The development of safe and energy efficient redox processes is key for a future sustainable organic chemistry and energy storage/vector applications. Molecular electrocatalysts have demonstrated their potential in the realm of CO 2 reduction, however, successful implementations for the reduction of other carbonyl groups remain sporadic. Building on the reversibility of hydrogenation and dehydrogenation of carbonyls and alcohols, an overview of current molecular electrocatalytic systems is presented. Key mechanistic concepts are emphasized to facilitate the link with more mature schemes in transfer hydrogenation, proton-and CO 2 -reduction. Thus, this work contributes to future catalyst generation development bridging fundamental aspects of electrochemical bond activation with molecular catalytic concepts in the context of societal challenges of today.
Diphosphine ligands are frequently used in palladium-catalyzed Suzuki-Miyaura (S-M) reactions. Despite their widespread application in both academic and industrial settings, their role in the B-to-Pd transmetalation has not been firmly established. We combined electrochemistry, NMR spectroscopy and DFT calculations to elucidate the role of dppf (1,1'-bis(diphenylphosphino)ferrocene) in this key elementary step of the S-M reaction. We observed that excess dppf inhibits transmetalation involving PhB(OH)2 and dppf-ligated arylpalladium(II) complexes, while an optimal [base]/[PhB(OH)2] ratio maximizes the concentration of a [Pd-O-B] key intermediate. In situ oxidation of dppf to the diphosphine monoxide dppfO can take place in the presence of base, leading to dppfO-ligated arylpalladium(II) complexes, which readily undergo transmetalation at room temperature. These findings suggest guidelines for the rational optimization of diphosphine-promoted S-M reactions.
Novel energy and atom efficiency processes will be keys to develop the sustainable chemical industry of the future. Electrification could play an important role, by allowing to fine-tune energy input...
Novel energy and atom efficiency processes will be keys to develop the sustainable chemical industry of the future. Electrification could play an important role, by allowing to fine-tune energy input and using the ideal redox agent: the electron. Here we demonstrate that a commercially available Milstein ruthenium cata-lyst (1) can be used to promote the electrochemical oxidation of ethanol to ethyl acetate and acetate, thus demonstrating the four electron oxidation under preparative conditions. Cyclic voltammetry and DFT-calculations are used to devise a possible catalytic cycle based on a thermal chemical step generating the key hydride intermediate. Successful electrification of Milstein-type catalysts opens pathway to use alcohols as renewable feedstock for the generation of esters and other key building blocks in organic chemistry, thus contributing to increase energy efficiency in organic redox chemistry.
The Cover Feature shows the cyclic interconversion of alcohols and carbonyls using electrons and protons. Molecular Electrocatalytic Alcohol Dehydrogenations (MEAD) and Carbonyl Hydrogenations (MECH) are crucial for atom and energy efficient processes for the chemical industry and energy applications. More information can be found in the Minireview by N. von Wolff et al.
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