Metal‐Free Visible‐Light Synthesis of Arylsulfonyl Fluorides: Scope and Mechanism

Abstract

The first metal‐free procedure for the synthesis of arylsulfonyl fluorides is reported. Under organo‐photoredox conditions, aryl diazonium salts react with a readily available SO2 source (DABSO) to afford the desired product through simple nucleophilic fluorination. The reaction tolerates the presence of both electron‐rich and ‐poor aryls and demonstrated a broad functional group tolerance. To shed the light on the reaction mechanism, several experimental techniques were combined, including fluorescence, NMR, and EPR spectroscopy as well as DFT calculations.

Acridinium Salts and Cyanoarenes as Powerful Photocatalysts: Opportunities in Organic Synthesis

“…Cyanoarenes are very attractive organophotocatalysts that have shown very interesting reactivity in photoredox catalysis. [10] This is mainly due to the electrochemical properties of their excited states,w hich range from À0.7 to À1.7 V for the reduction potentials and + 2.0 Vand greater for their oxidation potentials. [10] Recently,1 ,2,3,5-tetrakis(carbazole-9-yl)-4,6-dicyanobenzene (4CzIPN, PC10)has emerged as one of the most useful catalysts in the series,w hich besides its reduction potential, exhibits al onger excited-state lifetime because of the presence of the carbazole groups.S uch as tructure mimics those found in transition-metal photocatalysts,w here photoexcitation leads to the transfer of an electron from the HOMO of the metal atom to the LUMO of the ligands.…”

“…[10] This is mainly due to the electrochemical properties of their excited states,w hich range from À0.7 to À1.7 V for the reduction potentials and + 2.0 Vand greater for their oxidation potentials. [10] Recently,1 ,2,3,5-tetrakis(carbazole-9-yl)-4,6-dicyanobenzene (4CzIPN, PC10)has emerged as one of the most useful catalysts in the series,w hich besides its reduction potential, exhibits al onger excited-state lifetime because of the presence of the carbazole groups.S uch as tructure mimics those found in transition-metal photocatalysts,w here photoexcitation leads to the transfer of an electron from the HOMO of the metal atom to the LUMO of the ligands. [42] To design new effective cyanoarene-based photocatalysts, the group of Zeitler investigated the effects of aromatic and halogen substitutions on the active core of three newly synthesized and five previously studied cyanoarenes.…”

“…Although seminal reviews have covered the field of organophotocatalysis,t he use of new variants of acridinium salts [8,9] and cyanoarenes, [10] which have recently emerged as powerful photocatalysts,has not been reported in detail from as ynthetic and mechanistic point of view.T his Minireview focuses on the recent developments in this area by discussing the reactivity of acridinium salts and cyanoarenes which have shown remarkable reactivity in photoredox catalysis.…”

Advances in photochemical and electrochemical incorporation of sulfur dioxide for the synthesis of value-added compounds

“…Just recently, the group of Tlili reported a light mediated synthesis of arylsulfonyl fluorides from arenediazonium salts and DABSO-catalyzed by an organic photoredox-catalyst (Scheme 14). 86 Interestingly, DABSO plays a twofold role in this reaction. On the one hand it serves as the SO 2 -source to trap the formed aryl radical.…”

Synthetic Routes to Arylsulfonyl Fluorides

“…Interestingly, the reaction in the presence of halogen substituents gave the desired products in synthetically useful yields (15e-15h). To some extent, heterocyclic com- Very recently, we demonstrated that aryl sulfonyl fluorides could be obtained under visible-light metal-free procedures by using cyanoarenes as organophotocatalysts [35][36][37][38][39][40]. Indeed, the association of diazonium salts with DABSO in the presence or not of an external fluoride source (KHF 2 ) allows access to a wide variety of arylsulfonyl fluorides with moderate to very good yields (Scheme 12).…”