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A protocol for InIII and CuI co‐catalyzed synthesis of a wide array of arylimidazopyridine carboxylates by three components coupling of benzaldehydes, malonic esters and 2‐aminopyridines is described. The reaction proceeds through a reaction cascade of Knoevenagel condensation, 1,4‐conjugate addition, aerobic dehydrogenation, Ortoleva‐King reaction and decarboxylation. Multiple C−N and C−C bond formations in addition to multiple C−C, C−H, C−O, and N−H bond cleavages are involved in forming the product. [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]

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]

Abstract: Anethole is an ingredient in many flavours, fragrances and pharmaceutical formulations. To reduce the dependence of its supply on natural oils, a green route for anethole synthesis was designed on the basis of Meerwein–Pondorf–Verley (MPV) reduction and dehydration of 4′‐methoxypropiophenone. The one‐pot cascade reactions were heterogeneously catalysed by dual‐functional Zr‐MSU‐3, a predominantly Lewis‐acidic catalyst with a Si/Zr ratio of 10 and pores with sizes in the range of 3.2–4.2 nm. The use of 2‐pentanol as solvent and hydrogen donor for the MPV reduction was advantageous, as its high boiling point enhances the rate of the reactions, especially the dehydration of the MPV product, 1‐(4‐methoxyphenyl)‐propan‐1‐ol. This dispenses with the need for a strong acid catalyst that could result in by‐products of acid‐catalysed reactions. Anethole yields of 91 % with a trans/cis isomer ratio of about 92:8, similar to that of natural anethole, were obtained. In comparison, microporous Zr‐beta (Si/Zr 12.5) gave lower activity owing to pore‐size constraints. Hence, through design of the reactions and catalyst, 4′‐methoxypropiophenone can be efficiently converted to anethole in a sustainable and green manner. [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]

Zirconium phosphates have potential applications in areas of ion exchange, catalysis, photochemistry, and biotechnology. However, synthesis methodologies to form crystalline α-zirconium phosphate (Zr(HPO4)2⋅H2O) typically involve the use of excess phosphoric acid, addition of HF or oxalic acid and long reflux times or hydrothermal conditions. A minimalistic sustainable route to its synthesis has been developed by using only zirconium oxychloride and concentrated phosphoric acid to form highly crystalline α-zirconium phosphate within hours. The morphology can be changed from platelets to rod-shaped particles by fluoride addition. By varying the temperature and time, α-zirconium phosphate with particle sizes from nanometers to microns can be obtained. Key features of this minimal solvent synthesis are the excellent yields obtained with high atom economy under mild conditions and ease of scalability. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

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]

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]

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]

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]