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Cyclohexylphenols are valuable intermediate chemicals applied in the manufacture of dyes, resins, and pharmaceutical drugs. However, they are synthesized using raw chemicals derived from fossil fuels rather than sustainable sources (e.g., lignin-derived phenol). In this article, we report a one-pot synthesis of cyclohexylphenols via phenol-assisted conversion with isopropyl alcohol over the tandem catalytic system formed by RANEY® Nickel plus hierarchical Beta zeolite. Over this tandem catalytic system, cyclohexylphenols were synthesized with remarkable selectivity (∼70%) at high conversion rates (64%) after 1 h of reaction at 150° C. In contrast, higher temperatures (175 °C) were required to obtain alkylphenols over the Al-SBA-15 catalyst, which is highly accessible thanks to its uniform mesoporous structure, albeit with weaker Lewis acid sites. Additionally, selectivity to cyclohexylphenols over Al-SBA-15 was far lower (19%) than over hierarchical Beta zeolite, and cresols were instead the most abundant alkylphenol (26%). Therefore, the combination of suitable accessibility and Brønsted acidity of hierarchical Beta with the hydrogenating ability of RANEY® Ni through catalytic hydrogen transfer from isopropyl alcohol drives the selectivity of this tandem system towards the production of cyclohexylphenols. [ABSTRACT FROM AUTHOR]

The dialkylation of 2,14-dithiacalix[4]arene was studied employing various synthetic procedures known for the parent macrocycles (thiacalixarenes and/or classical calixarenes). The best results for distal dialkylation were achieved using the Mitsunobu reaction with the corresponding alcohols. Interestingly, due to the lower symmetry of the starting compound, the dialkylated derivatives represent inherently chiral systems. The introduction of chiral substituents thus leads to mixtures of diastereomers potentially useful for the separation of individual stereoisomers as demonstrated by chiral HPLC. The conformational behavior of the novel compounds was studied both in solution (NMR) and in the solid state (X-ray). [ABSTRACT FROM AUTHOR]

The meta- and para-substituted aminocalix[4]arenes immobilized in the cone conformation were acylated to yield the corresponding acyl amides. Subsequent cyclization with aryl or alkyl cyanides afforded the expected quinazolines only in the case of the para-substituted series, while only complex reaction mixtures were obtained for the meta-substituted analogues. This finding was used as a strategy for the preparation of novel inherently chiral calixarenes with strong fluorescence. The structure of the products was proved by the combination of NMR and single crystal X-ray analyses. The dynamic NMR study of quinazoline derivatives revealed the existence of two different atropisomers in solution at lower temperatures. As evidenced by resolution with a chiral HPLC column and by the fluorescence titration experiments, novel quinazolines represent inherently chiral macrocycles of high potential for the design of chiral calixarene-based receptors. [ABSTRACT FROM AUTHOR]

Research activities and recent developments in the area of three-dimensional zeolites and their two-dimensional analogues are reviewed. Zeolites are the most important industrial heterogeneous catalysts with numerous applications. However, they suffer from limited pore sizes not allowing penetration of sterically demanding molecules to their channel systems and to active sites. We briefly highlight here the synthesis, properties and catalytic potential of three-dimensional zeolites followed by a discussion of hierarchical zeolites combining micro- and mesoporosity. The final part is devoted to two-dimensional analogues developed recently. Novel bottom-up and top-down synthetic approaches for two-dimensional zeolites, their properties, and catalytic performances are thoroughly discussed in this review. [ABSTRACT FROM AUTHOR]

The advanced investigation of pore networks in isoreticular zeolites and mesoporous materials related to the IPC family was performed using high-resolution argon adsorption experiments coupled with the development of a state-of-the-art non-local density functional theory approach. The optimization of a kernel for model sorption isotherms for materials possessing the same layer structure, differing only in the interlayer connectivity (e.g. oxygen bridges, single- or double-four-ring building units, mesoscale pillars etc.) revealed remarkable differences in their porous systems. Using high-resolution adsorption data, the bimodal pore size distribution consistent with crystallographic data for IPC-6, IPC-7 and UTL samples is shown for the first time. A dynamic assessment by positron annihilation lifetime spectroscopy (PALS) provided complementary insights, simply distinguishing the enhanced accessibility of the pore network in samples incorporating mesoscale pillars and revealing the presence of a certain fraction of micropores undetected by gas sorption. Nonetheless, subtle differences in the pore size could not be discriminated based on the widely-applied Tao–Eldrup model. The combination of both methods can be useful for the advanced characterization of microporous, mesoporous and hierarchical materials. [ABSTRACT FROM AUTHOR]

The ability of the antispasmodic agent trospium chloride (TCl) to form solvates was investigated by applying conventional solvate screening methods on 20 solvents. According to the solubility of TCl, different approaches were considered (slow evaporation, slurrying and anti-solvent addition). Five solvates, with the solvents methanol, acetonitrile, propionitrile, N,N-dimethylformamide, nitromethane and dihydrate, were identified and characterized by various analytical techniques. Moreover, a solvate with isopropyl alcohol and TCl sesquihydrate was prepared circumstantially outside the systematic screening. The structures of all the solvates were determined by single crystal X-ray diffraction. The reproducible forms were further characterized by powder X-ray diffraction and desolvation behaviour was observed by thermoanalytical (TGA/DSC) methods. Structural features of novel solvates and of previously described polymorphs and cocrystals of TCl were compared, presented by a tree diagram which classifies the structures according to their molecular packing. [ABSTRACT FROM AUTHOR]

The inter-layer interactions and the possible arrangements of MWW-type layers were investigated computationally at the non-local density functional theory level. Powder XRD patterns were simulated for structures obtained computationally and compared with experimental data. The MCM-22P material corresponds to the layers bound with relatively strong hydrogen bonds between surface silanol groups that is an energetically preferred structure in the presence of a structure directing agent (hexamethyleneimine). The powder XRD pattern of MCM-56 is best matched for relatively disordered (in the ab plane) MWW layers that are partially condensed. The appearance of the powder XRD pattern in the 2 range of 7.5-10° depends on the extent of interlayer condensation. The combination of density functional investigation of interactions between MWW layers together with simulation of powder XRD patterns brings atomistic insight into the inter-layer arrangement and better understanding of the effects responsible for the differences between various layered materials of the MWW family. [ABSTRACT FROM AUTHOR]

Modification of HMCM-22 zeolite by alkaline treatment was investigated by various characterization techniques and in toluene disproportionation and alkylation with isopropyl alcohol. This ‘desilication’ process led for mild alkaline concentrations (~0.10–0.20 M NaOH at 323 K for 45 min) to the partial destruction of the zeolite framework, but also to the formation of additional mesoporosity. Furthermore, the accessibility/availability of Lewis acid sites, investigated by d3-acetonitrile and pyridine adsorption using FTIR spectroscopy, increased for these mild alkaline treatments, while the Brønsted acidity decreased. Higher alkaline concentrations (up to 0.50 M NaOH) led to a too severe framework and pore destruction and a decrease of both the Lewis and Brønsted acid site concentration. Decomposition and deconvolution of 29Si MAS-NMR spectra confirmed the Si extraction and partial framework destruction, since more Q3 SiOH groups were formed at the expense of the Q4 T-atoms in the framework. Furthermore, the T6 and T7 Si-atoms were preferentially extracted, which would indicate that an interconnection between the intralayer and the interlayer and/or outer surface is formed. The toluene conversion in its disproportionation reaction increased for the mildly treated sample, while the selectivity to xylene isomers (and cymene and n-propyltoluene isomers in the alkylation reaction with isopropyl alcohol) was similar to the thermodynamic equilibrium, suggesting that the reaction primarily occurs at outer surface cups of the HMCM-22 zeolite. [ABSTRACT FROM AUTHOR]

Liquid phase Friedel-Crafts acylation of cyclohexene and 1-methylcyclohexene was investigated over zeolites and mesoporous molecular sieves. The effect of the structure and concentration and type of active sites on the conversion and selectivity of cyclohexene and 1-methylcyclohexene was investigated. In addition, the effect of the chain length of acylating agent was studied. Catalytic experiments were carried out at temperature 80 °C and at atmospheric pressure. The highest conversion was reached over zeolite Beta with Si/Al ratio 37.5 (cyclohexene conversion 78.7%, 1-methylcyclohexene conversion 54.1%). It was found that with increasing chain length of the acylating agent cyclohexene as well as 1-methylcyclohexene conversions decrease. No direct relationship between the conversion of cyclohexene or 1-methylcyclohexene and the concentration of Lewis acid sites was found. [ABSTRACT FROM AUTHOR]

Hymecromone, an important insecticide intermediate, were synthesized under solvent-free conditions by Pechmann reaction upon ultrasound irradiation in the presence of acid zeolites possessing different structural features. This methodology offers significant improvements for the synthesis of coumarins with regards to yield of product, simplicity in operation, and avoiding toxic catalysts and solvents. [ABSTRACT FROM AUTHOR]

SSZ-33 based-catalyst, after modification with Mo and alumina binder, was evaluated in long-run tests in the toluene disproportionation in the presence of hydrogen as a carrier gas. The activity and selectivity of this catalyst were compared with those of ZSM-5 and mesoporous ZSM-5 prepared with the same concentration of Mo and alumina. Formation of the final catalysts decreased the void volume of micropores in order SSZ-33 > ZSM-5 > ZSM-5/Meso. Simultaneously, the concentration of Lewis acid sites increased due to the addition of alumina to the catalyst. The highest toluene conversion was achieved with SSZ-33 catalyst comprising 12-12-10-ring channels, which is the result of high acidity of this zeolite together with increased mass transport through large pores. ZSM-5 zeolite exhibited lower toluene conversion while only a low activity was found for mesoporous ZSM-5 probably due to the limitations of the access to the zeolite channels after modification with alumina. [ABSTRACT FROM AUTHOR]

Aromatic hydrocarbons represent an important group of starting materials, intermediates, as well as final products produced in the chemical industry in the range from large processes in petrochemistry up to the synthesis of fine chemicals. This short overview covers the recent achievements in acid-catalyzed transformations of aromatic hydrocarbons with a special focus on alkylation–isomerization–disproportionation reactions in petrochemistry, and acylations or condensations used mainly in synthesis of chemical specialties. In the case of fine chemical synthesis, some zeolite applications in the preparation of important intermediates for pharmaceutical or fragrance products are presented. Advantages and disadvantages of the various types of zeolite are discussed in these reactions from the point of view of their (shape) selective properties, as well as the accessibility of acid sites. [ABSTRACT FROM AUTHOR]

Valency changes of iron and tin in framework-substituted microporous and mesoporous molecular sieves (Fe-ETS-10, Fe-ZSM-5, Fe-AlPO-11, Sn-ZSM-12 and Sn-MCM-41) have been studied under reducing and oxidizing conditions by in situ Mössbauer spectroscopy. It is demonstrated that the structure of the host matrices strongly influences the stabilization and the oxidation state of the ions. Debye temperature, ΘD, data also are estimated, they support the suggested structural assignment of various species. [ABSTRACT FROM AUTHOR]