Photoinduced Synthesis of Polycyclic γ‐Sultines by a Radical‐Polar Crossover Cyclization

Abstract

Described herein is a visible light‐mediated radical addition/SO2 insertion/anionic cyclization of benzo‐fused homoallylic tosylates, allowing access to a diverse array of otherwise challenging‐to‐access fluoromethylated polycyclic γ‐sultines with two adjacent tetrasubstituted carbon stereocenters in 49–95% yields, which can be further readily functionalized towards bulky two adjacent tetrasubstituted carbon‐containing benzo‐fused γ‐sultone and mercaptoalkanol. Sodium fluoroalkanesulfinates were utilized as bifunctionalization reagents for both fluoromethyl groups and SO2. The cyclization proceeds through a stepwise photoinduced radical addition followed by an intramolecular 5‐exo‐tet anionic substitution cyclization after SO2 insertion.

Advances in photoinduced radical–polar crossover cyclization (RPCC) of bifunctional alkenes

“…Finally, 119 undergoes a polar 5- exo-tet cyclization to furnish polycyclic sultine 120 (Scheme 14). 18…”

Synthesis of constrained bicycloalkanes through bibase-promoted brook rearrangement/radical-polar crossover cyclization

“…With this in mind and our ongoing interests in radical cyclization reactions, 8 we postulated that a bibase-promoted 1,2-silyl transfer of radical intermediate I, similar to 1,2-Brook rearrangement, from carbon to oxygen of the corresponding readily available α-silyl (hetero)cyclobutanol could produce an alkyl radical intermediate II under photoredox conditions. 9 The highly nucleophilic character of radical II will enable it to readily react with the olefin to form a new radical species.…”