Transition‐metal‐free Photo‐induced Cascade Sulfonylation/Addition/Cyclization of 3‐Arylethynyl‐[1,1′‐biphenyl]‐2‐carbonitriles with Aryldiazonium Tetrafluoroborates via the Insertion of Sulfur Dioxide

Abstract

A transition-metal-free photo-induced cascade sulfonylation/addition/cyclization of 3-arylethynyl-[1,1'-biphenyl]-2-carbonitriles with Na 2 S 2 O 5 and aryldiazonium tetrafluoroborates for the construction of 4-sulfonated cyclopenta[gh] phenanthridines is developed. This reaction involves a radical pathway and goes through a sequence of phenyl radical formation, sulfur dioxide insertion, sulfonyl radical addition, iminyl radical formation, and cyclization. The methodology displays mild conditions, a broad substrate scope and does not require any external oxidants.

Multicomponent reactions and photo/electrochemistry join forces: atom economy meets energy efficiency

“…Recently, a similar strategy was employed by Zhou et al to form polycyclic scaffolds that hold relevant importance in photochemistry, polymer chemistry, materials, and many other applications. 276 In light of their utility, the authors sought to develop a straightforward strategy to form 4-sulfonated cyclopenta[gh]phenanthridines under mild conditions, exploiting, in this case, the reactivity of alkynes as radical traps. Following a mechanism similar to He's work (Scheme 141), the photocatalyst (eosin Y) is first responsible for the generation of an aryl radical from the arendiazonium salt, which subsequently forms the desired arylsulfonyl radical through the reaction with sodium metabisulfite.…”

Recent Advances in the Catalytic Synthesis of Arylsulfonyl Compounds

“…In 2020, a photoinduced domino synthesis of 4-sulfonated cyclopenta­[ g , h ]­phenanthridines was developed through 3-arylethynyl­[1,1′-biphenyl]-2-carbonitriles with the insertion of SO 2 from Na 2 S 2 O 5 combined with aryldiazonium 3-arylethynyl­[1,1′-biphenyl]-2-carbonitriles (Scheme ). This domino reaction involves a radical pathway and follows a sulfonylation and five-membered-ring cyclization with the formation of an iminyl radical, which involves intramolecular addition to the aryl ring and forms another six-membered ring to yield the targeted moiety.…”

The synthesis of anticancer sulfonated indolo[2,1-a]isoquinoline and benzimidazo[2,1-a]isoquinolin-6(5H)-ones derivatives via a free radical cascade pathway

“…6 Hence, the development of novel, versatile strategies to construct different useful skeletons bearing sulfonyl groups would be highly significant. 7 Recently, the studies revealed that heterocyclic molecules containing sulfonyl-substituents exhibit unique bioactivities and chemical properties, and widely adopted in drug design. 6 d ,8 Among the various sulfonate reagents, the incorporation of sulfonyl radicals, which generated in situ from thiosulfonates, have been disclosed in the literature.…”