Glyoxal Derivatives Research Articles

Organophotoredox-Catalyzed Synthesis of Unnatural α/β Amino Acids and Peptides via Deaminative Three-Component Coupling.

Herein, we disclose an expedient visible-light-mediated, organophotoredox-catalyzed multicomponent synthesis of unnatural amino acids using a Katritzky salt, glyoxal derivatives, and substituted anilines. Mechanistically, an alkyl radical is generated from the Katritzky salt via a deaminative process that undergoes addition to the in situ-generated imine to furnish α-amino acids in a moderate diastereoisomeric ratio. For the first time, we have demonstrated this deaminative protocol to access substituted β-amino acids from α-amino acid-derived Katritzky salts. Furthermore, α-amino amides are also generated from the corresponding 2-oxoacetamide derivatives.

A Catalyst‐ and Metal‐free Approach towards the Synthesis of β‐Carboline tethered Imidazole Derivatives and Assessment of their Photophysical Properties

AbstractA simple, facile, and highly efficient approach has been unfolded for the syntheses of β‐carboline tethered imidazole derivatives. This expeditious catalyst‐free strategy proceeds through the assembly of 1‐formyl‐9H‐β‐carbolines, glyoxal derivatives and ammonium acetate via the formation of concomitant four C−N bonds in a one‐pot operation. The current approach has various advantages, including multicomponent nature, simple reaction conditions, short reaction time, broad substrate scope, and high product yield. Importantly, the β‐carboline tethered imidazole derivatives displayed excellent photophysical properties with quantum yield up to 90%.

Distinctive Mechanistic Scenarios and Substituent Effects of Gold(I) versus Copper(I) Catalysis for Hydroacylation of Terminal Alkynes with Glyoxal Derivatives.

Density functional theory (DFT) calculations have been conducted to study the mechanisms, substituent effects, and the role of bases in Au- and Cu-catalyzed hydroacylation of terminal alkyne with glyoxal derivatives. The two reactions, despite being catalyzed by the same group of transition metals, follow distinctive reaction mechanisms. Through the detailed DFT calculations, insights into the mechanisms are obtained, and the substituent effects and the role of the bases are understood.

Catalytic Asymmetric Darzens‐Type Epoxidation of Diazoesters: Highly Enantioselective Synthesis of Trisubstituted Epoxides

AbstractHighly enantioselective Darzens‐type epoxidation of diazoesters with glyoxal derivatives was accomplished using a chiral boron–Lewis acid catalyst, which facilitated asymmetric synthesis of trisubstituted α,β‐epoxy esters. In the presence of a chiral oxazaborolidinium ion catalyst, the reaction proceeded in high yield (up to 99 %) with excellent enantio‐ and diastereoselectivity (up to >99 % ee and >20:1 dr, respectively). The synthetic potential of this method was illustrated by conversion of the products to various compounds such as epoxy γ‐butyrolactone, tertiary β‐hydroxy ketone and epoxy diester.

Catalytic Asymmetric Darzens-Type Epoxidation of Diazoesters: Highly Enantioselective Synthesis of Trisubstituted Epoxides.

Highly enantioselective Darzens-type epoxidation of diazoesters with glyoxal derivatives was accomplished using a chiral boron-Lewis acid catalyst, which facilitated asymmetric synthesis of trisubstituted α,β-epoxy esters. In the presence of a chiral oxazaborolidinium ion catalyst, the reaction proceeded in high yield (up to 99 %) with excellent enantio- and diastereoselectivity (up to >99 % ee and >20:1 dr, respectively). The synthetic potential of this method was illustrated by conversion of the products to various compounds such as epoxy γ-butyrolactone, tertiary β-hydroxy ketone and epoxy diester.

Synthesis of Glyoxal Derivatives in Continuous Flow

Synthesis of Glyoxal Derivatives in Continuous Flow

Continuous flow as an enabling technology: a fast and versatile entry to functionalized glyoxal derivatives

We herein report two complementary strategies employing organolithium chemistry for the synthesis of glyoxal derivatives. Micro-mixer technology allows for the generation of unstable organometallic intermediates and their instantaneous in-line quenching with esters as electrophiles. Selective mono-addition was observed via putative stabilized tetrahedral intermediates. Advantages offered by flow chemistry technologies facilitate direct and efficient access to masked 1,2-dicarbonyl compounds while mitigating undesired by-product formation. These two approaches enable the production of advanced and valuable synthetic building blocks for heterocyclic chemistry with throughputs of grams per minute.

Glyoxal and its derivatives for stabilization of aluminium silicate colloid-dispersed systems

Preliminary studies have shown the possibility of using organic-mineral additive based on glyoxal and saponite containing waste for injection strengthening of soils. Modification of the sandy soil with the organic-mineral additive increases its specific cohesion up to 50 times. However, the resulting periodic colloidal structure (PCS) is not resistant to external temperature and humidity effects. The research aim was to evaluate the possibility of obtaining glyoxal derivatives by its chemical interaction with bark lignin substances without their preliminary extraction and test these structures for stabilization of the aluminium silicate colloid-dispersed systems. To activate surface centers of lignin, the bark was ground to the average particle size of 3.2 μm. Identification of IR spectra showed that the characteristic bands for lignin-glyoxal and bark-glyoxal compositions coincide practically and differ significantly from the spectrum of lignin in the range of 500-1500 cm−1. It can confirm the formation of interaction products of bark lignin substances with glyoxal. Before the effect of moisture compressive strength of sandy soil samples with an organic-mineral additive based on glyoxal (reference sample) and its derivatives (test sample) is almost the same and at an average of 6 MPa. However, after moisture saturation the reference sample strength is reduced by 50 times, and the test sample strength is decreased by only 4 times. It confirms the formation of a stable PCS.

Construction of Distant Stereocenters by Enantioselective Desymmetrizing Carbonyl-Ene Reaction.

An efficient desymmetrizing carbonyl-ene reaction of 1-substituted 4-methylenecyclohexanes with glyoxal derivatives was thus executed by a chiral N,N'-dioxide/NiII catalyst, providing facile access to cyclohexene derivatives bearing two remote 1,6-related stereocenters. This distal stereocontrol methodology originates from the efficient interaction between the catalyst with enophiles, discrimination of the two chair conformations of olefinic components, and the intrinsic six-membered transition-state structure of ene process.

ChemInform Abstract: Synthesis of 1,2‐Dicarbonyl‐3‐enes by Hydroacylation of 1‐Alkynes with Glyoxal Derivatives Using Metal—Organic Framework Cu/MOF‐74 as Heterogeneous Catalyst.

A crystalline copper-based metal-organic framework Cu/MOF-74 was synthesized, and used as an efficient heterogeneous catalyst for the synthesis of 1,2-dicarbonyl-3-enes by means of the hydroacylation of 1-alkynes with glyoxal derivatives in the presence of a base. Cu/MOF-74 was found to be more catalytically active for the synthesis of 1,2-dicarbonyl-3-enes than other MOFs including Cu2 (BDC)2 (DABCO), Cu3 (BTC)2 , Cu(BDC), Cu2 (NDC)2 (DABCO), Cu4 I4 (DABCO)2 , Ni-MOF-74, Zn-MOF-74, Fe3 O(BDC)3 , In(OH)(BDC), and Zr6 O4 (OH)4 (BDC)6 . Cu/MOF-74 also exhibited better performance than other homogeneous copper catalysts, including Cu(OAc)2 , Cu(NO3 )2 , CuI, CuBr, CuCl, CuCl2 , and CuBr2 . The Cu/MOF catalyst was able to be recovered and reused several times without a significant degradation in catalytic activity. To the best of our knowledge, the formation of 1,2-dicarbonyl-3-enes has not previously been carried out under heterogeneous catalysis conditions.

HOCCO versus OCCO: Comparative spectroscopy of the radical and diradical reactive intermediates.

We present a photoelectron imaging study of three glyoxal derivatives: the ethylenedione anion (OCCO(-)), ethynediolide (HOCCO(-)), and glyoxalide (OHCCO(-)). These anions provide access to the corresponding neutral reactive intermediates: the OCCO diradical and the HOCCO and OHCCO radicals. Contrasting the straightforward deprotonation pathway in the reaction of O(-) with glyoxal (OHCCHO), which is expected to yield glyoxalide (OHCCO(-)), OHCCO(-) is shown to be a minor product, with HOCCO(-) being the dominant observed isomer of the m/z = 57 anion. In the HOCCO/OHCCO anion photoelectron spectrum, we identify several electronic states of this radical system and determine the adiabatic electron affinity of HOCCO as 1.763(6) eV. This result is compared to the corresponding 1.936(8) eV value for ethylenedione (OCCO), reported in our recent study of this transient diradical [A. R. Dixon, T. Xue, and A. Sanov, Angew. Chem., Int. Ed. 54, 8764-8767 (2015)]. Based on the comparison of the HOCCO(-)/OHCCO(-) and OCCO(-) photoelectron spectra, we discuss the contrasting effects of the hydrogen connected to the carbon framework or the terminal oxygen in OCCO.

Synthesis of 1,2-Dicarbonyl-3-enes by Hydroacylation of 1-Alkynes with Glyoxal Derivatives Using Metal-Organic Framework Cu/MOF-74 as Heterogeneous Catalyst.

A crystalline copper-based metal-organic framework Cu/MOF-74 was synthesized, and used as an efficient heterogeneous catalyst for the synthesis of 1,2-dicarbonyl-3-enes by means of the hydroacylation of 1-alkynes with glyoxal derivatives in the presence of a base. Cu/MOF-74 was found to be more catalytically active for the synthesis of 1,2-dicarbonyl-3-enes than other MOFs including Cu2 (BDC)2 (DABCO), Cu3 (BTC)2 , Cu(BDC), Cu2 (NDC)2 (DABCO), Cu4 I4 (DABCO)2 , Ni-MOF-74, Zn-MOF-74, Fe3 O(BDC)3 , In(OH)(BDC), and Zr6 O4 (OH)4 (BDC)6 . Cu/MOF-74 also exhibited better performance than other homogeneous copper catalysts, including Cu(OAc)2 , Cu(NO3 )2 , CuI, CuBr, CuCl, CuCl2 , and CuBr2 . The Cu/MOF catalyst was able to be recovered and reused several times without a significant degradation in catalytic activity. To the best of our knowledge, the formation of 1,2-dicarbonyl-3-enes has not previously been carried out under heterogeneous catalysis conditions.

Probing the Limits of Tetraazamacrocycle‐Glyoxal Condensates as Bidentate Ligands for Cu2+

AbstractTetracyclic bisaminals formed by condensation of tetraazamacrocycles and glyoxal have rarely been utilized as ligands for transition metal ions. Five novel Cu2+ complexes are presented to expand this set. Glyoxal derivatives of pyruvic aldehyde and butanedione were expected to further rigidify the bisaminal skeleton because of the steric requirements of the methyl groups, while the previously unutilized homocyclam was expected to increase flexibility due to the presence of a seven‐membered ring. Additionally, a nitrato complex was prepared to examine the effect of more bulky monodentate ligands on the bisaminal framework. The new complexes showed similar four‐coordination of Cu2+, but with significant changes in coordination geometry caused by substitution of the glyoxal bridge by one or two methyl groups. The homocyclam derivative produced a completely different coordination mode due to the flexibility of the larger macrocycle ring. Both structural and electronic properties were affected by the use of nitrato in place of the typical chlorido monodentate ligands. Overall, the electronic properties (magnetic moment, electronic spectra, and cyclic voltammetry) were only subtly affected. However, larger changes were observed when the larger homocyclam macrocycle was used or the nitrato anion was used in place of the chlorido ligand to complete the coordination. Additionally, the recently published geometric index τδ was evaluated by using this series of closely related Cu2+ complexes.

Immobilization and stabilization of an endoxylanase from Bacillus subtilis (XynA) for xylooligosaccharides (XOs) production

Xylooligosaccharides (XOs) are small oligomers constituted by 2−10 units of xylan monomers, with important nutraceutical properties. They can be produced through hydrolysis of xylan catalyzed by an endoxylanase. The use of immobilized and stabilized enzymes may decrease the industrial process costs. In this study, XynA, a recombinant enzyme from B. subtilis, was immobilized in three different supports: agarose and chitosan activated with glyoxal groups and chitosan activated with glutaraldehyde. High immobilization yields were obtained, 100% for agarose-glyoxal and chitosan-glutaraldehyde, 82% for chitosan-glyoxal, with recovered activities of 42.7 (±1.3), 10.7±0.8 and 53.6% (± 1.7), respectively. A great increase in the thermal stability of the enzyme (at 56°C, pH 5.5) was achieved for the glyoxal derivatives: 75-fold for chitosan and 8600-fold for agarose. The great thermal stability obtained to the derivative agarose-glyoxal can be explained by the enzyme immobilization through lysine residues located in unstable sites of the protein structure. The agarose-glyoxal derivative was tested in the production of XOs (X2, X3 and X4) from soluble and conventional birchwood xylan, reaching approximately 20% of conversion in 3h and 23% in 24h, without the undesirable xylose production. After 10 cycles of hydrolysis, the conversion remained almost unchanged.

ChemInform Abstract: Ultrasound‐Mediated One‐Pot Synthesis of 7‐Methyl‐Substituted Pyrido[4,3‐d]pyrimidine Scaffolds by a Catalyst‐Free Protocol.

AbstractThe reaction succeeds using aryl aldehydes as the reaction partner, but fails with alkyl aldehydes and phenyl glyoxal derivatives.

Straightforward and mild deprotection methods of N-mono- and N1,N7-functionalised bisaminal cyclens

Strategic removal of the bisaminal bridge of N-mono- and N1,N7-difunctionalised cyclen glyoxal derivatives was carried out via transamination processes with vicinal diamines. These procedures were found to be particularly well-suited for cyclen targets bearing sensitive groups.

ChemInform Abstract: CuBr‐Promoted Formal Hydroacylation of 1‐Alkynes with Glyoxal Derivatives: An Unexpected Synthesis of 1,2‐Dicarbonyl‐3‐enes.

AbstractThis novel reaction proceeds with absolute E‐selectivity.

CuBr-promoted formal hydroacylation of 1-alkynes with glyoxal derivatives: an unexpected synthesis of 1,2-dicarbonyl-3-enes.

An efficient and concise protocol has been developed for the highly regio- and stereoselective synthesis of E-1,2-dicarbonyl-3-ene derivatives by a copper-promoted reaction of 1-alkynes with α-carbonyl aldehydes in the presence of morpholine. The products obtained are believed as the formal hydroacylation of the triple bond.

Catalytic hetero-ene reactions of 5-methyleneoxazolines: highly enantioselective synthesis of 2,5-disubstituted oxazole derivatives.

An efficient catalytic asymmetric hetero-ene reaction of 5-methyleneoxazolines with 1,2-dicarbonyl compounds (including α-ketoesters and glyoxal derivatives) was realized using Ni(II)-N,N'-dioxide complexes as the catalysts. It provides a rapid, high yielding (up to 99%) route for the preparation of 2,5-disubstituted oxazole derivatives in a highly enantioenriched form (up to >99% ee) under mild conditions.

Slow delivery of a nitrification inhibitor (dicyandiamide) to soil using a biodegradable hydrogel of chitosan

Using chemical inhibitors to reduce soil nitrification decreases emissions of environmental damaging nitrate and nitrous oxide and improves nitrogen use efficiency in agricultural systems. The efficacy of nitrification inhibitors such as dicyandiamide (DCD) is limited in soil due to biodegradation. This study investigated if the persistence of DCD could be sustained in soil by slow release from a chitosan hydrogel. DCD was encapsulated in glyoxal-crosslinked chitosan beads where excess glyoxal was (i) partly removed (C beads) or (ii) allowed to dry (CG beads). The beads were tested in water and in soil. The beads contained two fractions of DCD: one which was quickly released in water, and one which was not. A large DCD fraction within C beads was readily available: 84% of total DCD bead content was released after 9h immersion in water, while between 74% and 98% was released after 7d in soil under low to high moisture conditions. A lower percentage of encapsulated DCD was readily released from CG beads: 19% after 9h in water, and 33% after 7d in soil under high rainfall conditions. Kinetic analysis indicated that the release in water occurred by quasi-Fickian diffusion. The results also suggest that DCD release was controlled by bead erosion and the leaching of glyoxal derivatives, predominantly a glyoxal-DCD adduct whose release was positively correlated with that of DCD (R2=0.99, p⩽0.0001). Therefore, novel chitosan/glyoxal composite beads show a promising slow-release potential in soil for agrochemicals like DCD.