Aliphatic Aldehydes Research Articles

Aldehyde-based Activation of C2α-lactylthiamin Diphosphate Decarboxylation on Bacterial 1-deoxy-d-xylulose 5-phosphate Synthase.

1-Deoxy-d-xylulose 5-phosphate synthase (DXPS) catalyzes the thiamin diphosphate (ThDP)-dependent formation of DXP from pyruvate (donor substrate) and d-glyceraldehyde 3-phosphate (d-GAP, acceptor substrate) in bacterial central metabolism. DXPS uses a ligand-gated mechanism in which binding of a small molecule "trigger" activates the first enzyme-bound intermediate, C2α-lactylThDP (LThDP), to form the reactive carbanion via LThDP decarboxylation. d-GAP is the natural acceptor substrate for DXPS and also serves a role as a trigger to induce LThDP decarboxylation in the gated step. Additionally, we have shown that O2 and d-glyceraldehyde (d-GA) can induce LThDP decarboxylation. We hypothesize this ligand-gated mechanism poises DXPS to sense and respond to cellular cues in metabolic remodeling during bacterial adaptation. Here we sought to characterize features of small molecule inducers of LThDP decarboxylation. Using a combination of CD, NMR and biochemical methods, we demonstrate that the α-hydroxy aldehyde moiety of d-GAP is sufficient to induce LThDP decarboxylation en route to DXP formation. A variety of aliphatic aldehydes also induce LThDP decarboxylation. The study highlights the capacity of DXPS to respond to different molecular cues, lending support to potential multifunctionality of DXPS and its metabolic regulation by this mechanism.

Practical Access to Trisubstituted Morita‐Baylis‐Hillman‐Type Products Through Copper‐Catalyzed Reductive Aldol Reactions of Alkynones

AbstractWe report a convenient and diastereoselective copper‐catalyzed reductive alkynone aldol addition to aldehydes, with pinacolborane as stoichiometric reductant, that results in the generation of densely functionalized, trisubstituted (Z)‐enone products analogous to Morita‐Baylis‐Hillman adducts. We demonstrate that the reaction proceeds via an allenolborate, which we have characterized by NMR spectroscopy. A range of aromatic and aliphatic aldehydes can be reductively coupled with various non‐terminal alkynones.

Van der Waals interactions between nonpolar alkyl chains and polar oxide surfaces prevent catalyst deactivation in aldehyde gas sensing

Catalysis-based electrical sensing of volatile organic compounds on metal oxide surfaces is a powerful method for molecular discrimination. However, catalyst deactivation caused by the poisoning of catalytic sites by analytes and/or catalyzed products remains a challenge. This study highlights the underestimated role of van der Waals interactions between hydrophobic aliphatic alkyl chains and hydrophilic ZnO surfaces in mitigating catalyst deactivation during aliphatic aldehyde sensing. By immobilizing octadecylphosphonic acid (ODPA) on ZnO nanowire sensors, recovery times for nonanal detection are significantly reduced without compromising sensitivity. Temperature-programmed measurements demonstrate a reduction in desorption temperature of carboxylates on ODPA-modified ZnO to below 150 °C, whereas carboxylates on bare ZnO remain above 300 °C, indicating a significant decrease in catalyst deactivation. Density functional theory calculations reveal that accumulated van der Waals interactions between alkyl chains and ZnO surfaces significantly contributed to adsorption molecular kinetics. IR spectroscopy using deuterated self-assembled monolayers (SAMs) reveals conformational changes of alkyl chains within the SAMs caused by aldehyde adsorption, supporting the suggested adsorption kinetics. A model is proposed based on the dynamic surface-covering by alkyl chains destabilizes catalytically oxidized carboxylic acids.

Bio-inhibitive corrosion effect of carica papaya leaf extract on cold-rolled mild steel in 0.1 M HCl solution

Plant extracts are prone to microbial growth that can lead to microbial-induced corrosion (MIC), a major setback for their performance and stability as corrosion inhibitors. Hence, this work aims to identify the microbes that may cause the ineffectiveness of carica papaya leaf extract (CPLE) as a bio-corrosion inhibitor of cold-rolled mild steel in 0.1 M HCl solution for 48 days at 28℃. Cold-rolled mild steel coupons were immersed in 100 ml of 0.1 M hydrochloric (HCl) acid solution containing 1 g, 2 g, 3 g, 4 g, and 5 g of carica papaya leaf extract (CPLE) for 48 days at 28℃. The gravimetric method was used to determine the coupons' corrosion rate (CR), surface coverage, and inhibition efficiency (IE%) of the CPLE. The functional groups in the CPLE were identified using Fourier Transform Infrared Spectroscopy (FTIR), and the surface appearance of the coupons after immersion was examined using an atomic force microscope (AFM). Gravimetric data showed the coupons dipped in a 0.1 M HCl solution containing 3 g/100 ml of the inhibitor exhibited the highest inhibition efficiency of 87.73%, surface coverage of 0.88, and lowest corrosion rate of 0.00255 mm/day or 0.93 mm/yr, after 48 days at 28℃. In FTIR, transmittance peaks occurred at 1558 cm−1 for amines (-NH) in alkaloid scissoring, 1452 cm−1 for aromatic -C = C in flavonoids, 2932 cm−1 for aliphatic methylene (-CH2) and aldehyde (RCOH) stretching, 1035 and 1077 cm−1 for aromatic-OR in tannin, and 3280 cm−1 for out-of-plane bending of hydroxyl (-OH) in phenolics. Vitamin C (522,940 μg/g), flavonoids (860 μg/g), saponins (637.9 μg/g), terpenoid (48.4 μg/g), phenol (120%μg/g), alkaloid (4.18 μg/g), tannin (59.84%), and glycosides (9.04%) make up the extract's average phytochemical content. AFM presents pits and ridges on the mild steel coupons immersed in 0.1 M HCl solution without the extract. Those immersed in the solutions with varying concentrations of the extract had a passive layer of the CPLE adhering to the surfaces of the coupons thereby preventing the coupon’s direct contact with the acid solution and weight loss. However, over time, microbial growth decreased the efficiency of CPLE due to metabolites. Microbial tests show creamy, irregular and raised bacterial total colony-forming units per gram (Tcfu/g) as 4.6 × 105 Tcfu/g and 1.9 × 107 Tcfu/g in 2 runs. Also, a mixture of white and fluffy appearance and spore formation of fungi population of 4.8 × 105 Tcfu/g and 3.2 × 107 Tcfu/g in 2 Runs made up of Penicillium spp, Coccidioides immitis, Aspergillus flavus, and Fusarium spp, with hyphae, were seen in the solutions containing CPLE.

Synthesis of Perfluoroalkylated Pyrazoles from α-Perfluoroalkenylated Aldehydes

Within this study, we report a simple two-step process for the synthesis of perfluoroalkylated pyrazoles from aliphatic aldehydes. In the photocatalytic first step, the aldehydes are transformed into the corresponding perfluoroalkylated enals, which then undergo nucleophilic attack by hydrazine and subsequent ring closure, providing the fluorinated 3,4-substituted pyrazole products in a 64–84% yield. Using triphenylphosphine and imidazolidinone as organocatalysts, the method is operationally simple and omits heavy metal-containing waste.

Hydrazine‐Catalysed Ring‐Opening Metathesis Polymerization Of Cyclobutenes

AbstractMaterials formed by the ring‐opening metathesis polymerization (ROMP) of cyclic olefins are highly valued for industrial and academic applications but are difficult to prepare free of metal contaminants. Here we describe a highly efficient metal‐free ROMP of cyclobutenes using hydrazine catalysis. Reactions can be initiated via in situ condensation of a [2.2.2]‐bicyclic hydrazine catalyst with an aliphatic or aromatic aldehyde initiator. The polymerizations show living characteristics, achieving excellent control over molecular weight, low dispersity values, and high chain‐end fidelity. Additionally, the hydrazine can be used in substoichiometric amounts relative to the aldehyde chain‐end while maintaining good control over molecular weight and low dispersity values, indicating that a highly efficient chain transfer mechanism is occurring.

Benzyl Alcohol Functionalization of [1.1.1]Propellane with Alkanes and Aldehydes.

Bicyclo[1.1.1]pentanes (BCPs) play a crucial role in drug discovery research as C(sp3)-rich bioisosteres of benzene rings. However, the preparation of BCPs with strong alkane C(sp3)-H bonds has not been reported to date. In this study, we reported a method for light-induced benzyl alcohol functionalization of [1.1.1]propellane with aliphatic hydrocarbons (which have not previously been explored for this purpose) and aldehydes under metal- and photocatalyst-free conditions. The BCP products could be transformed into various useful derivatives, demonstrating the utility of the method. Notably, we achieved the synthesis of functionalized BCPs with simple alkanes.

Non-Ionic Peterson-Type Olefination Reactivity and its Use in a Silicon-Promoted Carbonyl-Carbonyl Cross Coupling Reaction.

The [2+2] cycloaddition reaction between the Si=C double bond of adamantylsilene and the carbonyl group of aliphatic, aromatic or acetylenic ketones and aldehydes is demonstrated. The product of this reaction that is central to a non-ionic version of the Peterson olefination is an unusual four-membered 1,2-silaoxetane heterocycle that was characterized spectroscopically and crystallographically. In the presence of SiO2, the silaoxetane undergoes retro-cycloaddition with the formation of alkene products. As the [2+2] cycloaddition proceeds without the necessity of any base, enolizable ketones can be converted into olefins. In addition, it is shown that the adamantylsilene can be produced in situ by a sila-Peterson reaction, providing valuable input for the development of a new one-pot silicon-based reductive carbonyl-carbonyl cross coupling methodology.

Ascorbic Acid: An Efficient Organocatalyst for the Synthesis of 2‐Amino‐1,3,4‐oxadiazoles and Thiadiazoles via C−X Bond Formation

AbstractA new protocol for the synthesis of 2‐amino‐substituted 1,3,4‐oxadiazoles and 1,3,4‐thiadiazoles, were developed using semicarbazide or thiosemicarbazide along with the various aldehydes, followed by C−X (X=O, S) bond formation using ascorbic acid as a catalyst. This rapid, efficient, accessible, and robust/scalable sequential synthesis works with aromatic, aliphatic, and cinnamic aldehydes to provide a wide range of diazole derivatives with a 2‐amino substituent without the use of any transition metals. The synthesised molecules were characterised by 1H and 13C NMR analysis.

Electroinduced Reductive and Dearomative Alkene-Aldehyde Coupling.

The direct coupling of alkene feedstocks with aldehydes represents an expedient approach to the generation of new and structurally diverse C(sp3)-hybridized alcohols that are primed for elaboration into privileged architectures. Despite their abundance, current disconnection strategies enabling the direct coupling of carbon-carbon π-bonds and aldehydes remain challenging because contemporary methods are often limited by substrate or functional group tolerance and compatibility in complex molecular environments. Here, we report a coupling between simple alkenes, heteroarenes and unactivated aliphatic aldehydes via an electrochemically induced reductive activation of C-C π-bonds. The cornerstone of this approach is the discovery of rapid alternating polarity (rAP) electrolysis to access and direct highly reactive radical anion intermediates derived from conjugated alkenes and heterocyclic compounds. Our developed catalyst-free protocol enables direct access to new and structurally diverse C(sp3)-hybridized alcohol products. This is achieved by the controlled reduction of conjugated alkenes and the C2-C3 π-bond in heteroarenes via an unprecedented reductive dearomative functionalization for heterocyclic compounds. Experimental mechanistic studies demonstrate a kinetically biased single-electron reduction of C-C π-bonds over aldehydes. Application of rAP enables chemoselective generation of olefinic radical anion intermediates and avoids undesired saturative overreduction. Overall, this technology provides a versatile approach to the reductive coupling of olefin and heterocycle feedstocks with aliphatic aldehydes, offering straightforward access to diverse C(sp3)-rich oxygenated scaffolds.

Inhibitory activity of some short-chain aliphatic aldehydes on pheromone and ammonium carbonate-mediated attraction in olive fruit fly, Bactrocera oleae.

The olive fruit fly (OFF), Bactrocera oleae (Rossi), is the main insect pest of olive trees worldwide. Legislation limits to the use of some synthetic larvicidal insecticides is leading to the development of new control options for preventive control of adult flies. In the present study, the biological activity of four short-chain aliphatic aldehydes, namely hexanal, (E)-2-hexenal, heptanal and (E)-2-heptenal, previously reported as repellents to the OFF adults was investigated. Electroantennography (EAG) recordings showed that antennae of OFF males and females are able to perceive the test compounds in a wide range of doses. In field trapping experiments, reservoir-type polypropylene (PP) membrane dispensers loaded with individual compounds did not elicit a significant attraction of OFF males and females. On the contrary, a significant reduction of male catches was noticed when sex pheromone dispensers and PP membrane dispensers, loaded with one of the test compounds, were applied on the same white sticky traps ≈20 cm apart. Likewise, male and female catches in yellow sticky traps baited with ammonium carbonate (AC) dispensers as food attractant were significantly reduced by the presence of PP membrane dispensers of individual aliphatic aldehydes on the same traps. In small plots control trials, solid formulations of the four aldehydes into a bentonite clay support induced a significant reduction of the OFF active infestation mainly when C6 and C7 aldehyde-activated bentonites were used. Short-chain aliphatic aldehydes showed inhibitory effects on sex pheromone and food attractant-mediated attraction of OFF. Results of field trials suggest potential of short-chain aliphatic aldehydes to develop new semiochemical-based OFF control options. © 2024 Society of Chemical Industry.

Studies on the pyrolysis and potential flame retardancy of low-substituted starch phosphates

Investigations on the pyrolysis and potential flame retardancy imparted by solvent-free and semi-dry phosphorylation of different starches using sodium orthophosphates were conducted. The samples – low-substituted starch phosphates (SP) with degrees of substitution DSP < 0.5 - were subjected to differential scanning calorimetry, thermogravimetry coupled with evolved gas analysis and pyrolysis – gas chromatography – mass spectrometry. The data obtained as well as features of charring residues examined using microscopic and spectroscopic methods were related to structural aspects of SP – analysed by means of various spectroscopic techniques - and compared with those of native starches. It was found that charring and polyphosphate formation and the thermal resistance of the solid SP residues increased significantly if the DSP was at least 0.1. Accordingly, the exothermal decomposition, the temperature-induced loss of mass and the decomposition rates of SP decreased distinctly compared to native starch. The activation temperatures of SP and the formation of low-molecular pyrolysis products including aliphatic, cyclic, and aromatic aldehydes and ketones as well as anhydrosugars decreased markedly, even at DSP < 0.1. The results confirm the potential flame-retardancy of SP achieved by flame-inhibiting effects, despite low phosphorylation degrees, in both the gas and condensed phases.

Phytochemical and pharmacological investigation of the non-volatile compounds of Lepidium cartilagineum (J. C. Mayer) Thell. and determination of the essential oil composition of its flowers and fruits

Eighteen compounds, among them phenylpropanoids (1–2), neolignans (3–9), a megastigmane (10), a phenyl glucoside (11), flavonoids (12–14), and N-containing compounds (15–18) were isolated from the methanolic extract of the whole plant of L. cartilagineum. The structures of the compounds were determined by NMR and MS measurements. The composition of the essential oils prepared from the flowers and fruits of L. cartilagineum was investigated using GC and GC–MS measurements. The essential oils were rich in aliphatic aldehydes and hydrocarbons, but low in sulfur-containing compounds, e.g., isothiocyanates. The extracts prepared from the aerial parts and roots of the plant, the essential oil, and the isolated compounds (1–9) were tested for antiproliferative activity against COLO 205 and COLO 320 cell lines and antibacterial activity on Lactobacillus rhamnosus. Dehydrodiconiferyl alcohol γ’-methyl ether (5) possessed marked antiproliferative activity against both human tumor cell lines. Neither the extracts nor the compounds affected the growth of the bacteria and did not influence the biofilm formation of L. rhamnosus. Based on the results, it can be concluded that L. cartilagineum is non-toxic to the human gut microbiome forming L. rhamnosus.

Visible Light-Mediated Co(II) Catalyzed Synthesis of α,β-Epoxy Ketones by Oxidative Coupling of Alkenes and Aldehydes in Water.

A one-step, two-component visible light-mediated CoCl2·6H2O-catalyzed oxidative acylation of alkenes by aldehydes to synthesize α,β-epoxy ketone has been achieved in water at room temperature. The photocatalytic activity of Co(II) presented a remarkable achievement for synthesis of α,β-epoxy ketones from aldehydes and olefins, with a wide substrate compatibility including aromatic, heteroaromatic and aliphatic aldehydes, styrenes with both electron-donating and withdrawing groups, α-substituted styrenes, stilbene, acrylates, and even the challenging unactivated aliphatic alkenes. Mechanistic studies including radical trapping experiments, intermediate detection by GCMS, Hammett analysis, and DFT studies unveil the nature of the photocatalytic pathway.

Uncovering a general oxidation model of nitrogen-containing oxidant in N-heterocyclic carbene (NHC) catalyzed oxidative reactions of aldehydes

Predicting how oxidants interact with reactive partners to alter the oxidation mechanism is a significant challenge in carbene catalysis. In this study, we investigated several examples to address this issue. Using density functional theory (DFT), we explored N-heterocyclic carbene (NHC)-catalyzed oxidative [2 + 4] annulations of aliphatic aldehydes with α,β-unsaturated ketones, focusing on the role of nitrogen-containing oxidant. Our computational results reveal that a hydrogen-bonding bridge framework, formed during oxidation, is crucial for facilitating π···π stacking interactions between the oxidant and the NHC catalyst. These interactions significantly lower the oxidation energy barrier, enabling a facile hydride transfer. This mechanism was validated across other reactions involving different nitrogen-containing oxidants. Frontier molecular orbital (FMO) analysis demonstrates how the NHC catalyst lowers the cycloaddition energy barrier by altering the orbital overlap from shoulder-to-head to head-to-head. Additionally, this elucidates the origin of stereoselectivity by highlighting energy differences between two reacting components at cycloaddition transition states. The nucleophilic index further predicts the preferred ketone attack site. This work advances our understanding of oxidation mechanisms involving nitrogen-containing oxidants and offers valuable insights for designing potent organic oxidants in organocatalytic oxidative reactions.

Copper-Catalyzed Direct Asymmetric Aldol Reaction of Glycine Schiff Bases to Access syn-β-Hydroxy-α-amino Esters.

This study reported a copper-catalyzed direct asymmetric aldol reaction between aldehydes and glycine Schiff bases with methyl, allyl, and tert-butyl esters. Additionally, this reaction afforded high yields of syn-β-hydroxy-α-amino esters with excellent enantio- and diastereoselectivities (93-99% ee, up to >99:1 dr). The aldol reaction accepted aromatic, linear aliphatic, and α-substituted aliphatic aldehydes.

Sanguisorba officinalis L. ethanolic extracts and essential oil - chemical composition, antioxidant potential, antibacterial activity, and ex vivo skin permeation study.

Sanguisorba officinalis L. is classified as a medicinal plant and used in traditional medicine. The root of this plant is mainly used as a medicinal raw material, but the above-ground parts are also a valuable source of health-promoting biologically active compounds. The study aimed to evaluate the antioxidant activity and total polyphenol content (TPC) of extracts prepared in 70% and 40% aqueous ethanol solution (dry extract content 50-500g/L) from the aerial parts of S. officinalis. The essential oil was isolated from the tested raw material, and its composition was determined using GC-MS. Ethanolic extracts and essential oil have been tested for antibacterial activity. The extract in 70% v/v ethanol (dry extract content: 500g/L) was subjected to HPLC analysis for the content of selected phenolic acids and an ex vivo skin permeation study. The ability of these metabolites to permeate and accumulate in the skin was analysed. Extracts prepared at both ethanol concentrations showed similar antioxidant activity and TPC. Depending on the method, concentration of solvent, and dry extract content (50-500g/L), the activity ranged from 1.97 to 84.54g Trolox/L. TPC range of 3.80-37.04gGA/L. Gallic acid (424mg/L) and vanillic acid (270mg/L) had the highest concentrations among the phenolic acids analysed. Vanillic acid (10μg) permeates the skin at the highest concentration. The highest accumulation in the skin was found for 2,5-dihydroxybenzoic acid (53μg/g skin), 2,3-dihydroxybenzoic acid (45μg/g skin), and gallic acid (45μg/g skin). The tested ethanolic extracts exhibited antibacterial activity. Samples with a dry extract concentration of 500g/L showed the largest growth inhibition zones. The most sensitive strains to these extracts were P. aeruginosa (24mm), S. lutea (23mm), and S. pneumoniae (22mm). The smallest inhibition zones were observed for B. subtilis (17mm). The essential oil showed weaker antimicrobial activity (growth inhibition zone 8-10mm). The GC-MS method identified 22 major components of the essential oil, including aliphatic hydrocarbons, unsaturated terpene alcohols, aliphatic aldehydes, unsaturated and saturated fatty acids, sesquiterpene, phytyl ester of linoleic acid, nitrogen compound, phytosterol, terpene ketone, phenylpropanoids, aliphatic alcohol, diterpenoid, aromatic aldehyde, and aliphatic carboxylic acid. The conducted research has shown that ethanolic extracts from Sanguisorbae herba are a valuable source of compounds with antibacterial and antioxidant potential, including phenolic acids. The fact that selected phenolic acids contained in the tested extract have the ability to permeate and accumulate in the skin provides the basis for conducting extended research on the use of extracts from this plant raw material in cosmetic and pharmaceutical preparations applied to the skin.

Cyclopropanation with Non-Stabilized Carbenes via Ketyl Radicals.

A radical mechanism enables simple and robust access to nonstabilized, alkyl iron carbenes for novel (2 + 1) cycloadditions. This Fe-catalyzed strategy employs simple, aliphatic aldehydes as carbene precursors in a practical, efficient, and stereoselective cyclopropanation. This air- and water-tolerant method permits convenient generation of iron carbenes and coupling to an exceptionally wide range of sterically and electronically diverse alkenes (nucleophilic, electrophilic, and neutral). A transient ketyl radical intermediate is key to accessing and harnessing this rare, alkyl iron carbene reactivity. Mechanistic experiments confirm the (a) intermediacy of ketyl radicals, (b) iron carbene formation by radical capture, and (c) nonconcerted nature of the (2 + 1) cycloaddition.

Photo-Activated Carbon Dots as Catalysts in Knoevenagel Condensation: An Advance in the Synthetic Field

Photoinduced chemical reactions and the development of new materials represent a current and significant topic. We present a sustainable and eco-friendly approach to the Knoevenagel condensation reaction involving carbonyl and active methylene compounds. Our method utilizes photo-activated carbon dots (CDs) derived from 5-hydroxymethylfurfural (5HMF) within an aqueous medium and does not require acidic, basic, or thermal conditions. This protocol operates effectively with aromatic, aliphatic, and heteroaromatic aldehydes and ketones. The 5HMF-derived-CDs can be reused four times without significant loss of activity. Moreover, this methodology is suitable for scaling up reactions, thereby highlighting its potential for industrial applications.

Hydrazine-Catalysed Ring-Opening Metathesis Polymerization Of Cyclobutenes.

Materials formed by the ring-opening metathesis polymerization (ROMP) of cyclic olefins are highly valued for industrial and academic applications but are difficult to prepare free of metal contaminants. Here we describe a highly efficient metal-free ROMP of cyclobutenes using hydrazine catalysis. Reactions can be initiated via in situ condensation of a [2.2.2]-bicyclic hydrazine catalyst with an aliphatic or aromatic aldehyde initiator. The polymerizations show living characteristics, achieving excellent control over molecular weight, low dispersity values, and high chain-end fidelity. Additionally, the hydrazine can be used in substoichiometric amounts relative to the aldehyde chain-end while maintaining good control over molecular weight and low dispersity values, indicating that a highly efficient chain transfer mechanism is occurring.