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A series of hydrophilic N,N-dimethylpyrrolidinium- and N,N-dimethylpiperidinium-based ionic liquids (ILs) have been prepared and applied as reaction media in the Wacker oxidation of styrene by hydrogen peroxide using PdCl2as the catalyst. The efficiency of these ILs was compared with hydrophilic and hydrophobic imidazolium systems (including those with nitrile functionalities). The nature of the ionic liquid strongly influences the product distribution. In particular, in hydrophobic ILs, relevant amounts of 1,3-diphenyl-1-butene arising from styrene dimerization were detected, in addition to the expected phenylmethylketone. The formation of 1,3-diphenyl-1-butene may be attributed to the formation of Pd(0) species from “ClPdOH” (probably formed during the Wacker process) in a side-reaction. Consequently, the ability of the IL to favor or disfavor the reoxidation of “ClPdOH” to “ClPdOOH” by hydrogen peroxide, giving an homogeneous phase or a biphasic system, appears to be the main factor affecting selectivity. [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]

Covering: up to late 2009 [ABSTRACT FROM AUTHOR]

(S,R)-Indan–ambox ligand and its ruthenium(ii) complex have been prepared and successfully applied to asymmetric hydrogenation of prochiral simple ketones. A wide range of unfunctionalized ketones are reduced by Ru(ii)-indan–ambox catalyst with excellent enantioselectivities (up to 97% ee). [ABSTRACT FROM AUTHOR]

A stereoselective gold-catalyzed [2 + 2 + 2] cycloaddition of ketoenynes substituted at the propargylic position with OR groups has been applied for the synthesis of (+)-orientalol F and pubinernoid B. [ABSTRACT FROM AUTHOR]

Exposure of a series of ?-(o-haloaryl)-substituted ketones to palladium-catalyzed carbonylation conditions leads to the formation of the corresponding isocoumarins. Balloon pressure of CO is sufficient to achieve high yielding reactions, and both cyclic and acyclic ketones are efficient substrates. The utility of the method is illustrated by a short synthesis of the natural product thunberginol A. [ABSTRACT FROM AUTHOR]

The intramolecular carbocyclization of tethered alkynyl ketones to five-membered cyclic enones is shown to be catalyzed by trifluoromethanesulfonic acid in MeOH, proceeding in good to excellent yields and with high selectivities. [ABSTRACT FROM AUTHOR]

Polyetheretherketone (PEEK), as a high-performance polymer, is widely used for bone defect repair due to its homogeneous modulus of elasticity of human bone, good biocompatibility, excellent chemical stability and projectability. However, the highly hydrophobic surface of PEEK is biologically inert, which makes it difficult for cells and proteins to attach, and is accompanied by the development of infections that ultimately lead to failure of PEEK implants. In order to further enhance the potential of PEEK as an orthopedic implant, researchers have explored modification methods such as surface modification by physical and chemical means and the addition of bioactive substances to PEEK-based materials to enhance the mechanical properties, osteogenic activity and antimicrobial properties of PEEK. However, these current modification methods still have obvious shortcomings in terms of cost, maneuverability, stability and cytotoxicity, which still need to be explored by researchers. This paper reviews some of the modification methods that have been used to improve the performance of PEEK over the last three years in anticipation of the need for researchers to design PEEK orthopedic implants that better meet clinical needs.

Ketones, such as beta-hydroxybutyrate (BHB), are important metabolites that can be used to monitor for conditions such as diabetic ketoacidosis (DKA) and ketosis. Compared to conventional approaches that rely on samples of urine or blood evaluated using laboratory techniques, processes for monitoring of ketones in sweat using on-body sensors offer significant advantages. Here, we report a class of soft, skin-interfaced microfluidic devices that can quantify the concentrations of BHB in sweat based on simple and low-cost colorimetric schemes. These devices combine microfluidic structures and enzymatic colorimetric BHB assays for selective and accurate analysis. Human trials demonstrate the broad applicability of this technology in practical scenarios, and they also establish quantitative correlations between the concentration of BHB in sweat and in blood. The results represent a convenient means for managing DKA and aspects of personal nutrition/wellness. [ABSTRACT FROM AUTHOR]

This paper shows a novel oxidative functionalization of α-amino ketones to yield the corresponding α-ketoamides and α-acylimidates. The reaction proceeds via oxygen delivery from water/alcohols in conjunction with an electron acceptor and 4-dimethylaminopyridine (DMAP). Mechanistic study indicates that DMAP exhibits a dual function of nucleophilic catalysis and proton abstraction. [ABSTRACT FROM AUTHOR]

For the controllable transformation of C3–6 diols in ethylene glycol (EG), a H-Beta zeolite catalyst was modified with NH3via incomplete desorption. 60.8% of acid sites on the zeolite were deactivated, but the ratio of strong acid sites was obviously increased. With 1,2-pentanediol (PDO) as a representative large-carbon-number diol, the undesirable acetalization and oligomerization reactions of EG were suppressed in the EG-PDO reaction system over the modified catalyst due to their dependency on total acid sites. NH3-TPD and FTIR results proved that Lewis acid sites on the modified zeolite were eliminated after modification, resulting in the suppression of acetalization and oligomerization reactions. In contrast, a portion of strong Brønsted acid sites still remained, ensuring the catalytic transformation of PDO. Only 8.2% of EG was consumed after 8 h reaction, and the conversion of PDO could reach 84.3%. The loading of NH3 on the surface of zeolite pores led to diffusion resistance, slightly decreasing the reaction rate of PDO without affecting the reaction selectivity. The catalytic reactions of other C3–6 diols in EG followed similar principles, and the selectivity to aldehydes or ketone was improved over this modified catalyst. Non-diol biomass hydrogenation products such as glycerol had a negative influence on the selectivity, so these components should be isolated before the reactions. This catalyst could be reused at least 5 times, and the conversion of PDO slightly decreased. This work sheds light on the relationships between the acid properties of the catalyst and different reactions of diols. [ABSTRACT FROM AUTHOR]

Direct and selective installation of two different functional groups into the unsaturated bonds of alkenes constitutes a long-standing goal in organic synthesis. Herein, we first report a photoelectrochemical approach for the carboacylation/silanoylation of alkenes with unactivated alkanes/hydrosilanes via the LMCT process. A number of ketones with high complexity and diversity were rapidly obtained from commercially available materials in an economical and sustainable manner. Furthermore, this protocol can be scaled up to the gram-level. This paired electrocatalysis strategy features excellent regioselectivity, and ample substrate scope, is external-oxidant-free, and features a high resource economy. A series of mechanistic experiments were performed to determine the preferred pathway for the photoelectrochemical Ni(I)/Ni(II)/Ni(III) cycles in these transformations. [ABSTRACT FROM AUTHOR]

Owing to its associated advantages such as the generation of two stereocenters in 100% maximum theoretical yield, mild reaction conditions and environmentally friendliness, ketoreductase (KRED)-catalyzed dynamic reductive kinetic resolution (DYRKR) is a versatile and appealing synthetic approach to access valuable chiral alcohols containing two or more stereocenters. Despite the considerable progress that has been made in this research field, previous studies mostly focused on ketone substrates with relatively simple structures. In the present study, ketoreductases YDR368w and YGL039w were identified through enzyme screening and applied to the KRED-catalyzed DYRKR of sterically hindered 2-aryl-1,5-benzothiazepin-3,4(2H,5H)-diones (1). Eleven structurally diverse chiral cis-(2S,3S)-2,3-dihydro-3-hydroxy-2-aryl-1,5-benzothiazepin-4(5H)-ones (cis-(2S,3S)-2), including the critical synthetic intermediates to the calcium channel blockers diltiazem and clentiazem, were prepared in 50–90% isolated yields with excellent stereoselectivities (all >20 : 1 dr and ≥99% ee). Finally, the successful execution of a gram scale synthesis and the demonstrated excellent recyclability of the immobilized ketoreductase (up to 20 cycles) both underscored the good application potential of the currently established DYRKR method. [ABSTRACT FROM AUTHOR]

Selective oxidation of alcohols to aldehydes/ketones is an important reaction in the fine and bulk chemicals fields. However, the classical alcohol oxidation methods are often performed under unfriendly conditions or use stoichiometric oxidants. Herein, we report an ingenious system that enables high selectivity (up to 99%) and high conversion (up to 97%) with high reaction rates in the aerobic oxidation of alcohols to aldehydes/ketones for a broad range of alcohols, proceeding smoothly via mixing the solvent ethyl acetate and HBr under ambient conditions with visible light irradiation. Experimental characterization and theoretical calculations reveal that solvated dispersion intermediates are formed spontaneously in situ through noncovalent interactions among the molecules in the reaction system, which is proposed to be the origin of the high selectivity and high activity of this reaction. The dispersion system provides a feasible activation approach for aerobic oxidation of alcohols to aldehydes/ketones with high performance under visible light. [ABSTRACT FROM AUTHOR]

This work focuses on the development and investigation of a Rh/TPP catalytic system for the synthesis of saturated aliphatic carboxylic acids from readily available oxygenated substrates, H2 and non-toxic, renewable CO2. Optimization of the reaction conditions and reagents was carried out using 2-butanol and 1-butanol as typical secondary and primary alcohols. Afterwards, the reaction system was investigated in-depth with a separate investigation of the reverse water–gas-shift-reaction and the carbonylation reaction as key steps of the overall tandem transformation. Based on these results, a reaction network was established with two distinct main pathways. While the secondary alcohols are converted preferentially via acid catalysed dehydration to the corresponding olefins followed by hydroxycarbonylation, the primary alcohols react primarily via nucleophilic substitution to the iodide compound followed by a Monsanto-type carbonylation. Based on these results, a broad range of alcohols including bio-based substrates was converted to the corresponding C1 elongated carboxylic acids. Additionally, other oxygenated substrates such as aldehydes, ketones and industrially relevant substrate mixtures were applied successfully. [ABSTRACT FROM AUTHOR]

The production of jet-fuel precursors from furfural via aldol-condensation with methyl-isobutyl ketone (MIBK) over defect-engineered UiO-66(Zr) catalysts is presented. The catalysts are prepared using formic acid (FA), trifluoroacetic acid (TFA) and HCl as synthesis modulators, leading to the incorporation of defects on the microcrystalline structure of the metalorganic framework (MOF) material, which dramatically boosts the catalytic performance. An extensive characterization of the modified catalysts by means of X-ray diffraction (XRD), argon adsorption isotherm, thermogravimetry (TGA), transmission electron microscopy, and FTIR spectroscopy of adsorbed acetonitrile, confirmed the incorporation of missing-linker and missing-node defects within the MOF structure, enabling the explanation of the enhancement in the catalytic process. The analysis of the reaction kinetics evidences that, working under moderate temperature conditions, conversion of furfural and selectivity to the desired adduct (FuMe) close to 100% can be achieved, avoiding the formation of degradation and bulkier compounds. Finally, despite the generation of defects within the UiO-66(Zr) structure, the resultant catalyst displays good reusability in low furfural concentration mediums. [ABSTRACT FROM AUTHOR]

Heyns/Amadori rearrangement allows the synthesis of α-aminocarbonyl compounds from α-hydroxycarbonyls and amines via the generation of an aminoenol intermediate. In the present work, the in situ generated aminoenol intermediate has been efficiently trapped with ketones/aldehydes for the construction of N-heterocycles. This method offers access to various substituted indole derivatives with a high level of regioselectivity through the intramolecular trapping of the aminoenol intermediate derived from o-acyl/formylanilines and α-hydroxydimethylacetals/ketals followed by rearrangement/aromatization in the presence of acid. Important features include the use of α-hydroxydimethylacetal/ketal as an α-hydroxycarbonyl equivalent, excellent regiocontrol, good functional group tolerance, selective synthesis of acylindoles, gram-scale synthesis, and synthesis of higher analogues of indoles and anti-tumor agent. [ABSTRACT FROM AUTHOR]

Enzymatic synthesis of enantiopure chiral halogenated aryl alcohols by ketoreductases (KREDs) is emerging but still challenging, due to the low solubility and slow mass transfer in aqueous media. As an ecofriendly tool for this issue, amphiphilic micelles are attractive. Herein, KRED-catalyzed reduction of halogenated aryl ketones in a TPGS-750-M formed aqueous micellar solution was conducted, achieving the corresponding chiral alcohols with moderate to excellent yields of up to 99% and remarkable enantioselectivities of >99% ee under the optimal conditions. Notably, the performance strengthening mechanisms of micelles in this process are illustrated, in which the solubilization position of the substrate plays an essential role and the substrates solubilized in the palisade layer of the micelles exhibit the highest increases in conversion and enantioselectivity. These findings provide guidance for rational design of enzyme catalysis in aqueous micellar media. [ABSTRACT FROM AUTHOR]

Ruthenium(II) complexes [RuL(CO)Cl(PPh3)2], 1a–4a, have been synthesized using ligands PhN＝NC(Ar)NOH, HL 1–4, respectively, by varying the pendant aryl (Ar) groups. The single crystal X-ray diffraction studies of complexes reveal that there are certain changes in Ru–Nazo and Ru–Noxime bond lengths that may be explained primarily on the basis of electronic effects of pendant aryl groups. In 4a, all Ru–N bond lengths are longer and this is attributed to oximato–O⋯O (hydroxyphenyl) interactions. Furthermore, there are weak intramolecular F⋯π interactions in 3a. The complexes display multiple reductive responses ascribable to electron acceptance within the azo-oxime framework of the coordinated ligand and the corresponding one-electron reduced metastable anion radical complexes of type [Ru(L˙−)(CO)Cl(PPh3)2]−[1]˙− have been generated. This property of the complexes has been exploited in electron transfer catalysis via trapping of electrons in the azo-oxime skeleton in two types of reactions: (1) α-alkylation of ketones with primary alcohols and (ii) synthesis of 2-substituted quinoline derivatives from 2-aminobenzyl alcohols and substituted acetophenones/alkyl methyl ketones. The scope of catalysis has been studied and the probable catalytic pathway has been established from experimental results. The catalytic pathway is ligand-centric and redox-driven for the dehydrogenation process and the initial step involves formation of a coordinated anion radical. This leads to conversion of the starting 1° alcohol to the corresponding carbonyl via the HAT pathway, with the ruthenium(II) centre practically behaving as a template and remaining redox inactive. The catalytic reactions have been proven to be affected by the nature of pendant aryl (Ar) groups within the coordinated ligand. [ABSTRACT FROM AUTHOR]

The direct C(sp³)--H functionalization reactions enable the development of green and streamlined synthetic routes for structurally complex molecules by circumventing the pre-activation of the substrates. Herein, we disclose an atom- and step-economic synthetic approach for rapid access to both α-(2- indolyl) ketones and α-(3-indolyl) ketones, which are privileged structures in bioactive molecules and organic synthesis, though generally prepared by bespoke multi-step strategies. The reaction proceeded via direct acylation of indole benzylic C(sp³)--H bond under the NHC and photocatalyst catalysis. The mild conditions, broad substrate scope, and predictable regioselectivity among multiple potential reactive sites enable efficient access to α-indolyl ketones from readily available 2- or 3-alkyl-substituted indoles. Furthermore, the competitive reaction at the 2- or 3-benzylic position of the 2,3-dialkyl-substituted indoles was systematically studied. Further transformation and bioactivity studies of the obtained α-(2- or 3-indolyl) ketones highlight the potential utility of this method. [ABSTRACT FROM AUTHOR]

The synthesis of 2-acylindolizines, possessing a readily modifiable ketone group, is of significant importance as it provides versatile precursors for the preparation of various indolizines. However, due to the electronically less active and more sterically demanding nature of α,β-unsaturated ketones toward iminium formation with an aminocatalyst, the efficient one-pot transformation of α,β-unsaturated ketones for distinct 2-acylindolizines bearing sensitive groups represents a challenge for synthetic chemists. Herein, we report a weak-coordination-auxiliary amino-catalyzed approach that enables directed [3 + 2] cyclization of α,β-unsaturated ketones and N-heteroaryl ketones for the desired 2-acylindolizines via an iminium ion/enamine tandem sequence. A highly broad range of commercially available α,β-unsaturated ketones (internal, terminal, and cyclic enones) can act as coupling partners for readily accessible 2-acylindolizines relative to the existing state-of-the-art methods. Control experiments and in-depth DFT calculations highlight the importance of weakly coordinated glycine's carboxylic group in promoting the intramolecular cyclization and 1,5-proton transfer processes. [ABSTRACT FROM AUTHOR]

Silanones (O＝SiR2), a heavier congener of ketones (R2C＝O), are highly reactive species that are readily converted to oligomeric siloxane (O–SiR2)n. Coordination of silanones to the transition-metal fragments to afford silanone-coordinated complexes is a reliable silanone stabilization method. Recently, our group reported the synthesis, structures, and reactivity of dimesityl-substituted silanone complexes Cp*(OC)2M{O＝SiMes2(L)}(SiMe3) (M = W, Mo, L: Lewis base, Cp*: η5-C5Me5, Mes: 2,4,6-Me3C6H2). Herein, to investigate the effect of substituents on the silicon atom during the formation of a silanone complex, we demonstrated the use of Mes and smaller Me groups. As a result, the formation of Mes(Me)-substituted silanone molybdenum complex Cp*(OC)2Mo{O＝SiMes(Me)(py)}(SiMe3) (5b, py: pyridine) was suggested, the silanone tungsten complex Cp*(OC)2W{O＝SiMes(Me)(DMAP)}(SiMe3) (4a, DMAP: 4-(dimethylamino)pyridine) was obtained, and a dimethyl-substituted disiloxanyloxy(dioxo) complex Cp*(O)2W(OSiMe2OSiMe3) (9) was formed. The reaction of 4a with PMe3 proceeded via the elimination of DMAP and migration of the SiMe3 group to the oxygen atom of the silanone ligand to afford Cp*(OC)2W(SiMes(Me)OSiMe3)(PMe3) (11a). The Mo complex Cp*(OC)2Mo(SiMes(Me)OSiMe3)(PMe3) (11b) was produced by the reaction of Cp*(OC)2Mo{＝SiMes(Me)}(SiMe3) (7b) with pyridine-N-oxide in the presence of PMe3. [ABSTRACT FROM AUTHOR]

Here we report the short synthesis of "reversed" halogenated C-nucleoside (benzimidazole) analogs. Initially, 1,2; 3,4 vicinal diols of D -galactose were acetylated with two different ketones, acetone and cyclohexanone, to furnish acetylated galacto pyranose 1a and 1b, respectively. Subsequently, pyridinium chlorochromate (PCC) was used for the oxidation of C-6 hydroxy- of 1a and 1b to aldehyde 2a and 2b in good yields. Subsequently, the acetylated β- D -galactopyranosyl C-6 aldehydes were reacted with halogen-substituted O-phenylenediamine to furnish reverse C-galactopyranosyl nucleosides 3a to 7a; 3b to 7b. Hitherto, this is the first report on the synthesis of pyranose-based reverse-position C-nucleosides. These newly synthesized C-nucleosides were identified as an anti-leishmanial agent, in vitro, against Leishmania major and Leishmania tropica. The halogen substitution on the benzimidazole moiety and lipophilicity of the acetylated group of C-nucleosides were found to be the key factors for anti-leishmanial activity. For instance, compound 3a, a non-halogenated analogue, was inactive while its bromine-substituted analogue 6a was considerably active against L. major and L. tropica with IC50 = 8.60 ± 0.04 μM and 8.3 ± 0.4 μM, respectively. Moreover, fluorinated nucleoside 4a with low lipophilicity was inactive but its analogue 4b was active against both strains L. major and L. tropica with IC50 = 24.7 ± 0.3 μM and 20.9 ± 0.4 μM, respectively. [ABSTRACT FROM AUTHOR]

Triazine derivatives, a class of electron-deficient π-conjugated molecules with high photochemical activity and excellent luminescent characteristics, have been utilized as a kind of electron-acceptor for the construction of molecular cages, luminescent and photochromic materials. In this paper, a novel and highly stable MOF with cubane-like clusters, [Co4(SO4)3(F)3(tpt)2(tatb)] (1) (tpt = 2,4,6-tris-(4-pyridyl)-1,3,5-triazine, H3tatb = 4,4′,4′′-(1,3,5-triazine-2,4,6-triyl)tribenzoic acid), has been successfully synthesized based on a triazine derivative, and possesses unprecedented sulfate- and fluoride-bridged cubane-type tetranuclear cobalt clusters and a 3D + 3D → 3D open framework. Compound 1 shows a rather high BET surface area and exhibits excellent thermal stability and high chemical stability in common solvents and even in acidic or basic solutions (in a pH range from 4 to 12). Moreover, catalytic measurements show that compound 1 is an excellent heterogeneous catalyst for the selective oxidation of aryl alkenes to aldehydes or ketones with conversions of 97%. [ABSTRACT FROM AUTHOR]

Extending the catalytic valorization roadmap of platform molecules is one of the core tasks in the development of the biomass conversion field. Through ongoing research efforts, the transformation system of biomass-derived platform molecules has been well established and is gradually becoming relatively mature. In this context, it is of great practical interest to further explore next-generation platform molecules and their valorization pathways that have recently emerged. Linear diketones, usually derived from biomass and their C6 furan compounds, are one of the novel platform molecules that have been recently spotlighted for the synthesis of high-end chemicals due to their huge valorization potential. Herein, we intend to underline the crucial platform role that linear diketones, i.e., 2,5-hexanedione (HD) and 1-hydroxy-2,5-hexanedione (HHD), play in extending the biomass valorization roadmap to a broader one. Perspectives are concentrated on elucidating the heterogeneous tandem conversion system of biomass and its derived C6 furan compounds to HD and HHD. Also, we further demonstrate the diverse valorization routes of HD and HHD to high-end chemicals for various applications. The insights presented in this paper may contribute to highlighting the bright future of linear diketones in constructing a sustainable biomass valorization system. [ABSTRACT FROM AUTHOR]

This manuscript describes the synthesis of a triazolyl-pyridine-based phosphine, N-((diphenylphosphaneyl)methyl)-N-methyl-6-(1-phenyl-1H-1,2,3-triazol-4-yl)pyridin-2-amine, [2,6-{(PPh2)CH2N(Me)(C5H3N)(C2HN3C6H5)}] (1) (here onwards referred to as PNN) and its cationic and neutral MnI complexes and catalytic applications. The reaction of 1 with Mn(CO)5Br afforded a cationic complex [Mn(CO)3(PNN)]Br (2), which is highly stable in solid state, but in solution it gradually loses one of the CO groups to form a neutral complex [Mn(CO)2(PNN)Br] (3). Complex 2 on treatment with AgBF4 also yielded a cationic complex [Mn(CO)3(PNN)]BF4 (4). These complexes efficiently promoted the synthesis of quinoline derivatives via acceptor-less dehydrogenative coupling of 2-aminobenzyl alcohol and ketones, with complex 3 showing the highest activity with a very low catalyst loading (0.03 mol%) at 110 °C. Complex 3 (0.5 mol%) also showed excellent catalytic activity in the transfer hydrogenation of ketones and aldehydes to form respective secondary and primary alcohols. [ABSTRACT FROM AUTHOR]

We investigate Ti(NEt2)4 supported on silica dehydroxylated at 700 °C as an easily accessible pre-catalyst for oxo/imido heterometathesis reactions. Being activated with TolNH2, the supported Ti amide (≡SiO)Ti(NEt2)3 (1) demonstrates catalytic activity in the imidation of ketones with N-sulfinylamines comparable with the most active previously described well-defined imido catalyst (≡SiO)Ti(＝NtBu)(Me2Pyr)(py)2 (2) (Me2Pyr = 2,5-dimethylpyrrolyl), which implies the in situ formation of surface imido species in this system. The materials obtained via treatment of 1 with anilines (TolNH2 (1a) and p-MeOC6H415NH2 (1b)) were studied with IR, EA and 1H, 13C, 15N and 2D solid-state NMR, although the proposed imido intermediate has not been detected, pointing towards tris-amides (≡SiO)Ti(NHC6H4X)3 (X = Me, OMe) being the major surface species in the isolated materials 1a and 1b. The system 1/TolNH2 was tested in a range of imidation reactions and demonstrated excellent performance for express high-yielding preparation of ketimines, formamidines, lactone imidates and sulfurdiimines, making it a convenient alternative to the well-defined supported Ti imido catalysts. [ABSTRACT FROM AUTHOR]

A novel, simple, eco-friendly, non-toxic aluminium catalyst was synthesised for the chemoselective reduction of α,β-unsaturated ketones. A wide range of ketones were achieved with excellent yields, mild conditions, and low catalyst loading. Furthermore, this unprecedented method allowed for the stereoselective reduction of natural ketones. [ABSTRACT FROM AUTHOR]

A series of tridentate copper(II) N-heterocyclic carbene (NHC) complexes with imidazole, benzimidazole, and 5,6-dimethylbenzimidazole azole rings were synthesized and comprehensively characterized via X-ray crystallography, ESI-MS, cyclic voltammetry, and UV-Vis and EPR spectroscopic studies. These complexes were then utilized for the optimization of ketone reduction under sustainable conditions using 2-acetylpyridine and phenylsilane. The relationships between product formation, temperature, reaction time, and catalyst loading for the hydrogenation reactions are covered in detail. Reduction of eighteen different aliphatic, cyclic, and aromatic ketones were demonstrated, which were compatible to produce the corresponding products in moderate to good yields. These systems were used to develop related DNA-hybrid catalytic systems, but only supported weak enantioselectivity. Further thermodynamic experiments showed Cu-NHC complexes did not demonstrate specific binding to DNA, which is consistent with their limited selectivity. [ABSTRACT FROM AUTHOR]

Degradation of air quality in the atmosphere is mainly caused by air pollution and represents a major health risk. Limona ketone (LK) (C9H14O, 4-acetyl-1-methyl-1-cyclohexene) is emitted by α-pinene, which is massively present in the indoor environment and a major atmospheric source of secondary organic aerosols (SOAs), and has attracted attention in the field of atmospheric chemistry. The OH-addition and H-abstraction reactions of LK by OH radicals have been investigated using M06-2X, ωB97X-D, MP2 and CCSD(T) with the 6-311+G(d,p) basis set. Its degradation channels and reactions with O2, NO and HO2 radicals have been explored using quantum chemical methods. The reaction kinetics were studied theoretically over the temperature range of 278–350 K by employing canonical variational transition state theory with the small curvature tunnelling (CVT/SCT) method for both barrierless channels and channels with barriers. The addition of OH at the C1 position of LK at the endocyclic double bond was shown to be the most favourable, with a small relative energy barrier of −7.27 kcal mol−1, and H-abstraction at the C4 position exhibited a relative energy barrier of −1.65 kcal mol−1 at the M06-2X/6-311+G(d,p) level of theory. Our calculated energy results show that the OH addition reactions are more dominant than the H-abstraction channel through electronic rearrangement. The obtained overall rate coefficient at 298 K is 4.77 × 10−10 cm3 molecule−1 s−1, which is in good agreement with the experimental rate coefficient of kOH = (1.29 ± 0.33) × 10−10 at 296 ± 2 K and ∼735 Torr determined by Atkinson et al. Addition of the OH radical at the C1 position predominates over all the other reaction channels, with a branching ratio of 56.20% at 298 K. Our theoretical results suggest that the atmospheric lifetime is ∼0.58 hours and the formation of stable product 1-(hydroperoxy-4-methylcyclohex-3-en-1-yl) ethenone is thermodynamically exothermic in nature. This work provides valuable information regarding the degradation mechanism and atmospheric fate of LK in the reaction initiated by the OH radical. [ABSTRACT FROM AUTHOR]

A Cu-based catalyst was developed for one-step solvent-free synthesis of aviation biofuel from biomass-derived ketones, including acetone, cyclopentanone, cyclohexanone, and 2-pentanone. Under the optimal working conditions, the conversion rate of acetone, cyclopentanone, cyclohexanone and 2-pentanone of 100% can be achieved by using Cu/Al2O3. 79.7 c% maximum carbon yield of liquid hydrocarbons with 89.5% selectivity of aviation biofuel was obtained under the conditions of 1.0 MPa H2, 280 °C, and 2 h−1 WHSV. The effects of the calcination temperature on the acidity and basicity of the catalyst, as well as the valence and dispersion of Cu species, were investigated. Based on DFT calculations and in situ DRIFTS results, the preferred adsorption of carbonyl groups and efficient dissociation of hydrogen on Cu+ increased the local concentration of H and feedstock on the catalyst surface, accelerating the rate-determining step that predominated on Cu0. The synergistic effect of Cu0 and Cu+ enhanced the formation of aviation biofuel. [ABSTRACT FROM AUTHOR]

An efficient strategy to construct α-alkynyl ketones through electrochemical difunctionalization of alkenes was developed. This method is oxidant-free, metal-free, high-efficiency and eco-friendly, and offers rapid constructions of 1,2-alkynyl migration products through the radical process of 3-exo-dig cyclization. Moreover, the reaction could undergo a successful transformation under continuous-flow conditions. [ABSTRACT FROM AUTHOR]

One-pot three-component synthesis of α-methylated ketones from secondary and primary alcohols via a triple dehydrogenative method is presented here. This protocol uses a polystyrene-supported catalyst and the catalyst is reused for five runs without any drop in its activity. Detailed mechanistic investigation was carried out with control reactions and deuterium labelling experiments revealed that secondary and primary alcohols act as a hydrogen source in this one-pot synthesis of α-methylated substituted ketones. [ABSTRACT FROM AUTHOR]

Chiral β-amino alcohols are crucial building blocks in the synthesis of pharmaceutically active molecules and natural products. Developing green and sustainable methods for synthesizing chiral β-amino alcohols from renewable feedstocks continues to pose a significant challenge. Herein, we proposed a simple one-pot two-stage artificial cascade biocatalysis system for highly efficient conversion of renewable biomass-derived aldehydes into chiral β-amino alcohols with good yields and excellent enantioselectivity via sequential hydroxymethylation and asymmetric reduction amination. The initial stage involves converting aldehydes into α-hydroxy ketones by providing formaldehyde through benzaldehyde lyase-catalyzed hydroxymethylation. The subsequent stage is to convert α-hydroxy ketones into chiral β-amino alcohols through amine transaminase-catalyzed asymmetric reduction amination. Combining the two different types of reactions with two different enzymes, biomass-derived furfural 1a could be easily converted into (R)-2-amino-2-(furan-2-yl)ethanol ((R)-3a) and (S)-2-amino-2-(furan-2-yl)ethanol ((S)-3a) with up to 95% and 92% conversions and >99% ee, respectively. In addition, with this cascade biocatalysis, several enantiopure arylglycinols 3b–e were synthesized (39.4–99.0% conversions and >99% ee) from the biomass-derived benzaldehydes (1b–c) and benzaldehyde derivatives (1d–e). Furthermore, biotransformation on a preparative scale gave (S)-3a and (R)-3a in good yields (64.6% and 60.4%) and excellent ee (>99%). This study presents an eco-friendly and sustainable approach for synthesizing chiral β-amino alcohols using biomass-derived aldehydes. [ABSTRACT FROM AUTHOR]

Olefins are important feedstocks in the production of fuels and many useful chemicals. Herein, cobalt molybdate (CoMoO4) was first synthesized by an environmentally friendly evaporation method and it exhibited excellent catalytic performance for the production of olefins by the selective hydrodeoxygenation (HDO) of ketones that can be derived from lignocellulose. On the basis of the characterization results, the excellent catalytic performance of CoMoO4 was attributed to its larger specific surface area, better pore structure, higher oxygen vacancy (or Mo5+ species) concentration, higher acid strength and higher concentration of acid sites. Under the optimized reaction conditions, 4-heptanone was almost completely converted to heptene, and a high carbon yield of heptene (96%) was achieved over a CoMoO4 catalyst with a Co/Mo atomic ratio of 0.8 (denoted as CoMoO4-0.8). The CoMoO4 catalyst is also active for the selective HDO of other lignocellulosic ketones (such as acetone, butanone, 2-pentanone, 3-pentanone, cyclopentanone, cyclohexanone, 5-nonanone and acetophenone) to their corresponding olefins. [ABSTRACT FROM AUTHOR]

Besides numerous synthetic and biological applications, the catalytic construction of chiral Swaminathan ketones and their analogues possessing a bicyclo[5.4.0]undecane core structure has remained challenging for the scientific community for over four decades. Not more than five Swaminathan ketones (S. ketones) and their analogues are known in the literature to date. Herein, we report an unprecedented organocatalytic asymmetric desymmetrization strategy for the synthesis of chiral S. ketones and their analogues with excellent enantioselectivities from the corresponding 2-alkyl-2-(3-oxobutyl)-cycloheptane-1,3-diones via amine/acid-catalysed conformation-controlled intramolecular aldol condensation. We further reported a neat protocol for the high-yielding synthesis of functionally diverse synthons, 2-alkyl-2-(3-oxobutyl)-cycloheptane-1,3-diones from 2-alkylcycloheptane-1,3-diones via Michael addition. Finally, we also reported the powerful green organocatalytic reductive coupling protocol for generating a huge library of 2-alkylcycloheptane-1,3-diones from the conformationally flexible cycloheptane-1,3-dione and readily available aldehydes, which are potential synthons for the synthesis of bicyclo[5.4.0]undecane skeletons. Constructing a sustainable library of functionally rich chiral S. ketones with excellent enantioselectivities through conformation-controlled intramolecular aldol condensation via asymmetric desymmetrization and their interesting synthetic transformations with high selectivities are the key attractions of this study. [ABSTRACT FROM AUTHOR]

Iron-catalysed 1,2-acyl migration of tertiary α-azido ketones and 2-azido-1,3-dicarbonyl compounds provides a simple and atom-economical approach toward enamides and isoquinolones. This paper reports two catalyst systems for these transformations which employ iron(II) complexes [Fe(dpbz)]Br2 (dpbz = 1,2-bis(diphenylphosphino)benzene) and FeBr2/Et3N, respectively. [Fe(dpbz)]Br2 was found to be highly effective at converting 2-azido-2,3-dihydro-1H-inden-1-ones to isoquinolones. The reagent combination of FeBr2/Et3N, on the other hand, exhibited a broader catalytic scope, owing to the beneficial effect of Et3N. This latter catalyst system enables 2-azido-2-methyl-1,3-dicarbonyl compounds to be converted to the corresponding enamides under mild conditions in good yields. [ABSTRACT FROM AUTHOR]

Three dipyrromethane–diphosphine ligands containing phenyl (L1H2), ethyl (L2H2) and cyclohexyl (L3H2) groups at their meso positions and their nickel complexes were synthesized and structurally characterized. Treatment of Ph2C(C4H3N)2-1,9-(CH2PPh2)2 (L1H2) with [NiCl2(DME)] gave complex [NiCl2(κ2-P,P-L1H2)] 2a. Conversely, the analogous reactions of L2H2 and L3H2 with [NiCl2(DME)] showed a mixture of products containing both a pyrrolide nitrogen coordinated complex of type [Ni(κ4-P,N,N,P-L)] 3 without an exogenous base and a chelated complex of type 2a. In addition, all three ligands react with [NiCl2(DME)] in the presence of a strong base to give a complex of type 3. Furthermore, a novel binuclear Ni(0) complex bearing L1H2 was characterized by X-ray crystallography. Both complexes 2a and 3 (0.5 mol% of loading) catalyze the transfer hydrogenation of a series of aromatic and aliphatic ketones (20 substrates) to their corresponding secondary alcohols using iPrOH as a hydrogen source in the presence of KOH at 100 °C in 6 h. The kinetic trace of the catalytic reaction shows that the meso-phenyl substituted diphosphine coordinated nickel complexes perform better than the other two ligand coordinated nickel complexes. [ABSTRACT FROM AUTHOR]

Palladium-catalyzed cross-coupling chemistry and in particular ketone α-arylation has been relying on a rather narrow range of supporting ligands with almost no alternatives to phosphines and N-heterocyclic carbenes. Here we introduce a class of well-defined palladium(II) complexes supported by N,N′-chelating and electronically flexible pyridylidene amide (PYA)-pyridyl ligands as catalysts for efficient α-arylation of ketones. Steric and electronic variations of the N,N′-bidentate ligand indicate that the introduction of an ortho-methyl group on the pyridinum heterocycle of the PYA ligand enhances the arylation rate and prevents catalyst deactivation, reaching turnover numbers up to 7300 and turnover frequencies of almost 10 000 h−1, which is similar to that of the best phosphine complexes known to date. Introducing a shielding xylyl substituent accelerates catalysis further, however at the expense of lower selectivity towards arylated ketones. Substrate scope investigations revealed that both electron-rich and -poor aryl bromides as well as a broad range of electronically and sterically modified ketones are efficiently converted, including aliphatic ketones. Mechanistic investigations using Hammett and Eyring analyses indicated that both, oxidative addition and reductive elimination are relatively fast, presumably as a consequence of the electronic flexibility of the PYA ligand, while enolate coordination was identified as the turnover-limiting step. [ABSTRACT FROM AUTHOR]

An efficient, one-pot protocol for the synthesis of aminofurazans from readily available and inexpensive bromomethyl ketones has been developed. Alkyl, aryl and heteroaryl aminofurazans have been synthesized and characterized by multinuclear NMR and single crystal X-ray crystallography. [ABSTRACT FROM AUTHOR]

Disubstituted adamantanes having nitrophenol moieties were examined for their ability to recognize ketone and ester molecules through multiple intermolecular interactions, with the hydroxyl and nitro groups serving as hydrogen bond donors and acceptors. Crystallization of 1,3-bis(2-hydroxy-5-nitrophenyl)adamantane (1) in acetone, 2-butanone, and methyl acetate afforded three inclusion crystals with 1 : 1 stoichiometry. X-ray crystallographic analysis revealed that the hydroxyl groups of 1 engaged in OH⋯O interactions with the guest oxygen atoms in all crystals. Moreover, the guest hydrogen atoms participated in CH⋯O interactions with the host nitro and hydroxyl groups at three, four, or five points. These findings suggest that the guest molecules were captured through interactions with multiple functional groups in a manner resembling that of guest inclusion in enzyme pockets. Crystallization of 1,3-bis(4-hydroxy-3-nitrophenyl)adamantane (2) and 1,3-bis(2-ethoxy-5-nitrophenyl)adamantane (3) in acetone resulted in the formation of guest-free crystals, with NO2⋯NO2 interactions being prominent in the crystal of 3. [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]

Titanium(IV) enolates of cyclododecanone (CDD) were investigated as convenient CH-acidic units for stereoselective aldol additions to various benzaldehydes leading to β-hydroxy carbonyl compounds. Aldol reactions were carried out at low temperatures, below −40 °C, which allowed minimizing the processes of dehydration and formation of enones. In contrast to alkali metal enolates that produced mainly anti-aldols, titanium(IV) enolates of CDD tend to favor syn-stereoselectivity. Studies showed that the stereoselectivity of aldolization depended on the size and location of substituents in the aromatic ring of benzaldehydes used. The strongest effect was exerted by substituents in ortho and meta positions, while para-substituted benzaldehydes were characterized by stereoselectivity comparable to that of unsubstituted benzaldehydes. The presented work is so far the only method of synthesizing syn aldols from cyclododecanone in a one-step reaction. [ABSTRACT FROM AUTHOR]

Herein, we investigated the α-acetoxylation of ketones through various experiments. These include screening of reaction conditions, analysis of reactivity and selectivity over diverse ketones, kinetic study of the reaction of monoacetoxylation and diacetoxylation, density functional theory calculations for estimating the energy and structure, and analysis of natural bond orbitals. Based on the reaction products of the study, the pseudo first-order model is determined as the best model for the reaction, and the identification of the reaction intermediates indicates that iodonium is an essential intermediate in the reaction. Additionally, kinetic studies and theoretical calculations reveal that the reaction may utilize a different mechanism depending on the ketone structure; in this case, however, we focused on the α-acetoxylation of 4-tert-butylcyclohexanone. Based on these findings, we propose a reaction mechanism and the corresponding behavior description for iodine(III) in α-acetoxylation reactions. [ABSTRACT FROM AUTHOR]

Alternative solid polymer membrane electrolytes have garnered significant attention due to their extensive utilization in electrochemical power sources. Among these, sulfonated poly(ether ether ketone) (sPEEK) based membranes stand out as promising candidates due to their cost-effectiveness, robustness, and proton conducting properties, making them a potentially viable alternative to Nafion® in polymer electrolyte fuel cells (PEFCs). In this study, we have enhanced the proton conductivity of sPEEK through a novel approach of tailoring a hydrophilic Cu–pyromellitic acid complex (Cu–PMA) to form sPEEK/Cu–PMA composite membranes. In this study, various sPEEK/Cu–PMA composite membranes with different Cu–PMA wt% (0.25, 0.5, 0.75 and 1) were prepared. The structural morphologies along with the physicochemical and mechanical properties of sPEEK, and sPEEK/Cu–PMA composite membranes were analyzed by scanning electron microscopy, atomic force microscopy (AFM), X-ray diffraction (XRD), 1H-nuclear magnetic resonance (NMR), infra-red spectroscopy, universal testing machine (UTM), simultaneous thermal analysis (TG-DSC), dynamic mechanical analysis (DMA) etc. Moreover, the incorporation of Cu–PMA into the sPEEK matrix facilitated the formation of hydrophilic domains, leading to improved ionic conductivity. Notably, the sPEEK/Cu–PMA composite membrane with an optimal Cu–PMA loading of 0.5 wt% exhibited an impressive proton conductivity of 0.162 S cm−1, surpassing both the sPEEK membrane and other sPEEK/Cu–PMA composite membranes. This represents a remarkable >60% enhancement in proton conductivity for the sPEEK/Cu–PMA-0.5 wt% composite membrane in comparison with sPEEK (0.10 S cm−1) under high temperature and fully humid conditions. Furthermore, the sPEEK/Cu–PMA-0.5 wt% hybrid composite membrane demonstrated superior performance retention during cycling, as evidenced by heating–cooling–heating (HCH) measurements. Additionally, in a PEFC, the membrane electrode assembly (MEA) of the sPEEK/Cu–PMA-0.5 wt% composite membrane delivered an impressive current density of 960.14 mA cm−2 at an operating cell voltage of 0.6 V and a peak power density of 748 mW cm−2, which is ∼2 times higher than that of the MEA prepared with sPEEK (a current density of 488.5 mA cm−2 at a cell voltage of 0.6 V, and a peak power density of 404.11 mW cm−2). Notably, the sPEEK/Cu–PMA-0.5 wt% hybrid composite membrane exhibited 86% retention of open circuit voltage (OCV) even after a stability test of >100 h at 30% relative humidity and a cell temperature of 80 °C, confirming its viability for energy conversion and storage devices. [ABSTRACT FROM AUTHOR]

A series of manganese(I) carbonyl complexes bearing structurally related NN- and NNN-chelating ligands have been synthesized and assessed as catalysts for transfer hydrogenation (TH). Notably, the NN-systems based on N-R functionalized 5,6,7,8-tetrahydroquinoline-8-amines, proved the most effective in the manganese-promoted conversion of acetophenone to 1-phenylethanol. In particular, the N-isopropyl derivative, Mn1, when conducted in combination with t-BuONa, was the standout performer mediating not only the reduction of acetophenone but also a range of carbonyl substrates including (hetero)aromatic-, aliphatic- and cycloalkyl-containing ketones and aldehydes with especially high values of TON (up to 17 200; TOF of 3550 h−1). These findings, obtained through a systematic variation of the N-R group of the NN ligand, are consistent with an outer-sphere mechanism for the hydrogen transfer. As a more general point, this Mn-based catalytic TH protocol offers an attractive and sustainable alternative for producing alcoholic products from carbonyl substrates. [ABSTRACT FROM AUTHOR]

Herein, we report an efficient and sustainable approach for the selective synthesis of ketones by palladium pincer catalyzed β-alkylation of secondary alcohols with aromatic primary alcohols via the borrowing hydrogen (BH) approach for the first time. A set of new Pd(II) ONO pincer complexes was synthesized and characterised by elemental analysis and spectral techniques (FT-IR, NMR and HRMS). The solid-state molecular structure of one the complexes was corroborated by X-ray crystallography. A range of α-alkylated ketone derivatives (25 examples) was obtained in excellent yields up to 95% through sequential dehydrogenative coupling of secondary and primary alcohols with 0.5 mol% catalyst loading with a substoichiometric amount of the base. Control experiment studies were carried out for the coupling reactions which revealed that the reaction involves an aldehyde, a ketone and chalcone intermediates, and eventually established the borrowing hydrogen strategy. Gratifyingly, this protocol is simple and atom economical, with water/hydrogen as byproducts. In addition, large-scale synthesis also demonstrated the synthetic usefulness of the present protocol. [ABSTRACT FROM AUTHOR]

The photosynthetic tetrapyrroles and their catabolic products (phyllobilins) share similar structural features in the southern rim encompassing rings C–E with variation in the degree of saturation including a dihydrodipyrrin (chlorophyll a and bacteriochlorophyll a), a dipyrromethane (phylloleucobilin), and a dipyrrin (chlorophyll c). Here, a direct, two-step route to southern rim structures was examined. The Knoevenagel condensation of a pyrrole bearing a β-ketoester at the 3-position with a pyrrole-2-carboxaldehyde formed the dipyrrole-substituted propenone, which upon Nazarov cyclization gave the dipyrromethane-type southern rim containing the annulated, isocyclic ring. In this manner, three southern rim structures (51–80%) were obtained that vary in the nature of the pyrrole substituents (H, methyl, carbomethoxy). Characterization by 1H NMR spectroscopy in each case revealed an expected mixture of trans/cis isomers (∼9 : 1 ratio). Several derivatization processes (pyrrole acylation with trichloroacetic anhydride, ketone reduction with borohydrides) were examined. Analysis of one southern rim compound by single-crystal X-ray diffraction showed the trans configuration for the expected pair of enantiomers in the unit cell; a second compound gave the trans enantiomers as a conglomerate. The Knoevenagel–Nazarov route from relatively accessible pyrroles may provide new scaffolds for constructing tetrapyrrole architectures. [ABSTRACT FROM AUTHOR]

A group of three Ir-(III) complexes supported by a picolinamidato moiety was prepared. These complexes were shown to be efficient catalysts for α-alkylation of ketones and β-alkylation of secondary alcohols with primary alcohols in the presence of a catalytic amount of the Cp*Ir(III) catalyst and tBuOK in toluene at 110 °C via hydrogen-borrowing and produced substituted ketone products in good to excellent yields. This new C–C bond-forming reaction needs very small amounts of catalyst and base and produces only H2O as a by-product, making it an appealing and environmentally friendly protocol that allows for the "green" synthesis of ketone derivatives. [ABSTRACT FROM AUTHOR]

The use of multienzymatic systems has gained increasing attention as a method of choice for complex (asymmetric) syntheses. Incompatibilities between substrates, reagents and/or enzymes in one-pot batch conditions can hamper the applicability of a pursued cascade, so the use of flow systems provide useful synthetic solutions. The implementation of immobilised enzymes in continuous flow reactors allows the compartmentalisation and segregation of the enzymes in separate reactors, leading to otherwise disfavoured reaction cascades. Here, an amine transaminase and a lipase have been immobilised on polymer-coated controlled porosity glass carrier materials and studied for the first time together in the transamination of a prochiral ketone followed by acylation of the corresponding chiral amine in flow mode, two incompatible transformations under batch. Thus, the preparation of (R)-N-(1-phenoxypropan-2-yl)acetamide was accomplished after optimisation of the reaction conditions. [ABSTRACT FROM AUTHOR]