Enhanced hydrodeoxygenation of lignin-derived anisole to arenes catalyzed by Mn-doped Cu/Al_(2)O_(3)

Lignin is a renewable carbon resource to produce arenes due to its abundant aromatic structures.For the liquid-phase hydrodeoxygenation(HDO)based on metallic catalysts,the preservation of aromatic rings in lignin or its derivatives remains a challenge.Herein,we synthesized Mndoped Cu/Al_(2)O_(3) catalysts from layered double hydroxides(LDHs)for liquid-phase HDO of lignin-derived anisole.Mn doping significantly enhanced the selective deoxygenation of anisole to arenes and inhibited the saturated hydrogenation on Cu/Al_(2)O_(3).With Mn doping increasing,the surface of Cu particles was modified with MnO_(x) along with enhanced generation of oxygen vacancies(Ov).The evolution of active sites structure led to a controllable adsorption geometry of anisole,which was beneficial for increasing arenes selectivity.As a result,the arenes selectivity obtained on 4Cu/8Mn4AlO_(x) was increased to be more than 6 folds of that value on 4Cu/4Al_(2)O_(3) over the synergistic sites between metal Cu and Ov generated on MnO_(x).

BF₃.OEt₂-Mediated Benzylation of Arenes and Heteroarenes with Benzyl Ether Derivatives

An efficient BF3.OEt2-promoted benzylation of arenes and heteroarenes with various benzyl ether derivatives has been developed. This method provided alternative access to valuable diarylmethane in good yields under mild conditions via an easy work-up procedure.

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

The macrocyclic lactones building on calix[4]arenes 3a-b and double calix[4]arenes 4a- h were synthesized by the reaction of p-tert-butylcalix[4]arene (1a) or calixl41arene (1b) with glycol bis(2-chloroacetate) (2). The conditions to improve the yields of double calix[4]arenes have been discussed.

Synthesis of Calix[4]arenes with Dendritic Fragments

The 1,3-distally selective functionalization of calix[4]arenes with benzylicbromides at the lower rim in excellent ytelds is described. The calix[4]arenes withdendritic fragnents obtalned exist in cone conformation.

STUDIES ON CALIXARENES I THE CNDO／2 CALCULATION OF EQUILIBRIUM MOLECULAR GEOMETRY OF CALIX［4］ARENE I

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

The spiro-calix[4]arenes 3a-b can be synthesized conveniently by the reaction of p-tert-butylcalix[4]arene (1a) or calix[4]arene (1b) with pentaerythritol tetrakis(2-chloroacetate) (2).

High Stereoselective Glycosylation of Calix[4]arenes with α-Acetobromoglucopyranoside

Glycosylation of calix[4]arenes with a - acetobromoglucopyanoside 1 inacetonitrile in the presence of potassium carbonate or calcium hydride under mildconditions gave sugar calix[4]arenes 4 and 5 in good yields, and β-anomers were thesole products with high stereoselectivity. Compound 4 or 5 were dealt with anunoniain methyl alcohol to afford the Waer-soluble calix[4]arenes derivatives 6 and 7.

Synthesis of Bis-substituted Calix[4]arenes and Mechanism of Substituents Effect on K^+ and Hg^(2+) Ions Transports through Liquid Membrane

New calix[4]arene derivatives containing nitro,amino and benzoyl in the upper and lower rims of molecule were successfully synthesized.Their effectiveness towards K+ and Hg2+ across bubbling liquid membrane(BLM) was examined.For K+ ion transfer,preserving phenolic hydroxyl in the lower rim of calix[4]arene could enhance its transport ability.When benzoyl replaced phenolic hydroxyl,the transport would fall off,because benzoyl caused steric hindrance on the K+ transfer.The study also revealed that the group having the electron-withdrawing conjugative effect on phenolic hydroxyl,-NO2 in the upper rim of calix[4]arene,made transport ability of calix[4]arene fall off.On the contrary,-NH2 that had electron-repulsive conjugative effect enhanced the transport ability of the compound.For Hg2+ ion,only -NH2 in the upper rim of calix[4]arenes had high affinity for it and contributed to Hg2+ transfer.Transport amount of Hg2+ ion increased with increasing calix[4]arene5 concentration and ΔpH in BLM.

THE FRIEDEL-CRAFTS REACTION OF CALIXARENES^1

By optimization of the reaction conditions, the p-acylation of calixarenes by the Friedel-Crafts reaction succeeded in moderate to good yields.

Synthesis of Pyridylazo-substituted Chromogenic Calix[4]arenes

This letter reports a novel method for preparing chromogenic calix[4]arenes, in which the 4-aminopyridine was diazotized with isoamyl nitrite in EtONa/EtOH, and mono(azo)-, bis(azo)- and tetra(azo)-substituted calix[4]arenes were obtained as main product respectively by diazo-coupling in different molar ratio to calix[4]arene in non-aqueous solution at 0-5℃.

Mono-functionalized pillar[n]arenes: Syntheses, host–guest properties and applications

Pillar[n]arenes are a novel class of macrocyclic hosts reported by Ogoshi and co-workers in 2008. Because of their rigid pillar structures, interesting host-guest properties and ease of modifications, pillar[n]arenes have been developed rapidly in the field of functional materials and biomedicine. The modifications of pillar[n]arenes at different positions can give them varied characteristics. Functional groups can be introduced into one position of pillar[n]arenes without changing host-guest properties of pillar[n]arenes. A series of pillar[n]arene dimers, trimers, tetramers and metallacycles can be constructed by mono-functionalized pillar[n]arenes. In this review, two synthetic methods of mono-functionalized pillar[n]arenes are summarized and structures containing mono-functionalized pillar[n]arenes are described. Furthermore, the applications of mono-functionalized pillar[n]arenes in different fields (e.g., supramolecular polymers, sensors, molecular machines, catalysis, biological applications and light-harvesting systems) are also introduced. Hopefully, this article will be useful for researchers studying pillar[n]arenes, especially the mono-functionalized pillar[n]arenes.

A Novel Type of Lower-Rim-Connected Double-Calix[6]arenes Composed of A 1,2,4-Triply Bridged and A Normal Calix[6]arene

The synthesis and characterization of the first example of lower-rim-connected doublecalix[6]arene are reported, in which a l,2,4-triply bridged calix[6]arene subunit is connected to a calix[6]arene subunit via a polyether chain.

Selective nickel-electrocatalyzed benzylic C-H oxygenation of functionalized alkyl arenes

Herein, a site-selective paired electrochemical C–H oxidation of functionalized alkyl arenes promoted by nickel catalyst is disclosed. A Ni(Ⅱ)-dioxygen species formed in situ efficiently enable the oxidation process under mild conditions with a broad substrate scope with excellent functional group compatibilities,such as free carboxylic acid, aldehyde, halogen(including aryl iodide), amide and amino acid. The use of the nickel catalyst in combination with water provides a safe, green and economical method for oxidation of a range of molecules varying in complexity and drug derivatives, demonstrating its potential application in organic synthesis and the pharmaceutical industry. Reaction outcomes and mechanistic studies revealed the key role of the in situ Ni(Ⅱ)-dioxygen species for the subsequent oxidation of C(sp^(3))–H bonds,and short-lived reactive intermediates(aryl radical cation) was rapidly captured by the combination of a bipolar ultramicroelectrode(BUME) with nano-electrospray ionization mass spectrometry.

Pillar[6]arenes: From preparation, host-guest property to self-assembly and applications

Pillar[n]arenes primarily comprise pillar[5]arenes and pillar[6]arenes, which belong to the new class of supramolecular macrocyclic hosts. Pillar[n]arenes have aroused wide attention because of their highly rigid and symmetrical architectures, controllable cavity size, and wide applications in a wide variety of areas. Although pillar[6]arene is difficult to synthesize, numerous studies have been conducted on it. In this review, the strategies to synthesize and functionalize pillar[6]arenes are investigated systematically.In addition, their host-guest properties in organic solvents and in aqueous solution are described. Moreover, pillar[6]arenes applied in different fields(e.g., molecular recognition, drug release, cancer therapy,and gas separation) are clarified. Hopefully, this study is capable of arousing more attention from increasing scientists to study large-cavity pillar[n]arenes.

Imidazobenzimidazole fused aza-calix[4]arenes:Synthesis,structure,and Zn^(2+)-selective colorimetric-fluorometric sensor

Tetra(amino)azacalix[4]arene skeleton was functionalized at the bridging NH sites using various aromatic aldehydes via formation of imidazobenzimidazole fused heterocycles.X-ray single crystal analysis revealed distorted 1,3-alternate conformations for the resulting macrocycles.Anthracenyl and pyrenyl modified imidazobenzimidazole fused aza-calix[4]arenes existed as dimers in the solid state,associated mainly through-stacking interactions between the planar polycyclic fluorophores.The tetrapyrenyl modified product was further used as a Zn^(2+)-selective sensor,which showed naked-eye detected color change and enhanced excimer emission.The stoichiometry between the sensor and Zn2+was determined to be 1:1 and the association constant was 1.1×10^(5)L/mol.The sensing process was highly selective and showed strong anti-interference with presence of other cations.The UV-vis spectral changes in the sensing process were completely reversible by alternate addition of Zn^(2+) and F^(-),showing an efficient“on-off-on”result.

Prospering the biphen[n]arenes family by tailoring reaction modules

Reported here is the comprehensive investigation on the formation of biphen[n]arenes by tailoring reac-tion modules.Five new macrocyclic arenes and four oligomers were synthesized by the condensation of monomers possessing different multimethoxyphenyl reaction modules and paraformaldehyde.We proved that the number and sites of methoxy on reaction modules greatly affected the reaction activity,shape,and connection mode of macrocycles.Moreover,the triangular and saddle-shaped configuration of macro-cycles were revealed by single crystal structures.The results provided a typical and fundamental guidance in designing new macrocyclic arenes.

Dynamic materials fabricated from water soluble pillar[n]arenes bearing triethylene oxide groups

Pillar[n]arenes are a new kind of supramolecular macrocyclic hosts which have developed rapidly due to their unique topology and high functionality, giving rise to many applications in the construction of interesting and functional materials. Among them, water-soluble pillar[n]arenes bearing triethylene oxide (TEO) chains have drawn increasing research interest due to their advantageous properties. In this review, we summarized the recent progress of dynamic materials fabricated from water soluble pillar[n]arenes bearing TEO groups, including thermo responsive materials with lower critical solution temperature (LCST) behavior, cyclic host liquids, and smart windows. It is anticipated that more and more ‘smart' supramolecular materials based on modified pillar[n]arenes will be developed in this burgeoning area of research.

Electrooxidation-Induced C(sp^(3))-H/C(sp^(2))-H Radical-Radical Cross-Coupling between Xanthanes and Electron-Rich Arenes

The arylation of C(sp^(3))-H bonds has been a priority research topic in organic synthesis.Minsici reactions have been the powerful methods for C(sp^(3))-C(sp^(2))bonds formation.Despite its mature development,the scopes of arenes are usually suitable for elec-tron-deficient heterocyclic compounds,rather than electron-rich arenes.Herein,we report an electrooxidation-induced alkylation of electron-rich arenes with H_(2) evolution under exogenous oxidant-free conditions,avoiding the utilization of metal catalysts.This pro-tocol is well performed with various electron-rich aniline derivatives and nitrogen-containing heterocyclic compounds.We anticipate that this electro-oxidative C(sp^(3))-H arylation represents an important expansion for the classic arenes alkylation,thereby proving an attractive strategy for the developments of radical cross-coupling chemistry.

Upper-rim-modified thioether thiacalix[4]arene used for liquid-liquid extraction of Au(Ⅲ)and Pd(Ⅱ)in hydrochloric acid medium

Gold(Au)and palladium(Pd)play an increasing role in the production and human life;Therefore,it is of great significance to study their recovery.A 5,11,17,23-tetra-ethylthio-25,26,27,28-tetra-hydroxyl thiacalix[4]arene(TCAET)was synthesized specifically for the capture of Au(Ⅲ)and Pd(Ⅱ)from HCl medium by liquid-liquid extraction.In a 0.1 mol·L^(-1)HCl medium,the transfer of Au(Ⅲ)and Pd(Ⅱ)from the aqueous phase to the organic phase was highly efficient,with a transfer ratio of 100%for Au(Ⅲ)and 98%for Pd(Ⅱ).Furthermore,the extraction equilibrium time for Au(Ⅲ)was just 5 min.Job's method data demonstrated that TCAET formed complexes with Au(Ⅲ)and Pd(Ⅱ)in a ratio of 2:3 and 1:1,respectively,during the extraction process.TCAET showed high selectivity toward Pd(Ⅱ)and Au(Ⅲ)over other competing metal ions.Moreover,both Au(Ⅲ)and Pd(Ⅱ)could be successfully stripped from the loaded organic phases with a 1.0 mol·L^(-1)thiourea in 0.5 mol·L^(-1)HCl and 0.5 mol·L^(-1)thiourea in 0.5 mol·L^(-1)HCl,respectively.Results obtained from five consecutive extraction-stripping cycles showed good reusability of TCAET toward Au(Ⅲ)and Pd(Ⅱ)recovery.The conclusion can provide a certain reference for thiacalixarene in the recovery of precious metal species.

Crystal Structure and Host-Guest Binding Ability of Three Types of Pillar[5]arenes

A systematic research of the structural characterization and the host-guest binding abilities between three types of pillar[5]arenes 3-5(3 for Structure Type I,4 for Structure Type II and 5 for Structure Type III)is carried out by 1H NMR measurements and X-ray study.The results show that the configurations or symmetry of their cavities not only have large difference in these three types of pillar[5]arenes,but also have more or less variations even in the same structure type or the same host locked different guests such as crystals of 3a-3b,4a-4d.On the other hand,the complexation behavior of pillar[5]arenes with 1,4-dibromobutane(DBB)is affected by the different symmetri-cal structure or substituents on the rings.