This electrochemical bioconjugation reaction provides an efficient modification of biomolecules with high chemo- and site-selectivity under mild conditions.

Direct cross-coupling between alkenes/R-H or alkenes/RXH is a dream reaction, especially without external oxidants. Inputting energy by photocatalysis and employing a cobalt catalyst as a two-electron acceptor, a direct C-H/X-H cross-coupling with H evolution has been achieved for C-O and C-N bond formation. A new radical alkenylation using alkene as the redox compound is presented. A wide range of aliphatic alcohols-even long chain alcohols-are tolerated well in this system, providing a new route to multi-substituted enol ether derivatives using simple alkenes. Additionally, this protocol can also be used for N-vinylazole synthesis. Mechanistic insights reveal that the cobalt catalyst oxidizes the photocatalyst to revive the photocatalytic cycle.

Electrochemical oxidative cross-coupling with hydrogen evolution has become an environmentally friendly and efficient way to form new bonds. Direct electrosynthesis by anodic oxidation has been developed for the synthesis of complex molecules. However, in some cases, redox catalysts were needed to avoid over-oxidation and to achieve better reaction selectivity. Recently, the use of iodine as a mediator to achieve indirect electrochemical reactions has drawn increasing attention. This review article gives an overview of the recent development of iodine mediated electrochemical oxidative coupling reactions.

In this work, a direct C-H activation of thiophenes was presented via an oxidation pathway under visible-light irradiation, in which the thiophene radical cation serves as the key intermediate. Various thiophenes and azoles could be transformed into the corresponding amination products well, and HO was the only byproduct which is environmentally benign. Our results showed that tert-butyl nitrite (TBN) served as the electron transfer mediator and O as the terminal oxidant to regenerate the photocatalyst DDQ and revive the photocatalytic cycle.

The dearomatization of arenes represents a powerful synthetic methodology to provide three-dimensional chemicals of high added value. Here we report a general and practical protocol for regioselective dearomative annulation of indole and benzofuran derivatives in an electrochemical way. Under undivided electrolytic conditions, a series of highly functionalized five to eight-membered heterocycle-2,3-fused indolines and dihydrobenzofurans, which are typically unattainable under thermal conditions, can be successfully accessed in high yield with excellent regio-and stereo-selectivity. This transformation can also tolerate a wide range of functional groups and achieve good efficiency in large-scale synthesis under oxidant-free conditions. In addition, cyclic voltammetry, electron paramagnetic resonance (EPR) and kinetic studies indicate that the dehydrogenative dearomatization annulations arise from the anodic oxidation of indole into indole radical cation, and this process is the ratedetermining step.

For application in drug discovery and biomedicine, it is crucial to develop new biocompatible methods to modify polypeptides. Herein, a visible-light-induced photoredox trifluoromethylation of tryptophan-containing peptides is reported. Under a mild, biocompatible, and straightforward condition, this strategy could incorporate the trifluoromethyl group into tryptophan residue with excellent chemo-and site-selectivity. The use of lower photocatalyst loading in 2 mol-% and cheap CF 3 SO 2 Na salt represents a great catalytic activity and [a] Methyl N-Acetyl-S-trifluoromethyl-L-cysteinate (2e): [15a] White solid. 1 H NMR (400 MHz, CDCl 3 ) δ = 6.84 (d, General Procedure for Trifluoromethylation of Di-, Tri-and Tetrapeptides: A solution of peptide 3 (0.20 mmol), CF 3 SO 2 Na (0.40 mmol) and Ir[dF(CF 3 )ppy] 2 (dtbbpy)PF 6 (2 mol-%) in CH 3 CN (2 mL) was stirred under air atmosphere and irradiated by 3 W blue LEDs for 4 h. When the reaction finished, the solvent was removed under reduced pressure by an aspirator. Then, the product was obtained by flash column chromatography on silica gel (dichloromethane/ethyl acetate) to afford corresponding trifluoromethylation of peptide 4. Ac-Trp(CF 3 )-Gly-OMe (4a): [15b] White solid. 1 H NMR (400 MHz, CD 3 CN) δ = 10.18 (s, 1H), 7.76 (d, J = 8.1 Hz, 1H), 7.42 (d, J = 8.2 Hz, ]DMSO) δ = 11.91 (s, 1H), 8.23 (d, J = 7.9 Hz, 1H), 8.05 (d, J = 8.9 Hz, 0.54H) & 7.99 (d, J = 9.0 Hz, 0.12H), 7.83 (d, J = 8.1 Hz, 0.82H) & 7.77 (d, J = 8.3 Hz, 0.15H), 7.41 (d, J = 8.2 Hz, 1H), 7.26 (t, J = 7.6 Hz, 1H), 7.11 (t, J = 7.5 Hz, 1H), 4.75-4.57 (m, 0.88H) & 4.57-4.47 (m, 0.15H), 4.42-4.25 (m, 1H), 3.61 (s, 0.44H) & 3.55 (s, 2.

With the importance of sulfur-containing organic molecules, developing methodologies toward C–S bond formation is a long-standing goal, and, to date, considerable progress has been made in this area. Recent electrochemical oxidative cross-coupling reactions for C–S bond formation allow the synthesis of sulfur-containing molecules from more effective synthetic routes with high atom economy under mild conditions. In this review, we highlight the vital progress in this novel research arena with an emphasis on the synthetic and mechanistic aspects of the organic electrochemistry reactions.1 Introduction2 Electrochemical Oxidative Sulfonylation for the Formation of C–S Bonds2.1 Applications of Sulfinic Acid Derivatives for the Formation of C–S Bonds2.2 Applications of Sulfonylhydrazide Derivatives for the Formation of C–S Bonds3 Electrochemical Oxidative Thiolation for the Formation of C–S Bonds3.1 Applications of Disulfide Derivatives for the Formation of C–S Bonds3.2 Applications of Thiophenol Derivatives for the Formation of C–S Bonds4 Electrochemical Oxidative Thiocyanation for the Formation of C–S Bonds5 Electrochemical Oxidative Cyclization for the Formation of C–S Bonds6 Conclusion

Dearomative annulation of indoles has emerged as a powerful tool for the preparation of polycyclic indoline‐based alkaloids. Compared with well‐established methods towards five‐membered‐ring‐fused indolines, the six‐membered‐ring‐fused indolines are rarely accessed under thermal conditions. Herein, a dearomative [4+2] annulation between different indoles is developed through an electrochemical pathway. This transformation offers a remarkably regio‐ and stereoselective route to highly functionalized pyrimido[5,4‐b]indoles under oxidant‐ and metal‐free conditions. Notably, this electrochemical approach maintains excellent functional‐group tolerance and can be extended as a modification tactic for pharmaceutical research. Preliminary mechanism studies indicate that the electrooxidation annulation proceeds through radical–radical cross‐coupling between an indole radical cation and an N‐centered radical generated in situ.