Visible light ande osin Yc atalyze the synthesis of vinyl sulfonesf rom aryl sulfinates and alkenes by ap hotoredox process.T he reactions cope is broad in aryl sulfinates and alkenes and the general and simple procedure providesametal-free alternative for the synthesis of synthetically valuable vinyl sulfones.

Alkyl- and aryl vinyl sulfones were obtained by eosin Y (EY)-mediated visible-light photooxidation of sulfinate salts and the reaction of the resulting S-centered radicals with alkenes. Optimized reaction conditions, the sulfinate and alkene scope, and X-ray structural analyses of several reaction products are provided. A detailed spectroscopic study explains the reaction mechanism, which proceeds through the EY radical cation as key intermediate oxidizing the sulfinate salts.

Visible light and eosin Y catalyze the direct arylation of simple arenes with fluorinated aryl bromides by a photoredox process. The reaction scope is broad in fluorinated compounds and arenes and the general and simple procedure provides a metal-free alternative for the synthesis of synthetically valuable polyfluorinated biaryl structures. The mild reaction conditions allow a selective reaction with the alkaloid brucine without protection of functional groups illustrating the potential of the process for late stage functionalization. Mechanistic investigations reveal the photoreduction of eosin Y via its triplet state by triethylamine and subsequent electron transfer from the eosin Y radical anion to the polyfluorinated bromoarene, which fragments into the polyfluorinated aryl radical and a bromide anion. A radical chain reaction mechanism was excluded by a quenching factor analysis.

Helquat dyes are the first helicene-like cationic styryl dyes obtained as separate enantiomers. Their remarkable chiroptical properties are due to the unique combination of a cationic hemicyanine chromophore and a helicene-like motif. The magnitude of the ECD response and the pH switching along with their positioning in the visible region are unprecedented among helicenoids.