Catalyst-free arylation of sulfonamides via visible light-mediated deamination

Abstract

A novel arylation of sulfonamides with boronic acids to afford various diaryl sulfones via visible light-mediated N–S bond cleavage other than typical transition-metal-catalyzed C(O)–N bond activation is described. This methodology...

Visible-Light-Mediated Late-Stage Sulfonylation of Boronic Acids via N–S Bond Activation of Sulfonamides

“…Recently, our group established the first visible light-mediated direct functionalization of N–S bond in sulfonamides, wherein a sulfonyl radical generated from acyl sulfonamides was the key step (Scheme b) . However, the two-step-prefunctionalization limited the utilization of this method in organic synthesis.…”

“…13 Recently, our group established the first visible lightmediated direct functionalization of N−S bond in sulfonamides, wherein a sulfonyl radical generated from acyl sulfonamides was the key step (Scheme 1b). 14 However, the two-step-prefunctionalization limited the utilization of this method in organic synthesis. In our effort to find a simple and practical pathway to generate sulfonyl radical from sulfonamides, sulfonyl imines drew our attention because of their easy preparation and wide utilization.…”

Photocatalytic Late-Stage Functionalization of Sulfonamides via Sulfonyl Radical Intermediates

“…Hence, harnessing sulfonyl radicals via this approach requires specific substituents, 21g thus limiting applicability as a late-stage functionalization tool. 22 To address this constraint, our design focused on using an aldehyde activator to form aldimine 1 , 23 facilitating a controlled fragmentation to the key sulfonyl radical intermediate. Although N -sulfonylimines can be viewed as inherently electron-deficient in nature, we speculated that single electron reduction could again result in significant quantities of the sulfinate anion.…”

“…The photochemical methods that do achieve these direct reductions present a quandary, resulting from the precarious nature of sulfonamide fragmentation, which potentially produces the sulfinate anion and not the required radical. Hence, harnessing sulfonyl radicals via this approach requires specific substituents, thus limiting applicability as a late-stage functionalization tool . To address this constraint, our design focused on using an aldehyde activator to form aldimine 1 , facilitating a controlled fragmentation to the key sulfonyl radical intermediate.…”

Visible-Light-Mediated Late-Stage Sulfonylation of Anilines with Sulfonamides

“…Previous exploration of N–S bond cleavage of sulfonamides mainly focused on desulfonylation to generate the corresponding amines . Recently, our group has revealed that acylated sulfonamides could act as sulfonylation reagents to undergo arylation with aryl boronic acids . Herein, we report a more general and operationally simple method for late-stage sulfonylation of anilines with either primary or secondary sulfonamides via visible-light irradiation (Scheme c).…”