Glycolaldehyde Dimer Research Articles

Stereo‐ and Chemoselective Enrichment of sp3 Character in Post‐Ugi Morpholines

We conducted a systematic study on synthesis and modification of morpholine core using Ugi adducts derived from propiolic acid and glycolaldehyde dimer. The assembly step involved triphenylphosphine‐promoted 6‐exo‐dig umpolung oxa‐Michael cyclization of Ugi‐derived hydroxypropargylamides yielding 2‐methylenemorpholin‐3‐one derivatives. Subsequent heterogeneous catalytic hydrogenation of the exocyclic double bond proceeded in a highly diastereoselective fashion establishing a relative cis configuration in the resulting sp3‐enriched morpholinone scaffold. Finally, chemoselective amide reduction with lithium aluminum hydride (LAH) allowed to obtain fully saturated morpholines while leaving the more sterically hindered exocyclic amide moiety intact. Taken together these findings outline the strategy for controlled reduction of the inherent rigidity of post‐Ugi scaffolds.

Electrochemical Decomposition of Ethylene Glycol-Choline Chloride Deep Eutectic Solvent

Deep eutectic solvents (DES) are a form of ionic liquid that can offer a larger electrochemical window than water while remaining relatively conductive as compared to other non-aqueous options. DES are made from the eutectic combination of a variety of hydrogen bond donors and acceptors. At a molar ratio of donor and acceptor specific to each DES, the melting point of the mixture is significantly depressed resulting in a room temperature liquid with a high boiling point. As a result, they are considerably less volatile and therefore a safer alternative to traditional organic solvents such as acetonitrile. The low vapor pressure associated with a deep eutectic composition allows for operation at elevated temperatures for faster kinetics, increased conductivity and lower viscosity. DES can also contain a greater concentration of supporting charge carries than many organic solvents (up to 8 M) and many redox active organic compounds are also highly soluble in DES. These factors make DES a promising electrolyte for redox flow batteries, with the potential for higher energy densities than can be achieved in aqueous electrolytes.One of the most commonly studied DES is a 1:2 molar ratio mixture of choline chloride and ethylene glycol respectively. This mixture, commonly called ‘ethaline’ is one of the most conductive, lowest viscosity DES. While these are desirable characteristics, the stable electrochemical window is only ≈2 V which is only somewhat larger than the usable window of an alkaline aqueous electrolyte. The objective of this effort is to investigate the electrochemical decomposition of ethaline at the anodic and cathodic limits.Relatively little literature exists on the decomposition of ethaline. It has been claimed that at the anode, several different chlorinated organics are created by various mechanisms and that hydrogen is evolved at the cathode from water contained in the electrolyte.1 While the oxidation of ethylene glycol (EG) is well studied2 , 3, the oxidation of ethaline and the reduction of EG and ethaline both are somewhat unknown. A series of electrolysis experiments using a divided cell were carried out using dry ethaline prepared in a glove box with a water vapor content below 5 ppm. The water content in the electrolyte was determined by Karl Fischer titration to be less than 300 ppm. The products of these experiments were analyzed using mass spectroscopy (of both the anodic and cathodic electrolytes and of the headspace above each) and FTIR. These results show that the positive decomposition involves the oxidation of ethylene glycol to glycolaldehyde, and subsequent formation of the glycolaldehyde dimer in solution. At the negative limit, hydrogen is evolved in direct proportion to the current passed. However, it can be conclusively shown that the reduction current can exceed the maximum possible current due to the reduction of water, implying that the reduction of the DES components is necessary. GC-MS analysis of the negative electrolyte showed the presence of higher molecular weight fragments consistent with the reaction scheme shown in Fig 1 below. In this scheme, the reduction of ethylene glycol results in the generation of H2 gas as observed, and the formation of ethylene oxide. The ethylene oxide produced then can react chemically with ethylene glycol to yield dimers and trimers of polyethylene glycol whose molecular masses are consistent with the peaks observed in the GC-MS analysis.The identification of these breakdown pathways will provide insight into safety concerns related to overcharge of ethaline electrolytes and will allow for the development of alternative formulations that can extend the potential limits to allow for the incorporation of higher voltage redox couples in redox flow batteries based on DES electrolytes.

Molecular characteristics of volatile components from willow bark

Willow (Salix matsudana) bark is the bark of willow trees, it is rich in resources. Extracting these resources becomes difficult due to the relative lack of systematic and in-depth analysis of the total chemical composition. Analysis was performed using TDS-GC/MS, TG, FTIR and PY-GC/MS techniques. Results and discussion: the extracts form volatile organic compounds are mainly included in the analysis of TDS-GC/MS, such as, organic acids, exters, alcohols, etc. Extracts are rich in VOCs:1,2-Benzenedicarboxylic acid, bis(2-methylpropyl) ester, its function is mainly as plasticizer. FTIR analysis are further confirmed, the ingredients of total extracts include ethers, The treatment of total heat loss is divided into two distinct phases: the first phase of 50 °C to 100 °C, the second phase of 150 °C to 250 °C, the sequence of quality loss is the second and the first stage, important turning point temperature is 245 °C, with significant changes in quality, for example, high polymer pyrolysis into small volatile molecules. In addition, various pyrolysis VOCs have been analyzed by PY-GC/MS, And have good development space, such as, Carbamic acid, monoammonium salt (4.80%), Glycolaldehyde dimer (4.04%), Catechol (0.44%). etc. Both of them have good development prospects, including many new chemical components produced by the pyrolysis of total extracts and residues, which is a new method to provide high quality applications.

Structural Characterization of β-Glycolaldehyde Dimer

Structural characterization of the β-polymorph of glycolaldehyde dimer by powder X-ray diffraction, Raman and infrared spectroscopies is described. The previously described α-polymorph and the β-polymorph both crystallize in the monoclinic crystal system, space group P21/c, but with different cell parameters. There are no significant differences in the glycolaldehyde dimer molecular structure, the molecules in both polymorphs are trans-isomers with the hydroxyl groups in axial positions. The two polymorphs have a different arrangement of the glycolaldehyde dimer molecules. In the previously reported α-polymorph the molecules are arranged in hydrogen bonded layers parallel to (100) while in the β-polymorph the hydrogen bonded molecules are arranged in a three-dimensional network. Theoretically calculated Gibbs free energy as well as differential scanning calorimetry indicate β-polymorph to be the stable crystal phase of glycolaldehyde.

A family AA5_2 carbohydrate oxidase from Penicillium rubens displays functional overlap across the AA5 family.

Copper radical alcohol oxidases belonging to auxiliary activity family 5, subfamily 2 (AA5_2) catalyze the oxidation of galactose and galactosides, as well as aliphatic alcohols. Despite their broad applied potential, so far very few AA5_2 members have been biochemically characterized. We report the recombinant production and biochemical characterization of an AA5_2 oxidase from Penicillium rubens Wisconsin 54–1255 (PruAA5_2A), which groups within an unmapped clade phylogenetically distant from those comprising AA5_2 members characterized to date. PruAA5_2 preferentially oxidized raffinose over galactose; however, its catalytic efficiency was 6.5 times higher on glycolaldehyde dimer compared to raffinose. Deep sequence analysis of characterized AA5_2 members highlighted amino acid pairs correlated to substrate range and conserved within the family. Moreover, PruAA5_2 activity spans substrate preferences previously reported for AA5 subfamily 1 and 2 members, identifying possible functional overlap across the AA5 family.

α-Unsubstituted Pyrroles by NHC-Catalyzed Three-Component Coupling: Direct Synthesis of a Versatile Atorvastatin Derivative.

A practical one-pot cascade reaction protocol provides direct access to valuable 1,2,4-trisubstituted pyrroles. The process involves an N-heterocyclic carbene (NHC)-catalyzed Stetter-type hydroformylation using glycolaldehyde dimer as a novel C1 building-block, followed by a Paal-Knorr condensation with primary amines. The reaction makes use of simple and commercially available starting-materials and catalyst, an important feature regarding applicability and utility. Low catalyst loading under mild reaction conditions afforded a variety of 1,2,4-substituted pyrroles in a transition-metal-free reaction with high step economy and good yields. This methodology is applied in the synthesis of a versatile Atorvastatin precursor, in which a variety of modifications at the pyrrole core structure are possible.

ChemInform Abstract: A Concise One‐Pot Organo‐ and Biocatalyzed Preparation of Enantiopure Hexahydrofuro[2,3‐b]furan‐3‐ol: An Approach to the Synthesis of HIV Protease Inhibitors.

AbstractThe one‐pot synthesis of the title species (IV) involves condensation of dihydrofuran with glycolaldehyde dimer (II) followed by lipase‐catalyzed kinetic resolution.

ChemInform Abstract: One‐Step Protecting‐Group‐Free Synthesis of Azepinomycin in Water.

AbstractA direct synthesis of the title compound (III) is achieved by the uncatalyzed reaction of 5‐aminoimidazole‐4‐carboxamide (I) with glycolaldehyde dimer in buffered aqueous solution.

New strategy for the synthesis of proaporphine and homoproaporphine-type alkaloids from a common intermediate

Starting with 3-bromo-4,5-dimethoxybenzaldehyde 14, it was coupled with the boronic anhydride 15 using standard Suzuki reaction conditions to give 16 (91%). The aldehyde 16 was exposed to classical nitro-aldol reaction conditions to give 17 (88%), and conjugatively reduced with DIBAL-H to give 18 (91%). Protection of the amine 18 as its N-carbamate derivative 19, followed by condensation with glycol aldehyde dimer under acidic reaction conditions gave 20 (78%). Subsequent conversion of 20 into its mesylate derivative 21, and exposure to CsF under aprotic reaction conditions gave 22 (81%). Deprotection of 22 gave (±)-stepharine 10 in 29% overall yield though 8 steps. A similar sequence of reaction conditions converted the amine 18 into the -NTs protected homoproaporphine adduct 28.

Catalytic Cracking of C2–C3 Carbonyls with Vacuum Gas Oil

The fluid catalytic cracking (FCC) route could be considered for the co-processing of biomass-derived pyrolysis oil with petroleum-derived vacuum gas oil (VGO) in a typical refinery unit by integrating it with a biomass fast pyrolysis process. This paper aims to study the effect of co-processing pyrolysis oil representative model compounds (C2–C3 carbonyls such as hydroxyacetone and glycolaldehyde dimer) with VGO in a FCC advanced cracking evaluation (ACE-R) unit, using an industrially available FCC equilibrium catalyst (E-CAT). The blending ratios of C2–C3 carbonyls and VGO were varied from 5:95, 10:90, 15:85, and 20:80. The reactor was operated in close to industrial FCC process at a temperature of 530 °C and atmospheric pressure with a catalyst-to-oil ratio of 5.0. The blended FCC feedstock and their liquid distillates were structurally characterized by 1H and gated decoupled 13C NMR techniques. The average structural parameters like branchiness index, substitution index, average length of alkyl chains, and fraction of aromaticity per molecule was obtained from NMR data. A linear increase in FCC conversion was observed with increase in hydroxyacetone blending ratio with VGO from 5% to 20%, which may be due to an increase in propylene and a decrease in heavy cycle oil. Increasing the glycolaldehyde blending ratio from 5% to 10% increased the FCC conversion, while the conversion decreased at ratios of 15% and 20%. The 1H NMR and 13C NMR data indicated that there is an increase in the amount of monoaromatics with increases in the amount of hydroxyacetone, whereas in the case of glycolaldehyde, the monoaromatics increased for blending ratios up to 10% and decreased upon further increases in blending ratio. The equilibrium FCC catalyst is capable of cracking oxygenates presents in pyrolysis oil such as hydroxyacetone and glycolaldehyde toward the production of liquefied petroleum gas (LPG) range products. Furthermore, a scheme has been proposed for the processing of pyrolysis oil in petroleum refinery units.

Glycolaldehyde dimer in the stable crystal phase has axial OH groups: Raman, infrared and X-ray data analysis

Although a small molecule and a simple 1,4-dioxane derivative, 2,5-dihydroxy-1,4-dioxane or glycolaldehyde dimer has a crystal structure that has eluded researchers so far, chief reason lying presumably in substance polymorphism. Here we report for the first time on the stable crystal structure of the glycolaldehyde dimer characterized by the X-ray powder diffraction method at room temperature. It crystallizes in the monoclinic system, space group P21/c, with unit cell parameters a=5.9473(1)Å, b=8.3997(1)Å, c=5.61953(8)Å and β=114.8814(9)°. The glycolaldehyde dimer molecules are the trans-isomers with the electronegative hydroxyl groups in axial positions and molecules are arranged in hydrogen bonded layers parallel to (100). Each layer is stabilized by intermolecular medium strong O–H⋯O hydrogen bonds. The 1,4-dioxane ring of the molecule adopts a chair conformation.Raman and infrared spectra were re-examined and assigned with the help of ab initio calculation followed by a normal modes analysis modes most sensitive to crystal packing were identified as the C–OH deformations which were assigned to the IR and Raman bands at 1239 and 1237cm−1, respectively; the two O–C–O deformation modes, both associated with the Raman and IR bands at 561 and 535cm−1 and, the two OH torsion modes assigned to the IR bands at 630 and 604cm−1.

Hydrochar and Biochar Effects on Germination of Spring Barley

AbstractWithin the framework of climate change mitigation by sequestrating recalcitrant carbon in soil, biochar is considered as a promising soil amendment. Testing any such soil additives is vitally important, as they should not cause abiotic stress for plants due to chemical constituents they may contain. Thus, germination tests with spring barley (Hordeum vulgare) were conducted to assess phytotoxic effects of biochar, hydrochar and process‐water from hydrothermal carbonization (HTC) as soil amendments. Additionally, single‐component tests with substances found in process‐waters were carried out with cress (Lepidium sativum). While biochars generally had no effect on germination, hydrochars and process‐waters significantly inhibited germination. The dissolved organic carbon content predicted the germination‐inhibiting effects observed. Three compounds resulted in partial (guaiacol) or total (levulinic acid and glycolic acid) inhibition of cress seed germination, and three others (acetic acid, glycolaldehyde dimer and catechol) had a negative impact on growth. Phytotoxic substances in chars appeared to be mostly water soluble and volatile. Pre‐treatments of hydrochars and process‐waters (i.e. storage and washing) were able to reduce germination inhibition. While phytotoxic substances that are generated during HTC stay in the products, biochars from kiln carbonization of the same feedstocks had no negative effects on germination, likely because volatiles evaporate during the conversion. Our study highlights the importance of comprehensively testing carbonized products for their compatibility with agricultural and horticultural systems.

Synthesis of Passerini−Ugi Hybrids by a Four-Component Reaction Using the Glycolaldehyde Dimer

Passerini-Ugi hybrid adducts can be obtained through a four-component reaction by using glycolaldehyde dimer.

Spectroscopic arguments for a new crystal phase of glycolaldehyde

AbstractIn an attempt to elucidate the nature of glycolaldehyde dimer solid phases further, low‐temperature Raman spectroscopy was employed and phonon spectra were recorded in the temperature in range 10–300 K. It seems probable that the α phase of glycolaldehyde dimer belongs to the P21/n space group with Z = 2, the same crystal class in which 1,4‐dioxane and DL‐glyceraldehyde crystallize. Studying the temperature dependence of the low‐wavenumber Raman bands of glycolaldehyde dimer α phase, one observes an increase in the number of phonons from six to 13 when the sample is cooled below 80 K. We suggest that a phase transformation into a new phase γ takes place, with the number of molecules per unit cell probably equal to Z = 4. Normal coordinate analysis was performed for glycolaldehyde dimer with two equatorial and with two axial hydroxyl groups, in order to predict the number of internal modes falling in the phonon region. If there were any centrosymmetric dimers with two axial hydroxyl groups present, than a band around 150 cm−1 would have been expected in the Raman spectrum, which was not observed. This is by far the strongest argument in favour of the hypothesis that the α phase consists of dimers with two equatorially placed hydroxyl groups. Copyright © 2005 John Wiley & Sons, Ltd.

The in situ Oxidation—Wittig Reaction of α‐Hydroxyketones.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The in situ oxidation-Wittig reaction of alpha-hydroxyketones.

In situ oxidation-Wittig methodology has been applied to alpha-hydroxyketones avoiding the problems normally associated with alpha-ketoaldehydes; the procedure is practically simple, and in many cases gives high yields of the product gamma-ketocrotonates; the procedure has also been successfully utilised with ethyl glycolate and glycolaldehyde dimer.

An Efficient Synthesis of Morpholin-2-one Derivatives Using Glycolaldehyde Dimer by the Ugi Multicomponent Reaction

A new one-pot procedure for the efficient synthesis of novel 3-substituted morpholin-2-one-5-carboxamide derivatives using commercially available glycolaldehyde dimer as a bifunctional component with various alpha-amino acids and isocyanides by the Ugi five-center three-component reaction (U-5C-3CR) was developed. [reaction: see text]

Kinetics of equilibrium attainment between molecular glycolaldehyde structures in an aqueous solution

The kinetics of the isomerization and monomerization of the glycolaldehyde dimer in a D2O solution (pD = 4.3) at 25°C is studied by1H NMR spectroscopy (360 MHz). The dynamics of the concentrations of seven dimeric and two monomeric glycolaldehyde forms present in the solution is examined when the system attains equilibrium. A kinetic scheme of equilibrium attainment in an aqueous solution of glycolaldehyde is proposed. The apparent rate constants of the transformation of the molecular glycolaldehyde structures into each other are determined

Investigation of the mechanism of dissociation of glycolaldehyde dimer (2,5-dihydroxy-1,4-dioxane) by FTIR spectroscopy

Glycolaldehyde represents the simplest α-hydroxycarbonyl moiety–a common structural feature of reducing sugars. It exists in solid state, only in crystalline dimeric form as 2,5-dihydroxy-1,4-dioxane. However, in solution phase or during heating, it dissociates into different dimeric and monomeric forms. FTIR spectroscopy was used to study the effect of temperature, pH and solvent on the dissociation and chemical transformations of glycolaldehyde. The infrared spectra were recorded in different solvents as a function of time and temperature (both during heating and cooling cycles) between 30 and 85 °C. During heating, glycolaldehyde cyclic dimer generated two bands in the carbonyl region, one at 1744 cm −1 and the other at 1728 cm −1. These bands increased during the heating cycle and decreased during the cooling cycle. The data indicated that the glycolaldehyde cyclic dimer (2,5-dihydroxy-1,4-dioxane) undergoes a ring opening to form the acyclic dimer (1728 cm −1) that can recyclize into the 2-hydroxymethyl-4-hydroxy-1,3-dioxolane structure. The acyclic dimer can also dissociate into monomeric glycoladehyde (1744 cm −1) in equilibrium with the enediol form (1703 cm −1). There is evidence to indicate oxidation of glycolaldehyde into glycolic acid during heating, in either neutral or basic aqueous solutions.