Recent advances in organic electrosynthesis using heterogeneous catalysts modified electrodes

Organic electrosynthesis as an emerging green and advantageous alternative to traditional synthetic methods has achieved remarkable progress in recent years because sustainable electricity can be employed as traceless redox agents. To surmount the over-oxidation/reduction issues of direct electrolysis,mediated or indirect electrochemical processes are attaining remarkable significance and promoting the selectivity of products. Molecular electrocatalysts, benefiting from the easily electronic and steric modulation, suffers from readily degradation issue in most cases. Remarkably, heterogeneous catalysts have drawn more attention due to their high activity, stability, and recyclability. Hence, in this review, the most recent growth of heterogeneous catalysts modified electrodes for organic electrosynthesis were summarized, highlighting structural optimization and electrochemical performance of these materials as well as reaction mechanism. Furthermore, key challenges and future directions in this area were also discussed.

Recent progress in cathodic reduction-enabled organic electrosynthesis: Trends, challenges, and opportunities

Compared with general redox chemistry,electrochemistry using the electron as a potent,controllable,yet traceless alternative to chemical oxidants/reductants usually offers more sustainable options for achieving selective organic synthesis.With its environmentally benign features gradually being uncovered and studied,organic electrosynthesis is currently undergoing a revival and becoming a rapidly growing area within the synthetic community.Among the electrochemical transformations,the anodically enabled ones have been far more extensively exploited than those driven by cathodic reduction,although both approaches are conceptually attractive.To stimulate the development of cathodically enabled organic reactions,this review summarizes the recently developed reductive electrosynthetic protocols,discussing and highlighting reaction features,substrate scopes,applications,and plausible mechanisms to reveal the recent trends in this area.Herein,cathodic reduction-enabled preparative organic transformations are categorized into four types:reduction of(1)unsaturated hydrocarbons,(2)heteroatom-containing carbon-based unsaturated systems,(3)saturated C-hetero or C–C polar/strained bonds,and(4)hetero-hetero linkages.Apart from net electroreductive reactions,a few examples of reductive photo-electrosynthesis as well as paired electrolysis are also introduced,which offer opportunities to overcome certain limitations and improve synthetic versatility.The electrochemically driven,transition metal-catalyzed reductive cross-couplings that have been comprehensively discussed in several other recent reviews are not included here.

SOLID-STATE ELECTROCHROMIC DISPLAY

The catalyzation of CoTPP for electrocarboxylation of alkyl halides, alkenes and ketones with CO;are studied. The electrocarboxylation of these organic compounds with CO;in the presenec of catalyst can occur at more positive potential than that of no catalyst. The products of electrocarboxylation were identified by UV, IR and GC-MS. The electrocarboxylation mechanisms of different organic compounds are discussed.

Electrochemically mediated three-component synthesis of isothioureas using thiols as sulfur source

The simultaneous binding/dissociation of multiple bonds in a one-pot manner by multicomponent reactions provide an important approach for developing novel and sustainable pathway in the drug discovery process.Herein we develop an electrocatalytic three-component reaction to construct multifunctional and valuable isothiourea compounds,which uses thiols,isocyanides and amines as substrates.Compared with the previous work,the organic electrosynthesis technique can avoid the requirement of heavy metal catalysts and stoichiometric oxidants.In addition,using thiol as a substrate to participate in the three-component reaction broadens the source of sulfur,which can also construct more abundant isothiourea derivatives.

Electrophotocatalytic Si-H Activation Governed by Polarity-Matching Effects

Trialkylsilanes are important building blocks in organic synthesis;however,their widespread use in redox chemistry is limited by their high oxidation potentials and comparably high bond dissociation energies(BDEs)of Si-H and α-Si-C-H bonds(>92 kcal mol^(−1)).Herein,we report a new strategy for Si-H bond homolysis enabled by the synergistic combination of electrooxidation,photoinduced ligand-to-metal charge transfer(LMCT),and radical-mediated hydrogen atom transfer(HAT).Governed by the polarity-matching effect,the HAT to electrophilic MeO·or[Cl-OHCH_(3)]·from the more hydridic Si-H instead of a C-H bond allows the selective generation of silyl radicals.This electrophotocatalytic protocol provides rapid access to Si-functionalized benzimidazo-fused isoquinolinones with broad functional-group compatibility.Mechanistic studies have shown that n-Bu_(4)NCl is essential to the electrooxidation of CeCl_(3) to form the Ce(Ⅳ)species.