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3-Phenylimidazo[1,2- a]pyridines were synthesized through the perfluorohexyl iodide mediated coupling of 2-aminopyridines and phenylacetylenes. In situ iodination of the terminal alkyne by perfluorohexyl iodide reverses the polarity by generating a transient electrophilic iodoalkyne, and this alters the regioselectivity of the phenyl group. The reaction then proceeds by tandem electrophilic alkynylation and cyclization to form the fused-ring product. The protocol affords the 3-phenyl isomer with full regioselectivity and is complementary to reported methodologies for the synthesis of the 2-phenyl isomer starting from the same substrates. [ABSTRACT FROM AUTHOR]

Amines were used as hydrogen donor for the borrowing hydrogen methodology with a heterogeneous catalyst. Supported copper catalysts catalyzed the self-condensation reaction of primary amines to secondary amines/imines with high efficiency. The recyclable, non-leaching catalyst is synthesized by a sol–gel method, which allows entrapping copper nanoparticles in an alumina matrix. The synthesized copper catalysts were found to be active in the self-coupling of primary amines to produce secondary amines. The hydrogen donor for the transfer hydrogenation appears to be the primary amine, and no additional hydrogen or hydrogen transfer reagent is required. To the best of our knowledge, this is the first report of a copper based catalyst for this type of reaction using the borrowing hydrogen scheme. [ABSTRACT FROM AUTHOR]

The ammonia evaporation method, originally applied for the preparation of highly dispersed silica-supported copper catalysts, was used to synthesize magnesia-silica for the one-step conversion of ethanol to 1,3-butadiene. The MgO-SiO2 catalysts obtained by this method contained a high fraction of magnesium silicate hydrates, which are associated with enhanced butadiene selectivity. These catalysts were benchmarked against those prepared by a conventional wet-kneading method. A Mg/Si molar ratio of 4 was optimal, forming butadiene with 37% yield, which is far superior to the 15% yield obtained with MgO-SiO2 formed by wet-kneading. At 475 °C and a WHSV of 3.2 h−1, a productivity of 0.612 gBD gcat−1 h−1 was measured without the catalyst suffering from deactivation, even after 52 h TOS. The catalysts were characterized by spectroscopic and thermal techniques to elucidate their physicochemical properties and explain the differences in the catalytic performance. The presence of magnesium silicate hydrates gave a balance of surface acidity and basicity, which greatly improved butadiene formation. The open morphology of MgO-SiO2 with vertically arranged platelets and the presence of large pores are proposed to contribute to the stability of the catalyst. [ABSTRACT FROM AUTHOR]

Abstract: Trihexyl (tetradecyl) phosphonium tetrafluoroborate was found to be an active catalyst for the introduction of fluoride by nucleophilic aromatic substitution. With a decomposition temperature above 300°C, this ionic liquid is suitable for reactions at high temperatures. The addition of 1mol% of the ionic liquid relative to KF increased the initial rate for the fluorination of 1,2-dichloro-4-nitrobenzene six-fold compared to the uncatalysed reaction. The highest reaction rate was observed at 20mol% ionic liquid relative to KF. Ease of handling without the need for stringent drying conditions and reuseability make this ionic liquid a useful phase transfer catalyst. [Copyright &y& Elsevier]

Abstract: Ag/Al2O3 catalysts were found to be highly active and selective in the N-alkylation of aniline with a variety of aromatic and linear alcohols. In the presence of a base, for example, Cs2CO3 or K3PO4 as promoter, high yields of secondary amines were obtained. The highest activity was found with 2.4wt.% Ag/Al2O3. The reaction involves the transient catalytic dehydrogenation of the alkylating alcohol to the corresponding carbonyl compound which then reacts spontaneously with the amine. In the final step, the hydrogen from the alcohol dehydrogenation step is transferred back to the imine, giving the secondary amine as the final product. With secondary amines, piperidine and pyrrolidine, the hemiaminal intermediate can undergo dehydrogenation as well as dehydration to give amides and amines, respectively. The heterogeneous nature of Ag/Al2O3 allows for easy recovery and regeneration, which makes it an attractive system in the context of green and sustainable synthesis. [Copyright &y& Elsevier]

Abstract: Zr-zeolite beta with Si/Zr ratio of 75–200, as well as zeolite beta with both Zr (Si/Zr ratio of 100) and Al (Si/Al ratios of 100 and 25), were synthesized in a seeded synthesis using HF as the mineralizer. The Al-free Zr-zeolite beta was found to catalyse the MPV reduction of -unsaturated aldehydes to the corresponding alcohols with high selectivity. In the reduction of cinnamaldehyde to cinnamyl alcohol, TONs of 55–77 mol mol−1 Zr h−1 were obtained with selectivity . Zr-zeolite beta maintained good activity and selectivity in the presence of water and benzoic acid. Reuse of the catalyst by washing with 2-propanol or recalcination led to recovery of activity. For the Al-containing Zr-zeolite beta, 27Al NMR spectra showed that Al was incorporated into the zeolitic framework. This is in agreement with pyridine adsorption studies in which Brønsted acidity was detected. However, the increased acidity decreased the selectivity in the MPV reduction of cinnamaldehyde as a significant amount of 1-cinnamyl 2-propyl ether was formed as a byproduct. Hence, Al-free Zr-zeolite beta is a useful chemoselective catalyst for the MPV reduction of -unsaturated aldehydes. [Copyright &y& Elsevier]

Kinetic resolution of racemates with the help of enzymes has become a widely adopted method for the synthesis of chiral intermediates and compounds with biological activity. However, the inherent limitation to 50% yield of any one stereoisomer restricts the use of this method in industrial practice, when only one of the stereoisomers is required. The yield can theoretically be improved to 100% through either a chemical reaction, which inverts the stereochemistry at the optical active center, or through racemization of the unwanted isomer, followed by additional enzymatic resolution. The combination of the racemization of the slower reacting stereoisomer with kinetic resolution in a one-pot reaction is termed dynamic resolution. We describe the dynamic resolution of secondary alcohols through enzymatic stereoselective transesterification and heterogeneously catalyzed racemization of the alcohol over several zirconia-containing catalysts. In order to facilitate the separation of the products, we used a fluorous phase-switching technique coupled with fluorous extraction. The continuous extraction in a membrane contactor allows for facile recovery of the fluorous tagged species in a scaleable operation. The unoptimized scheme offers over 90% conversion with ca. 75% enantiomeric excess (e.e.). [Copyright &y& Elsevier]

Hydrous zirconia and grafted zirconium 1-propoxide catalysts were found active in the Oppenauer oxidation of cinnamyl alcohol, geraniol and 4-tert-butylcyclohexanol (cis- and trans-). The most active hydrous zirconia catalysts were formed by calcining at 250–300°C. Grafted zirconium 1-propoxide on silica gel and MCM-41 were active in the Oppenauer oxidation of geraniol with high selectivity to the desired citral product. However, over an acidic support such as AlMCM, the grafted zirconium 1-propoxide catalysed the dehydration and isomerisation of the alcohol, leading to low yield to citral. Also, furfural was found to be an efficient oxidant for the titled Oppenauer oxidation. Other solid catalysts such as γ-Al2O3, Na–Al2O3, zeolite beta and Mg/Al hydrotalcite showed only moderate catalytic activity and selectivity in the Oppenauer oxidation of geraniol. As compared to other solid catalysts, hydrous zirconia solid catalysts used in this work are active and selective towards the formation of desired carbonyl oxidation products; additionally, these solid zirconia catalysts are easy to prepare and recycle, and applicable to different alcohol substrates. [Copyright &y& Elsevier]

Bismuth oxyhalides BiOX (X = Cl, Br, I) are seldom applied as photocatalysts in organic synthesis. Herein, we investigated their potential for the aerobic oxidative coupling of benzylamine to N -benzylidenebenzylamine, as imines are important synthetic intermediates of pharmaceuticals and biologically active nitrogen-containing organic compounds. The influence of the halide and the exposed crystal facets on the photoactivity was investigated. BiOBr showed excellent photoactivity, surpassing BiOCl and BiOI, which have poor light absorption and oxidation ability, respectively. Three differently facetted BiOBr photocatalysts were synthesized. The {001}-facetted BiOBr exhibited higher intrinsic activity than the {010}- or {110}-samples due to efficient charge separation. However, surface area plays an important role as reactions usually occur at the catalyst surface. Because of their much larger surface area, the solvothermally-synthesized BiOBr microspheres with {110}-dominant exposed facet showed the highest photooxidative activity, with 100% conversion and 100% selectivity to N -benzylidenebenzylamine after 14 h visible light irradiation at room temperature using oxygen from atmospheric air. This work provides an economical, feasible, sustainable and green process for the synthesis of imines and illustrates the great potential of bismuth oxyhalides as photocatalysts for organic synthesis. [ABSTRACT FROM AUTHOR]

A straightforward synthesis of 5-phenylthiazolamines by coupling thiourea with phenylacetones, phenylacetophenones, and β-tetralone has been developed. Thiourea acts as a substrate and an α-bromination shuttle by transferring a Br atom from CBrCl3 to the α-carbon of the carbonyl moiety. A series of steps are then triggered to reach the final product. Isolated yields from 80 to 95 % were obtained. Key features of this protocol include its minimal use of reagents (i.e., substrates, CBrCl3, and CsHCO3), its short reaction times under mild conditions (at 80 °C for 2-3 h), and its ease of scale up to prepare gram quantities of product. [ABSTRACT FROM AUTHOR]

A wide range of imidazo[1,2- a]pyridines are accessible from cheap and readily available 2-aminopyridines and 1,3-dicarbonyl compounds using a unique CBrCl3/2-aminopyridine system for bromination at the α-carbon. 2-Aminopyridine is not only the substrate but also acts as a bromination shuttle, transferring the bromine atom from CBrCl3 to the α-carbon of the 1,3-dicarbonyl. The reaction mechanism involves a series of reversible steps, including an addition reaction with cyclic transition state, to form a bromo-hemiaminal intermediate. Isolated yields of up to 97% were obtained under mild conditions and at short reaction times in this transition metal-free, one-pot synthesis. [ABSTRACT FROM AUTHOR]

Polysubstituted furans were obtained with excellent yields via the electrophilic alkynylation of 1,3-dicarbonyl compoundsws with phenyl- or ester-substituted brominated alkynes. The reaction is catalyzed by the inexpensive and readily available catalyst, cobalt(II) chloride, and has a wide substrate scope. The C( sp)C( sp3) coupling occurs under mild conditions with short reaction times and does not require an inert atmosphere or ligands. It is proposed that the reaction proceeds through a chelation complex of cobalt(II) with the deprotonated 1,3-dicarbonyl compound. [ABSTRACT FROM AUTHOR]

Ruthenium encapsulated in an aluminium oxyhydroxide-support was investigated for the transfer hydrogenation of aldehydes and ketones with potassium formate as a sustainable green hydrogen donor. The entrapped ruthenium were narrowly distributed with mean diameters of 1.5–1.8 nm. XPS studies show that the ruthenium was present as Ru 0 and Ru 3+ . The catalysts showed high activity even at low metal loadings of 0.5–2 wt.%. The maximum TOF for benzaldehyde hydrogenation was over 1 wt.% Ru. The reduction of aromatic and aliphatic aldehydes was facile and occurred with 100% yield. In comparison, ketones were less readily reduced although moderate to excellent yields could be obtained after a longer reaction time. No leaching of ruthenium was observed in contrast to a catalyst prepared by wet impregnation. Washing of the used catalyst with water and ethanol effectively removed the deposited bicarbonate co-product and the recycled catalyst maintained its activity up to five runs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rapid crystallization of Zr-Beta with high Zr content possible with MCLA protocol. • Zr-Beta formed with high crystallinity and hydrophobicity. • High Zr loadings useful in MPV reduction of sterically hindered ketones and diones. • MCLA-synthesized Zr-Beta is less susceptible to poisoning by water adsorption. Heteroatom-incorporated zeolite catalysts are critical for biomass utilization and feedstock valorization in green chemistry. Key features are adjustable acidity, high stability, and a tailored range of functionalities. However, an environmentally benign synthesis of zeolites with good crystallinity and especially with high levels of metal substitution into the lattice remains challenging. Here, we propose a mechanochemistry-based liquid-assisted method (MCLA) for Zr-incorporated Beta zeolites that is high yielding, facile and sustainable. Compared with the fluoride-mediated hydrothermal method, crystallization times were considerably shortened so that Si-Beta and Zr-Beta (Si/Zr 100) zeolites can be synthesized within 9 and 15 h, respectively. Using the MCLA route, Beta zeolites with Zr loading up to 10.4 wt% (Si/Zr 12.5) were obtained. The materials have excellent catalytic activity for Meerwein-Ponndorf-Verley reductions with much higher water tolerance compared to Zr-Beta prepared by the post-synthesis method. The hydrophobic nature of the MCLA-synthesized zeolites makes them particularly useful as catalysts for organic reactions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mg incorporated into zeolite Beta framework by two-step postsynthesis procedure. • Rh3+/[MgO 4 ]2- electrostatic interactions stabilize single Rh atoms. • Catalytic efficiency of Rh/Mg-Beta due to low atomic coordination and basicity. • High selectivity in phenol hydrogenation to cyclohexanone at mild conditions. Nanoparticles are of interest in heterogeneous catalysis because of their excellent activity associated with atoms in a low coordination environment. However, their high reactivity becomes a drawback where selectivity is desired, compounded by their propensity towards agglomeration. Here, we show that stable subnanometric Rh particles can be prepared in a Mg-doped zeolite Beta based on the electrostatic interaction of the negatively charged zeolitic framework and the Rh3+ precursor. The Mg ions are incorporated into the zeolite framework whereas the Rh is located in the channels adjacent to the Mg. With only 0.27 and 0.5 wt% Mg and Rh, respectively, the Rh/Mg-Beta catalysts were highly active with > 94 % selectivity for the hydrogenation of phenol to cyclohexanone, an important intermediate for the production of Nylon. Key to the selectivity is the formation of the C=O double bond early in the reaction sequence, aided by the basicity of the Mg-Beta support. [ABSTRACT FROM AUTHOR]

Beta-Silicalite-1 core-shell microcomposites with controllable shell thickness were synthesized and used as racemization catalysts in the one-pot dynamic kinetic resolution (DKR) of secondary alcohols by using lipase-catalyzed transesterification. The inert Silicalite-1 shell covered the external acidic sites of the Beta zeolite core, suppressing dehydration and non-enantioselective transesterification of the alcohol. The alcohols could penetrate the Silicalite-1 shell to access the acidic sites at the core Beta for racemization, however, the enzymatically formed ( R)-esters were excluded owing to their larger size. As a result, the high ee of the ( R)-ester products was conserved and dehydration side products were minimized. Owing to the shape selective nature of the composite racemization catalyst, small and readily available acyl donors could be used in the enzyme-catalyzed transesterification to obtain the esters with high enantiopurity. The DKR of 1-phenylethanol with isopropenyl acetate using an optimized core-shell catalyst, CS-60, gave 92 % selectivity to ester formation and the desired ( R)-1-phenylethyl acetate was formed with 94 % ee. [ABSTRACT FROM AUTHOR]

Abstract: Prins condensation of β-pinene with paraformaldehyde was carried out over MCM-22, delaminated ITQ-2 and silica pillared MCM-36. The mesopore-containing MCM-36 and ITQ-2 catalysts exhibit higher conversion of β-pinene due to more exposed acid sites. Lewis acid sites are responsible for Prins condensation while Brønsted acid sites favor the isomerization of pinene. The Brønsted acid sites can be removed mostly by ion-exchanging the zeolites with sodium cations. Thus, NaMWW zeolites had a higher selectivity towards Nopol. Of these, NaITQ-2 showed the highest activity and selectivity, and is a stable and reusable catalyst for production of Nopol. [Copyright &y& Elsevier]

Abstract: The direct formation of hydrogen peroxide from H2 and O2 was successfully carried out in a capillary microreactor at room temperature and atmospheric pressure. A key element in sustaining the activity of the catalyst is the incarceration of the palladium nanoparticles in a cross-linkable amphiphilic polystyrene-based polymer, prepared following the protocol of Kobayashi [R. Akiyama, S. Kobayashi, J. Am. Chem. Soc. 125 (2003) 3412–3413]. The immobilization effectively reduced the leaching of palladium under acidic conditions. Applying the catalyst as a coating on the inner walls of a capillary enabled the sustained production of 1.1% hydrogen peroxide over at least 11days. The highest catalyst utilization in a 2mm capillary reactor was 0.54molH2O2/hgPd. When the inner diameter of the reactor capillary was reduced to 530μm, the rate was enhanced fourfold to 2.28molH2O2/hgPd corresponding to a turnover frequency of 0.067s−1. [Copyright &y& Elsevier]

Abstract: Hydrothermal digestion of freshly precipitated cerium–zirconium hydroxides was used to synthesize nanocrystalline ceria–zirconia. This simple method produced ceria–zirconia with higher surface area and thermal stability than the untreated oxide. After calcination at 1000°C, the surface area of the hydrothermally synthesized samples was ∼11–12m2/g while the untreated Ce0.5Zr0.5O2 had only 4.2m2/g. The continuous dissolution and reprecipitation of hydroxides during hydrothermal treatment is postulated to a more defect-free structure which is able to withstand loss of surface area when exposed to high temperatures. In addition, these nanocrystalline oxides were more reducible than the untreated oxide. While the addition of silica to ceria–zirconia further increased the surface area and oxygen storage capacity, the oxides suffered severe loss of surface area after calcination to 1000°C. A silica-rich overlayer was formed which decreased the oxygen storage capacity as compared to silica-free ceria–zirconia. The oxygen storage capacity shows a strong dependence on the surface area for values below 50m2/g but diffusion of oxygen from the bulk becomes limiting for high surface area ceria–zirconia. [Copyright &y& Elsevier]

[Display omitted] • Gold nanostars (AuNS) were synthesized and stabilized by CTAC and thiophenol. • Encapsulation by TiO 2 confers robustness with retention of nanostar morphology. • AuNS@TiO 2 exhibits localized surface plasmon resonance and strong electric fields. • AuNS@TiO 2 is an effective photocatalyst for aerobic oxidation of alcohols. Gold nanostar (AuNS) particles, characterized by pointed tips emerging from a central core, exhibit localized surface plasmon resonance (LSPR) with strongly amplified electric field upon illumination. Compared to Au nanospheres and nanorods, the absorbance is enhanced with the absorption band extending from 500 to above 1000 nm. However, they are easily reshaped by Ostwald ripening and therefore difficult to use in any application. This study shows that the AuNS particles can be effectively stabilized by encapsulation with TiO 2 using a low temperature method. The synthesis parameters and capping solution were optimized to form nanostars. The encapsulated Au nanoparticles promoted the aerobic oxidation of benzyl alcohol to benzaldehyde at ambient temperature under visible light irradiation. AuNS@TiO 2 showed significantly higher photocatalytic activity than Au nanospheres, Au nanorods or bulk TiO 2 due to its enhanced LSPR. Encapsulation of the colloidal nanoparticles with TiO 2 confers robustness to the resulting heterogeneous catalyst with retention of the metal particle size, morphology and associated LSPR properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solid solutions of BiOBr n I 1-n can be formed via solvothermal synthesis. • Adjusting the Br/I ratio leads to tunable bandgaps of 1.95–2.95 eV in BiOBr n I 1-n. • Optimum balance of light absorption and redox potential in BiOBr 0.75 I 0.25. • BiOBr 0.75 I 0.25 is a versatile photocatalyst for photo oxidation of phenols and EDCs. A novel family of visible-light-sensitive photocatalysts, bismuth oxyhalide solid solutions (BiOBr n I 1-n , n = 0–1), was synthesized by a nonaqueous solvothermal method. The bismuth oxyhalides crystallized in individually separated platelets which aggregated into microspheres, allowing for efficient light capture. By increasing the Br/I ratio, the band gap of BiOBr n I 1-n could be tuned from 1.95–2.95 eV. The material with the composition BiOBr 0.75 I 0.25 exhibited the best photoactivity. It catalysed the degradation of p -cresol under visible light at a rate 31-times that of pure BiOBr and 1.7-times that of BiOI. BiOBr 0.75 I 0.25 proved to be a versatile photocatalyst for the degradation of a wide range of substituted alkyl phenols and endocrine disrupting chemicals (EDCs). Total organic carbon in the water was reduced to 10–33 % at > 99 % degradation efficiency. The excellent performance was attributed to a matching bandgap, balance between light absorption and redox potential, and efficient charge separation. Recyclability testing showed that BiOBr 0.75 I 0.25 maintained its high activity even after three cycles of p -cresol photodegradation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zr-HY is an excellent catalyst for the cascade reaction. • Hydrophobicity and cosolvents significantly accelerate the title reaction. • Ratio of open:closed Zr sites higher in Zr-HY than Zr-Beta. • IR of sorbed 2-pentanol probes hydrophobic/hydrophilic environment. Trans -anethole is an important ingredient in many flavors, fragrances and pharmaceutical formulations. Heterogeneous catalysis provides the opportunity for its green synthesis from 4′-methoxypropiophenone via a cascade of Meerwein-Ponndorf-Verley reduction followed by dehydration. Zr-containing zeolites were especially active catalysts. Surprisingly, Zr-HY was more active than Zr-Beta or mesoporous Zr-MSU. The effect of pore size, hydrophobicity and co-solvent has been investigated. Pyridine poisoning revealed that weak Lewis acid sites can catalyze the MPV reduction but stronger acid sites are required for the dehydration. The hydrophobicity and the ratio of open/closed Zr sites were higher for Zr-HY than Zr-Beta. Adding a moderately polar co-solvent like p -xylene more than doubled the reaction rate compared to only 2-pentanol as solvent. For an efficient cascade reaction, a hydrophobic catalyst with large micropores is required which combines hydrogen transfer and dehydration activities, together with an inert co-solvent that balances the concentration of both substrates inside the zeolite. [ABSTRACT FROM AUTHOR]

A wide array of polysubstituted 1‐bromo and chloronaphthalenes are obtained from coupling of allylbenzenes and polyhalomethanes. The reaction is mediated by iron metal under visible light irradiation and proceeds via a Kharasch addition intermediate followed by intramolecular FeIII mediated Friedel‐Crafts alkylation, with the formation of two Csp2−Csp2 bonds in the process. This method gives easy access to 1‐halonaphthalenes with substituent(s) at C‐5 to C‐8 that are otherwise hard to synthesize. [ABSTRACT FROM AUTHOR]

Butadiene is an important monomer for synthetic rubbers. Currently, the annual demand of ∼16 million tonnes is satisfied by butadiene produced as a byproduct of steam naphtha cracking where ethylene and propylene are the main products. The availability of large amounts of shale gas and condensates in the USA since about 2008 has led to a change in the cracker feed from naphtha to ethane and propane, affecting the amount of butadiene obtained. This has provided the impetus to look into direct processes for butadiene production. One option is the eco‐friendly conversion of (bio) ethanol to butadiene (ETB). This process had been developed in the 1930s in the then Soviet Union. It was operated on a large scale in USA during World War II but has since been abandoned in favour of petroleum‐based processes. The current trend, driven both by the availability of the raw material and ecological considerations, may make this process feasible again, particularly if the catalytic systems can be improved. This critical review discusses recent catalysts for the ETB process with special focus on the development since 2014, benchmarking them against earlier systems with a large database of operational experience. [ABSTRACT FROM AUTHOR]

γ‐Zirconium phosphate (γ‐ZrP) has potential as a very useful inorganic ion‐exchanger due to its stability under thermal and acidic conditions. We recently reported its facile synthesis using a modified solventless method, which could make the exploitation of its ion‐exchange properties for cleanup of radioactive materials and extraction of valuable ions feasible. The adsorption isotherms of Rb+ and Sr2+ over γ‐ZrP are described well with the Langmuir model, with maximum adsorption capacity of 1.52 and 1.31 mmol/g, respectively. Both ions adsorb on γ‐ZrP following pseudo‐second order kinetics with a much faster uptake of Rb+ than of Sr2+. γ‐Zirconium phosphate shows very high affinity for Rb+, allowing its enrichment from low‐concentration solutions. Notably, Rb+ is selectively removed from complex solutions containing large amounts of Na+, Mg2+, Ca2+, or transition metals such as Cu2+, Ni2+, Fe2+, Fe3+, Co2+ and Zn2+. The used sorbent can be fully regenerated by nitric acid, enabling the recovery of Rb+. [ABSTRACT FROM AUTHOR]

• A highly efficient Cu/SiO 2 catalyst for non-oxidative dehydrogenation of ethanol. • Catalyst preparation by ammonia evaporation with optimum loading lends robustness. • High yields of acetaldehyde and hydrogen using 4.37% ethanol/Heat GHSV 8895 h−1. • Long catalyst lifetimewith minimal sintering and coking. While acetaldehyde is industrially produced in the Wacker process by homogeneous catalysts, a heterogeneous catalyst is so far elusive due to rapid deactivation stemming from metal sintering and coke formation. This work reports on a highly efficient, robust and stable Cu/SiO 2 catalyst for the non-oxidative dehydrogenation of ethanol prepared by the ammonia evaporation method. The highly dispersed Cu-particles are distinguished by outstanding thermal stability with very little sintering up to 600 °C. This was attributed to the strong interactions between the copper crystallites and SiO 2 arising from the intermediately formed copper phyllosilicate phase. Deactivation due to coke formation was successfully addressed by optimizing the metal loading. The CH x /Cu ratio in the used catalyst decreased by a factor of 10 as the copper loading was increased from 0.5 to 10 wt%. Samples with Cu ≥ 10 wt% demonstrated excellent activity of > 90% ethanol conversion and > 98% acetaldehyde selectivity with no observable deactivation for up to 500 h on-stream at 280 °C and a GHSV of 8895 h−1 (34,930 ml g-1h−1). [ABSTRACT FROM AUTHOR]

Surface modification with a photosensitizer is an efficient way to improve visible light activity of wide band gap semiconductors, but is rarely applied in photocatalytic organic synthesis. Herein, we report that 2‐aminoterephthalic acid (ATA) sensitized {110}‐facetted BiOCl nanosheets, prepared by a solvothermal method, exhibit outstanding photocatalytic activity for the selective oxidative coupling of benzylamine to N‐benzylidenebenzylamine under visible light. UV‐vis diffuse reflectance spectra confirmed that the introduction of ATA extends the light absorption of wide band gap BiOCl into the visible light region. Characterization by HRTEM and SAED indicated that the samples were predominantly terminated by {110} facets. BiOCl incorporating 0.18 % ATA exhibited superior activity for the photocatalytic oxidation of benzylamine under visible light, with 100 % conversion and 100 % selectivity towards N‐benzylidenebenzylamine. The catalyst exhibited excellent recyclability and works well with other substituted benzylamines, suggesting its robust and universal nature. This work provides an example for the application of a low‐cost and highly efficient visible‐light‐responsive photocatalyst in organic synthesis. [ABSTRACT FROM AUTHOR]

An efficient method of photocatalytic degradation of methylparaben in water using Ag nanoparticles (NPs) loaded AgBr‐mesoporous‐WO3 composite photocatalyst (Ag/AgBr@m‐WO3), under visible light is presented. In this process, quantification of methylparaben in water was carried out by high‐performance liquid chromatography (HPLC) and the HPLC results showed a significant reduction of methylparaben in water due to the enhanced of photocatalytic degradation efficiency of Ag/AgBr@m‐WO3. For the material synthesis, highly ordered mesoporous‐WO3 (m‐WO3) was initially synthesized by sol–gel method and AgBr nanoparticles (NPs) were subsequently introduced in the pores of m‐WO3, and finally, the Ag nanoparticles were introduced by light irradiation. The enhanced photocatalytic degradation of methylparaben in water is attributed to the formation of surface plasmonic resonance (SPR) due to the introduction of Ag NPs on the surface of the catalyst. Also, the formation of heterojunction between AgBr and mesoporous‐WO3 in Ag/AgBr@m‐WO3 significantly inhibited the recombination of light‐induced electron‐hole pairs in the semiconductor composite. The morphological and optical characterizations of the synthesized photocatalysts (Ag/AgBr@m‐WO3) were carried out using SEM, TEM, XDR, N2 adsorption–desorption, UV‐VIS diffuse reflectance spectroscopy (DRS). Also, the photocatalytic studies using radical scavengers were carried out and the results indicated that O2·- is the main reactive species. [ABSTRACT FROM AUTHOR]

• One-pot cascade transformation of furfural to γ-valerolactone in open system. • Zr-HY is an excellent MPV catalyst for reduction of furfural and levulinate ester. • Variable combination of Lewis and Brønsted acidic sites in mixture of Zr-HY and Al-HY zeolites. • High yields of γ-valerolactone within short reaction times. A highly efficient catalyst system was developed for the one-pot transformation of furfural to γ -valerolactone (GVL) in an open system. The cascade of two Meerwein Ponndorf Verley (MPV) reductions, ring-opening and esterification reactions was catalyzed by a physical mixture of Zr- and Al-HY zeolites where the proportion and strength of Lewis and Brønsted acid sites could be independently optimized. The excellent activity of Zr-HY zeolites for the MPV reduction of furfural and levulinate ester with 2-pentanol as hydrogen donor was attributed to the larger pore size of HY-zeolites and stronger Lewis acidic sites compared to Zr-Beta. Al-HY zeolites were more effective as Brønsted acid than Al-Beta because they converted furfuryl ether to levulinate ester rather than to β -angelica lactone. The dual catalytic system comprising Zr-HY (Si/Zr 20) and Al-HY (Si/Al 6) exhibited remarkably high catalytic activity with GVL yields of 85% after only 5 h at 120 °C. [ABSTRACT FROM AUTHOR]

A silica-supported rhodium catalyst for the selective hydrogenation of phenol to cyclohexanone under mild conditions has been developed. As the Rh concentration on the catalyst increased from 0.5 to 15 wt%, the conversion (at phenol/Rh mole ratio 100/1) dropped whereas the initial selectivity to cyclohexanone increased. The direct hydrogenation to cyclohexanol occurred in parallel with partial hydrogenation to cyclohexanone. The negative correlation between selectivity and Rh dispersion suggests that direct hydrogenation occurs at low coordination sites whereas dissociation of phenol to phenoxy followed by hydrogenation to cyclohexanone takes place at higher coordinated terrace sites. DFT calculations revealed that the activation barrier for O–H bond cleavage is lower for phenol adsorbed on a Rh(1 1 1) flat surface than on small particles. By blocking the low coordination edge and step sites through grafting with (3-mercaptopropyl)trimethoxysilane, the cyclohexanone selectivity was improved from 82 to 93% at 100% conversion. The catalyst is active at room temperature and 1 atm H 2 pressure and can be easily activated by in-situ reduction. [ABSTRACT FROM AUTHOR]

A synthesis of aminothiazoles from various 1,3-dicarbonyls and thioureas without a leaving group has been developed. The reaction is photocatalyzed by tetraiodofluorescein, an organic dye. Under irradiation with green LEDs, a sulfur radical is generated in situ from thiourea, followed by addition to the enol tautomer, forming the aminothiazole backbone. This novel strategy provides a greener alternative to the traditional leaving group protocols, with excellent atom economy. [ABSTRACT FROM AUTHOR]

Forming heterojunctioned composites is an effective way to develop visible-light-driven photocatalysts. A series of BiOBr/NaBiO 3 composites were synthesized by surface transformation of NaBiO 3 with hydrobromic acid. Commensurate planes of BiOBr and NaBiO 3 enabled the formation of a closely bound interface. Composites with <20 wt.% BiOBr exhibited excellent photocatalytic activity towards the degradation of chlorophenols under low intensity visible light (λ > 400 nm). The best photocatalyst was 9% BiOBr/NaBiO 3 with a quantum yield of 0.365. No photocorrosion was observed after three cycles. Using radical scavengers and inert atmosphere, holes, superoxide and hydroxyl radicals were found to be involved in the photoactivity of the BiOBr/NaBiO 3 composite. Hydroxylated and open-ring diacid molecules were identified as intermediates in the mineralization of 4-chlorophenol. [ABSTRACT FROM AUTHOR]

Atrazine is one of the most extensively used herbicides. Being non-biodegradable in nature, it has a long half-life in water and hence it is prone to contaminate the water bodies and even seeps into the ground to pollute underground water. In this study, we developed a photocatalytic method for the degradation of Atrazine in water samples. Highly ordered mesoporous Ag-WO 3 /SBA-15 composites were tested as photocatalysts for the degradation of atrazine in water. It was found that 40% WO 3 loading rendered an optimum surface area and material content in the SBA-15 template and hence favored the enhanced photocatalytic degradation of atrazine in water. The further addition of Ag onto the WO 3 /SBA-15 composite not only made this catalyst very effective in the most sought visible region due to solar energy harvesting, but also significantly reduced the electron hole recombination as evidenced by photoluminescence studies to enhance the degradation efficiency. As a result, the Ag-WO 3 /SBA-15 composite the photo-catalytic degradation of atrazine in water under visible radiation was significantly enhanced. [ABSTRACT FROM AUTHOR]

A wide range of imidazo[1,2-a]pyridines are accessible from cheap and readily available 2-aminopyridines and 1,3-dicarbonyl compounds. [ABSTRACT FROM AUTHOR]

The acceptorless dehydrogenation of alcohols at low temperatures holds promise as a clean energy source and has been the subject of much research. In view of the thermodynamic limitations imposed by a positive Gibbs free energy, we examine the feasibility and extent of hydrogen formation from alcohol dehydrogenation using alumina-supported Ag catalysts. The results showed that in a closed system at 120 °C, the conversion of benzyl alcohol to benzaldehyde was limited by the available oxygen. The energetically demanding acceptorless route with hydrogen evolution contributed less than 2.5 % to the overall conversion. The presence of oxygen as an acceptor is vital for the progress of the reaction. In open systems even without an active influx of oxygen, alcohol dehydrogenation occurred readily but water was the main product rather than hydrogen. [ABSTRACT FROM AUTHOR]

Bismuth oxyiodide composites were synthesized and tested as photocatalysts under visible light irradiation. Calcination of bismuth oxyiodide, BiOI, at 420 °C for various lengths of time led to composites with varying compositions of BiOI and α-BiOI. The ease of forming iodide-poor bismuth oxyhalides can be attributed to ready loss of the strongly reducing iodide ion. Thermogravimetric measurements show that BiOI is not thermally stable above 350 °C. The BiOI/α-BiOI composites formed active visible-light photocatalysts for the degradation of phenol, p-chlorophenol, p-cresol, and 4- tert-butylphenol. Compared to BiOI, the rate constant for the photodegradation of phenol was 5-6 times higher over the BiOI/α-BiOI composites. The excellent activity can be attributed to the efficient separation of photogenerated charge carriers at the intimately contacted heterojunctions of the in situ-generated composites. [ABSTRACT FROM AUTHOR]

The title reaction features mild and ligand-free reaction conditions and short reaction times. [ABSTRACT FROM AUTHOR]

An extensive array of 4 H-pyrido[1,2- a]pyrimidin-4-ones have been synthesized from commercially available 2-aminopyridines and β-oxo esters with excellent yields under solvent-free conditions. The reaction, catalyzed by cheap and nontoxic BiCl3, proceeds with short reaction times under mild conditions and normal atmosphere. Only water and alcohol are formed as co-products in this green reaction. [ABSTRACT FROM AUTHOR]

Abstract: KF/γ-alumina is an effective catalyst for the aldol condensation of citral with acetone. Even at a relatively low acetone/citral ratio of 1–10, the selectivity to pseudoionones was high, ranging between 82% and 97%. X-ray diffraction shows the presence of KF and K3AlF6 crystallographic phases on the supported catalyst. At KF loadings of 3–6.75mmolg−1, a pretreatment of the catalyst by heating to 450°C was necessary to obtain an active catalyst. However, samples with KF loadings of 8.5mmolg−1 and higher were active even without pretreatment, facilitating handling and use of the catalysts. The development of (111) planes revealed by in situ XRD during the thermal activation process correlates with the activity for aldol condensation. [Copyright &y& Elsevier]

Abstract: The addition of nickel to Zr-beta gave a useful bifunctional catalyst that combines a high rate of cyclization of (±)-citronellal to isopulegols over zirconium sites and subsequent hydrogenation to menthols. The diastereoselectivity to the desired (±)-menthol was 90%. A loading of 4 wt% is optimal; lower loadings led to a low rate of hydrogenation, whereas a higher nickel loading appears to block the zirconium Lewis acid sites essential for the cyclization of citronellal. A mixture of Zr-beta and Ni/MCM-41 also formed an effective bifunctional catalyst system where the selectivity toward menthols remained high even with nickel loadings up to 15 wt%. The yield of (±)-menthol over the dual-catalyst system was 86–89% with of byproducts, citronellol and 3,7-dimethyloctanol. Besides nickel, bifunctional Rh/Zr-beta catalysts also formed menthols with selectivity , although the diastereoselectivity to (±)-menthol was lower (85%). In comparison, a 2% Pd/Zr-beta catalyst exhibited lower activity and selectivity to menthols, forming substantial amounts of 3,7-dimethyloctanal. [Copyright &y& Elsevier]

Abstract: The hydrogenation of 4-tert-butylphenol and p-cresol was investigated over Zr-beta-supported rhodium catalysts. By designing a suitable bifunctional catalyst, the intermediate, 4-alkylcyclohexanone, formed by metal-catalyzed hydrogenation of 4-alkylphenol, could be reduced via the highly stereoselective Meerwein–Ponndorf–Verley reduction over zirconium Lewis acid sites. Thus, in the presence of 2-propanol as solvent and MPV reductant, a high stereoselectivity to cis-4-alkylcyclohexanol was observed. Over 0.5% Rh/Zr-beta, 4-tert-butylphenol, and p-cresol were hydrogenated to the cis-alcohols with 95 and 89% stereoselectivity, respectively. A higher metal loading or the use of solvents such as hexane or tert-butanol led to a lower stereoselectivity, as metal-catalyzed hydrogenation predominated. Similarly, the cis:trans alcohol ratio was lower for rhodium supported on zirconia or Al-beta. Compared with rhodium, palladium was less active in the hydrogenation of the 4-alkylphenols, requiring a higher hydrogen pressure and temperature. A two-step cascade reaction mechanism is proposed for the conversion of 4-alkylphenols to cis-4-alkylcyclohexanols. [Copyright &y& Elsevier]

Abstract: The catalytic cyclisation of citronellal was studied over Zr-zeolite beta, micro/mesoporous Al-MSU-SFAU, and microporous HY catalysts. All samples showed good activity in the cyclisation of citronellal to form isopulegols with >97% selectivity. A high diastereoselectivity for (±)-isopulegol of ∼93% was observed over Zr-zeolite beta, whereas Al-MSU-SFAU and HY showed a lower selectivity of ∼65%. Zr-zeolite beta was synthesised in a range of Si/Zr of 75–200 with the use of fluoride and zeolite beta seeds. Zeolite beta with Al and Ti substitution was less active and selective than Zr-zeolite beta. The rate of reaction strongly depended on the type of solvent used, but the reaction could also be carried out without any solvent. A hydroxylated surface is important for good activity. This is consistent with the proposed mechanism, where both Lewis and Brønsted acid sites are essential for the reaction. [Copyright &y& Elsevier]

A diagram is presented on the synthesis of 4H-Pyrido[1,2-a]pyrimidin-4-ones Catalyzed by BiCl3