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Ketyl radicals can be used in a range of reactions, but their generation often requires harsh conditions and a large excess of reductants. Now, a multicomponent, palladium-photocatalysed reaction between aldehydes, 1,3-butadiene and N, S, O and C nucleophiles to build architecturally complex homoallylic alcohols is reported wherein ketyl-type radicals are generated under mild conditions.
The selective functionalization of C=C bonds of alkenes is well studied, however, regio- and enantioselective transformations of the allylic C–H bond of unactivated alkenes are relatively underexplored. Now, a palladium-catalysed branch-selective and enantioselective allylic C−H alkylation of α-alkenes is reported. The process tolerates a wide range of α-alkenes, from chemical feedstocks to bioactive α-alkenes
Methods for the hydrofluoroalkylation of alkenes often require expensive reagents and have limited reaction scope. Now, a photoinduced manganese-catalysed hydrofluoroalkylation is reported, providing an array of fluoroalkyl-containing products from fluoroalkyl halides. Mechanistic studies reveal that the bidentate phosphine ligand plays a key role in atom transfer processes and increases the stability and lifetime of the metalloradical intermediate.
Synthetic routes to aminoglycosides are often long and rely upon the coupling of semisynthetically produced fragments. Now, an enantioselective, copper-catalysed hydroamination of benzene has been developed to enable access to the aminoglycoside antibiotic ribostamycin. This bottom-up strategy provides modular and expedient entry into the aminocyclitol class.
Strategies for the creation of topological carbon nanostructures have greatly advanced synthetic organic chemistry and materials science. Now, the synthesis of a Möbius carbon nanobelt, a molecule with a twist on belt-shaped aromatic hydrocarbons, is reported.
Making many stereogenic centres in a single step remains a challenge. Now, a combined nickel and copper-catalysed stereodivergent propargylic substitution process has been developed to access four stereoisomers of amathaspiramide D. The scope of the reaction is shown across a range of propargylic carbonate and aldimine ester substrates to generate a number of chiral propargylated α-amino ester products.
Enantioselective dearomatization of substituted non-activated benzene derivatives is a challenge due to their inherent stability. Now, a chiral samarium complex-mediated enantioselective dearomatization of substituted benzene derivatives is realized via intramolecular reductive coupling with ketyl radicals. The method has been used to synthesize a range of dearomatized bicycles with three stereogenic centres.
Making highly crystalline covalent organic frameworks (COFs) is challenging and existing linkages used for constructing COFs are limited in terms of variety and functionality. Now, crystalline COFs with imidazopyridinium linkages, which serve as precursors to N-heterocyclic carbenes, have been synthesized, expanding the reactivity of COFs by incorporating chemical ambivalence (electrophilicity and nucleophilicity) into the linkages. The COFs are also used as cathode materials in lithium–sulfur batteries.
The synthesis of graphynes has often been limited to using irreversible coupling reactions that are likely to result in materials that lack long-range order. Now, a periodically sp–sp2-hybridized carbon allotrope, γ-graphyne, is prepared using a reversible dynamic alkyne metathesis and managing the balance between kinetic and thermodynamic control. This material’s interlayer stacking and folding behaviour are also revealed.
The coupling of sulfonimidoyl fluorides and alkynes using sulfur(VI) fluoride exchange (SuFEx) reactions has not been available because of the intrinsic reactivity of the π component. Now, a divergent SuFEx process between sulfonimidoyl fluorides and alkynes to produce vinylic or acetylenic sulfoximines is reported. Mechanistic studies reveal the origins of the vinylic sulfoximines, and several synthetic transformations of the products demonstrate the utility of the process.
Cross-coupling reactions between aryl halides and alcohols using copper are challenging due to the energetically demanding oxidative addition of copper into aryl halides. Now, this high-barrier step is bypassed using an energy transfer or direct excitation strategy for copper-mediated cross-coupling reactions. This process enables the use of aryl chlorides as electrophiles and alcohols, amines and fluoride as nucleophilic coupling partners.
In nature, terpenes are made by forming isoprene chains and then folding the chains into carbocycles, followed by oxidation and rearrangement reactions. Now, inspired by nature, a range of polycyclic terpene structures are synthesized from phenols through a three-step sequence of prenylation, dearomatization and/or prenyl migration, and then epoxidation and/or radical cyclization. Several total syntheses of natural products are carried out using this approach.
The synthesis of all possible stereoisomers of drug candidates is essential for pharmaceutical development. However, only a few catalytic enantioselective methods provide access to all stereoisomers of molecules with contiguous stereocentres. Now, a strategy combining nickel and squaramide catalysis enables the stereodivergent α-propargylation of oxindoles and subsequently the synthesis of three natural products.
The [2+2+2] cyclotrimerization of two distinct alkynes and alkenes to form six-membered carbocycles is typically constrained by competing β-hydride elimination, low stereocontrol and the need to add reagents slowly. Now, a rhodium-catalysed three-component [2+2+2] cyclotrimerization with excellent chemo-, regio- and stereocontrol is reported that does not require any special operations. The utility of the process is shown and mechanistic studies probe the origins of the selectivity.
Although dinitrogen cleavage by metal complexes is known, the subsequent formation of N–H bonds using H2 is thermodynamically challenging. Now, ammonia synthesis using an Ir photocatalyst and H2 for the hydrogenation of a N2-derived molybdenum nitride is reported. The starting molybdenum nitride can be regenerated to complete a synthetic cycle for the preparation of ammonia from N2 and H2.
On-surface methods can be used to synthesize organic molecules, polymers and nanomaterials, however, the diversity of conceivable products is limited by the number of known on-surface reactions. Now, a phenylene ring-forming reaction on a gold surface by intermolecular oxidative coupling of isopropyl substituents on arenes is reported. The reaction is probed using bond-resolved imaging and computational modelling.
The fabrication of single-metal-atom chains in an atomically precise way is challenging. Now, a chemical vapour co-deposition method is reported for the synthesis of highly ordered single-atom chains of platinum with lengths of up to 20 nm on a wafer-scale. The metallic behaviour of the single-metal-atom chain is revealed by electronic measurements, first-principle calculations and complex network modelling.
The synthesis of α,α-disubstituted α-amino acids and peptides is often limited by the need to couple sterically hindered substrates. Now, copper-catalysed dehydrogenative coupling of α-amino acid Schiff bases and hydrocarbon feedstocks has been developed. Application of this method to peptides enables the incorporation of sterically hindered α-amino acid motifs, which impart a stabilizing helical effect on the peptide structure.
The pulp and paper industry produces approximately 50 million metric tons of lignin per year as a waste product. Here, lignin is shown to act as a photocatalyst for the solar-driven synthesis of hydrogen peroxide from H2O and O2 under visible light. Coupling this photocatalytic process with unspecific peroxygenases enables the enantioselective oxyfunctionalization of C–H bonds.
C-glycosides form the basis of numerous therapeutic compounds, but their synthesis using sustainable catalysts is a challenge. Here, an iron-catalysed reductive cross-coupling method is developed that couples glycosyl radicals, generated in situ from glycosyl chlorides, with unsaturated electrophiles. Mechanistic experiments indicate that the active catalytic species is a low-valent iron complex.
