ceverelst

Spectroscopy reveals clues to dinos’ metabolisms

Nature Synthesis, Published online: 30 May 2022; doi:10.1038/s44160-022-00088-3

The Kolbe electrolysis is a transformation renowned for forging C(sp3)–C(sp3) bonds. However, it is challenging to selectively make cross-products — that is, form new bonds from different partners — using this reaction. Now, a nickel-catalysed ‘reductive Kolbe’ reaction enables a decarboxylative cross-coupling approach.

A widespread soil mineral, alpha-iron(III) oxyhydroxide, which is loaded onto an alumina support, works as a recyclable catalyst for CO₂ reduction. In the presence of a Ru^II photosensitizer, the catalyst produces formic acid with 80–90 % selectivity and an apparent quantum yield of 4.3 % at 460 nm.

Abstract

Photocatalytic conversion of CO₂ into transportable fuels such as formic acid (HCOOH) under sunlight is an attractive solution to the shortage of energy and carbon resources as well as to the increase in Earth's atmospheric CO₂ concentration. The use of abundant elements as the components of a photocatalytic CO₂ reduction system is important, and a solid catalyst that is active, recyclable, nontoxic, and inexpensive is strongly demanded. Here, we show that a widespread soil mineral, alpha-iron(III) oxyhydroxide (α-FeOOH; goethite), loaded onto an Al₂O₃ support, functions as a recyclable catalyst for a photocatalytic CO₂ reduction system under visible light (λ>400 nm) in the presence of a Ru^II photosensitizer and an electron donor. This system gave HCOOH as the main product with 80–90 % selectivity and an apparent quantum yield of 4.3 % at 460 nm, as confirmed by isotope tracer experiments with ¹³CO₂. The present work shows that the use of a proper support material is another method of catalyst activation toward the selective reduction of CO₂.

The Front Cover shows the valorisation of lignocellulose to various value-added chemicals. Here hydrogenation and dehydrogenation reactions play a crucial role, which can be catalysed by acids. Heteropolyacids are especially promising because they possess an adaptable Brønsted acidity. Due to their good solubility in water and organic solvents, recycling strategies are needed to implement industrially applicable processes applying the promising catalyst class. In their Review, L. Hombach et al. summarise the recent developments in the field of immobilisation and solidification of heteropolyacids and the application of these catalysts in bio-based conversions. More information can be found in the Review by L. Hombach et al.

Abstract

We report a one-pot reaction of (β-amino-α,α-difluoroethyl)phosphonates involving aza-Wittig reagents, in which, difluoromethylphosphonate-containing diazo and trifluoromethylated ketones assemble to furnish azo-containing α-fluorovinylphosphonates. Mechanism studies disclose a pathway, which contains an aza-Wittig reaction, water addition to hydrazone, and C−F bond cleavage with an aza-Wittig reagent as a key intermediate. This reaction is conducted at 60 °C affording a series of α-fluorovinylphosphonate compounds in 42–94% yields and Z-stereoselectivity. This work opens a vision for the difluoroalkyl-substituted diazos, and provides a strategy for the synthesis of α-fluorovinylphosphonate derivatives.

Nature, Published online: 20 April 2022; doi:10.1038/d41586-022-01036-z

Birds and their dinosaur ancestors had feathers, and now it seems that a distantly related group called pterosaurs had them, too. The finding extends the origins of feathers back to long before birds evolved, and sheds light on their role.

Nature Synthesis, Published online: 11 April 2022; doi:10.1038/s44160-022-00052-1

Molecular editing allows structures to be built up in terms of complexity, or changed or pruned one atom at a time using transformations which are mild and selective enough to be employed at the late stages of a synthetic sequence. In this Review, a subclass of molecular editing reactions termed ‘single-atom skeletal editing’ are described, with a particular focus on heterocycles.

Electron-rich aryl acetates derived from (renewable) phenolics were selectively reduced to the corresponding arenes using pinacolborane (HBpin) and a nickel-N-heterocyclic carbene (NHC) catalytic system in the green solvent dimethylcarbonate (DMC). The method is applicable to 4-propylguaiacyl acetate derived from pine wood.

Abstract

Acetate serves as a renewable and easily installed leaving group for selective deoxygenation of phenolics (ArOH). Ni-catalyzed hydrodeacetoxylation of aryl acetates (Ar−OAc) with HBpin in a green carbonate solvent selectively delivers the corresponding deoxygenated arenes (ArH). The method is also applicable to highly challenging guaiacyl and syringyl acetates, leaving −OMe groups intact without arene reduction. Renewable 4-propylguaiacol obtained from pine can also be transformed without significant loss in yield versus oil derived feedstock. The observed chemoselectivity for Ar−OAc versus ArO−Ac bond cleavage was rationalized based on mechanistic experiments and DFT calculations. ArOH side-product formation is attributed to direct competitive Ni-catalyzed reduction of the C=O bond. Hydrodeacyloxylation of a set of aryl alkanoates featured interesting chemoselectivity with a dramatic influence of the length and structure of the alkyl chain on catalysis.

Nature, Published online: 23 March 2022; doi:10.1038/s41586-022-04528-0

In extinct species including non-avian dinosaurs, bone density is shown to be a reliable indicator of aquatic behavioural adaptations, which emerged in spinosaurids during the Early Cretaceous.