Articles in 2022

Reactions induced by σ-aromaticity are uncommon compared with those induced by π-aromaticity. Now, a π- and σ-aromaticity relay strategy is developed to realize the ring contraction of metallacyclobutadiene to metallacyclopropene. This reaction involves the release of π-antiaromaticity to afford a π-aromatic intermediate, followed by ring reclosure to form σ-aromatic metallacyclopropene.

Controlling diastereodivergent light-driven processes remains synthetically challenging. Here, we disclose how the light source and steric parameters can be used to control the diastereoselectivity of [2 + 2] heterocycloaddition processes, such as in Paternò–Büchi reactions, and provide access to previously inaccessible stereochemical variants.

Mechanical cleavage of layered materials to obtain two-dimensional (2D) sheets is restricted to materials with interlayer interactions dominated by van der Waals (vdW) forces. Here, calendering is used to weaken interlayer binding in non-vdW layered structures (metals, semiconductors and superconductors) allowing mechanical exfoliation to obtain 2D sheets with thickness-dependent properties.

Enantioselective difunctionalization of alkenes mediated with radicals and using selective C–H bond activation remains unexplored. Now, an asymmetric 1,2-oxidative alkylation of conjugated dienes, based on direct functionalization of strong and neutral C(sp³)–H bonds, is reported using a combination of hydrogen atom transfer and copper-catalysed reactions.

Automated organic synthesis is often limited to making simple molecules, requiring a small number of synthetic steps, because of the complexity and variety of organic molecules. Now, a robotic platform has been instructed to build complex structures, such as the core fragment of (+)-kalkitoxin, in a stereochemically controlled and iterative manner.

Asymmetric C–H functionalisation provides efficient synthetic routes to chiral metallocenes; however, these methods are often limited by the substitution patterns that can be accessed. Now, a Rh-catalysed enantioselective C–H arylation provides access to chiral 1,2-disubstituted and 1,3-disubstituted metallocenes via kinetic resolution of pre-functionalised metallocenes.

Stereoselective alkynylallylic substitution reactions are underexplored compared with propargylic and allylic substitutions. Now, a copper-catalysed intermolecular and decarboxylative alkynylallylic amination, alkoxylation and alkylation strategy has been developed for the synthesis of chiral 1,4-enynes. Mechanistic studies suggest that the formation of a dinuclear copper allenylidene is the rate-limiting step.

Torus knots are assembled in a contra-helical tubular manner by coaxially nesting a small multistranded helix within a larger reverse helix. This approach enables the near-quantitative one-step syntheses of four iron(II)-templated trefoil knots. The spin-crossover properties of the iron(II) centres in the knots are tuneable by altering the intramolecular strain.

Alternaric acid is a known starting point for herbicide development. Now, the development of a total synthesis enables structure–activity relationship profiling of compound libraries, which, combined with phenotypic screening and molecular modelling, identifies lead compounds with enhanced herbicidal activity compared with alternaric acid.

Developing highly elastic and conductive hydrogels is challenging, especially for use in harsh environments including organic solvents and extreme temperatures. Now, a self-assembly and in situ polymerization method is reported for the fabrication of highly compressible and environmentally adaptive conductive hydrogels with concrete-type constituents and high-tortuosity interconnected cellular architectures.

The complexity of carbohydrate structures makes their synthesis challenging. Now, an automated glycan synthesizer is reported which is capable of preparing a library of bioactive oligosaccharides, including a fully protected fondaparinux pentasaccharide. Furthermore, the synthesizer can rapidly assemble arabinans up to 1,080-mer size, starting from monosaccharide building blocks.

Two-dimensional materials have many desirable properties but controllable synthesis is difficult. Now, a flux-assisted growth approach has been designed to reproducibly prepare high-quality, atomically thin materials. Eighty atomically thin composite flakes have been prepared by this approach.

Degradable polymers are needed to overcome the environmental persistence of the materials. Now, cyclic–acyclic monomers metathesis polymerization is reported to produce degradable thermoset, thermoplastic and elastomeric polymers. The material properties and degradability of the polymers are investigated after different treatment methods during their synthesis.

Selective oxidation of ring C–H bonds is an attractive route to functionalized cyclic amines, which are versatile intermediates in drug synthesis. Now, engineered P450 enzymes, designed with computational guidance to disfavour undesired products, are reported to oxidize all unactivated C–H bonds in cyclic amines with high selectivity.

Developing a bench-stable glycosyl donor of multifunctional sugar residues that can be activated under mild conditions is a challenge in carbohydrate chemistry. Now, stable glycosyl sulfones are used in a photoinduced method for desulfonylative cross-coupling to prepare a range of C- and S-glycosides.

Developing enantiodivergent catalysts capable of preparing both enantiomeric products from one substrate in a controlled fashion is challenging. Now, a manganese(III)-salen complex with a chiral photoswitchable phosphate counterion is reported for the epoxidation of alkenes in a stereoselective manner, where irradiation with light allows access to either enantiomer of the epoxide.

Plastic waste poses a serious economic, ecological and environmental threat. Here, non-recyclable, post-consumer microplastics are used as an electron feedstock for biosynthetic reactions in a photoelectrocatalytic system. The microplastics are simultaneously broken down into organic fuels, meaning that this system provides valuable chemicals at both the anodic and cathodic sites.

β-hydride and β-heteroatom eliminations are elementary steps in many catalytic reactions used in the synthesis of drug molecules and polymers. However, the elimination processes often compete leading to unpredictable outcomes. Here, a series of mechanistically informed selection rules are developed to selectively achieve the desired elimination.

α,α-Dideutero carboxylic acids are common precursors for isotopically labelled molecules; however, their synthesis often requires high temperatures with strong bases or precious metals. Now, the α-deuteration of carboxylic acids has been developed under mild conditions using a ternary catalyst system of K₂CO₃, pivalic anhydride and 4-dimethylaminopyridine.

Current synthesis of 2D crystalline superconductors mainly limits them to layered materials. Now, crystalline, non-layered 2D PdTe has been synthesized by inducing interfacial reactions at a solid–solid interface, exhibiting 2D superconductivity with a thickness-dependent onset critical temperature of ~2.56 K.