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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.
The Paternò–Büchi reaction is a useful approach in organic synthesis to prepare oxetanes. Understanding the mechanism of this reaction is required for the prediction and control of the diastereoselectivity of the products.
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.
A polymerization strategy — termed CAMMP — combines two types of olefin metathesis monomers to produce degradable copolymers without sacrificing the mechanical properties of the equivalent homopolymer.
Isolating 2D materials from non-van der Waals (non-vdW) layered structures by mechanical cleavage is challenging owing to strong electronic coupling between adjacent layers. We show that mechanically sliding the layers weakens interlayer interactions, enabling delamination of a wide range of non-vdW layered structures to produce 2D sheets with unusual thickness-dependent physical properties.
Polyvinyl chloride (PVC) is challenging to recycle owing to the formation of hydrochloric acid during depolymerization at high temperatures. Now, a method for upcycling PVC that relies on its intrinsic reactivity in a low-intensity electrochemical process is reported, which can be exploited to chlorinate arenes.
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.
1,4-Dicarbonyls are challenging targets owing to the natural-polarity mismatch of potential reaction partners. This Review discusses methods for 1,4-dicarbonyl synthesis based on the coupling of two carbonyl-containing fragments as well as methods that involve non-carbonyl precursors. A spotlight on 1,4-dicarbonyls in total synthesis underlines the diversity of approaches for this motif.
Controllable cleavage and conversion of strong C(sp3)–H bonds remains a challenging task in organic synthesis. Here, a reaction design combining hydrogen atom transfer and copper catalysis is developed which allows enantioselective alkene difunctionalization using aliphatic C–H bond activation.
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.
Chiral tetrahedral carbon atoms bearing functional groups amenable to functionalization offer numerous synthetic opportunities. Catalysed by copper pyridine-bis(oxazoline) complexes, the developed alkynylallylic substitution provides 3-substituted 1,4-enynes with excellent regio- and stereocontrol.
Inverse vulcanization uses high temperatures to form sulfur-rich polymers. Now, using a photoinduced method, polymerization occurs at ambient conditions enabling a broader selection of viable comonomers compared with existing routes, as well as eliminating the formation of toxic gas.
Atomically thin materials have exciting physicochemical properties but multi-element and non-layered 2D materials are difficult to prepare by conventional methods. Now, a flux-assisted method is reported, enabling the synthesis of such 2D materials by confining reaction space.
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.
Nucleophiles are versatile reagents that can engage in a plethora of C–C and C–heteroatom bond-forming reactions. This Review examines their increasing role in transition metal-catalysed directed C–H functionalization, with a focus on synthetic approaches involving organometallic nucleophiles and X-based (X = N, O and S) coupling partners.
A method for the kinetic resolution of diverse planar chiral multisubstituted metallocenes through Rh-catalysed asymmetric C–H arylation of pre-functionalized metallocenes is developed. This general strategy allows for the synthesis of planar chiral 1,2- and 1,3-disubstituted metallocenes bearing a wide range of functional groups.
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.