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The ring opening of cyclopropenes provides a compelling platform for the rapid synthesis of various polysubstituted acyclic alkenes, but radical-mediated reactions of this type remain underexplored. Here, the authors report an aminative ring-opening of cyclopropenes with iron-aminyl radical to afford tetrasubstituted alkenyl nitriles.

A method for the site-selective C–H borylation of arenes and heteroarenes is described, in which BBr₃ acts as both a reagent and a catalyst.

The synthesis of polycyclic structures bearing partially saturated (hetero)arenes is important as many of these structures have biological relevance. Here the authors develop a one-step method for selective dearomative functionalization of feedstock (hetero)arenes via organophotocatalysis.

The introduction of fluorine into organic molecules often requires prefunctionalised molecules or protection of reactive functional groups. Here, the authors report a biocatalytic method for the trifluoromethylation of unprotected phenols under mild conditions.

Single-molecule electrical detections clarify both productive and hidden degenerate pathways of ring-closing metathesis, and enable precise on-device synthesis of a single polymer with single-monomer-insertion-event resolution.

The umpolung functionalization of imines bears vast synthetic potential, but polarity inversion is less efficient compared with the carbonyl counterparts. Now, an alternative strategy exploiting chiral phosphoric acid catalytic aromatization has been developed, affording structures possessing a central chirality or a stereogenic C–N axis with high efficiency and enantiocontrol.

Axial chirality is a key element in many valuable compounds, such as ligands in organic chemistry or pharmaceuticals. Now the catalytic atroposelective synthesis of acyclic 1,3-dienes by chiral phosphoric acid-catalysed bromination is described, expanding the chemical space of axially chiral compounds.

Hybrid 2D/3D ring systems have emerged as important scaffolds in medicinal chemistry, but efficient protocols for their synthesis are scarce. Now, energy-transfer-mediated cascade dearomative [2 + 2] cycloaddition/rearrangement reactions are developed to provide facile access to pyridine-fused 2D/3D ring systems.

Hydrocarbon fuels contain organosulfur molecules that poison catalytic converters and release toxic sulfur oxides when the fuel is combusted. Here the authors demonstrate that the sulfur concentration in diesel fuel can be reduced to very low levels using a potassium tert-butoxide and silane system.

Distinguishing remote C–H bonds on adjacent carbon atoms is a fundamental challenge because of a lack of electronic or steric bias. Now, differentiation of distal C–H bonds that are adjacent to each other has been achieved by combining selective remote C–H activation—based on distance and geometry—with a norbornene-assisted palladium migration.

In situ chirality identification for single-molecule systems is not a straightforward task. Now, real-time chirality identification during a Michael addition reaction has been realized by continuous measurements of spin-polarized currents through a single-molecule junction, providing a promising method for studying symmetry-breaking reactions.

Catabolizing lignin-derived aromatic compounds requires an aryl-O-demethylation step. Here the authors present the structures of GcoA and GcoB, a cytochrome P450-reductase pair that catalyzes aryl-O-demethylations and show that GcoA displays broad substrate specificity, which is of interest for biotechnology applications.

A ternary catalytic method combining organic photoredox, hydrogen atom transfer and nickel catalysis is reported. This combination can directly arylate the allylic C(sp³)–H bonds of a broad range of readily available olefins. Mechanistic experiments, coupled with density functional theory calculations aid the elucidation of the ternary catalytic cycle and the origin of regioselectivity.

Phthaloyl peroxide functions as a selective oxidant of C–H bonds in the transformation of arenes to phenols under mild conditions, in a reaction that is compatible with a wide array of functional groups.

The X-ray crystal structure of the epoxide hydrolase Lsd19 in complex with its substrate and product analogue is determined, providing insight into a general mechanism of enzyme-catalysed formation of polyether natural products.

Enzymatic Diels–Alder reactions are of high synthetic interest, but mechanistic insights remain scarce. Now, a structure of the Diels–Alderase CghA in complex with its product is reported, a catalytic mechanism proposed and the enzyme is engineered to form the energetically disfavoured exo adduct.

Difluorocarbene transfer is mostly limited to reactions that utilize its intrinsic electrophilicity. Now, a controllable palladium-catalysed difluorocarbene transfer reaction is reported that involves nucleophilic and electrophilic palladium difluorocarbene species. The selective reactions between arylboronic acids and the difluorocarbene precursor BrCF₂PO(OEt)₂ give four different products—difluoromethylated and tetrafluoroethylated arenes and their corresponding fluoroalkylated ketones.

The staged hydrolysis of N-methylimidodiacetic (MIDA) boronates is a prerequisite for their application in small-molecule constructions. Mechanistic studies now show that two distinct hydrolysis mechanisms operate in parallel, the partitioning — which is dependent on the pH, water activity and homogeneity of the medium — can be readily quantified by ¹⁸O incorporation.

A computational protein design was used to generate eight enzymes that were able to catalyse the Kemp elimination, a model reaction for proton transfer from carbon. Directed evolution was used to enhance the catalytic activity of the designed enzymes, demonstrating that the combination of computational protein design and directed evolution is a highly effective strategy to create novel enzymes.

Viridicatin is a fungal alkaloid. Here, the authors identify and characterize the cyclopenase that catalyzes the last step of its biosynthesis in Aspergillus nidulans, the conversion of cyclopenin to viridicatin, and find that the reaction proceeds via an unusual elimination mechanism.

Enzymatic catalysis of pericyclic [6+4] cycloaddition reactions to form ten-membered rings is observed during biosynthesis of the macrocyclic antibiotic streptoseomycin, and the mechanism of these transformations is established.

The discovery of amplifying autocatalysis in a pyridine-3-carbaldehyde system facilitates a mechanistic deconstruction of the Soai reaction. A tetrameric autocatalyst, assembled by a combination of steric effects and nitrogen–zinc coordination, activates the substrate by two-point binding. This is followed by intra-complex isopropyl group transfer that generates the product alkoxide with high homochiral fidelity.

Although general inhibitors of the ubiquitin-proteasome system have been reported, compounds targeting specific ubiquitylation enzymes should be beneficial in clinical applications and basic research. Aghajan et al. present an inhibitor of the yeast SCF^Met30 E3 ligase that prevents the binding of the Met30 F-box protein to the core ligase complex.