Volume 11 Issue 5, May 2019

Bruce C. Gibb explains why plastic isn’t always fantastic.

The direct formation of C–N bonds onto arenes provides a simple route to synthesize a variety of important products. Now, formation of a highly polarized, aminium radical cation enables direct C–H amination, allowing the coupling of an exceptionally broad range of alkyl amines and arenes.

Bacterial communication is a potential strategy to control bacterial behaviours and thus, attenuate pathogen infectivity; however, identifying the signalling molecules that regulate communication pathways is challenging. Now, a robust strategy to rapidly identify previously unknown signalling peptides has been developed. This approach provides a means to map out and decipher bacterial signalling mechanisms.

Two recent back-to-back meetings conveyed a common set of ongoing challenges for the fields of organocatalysis, photoredox catalysis and photochemistry.

Biochemical and cellular assays are often plagued by false positive readouts elicited by nuisance compounds. A significant proportion of those compounds are aggregators. This Review discusses the basis for colloidal aggregation, experimental methods for detecting aggregates and analyses recent progress in computer-based systems for detecting colloidal aggregation with particular emphasis on machine learning [In the online version of this Review originally published, the graphical abstract image was incorrectly credited to ‘Reven T.C. Wurman / Alamy Stock Photo’ this has now been corrected].

Magic-number Au₁₁ clusters containing N-heterocyclic carbene (NHC) ligands are prepared by ligand exchange on known phosphine clusters and the introduction of even a single NHC results in improved cluster stability. The use of NHC-containing clusters in the electrocatalytic reduction of CO₂ to CO is described and correlates with cluster stability.

The synthesis of aryl amines is traditionally achieved through aromatic nitration or transition metal-catalysed cross coupling. Now, photocatalysis provides a route for the direct and selective C–H amination of aromatics with alkyl amines, without the need for pre-functionalization. This reaction tolerates a variety of functional groups and can be used for late-stage modification.

A concise strategy for engineering functional, supramolecular protein complexes has now been developed based on single-mutation-mediated covalent tethering. Metalloproteins designed with this method can sustain large alterations to the metal coordination environment, bind small molecules, exhibit reversible redox activity and sustain large alterations to the protein structure.

It is difficult to recover materials for re-manufacturing and re-use from plastics that are compounded with colourants, fillers and flame retardants. Now, it has been shown that alternative plastics based on dynamic covalent poly(diketoenamine)s depolymerize in strong aqueous acids and enable triketone and amine monomers to be isolated and upcycled into new plastics.

While much effort has been devoted to understanding how nanoparticle morphology can be leveraged to improve catalytic activity, engineering their microstructure from first principles to this end has remained difficult. Now a methodology for designing the optimal structure of a solid catalyst with the aim of achieving the highest possible activity for surface-sensitive reactions has been developed.

RNA is usually considered to be the first genetic polymer, with DNA a product of a biochemical pathway that arose after the origin of life. Now, studies into the prebiotic phosphorylation of an RNA nucleoside reveal pathways for the synthesis of DNA building blocks, providing experimental support for a prebiotic link between RNA and DNA.

Bacteria communicate through excretion of minute amounts of chemical signalling molecules that affect virulence, biofilm formation and colonization. In staphylococci, these molecules, called autoinducing peptides, are macrocyclic thiolactone-containing peptides. Now, a simple enrichment method, based on chemoselective capture on polymer beads, has been developed that enables the identification of previously unknown autoinducing peptides.

Synthetic dissipative systems, formed by out-of-equilibrium self-assembly processes, can mimic some of the properties of biological systems, but often show poor mechanical performance. Now, a shear-induced transient hydrogel has been prepared that is also highly stretchable. The system is based on coordination interactions between Cu(ii) centres and the pendant carboxylate groups of a pseudopolyrotaxane.

Nitriles are widely used in chemistry and are found in many bioactive compounds but, despite recent advances, there are no broadly applicable approaches for the synthesis of di- or tri-substituted alkenyl nitriles. New catalytic cross-metathesis strategies now allow direct access to a wide range of Z- or E-di-substituted cyano-substituted alkenes and their tri-substituted variants.

In a ruthenium-catalysed living ring-opening metathesis polymerization, one metal centre is required for each polymer chain, and this requires high catalyst loadings when aiming for short polymer chains. Now, it has been shown that a degenerative reversible chain-transfer process enables the synthesis of ring-opened metathesis polymers with controlled molecular weight, using only catalytic amounts of a ruthenium complex.