Electrochemical Oxidative Csp3—H/S—H Cross‐Coupling with Hydrogen Evolution for Synthesis of Tetrasubstituted Olefins

Tetrasubstituted olefins are significant scaffolds as they are prevalent in many biologically active compounds and versatile building blocks for organic synthesis. Herein, we report an electrochemical oxidative Csp³—H/S—H cross‐coupling reaction, in which various tetrasubstituted olefins were prepared under base‐free, transition metal‐free, and oxidants‐free reaction conditions.     

Electro‐Oxidative S−H/S−H Cross‐Coupling with Hydrogen Evolution: Facile Access to Unsymmetrical Disulfides

Sulfur is an essential element because it exists widely in proteins. The disulfide bond is an important moiety in many different types of significant organic molecules. A new approach for oxidant‐ and catalyst‐free S?H/S?H cross‐coupling, with hydrogen evolution, to construct unsymmetrical disulfides was developed. Under the conditions of an undivided cell at room temperature, a series of unsymmetrical disulfides were prepared with up to 87 % yield from the direct coupling of an aryl mercaptan and alkyl mercaptan. Gram‐scale synthesis also highlights the synthetic utility of this electrochemical strategy.     

Cover Picture: Nickel‐Catalyzed Cross‐Electrophile Coupling of Aryl Bromides with Pyrimidin‐2‐yl Tosylates (Chin. J. Chem. 9/2017)

The cover picture shows a new protocol for the NiCl₂ ‐catalyzed cross‐electrophile coupling of aryl bromides with pyrimidin‐2‐yl tosylates to give the corresponding C2 ‐arylation pyrimidine derivatives. This study provides an improvement over previous methods by using pyrimidin‐2‐yl tosylates instead of halides as coupling partners that are stable and easily available. More details are discussed in the article by Wang et al. on page 1366–1370.

     

Cover Picture: Benzene Triimides: Facile Synthesis and Self‐Assembly Study (Chin. J. Chem. 7/2019)

The cover picture shows an efficient one‐pot condensation of maleimide derivatives in the presence of acetic acid and water to afford a series of benzene triimides (BTIs). The structure, physicochemical properties and electrochemistry behavior of BTIs were systematically investigated. Owing to the planar structure and unique electron‐deficient nature, BTIs can self‐assemble into different motifs. More details are discussed by Wang et al. on page 684–688.

     

Electrochemical Intramolecular C—H/O—H Cross‐Coupling of 2‐Arylbenzoic Acids

A synthetic protocol to lactones by electro‐oxidative induced C—H activation of 2‐arylbenzoic acids has been developed. By using Na₂SO₄ aqueous solution as a cheap and green supporting electrolyte, different 2‐arylbenzoic acids could provide the corresponding lactones in 30%—90% yields. This reaction could be conducted on a gram scale with a good efficiency as well as a high utility for natural product synthesis.     

Cover Picture: Understanding Zeolites Catalyzed Methanol‐to‐Olefins Conversion from Theoretical Calculations (Chin. J. Chem. 5/2018)

The cover picture shows the complexity of the reaction mechanism of zeolites catalyzed methanol‐to‐olefins (MTO) conversion. The MTO process plays a vital role in the production of light olefins from nonpetroleum resources. Despite of the successful industrialization of the MTO process in China, the detailed reaction mechanism is not yet well understood. The theoretical studies on the MTO hydrocarbon pool mechanism by the Group of Xie are summarized in the Chemistry Author Up Close by Xie et al. on page 381–386.

     

Cover Picture: Transition‐Metal‐Free Defluorosilylation of Fluoroalkenes with Silylboronates* (Chin. J. Chem. 10/2019)

The cover picture shows a simple, inexpensive and robust method on defluorosilylation of diverse fluoroalkenes with silylboronates in the presence of alkoxy base to directly synthesize various silylated fluoroalkenes. Density functional theory calculations revealed that transient silyl anion complex undergoes S_N2’ or S_N^V substitution, which is responsible for this base‐mediated defluorosilylation reaction, thus obviating the need for copper salts. More details are discussed in the article by Shi et al. on page 1009–1014.

     

Electrochemical Oxidative C—H Sulfenylation of Imidazopyridines with Hydrogen Evolution

Selective oxidative C—H sulfenylation of imidazopyridine heterocycles is achieved using an undivided electrolytic cell. The reaction avoids the use of stoichiometric amount of external chemical oxidant and produces hydrogen gas as the only byproduct. Both aryl and aliphatic thiols demonstrate good reactivity for C—S bond formation.     

Cover Picture: Highly Regioselective Sequential 1,1‐Dihydrosilylation of Terminal Aliphatic Alkynes with Primary Silanes (Chin. J. Chem. 5/2019)

The cover picture shows that sequential 1,1‐dihydrosilylation of terminal aliphatic alkynes with primary silanes enabled by one earth‐abundant cobalt catalyst has been developed. This protocol is operationally simple using readily available aliphatic alkynes, including simple acetylene and complex drug derivative, for efficient access to valuable gem‐bis(dihydrosilyl)alkanes in highly regioselective and atom‐economic manners. Corresponding asymmetric transformations are achieved with excellent enantioselectivities. More details are discussed in the article by Lu et al. on page 457–461.

     

Cover Picture: Engineering SpyCatcher Variants with Proteolytic Sites for Less‐Trace Ligation (Chin. J. Chem. 2/2019)

The cover picture shows an approach toward less‐trace SpyTag‐SpyCatcher ligation. A proteolytic recognition sequence has been engineered into the second loop of SpyCatcher to produce SpyCatcher^DDDDK variant. The reaction between SpyTag and SpyCatcher^DDDDK is highly efficient both in vivo and in vitro, producing a stable covalent complex. The complex can be further cleaved at the second loop by enterokinase, resulting in only a small scar after ligation. This protocol adds to the expanding toolbox of genetically‐encoded peptide‐protein chemistry for protein topology engineering. More details are discussed in the article by Zhang et al. on page 113–118.

     

Cover Picture: Catalytic Enantioselective Protonation of Monofluorinated Silyl Enol Ethers towards Chiral α‐Fluoroketones (Chin. J. Chem. 8/2019)

The cover picture shows a highly enantioselective organocatalytic protonation of monofluorinated silyl enol ethers to α‐secondary α‐fluoroketones using water as proton source. Notably, in the presence of D₂O and MeOD, the facile access of chiral α‐deuterated α‐fluoroketones in excellent enantioselectivity is achieved. More details are discussed by Zhou et al. on page 799–806.

     

Cover Picture: Facile Synthesis and in situ TEM Observation of Nanoporous Pd for Enhanced Catalytic Applications (Chin. J. Chem. 6/2019)

The cover picture shows facile photochemical synthesis, direct in situ TEM characterization, and effective catalytical applications of sponge‐like porous Pd nano particles. In situ liquid cell TEM observation not only confirms the actual existence of the sponge‐like Pd in a liquid solution, but also shows such Pd nanostructure is in a dynamic stable state, which is beneficial for the material exchange and the catalytic performance improvement. The expected catalytic activity improvement is supported by such as the 4‐nitrophenol reduction reactions, which is important both for the environment and the industry. More details are discussed in the article by Chen et al. on page 565–569.