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In situ synthesis of gold nanoparticles on paper sheets was achieved without any external reducing reagents and heat treatments. Surface-activated pulp fibers with carboxyl and aldehyde contents of 1.18 and 0.349 mmol g-1, respectively, which were obtained from softwood kraft pulp using 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), were fabricated into paper sheets with polyamideamine epichlorohydrin (PAE) resin with a papermaking technique. The TEMPO-oxidized pulp papers were flexible, lightweight, and easy to handle in a wet state due to the PAE-mediated reinforcement. Simple immersion of the white TEMPO-oxidized paper in an aqueous solution of tetrachloroauric acid at room temperature brought about distinct color change from white to red-purple, strongly suggesting the formation of gold nanoparticles. Post-oxidized aldehyde-free paper provided no color variation, and thus the aldehyde groups on pulp fibers made a significant contribution to the in situ synthesis of gold nanoparticles. The organic-inorganic paper materials of TEMPO-oxidized pulp and gold nanoparticles demonstrated the catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol in an aqueous system. [ABSTRACT FROM AUTHOR]

The immobilization of N-sulfonyl-(Ra)-binam-d-prolinamide using polystyrene as a support allows the recovery of an efficient catalytic system for the enantioselective direct aldol reaction between different ketones and aldehydes under solvent-free or aqueous conditions. The polystyrene-supported N-sulfonyl-(Ra)-binam-d-prolinamide catalyst in combination with benzoic acid showed similar results to those obtained with unsupported N-tosyl-binam-derived prolinamide under similar reaction conditions. The aldol products were obtained at room temperature and using only 2 equivalents of the ketone with high yields, regio-, diastereo- and enantioselectivities. The aldol reaction between aldehydes can also be performed under these reaction conditions with moderate results. The recovered catalyst can be reused up to six times without having a detrimental effect on the achieved results. [ABSTRACT FROM AUTHOR]

In synthetic chemistry, the protection of aldehydes and ketones is crucial during multistep synthesis of complex molecules. Organic chemists have paid substantial attention to the synthesis of 1,3‐oxathiolanes and 1,3‐oxathianes because of their considerable stability under acidic conditions and ease of removal of protecting groups. In this paper, we report the mild and efficient oxathiacetalization of aldehydes with 2‐mercaptoethanol and 3‐mercaptopropan‐1‐ol through visible‐light‐promoted eosin‐Y catalyzed C–S and C–O bond formation at ambient temperature under metal‐free conditions. This catalytic system also affords oxathiacetalization of ketones through photoredox catalysis. [ABSTRACT FROM AUTHOR]

Silica-based mesoporous materials, such as SBA-15, are important supports in the field of catalysis due to their ordered pore channels. The traditional synthesis route of SBA-15 suffers from high autogenous pressure and explosion risks, limiting its industrial production. Herein, a reflux system under ambient pressure was used for the synthesis of SBA-15. Ni nanoparticles were incorporated into the obtained materials to evaluate the quality of the SBA-15 support. The comparative performance of Ni/SBA-15H and Ni/SBA-15R validated there was negligible difference between the SBA-15 prepared by the hydrothermal method (SBA-15H) and the reflux method (SBA-15R). This revolutionary synthesis methodology provides a novel and secure route for the large-scale preparation of SBA-15. [ABSTRACT FROM AUTHOR]

A one-pot, one-step protocol combining hydrogen transfer initiated dehydration (HTID) of 1,3-propanediol (1,3-PDO), catalysed by [Cp*IrCl2(NHC)] (Cp* = pentamethylcyclopentadienyl; NHC = carbene ligand) complexes (1-5H and 1-3F), and self-aldol condensation (SAC) of propanal (2), allowed selective production of C6 aldehyde 2-methyl-pent-2-enal (3), in ionic liquids with high substrate conversion. This shows, for the first time, the conversion of 1,3-propanediol to C6 aldehydes in one pot via a catalytic hydrogen borrowing methodology. The Ir(III) pre-catalysts and the ionic liquids were recyclable. C6 aldehyde 2-methyl-pent-2-enal could also be selectively produced in the presence of water and in neat 1,3-PDO. The efficient, selective delivery of a value-added chemical from 1,3-PDO, a major product of many whole-cell bacterial fermentation processes, shows that the combination of chemo-catalytic processing of the chemical platform via Cp*IrCl2(NHC)-catalysed HTID/SAC with bio-catalysis has the potential to allow direct valorisation of the bio-renewable feedstocks, such as waste glycerol and sugars, into valuable chemicals. [ABSTRACT FROM AUTHOR]

The present paper reports on the use of CeO2 materials supported palladium chloride catalyst for selectively oxidising organic alcohols into aldehydes. Spherical, microsized rod-shaped and spindle-like CeO2 particles are synthesised and characterised by SEM. The catalysts are prepared by loading palladium chloride onto the CeO2 support matrix. A complete characterization of the catalysts is performed. The activity of catalysts is studied by the selective oxidation of various alcohols. The results show that (1) the catalytic activities prepared by spherical cerium are superior to the catalysts prepared by spindle-like or rod-shaped cerium and (2) the catalyst PdCl2/CeO2 (nanospheres) show good activity, high yield, and good stability. [ABSTRACT FROM AUTHOR]

Gallium hydrides stabilised by primary and secondary amines are scarce due to their propensity to eliminate dihydrogen. Consequently, their reactivity has received limited attention. The synthesis of two novel gallium hydride complexes HGa(THF)[ON(H)O] and H2Ga[μ2‐ON(H)O]Ga[ON(H)O] ([ON(H)O]2−=N,N‐bis(3,5‐di‐tert‐butyl‐2‐phenoxy)amine) is described and their reactivity towards aldehydes and ketones is explored. These reactions afford alkoxide‐bridged dimers through 1,2‐hydrogallation reactions. The gallium hydrides can be regenerated through Ga−O/B−H metathesis from the reaction of such dimers with pinacol borane (HBpin) or 9‐borabicyclo[3.3.1]nonane (9‐BBN). These observations allowed us to target the catalytic reduction of carbonyl substrates (aldehydes, ketones and carbon dioxide) with low catalyst loadings at room temperature. [ABSTRACT FROM AUTHOR]

The family of polyoxometalate (POM) intercalated layered double hydroxide (LDH) composite materials has shown great promise for the design of functional materials with numerous applications. It is known that intercalation of the classical Keggin polyoxometalate (POM) of [PW12O40]3− (PW12) into layered double hydroxides (LDHs) is very unlikely to take place by conventional ion exchange methods due to spatial and geometrical restrictions. In this paper, such an intercalated compound of Mg0.73Al0.22(OH)2 [PW12O40]0.04⋅0.98 H2O (Mg3Al-PW12) has been successfully obtained by applying a spontaneous flocculation method. The Mg3Al-PW12 has been fully characterized by using a wide range of methods (XRD, SEM, TEM, XPS, EDX, XPS, FT-IR, NMR, BET). XRD patterns of Mg3Al-PW12 exhibit no impurity phase usually observed next to the (003) diffraction peak. Subsequent application of the Mg3Al-PW12 as catalyst in Knoevenagel condensation reactions of various aldehydes and ketones with Z-CH2-Z′ type substrates (ethyl cyanoacetate and malononitrile) at 60 °C in mixed solvents ( V2-propanol: Vwater=2:1) demonstrated highly efficient catalytic activity. The synergistic effect between the acidic and basic sites of the Mg3Al-PW12 composite proved to be crucial for the efficiency of the condensation reactions. Additionally, the Mg3Al-PW12-catalyzed Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate demonstrated the highest turnover number (TON) of 47 980 reported so far for this reaction. [ABSTRACT FROM AUTHOR]

A straightforward and efficient C(sp2)–H acylation of enamides with aldehydes via transition-metal-free photoredox catalysis is demonstrated. The transformation proceeded smoothly without resorting to expensive and potentially toxic iridium or ruthenium polypyridyl-based photocatalysts under mild conditions, furnishing a diverse range of synthetically crucial, geometrically defined β-acylated enamides in a stereoselective and regioselective manner. [ABSTRACT FROM AUTHOR]

This paper describes the development of a palladium-catalyzed decarboxylative inter- and intramolecular condensation reaction of isoxazol-5(4 H)-ones with carbonyl compounds in the presence of PPh3, giving various 2-azabuta-1,3-dienes or pyrroles in moderate to high yields. [ABSTRACT FROM AUTHOR]

An efficient and convenient method for the preparation of 3-benzylquinazolin-4(1H)-one derivatives under solvent-free and catalyst-free conditions by the reaction of isatoic anhydride, benzylamine, and aromatic aldehydes was reported. In reported papers, ammonia water, ammonium salt, and aromatic amine were often used to synthesize quinazolin-4(1H)-one derivative, but benzylamine was seldom used in this synthesis. This article offers a green method for the synthesis of 3-benzylquinazolin-4(1H)-one derivative used benzylamine as starting material. This methodology has the advantages of short reaction time, mild reaction conditions, easy work-up, and environmental friendliness. [ABSTRACT FROM AUTHOR]

The oxidative esterification of various aldehydes with alcohols could be achieved by a heterogeneous iron(III) catalyst supported on a ring-like POM inorganic ligand under mild conditions, affording the corresponding esters, including several drug molecules and natural products, in high yields. ESI-MS and control experiments demonstrated that POM-FeV(＝O) was the active catalytic species and the plausible mechanism was presented. More importantly, the 6th run of the iron catalyst recycles shows only a slight decrease in the yield. [ABSTRACT FROM AUTHOR]

Trifluoroacetic acid as an efficient catalyst promoting the Dakin-West reaction at ambient temperature is reported for the first time in this paper. A few efficacious auxiliary catalysts were also developed for the Dakin-West reaction. A variety of substituted aryl aldehydes and aryl ketones were found to be applicable to the preparation of some new β-acetamido-β-arylpropiophenones. This procedure has several advantages such as high yields, short reaction time, and smaller amount (0.30 mol%) of catalyst. [ABSTRACT FROM AUTHOR]

It is already known that phenolic monomers bearing electron-withdrawing groups could hardly be polymerized by oxireductases. In this paper, enzymatic polymerization (EP) of phenolic monomers possessing electron-withdrawing aldehyde side-groups, protocatechualdehyde (PCA) and pyrogallolaldehyde (PGA), is presented. The monomers were converted to their polymers via enzyme-catalyzed oxidative polymerization in buffered-dioxane solution using horseradish peroxidase as the catalyst and hydrogen peroxide as the oxidant. The resulting products (abbreviated as PPCA and PPGA) were characterized by means of UVVis, FT-IR, 1H-NMR, GPC (gel-permeation chromatography), TG-DTA and DSC analyses. IR and NMR data indicated that the obtained polymers consisted of a mixture of phenylene/oxyphenylene units, and the aldehyde (-CH=O) side-groups in the polymer chains were not oxidized. The electrical and electrochemical characterizations of the polymers were performed by solid-state conductivity and cyclic voltammetry (CV) techniques, respectively. Fluorescence analyses of PGA and PPGA were also conducted in DMSO. Emission maxima of PPGA were red shifted by nearly 34 nm compared to its monomer. [ABSTRACT FROM AUTHOR]

For the first time, a reductive alkylation process in continuous flow has been elaborated for the conversion of bio-based alcohols and aldehydes into symmetrical and dissymmetrical high-value-added ethers for industrial companies. The developed method is an etherification associating liquid, solid and gas phases under green conditions (continuous flow, catalysis, bio-based starting materials). [ABSTRACT FROM AUTHOR]

We herein describe an asymmetric α-allylic allenylation of β-ketocarbonyls and aldehydes with 1,3-enynes. A synergistic chiral primary amine/Pd catalyst was identified to facilitate the utilization of 1,3-enynes as atom-economic and achiral allene precursors. The synergistic catalysis enables the construction of all-carbon quaternary centers-tethered allenes bearing non-adjacent 1,3-axial central stereogenic centers in high level of diastereo- and enantio-selectivity. By switching the configurations of ligands and aminocatalysts, diastereodivergence can be achieved and any of the four diastereoisomers can be accessed in high diastereo- and enantio- selectivity. Enantioselective α-allylic allenylation of carbonyls is a straightforward approach to access chiral allenes that are of significant relevance as synthons and bio-active products. Here, the Luo group describe an asymmetric α-allylic allenylation of β-ketocarbonyls and aldehydes with 1,3-enynes, via a combined chiral primary amine and palladium catalyst system. [ABSTRACT FROM AUTHOR]

This paper describes the catalytic activity of air stable and easy to handle manganese complexes towards the hydrosilylation of aldehydes. These catalysts incorporate a bulky diazabutadiene ligand and exhibit good functional group tolerance and chemoselectivity in the hydrosilylation of aldehydes, utilizing primary silanes as the reducing agent. The reactions proceed with turnover frequencies approaching 150 h−1 in some instances, similar to those observed for other manganese-based catalysts. The conversion of aromatic aldehydes to the corresponding alcohols was found to be more efficient than that for the analogous aliphatic systems. [ABSTRACT FROM AUTHOR]

Disodium phosphate catalyzed one-pot synthesis of 3,4-dihydropyrano[3,2-c]chromenes, from aldehydes, active methylene compounds malononitrile and 4-hydroxycoumarin in ethanol:water (1:1) under reflux temperature. The attractive features of this process are inexpensive, efficient, as well as user friendly. [ABSTRACT FROM AUTHOR]

Three cyclic zinc(II) bis-porphyrins ( CB) with highly flexible linkers are employed as artificial molecular containers that efficiently encapsulate/coordinate various aromatic aldehydes within their cavities. Interestingly, the arrangements of guests and their reactivity inside the molecular clefts are significantly influenced by the cavity size of the cyclic containers. In the presence of polycyclic aromatic aldehydes, such as 3-formylperylene, as a guest, the cyclic bis-porphyrin host with a smaller cavity ( CB1) forms a 1:1 sandwich complex. Upon slightly increasing the spacer length and thereby the cavity size, the cyclic host ( CB2) encapsulates two molecules of 3-formylperylene that are also stacked together due to strong π-π interactions between them and CH-π interactions with the porphyrin rings. However, in the cyclic host ( CB3) with an even larger cavity, two metal centers of the bis-porphyrin axially coordinate two molecules of 3-formylperylene within its cavity. Different arrangements of guest inside the cyclic bis-porphyrin hosts are investigated by using UV/Vis, ESI-MS, and 1H NMR spectroscopy, along with X-ray structure determination of the host-guest complexes. Moreover, strong binding of guests within the cyclic bis-porphyrin hosts support the robust nature of the host-guest assemblies in solution. Such preferential binding of the bis-porphyrinic cavity towards aromatic aldehydes through encapsulation/coordination has been employed successfully to catalyze the Knoevenagel condensation of a series of polycyclic aldehydes with active methylene compounds (such as Meldrum's acid and 1, 3-dimethylbarbituric acid) under ambient conditions. Interestingly, the yields of the condensed products significantly increase upon increasing spacer lengths of the cyclic bis-porphyrins because more substrates can then be encapsulated within the cavity. Such controllable cavity size of the cyclic containers has profound implications for constructing highly functional and modular enzyme mimics. [ABSTRACT FROM AUTHOR]

A highly selective, solvent-free process for the acetalisation of aldehydes was achieved by the use of a readily accessible antimony(v) catalyst which we previously prepared in our lab as a tetraarylstibonium triflate salt ([1][OTf]). High yields of the acetals were achieved in the presence of stoichimetric amounts of either triethoxymethane or triethoxysilane. It was found that triethoxymethane reactions required longer time to reach completion when compared to triethoxysilane reactions which were completed upon mixing of the reagents. The products can be easily separated from the catalyst by distillation which enabled further use of [1][OTf] in additional calytic reactions (up to 6 cycles). Moreover, [1]+ also catalyzed the deprotection of the acetals into their corresponding aldehydes using only water as a solvent. [ABSTRACT FROM AUTHOR]

The Prins reaction is an efficient method for the direct generation of 1,3-dioxanes from alkenes and aldehydes. As first published in 2008, this process can be effected by stoichiometric amounts of molecular iodine. We herein report a catalytic protocol allowing the use of iodine at low loading (0.5-5 mol%), smoothly effecting the condensation of styrenes with aliphatic aldehydes to rac-1,3-dioxanes. Moreover, this mild catalytic system effects the isomerization of the 1,3-dioxane products to the thermodynamically favored one. As a result, substituted rac-1,3-dioxanes were prepared in high yields (up to 92%), and with high diastereoselectivities (d.r. up to 82:18). For the application of iodine in catalytic amounts, the addition of pyridinium bis(trifluoromethanesulfonyl) imide (TFSI) salts in a 1:1 ratio to iodine is the key to success. [ABSTRACT FROM AUTHOR]

The transoximation reaction enables the transfer of an oxime to a carbonyl compound and is catalyzed by transoximase in the pupae of the silkworm. Inspired by this bio-synthetic pathway, we achieved the transoximation of oximes to aldehydes and ketones catalyzed by a Brønsted acid under mild conditions. Hydroxylamine salt, which necessitates a stoichiometric amount of base, was not required. NMR analysis clarified that this reaction proceeded through hydroxylamines generated by the successive hydrolysis of the oxime in situ. In addition, an environmentally benign method for catalytic transoximation was demonstrated in aqueous medium on a one hundred gram scale and the reaction filtrate containing the catalyst was recovered and reused over 10 times. [ABSTRACT FROM AUTHOR]

Anthracene-based ligand L1 comprising an imine functionality and a tellurium (Te) donor moiety has been prepared. This ligand L1 has been characterized using 1H, 13C and 125Te NMR spectroscopic techniques. The novel palladium(II) complex 1 and ruthenium(II) complex 2 have been synthesized by reacting organotellurium ligand L1 and Na2PdCl4/[Ru p(cymene)Cl2]2, respectively. The Pd(II) complex 1 and Ru(II) complex 2 were characterized with high resolution mass spectrometry (HR-MS) and 125Te NMR spectra. The molecular structures of complexes 1 and 2 were authenticated with single crystal X-ray diffraction. Both the complexes are thermally stable, robust, and air and moisture insensitive. Palladium complex 1 exhibits nearly square planar geometry. The molecular structure of complex 2 has a pseudo-octahedral half sandwich piano-stool geometry around ruthenium. The catalytic activity of complex 1 has been explored for O-arylation of phenol, whereas the catalytic activity of complex 2 was explored for aldehyde to amide conversion. A variety of structurally different chloroarenes have been coupled with phenol employing 1 as a catalyst. A wide range of aldehydes containing different functional groups (viz. H, –Me, –NO2, F, OMe, Cl and Br at the para position) were readily converted into their corresponding amide by employing Ru(II) complex 2 as a catalyst in a reaction time of 12 hours. [ABSTRACT FROM AUTHOR]

A mechanistic investigation, which included a Hammett correlation analysis, evaluation of the effect of variation of catalyst composition, and low-temperature NMR spectroscopy studies, of the Lewis acid-Lewis base catalyzed addition of acetyl cyanide to prochiral aldehydes provides support for a reaction route that involves Lewis base activation of the acyl cyanide with formation of a potent acylating agent and cyanide ion. The cyanide ion adds to the carbonyl group of the Lewis acid activated aldehyde. O-Acylation by the acylated Lewis base to form the final cyanohydrin ester occurs prior to decomplexation from titanium. For less reactive aldehydes, the addition of cyanide is the rate-determining step, whereas, for more reactive, electron-deficient aldehydes, cyanide addition is rapid and reversible and is followed by rate-limiting acylation. The resting state of the catalyst lies outside the catalytic cycle and is believed to be a monomeric titanium complex with two alcoholate ligands, which only slowly converts into the product. [ABSTRACT FROM AUTHOR]

Syntheses of N‐heterocyclic compounds that permit a flexible introduction of various substitution patterns by using inexpensive and diversely available starting materials are highly desirable. Easy to handle and reusable catalysts based on earth‐abundant metals are especially attractive for these syntheses. We report here on the synthesis of 3,4‐dihydro‐2H‐pyrroles via the hydrogenation and cyclization of nitro ketones. The latter are easily accessible from three components: a ketone, an aldehyde and a nitroalkane. Our reaction has a broad scope and 23 of the 33 products synthesized are compounds which have not yet been reported. The key to the general hydrogenation/cyclization reaction is a highly active, selective and reusable nickel catalyst, which was identified from a library of 24 earth‐abundant metal catalysts. [ABSTRACT FROM AUTHOR]

A simple iron- and silyl chloride catalyzed method for the preparation of symmetrical and nonsymmetrical ethers is presented. Various aldehydes and ketones were reductively etherified by using triethylsilane as a reducing agent in the presence of 2 mol% of iron(III) oxo acetate and 8 mol% of chloro(trimethyl)silane. The reactions can be carried out at ambient temperatures and pressures with ethyl acetate as the solvent. [ABSTRACT FROM AUTHOR]

Transfer hydrogenation has become a versatile and practical method for reduction in organic synthesis. The development of aqueous transfer hydrogenation reactions is not only fundamentally interesting in terms of understanding enzymatic catalysis, but also offers economic and environmental benefits, as water is cheap and nontoxic. In this review paper, an account of the work on transfer hydrogenation in aqueous media done by the Xiao group is given. Aqueous transfer hydrogenation of ketones, aldehydes and heterocycles as well as reductive amination reactions, including extension into biomass-derived platform molecules, has been successfully developed employing the classical Noyori-type catalysts or the newly invented iridacycles, with most of the reactions taking place “on water”. Water is shown to be an enabling medium for transfer hydrogenation reactions of various features. Not only can it accelerate a reduction, it also provides a simple tool, the solution pH, to control a reaction. [ABSTRACT FROM AUTHOR]

An efficient and practical method for the one-pot Mannich reaction of aromatic ketones with aldehydes and amines at room temperature has been developed under solvent-free conditions catalyzed by (C4H12N2)2[BiCl6]Cl·H2O (3 mol%). The catalyst may also be recycled multiple times by simple isolation protocols without compromising the catalytic efficiency. [ABSTRACT FROM AUTHOR]