LongLarf

Nature Communications, Published online: 22 April 2021; doi:10.1038/s41467-021-22621-2

1-(Isoquinolin-1-yl)naphthalen-2-ol (QUINOL) is an atropisomeric heterobiaryl that serves as a platform for the synthesis of other biaryl ligands useful in asymmetric catalysis. Here, the authors report a straightforward oxidative cross-coupling reaction between isoquinolines and 2-naphthols to efficiently access the QUINOL scaffolds in a metal-free manner.

Metalloprotein properties can be tuned by changing the primary metal coordination sphere. Here amber stop codon suppression with engineered pyrrolysyl-tRNA synthetases was used to replace the proximal histidine in myoglobin with a range of new amino acids. In addition to tuning the heme redox potential over a >200 mV range, these noncanonical ligands modulate the protein's carbene transfer activity with ethyl diazoacetate.

Abstract

Changing the primary metal coordination sphere is a powerful strategy for tuning metalloprotein properties. Here we used amber stop codon suppression with engineered pyrrolysyl-tRNA synthetases, including two newly evolved enzymes, to replace the proximal histidine in myoglobin with N_δ-methylhistidine, 5-thiazoylalanine, 4-thiazoylalanine and 3-(3-thienyl)alanine. In addition to tuning the heme redox potential over a >200 mV range, these noncanonical ligands modulate the protein's carbene transfer activity with ethyl diazoacetate. Variants with increased reduction potential proved superior for cyclopropanation and N–H insertion, whereas variants with reduced E ^o values gave higher S–H insertion activity. Given the functional importance of histidine in many enzymes, these genetically encoded analogues could be valuable tools for probing mechanism and enabling new chemistries.

Nature Chemistry, Published online: 19 April 2021; doi:10.1038/s41557-021-00662-w

Although strategies for the automated assembly of compounds of pharmaceutical relevance is a growing field of research, the synthesis of small-molecule pharmacophores remains a predominantly manual process. Now, an automated six-step synthesis of prexasertib is achieved by multistep solid-phase chemistry in a continuous-flow fashion using a chemical recipe file that enables automated scaffold modification through both early and late-stage diversification.

Isodesmic C–H functionalization reactions are extremely rare. Herein we report the first Pd(II)-catalyzed isodesmic C–H iodination of arenes using 2-nitrophenyl iodides as the mild iodinating reagents. Unusual C–I reductive elimination occurred in preference to competing C–C coupling in this reaction. Assisted by aliphatic carboxyl directing groups, a range of hydrocinnamic acids and related arenes could be selectively iodinated at either meta- or ortho-positions of the phenyl ring. Remote diastereoselective C–H activation was also promising. This method may open up a new way to iodinate challenging substrates.

This minireview reported the synthesis of the 5 and 4‐halo‐1,2,3‐triazoles which are very important key intermediates to the synthesis of 4, 5‐disustituted‐1,2,3‐triazoles. The major derivatives are the iodo‐triazoles followed by the bromide and chloride triazoles. The fluoro‐triazoles appeared more recently and are prepared by different methods.

Abstract

1,2,3‐triazoles are important scaffolds in several fields, and there is still a demand to construct these compounds, most notably the disubstituted 4, 5 compounds. The latter are obtained in different ways, but the 4‐ and 5‐halo triazoles are generally the key intermediates in their synthesis. These halogenated compounds are an extraordinary platform leading to a great chemical diversity around the 4 and 5 positions. However, their own pathways are generally put aside at the expense of the substituted triazoles. This review is focused on the main synthesis of 5‐ and 4‐halo 1,2,3‐triazoles from cycloaddition followed or not by halogenation reaction. Unlike the halogens (iodine, bromine, and chlorine), the 5‐ and 4‐fluoro 1,2,3‐triazoles will be presented separately due to their relatively more difficult and still recently challenging synthesis.

Nature Catalysis, Published online: 15 April 2021; doi:10.1038/s41929-021-00594-1

Transformations in organic chemistry are mainly limited to the incorporation of only one equivalent of the greenhouse gas CO2 per substrate. Now, a visible-light photoredox-catalysed dicarboxylation of alkenes, allenes and arenes allows the incorporation of two CO2 molecules into organic compounds.

Publication date: 21 May 2021

Source: Tetrahedron, Volume 88

Author(s): Gábor Mikle, Fanni Bede, László Kollár

Synlett
DOI: 10.1055/s-0040-1706034

The high abundance of C–H bonds in organic molecules makes C–H functionalization a powerful approach to quickly increase the complexity of an organic molecule. However, the high abundance of C–H bonds also provides a challenge to C–H functionalization reactions: selectivity. While most C–H functionalization reactions produce mixtures of different products for most substrates, we have developed a highly selective method for aromatic C–H functionalization via sulfonium salts. The reaction does not require a certain directing group to be selective. The introduced functional group is a sulfonium group, which participates in various follow-up reactions such as palladium-catalyzed cross-coupling reactions and photoredox catalysis. Here we discuss our pathway to develop the reaction as well as its scope and utility.1 Introduction2 Site-Selective Synthesis of Sulfonium Salts3 Sulfonium Salts in Palladium-Catalyzed Cross-Coupling4 Sulfonium Salts in Photoredox Catalysis5 Sulfur(IV) Reductive Elimination6 Cine Substitution7 Conclusion
[...]

Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

Article in Thieme eJournals:
Table of contents  |  Abstract  |  Full text

An amine–borane system has been discovered to deliver a reversible dehydrogenation/regeneration at room temperature. It provides a new way for hydrogen storage under mild conditions.

Abstract

Amine–borane complexes have been extensively studied as hydrogen storage materials. Herein, we report a new amine–borane system featuring a reversible dehydrogenation and regeneration at room temperature. In addition to high purity H₂, the reaction between ethylenediamine bisborane (EDAB) and ethylenediamine (ED) leads to unique boron–carbon–nitrogen 5‐membered rings in the dehydrogenation product where one boron is tricoordinated by three nitrogen atoms. Owing to the unique cyclic structure, the dehydrogenation product can be efficiently converted back to EDAB by NaBH₄ and H₂O at room temperature. This finding could lead to the discovery of new amine boranes with potential usage as hydrogen storage materials.