Articles

The role of cationic intermediates in the benzylidene-directed synthesis of 1,2-cis glycosidic linkages is unclear. Now cryogenic infrared spectroscopy provides insight into the S_N1 mechanism of benzylidene-directed glycosylation reactions. The analysis reveals that cationic intermediates form anhydro cations through a two-step process, which correlates with the observed stereochemical outcome.

Intermolecular [2+2+1] cycloaddition reactions are challenging owing to issues with chemoselectivity. Now a Rh-catalysed enantioselective [2+2+1] cycloaddition reaction using three different 2π-components is reported. The process can form a broad range of synthetically valuable chiral 3-methylenecyclopent-1-ene derivatives with excellent selectivity.

While facile methods to prepare o- and p-benzynes exist, m-benzyne in the ground state has remained experimentally inaccessible. Now, the room-temperature and atmospheric-pressure synthesis of m-benzyne in solution is reported. Experimental and theoretical investigations reveal that m-benzyne behaves as a potent electrophile but shows weak free-radical character.

The selective formation of C–C bonds using carbynes or carbyne equivalents is difficult due to their highly reactive nature. Now, a three-component formal cycloaddition reaction between phosphorus ylides, electron-rich olefins and electron-deficient olefins is reported, using the photocatalytic carbyne reactivity of phosphorus ylides.

Increasing the metal loading of single-atom catalysts (SACs) typically results in aggregation, which can have a detrimental effect on catalytic performance. Now, a nitrogen-doping-assisted atomization approach is reported that transforms metal-sulfide nanoparticles into ultrahigh-density metal–nitrogen–carbon SACs.

Methods for asymmetric alkyl–alkyl bond formation between sp³-hybridized carbon atoms, C(sp³)–C(sp³), are limited yet highly desirable. Now an approach for asymmetric alkyl–alkyl bond formation by Ni-catalysed cross-coupling between alkenes has been developed to construct tertiary stereogenic carbon centres with head-to-tail regioselectivity and excellent chemo- and enantioselectivity.

Heteroatom-embedded hexa-peri-hexabenzocoronenes (HBCs) display notable properties, but the selective incorporation of heteroatoms into the HBC core makes their synthesis difficult. Now a two-step process for the synthesis of 3a²-azahexabenzocoronenium salts is reported. The process comprises a formal [3 + 3] cycloaddition between azomethine ylides and cyclopropenes, followed by mechanochemical cyclization.

Eliminating the substrate-specific constraints in alkene hydroalkylation reactions, where heteroatom-containing substrates are often required to achieve enantioselectivity, remains a challenge. Now a cobalt-hydride catalyst is shown to overcome heteroatom constraints through C–H···π interactions between substrates and catalysts, enabling the efficient construction of chiral tertiary carbon centres at the benzyl position.

Small γ-Fe₂O₃ nanoparticles (<2 nm) encapsulated in the pores of a conductive metal–organic framework enable the efficient electrosynthesis of urea through the co-reduction of CO₂ and nitrate under neutral conditions.

Three-dimensional nitrogen-rich bridged systems are of great importance in drug design. Now, a synthetic strategy enabling their preparation from readily available starting materials has been developed. This approach provides access to unstabilized C,N,N-cyclic azomethine imines, which are obtained as bench-stable dimers and undergo [3 + 2] cycloaddition reactions with various dipolarophiles.

Metal–π interactions typically hinder metal-catalysed C–H functionalization reactions involving large π-conjugated systems. Now, an iron-catalysed aza-annulation method, employing a bulky trisphosphine ligand and an aluminium base, proves efficient for large π-extended substrates, holding promise for electronic materials discovery.

In vitro biosynthetic analysis reveals that a single trans-AT polyketide synthase (PKS) module iteratively enables five rounds of polyketide elongation and interacts with both the preceding and succeeding PKS enzymes to produce the 17-membered macrocyclic polyketide chejunolide.

CdSe nanocrystals are used as synthetic templates for HgSe and alloyed Hg_xCd_1−xSe nanocrystals with tunable, diverse structures. Cd²⁺-to-Hg²⁺ exchange occurs homogeneously and completely through interdiffusion enhancement with Ag⁺ catalysts and with surface cation exchange modulated by alkylthiol ligands.

A modular synthetic procedure is reported in which a selenium capping agent hinders phase segregation and aggregation while sequencing the priority of metals that migrate into the substrate lattice, leading to a layer-by-layer growth of ordered nanostructures.

The dynamic kinetic resolution of secondary alcohols for the synthesis of macrocycles is reported. This approach uses a chemoenzymatic method to form enantioenriched 14–19-membered macrolactones and macrodiolides and can be used to prepare bioactive natural products.

Saturated heterocycles are prevalent motifs in organic synthesis but their synthesis still presents persistent challenges. Now, a hypervalent iodine(III)-mediated selective intramolecular C(sp³)–H functionalization, facilitated by hexafluoroisopropanol, is reported, which via single-electron transfer provides access to pyrrolidines, piperidines and O-heterocycles in the presence or absence of light.

A one-pot, metal-free synthesis of nitrogen-containing polycyclic aromatic heterocycles is reported by using a sequence of imine condensation, nucleophilic aromatic substitution and intramolecular Friedel–Crafts reactions. Subsequently, in situ crystallization using precipitation under high pressure yields a series of substituted and unsubstituted 5,11,17-triazatrinaphthylene compounds.

Biocatalytic methods for the synthesis of chiral cyclohexenones bearing quaternary stereocentres through oxidation and reduction reactions are reported. Mechanistic studies reveal the role of active-site residues in the oxidation process and inform the development of the enzymatic reduction reaction.

The use of alkyl halides in radical cross-couplings generally requires silicon reagents as halogen abstractors. Now Me₃N–BH₃ is reported to facilitate these couplings with both aryl bromides and aryl boronic acids under either nickel or copper catalysis.

Artificial metalloenzymes are useful catalysts in synthesis, but their use in cells is a challenge. Now, the development of an engineered whole-cell enzymatic cascade, which converts glucose-derived fatty diacids into cycloalkenes, is reported. The cascade process combines a decarboxylase with an artificial metalloenzyme that catalyses an abiotic olefin metathesis reaction.