Arene Analogues Research Articles

Comparative study of calix[4]arene derivatives: implications for ligand design

The first comparative theoretical study of three parent calix[4]arene analogues (calix[4]arene, thiacalix[4]arene, and homooxacalix[4]arene) has been performed using molecular dynamic simulations and density functional theory (MPWB1K/6-311G ∗∗//B3LYP/6-311G ∗∗) methods. The theoretical observations herein including optimized geometry, polarity, and atomic charge data provide that homooxacalix[4]arene would offer more efficient platform for metal ion recognition compared to thiacalix[4]arene or calix[4]arene.

Efficient Post-Macrocyclization Functionalizations of Oxacalix[2]arene[2]pyrimidines

Diversely functionalized oxacalix[2]arene[2]pyrimidines have been synthesized starting from a bis(methylsulfanyl)-substituted oxacalix[4]arene by two efficient post-macrocyclization pathways. Functionalized aryl groups were introduced on the pyrimidine building block via Liebeskind-Srogl cross-coupling reactions, while a variety of O-, S-, N-, and C-nucleophiles were inserted on the calixarene skeleton by nucleophilic aromatic substitution reactions on the bis(methylsulfonyl)oxacalix[4]arene analogue.

Topological Polymerization of tert-Butylcalix[4]arenes Containing Diynes

The new 25,26,27,28-tetra(8-hydroxylocta-2,4-diynyl)-tert-butylcalix[4]arene was synthesized in good yield from copper-catalyzed coupling reaction of 25,26,27,28-tetra(2-propynyl)-tert-butylcalix[4]arene with 5-iodo-4-pentynol in pyrrolidine. The hydroxyl end groups were converted to urethane groups through addition to alkyl or phenyl isocyanate. Di- and trisubstituted tert-butylcalix[4]arene analogs were also synthesized through the same approach. The solid-state photopolymerization study revealed that only the calix[4]arene derivatives containing four diyne units with alkyl urethane groups were substantially polymerized upon exposure to UV or gamma irradiation to give polydiacetylenes containing calix[4]arene. The visible absorption band at 350−600 nm and the Raman signals around 1500 and 2100 cm-1 characterized the ene−yne conjugation formed through the topological 1,4-addition polymerization of the diyne units.

Silver(I) N‐Heterocyclic Carbene‐Bridged Calix[4]arene Analogues as Efficient [60]Fullerene Receptors

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

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 Diastereoselective Polycyclization of Homo(polyprenyl)arene Analogues Bearing Terminal Siloxyvinyl Groups

Highly diastereoselective polycyclization of homo(polyprenyl)arene analogues bearing terminal siloxyvinyl groups was catalyzed by tin(IV) chloride (10 mol %). The cyclizations of tert-butyldiphenylsilyl and triisopropylsilyl polyenol ethers gave 4alpha(equatorial)- and 4beta(axial)-siloxypolycycles as major isomers, respectively. The strong nucleophilicity of pro-C(9), a (6E) geometry, and a bulky silyl group effectively favored the alpha-preference, whereas the weak nucleophilicity of pro-C(9), a (6Z)-geometry, and less steric hindrance of a silyl group favored the beta-preference. [reaction: see text].

Syntheses and Coordination Properties of (Thia)Calix[4]Arenes Bearing Single ω-Quinolin-8-Yl-Oligooxyethylene Pendant

Four mono-quinolin-8-yl-substituted (thia)calix[4]arenes via oligooxyethylene spacers (1a–b and 2a–b) were synthesised conveniently in one step. Their structures and conformations were characterised by 1H NMR and ESI-MS spectra. Their coordination properties were studied by fluorescence spectra titration in CH3CN. All of them can form stable 1:1 complex with Zn(II) and Mg(II) ions, respectively. The stability constants of thiacalix[4]arene (2a and 2b) derivatives are higher than those of the calix[4]arene analog (1a and 1b).

Extended Calix[4]arene Analogues by Two P−CuI−P Bridges and Anion Encapsulation

Two novel extended calix[4]arene analogues by two P-Cu(I)-P bridges have been synthesized. The molecular structures and anion encapsulation ability for ClO4- and BF4- have been studied by X-ray analysis.

Approaches to polymetallated calixarene derivatives

Tetrabrominated calix[4]arene analogue 4 was subjected to lithium-halogen exchange with tertbutyl lithium to give a tetra-lithium salt which could be silylated with chlorotrimethylsilane to give tetrasilylated derivative 5 and the trisilylated analogue 6. However, attempts to use boron electrophiles resulted in only partial boronation. Attempts to brominate calix[6]arene 12 proved surprisingly difficult, which prevented the isolation of 13 and hence generation of the corresponding hexa-lithium salt. Bromination of calix[8]arene 14b was possible and the octalithium salt was generated by lithium-halogen exchange of 15 with tert-butyl lithium. Subsequent reaction with chlorotrimethylsilane though, only resulted in partial silylation to give 16.

Synthesis of cesium selective pyridyl azocalix[ n]arenes

A series of pyridylazo calix[ n]arenes ( n=4, 6, 8) including the first examples of mixed hetroaryl azocalix( n)arenes have been synthesized by coupling calix[ n]arenes with diazonium salts derived from amino pyridines. It has been observed that the coupling reaction of diazonium salt obtained from 3-aminopyridine with calix[ n]arene gives tetrakis-, hexakis- and octakis (pyridylazo)calix[ n]arenes ( n=4,6,8) while those derived from 4-aminopyridine give partially substituted (4-pyridylazo)calix[ n]arene analogs. There is no reaction of calix( n)arenes with diazonium salts derived from 2-aminopyridine under identical conditions of experiments. The conformational analysis of synthesized compounds have been ascertained by detailed spectral measurements and single crystal X-ray analysis of 5-(3′-pyridylazo)-25,26,27,28-tetrahydroxycalix[4]arene. A rational explanation for the observed partial and exhaustive coupling reaction in the synthesis of heteroaryl azocalix( n)arenes has been suggested. Preliminary evaluation of synthesized derivatives as molecular receptors for metal ions indicates that they have good potential to function as selective ionic filters for cesium ions.

Conformational Control of Calix[6]arenes Through Multiple Bridges

AbstractThe synthesis of the A,D‐m‐xylylene‐bridged B,C,E,F‐tetra‐O‐alkylcalix[6]arenes 1b–c and the A,D‐B,C;E,F‐triply bridged calix[6]arenes 2a–c is described. The cone conformation of the new bridged calix[6]arenes has been established by a full set of 1D/2D 1H and 13C NMR techniques. These compounds are substantially more rigid than calix[6]arene analogues with an A,D‐p‐xylylene bridge, and the resulting cavities are better defined. Molecular mechanics optimization of triply bridged calix[6]arenes 2b and 2c resulted in structures fully consistent with the NMR spectra. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Chemistry and Dynamics of Interaction of Nucleosides with Pentafluoropyridine

Interaction of pentafluoropyridine with hydroxyl groups of thymidine, uridine, adenosine, and deoxyadenosine at room temperature leads to the formation of aryl ethers of nucleosides with a high yield. Under severe conditions, one more tetrafluoropyridine residue is attached to pyrimidine fragments of T and U, while purine heterocycle in A remains intact. Nucleoside derivatives are formed with a quantitative yield and can be used in situ as intermediates for, as an example, molecular design of arene analogs of nucleic acids. The reaction with thymidine is a successive-parallel process, the limited stage being arylation of the secondary hydroxyl group. The presence of the vicinal hydroxyl group in pentose results in the opposite rate ratio of the formation of primary and secondary tetrafluoropyridyl ethers of adenine and uridine.

Chemical and Electrochemical Reduction of Polyarene Manganese Tricarbonyl Cations: Hapticity Changes and Generation of Syn- and Anti-Facial Bimetallic η4,η6-Naphthalene Complexes

(Eta6-naphthalene)Mn(CO)(3)(+) is reduced reversibly by two electrons in CH(2)Cl(2) to afford (eta4-naphthalene)Mn(CO)(3)(-). The chemical and electrochemical reductions of this and analogous complexes containing polycyclic aromatic hydrocarbons (PAH) coordinated to Mn(CO)(3)(+) indicate that the second electron addition is thermodynamically easier but kinetically slower than the first addition. Density functional theory calculations suggest that most of the bending or folding of the naphthalene ring that accompanies the eta6 --> eta4 hapticity change occurs when the second electron is added. As an alternative to further reduction, the 19-electron radicals (eta6-PAH)Mn(CO)(3) can undergo catalytic CO substitution when phosphite nucleophiles are present. Chemical reduction of (eta6-naphthalene)Mn(CO)(3)(+) and analogues with one equivalent of cobaltocene affords a syn-facial bimetallic complex (eta4,eta6-naphthalene)Mn(2)(CO)(5), which contains a Mn-Mn bond. Catalytic oxidative activation under CO reversibly converts this complex to the zwitterionic syn-facial bimetallic (eta4,eta6-naphthalene)Mn(2)(CO)(6), in which the Mn-Mn bond is cleaved and the naphthalene ring is bent by 45 degrees . Controlled reduction experiments at variable temperatures indicate that the bimetallic (eta4,eta6-naphthalene)Mn(2)(CO)(5) originates from the reaction of (eta4-naphthalene)Mn(CO)(3)(-) acting as a nucleophile to displace the arene from (eta6-naphthalene)Mn(CO)(3)(+). Heteronuclear syn-facial and anti-facial bimetallics are formed by the reduction of mixtures of (eta6-naphthalene)Mn(CO)(3)(+) and other complexes containing a fused polycyclic ring, e.g., (eta5-indenyl)Fe(CO)(3)(+) and (eta6-naphthalene)FeCp(+). The great ease with which naphthalene-type manganese tricarbonyl complexes undergo an eta6 --> eta4 hapticity change is the basis for the formation of both the homo- and heteronuclear bimetallics, for the observed two-electron reduction, and for the far greater reactivity of (eta6-PAH)Mn(CO)(3)(+) complexes in comparison to monocyclic arene analogues.

Stepwise Cross-Couplings of a Dibromo-γ-methylenebutenolide as an Access to Z-Configured α-Alkenyl-γ-alkylidenebutenolides. Straightforward ­Synthesis of the Antibiotic Lissoclinolide

The Z-isomer of a-bromo-y-(bromomethylene)butenolide was prepared from α-angelica lactone or levulinic acid in three and four steps, respectively. Successive Stille-couplings with an unsaturated stannane, with the potential to use a different second unsaturated stannane, involved the γ-substituent first and the α-substituent thereafter. Thereby, a-alkenyl-y-alkylidenebutenolides and their arene analogs were obtained Z-selectively.

Do pentaurea calix[5]arenes form hydrogen bonded dimeric capsules?

Calix[5]arenes substituted at their wider rim by five urea residues do not form hydrogen bonded dimeric capsules in aprotic, apolar solvents, in contrast to their calix[4]arene analogs, although molecular dynamic simulations predict very similar geometrical parameters for both cases. The reason for this different behavior is most probably the higher energetic cost which must be paid to arrange the calix[5]arene skeleton in the C5-symmetrical conformation required for the dimerization.

Chiral Calix[4]arenes

AbstractFor Abstract see ChemInform Abstract in Full Text.

キラルカリックス［４］アレーン

syn-Dihydroxymetacyclophanes were converted to bridged calix [4] arene analogs by base-cat-alyzed condensation with formaldehyde. A remarkable template effect was observed on this condensation. Enlarged calix [4] arene analogs were synthesized by two different methods. All calix [4] arene analogs took the cone-type conformation and kept it even at high temperatures. From them, the unique chiral calixarenes were successfully synthesized by the following two methods : one is Williamson ether synthesis and the other is a stepwise ether cleavage with a mild Lewis acid. The high regioselectivity is recognized by the latter stepwise method. Also from them, the ionophores having oligoethylene glycol unit were obtained, which efficiently extracted larger alkali metal ions like K+, Rb+, and Cs+ than smaller ones like Li+ and Na+. Their ion selectivity apparently changed by the chain length of crown ether. All racemates obtained were resolved by the chiral HPLC column. The planar chiral calixarenes recognized the chirality of guest molecules. Thus, the (-) -receptor resolved strongly forms 1 : 1 complex with (R) - (+) - α-phenylethylammonium picrate.

Synthesis and Characterization of Chiral Calixarene Analogs Locked in the Cone Conformation by the Photocycloaddition

A bisphenol derivative was used as the starting material. [2+2] Photocycloaddition of tetraolefin gave the desired calix[4]arene analogs having chiral and achiral structure in 12-77% yields. The optical resolution was successfully achieved by using the HPLC method. The calixarene analog formed a 1:1 complex with alkali metal ions and extracted large metal picrates better than small ones.

Non-covalent calixarene–amino acid complexes formed by MALDI-MS

Non-covalent inclusion complexes formed between amino acids and derivatized calix[6]arenes are observed in MALDI mass spectrometry. The methyl, ethyl, and propyl ester derivatives of calix[6]arene yielded amino acid complexes, while the smaller calix[4]arene analogs did not. Similarly the underivatized calix[6]arene and calix[4]arene did not produce complexes. Amino acid complexes were observed for nearly all 20 amino acids in time-of-flight (TOF) analysis. In Fourier transform mass spectrometry (FTMS) analysis, however, only the most basic amino acids arginine, histidine, and lysine formed stable adducts. The complexes were abundant under matrix-assisted laser desorption ionization (MALDI) conditions, which suggested favorable interactions between host and guest.

ChemInform Abstract: Facile Formation of Calix[4,5,6, and 9]arene Analogues Having the intra‐ and extra‐Hydroxyl Groups.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.