Stabilization of reactive intermediates is an enabling concept in biomass fractionation and depolymerization. Deep eutectic solvents (DES) are intriguing green reaction media for biomass processing; however undesired lignin condensation is a typical drawback for most acid-based DES fractionation processes. Here we describe ternary DES systems composed of choline chloride and oxalic acid, additionally incorporating ethylene glycol (or other diols) that provide the desired ‘stabilization’ function for efficient lignocellulose fractionation, preserving the quality of all lignocellulose constituents. The obtained ethylene-glycol protected lignin displays high β-O-4 content (up to 53 per 100 aromatic units) and can be readily depolymerized to distinct monophenolic products. The cellulose residues, free from condensed lignin particles, deliver up to 95.9 ± 2.12% glucose yield upon enzymatic digestion. The DES can be recovered with high yield and purity and re-used with good efficiency. Notably, we have shown that the reactivity of the β-O-4 linkage in model compounds can be steered towards either cleavage or stabilization, depending on DES composition, demonstrating the advantage of the modular DES composition.

Green amine synthesis is assessed using the CHEM21 green metrics toolkit, offering a step-by-step guide for sustainability evaluation and promoting environmentally conscious transformations.

New chiral heteroleptic germanium(II) and tin(II) metallylenes were obtained using 1-(para-tolylsulfinyl)-3-tosyl-5-tert-butyl-benzene as a non-symmetric O,C,O-chelating pincer ligand. Crystallographic analysis and DFT calculations indicate that the non-symmetric sulfinyl–sulfonyl pincer ligand acts as an O,C,O-coordinating pincer-type-ligand with predominant sulfinyl intramolecular SO coordination to germanium(II) and tin(II) centers.

Background: This research centers on the development and spectroscopic characterization of new quinazolin-4(3H)-one-isoxazole derivatives (5a–e). The aim was to investigate the regioselectivity of the 1,3-dipolar cycloaddition involving arylnitriloxides and N-propargylquinazolin-4(3H)-one, and to assess the antioxidant properties of the synthesized compounds. The synthetic approach started with the alkylation of quinazolin-4(3H)-one using propargyl bromide, followed by a 1,3-dipolar cycloaddition reaction. Methods: The structural identification of the products was performed using various spectroscopic methods, such as IR, 1H, 13C, and HMBC NMR, HRMS, and single-crystal X-ray diffraction. To further examine the regioselectivity of the cycloaddition, Density Functional Theory (DFT) calculations at the B3LYP/6-31G(d) level were employed. Additionally, the antioxidant potential of the compounds was tested in vitro using DPPH (2,2-Diphenyl-1-picrylhydrazyl)radical scavenging assays. The reaction selectively produced 3,5-disubstituted isoxazoles, with the regiochemical outcome being independent of the substituents on the phenyl ring. Results: Theoretical calculations using DFT were in agreement with the experimental results, revealing activation energies of −81.15 kcal/mol for P-1 and −77.32 kcal/mol for P-2, favoring the formation of P-1. An analysis of the Intrinsic Reaction Coordinate (IRC) confirmed that the reaction proceeded via a concerted but asynchronous mechanism. The antioxidant tests demonstrated that the synthesized compounds exhibited significant radical scavenging activity, as shown in the DPPH assay. The 1,3-dipolar cycloaddition of arylnitriloxides with N-propargylquinazolin-4(3H)-one successfully resulted in novel 3,5-disubstituted isoxazoles. Conclusions: The experimental findings were well-supported by theoretical predictions, and the antioxidant assays revealed strong activity, indicating the potential for future biological applications of these compounds.