Volume 2 Issue 10, October 2019

The design of heterogeneous catalysts with tunable activity and selectivity constitutes a remarkable challenge. Now, a synthetic approach towards producing nanocrystals encapsulated within polymer layers has been developed, unravelling the principles to achieve control of transition state and product diffusion using CO oxidation as a case study.

Transition metal-catalysed bioorthogonal reactions are severely hindered in biomedical applications, mainly due to a lack of target specificity. Now, research shows that a trojan exosome vesicle can deliver a palladium catalyst specifically to progenitor cells for bioorthogonal catalysis, allowing localized prodrug activation.

Given the importance of enantioenriched β²- and β³-amino acids as building blocks, direct and versatile methods for their synthesis are highly coveted by organic chemists. Now, using easily accessible 1,3-oxazinane motifs, a regiodivergent and enantioselective C–H functionalization method permits their synthesis in a straightforward and practical fashion.

Imine reductases are promising catalysts, facilitating a direct stereoselective route to secondary amines. Now, protein engineering has created stable and efficient variants that allow their application in kilogram-scale synthesis.

While the oxidative addition of Pd to carbon–halide bonds is often regarded as being essentially irreversible, this is sometimes not the case. This Perspective looks at the conditions leading to reductive elimination of Pd from carbon–halide bonds, and the synthetic opportunities that this offers are discussed.

Encapsulation is an effective strategy to tune metal-catalysed reactions, although its potential has not been fully explored. Here, design principles and advanced understanding of the reactivity of different polymer-encapsulated Pd nanocrystals are provided using CO oxidation as a benchmark reaction.

Targeted therapy is an important approach to reduce the side effects of medicinal drugs. This work reports the synthesis of catalytically active Pd nanostructures in exosomes that selectively target cancer cells for drug activation using biorthogonal chemistry.

Small changes in catalyst synthesis can have large and often poorly understood effects on activity. Here the authors show how variation of post synthetic heat treatment—in combination with changes in metal loadings—can lead to the most efficient catalysts, and also identify the most likely active sites.

Here the enantioselective lithiation of Boc-1,3-oxazinanes is reported. Transmetallation to zinc allows for regiodivergent functionalization at either C4 or C5 positions via a ligand-controlled Negishi coupling, and subsequent oxidative cleavage gives easy access to both β²- and β³-amino acids.

Cu₂O is a promising photocatalyst, although its stability is compromised by a disproportionation reaction that leads to the formation of Cu and CuO. Now, a method is reported to stabilize Cu₂O nanocubes, rendering them highly active and stable for the photocatalytic reverse water–gas shift reaction.

One of the major challenges in C–H functionalization is to achieve selectivity when multiple bonds of similar reactivity are present. Now, a method to selectively amidate sterically and electronically similar β- or γ-C–H bonds that utilize different silver catalysts is reported, giving access to valuable 1,2- and 1,3-aminoalcohols.

Imine reductases have been regarded as one of the most promising enzymes by the pharmaceutical industry—but their industrial application is still lacking. This work reports the successful industrial application of an imine reductase, enabled by directed evolution.

Due to its importance, the water-gas shift reaction has been the subject of numerous studies; however, a unifying mechanistic picture has not yet emerged. Now, a combination of spectroscopic, kinetic and computational methods reveal the crucial role of carboxyl intermediate for this centuries-old process.

Enantioselective synthesis of atropisomeric biaryls is highly desirable due to the utility of these compounds as ligands and catalysts. Now, an organocatalytic polyketide cyclization is shown to convert poly-β-carbonyl compounds into binaphthalene derivatives in good enantioselectivities.

Reductive desymmetrization of 2,2-disubstituted cyclodiketones can provide valuable complex molecules with multiple chiral centres, but the generation of a single stereoisomer is difficult. This work addresses this synthetic challenge by engineering the activity and stereoselectivity of a carbonyl reductase.