Electrochemically Promoted Bifunctionalization of Alkynes for the Synthesis of β‐Keto Sulfones

Abstract

An electrochemical oxidative difunctionalization of internal and terminal alkynes with sulfonyl hydrazides for the synthesis of β-keto sulfones has been achieved. The reaction involves the addition of sulfonyl radicals to alkynes, and the resulting alkenyl radicals are oxidized to alkenyl cations, which are then nucleophilically attacked by H 2 O, followed by tautomerization to form β-keto sulfones. The method is green and sustainable as it is catalyst-free, oxidant-free, and additive-free. The new CÀ O and CÀ S bonds can be constructed in one-pot to directly access β-keto sulfone derivatives.

Electrochemical difunctionalization of alkenes and alkynes for the synthesis of organochalcogens involving C–S/Se bond formation

“…In 2021, He and co-workers explored a green and sustainable electrochemical oxidative difunctionalization of alkynes with sulfonyl hydrazides for the synthesis of β-keto sulfones (Scheme 13). 30 In general, new C–O bonds and C–S bonds were formed with H 2 O as nucleophile. This process does not require any oxidizing agent, and is not only suitable for terminal alkynes, but also for internal alkynes.…”

The Application of Sulfonyl Hydrazides in Electrosynthesis: A Review of Recent Studies

“…Meanwhile, an approach to the electrochemical oxidative selenosulfonylation of alkynes was also involved in the same report by Xu et al (Scheme 9). 61 In this protocol, sulfonyl hydrazides (62), alkynes (63), and diphenyl diselenide (64) were treated in an undivided cell charging a graphite anode and a Pt cathode, using nBu 4 NBF 4 as a supporting electrolyte. The reaction had a broad scope of substrates, and most of the selected alkynes and sulfonyl hydrazides with aryl groups bearing either electron-donating or electron-withdrawing substituents were tolerated.…”

“… 62 In 2021, He and co-workers developed an oxysulfonylation of alkynes using sulfonyl hydrazides ( 42 ) and alkynes ( 43 ) ( Scheme 7 ). 64 …”

Synthesis of β‐Keto Sulfones by Oxy‐Sulfonylation of Alkynes in HFIP

“…Apart from the alkynes, dioxygen‐triggered oxo‐sulfonylation of hydrazones was also explored by Hajra and co‐workers offering N‐acylsulfonamides in 2020 (Scheme 2e) [6e] . Very recently, He and Guan reported a electrochemical oxysulfonylation process employing sulfonyl hydrazides (Scheme 2f) [6f] . Despite these great successes, the use of excess amounts of sulfonyl reagent, additional acid, base or catalyst in these processes generated unwanted waste.…”