Electrooxidative Tandem Cyclization of Activated Alkynes with Sulfinic Acids To Access Sulfonated Indenones

Abstract

An electrooxidative direct arylsulfonlylation of ynones with sulfinic acids via a radical tandem cyclization strategy has been developed for the construction of sulfonated indenones under oxidant-free conditions. This method provides a simple and efficient approach to prepare various sulfonylindenones in good to excellent yields, demonstrating the tremendous prospect of utilizing electrocatalysis in oxidative coupling. Notably, this reaction could be easily scaled up with good efficiency.

Synthetic Organic Electrochemical Methods Since 2000: On the Verge of a Renaissance

“…A similar example in 2015 showcased that the same type of product could be accessed via the reaction of electrogenerated sulfonyl radicals and styrenes—NaI was used as the mediator, allowing the formation of a β -iodosulfone intermediate (Figure 3A, right). 78 Halide mediated oxidations of aryl sulfinates have also found applications in the preparations of oxindole (Figure 3B, top), 79 indenones (Figure 3B, bottom), 80 and sulfonamides 81 (Figure 3C) through sulfonyl radical initiated reactions.…”

Oxidative Sulfonylation of Multiple Carbon‐Carbon bonds with Sulfonyl Hydrazides, Sulfinic Acids and their Salts

“…Sulfonyl hydrazides were also used as sulfonylation reagents, and 2-sulfonylindanone was formed from chalcone and benzenesulfinic acid in a 50% yield under these conditions. [229] The reaction of biaryl ynones 413 with sodium sulfinates 414 under the action of Mn(OAc) 3 • 2H 2 O yielded spiro [5.5]trienones 415 (Scheme 183). The process ran under mild conditions through the formation of the sulfonyl radical, its addition to the triple bond, followed by 6-exo-trig cyclization.…”

“…This tandem transformation includes sulfonylation of alkynes, carbocyclization, dearomatization, and oxidation steps. Sulfonyl hydrazides were also used as sulfonylation reagents, and 2‐sulfonylindanone was formed from chalcone and benzenesulfinic acid in a 50% yield under these conditions [229] …”

Electrochemically Enabled Intramolecular and Intermolecular Annulations of Alkynes

“…In 2017, an environmentally friendly electrosynthesis strategy for preparing sulfonated indenones was proposed by Lei and coworkers. [12] In this work, a radical tandem cyclization was carried out to direct arylsulfonlylations of ynones with sulfinic acids under electrosynthesis conditions without the use of external oxidants. More importantly, the scope and limitations of this type of reaction were examined by investigating a series of substrates 1 and 2 with various substituents.…”