Photoredox Catalytic Pentafluorosulfanylative Domino Cyclization of α-Substituted Alkenes to Oxaheterocycles by Using SF6

Abstract

Virtually inert sulfur hexafluoride becomes a precious pentafluorosulfanylation agent, if properly activated by photoredox catalysis, to access α-fluoro and α-alkoxy SF5-compounds. This advanced protocol converts SF6 in the presence of alkynols as bifunctional C−C- and C−O-bond forming reagents directly into pentafluorosulfanylated oxygen-containing heterocycles in a single step from α-substituted alkenes. The proposed mechanism is supported by theoretical calculations and gives insights not only in the pentafluorosulfanylation step but also into formation of the carbon-carbon bond and is in full agreement with Baldwin's cyclization rules. The key step is a radical type 5-, 6- respectively 7-exo-dig-cyclization. The synthesized oxaheterocycles cannot be simply prepared by other synthetic methods, show a high level of structural complexity and significantly expand the scope of pentafluorosulfanylated building blocks valuable for medicinal and material chemistry.