1,1,1,3,3,3‐Hexafluoro‐2‐propanol

KuQuinone as a Highly Stable and Reusable Organic Photocatalyst in Selective Oxidation of Thioethers to Sulfoxides

“…As a matter of fact, thioanisole conversion is significantly reduced when performing reactions in the presence of radical cation scavengers (like 1,4-dimethoxybenzene) and radical quenchers, such as TEMPO (Figure S4). Such experiments still indicate a radical mechanism that may occur through the formation of thioether radical cation (as in Scheme , pathway b), which is stabilized in HFIP. , However, superoxide radical anion is possibly not involved in the process, since O 2 •– scavengers did not affect the reaction. Such result likely indicates a different electron transfer mechanism, in which molecular oxygen is directly involved (Scheme ).…”

“…41 Results show that in HFIP, thioanisole full conversion to methyl phenyl sulfoxide was successfully obtained in just 40 min, with no sulfone traces (Table 1, entry 5). The remarkable selectivity of the process is probably related to the strong hydrogen bond donor ability of HFIP: 56,57 indeed, solvent coordination to sulfoxide likely prevents the further oxidation to sulfones via electronic effects. Importantly, HFIP is a nonflammable low boiling solvent, and thus it can be easily removed from the reaction mixture by distillation and recycled.…”

“…Such experiments still indicate a radical mechanism that may occur through the formation of thioether radical cation (as in Scheme 2, pathway b), which is stabilized in HFIP. 56,57 However, superoxide radical anion is possibly not involved in the process, since O 2 •− scavengers did not affect the reaction. Such result likely indicates a different electron transfer mechanism, in which molecular oxygen is directly involved (Scheme 3).…”