Electrochemical Thiolation and Borylation of Arylazo Sulfones with Thiols and B₂pin₂

Abstract

An efficient electrochemical synthesis approach of various unsymmetrical thioethers and arylboronates has been developed. Bench stable arylazo sulfones were used as radical precursors for carbonheteroatom bond formation under electrochemical conditions. Moreover, the scalability of this approach was evaluated by performing the electrochemical thiolation and borylation of arylazo sulfones with thiols and B 2 pin 2 on a gram scale. This protocol not only avoided the use of stoichiometric oxidants, metal catalysts, activating agents and even added bases, but also exhibited favorable functional group tolerance.

Synthesis of Aryl Thiocyanates and Aryl Selenocyanates via Visible‐Light Activation of Arylazo Sulfones

“…À 0.9 V vs SCE, see also the redox diagram in Scheme 4b) [57] results in the formation of the corresponding radical anion 1 *À (Scheme 4a, path c), that, following N 2 and CH 3 SO 2 À releases an aryl radical (Ar * ). [58] Trapping of the latter intermediate by the Cu II -based complex II [59] and ensuing reductive elimination from III (paths d,e), affords the desired products 2-27 while restoring the starting catalyst I. The role of an aryl radical in the examined process has been further evidenced by the noxious effect of TEMPO on the reaction outcome (Table 1, run 9).…”

Desulfonylation via Radical Process: Recent Developments in Organic Synthesis

“…The peculiar arylazosulfones 137 - 1 which imparted both color and photoreactivity to molecules were found to be suitable substrates for arylation reactions under different photocatalytic conditions (Scheme A). Indeed, the CH 3 SO 2 N 2 moiety is dubbed as a dyed auxiliary group that allows the functionalized arylazosulfones to undergo, upon visible-light or UV-light irradiation, homolytic cleavage of the N–S bond and the loss of N 2 to deliver aryl radicals (Ar•) 137 - 4 or triplet aryl cations ( 3 Ar + ) 137 - 5 . − As such, photoactivated arylazosulfones 137 - 1 have been applied to a plethora of arylation protocols by Protti, Fagnoni, and others, including metal-free photoarylation of (hetero)­arenes (Scheme B, 1), radical arylation of isonitriles (Scheme B, 2), gold-promoted Suzuki synthesis of (hetero)­biaryls (Scheme B, 3), Mizoroki–Heck-type coupling with 1,1-diarylethylenes (Scheme B, 4), visible-light-driven synthesis of arylstannanes with hexamethylditin (Scheme B, 5), direct borylation with bis­(pinacolato)­diboron (B 2 pin 2 ) (Scheme B, 6), Arbuzov-like reaction with triorganophosphites (Scheme B, 7), trifluoromethylthiolation of S -trifluoromethyl arylsulfonothioates (Scheme B, 8), oxidative coupling with thiols under air (Scheme B, 9), thiolation with disulfides (Scheme B, 10), deutero deamination (Scheme B, 11), and electrochemical synthesis of unsymmetrical thioethers/selenides (Scheme B, 12) . Obviously, such bench-stable arylazo sulfones derived from anilines are great substitutes for aromatic diazonium salts.…”

Recent Advances in Arylations and Sulfonylations of Arylazo Sulfones

“…2019 年, 魏伟课题组 [28] 利用可见光诱导策 1.2 电催化下芳基偶氮砜的芳基化反应 近年来, 电催化作为一种绿色的合成手段逐渐在有 机合成化学中得到应用 [29] . 2020 年, 易文斌课题组 [30]…”