Oxirane Ring Opening Research Articles

Valorisation of food waste into bio-based polyurethane rigid foams: From experimental investigation to techno-economic analysis

Food waste (FW) constitutes a significant portion of municipal solid waste and thus requires proper treatment. A ‘waste-to-wealth’ concept, in this case, urges the valorisation of FW to produce value-added products, given that such waste contains significant quantities of diverse nutrients. While most of these efforts have been focused on the recovery of carbohydrates, this paper introduces an FW biorefinery scheme to valorise FW lipids (FWLs) into bio-based polyols for polyurethane rigid foams (PURF). Considering economic viability, cost-effective dosages of enzymes for FW hydrolysis were first investigated. Subsequently, the obtained FWLs were converted into bio-based polyols through stepwise epoxidation and oxirane ring-opening. Characterisation results showed that FW hydrolysis aided the development of FWL-derived polyols into PURF. Moreover, the obtained PURF exhibited excellent properties that are suitable for thermal insulation applications in the fields of civil engineering and appliances. A further techno-economic analysis demonstrated a promising profitability of valorising FW into PURF. Proven as material-intensive, critical cost drivers of the proposed valorisation scheme mainly included the price of the PURF and the chemicals required for the synthesis. The FW processing rate also significantly influenced the economic viability. By providing a successful valorisation pathway from FW to PURF and highlighting vital economic variables, this work aims to provide insights to promote the sustainable development of FW biorefineries and relevant bio-based polymer industries.

FeCl3-catalyzed regioselective ring-opening of aryl oxirane with 4-hydroxycoumarin for the synthesis of furo[3,2-c]coumarins.

The regioselective ring-opening of aryl oxiranes was investigated with various 4-hydroxycoumarins in dimethyl sulfoxide in the presence of 20 mol% FeCl3 as a catalyst at 110 °C. This approach provided a short and concise synthetic route for the regioselective synthesis of 2-aryl-4H-furo[3,2-c] coumarin derivatives. Product formation occurred through regioselective ring-opening of the aryl oxirane at a less hindered site, followed by dehydration and concomitant cyclization. The salient features of our protocol were: cost-effectiveness; short reaction time; step- and atom economy; easy handling; broad scope of substrates; regioselectivity; good-to-excellent yields; non-requirement of dry solvents, co-catalysts, ligands, or any other additives; inert atmospheric conditions.

Catalytic Asymmetric Oxirane Ring Opening with Chirally-Modified PCN-222 MOF

Catalytic Asymmetric Oxirane Ring Opening with Chirally-Modified PCN-222 MOF

Polyols from castor oil (Ricinus communis) and epoxidized soybean oil (Glycine max) for application as a lubricant base

AbstractPolyols are widely synthesized from fossil sources and applied in multiple sectors of the industry as raw material for polyurethane production and also as lubricants. Although the preparation method normally used is efficient and practical, it is necessary to develop environmentally friendly synthesis route that reduce pollution. This study focuses on an alternative synthetic route for the synthesis of polyols using only raw materials from renewable sources. Polyols were successfully obtained by modifying castor oil and epoxidized soybean oil through transesterification, transamidation and oxirane ring opening. The polyols were then characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (1H and 13C‐NMR), acidity index (AI), thermogravimetry (TGA), differential scanning calorimetry (DSC), size exclusion chromatography (SEC), dynamic viscosity and exploratory scanning of ecotoxicological parameters using Artemia salina. The results highlight the promising potential of transamidated castor oil (TACO) polyol in the field of biolubricants, attributed to its high viscosity index, oxidative stability and, ecofriendly behavior.

Synthesis of 2,2-Disubstituted and 2,2,3-Trisubstituted 1,4-Dioxane-Derived Building Blocks

AbstractAn approach to the preparation of 2,2-disubstituted and 2,2,3-trisubstituted 1,4-dioxane-derived building blocks is described. The reaction sequence commenced from dimethyl- or spirocyclobutyl-substituted oxiranes bearing an additional benzyloxy group as the starting materials. The key step of the 1,4-dioxane ring construction included oxirane ring opening with ethylene glycol monolithium salt, followed by the two-step cyclization of the diols obtained. The utility of the method was demonstrated by multigram preparation (up to 300 g; 30 g average scale of the final products) of 2,2-dimethyl-1,4-dioxane and 5,8-dioxaspiro[3.5]nonane building blocks, i.e. carboxylic acids, alcohols, amines, aldehyde, ketones, and bromides. Additional synthetic possibilities were shown by the preparation of selected examples of 1,4-dioxane-containing acetylenes, thiols, sulfonyl halides, and sulfonamides.

Oxidative Ring-Opening Transformation of 5-Acyl-4-pyrones as an Approach for the Tunable Synthesis of Hydroxylated Pyrones and Furans.

A selective and tunable approach for oxidation of 4-pyrones has been developed via ring-opening transformations leading to various hydroxylated oxaheterocycles. The first step of the strategy includes the base-catalyzed epoxidation of 5-acyl-4-pyrones in the presence of hydrogen peroxide for the effective synthesis of pyrone epoxides in high yields. The epoxides bearing the CO2Et group are reactive molecules that can undergo both pyrone and oxirane ring-opening via deformylation to produce hydroxylated 2-pyrones or 4-pyrones. The acid-promoted transformation led to 3-hydroxy-4-pyrones (24-76% yields), whereas the K2CO3-catalyzed ring-opening process of 2-carbethoxy-4-pyrone epoxides proceeded as an attack of alcohol at the C-3 position bearing the CO2Et group to give functionalized 6-acyl-5-hydroxy-2-pyrones (27-87% yields). The base-catalyzed reaction of 2-aryl-4-pyrone epoxides was followed by ring contraction and the dearoylation process to produce 3-hydroxyfuran-2-carbaldehydes in 42-80% yields. The transformation of 3-aroylchromone epoxides led to flavonols and 3-hydroxybenzofuran-2-carbaldehyde in the acidic and basic conditions, respectively. The prepared hydroxylated heterocycles demonstrated high reactivity for further transformations and low cytotoxicity and are promising fluorophores or UV filters.

Mechanochemical Degradation of Poly(vinyl chloride) into Nontoxic Water-Soluble Products via Sequential Dechlorination, Heterolytic Oxirane Ring-Opening, and Hydrolysis.

As one of the most widely used commodity plastics, poly(vinyl chloride) (PVC) is extensively used worldwide, yet is difficult to recycle and is often discarded immediately after use. Its end-of-life treatment often generates toxic hydrogen chloride and dioxins that pose a critical threat to ecosystems. To address this challenge, the mechanochemical degradation of PVC into water-soluble biocompatible products is presented herein. Oxirane mechanophores are strategically introduced into the polymeric backbone via sequential dechlorination followed by epoxidation. The oxirane mechanophore in the polymer backbone undergoes a force-induced heterolytic ring-opening to carbonyl ylide intermediates, which eventually generates acetals during the course of the reaction. The subsequent hydrolysis of the backbone acetals affords the scission of the polymeric chain into water-soluble low-molecular-weight fragments. Combined with its low cytotoxicity and phytotoxicity, this solvent-free mechanochemical degradation process offers a green alternative for the degradation of PVC.

Imidazolium-based ionic liquid supported layered silicate HUS-7 as an active catalyst for ring opening of oxiranes

Imidazolium-based ionic liquid supported layered silicate HUS-7 as an active catalyst for ring opening of oxiranes

A combined experimental and computational chiroptical approach to establish the biosynthesis and absolute configuration of licochalcone L

Often, chiral natural products exist as single stereoisomers; however, simultaneous occurrences of both enantiomers can exist in nature, resulting in scalemic or racemic mixtures. Ascertaining theabsolute configuration (AC) of natural products is pivotal for attributing their specific biological signature. Specific rotation data commonly characterize chiral non-racemic natural products; however, measurement conditions, viz., solvent and concentration, can influence the sign of specific rotation values, especially when characterizing natural products possessing small values. For example, licochalcone L, a minor constituent of Glycyrrhiza inflata, was reported with a specific rotation of [α]D22= +13 (c 0.1, CHCl3); however, not establishing the AC and the reported zero specific rotation for an identical compound, licochalcone AF1, resulted in debatable chirality and its biogenesis. In this study, a combined experimental and computational chiroptical approach involving specific rotation and electronic circular dichroism (ECD) data, supported by time-dependent density functional theory (TDDFT), were effectively utilized to establish the AC of licochalcone L as the (E, 2″S)-isomer. Establishing the 2″S absolute configuration permitted the conception of a reasonable biosynthetic pathway involving intramolecular ‘5-exo-tet’ ring opening of a chiral oxirane to form chiral licochalcone L in G. inflata.

Synthesis of Polyurethane from Apricot Kernel Oil and Characterization

In the study, natural origin polyol was obtained from apricot kernel oil. The obtained polyol was used in the synthesis of polyurethane, which is an industrially important polymer. Obtaining polyol from apricot kernel oil was firstly epoxidized with a two-step process and then converted to the desired polyol structure by oxirane ring opening. The obtained biocompatible polyol structure was subjected to polymerization process with the hexamethylene diisocyanate structure. The obtained polyurethane structures were characterized chemically, thermally and morphologically. The chemical structure was investigated by FTIR spectra. The thermal stability, Tg values and decomposition temperatures of the obtained polyurethane structure were investigated by TGA, DTA and DSC techniques. The basic morphological features of the polyurethane structure were evaluated by SEM analysis.

The Mechanism of Frabot Test for Uric Acid

Uric acid is an Analyte. Excess uric acid ─ hyperuricemia ─ leads to gout and renal stones. Frabot noted that uric acid added to an alkaline tungstate solution developed an intense blue colour. A colorimetric method widely utilized to quantify uric acid depends on the reduction of the chromogen sodium tungstate by uric acid to produce a measurable colour change. The reaction route from the initial products to the coloured compounds and the oxido-degradation of the organic substance has not been advanced. In this communication the electron flow is given in each step of the series of reactions that take place. These are isomerization to imidol, Michael addition to enone, oxirane formation in a redox step, hydrolysis of imido group, oxirane ring opening, ring contraction to five- member ring, ring opening via alkoxide, and finally assisted decarboxylation to the end product, 5-ureido hydantoin (allantoin).

Nucleophilic epoxide ring opening in the system "epichlorohydrin–carboxylic acids–tetrabutylammonium iodide–solvent (e=15.1–28.7)"

The mechanism of the oxirane ring opening by carboxylic acids with different volume of substituents in the system "epichlorohydrin(ЕCH)–RCOOH–tetrabutylammonium iodide–solvent (=15.1–28.7)" was studied in the excess of ECH at the temperatures of 40–800C by methods of chemical kinetics and correlation analysis. The effects of solvent polarity (ECH and its mixtures with THF and nitrobenzene), temperature, and spatial structure (topological steric effect index TSEI) of carboxylic acids on the proceeding of the reaction were investigated. The structure of the reaction products was determined by gas chromatography–mass and 1H NMR spectroscopy. It was found that the reaction accelerates with a decrease in the solvent polarity, an increase in temperature and steric effect in the structure of the reagent. It was shown that the tetraalkylammonium carboxylate (R'4N+–OOCR) which formed in situ causes the final product formation in the rate-determining step of the reaction mechanism.

Chiral Indolizinium Salts Derived from 2-Pyridinecarbaldehyde-First Diastereoselective Syntheses of (-)-1-epi-lentiginosine.

The first diastereoselective synthesis of (-)-1-epi-lentiginosine from a common chiral trans-epoxyamide derived from 2-pyridincarbaldehyde is reported. This methodology involves a sequential oxirane ring opening and intramolecular 5-exo-tet cyclization of tosylate trans-epoxyalcohol to afford a diastereomeric mixture of indolizinium salts in a one-pot fashion, followed by regio- and diastereospecific pyridinium ring reduction.

Synthesis and Frictional Characteristics of Bio-Based Lubricants Obtained from Fatty Acids of Castor Oil

The depletion of oil reserves and concerns about the environmental impact of the use and incorrect disposal of mineral lubricants have been promoting the development of bio-based lubricants. In this study, biolubricants obtained from fatty acids of castor oil were synthesized by esterification (>wt.%93), epoxidation (>wt.%92), and oxirane ring opening reactions using water (>wt.%92) or 2-ethylhexanol (>wt.%94) as nucleophilic agents. The frictional characteristics of the synthesized samples were obtained through tribological tests performed in a four-ball tester and compared with a commercial mineral oil. The sample obtained through oxirane ring opening with water showed the best frictional performance (FC = 0.0699 ± 0.0007) among the prepared samples, with equivalent wear rate (WSD = 281.2 ± 5.54 μm) and ca. 20% lower friction coefficient when compared to the commercial mineral oil, indicating its great potential for replacing mineral fossil oils.

Evaluation of adhesion and corrosion wear resistance of biobased polymers derived from linseed oil deposited on Fe-Zn sheets

The objective of this paper is to study adherence and corrosion wear resistance of biobased polymers derived from epoxidized linseed oil (ELO) deposited on galvanized iron sheets. The adhesion and anticorrosive properties of the pure epoxy resin (ELO) were compared with those that contained bisphenol A (BFA) and carbon black (CB), which were polymerized by oxirane ring opening catalyzed by aluminum triflate (ATf). Fourier Transform Infrared Spectroscopy (FTIR) confirmed the formation of the different biobased polymers as coatings. To evaluate the performance to the corrosion resistance each coating was tested to adhesion and accelerated weathering within a salt spray chamber. The use of BFA provided greater adhesion than pure ELO coatings. Additionally, the addition of small loads of CB improved the appearance, adhesion, and durability of the coating, thus decreasing the corrosion of the galvanized sheets. Finally, the interactions that occur at the interface between the different polymeric matrices and the substrate surface, which allow improving the corrosion resistance were analyzed.

Convenient Synthesis of N-Heterocycle-Fused Tetrahydro-1,4-diazepinones.

A general approach towards the synthesis of tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepin-4-one, tetrahydro[1,4]diazepino[1,2-a]indol-1-one and tetrahydro-1H-benzo[4,5]imidazo[1,2-a][1,4]diazepin-1-one derivatives was introduced. A regioselective strategy was developed for synthesizing ethyl 1-(oxiran-2-ylmethyl)-1H-pyrazole-5-carboxylates from easily accessible 3(5)-aryl- or methyl-1H-pyrazole-5(3)-carboxylates. Obtained intermediates were further treated with amines resulting in oxirane ring-opening and direct cyclisation-yielding target pyrazolo[1,5-a][1,4]diazepin-4-ones. A straightforward two-step synthetic approach was applied to expand the current study and successfully functionalize ethyl 1H-indole- and ethyl 1H-benzo[d]imidazole-2-carboxylates. The structures of fused heterocyclic compounds were confirmed by 1H, 13C, and 15N-NMR spectroscopy and HRMS investigation.

Enthalpy–Entropy Compensation in Reactions of Oxirane Ring Opening

Enthalpy–Entropy Compensation in Reactions of Oxirane Ring Opening

Potential of Crude Tall Oil Polyols for Rigid Polyurethane Foam Production and their Comparison with Tall Oil Fatty Acids Polyols

Tall oils are a second-generation feedstock with perspective use in polyurethane materials. This study compared crude tall oil and tall oil fatty acid bio-polyols to determine whether crude tall oil could be used for polyurethane foam production making the production more cost-effective. Polyols were synthesized in a two-step process. At first, double bond epoxidation followed by oxirane ring-opening, and transesterification with multifunctional alcohols. The epoxidation process was studied with acid value and relative conversion to oxirane analysis. The obtained polyols were analyzed for acid value, hydroxyl value, viscosity, and with Fourier transform infrared spectroscopy analysis. The results showed suitable hydroxyl values for almost all polyols, including crude tall oil polyols, but the high viscosity limits the use of most of the polyols.

Bis(oxiranes) Containing Cyclooctane Core: Synthesis and Reactivity towards NaN3.

Reactions of oxirane ring opening provide a powerful tool for regio- and stereoselective synthesis of polyfunctional and heterocyclic compounds, widely used in organic chemistry and drug design. Cyclooctane, alongside other medium-sized rings, is of interest as a novel molecular platform for the construction of target-oriented leads. Additionally, cyclooctane derivatives are well known to be prone to transannular reactions, which makes them a promising object in the search for novel approaches to polycyclic structures. In the present work, a series of cyclooctanediones was studied in Corey-Chaykovsky reactions, and novel spirocyclic bis(oxiranes) containing cyclooctane core, namely, 1,5-dioxadispiro[2.0.2.6]dodecane and 1,8-dioxadispiro[2.3.2.3]dodecane, were synthesized. Ring opening of the obtained bis(oxiranes) upon treatment with sodium azide was investigated, and it was found that the reaction path is determined by the reciprocal orientation of oxygen atoms in the oxirane moieties. Diastereomers of the bis(oxiranes) with cis-orientation underwent independent ring opening, supplying corresponding diazidodiols, while in the case of stereoisomers with trans-orientation, domino-like reactions occurred, including intramolecular nucleophilic attack and the formation of a novel three- or six-membered O-containing ring. Summarily, a straightforward approach to polyfunctional compounds containing cyclooctane or oxabicyclo[3.3.1]nonane cores, employing bis(oxiranes), was elaborated.

Esters from castor oil functionalized with aromatic amines as a potential lubricant

AbstractVegetable oils are very promising alternatives to fossil lubricants due to their abundance, low cost, excellent performance, and environmental friendliness. Due to its multifunctional structure, castor oil is an excellent precursor in the synthesis of new biolubricants. However, it showed poor thermal‐oxidative stability and a higher pour point. This study used castor oil fatty acids prepared by transesterification (EHRO), epoxidation (TEPO), and oxirane ring opening with the aromatic amines aniline (ANIL) andp‐anisidine (ANIS). The chemical structure of these oils was verified by1H and13C NMR analysis, and mass spectrometry. Measurements show that the presence of an aromatic amine increases the viscosity resulting in 172 (ANIL) and 199 (ANIS) cSt at 40°C, but reduces viscosity index to 16 and 1, respectively. In addition, the amine groups can scavenge radicals increasing their thermal and oxidative stability. These products do not oxidize copper, and tribological analysis reveals that ANIS has the lowest torque with wear equivalent to commercial mineral lubricant NH‐140.