivative bearing two conjugated ferrocene groups (3) was obtained in yield of 88%. By reacting 1,3-bi-substituted [2-(p-formylphenyloxy)ethyloxy]-p-tert-butylcalix[4]arene (5) with 1,1′-diacetylferrocene hydrazone (4) in “1?+?1” condensation mode, novel calix[4]arene derivative with 1,3-substituted large conjugated ferrocene bridge (6) was synthesized in yield of 83%. The structures and conformations of new compounds were confirmed by elemental analyses, IR spectra, ESI-MS, ¹H NMR, etc. The electrochemical cyclic voltammetry experiments revealed that compounds 3 and 6 possessed excellent reversible electrochemical properties. The ¹H NMR titration study showed that compound 6 possessed excellent complexation abilities for NaH₂PO₄ and glycine in 1:1 host–guest complex with the association constants of 3,850 and 2,460?M^?1, respectively.     

Silphos [PCl3− n (SiO2) n ]: A Heterogeneous Phosphine Reagent for the Regioselective Synthesis of vic-Haloalcohols

Silphos as a silica-based phosphine [PCl_3?n (SiO₂) _n ] provides a practical method for the conversion of epoxides to vic-haloalcohols in the presence of molecular bromine, iodine, or N-halosuccinimides (NXS, X = Cl, Br, I) in CH₃CN or under solvent-free conditions at r.t. The simple filtration of heterogeneous Silphos oxide from the reaction mixture affords the pure vic-haloalcohols with excellent yields.     

On general forms for structure of some [n−1, 1] ⊗ [λ]L n n inner tensor products with 6 ≤n≤ 20, (60) forn even,in the context of spin cluster problems of multiquantum NMR

Consideration ofL _n groups for n even and between 6 n: 20, (60) is consistent with the existence (over a simply reducible (SR) space) of certain similarities in the inner tensor product (ITP) structures associated with -p 2 [n -1, 1] [.], or - [(n/2)²] products, and for general (even)n for [n -1, 1] [n - 2, 1²] ITPs, but not for ITPs involving higher generalm (p 3) components, as in [n-1, 1] [n-m, m-1, 1].These observations provide considerable insight into the nature of van der Waals (3 n 20), metallic-, or met-carb- clusters andn = 12, 20 cage molecules analogous to dodecahedrane (a cage,n = 20 molecule) or¹³C buckminsterfullerene(ane) (n = 60) [A] _n , [AX] _n clusters, besides allowing for further combinatorial views on higherL _n group characters and their associated group algebra. Mathematical insight to date into the nature of general ITPs involvingnon-SR direct sums has proved less fruitful on account of the number of component partitions spanned by specific TTP maps and their associated multiplicities.     

Synthesis of bridgehead-substituted azabicyclo[2.2.1]heptane and -[3.3.1]nonane derivatives for the elaboration of α7 nicotinic ligands

Azabicyclo[2.2.1]heptane and -[3.3.1]nonane scaffolds (X = Cl, Br) containing a pyridinyl substituent at the bridgehead position were prepared via two complementary chemical pathways, either by the transformation of a methoxy group into a synthetically valuable chlorine atom at the C-6 position of the pyridine moiety or by means of a regioselective C-6 deprotonation/halogenation process of the pyridine moiety exemplified by chlorination or bromination. These newly generated scaffolds were then engaged in Suzuki-Miyaura coupling reactions to provide α7 nicotinic ligands. Both chemical series were evaluated in vitro for their affinity at α7 nicotinic receptors, revealing nanomolar potency with significant selectivity over the α4β2 nicotinic subtype. These approaches offer a general access to these α7 nicotinic scaffolds and ligands.     

Pyridazines,LIV: On the synthesis of pyridazine-fused S-heterocycles: Thieno[2,3-c]pyridazine,pyrimido[4′,5′:4,5]thieno[2,3-c]pyridazine,and pyridazino[3,4-b][1,4]benzothiazine

Summary Starting from 3-chloro-4-pyridazinecarbonitrile (1), the thienopyridazine derivatives2 and3 were prepared. Condensation of3 with triethyl orthoformate afforded the novel tricyclic system4. Reaction of1 with 2-aminothiophenol, followed by treatment with NaH/DMSO was found to give the diaza-phenothiazine6 instead of the expected condensed thiazepine.Dedicated with best wishes to Prof. Dr. G. Zigeuner on the occasion of his 70^th anniversary     

On the validity of the correlation – Belda equation for some physical and chemical properties in 1,4-dioxane + water mixtures

Knowledge and prediction of physicochemical properties of binary mixtures is of great importance in understanding intermolecular interactions. The literature shows that most such systems exhibit non-linear behaviour. In this frame, a correlating equation was recently proposed by Belda and tested with success on 50 binary systems for density, viscosity, surface tension and refractive index. In order to assess the validity of the proposed equation, it has been applied to 1,4-dioxane + water mixtures at 298.15?K for nine physicochemical properties. These mixtures exhibit strong interactions. The results were fitted and compared with the Redlich–Kister (R–K) equation of the same number of parameters. The equation seems to offer better results for some properties than those of R–K with two free parameters.     

Selective complexation of UO 2 2+ by the calix[6]arene6− anion: Structure and hydration studied by molecular dynamics simulations

Based on molecular dynamics simulations, we describe the structure and solvation pattern of thep-Me-calix[6]arene^6– anion in the free state, and complexed with UO ₂ ²⁺ in aqueous solution. UO ₂ ²⁺ is coordinated in its equatorial plane to five phenolate oxygens, and has no direct coordination with water molecules. The closest water molecules are strongly hydrogen bonded to the ligand. The complex of thep-Me-calix[5]arene^5– anion with UO ₂ ²⁺ displays similar binding and solvation features. For the purpose of comparison, a complex ofp-Me-calix[6]arene^6– with a spherical divalent cation, referred to as Cu²⁺ is simulated under the same conditions. In the most stable conformer, Cu²⁺ is coordinated to four phenolic oxygens in a square planar arrangement, and to one water molecule. An energy component analysis suggests that the high binding selectivity of the calixarene for uranyl relates to a large cation-guest interaction, and to a better hydration of the complex. In the UO ₂ ²⁺ complex the strong hydration of the negatively charged ligand is not significantly prevented by the complexed cation, unlike in the spherical cation complexes. It is stressed that entropic effects, which are not amenable to such calculations, play an important role in the binding selectivity of these calix[6] and calix[5]arenes for uranyl.     

Using magnetized water as a solvent for a green,catalyst-free,and efficient protocol for the synthesis of pyrano[2,3-c]pyrazoles and pyrano[4′,3′:5,6]pyrazolo [2,3-d]pyrimidines

Research on Chemical Intermediates - A facile, eco-friendly, and highly efficient one-pot four-component protocol is demonstrated for the synthesis of the pyrano[2,3-c]pyrazole and...     

Preparation and characterization of MNPs–PhSO3H as a heterogeneous catalyst for the synthesis of benzo[b]pyran and pyrano[3,2-c]chromenes

Research on Chemical Intermediates - In this study, an efficient and novel procedure has been reported for loading sulfanilic acid on the surface of magnetite Fe3O4 nanoparticles using...     

K7[PW11CoO40]: Efficient and Ecofriendly Catalyst for the Enamination of β-Dicarbonyl Compounds

Condensation of a variety of β-dicarbonyl compounds with primary and secondary amines carried out in the presence of catalytic amounts of K₇[PW₁₁CoO₄₀]. From this reaction N-substituted β-enamino esters and ketones were obtained in high yields.     

A new method for the formation of the imidazo[4′, 5′; 3,4] pyrido[2,3-b]indole ring: Formal synthesis of the alkaloids from marine origin grossularines-1 and 2

A new synthesis of the 2-dimethylamino-4-hydroxy-6-methoxymethyl-3H-imidazo[4′, 5′:3,4] pyrido[2,3-b]indole, used as key intermediate in the total synthesis of the alkaloids grossularines-1 and -2, based on the step-wise formation of the pyridine and imidazole rings, is described.     

DBU as a scaffold for the synthesis of [1,3]oxazolo[2’,3’ : 2,3]pyrimido-[1,2-a]azepines: annulation with aromatic cyanopropargylic alcohols

1. Download high-res image (80KB)
2. Download full-size image