Visible-light-promoted syntheses of β-keto sulfones from alkynes and sulfonylhydrazides

Abstract

A variety of functionalized β-keto sulfones were smoothly prepared through oxysulfonylation of commercially available alkynes with sulfonylhydrazides under the synergistic interactions of visible light irradiation, Ru(bpy)3Cl2 photocatalyst, oxygen, KI, and NaOAc basic additive under very mild reaction conditions.

(NH4)2S2O8‐Mediated Direct Oxysulfonyloxylation of Alkynes with Sulfonic Acids to Access α‐Sulfonyloxyketones

“…First, the decomposition of ammonium persulfate generates radical anion 4 and hydroxyl radical 5 with heat, which then undergoes hydrogen atom abstraction from p ‐toluenesulfonic acid (PTSA) 2 a to generate sulfonyloxy radical 6 . Subsequent radical addition of 6 to phenylacetylene 2 a affords vinyl radical 7 ,,, which is then trapped by a hydroxyl radical to form oxygenated intermediate 8 . Finally, tautomerization of enol 8 liberates α‐sulfonyloxyketone 3aa .…”

A Retrosynthetic Approach for Photocatalysis

“…An alternative procedure was developed by Huang and co‐workers starting from sulfonylhydrazines rather than sulfonyl chlorides . In addition to the previous method also electron‐rich arenes/electron‐donating substituents were tolerated.…”

Advances in Oxosulfonylation Reaction

“…In 2016, Cai and co-workers [60] reported a oxosulfonylation reaction of terminal aryl alkynes 19a with sulfonylhydrazides 19b in presence of 2 mol% of Ru (bpy) 3 Cl 2 as a photocatalyst under oxygen atmosphere and visible light (45 W household bulb) irradiation for 24 hours. NaOAc and KI were used as base and additive respectively.…”

“…In light of its extensive efficacies, numerous protocols of oxosulfonylation such as metal-catalyzed oxosulfonylation, [46][47][48][49][50][51][52][53][54][55] organophotocatalyzed oxosulfonylation, [32,[56][57][58] metal-based photocatalyzed oxosulfonylation, [59][60][61] catalyst free photo-induced oxosulfonylation [62][63][64] etc have been developed. Very recently, oxygen triggered oxosulfonylation methods [65][66][67][68][69][70][71][72] show great interest among synthetic organic chemists.…”