Volume 1 Issue 4, April 2022

Ring-forming reactions are at the heart of organic synthesis. Now, phenylene rings are synthesized from two isopropyl moieties on a gold surface. Resolving the intermediates of this (3+3) cycloaromatization reaction with atomic force microscopy offers mechanistic insight into the dimerization process.

Ammonia synthesis is of great interest owing to its use in fertilizers and as an energy carrier. However, it is challenging to develop a low-energy catalytic process for the formation of weak N–H bonds. Now, a photocatalytic system harnesses visible light to promote ammonia formation from N₂ and H₂.

The reversible formation of carbon–carbon bonds is key in many catalytic reactions but its mechanism is challenging to study. Now, a detailed investigation into a palladium-catalysed diastereoconvergent reaction uncovers a unique mechanism in which reversible β-carbon elimination is crucial for productive catalysis.

Conversion of greenhouse gases and other pollutants to fine chemicals is a global challenge. First-row-transition-metal catalysts show promise as cost-effective tools to combat environmental impacts by managing the carbon and nitrogen cycle. Nitrogen oxyanions are experiencing renewed interest for their use as N₁ feedstocks.

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.

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.

Reductive coupling reactions mediated by samarium(ii) iodide are useful transformations to form C–C bonds. The unique reactivity and selectivity of SmI₂ result in its wide application in key steps in the total synthesis of natural products. This Review outlines synthetic routes using this versatility to make important C–C bonds in complex products.

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.

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.

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.

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.