Robby Vroemans

tert -Butyl nitrite-mediated regioselective annulation reaction is presented between substituted 5/2-amino-N-phenyl azoles and alkynes in acetonitrile for the synthesis of azole-fused quinolines.

Abstract

A metal- and photoredox-catalyst free unified approach for the synthesis of azole-fused quinolines via annulation reaction between substituted 5/2-amino-N-phenyl azoles and alkynes in the presence of tert-butyl nitrite (t-BuONO) in acetonitrile is reported. The reaction that proceeds via radical mechanism afforded solid products, which separated out in the reaction mixture and were isolated by filtration only. The participation of the azole substrate in the reaction ensued only if a functional group capable of accepting hydrogen was present on carbon adjacent to the carbon bearing the amino group. It is anticipated that such functional group facilitated stabilization of the diazoether transition state via hydrogen bonding.

Publication date: Available online 24 February 2022

Source: Chem

Author(s): Calvin V. Chau, Sajal Sen, Adam C. Sedgwick, Philip A. Gale, G. Dan Pantos, Sung Kuk Kim, Jung Su Park, Elisa Tomat, Jonathan F. Arambula, Anne E.V. Gorden, Hiroyuki Furuta

Nature, Published online: 24 February 2022; doi:10.1038/d41586-022-00579-5

Nature, Published online: 25 February 2022; doi:10.1038/d41586-022-00556-y

Abstract

A diastereoselective synthesis of borylated bicyclic 5-5 fused ring systems by a domino Ni-catalyzed hydroborylative polycyclization of allenynes has been developed. The reaction provides two new C−C and one C−B bonds and constitutes an atom-economical method. It occurs rapidly, in absence of inert atmosphere, with an inexpensive Ni-based catalyst and HBpin as boron source. The procedure showed excellent tolerance to functional groups and a wide scope. Derivatization of the borylated bicycles has been performed to explore the synthetic utility of the products. Experimental and DFT-calculation results suggest that the process starts by an oxidative cyclometallation involving Ni(0) and both the allene and the alkyne moieties, followed by a stereoselective σ-metathesis with HBpin. Formation of the second ring takes place through a non-fully coplanar 1,2-insertion into the Ni−H bond to give a nickelacyclohexene which finally evolves by reductive elimination.

Nature, Published online: 23 February 2022; doi:10.1038/d41586-022-00506-8

The synthesis of axially chiral compounds featuring a N−C stereogenic axis are presented and discussed, with an emphasis in catalytic asymmetric approaches. Diverse strategies and methodologies, based either on metal-catalyzed transformation or in organocatalytic activation, comprise not only the direct generation of the N−C axis but also desymmetrization, kinetic resolution, dynamic kinetic resolution and different types of chirality transfer.

Abstract

Molecules with restricted rotation around a single bond or atropisomers are found in a wide number of natural products and bioactive molecules as well as in chiral ligands for asymmetric catalysis and smart materials. Although most of these compounds are biaryls and heterobiaryls displaying a C−C stereogenic axis, there is a growing interest in less common and more challenging axially chiral C−N atropisomers. This review offers an overview of the various methodologies available for their asymmetric synthesis. A brief introduction is initially given to contextualize these axially chiral skeletons, including a historical background and examples of natural products containing axially chiral C−N axes. The preparation of different families of C−N based atropisomers is then presented from anilides to chiral five- and six-membered ring heterocycles. Special emphasis has been given to modern catalytic asymmetric strategies over the past decade for the synthesis of these chiral scaffolds. Applications of these methods to the preparation of natural products and biologically active molecules will be highlighted along the text.

Publication date: April 2022

Source: Trends in Chemistry, Volume 4, Issue 4

Author(s): Georgios Giannakakis, Sharon Mitchell, Javier Pérez-Ramírez

Catalysts, Vol. 12, Pages 244: Research Progress and Reaction Mechanism of CO2 Methanation over Ni-Based Catalysts at Low Temperature: A Review

Catalysts doi: 10.3390/catal12020244

Authors: Li Li Wenqing Zeng Mouxiao Song Xueshuang Wu Guiying Li Changwei Hu

The combustion of fossil fuels has led to a large amount of carbon dioxide emissions and increased greenhouse effect. Methanation of carbon dioxide can not only mitigate the greenhouse effect, but also utilize the hydrogen generated by renewable electricity such as wind, solar, tidal energy, and others, which could ameliorate the energy crisis to some extent. Highly efficient catalysts and processes are important to make CO2 methanation practical. Although noble metal catalysts exhibit higher catalytic activity and CH4 selectivity at low temperature, their large-scale industrial applications are limited by the high costs. Ni-based catalysts have attracted extensive attention due to their high activity, low cost, and abundance. At the same time, it is of great importance to study the mechanism of CO2 methanation on Ni-based catalysts in designing high-activity and stability catalysts. Herein, the present review focused on the recent progress of CO2 methanation and the key parameters of catalysts including the essential nature of nickel active sites, supports, promoters, and preparation methods, and elucidated the reaction mechanism on Ni-based catalysts. The design and preparation of catalysts with high activity and stability at low temperature as well as the investigation of the reaction mechanism are important areas that deserve further study.

Synthesis
DOI: 10.1055/s-0041-1737337

An efficient method for direct thiolation of anilides with thiols using NiCl2·6H2O as the catalyst is developed. Using this method, the desired products were successfully synthesized in moderate to good yields. Initial mechanistic studies suggest that this reaction proceeds through a radical pathway.
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Article in Thieme eJournals:
Table of contents  |  Abstract  |  Full text

The Front Cover shows how the “Dehalogenato” spell allows to replace halogen atoms by hydrogens, using a heterogeneous nickel catalyst supported on titanium oxide in the presence of dihydrogen. The practicality of this catalyst system is demonstrated by the complete dehalogenation of environmentally hazardous and polyhalogenated substrates such as polybrominated diphenyl ethers and others. More information can be found in the Research Article by D. K. Leonard, P. Ryabchuk, et al.