Research Briefing in 2022

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.

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.

Chemical reagents readily oxidize alkyl amines at sites adjacent to nitrogen. Achieving selective oxidation at specified non-adjacent sites is much more challenging. A computation-guided process is introduced that enables rapid optimization of enzymes for site-selective hydroxylation of a variety of cyclic amines.

Coordination of a photoswitchable chiral phosphate ligand to an achiral manganese(iii)-salen complex yields a catalyst that can produce either enantiomer of an epoxide from a single alkene substrate. This enantiodivergent catalysis is governed by the transfer of the chirality of the phosphate ligand to the manganese(iii)-salen complex.

Using anion-binding interactions to tackle challenging polymerizations is an ambitious goal and in its infancy. Seleno-cyclodiphosph(v)azanes are demonstrated to exert anion-binding interactions to precisely control the equilibrium between a dormant covalent precursor and active cationic species under mild conditions, thus enabling living cationic polymerization.

The construction of seven-membered carbocycles through cycloaddition reactions represents a longstanding challenge in organic synthesis. A study now reports a copper-catalysed enantioselective (4 + 3) cycloaddition between 2-aminoallyl cations and dienol silyl ethers that affords structurally diverse cycloheptanoids with high stereoselectivities and shows broad substrate scope.

Targeting 2D heterolayers by vertically stacking chemically different layers is a synthetic challenge. A generic and effective approach for synthesizing heterolayered oxychalcogenides using molten hydroxides as unconventional reaction media is introduced. This approach enables the rapid stacking of oxide and chalcogenide layers with precise control of the composition.

Quantum chemical calculations can not only provide mechanistic insight into known chemical reactions, but can also be used to predict the outcome of unknown reactions. In silico reaction screening with difluorocarbene is showcased, leading to new multicomponent dearomative cycloaddition reactions of pyridines that provide medicinally important fluorinated N-heterocycles.

Inspired by catenane chemistry, mechanically interlocked plasmonic nanostructures are synthesized in a bottom-up approach. The nanocatenanes exhibit mechanical helical chirality and, when combined with a thermoresponsive polymer, can actuate mechanical motion.

Metal-catalysed asymmetric allylic alkylations are now well established in natural product synthesis. When applied to butenolides, this reaction has always produced the C3-allylated products rather than the C5-allylated analogues. A method is introduced that provides a switch in regioselectivity and enables straightforward access to butenolide-containing natural products with complete stereocontrol.

A strategy to synthesize allenylphosphine derivatives with both P and axial chirality is developed and allows for diverse derivatizations of chiral phosphines. The Ni-catalysed enantioconvergent reaction occurs without racemization or symmetrization of the propargylic carbonate substrate, as demonstrated by combined experimental and computational methods.

Accessing reactive ketyl-type radicals in mild and controllable ways represents an ambitious target. A study now reports a multicomponent palladium-photocatalysed reaction between aldehydes, 1,3-butadiene and various nucleophiles that affords complex homoallylic alcohols through ketyl-type radicals.

Nature prepares diverse terpene architectures in a three-step process starting from isoprene building blocks. A new three-step synthetic procedure is introduced to prepare terpenes starting from readily available phenols. Similarly to those used in nature, this pathway provides reliable and efficient access to diverse and complex terpene architectures.

The construction of all stereoisomers of molecules containing contiguous stereocentres with full control of the absolute and relative stereochemical configuration has rarely been demonstrated. An approach involving dual-catalytic activation enables the stereodivergent α-propargylation of oxindoles with high stereocontrol and shows broad substrate scope.

A method for the synthesis of sterically congested α-amino acids and peptides using amino acid Schiff bases and hydrocarbons is developed. A superior helix-stabilizing effect of highly congested unnatural α-amino acids is demonstrated by circular dichroism measurements of synthesized peptides.