Electrochemical Oxidative Cross‐Coupling of Enaminones and Thiophenols to Construct C−S Bonds

Abstract

An electrochemical oxidative C(sp 2)-H sulfuration has been developed. Various enaminones and thiophenols were compatible, generating the desired alkenyl sulfur compounds in up to 87 % yield. This transformation proceeded smoothly under mild reaction conditions without external oxidant and transition-metal catalyst. Remarkably, thiophenols selectively coupled with enamines when substrates had other alkenyl groups. In addition, the desired products could be further transformed into a series of αsulfur isoxazoles, which are a kind of useful heterocycles in materials and bioactive molecules.

Photochemical and Electrochemical Applications of Proton-Coupled Electron Transfer in Organic Synthesis

“…Following this, in 2020, Lei, Lu, Gao, and co-workers demonstrated the α-sulfenylation of N,N -dimethylenaminone derivatives under similar electrochemical conditions ( Scheme 237 ). 629 Under constant current electrolysis of enamine and thiol substrates in an undivided cell (C rod anode, Pt plate cathode, n -Bu 4 N + BF 4 – supporting electrolyte in MeCN) at ambient temperature, 28 examples of this C(sp 2 )–H oxidative cross-coupling were disclosed in yields of 24–87%. The scope includes a range of aryl thiols and aryl enaminones.…”

Tf2O‐Mediated Regioselective C(sp2)−H Sulfenylation of Enaminones Using Methyl Sulfoxides as Sulfur Sources

“…Wan and his colleagues developed KIO 3 ‐catalyzed aerobic cross‐coupling reactions for the α‐sulfenylation of enaminones by using thiophenol as sulfur source (Scheme 1, eq 2) [10b] . Inspired by this work, Loh, [10c] Prabhu, [10d] Maddani [10e] and Lei [10f] used the similar strategy to realize the formation of carbon‐sulfur bonds by the oxidative cross‐coupling of enaminones with thiophenols, respectively (Scheme 1, eq 3–6). Currently, Wan and Li went on to report the construction of C(sp 2 )−S bonds by KIO 3 /TEMPO oxidation, [10g] molecular iodine oxidation [10h] and electrochemical oxidation [10i] of enaminone derivatives.…”

Green and Practical Synthesis of Thioenamines and Chromones via Iodine-Catalyzed Cross-Dehydrogenation Coupling Reaction

“…Simultaneously, Deng developed a multi-component synthesis of thioenamines starting from disulfides, amines, and alkynes mediated by iodine (Scheme , C). Recently, electrochemistry also played a role in the synthesis of thioenamines, and the related examples were reported by Lei in 2020 and Yu in 2021 (Scheme , D).…”