Ewoud

An organo-photocatalyzed approach for the chemoselective dealkylation and de-esterification of phenols is developed by employing trimethyl silyl chloride as the C‒O bond activator and 9-Mes-10-MeAcr+ClO4‒ as the photoredox catalyst. This method demonstrates an exceptional selectivity towards the cleavage of phenolic ethers and esters over equivalent aliphatic scaffolds, presenting a broad range of functional group sustainability. This strategy also enables selective debenzylation of phenols in the presence of reduction-sensitive functional groups. The photocatalytic efficiency was further extrapolated in the fragmentation of lignin models and synthetic modification in manufacturing a FLAP inhibitor. Mechanistic studies, photophysical experiments and computations provide evidence for the involvement of an oxonium intermediate, generated through the photo-oxidation of the arene ring, which ultimately leads to the selective disintegration of C‒O bond, facilitated by the oxophilicity of silicon.

Developing recyclable heterogeneous catalysts for organic synthesis requires a deep understanding of active site architectures during surface-catalyzed reactions. Our approach, combining in-situ X-ray absorption spectroscopy and droplet-based microfluidics, investigates Suzuki–Miyaura coupling over palladium single-atoms on carbon nitride. The results highlight the need for distinct design criteria compared to traditional homogeneously catalyzed processes.

Abstract

Single-atom heterogeneous catalysts (SACs) hold promise as sustainable alternatives to metal complexes in organic transformations. However, their working structure and dynamics remain poorly understood, hindering advances in their design. Exploiting the unique features of droplet-based microfluidics, we present the first in-situ assessment of a palladium SAC based on exfoliated carbon nitride in Suzuki–Miyaura cross-coupling using X-ray absorption spectroscopy. Our results confirm a surface-catalyzed mechanism, revealing the distinct electronic structure of active Pd centers compared to homogeneous systems, and providing insights into the stabilizing role of ligands and bases. This study establishes a valuable framework for advancing mechanistic understanding of organic syntheses catalyzed by SACs.

Nature, Published online: 14 March 2024; doi:10.1038/d41586-024-00805-2

Year-long effort compiles comprehensive database of chemicals in plastics.

Synlett
DOI: 10.1055/a-2272-8045

Photoinduced carbamoylation of ethers using isocyanates as amide sources was accomplished under mild and environmentally friendly reaction conditions. A series of isocyanates were tolerated in this protocol to construct α-amide-substituted ether derivatives with desired yields. The method featured broad substrate scope and good functional group tolerance, which could play an important role in the construction of biological molecules with ethers.
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The solventless synthesis of peptides from unactivated amino acids was performed in a twin-screw extruder. The general method was applied to the preparation of dipeptides and tripeptides. Aspartame, a synthetic dipeptide, was also prepared in a continuous mode on large scale.

A photocatalytic strategy is developed for oxidative cleavage of C−C bond in lignin models and natural lignin at room temperature. This strategy exhibits several advantages, such as aerobic environment, abundant and inexpensive chloride salts, facile generation of chlorine radical in the presence of organocatalyst, thus representing a significant advancement in the valorization of lignin into highly value-added aromatic products.

Abstract

It is challenging to realize the selective C−C bond cleavage of lignin β-O-4 linkages for production of high-value aromatic chemicals due to its intrinsic inertness and complex structure. Here we report a light-driven, chlorine-radical-based protocol to realize the oxidative C−C bond cleavage in various lignin model compounds catalyzed by commercially available TPT and CaCl₂, achieving high conversion and good to high product yields at room temperature. Mechanistic studies reveal that the preferential activation of C_β−H bond facilitates the oxidation and C−C bond cleavage of lignin β-O-4 model via chlorine radical. Furthermore, this method is also applicable to the depolymerization of natural lignin extracts, furnishing the aromatic oxygenates from the cleavage of C_α−C_β bonds. This study provides experimental foundations to the depolymerization and valorization of lignin into high value-added aromatic compounds.

Nature, Published online: 14 February 2024; doi:10.1038/d41586-024-00390-4

Papers in engineering are under-represented, even neglected, in the journal. We want to change that.

Discover a sustainable, solid-phase catalyst for fast and efficient oxidation of a wide range of alcohols to their corresponding carbonyls in continuous flow! The new approach enables successful oxidation of various alcohols, including previously unreactive primary alcohols, with minimal catalyst loadings and rapid product accessibility.

Abstract

One of the most useful transformations in the synthetic chemist arsenal is the oxidation of alcohols to their corresponding carbonyl congeners. Despite its seemingly straightforward nature, this transformative reaction predominantly relies on the use of metals or hazardous reagents, making these processes highly unsustainable. To address this challenge, we have developed a sustainable metal-free method for the oxidation of alcohols in continuous flow. Using a solid phase hypervalent iodine catalyst and nBu₄HSO₅ as a phase transfer catalyst and co-oxidant, primary and secondary alcohols were selectively oxidized to the corresponding carbonyl motifs. This operationally simple continuous-flow set-up is highly robust (15 cycles run without significant catalyst leaching or loss of reaction efficiency), uses green solvents, such as acetonitrile or acetic acid, and is readily scalable.

A green and sustainable −COOH & −OH condensation solution polymerization method for FDCA-based polyesters.

Abstract

A green and sustainable −COOH & −OH condensation solution polymerization method was hereby reported for FDCA-based polyesters to avoid discoloration and toxic solvents. First, taking poly(ethylene 2,5-furandicarboxylate) (PEF) as the representative of FDCA-based polyester, enabling good white appearance PEF with M _n=6.51×10³ g mol⁻¹ from FDCA and ethylene glycol in green solvent γ-valerolactone (GVL), catalyzed by 4-dimethylaminopyridine (DMAP) and N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride (EDC). Additionally, the molecular weight of PEF was rapidly improved (M _n >2.5×10⁴ g mol⁻¹) via remelting polycondensation within minutes, with the dispersity still kept relatively low dispersity (Đ<1.40). Importantly, the −COOH & −OH condensation solution polymerization method was successfully applied for the synthesis of various FDCA-based polyesters, including diols with varying carbon chain lengths (3 to 11 carbons) and cycloalkyl diols, especially the applicability of this method to diols containing C=C double bonds, which was found to exhibit low heat resistance. Lastly, assisting with ¹³C labeled 1,4-succinic acid and in-situ ¹³C-NMR, an in-depth study of the possible catalytic mechanism was proposed, by which, EDC activated FDCA, and then DMAP catalyzed it with diol to yield macromolecular chain of polyester. Overall, the results provided a green and sustainable strategy for the synthesis of FDCA-based polyesters.

Nature, Published online: 09 February 2024; doi:10.1038/d41586-024-00383-3

Engineered petunia emits a continuous green glow thanks to genes from a light-up mushroom.

Nature, Published online: 31 January 2024; doi:10.1038/s41586-023-06939-z

Four future greenhouse gas emission scenarios for the global plastics system are investigated, with the lead scenario achieving net-zero emissions, and a series of technical, legal and economic interventions recommended.

Nature, Published online: 15 January 2024; doi:10.1038/d41586-024-00129-1

The latest outburst sent molten rock into the port town of Grindavík, igniting homes.