Aliphatic Aldehydes Research Articles

Hydrogenation of Aliphatic Aldehydes and Ketones on Stabilized PtRu or IrRu Bimetallic Nanoparticles

Key words iridium catalysis - platinum catalysis - ruthenium catalysis - bimetallic nanoparticles - hydrogenation - carbonyl compounds

Uranyl(VI) Triflate as Catalyst for the Meerwein-Ponndorf-Verley Reaction.

Catalytic transformation of oxygenated compounds is challenging in f-element chemistry due to the high oxophilicity of the f-block metals. We report here the first Meerwein-Ponndorf-Verley (MPV) reduction of carbonyl substrates with uranium-based catalysts, in particular from a series of uranyl(VI) compounds where [UO2(OTf)2] (1) displays the greatest efficiency (OTf = trifluoromethanesulfonate). [UO2(OTf)2] reduces a series of aromatic and aliphatic aldehydes and ketones into their corresponding alcohols with moderate to excellent yields, using iPrOH as a solvent and a reductant. The reaction proceeds under mild conditions (80 °C) with an optimized catalytic charge of 2.3 mol % and KOiPr as a cocatalyst. The reduction of aldehydes (1-10 h) is faster than that of ketones (>15 h). NMR investigations clearly evidence the formation of hemiacetal intermediates with aldehydes, while they are not formed with ketones.

A Cross‐Coupling Reaction Between Aliphatic Aldehydes And Sulfonium Salts

AbstractThe synthesis of multi‐substituted electron‐deficient alkenes is often accomplished via cross‐coupling of diazo compounds in the presence of a metal catalyst. Herein, we report an organocatalytic protocol that enables the direct coupling of aliphatic aldehydes with sulfonium ylides. A key carbene mimetic, α‐iodoenamine/enol, is believed to engage in direct cross‐coupling with a sulfonium ylide, delivering α,β‐unsaturated carbonyl compounds with a formyl substituent. The reaction demonstrated remarkably mild conditions, convergence, and control of olefin geometry.magnified image

Mechanistic Insights on the Anionic Polymerization of Aliphatic Aldehydes

Self-immolative polymers are a class of stimuli-responsive macromolecules that can unzip down to monomer level. Among those, aliphatic polyaldehydes are particularly attractive due to their ability to rapidly depolymerize at ambient temperatures. By virtue of their thermal fragility, their preparation is challenging, and no mechanistic details exist about their synthesis. This study aims at clarifying the mechanism of the anionic polymerization of aliphatic aldehydes. For this purpose, several aliphatic aldehydes were polymerized using a variety of initiators. It was found that irrespective of the nature of the initiating species, the enolate formed between the initiator and the monomer is actually triggering the polymerization. The formation of an enolate is also responsible for a chain-transfer reaction to monomer, which limits the molecular weight of the polymer (ktr/kp = 0.0036). The microstructure of the polymer was determined by solid-state 13C nuclear magnetic resonance spectroscopy. It was found that all anionic polymers are linear, mostly isotactic (mm > 60%), and crystalline. These polymers are prone to depolymerize at room temperature in solution, making them interesting candidates as self-immolative polymers.

Metabolomics profiling of human exhaled breath condensate by SPME/GC × GC-ToFMS: Exploratory study on the use of face masks at the level of lipid peroxidation volatile markers

Metabolomics encompasses the acquisition of large-scale datasets from a single sample to identify and/or elucidate physiological or pathological mechanisms, or even to assess environmental exposure, being sample preparation and instrumental analysis two fundamental steps in the construction of a metabolomics workflow. The study of the human exhaled breath condensate (EBC) has gained tremendous interest recently owing to the advances in analytical techniques. Thus, this study aims to develop a methodology for EBC metabolites profiling based on headspace solid phase microextraction (SPME) combined with comprehensive two-dimensional gas chromatography (GC × GC). Metabolite’s extraction efficiency was improved by the optimization of four SPME parameters using a real EBC matrix: fibre coating, sample pH and volume, and extraction temperature. EBC analysis was performed according to the optimized parameters, using aliquots of 500 μL of EBC, at its physiological pH, with the DVB/CAR/PDMS fibre coating, at 40.0 ± 0.1 °C, being able to detect analytes at pg/mL, with acceptable reproducibility. EBC volatile composition was provided, with around 400 chemical features detected, in which 130 were putatively identified as belonging to hydrocarbons, aldehydes, alcohols, ketones, esters, monoterpenic and sesquiterpenic compounds, ethers, norisoprenoids and furans, revealing therefore its high complexity. This research represents the most detailed study on the volatile composition of EBC and allows the assessment of a broad range of endogenous and exogenous metabolites, with further relevance on clinical or environmental exposure studies. To test the applicability of this methodology, an exploratory study was carried out to assess the impact of the use of surgical facemasks on young researcher’s lipid peroxidation volatile markers during a normal working day in a laboratory. In young healthy adults (age ≤ 32), the use of surgical facemasks seems not significantly affect the levels of the volatile markers of lipid peroxidation (aliphatic alkanes and aldehydes), neither the O2 saturation level - SpO2. This methodology shows promise as a convenient way to follow specific physiological or pathological conditions based on EBC metabolome and may be paired as part of an aggregate analytical structure.

A Highly EfficientN‐Mesityl Thiazolylidene for the Aliphatic Stetter Reaction: Stereoelectronic Quantification for Comparison of N‐Heterocyclic Carbene Organocatalysts

AbstractThe NHC‐catalysed intermolecular Stetter reaction provides direct access to 1,4‐diketones, however current NHC catalysts for this specific transformation remain underdeveloped, significantly limiting the use of this reaction in target‐oriented synthesis. Here we report a novelN‐mesityl thiazolium NHC as a high‐performing catalyst for this reaction, enabling high yields and short reaction times for a range of sterically non‐trivial aliphatic aldehydes reacting with enone substrates. Quantification of the properties of novel and known NHC organocatalysts revealed that both steric and electronic properties play an important role in the success of the newN‐mesityl thiazolium NHC for this reaction. These developments will facilitate wider application of the Stetter reaction as a key carbon‐carbon bond forming reaction for coupling of complex fragments under mild conditions.

Ambipolar Charge Transport Properties of Naphthophenanthridine Discotic Liquid Crystals.

A series of novel naphthophenanthridine derivatives are synthesized via N-annulation of hexabutoxytriphenylene-1-amine with various aliphatic aldehydes through the Pictet-Spengler reaction. The synthesized derivatives have been found to self-assemble into a columnar hexagonal mesophase over a wide temperature range, as validated through polarized optical microscopy, differential scanning calorimetry and X-ray diffraction experiments. The photophysical properties of these compounds were studied using UV-visible and emission spectroscopy. The synthesized compounds exhibit ambipolar charge transport, showing temperature-independent electron and hole mobility on the order of 3 × 10-4 cm2/V s, as evaluated by the time-of-flight technique. These novel N-annulated derivatives can be of immense potential toward semiconducting applications of self-assembling supramolecular systems.

Formaldehyde, aliphatic aldehydes (C2 -C11 ), furfural, and benzaldehyde in the residential indoor air of children and adolescents during the German Environmental Survey 2014-2017 (GerES V).

Indoor air concentrations of formaldehyde, furfural, benzaldehyde, and 11 aliphatic aldehydes (C2 -C11 ) were measured in residences of 639 participants in the German Environmental Survey for Children and Adolescents 2014-2017 (GerES V). Sampling was conducted using passive samplers over periods of approximately seven days for each participant. The most abundant compounds were formaldehyde and hexanal with median concentrations of 24.9µgm-3 and 10.9µgm-3 , respectively. Formaldehyde concentrations exceeded the Guide Value I recommended by the German Committee on Indoor Guide Values (Ausschuss für Innenraumrichtwerte - AIR) (0.10mg m-3 ) for 0.3% of the participating residences. The sum of aliphatic n-aldehydes between C4 (butanal) and C11 (undecanal) exceeded their Guide Value (0.10mgm-3 ) for 2.0% of the residences. The geometric mean concentrations of most aldehydes were lower than in the earlier GerES IV (2003-2006) study. Formaldehyde and hexanal concentrations, however, were comparable in both studies and showed no significant difference. Indoor aldehyde concentrations did not exhibit significant correlations with factors collected in questionnaires, such as the age of the participants, their socio-economic status, the location of the residence (former East/West Germany), migration background, tobacco exposure, and the type of furniture used. The validity of the passive sampler measurements was verified against active sampling techniques in a test chamber experiment.

Role of metal center and coordination environment in M-(Z)-N-((E)-pyridin-2-ylmethylene)isonicotinohydrazonate (M = LaIII, ZnII, CdII or HgII) catalyzed cyanosilylation of aldehydes

A series of known metal complexes, [LaL2(NO3)(H2O)2]·5H2O (1), [Zn(μ-L)(NO3)(H2O)]n (2), {[Cd2(μ-HL)(μ-L)(NO3)3(H2O)]·H2O}n (3) and [Hg(μ-L)(N3)]n·nH2O (4), were synthesized from the corresponding metal salts and 2-pyridinecarboxaldehyde isonicotinoylhydrazone (HL), and demonstrated high activity and selectivity in the cyanosilylation of aldehydes. Although all the complexes are derived from the same HL hydrazone ligand, the catalytic activity of 1–4 is different and relates to the metal center and coordination environment, whereas complex 1 being the most effective homogeneous Lewis acid-base catalyst towards the synthesis of cyanohydrin trimethylsilyl ethers from both aliphatic and aromatic aldehydes with yields up to 96.3 % in 6 h in methanol solution and at room temperature. According to the proposed mechanism, both coordination and noncovalent interactions (hydrogen and tetrel bonds) play a significant role and account for the higher catalytic activity of complex 1.

Optimizing the Iodide/Iodonium/O2 Oxidation Cycle Enhances the Scope, Selectivity, and Yields of Hydroiodic Acid‐Catalyzed Multicomponent Cyclocondensation Reactions

AbstractCatalytic iodine in the presence of water acts indirectly as a source of Brønsted acid and, concurrently, generates iodonium ion and hydrogen peroxide, which mediate the final oxidative aromatization step in the multicomponent cyclocondensation of an aromatic amine and two aliphatic aldehyde compounds. The oxidative cycle in this and related iodine‐catalyzed reactions is seldom discussed, generally unoptimized, and rarely investigated in detail. This work establishes that two independent catalytic cycles (H+ and I−/I+) drive such multicomponent cyclocondensation/ oxidation reactions, provided that the oxidant is generated in sufficient concentration to inhibit oxidation of the dihydroquinoline by the intermediate iminium cation. The complementary dual catalytic cycles, when optimized, act in concert to suppress side product formation, which simplifies isolation and purification of the self‐aggregating products, and increases the efficiency and scope of the Wang‐Kozlov multicomponent reaction.magnified image

Bioactivity of Cereal- and Legume-Based Macaroni Pasta Volatiles to Adult Sitophilus granarius (L.).

Simple SummaryPasta factories can be infested by insects. By following the odour of cereal-based pasta, insects can enter packages of commercial products. The aim of this work was to compare the bioactivity of volatiles produced by cereal- and legume-based macaroni pasta on adults of granary weevil, Sitophilus granarius, in multi-choice behavioural bioassays. Tests were performed with ten commercially available Italian macaroni pastas made from six different cereals or four different legumes. Granary weevil adults were more attracted to cereal-based pastas than legume-based pastas, but the differences in attractiveness were not always significant. Gas chromatography-mass spectrometry analysis of head-space solid-phase microextraction collections from the different pasta samples highlighted marked qualitative and quantitative differences, with aliphatic aldehydes and aliphatic alcohols being the most abundant volatile components of cereal- and legume-pastas, respectively. Moreover, the results of the two-choice behavioural bioassays suggested that the low level of attraction to legume pasta is mainly due to the lack of attractant stimuli other than emission of repellent compounds.The attractiveness of ten commercially available Italian macaroni pastas made from different cereals [Triticum durum; Triticum durum (whole wheat); Triticum dicoccum; mixture of five cereals; Triticum turgidum; Triticum turanicum] or legumes (Cicer arietinum; Lens culinaris; Pisum sativum; Vicia faba) to Sitophilus granarius, was compared. S. granarius adults were more attracted to cereal pastas than legume pastas, but the differences in attractiveness were not always significant. Consistent with the results of behavioural bioassays, the mortality of adults over 20 days exposed to pasta samples was 100% with the legume pasta samples and only 8% with the T. turanicum pasta. GC-MS analysis of HS-SPME extracts from the different pasta samples highlighted marked qualitative and quantitative differences, with aliphatic aldehydes and aliphatic alcohols being the most abundant volatile components of cereal- and legume-pastas, respectively. In two-choice behavioural bioassays, insect attraction to a 1:1 combination of T. turanicum and C. arietinum pastas (80%) was even higher than that observed in T. turanicum pasta alone (64%) and in C. arietinum pasta alone (20%). This strongly suggested that the low attractiveness of legume pasta is mainly due to the lack of attractant stimuli rather than emission of repellent compounds.

Variation of Yield and Chemical Composition of Essential Oil from Cupressus lusitanica Growing in Different Agro-ecological Zones of Rwanda

Chemical composition and essential oil contents among essential oil-bearing plants are mostly influenced by different factors including ecological features of habitat. In this study, variation in yield and chemical composition of essential oils (EOs) from the leaves of Cupressus lusitanica Mill. (Cupressaceae) in different regions of Rwanda was investigated. Extraction of essential oils from fresh leaves of C. lusitanica collected in March 2021 and April, 2021 from three different ecological zones of Rwanda, Buberuka highland zone (Burera), Central plateau zone (Huye) and Eastern savannah zone (Kayonza) was realized through steam distillation. The chemical compositions of distilled EOs were analyzed using both Fourier transform infrared (FT-IR) spectroscopy and gas chromatography-mass spectrometry (GC-MS), while their yields were determined by simple calculus. The average yields of the EOs were 0.27 ± 0.02, 0.34 ± 0.02 and 0.39 ± 0.01% (v/w) for Burera, Huye and Kayonza, respectively. Results of FT-IR analysis were confirmed by those of GC-MS analysis, and indicated the presence of different groups of compounds including aliphatic alkanes, carboxylic acids, alkenes, aldehydes, aromatics and ketones in the EOs. GC-MS results revealed that sabinene (20.84%), myrcene (19.63%), α-pinene (10.23%) and δ-3-carene (10.13%) were the dominant chemical constituents for EOs of C. lusitanica from Burera. Umbellulone (24.21%), δ-3-carene (16.76%), sabinene (10.54%) and α-pinene (8.21%) were the main constituents for EOs of C. lusitanica from Huye, while γ-terpinene (18.77%), umbellulone (18.16%), isobornyl acetate (9.972%), and myrcene (7.20%) were the major components of EOs of C. lusitanica from Kayonza. The current results demonstrated an intraspecific variation in content and chemical profile of C. lusitanica EOs from one geographical region to another. The observed variations are mostly due to the interactions of C. lusitanica species with climatic and environmental conditions of ecological habitat. However, it could also be the effects of various biotic factors, as well as maturity of plant and stage of plant growth. Further studies are needed to establish the influence of different geo-climatic and environmental factors on each single major component of C. lusitanica EOs.

Amide Bond Formation via Aerobic Photooxidative Coupling of Aldehydes with Amines Catalyzed by a Riboflavin Derivative.

We report an effective, operationally simple, and environmentally friendly system for the synthesis of tertiary amides by the oxidative coupling of aromatic or aliphatic aldehydes with amines mediated by riboflavin tetraacetate (RFTA), an inexpensive organic photocatalyst, and visible light using oxygen as the sole oxidant. The method is based on the oxidative power of an excited flavin catalyst and the relatively low oxidation potential of the hemiaminal formed by amine to aldehyde addition.

LuxAB-Based Microbial Cell Factories for the Sensing, Manufacturing and Transformation of Industrial Aldehydes

The application of genetically encoded biosensors enables the detection of small molecules in living cells and has facilitated the characterization of enzymes, their directed evolution and the engineering of (natural) metabolic pathways. In this work, the LuxAB biosensor system from Photorhabdus luminescens was implemented in Escherichia coli to monitor the enzymatic production of aldehydes from primary alcohols and carboxylic acid substrates. A simple high-throughput assay utilized the bacterial luciferase—previously reported to only accept aliphatic long-chain aldehydes—to detect structurally diverse aldehydes, including aromatic and monoterpene aldehydes. LuxAB was used to screen the substrate scopes of three prokaryotic oxidoreductases: an alcohol dehydrogenase (Pseudomonas putida), a choline oxidase variant (Arthrobacter chlorophenolicus) and a carboxylic acid reductase (Mycobacterium marinum). Consequently, high-value aldehydes such as cinnamaldehyde, citral and citronellal could be produced in vivo in up to 80% yield. Furthermore, the dual role of LuxAB as sensor and monooxygenase, emitting bioluminescence through the oxidation of aldehydes to the corresponding carboxylates, promises implementation in artificial enzyme cascades for the synthesis of carboxylic acids. These findings advance the bio-based detection, preparation and transformation of industrially important aldehydes in living cells.

α- and β-Functionalized Ketones from 1,3-Dienes and Aldehydes: Control of Regio- and Enantioselectivity in Hydroacylation of 1,3-Dienes.

Ketones are among the most widely used intermediates in organic synthesis, and their synthesis from inexpensive feedstocks could be quite impactful. Regio- and enantioselective hydroacylation reactions of dienes provide facile entry into useful ketone-bearing chiral motifs with an additional latent functionality (alkene) suitable for further elaboration. Three classes of dienes, 2- or 4-monosubstituted and 2,4-disubstituted 1,3-dienes, undergo cobalt(I)-catalyzed regio- and enantioselective hydroacylation, giving products with high enantiomeric ratios (er). These reactions are highly dependent on the ligands, and we have identified the most useful ligands and reaction conditions for each class of dienes. 2-Substituted and 2,4-disubstituted dienes predominantly undergo 1,2-addition, whereas 4-substituted terminal dienes give highly enantioselective 4,1- or 4,3-hydroacylation depending on the aldehyde, aliphatic aldehydes giving 4,1-addition and aromatic aldehydes giving 4,3-addition. Included among the substrates are feedstock dienes, isoprene (US$1.4/kg) and myrcene (US$129/kg), and several common aldehydes. We propose an oxidative dimerization mechanism that involves a Co(I)/Co(III) redox cycle that appears to be initiated by a cationic Co(I) intermediate. Studies of reactions using isolated neutral and cationic Co(I) complexes confirm the critical role of the cationic intermediates in these reactions. Enantioselective 1,2-hydroacylation of 2-trimethylsiloxy-1,3-diene reveals a hitherto undisclosed route to chiral siloxy-protected aldols. Finally, facile syntheses of the anti-inflammatory drug (S)-Flobufen (2 steps, 92% yield, >99:1 er) and the food additive (S)-Dihydrotagetone (1 step, 83% yield; 96:4 er) from isoprene illustrate the power of this method for the preparation of commercially relevant compounds.

Rapid HPLC–MS/MS Detection of Aliphatic Aldehyde Formation in Four Vegetable Oils from Different Frying Processes

Rapid HPLC–MS/MS Detection of Aliphatic Aldehyde Formation in Four Vegetable Oils from Different Frying Processes

Pd-Catalyzed β-C-H Arylation of Aldehydes and Ketones Based on a Transient Directing Group.

The direct Pd-catalyzed β-C-H arylation of aldehydes and ketones was developed by using 2-amino-N,N'-diisopropylsuccinamide as a novel transient directing group (TDG). The TDG showed good versatility in functionalizing unactivated β-C-H bonds of aldehydes and ketones. It was effective not only for aliphatic aldehydes and ketones but also for aromatic aldehydes and ketones. Besides, it was applicable to o-methylbenzaldehydes.

Aggregation of Surfactants: Catalytic Reinforcement in Oxidation of Unsaturated E-Crotonaldehyde

Abstract In this work, the kinetics of the micellar catalyzed oxidation of the unsaturated aliphatic aldehyde, E-crotonaldehyde in aqueous medium under pseudo 1st-order reaction condition was spectrophotometrically investigated at 25 °C. In the spectrophotometric measurement, the rate of the reaction was recorded by the decreasing intensity of the metallic oxidant, hexavalent chromium [Cr(VI)], in acidic aliquots at 450 nm with varying concentration of surfactants and/or heteroaromatic promoters. Spectral evidences have been produced in favour of the mechanistic approach and the product formation.

Copper Catalyzed‐TBHP/DTBP Promoted C(sp2)−H Bond Scission of Aldehydes: An Approach to Transform Aldehyde to Esters

AbstractThe direct oxidative C(sp2)−H functionalization represents a step and atom economical approach for the utilization of aldehyde as promising acyl surrogates. A mild and practical copper catalyzed‐TBHP/DTBP promoted esterification of aldehydes in the presence of alkyl halides and alcohols has been developed. This strategy relies on naturally abundant aldehydes as acyl precursors, which can further couple with readily available alkyl halides/alcohols to transform into esters. Preliminary mechanistic investigations reveal that aldehyde in the presence of tert‐butoxy radical transforms into acyl radical. This protocol exhibits a broad substrate scope along with wide functional group compatibility and is applicable to a wide range of aldehydes, including challenging aliphatic aldehydes to undergo the C(sp2)−H bond scission to furnish the desired esters in good to excellent yields.

Catalytic Enantioselective Addition of Alkylzirconium Reagents to Aliphatic Aldehydes.

A catalytic methodology for the enantioselective addition of alkylzirconium reagents to aliphatic aldehydes is reported here. The versatile and readily accessible chiral Ph-BINMOL ligand, in the presence of Ti(OiPr)4 and a zinc salt, facilitates the reaction, which proceeds under mild conditions and is compatible with functionalized nucleophiles. The alkylzirconium reagents are conveniently generated in situ by hydrozirconation of alkenes with the Schwartz reagent. This work is a continuation of our previous work on aromatic aldehydes.