Emergence of a novel catalytic radical reaction: Titanocene-catalyzed reductive opening of epoxides

The preparatively important catalytic opening of epoxides to beta-titanoxy radicals via single-electron transfer (SET) is described. These radicals ca n be reduced to alcohols or participate in C-C bond-forming reactions. A ke y step in the catalytic cycle is the conceptually novel protonation of tita nium-oxygen and -carbon bonds. Our method combines the advantages of radica l reactions, e.g., high functional group tolerance and stability of radical s under protic conditions, with the ability of organometallic complexes to determine the course of transformations in reagent-controlled reactions.