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The possible catalytic mechanism was proposed and studied comprehensively at the M062X/6-31G(d,p) level of theory for a reported chemoselective intermolecular SN2 nucleophilic substitution of aldehydes with alkanolamine. The calculated results show that the catalytic cycle occurs through six stages, namely, the nucleophilic attack of active N-heterocyclic carbene (NHC) on the substrate, generation of the Breslow intermediate, oxidative addition of NBS and alkanolamine, SN2 nucleophilic substitution, Et3N-assisted debromination, and finally regeneration of the NHC along with the release of the product. The results show that TSs of the C–N or C–O bond formation is the key transition state that determines the chemoselectivity of the title reaction. Moreover, our results demonstrated that the N-bromoamine intermediate is more favorable both thermodynamically and kinetically than hypobromite by 14.2 kcal mol−1, which is consistent with the fact that only the N-acylation product was observed in the experiment. In addition, we found that alkanolamine not only acts as a reactant but also as a proton-shuttle and stabilizer to stabilize the structure of the favored chemoselective transition state by multiple N–H⋯N, N–H⋯O and C–H⋯Br− noncovalent interactions. Et3N firstly acts as a base to promote the formation of the active catalyst NHC, then the protonated Et3N acts as a proton-shuttle to accelerate the Breslow intermediate formation and decrease the activation barrier. The Parr functions and frontier molecular orbital analyses of key species indicate that NHC remarkably enhances the nucleophilicity of the substrate aldehyde, leading to a significant increase of the HOMO energy and a moderate increase of the LUMO energy. We hope this work could provide deeper insights into the fundamental mechanisms of the Et3N-assisted NHC-catalyzed SN2 substitution reactions. [ABSTRACT FROM AUTHOR]

We designed a robust and efficient greener synthetic protocol to access p-quinone fused 5-substituted-1,4-benzodiazepine scaffolds, a new molecular hybrid, through InCl3 mediated Pictet–Spengler type cycloannulation of 2-amino-3-arylamino-p-quinone and commercially prevalent aldehydes. This protocol would ease access to privileged redox-active p-quinone fused seven-membered frameworks that are difficult to access by other protocols and would find potential applications in biological and electrochemical research. [ABSTRACT FROM AUTHOR]

A metal-free C–H functionalization of purines with aldehydes was developed to access C6-acylated purines via green radical reactions. Theoretically, there are many competitive reactions due to the three C–H bonds (C2–H, C6–H, C8–H) in the purine, and the acylation only happens at the purinyl C6-position. This method avoids a metal catalyst and provides a green approach to construct C–C (sp2) bonds at the purinyl C6-position, while maintaining excellent compatibility with various functional groups. Moreover, the protocol features broad substrate scope and easy scale-up. The transformation of the product demonstrates the significant practical value of the method. The primary mechanism was proposed based on controlled experiments. [ABSTRACT FROM AUTHOR]

A convenient method for Z → E geometry isomerization of aryl–aryl (stilbenes), alkyl–aryl, and alkyl–alkyl alkenes was developed. This user-friendly method utilized a popular commercial Hoveyda–Grubbs ruthenium olefin metathesis catalyst in the presence of sodium formate in toluene and is characterized by good functional group compatibility, including halogen, ester, aldehyde, and acetal functions. This research originated from trials on the valorization of a waste by-product resulting from the industrial synthesis of a valuable API—rosuvastatin. [ABSTRACT FROM AUTHOR]

A green and efficient method for the construction of functionalized 2,3-dihydrothiophene derivatives in water was reported. In this work, Novozym 435 acted as a remarkable biocatalyst in catalyzing the four-component reaction of aldehydes, malonitrile or ethyl cyanoacetate, 1,3-thiazolidinedione, and amines under mild conditions. Excellent yields (85–95%) of all the corresponding products could be obtained in reasonable reaction time. Moreover, Novozym 435 could be reused for six cycles with a yield of at least 80%. The rationality of this multicomponent reaction mechanism was also verified via control experiments. [ABSTRACT FROM AUTHOR]

In this study, three novel binuclear, distinctly defined, air-stable cobalt(II) complexes, denoted by the formulas [Co(H2L1)]2(1), [Co(H2L2)]2(2) and [Co(H2L3)]2(3), are reported. Binuclear cobalt(II) complexes (1–3) namely bis-[3,3′-bis[(2,6-dimethyl-phenylimino)-methyl]-[1,1′]-biphenyl-2,2′-dioxo cobalt(II)] (1), bis-[3,3′-bis[(2,6-di-i-sopropylphenyl)imino)methyl)-[1,1′-biphenyl]-2,2′-dioxodicobalt(II)] (2) and bis-[3,3′-bis[(2,6-diethyl-phenylimino)-ethyl]-[1,1′]-biphenyl-2,2′-dioxo cobalt(II)] (3) were synthesised and isolated for the first time. Several techniques, including mass spectrometry, UV-visible spectra, FT-IR spectra, elemental analysis, and single-crystal X-ray diffraction, were used to ascertain the structural properties of the binuclear cobalt(II) complexes. All these binuclear cobalt(II) [Co(H2L1)]2, [Co(H2L2)]2 and [Co(H2L3)]2 complexes (1–3) demonstrated excellent catalytic activity for the acceptor-less dehydrogenation (AD) reaction of primary alcohols to create the corresponding aldehydes and molecular hydrogen (H2). Multiple alcohols, including those that are electron-rich/electron-poor primary alcohols, have been successfully converted into the corresponding aldehydes using catalytic acceptor-less dehydrogenation (CAD), which only produces molecular hydrogen as a byproduct. [ABSTRACT FROM AUTHOR]

Acylethynylpyrroles, readily available from acylbromoacetylenes and pyrroles, smoothly undergo [3+2]-cyclization with ketones and aldehydes (room temperature) to give acylmethylidenepyrrolo[1,2-c]oxazoles. The reaction protocol meets the principles of the PASE (pot, atom, and step economy) paradigm to afford various pyrrolo[1,2-c]oxazoles, including spirocyclic ones, in up to 82% yield. [ABSTRACT FROM AUTHOR]

In this study, a novel magnetically recoverable Fe3O4@SiO2–BenzIm-Fc[Cl]/BiOCl nano-composite was synthesized using a simple chemical co-precipitation method. This is the first time that a magnetic nano-catalyst bearing ionic liquid, ferrocene and BiOCl is synthesized. The Fe3O4@SiO2–BenzIm-Fc[Cl]/BiOCl nano-composite was characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and field emission scanning electron microscopy (FE-SEM) techniques. The catalytic activities of the novel magnetic nano-composite were evaluated in one-pot three-component synthesis of a wide variety of 2-amino-3-cyano-4H-chromene derivatives under ultrasound irradiation. A simple, facile and highly efficient ultrasound-assisted method was developed to synthesize 4H-chromene derivatives via one-pot, three-component reaction of aldehyde, malononitrile and active phenolic compounds (2-naphthol, 1-naphthol, 3-(dimethylamino)phenol, resorcinol and orcinol) at room temperature. The reaction of aldehyde, malononitrile and orcinol is newly introduced in this paper. The ultrasound-assisted synthesis protocol that was studied in this article exhibits some notable advantages such as short reaction times, operational simplicity, green reaction conditions, high yields and easy work-up and purification steps. In addition, the novel magnetic nano-composite could be easily recovered by an external magnetic field and reused for six-reaction cycles without significant loss of its catalytic activity. [ABSTRACT FROM AUTHOR]

The unique and highly tunable photophysical, photochemical and photoredox properties of porphyrins contribute to their versatile applications in alternate energy generation, sensing, and therapeutic fields. The synthetic route for meso substituted porphyrins involves acid-catalysed condensation of aldehyde and pyrrole followed by oxidation. Herein, we report an environmentally benign novel approach for the synthesis of substituted tetraaryl porphyrins using acetonitrile as the solvent and Keggin type phosphovanadotungstic acid as the catalyst. The simple one-pot strategy completely avoids the usage of acidic/chlorinated solvents and expensive oxidising agents. A reasonable spectroscopic yield of around 12–39% could be obtained for various derivatives under the optimised conditions. [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]

We report a Cu(I)-catalyzed synthesis of quinazolines via cascade cyclization/hydrodehalogenation by using acetamide as a nitrogen source and H2O as a hydrogen source. The current reaction provides a unified modular route from readily available starting materials to quinazolines in which aryl aldehydes can be decorated with diverse substitutions. In this reaction, acetamide becomes an interesting alternative for the unpleasant smelling ammonia and toxic amidines. [ABSTRACT FROM AUTHOR]

Ligand-free reductive coupling of aldehydes with 1,3-dienes was successfully developed using the nickel nanoparticle catalyst SANi (sulfur-modified Au-supported nickel). Leakage of nickel species into the reaction solution is minimal. SANi can be used repeatedly and the reaction is an environmentally benign reaction. [ABSTRACT FROM AUTHOR]

A concise and practical approach for expedient synthesis of substituted benzoxazolpyrroles, benzothiazolpyrroles and indolizines by three-component cascade annulative coupling of an aldehyde, 2-heteroaryl acetonitrile and an isocyanide in the presence of 10 mol% 2-(hydroxymethyl)pyrrolidinium acetate has been devised in high yields for the first time. The compatibility with a wide range of functional groups makes this domino formation of one C-C and two C-N bonds interesting. In particular, the heterocycles derived from 2-bromobenzaldehydes are further converted into indole-fused novel pentacyclic (6-5-5-5-6) heteroaromatic compounds by Pd(II)-catalyzed intramolecular N-arylation via a cross-dehydrobromination reaction. This annulative protocol not only provides an efficient method to access tricyclic heteroaromatics, but also enriches the research domain of pentacyclic scaffolds. [ABSTRACT FROM AUTHOR]

In this work, a simple and stepwise strategy has been adopted for the successful synthesis of diamine functionalized porous graphene oxide sheets decorated with ultra-small palladium oxide nanoparticles. The successful synthesis, stepwise functionalization, morphology and elemental composition have been authenticated by using numerous physicochemical characterization techniques such as FT-IR, TGA, powder XRD, SEM, HR-TEM, EDAX, elemental mapping, CHNS, ICP-MS and XPS analyses. The prepared nano-catalyst has been employed as a recyclable catalyst for the oxidative amidation of aldehydes with amines. The main features of this nano-catalyst include mild reaction conditions, simple work-up procedure, high product yield without any hazardous by-products and recyclability for several catalytic cycles. It could be believed that the unique porous architecture of the nano-catalyst was responsible for the enhanced specific surface area which favors a quick response and improved interaction between the catalytic active moieties and the reactants. [ABSTRACT FROM AUTHOR]

A rhodium(I)-catalyzed regioselective hydroacylation of alkenyl-bearing allylic alcohols with simple aldehydes for the preparation of diverse 1,5-diketones is described. Mechanistic investigation suggests that this transformation might proceed through redox isomerization of the allylic alcohol followed by hydroacylation of the resulting enone with aldehyde involving a stable six-membered rhodacycle intermediate. This protocol highlights the role of in situ generated carbonyl group in controlling the site-selectivity of the intramolecular alkene moiety. [ABSTRACT FROM AUTHOR]

Oxazoles are among the most important heterocyclic scaffolds in the fields of natural products and medicinal chemistry. Herein is developed a tandem reaction for the synthesis of a diverse array of 4,5-difunctionalized oxazoles utilizing easily-accessible ethyl 2-isocyanoacetate and aldehydes (26 examples, 31–83% yields). This cascade reaction is facilitated by catalytic CuBr and molecular oxygen as the oxidant. The process involves a catalytic cycloaddition oxidative dehydroaromatization mechanism. The broad aldehyde substrate scope, mild reaction conditions, and atom economy make this protocol an attractive alternative to access functionalized oxazoles. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of twelve Rh(I) complexes with fluorinated NHC ligands are described. Seven molecular structures of these complexes were unequivocally elucidated by single crystal X-ray diffraction techniques. In all cases the metal center showed a distorted square planar geometry; including a chloride, a 1,5-cyclooctadiene and an NHC ligand coordinated to the Rh(I) center. Furthermore, the catalytic activity of the series of complexes was explored in the arylation of aldehydes, finding that the catalytic activity of the complexes is related to the number of fluorine atoms present on their structures, showing that as more fluorine atoms are found in the NHC ligand, the complexes become more active. This observation can be correlated with the fact that increasing the number of fluorine atoms in the NHC makes it a less electron-donating ligand, thus favoring the arylation of aldehydes. [ABSTRACT FROM AUTHOR]

A new strategy has been proposed for synthesizing Co@CoO core–shell nanoparticles with a core–shell structure, which involves a facile solvent-thermal process in deep eutectic solvents (DESs). In contrast to the irregular sheet-like packing material obtained in water, twinned and 3D-ellipsoid-shaped nanoparticles were achieved in choline chloride (ChCl)/glycerol and ChCl/PEG-300, respectively. It was found that the nanoparticles were featured as metal Co(0) cores homogeneously wrapped by CoO shells after reduction under a H2 atmosphere. The Co@CoO core–shell nanoparticles showed good activity and stability for the hydroformylation of olefins, and the conversion of 1-octene can reach 99% at 130 °C under 4 MPa (CO/H2 = 1) pressure, and the selectivity to C9 aldehydes was reached up to 97%. The characterization by XPS, H2-TPR and HRTEM indicated that metal Co(0) species could be an active site for hydroformylation of olefins. Notably, the leaching of cobalt carbonyl species was highly dependent on the surface molar ratio of Co2+/Co0 as revealed by XPS spectra, and the surface CoO layer played an important role in suppressing the loss of active Co species in hydroformylation of olefins. Moreover, the core–shell nano-catalysts are easily separated magnetically from the reaction mixture and showed good recyclability in nine consecutive catalytic runs. [ABSTRACT FROM AUTHOR]

Magnetic reduced graphene oxide supported CuO (rGO/Fe3O4–CuO) as a heterogeneous catalyst in cross dehydrogenative coupling (CDC) reactions has been demonstrated for the synthesis of esters using methyl aromatics and aldehydes/benzyl alcohols as coupling partners. Various benzylic esters were prepared efficiently from cheap raw chemicals by employing tert-butyl hydroperoxide (TBHP) as a "green" oxidant and tetra-n-butylammonium bromide (TBAB)/tetra-n-butylammonium iodide (TBAI) as additives. Because of the heterogeneous nature of this catalytic system, simple filtration was used to separate the catalyst. [ABSTRACT FROM AUTHOR]

In the present paper, we have reported the synthesis of an imine-based silica-functionalized copper(ii) catalyst using salicyldehyde as a ligand. Furthermore, the catalyst is characterized through various spectroscopic techniques, namely FTIR, XRD, TGA, EDX, XPS, SEM, TEM and AAS. Herein, we have studied its applications in the synthesis of the oxygen-containing heterocyclic 2-amino-4H-chromenes and the nitrogen-containing heterocyclic acridinones. A single crystal X-ray analysis of 2-amino-4-(4-chlorophenyl)-6,6,8,8-tetrahydro-7,7-dimethyl-5-oxo-4H-chromene-3-carbonitrile has revealed that the compound crystallizes in a monoclinic crystal system with space group P21/n. [ABSTRACT FROM AUTHOR]

This paper reports on the synthesis and use of palladium nanoparticles as heterogeneous catalysts for the reductive amination of aldehydes and hydrogenation of unsaturated ketones. This method has the advantages of high yields, simple methodology and easy work up. The catalyst can be recovered and reused several times without significant loss of catalytic activity. [ABSTRACT FROM AUTHOR]

The reaction of dithiooxamide with aromatic aldehydes is a well-known method for the preparation of thiazolo[5,4-d]thiazoles (TzTz). However, we report here that, using adequately substituted 2-halobenzaldehydes, this reaction may afford selectively thiazolo[5,4-c]isoquinolines (TzIQ) or mixtures of TzTz and TzIQ. The use of lanthanum(III) triflate as the catalyst favors the formation of TzIQ. The results obtained using a large number of substituted benzaldehydes showed that the nature, number and position of halogen atoms and other substituents on the aldehyde have a great impact on the reaction outcome. The structures of six TzTz and six TzIQ were unveiled by single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

1,3-Dipolar cycloaddition of nonstabilized azomethine ylides derived from α-C–H functionalization of tetrahydroisoquinoline for regio- and diastereoselective synthesis of spirooxindole-pyrrolidines is developed. A three-component reaction of readily available cyclic amines, aryl aldehydes, and olefinic oxindoles provides a pot, atom and step economy (PASE) approach for preparing spiro-heterocyclic compounds with biological interest. [ABSTRACT FROM AUTHOR]

With aldehydes as the radical precursors under visible-light irradiation, a simple and mild C–H acylation reaction of quinoxalin-2(1H)-ones has been achieved. A wide variety of functional groups could be incorporated into the products by employing diverse aldehydes and quinoxalin-2(1H)-one derivatives. Also, this method was applied to the modification of natural molecules and pharmaceutically relevant compounds. A mechanistic study revealed that an HAT process occurred in the acylation reaction for the generation of acyl radicals, and that PIFA ([bis(trifluoroacetoxy)iodo]benzene) acted both as the photosensitizer and oxidant in this reaction. [ABSTRACT FROM AUTHOR]

Furan-2-one derivatives are of great importance in chemistry for both synthetic and biological purposes. Herein, we report a new approach towards their synthesis via a mild, inexpensive, and green photochemical protocol, where dual analyte thioureas, 1 (1H-benzo[d]imidazol-2-yl)-3-(4-nitrophenyl)thiourea (BINPT) and 1-(4-methylbenzo[d]thiazol-2-yl)-3-(4-nitrophenyl)thiourea (MBNPT), are utilized as the catalyst and white LEDs as the light source via electron donor–acceptor (EDA) complexes. A variety of diethyl 2-(phenylamino)fumarates and aldehydes were converted into 3,4,5-trisubstituted furan-2-ones in good to high yields. Selected compounds were further studied using DFT calculations in order to establish a clear picture about the geometric parameters of the compounds. [ABSTRACT FROM AUTHOR]

Palladium(II) oxide (PdO) nanoparticles (Nps) were prepared by an environmentally benign hydrothermal method with a new capping agent quercetin. The nanoparticles were characterized using FT-IR, powder XRD, TG-DTA, SEM, EDS, HR-TEM, SAED and surface area analysis (BET) to reveal the formation, crystalline structure, thermal stability, morphology, elemental composition, size, crystalline nature and surface nature, respectively. Quercetin acted well as a capping agent and could yield PdO nanoparticles with a 10–15 nm size. For the first time nanosize PdO was employed as a heterogeneous catalyst for the preparation of therapeutically important propargylamines through A3 coupling reactions. A very small amount of catalyst (10 mg) was enough to complete the reaction. The isolated yields of the products were satisfying and the proposed catalyst could catalyze the reaction in the presence of a wide range of reactants. The turn over number (TON) was calculated to be high with a value of 10 625 h−1 and the turn over frequency (TOF) was also found to be excellent. The formation of propargylamines was confirmed by GC-MS analysis. The PdO catalyst was recyclable and reusable for 7 successive catalytic cycles without a significant loss in yield. [ABSTRACT FROM AUTHOR]

DFT calculations have been performed to study the relative preference of different unsaturated organic molecules (CO2, PhCHO and styrene) for insertion into different Cu--X (X = B, C, O) bonds, which are competing processes in copper-catalyzed three-component boracarboxylation reactions involving CO2 and B2pin2. In this work, the variations in the insertion barriers and in the relative stability of the insertion products have been systematically analyzed and discussed in-depth. Our DFT calculations also allow us to make a prediction that when both aldehyde and styrene are present with CO2 and B2pin2, styrene will undergo the three-component boracarboxylation reaction rather than the aldehyde. [ABSTRACT FROM AUTHOR]

A library of N-alkylated lipopeptide organocatalysts were synthesized through an isocyanide-based multicomponent reaction. Various structural motifs were tunably introduced on the catalyst backbone with the aim of incorporating amphiphilic features. Consequently, they have further been evaluated in the 1,4-addition of aldehydes to trans-β-nitrostyrene having water as the sole solvent. Under sustainable reaction conditions, Michael adducts were obtained in excellent yields, diastereoselectivities, and enantioselectivities using low catalyst loadings and without additives. [ABSTRACT FROM AUTHOR]

Herein we report an interesting multicomponent reaction of α,β-unsaturated aldehydes, 2-hydroxy-1,4-naphthoquinone and 5-aminopyrazoles by liquid assisted grinding. This three-component reaction provides styryl linked benzo[h]pyrazolo[3,4-b]quinoline-5,6(10H)-diones by grinding for 20–30 min in the presence of water (η = 0.25 μL mg−1). The resultant three-component product has four bioactive moieties such as 1,2-naphthoquinone, pyridine, pyrazole and styryl. One-pot green reaction conditions, short reaction time, easier purification process, and good yields are the other notable features of this methodology. All the products were characterized by IR, NMR and HRMS. Furthermore, the structure was unambiguously confirmed by recording single crystal XRD of two compounds. [ABSTRACT FROM AUTHOR]

We investigated the photocatalytic performance of a magnetic nanohybrid of CoFe2O4 and TiO2 hetero-nanostructures (TiO2/CoFe2O4) conjugated with zinc tetrakis carboxyphenyl porphyrin (ZnTCPP) for controlled oxidation of alcohols to aldehydes under visible light. The photocatalyst was prepared by nucleating titania on pre-formed CoFe2O4 nanoparticles, generating anatase TiO2/CoFe2O4 hetero-nanostructures upon annealing at 450 °C. Then, they were conjugated with ZnTCPP resulting in ZnTCPP-TiO2/CoFe2O4 nanohybrid materials, which were characterized in detail by different structural and spectroscopic methods. The ZnTCPP-TiO2/CoFe2O4 nanostructures have an average size of 21 nm and show ferromagnetic behavior with a magnetization saturation of 47 emu g−1, a remanence of 22 emu g−1, and a coercivity of ca. 1000 Oe. The photocatalytic conversion of alcohols up to 87% under visible light was achieved by using this hybrid nanomaterial. Such a high catalytic performance can be related to the low charge recombination rate of the ZnTCPP-TiO2/CoFe2O4 nanostructures. The magnetic hybrid nanostructures reported in this work have excellent potential as visible light photocatalysts with advantages of high efficiency, selectivity, stability, and easy separation. [ABSTRACT FROM AUTHOR]

Meerwein–Ponndorf–Verley reduction (MPVr) is a sustainable route for the chemoselective transformation of α,β-unsaturated aldehydes. However, tailoring ZrO2 catalysts for improved surface-active sites and maximum performance in the MPV reaction is still a challenge. Here, we synthesized mesoporous zirconia (ZrO2) and metal-doped zirconia (M_ZrO2, M = Cr, Mn, Fe, and Ni). The incorporation of metal dopants into zirconia's crystal framework alters its physico-chemical properties such as surface area and total acidity-basicity. The prepared catalysts were evaluated in the MPVr using 2-propanol as a hydrogen donor under mild reaction conditions. The catalysts' remarkable reactivity depends mainly on their surface mesostructure's intrinsic properties rather than the specific surface area. Cr_ZrO2, which is stable and sustainable, presented superior activity and 100% selectivity to unsaturated alcohols. The synergistic effect between Cr and Zr species in the binary oxide facilitated the Lewis acidity-induced performance of the Cr_ZrO2 catalyst. Our work presents the first innovative application of a well-designed mesoporous Cr_ZrO2 in the green synthesis of unsaturated alcohols with exceptional reactivity. [ABSTRACT FROM AUTHOR]

A simple one pot allylation and propargylation of aldehydes mediated by zinc(0), which is in situ generated from the redox couple of Al and ZnCl2 in 2N HCl, is demonstrated to afford the corresponding homoallyl and homopropargyl alcohols with excellent yields. [ABSTRACT FROM AUTHOR]

An expeditious microwave assisted one-pot sequential route to synthesize pyrido fused imidazo[4,5-c]quinolines via the Pictet–Spengler cyclization strategy has been developed. In this study, substituted 2-amino pyridines are condensed with 2-bromo-2′-nitroacetophenone to generate imidazo[1,2-a]pyridines with nitro group functionality at C-2 position. Reduction of nitro group to its amine congener in green media followed by the Pictet–Spengler cyclization strategy with substituted aldehydes led to the formation of new C–C and C–N bonds in a one-pot sequential manner. The cyclization proceeds through the CO(carbonyl)–C(H) cleavage of the aldehyde group via oxidative cross-coupling, transamination, cyclization and aromatization steps. Low cost reagents and a green solvent were used to facilitate the architecturally beautiful pyrido fused imidazo[4,5-c]quinoline scaffolds in high yields. The key features of this synthetic protocol are the use of microwave-assisted mild reaction conditions, one-pot sequential pathway, broad substrate scope and green media, which make it feasible for the synthesis of fused polyheterocycles. Moreover, the synthetic manipulation proceeded well with heteroaromatic and aliphatic aldehydes also in good yields. [ABSTRACT FROM AUTHOR]

Utilization of abundantly available biomass to develop advanced materials and products has become an utmost priority these days. Herein, we developed a sustainable route for the synthesis of Ni nanoparticles loaded on N-doped carbon nanosheets using underutilized sugarcane bagasse, urea and NiCl2·6H2O as the carbon, nitrogen and Ni source. The synthesized catalyst was characterized using different analytical techniques; FESEM, elemental mapping and HRTEM analysis revealed the formation of flower-like carbon nanosheets containing uniformly distributed nickel nanoparticles with average particle size of 2.4–10 nm. The synthesized nanocatalyst was used for the one-pot reductive amination of different bio-derived aldehydes with the nitroarenes at 100 °C for 4 h. The complete conversion of the variety of nitroarenes with the formation of imines and benzimidazole products was obtained under optimized reaction conditions. The catalyst was recyclable up to five times with negligible loss in selectivity towards imines. [ABSTRACT FROM AUTHOR]

A MOF-5-catalyzed three-component coupling reaction was developed as an efficient approach for the synthesis of 2,4-disubstituted quinoline derivatives via a one pot three-component reaction of aromatic amines, aldehydes and alkynes with excellent yields. The easy recovery and reusability of the catalyst, broad substrate scope, short reaction time, high yields of products and solvent-free conditions make this protocol practical, environmentally friendly and economically attractive. [ABSTRACT FROM AUTHOR]

In this study, a series of Pickering emulsions for catalysis of Knoevenagel condensations of malononitrile with aldehydes were prepared by surface modification of amine-functionalized graphene oxide (GO-NH2) with trimethoxymethylsilane (MTMS). The catalytic activity of the prepared Pickering emulsion system in a Knoevenagel condensation was mainly determined by the active sites and properties (namely droplet size, density, and distribution) of the emulsion. The results show that the mass ratio of 3-aminopropyltrimethoxysilane to MTMS affects the active catalytic sites and properties of the Pickering emulsion. Under conditions that provided a large number of active catalytic sites in the Pickering emulsion, modification of the surface of amine-functionalized GO with an organosilane enhanced substrate adsorption on the catalyst and improved the properties of water-in-oil Pickering emulsions. This increased the Picking emulsion catalytic activity. The Pickering emulsion prepared with GO-NH2 : Si = 1.8 : 0.2 gave the highest catalytic activity in a Knoevenagel condensation at 40 °C, and its activity was much higher than that of GO-NH2. The Pickering emulsion with GO-NH2(1.8)–Si(0.2) still showed high catalytic activity after six cycles and therefore has good reusability. [ABSTRACT FROM AUTHOR]

DBU-functionalized MCM-41-coated nanosized hematite (DBU-F-MCM-41-CNSH) was prepared as a new magnetically separable mesoporous nanomaterial and was characterized by various techniques such as FT-IR, XRD, HR-TEM, FESEM, BET, VSM and elemental analyses (CHN and ICP). The synthesized magnetic mesoporous nanomaterial was applied successfully as a basic nanocatalyst for the diastereoselective synthesis of 2-(N-carbamoylacetamide)-substituted 2,3-dihydrothiophenes through a one-pot four-component reaction of aryl aldehydes, primary and secondary amines, 1,3-thiazolidinedione and malononiterile in a 1 : 2 v/v mixture of EtOH/H2O at 60 °C. Using this method, all desired products were obtained in good to excellent yields (83–94%) after short times (25–45 min). The chemical and physical stability of the catalyst was proved by studying its chemical structure using the same analyses after the 8th reuse. [ABSTRACT FROM AUTHOR]

A bench-stable combination of NaBH4-acetylacetone was developed for the efficient chemoselective reduction of aldehydes in the presence of ketones. This method offers a useful synthetic protocol for distinguishing carbonyl reaction sites, and its synthetic utility is reflected by its moisture tolerance and high efficiency in a variety of complex settings. [ABSTRACT FROM AUTHOR]

A transition metal- and organophotocatalyst free synthesis of esters, carboxylic anhydrides and amides from aldehydes induced by visible-light has been reported. The proposed methodology can be carried out by the use of sunlight or artificial visible light as a blue LED source. The methodology has a very broad applicability and the desired products are obtained in very satisfactory yields. [ABSTRACT FROM AUTHOR]

Hydrogenation of alkenes, alkynes and aldehydes was investigated under biphasic conditions using Au nanoparticles (AuNP) embedded into combinations of α-cyclodextrin (α-CD) and a poloxamine (Tetronic®90R4). Thermo-responsive AuNP-containing α-CD/Tetronic®90R4 hydrogels are formed under well-defined conditions of concentration. The AuNP displayed an average size of ca. 7 nm and a narrow distribution, as determined by TEM. The AuNP/α-CD/Tetronic®90R4 system proved to be stable over time. Upon heating above the gel-to-sol transition temperature, the studied catalytic system allowed hydrogenation of a wide range of substrates such as alkenes, alkynes and aldehydes under biphasic conditions. Upon repeated heating/cooling cycles, the Au NP/α-CD/Tetronic®90R4 catalytic system could be recycled several times without a significant decline in catalytic activity. [ABSTRACT FROM AUTHOR]

Acetic acid mediated regioselective synthesis of novel 2,4,5-trisubstituted thiazole derivatives has been reported by a domino reaction of thiosemicarbazide and aldehydes/ketones/isatin, to generate thiosemicarbazones (in situ) followed by addition of arylglyoxal and active methylene/activated C–H acids/pyrazole/indole in ethanol at 80 °C. The products are obtained in high yields by a simple work up. Metal free, short reaction time and high yields are some merits of this methodology. [ABSTRACT FROM AUTHOR]

The present work describes an expedient approach for the direct conversion of indole-3-carboxaldehyde to 3-chlorooxindoles using a simple sustainable synthetic method. From an environmental perspective, a combination of NaCl/oxone in a CH3CN : H2O (1 : 1) system was developed for direct oxidative chlorination of a wide array of indole derivatives. This chlorination strategy is more viable, remarkably cheaper and provides easy access to potential 3-chlorooxindoles. In addition, this environmentally benign method can also be applicable for constructing isatin derivatives in good yields. [ABSTRACT FROM AUTHOR]

Reactions of 3-amino-2-pyrazinecarboxylic acid (HL) with SnCl2 under different hydrothermal conditions and crystallization processes produced two new mononuclear Sn(ii) compounds (1 and 2) of general formula [Sn(κN,O-L)2] (L = 3-amino-2-pyrazinecarboxylate), and single crystal X-ray diffraction analysis indicated that they are packing polymorphs, complex 1 crystallizing in the monoclinic C2/c space group whereas 2 in the monoclinic P21/c. The Hirshfeld surface analysis shows that the supramolecular features of both forms are guided by Sn…O and Sn…N contacts, as well as by strong N–H…O and N–H…N hydrogen bonds that differentiate the packing in the two forms. Complex 1 shows a one dimensional hydrogen bonded network whereas 2 shows a 2D hydrogen bonded network. To the best of our knowledge no examples of packing polymorphs based on tin(ii) complexes have been reported so far. These polymorphs are interconvertible when immersed in a suitable solvent or mixture of solvents. They also act as heterogeneous catalysts for the cyanosilylation reaction of aldehydes with trimethylsilyl cyanide (TMSCN) and can be recycled several times without losing activity. [ABSTRACT FROM AUTHOR]

A new metal–organic aerogel (MOA-Rh-2) containing dirhodium paddle-wheels has been prepared from the reaction of dirhodium(ii) tetracarboxylate (Rh2(OAc)4) and tetrakis(4-carboxyphenyl)porphyrin (TCPP) in a mixed solvent of DMF and water, followed by supercritical CO2 extraction. MOA-Rh-2 has been fully characterized by ICP-OES, EDS, XPS, PXRD, SEM, TEM and TGA. Its porosity has been confirmed by N2 adsorption isotherms at 77 K, and the Barrett–Joyner–Halenda pore size is centered at 3.5 nm. The existence of mesopores has been further verified by dye adsorption tests using methylene blue (14.4 × 6.1 Å2) and rhodamine B (15.8 × 11.8 × 6.8 Å3). MOA-Rh-2 is air and moisture-stable. The catalytic results show that, under an air atmosphere and at ambient temperature, a low loading (0.1–0.4 mol%) of MOA-Rh-2 can efficiently promote the hydrosilylation of aldehydes and ketones with the commercially available silane of PhSiH3. After catalytic reactions, MOA-Rh-2 can be recycled and reused for 5 runs without significant loss of the activity, and the reaction conversions are in the range of 89–99%. [ABSTRACT FROM AUTHOR]

In the present study, a novel propylamine-containing magnetic organosilica (Fe3O4@OS-NH2) material with a core–shell structure is prepared and characterized, and its catalytic performance is investigated in the one-pot condensation of aldehydes with ethyl cyanoacetate. The Fe3O4@OS-NH2 catalyst was prepared through simultaneous hydrolysis and condensation of bis(triethoxysilyl)ethane and (3-aminopropyl)trimethoxysilane around magnetic iron oxide nanoparticles. Several techniques such as energy-dispersive X-ray spectroscopy (EDX), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD) and vibrating sample magnetometry (VSM) were applied to characterize the Fe3O4@OS-NH2 catalyst. This nanomaterial showed an excellent efficiency in the Knovenagel condensation of aldehydes with ethyl cyanoacetate and gave the corresponding coupling products in high yields. This catalyst was also recovered and reused several times while retaining its performance and stability. [ABSTRACT FROM AUTHOR]

Transition metal (Cu, Mn, Ni, Zr) substituted metal organic frameworks (MOFs) are prepared for the reduction of carbon–carbon multiple bonds with hydrazine hydrate in ethanol under mild reaction conditions. Among the MOFs investigated in this study, the Cu framework substituted MOF exhibited the best activity in this study. Further, Cu nanoparticles (CuNPs) are supported on the surface of a Cu framework substituted MOF to achieve excellent reduction activity. The catalyst exhibits efficient recyclability with no appreciable loss in the catalytic activity even after five recycles. In order to establish the reaction mechanism, reactions are performed under N2 and Ar atmospheres. A reaction is also performed under an Ar atmosphere but in the presence of H2O2 to elucidate the mechanism. The catalyst exhibits excellent activity in the reduction of alkynes. Under the optimum reaction conditions, the catalyst is also successful in reducing a wide range of aldehydes and ketones. The present catalytic process demonstrates several key advantages such as mild and convenient reaction conditions, a low substrate to hydrazine ratio, reusability, and cost-effectiveness of the catalyst (Pt or Pd free catalyst). [ABSTRACT FROM AUTHOR]

A mild and efficient one-pot visible light-induced method has been developed for the synthesis of amino alcohols. Amino alcohols are important structural elements that are frequently found in pharmaceutical agents and biologically active natural products. The routine procedure in the drug discovery and development process to prepare and fully characterize amino alcohols makes them a drug candidate for biological evaluation. This protocol utilizes visible light as the greenest reagent and eosin Y as an organophotoredox catalyst to synthesise bioactive amino alcohols. Gram scale reactions demonstrated the potential synthetic applications of this protocol. [ABSTRACT FROM AUTHOR]

A series of fluorescent aldehydes were synthesized and used in a conventional Biginelli multicomponent reaction under Lewis acid CeCl3·7H2O catalysis. The photoactive hybrid dihydropyrimidin-2-ones (Flu-DHPM) were isolated in reasonable to good yields. The compounds presented emission in the visible region with a large Stokes’ shift and low quantum yield of fluorescence as expected, ascribed to the phototautomerism in the excited state (ESIPT). Moreover, the ESIPT process allowed for Flu-DHPM with intense emission in the solid state compared to the dihydropyrimidin-2-ones (DHPMs) without the benzazolic core. The observed photophysical features were successfully used to explore these compounds as fluorescent probes in biological media. In addition, cell imaging experiments demonstrated that these photoactive hybrids have potential for use as cellular markers. [ABSTRACT FROM AUTHOR]

A novel electrode material was prepared by electrochemical oxidation of [4,4′-phenylazo-2,2′-(ethylenediimino-κ2N-methyl)diphenolate-κ2O]nickel, a [Ni(ii)(salen)]-type complex, in chlorinated solvent. The chemical structure of the material was explored by FTIR, NMR and XPS techniques to determine the main components of the material and the nature of the linkage between them. The morphology of the material films was explored by SEM analysis. The electrochemical properties of the new material were studied by a set of voltammetric methods and an unusual stability of the material in aqueous medium was observed. [ABSTRACT FROM AUTHOR]

C1-Alkynylation of tetrahydroisoquinoline (THIQ) was achieved via the A3 coupling strategy from the reaction of THIQ as a secondary amine, aldehydes and alkynes using the CuO@Fe2O3 nanocatalyst under green reaction conditions. The wide scope of the present method was studied using various aliphatic/aromatic aldehydes and alkynes to afford the corresponding C1-alkynylated products in quantitative yields. Moreover, the present catalytic system was found to be versatile for the decarboxylative A3 coupling strategy with improved progress of reactions by replacing the alkynes with phenylpropiolic acid under optimized conditions. The present catalytic system was found to be robust, magnetically recoverable and recyclable 5 times without significant loss in its activity, offering a low E-factor and high atom economy (AE). [ABSTRACT FROM AUTHOR]