Generation of Sulfonyl Radicals from Aryldiazonium Tetrafluoroborates and Sulfur Dioxide: The Synthesis of 3‐Sulfonated Coumarins

Abstract

A catalyst-free approach for the generation of sulfonyl radicals from aryldiazonium tetrafluoroborates in the presence of DABCO⋅(SO2 )2 is realized. The combination of aryldiazonium tetrafluoroborates, DABCO⋅(SO2 )2 , and aryl propiolates affords 3-sulfonated coumarins in good to excellent yields. This tandem reaction process involves radical addition, spirocyclization, and 1,2-migration of esters. Additionally, the in situ diazotization of a number of anilines allows the directional synthesis of desired 3-sulfonated coumarins in a one-pot, two-step process.

Sulfonylation of Benzylic C−H Bonds through the Reaction of Aryl(o‐tolyl)methanones with Sulfonyl Hydrazides or Sulfonyl Chlorides

“…1 H NMR (400 MHz, CDCl 3 ): δ =7.47 (d, J= 8.2 Hz, 2 H), 7.36 (m, 2 H), 7.30 (t, J= 7.4 Hz, 4 H), 7.20 (d, J= 7.4 Hz, 2 H), 7.15 (d, J= 8.2 Hz, 2 H), 7.10 (d, J= 7.1 Hz, 2 H), 6.99 (s, 1 H), 2.38 ppm (s, 3 H); 13 C NMR (100 MHz, CDCl 3 ): δ =154.9, 144.0, 139.4, 138.8, 135.8, 130.5, 123.0, 129.6, 129.2, 128.8, 128.4, 128.0, 21.8 ppm. HRMS data could be found in previous report.…”

Generation of Sulfonyl Radicals from Aryldiazonium Tetrafluoroborates and Sulfur Dioxide: The Synthesis of 3‐Sulfonated Coumarins

“…Reactions of the phenyl propiolates 1 bearing benzyl, methoxyl, and fluoro substituents in the para-position of the phenoxy ring with DABCO·(SO 2 ) 2 and 2 a occurred efficiently, thus resulting in the desired products 3 s-u in good yields, [19] while a lower yield of 40 % was obtained for the substrate with much stronger electron-withdrawing group (acetyl). Reactions of the phenyl propiolates 1 bearing benzyl, methoxyl, and fluoro substituents in the para-position of the phenoxy ring with DABCO·(SO 2 ) 2 and 2 a occurred efficiently, thus resulting in the desired products 3 s-u in good yields, [19] while a lower yield of 40 % was obtained for the substrate with much stronger electron-withdrawing group (acetyl).…”

Vicinal Difunctionalization of Alkenes through a Multicomponent Reaction with the Insertion of Sulfur Dioxide

“…For oxysulfonylation of alkenes, the process mostly included as ulfonyl radical intermediate, which would undergo addition to alkenes. [7] The experimental ease avoidingt he handlingp roblem of its gaseous form and the efficiency of insertiono fs ulfur dioxide make the methods attractive for the generation of diverses ulfonyl compounds. For example, Lei and co-workers reported at hree-component reaction of alkenes, sulfinic acids and oxygen in ar adical process, giving various b-hydroxysulfones in good yields.…”