Metal‐Free, Multicomponent Anti‐Markovnikov Hydroarylsulfonylation and Alkoxyarylsulfonylation of Vinyl Arenes

Abstract

A unified strategy for the hydro‐arylsulfonylation of vinyl arenes has been developed under catalyst, additive‐free conditions at room temperature from the corresponding aryldiazonium salts, DABSO (DABCO ⋅ 2SO2), and thiophenol as hydrogen atom transfer (HAT) reagent. Mechanistically, an incipient arylsulfonyl radical is generated from the corresponding aryl diazonium salts and DABSO which undergoes anti‐Markovnikov addition to styrenes followed by hydrogen atom transfer from thiophenol. Interestingly, this multi‐component reaction is highly chemoselective suppressing deleterious thiosulfonylation and thiol‐ene reactions. Tuning the reaction conditions, a four‐component difunctionalization with alkoxy group has been achieved using 1,4‐dicyanobenzene as an oxidant. Furthermore, base‐promoted elimination to form vinyl sulfone has been also examined. The practicability of this present reaction has been demonstrated by the ex situ generation of sulfur dioxide in an H‐type reaction vessel and subsequent hydro‐ and alkoxyarylsulfonylation in good to moderate yields. The hydroarylsulfonylation reaction is scalable and applied to a metal‐free synthesis of the key intermediate for an anti‐migraine drug Eletriptan.

DABSO as a SO2 gas surrogate in the synthesis of organic structures

“…Moreover, by employing 1,4-dicyanobenzene (DCB) as the oxidant, 4-alkoxy styrenes 53 is transformed to sulfones 55 via alkoxylation of cationic intermediate 54 (Scheme 28). 71 The synthesis of α-sulfonyl ketoximes was developed through a four-component reaction of t-butyl nitrite 56, DABSO, anilines 57, and styrene derivatives 58 (Scheme 29). The progress of this reaction relies on the salicylic acid-catalyzed formation of radical 59 through the conversion of aniline to diazonium, the removal of a nitrogen molecule, and its treatment with DABSO.…”

DABSO – A Reagent to Revolutionize Organosulfur Chemistry

“…Following these studies, the combination of aryldiazonium salts and DABSO has been extensively used for the preparation of sulfone products. Sulfonyl radical addition to alkenes or alkynes gives -sulfonyl radicals, which can then be quenched by hydrogen atom transfer (HAT), 65 or by reaction with in situ generated radicals (Scheme 23, A). 66 A SET step can be used to prepare a carbocation intermediate, from which deprotonation gives alkene or alkyne products (Scheme 23, B).…”

Aryldiazonium Salts and DABSO: A Versatile Combination for Three‐Component Sulfonylative Cross‐Coupling Reactions

“…(E)-1-methoxy-4-(2-((4-methoxyphenyl)sulfonyl)vinyl)benzene, (4 i). [11] Column chromatography (SiO 2 , eluting with 80 : 20 hexane/ ethyl acetate) afforded the desired product as a white solid (51.1 mg, 84%). 1 H NMR (400 MHz, CDCl 3 ): δ 7.84 (d, J = 9.2 Hz, 2H), 7.55 (d, J = 15.2 Hz, 1H), 7.39 (d, J = 8.8 Hz, 2H), 6.97 (d, J = 9.2 Hz, 2H), 6.86 (d, J = 9.2 Hz, 2H), 6.68 (d, J = 15.6 Hz, 1H), 3.84 (s, 3H), 3.80 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ): δ 163.…”

“…Owing to the versatile utility of vinyl sulfones in organic synthesis, covalent modification of biomolecules, polymers and ubiquitous presence in drug molecules, we further intended to synthesize arylvinylsulfone engaging vinyl boronic acid in this cross‐coupling manifold [10] . Previously, we obtained vinyl sulfone from aryldiazonium salts, DABSO, and styrenes under oxidative/elimination pathway in moderate yields [11] . Although only electron‐rich styrenes were capable of this transformation in presence of an oxidant 1,4‐dicyanobenzene.…”

“…[10] Previously, we obtained vinyl sulfone from aryldiazonium salts, DABSO, and styrenes under oxidative/elimination pathway in moderate yields. [11] Although only electron-rich styrenes were capable of this transformation in presence of an oxidant 1,4-dicyanobenzene. The Wu group and the Feng group reported the synthesis of vinylsulfones from styrenes under copper catalysis and TBAI/TBHP conditions respectively.…”