Anodic oxidation in a solution containing a variety of olefins and a small amount of Mn (OAc) 2· 4H2O brought about Mn+ 3-mediated carbon—carbon bond formation, such as efficient carboxymethylation of styrene derivatives to the corresponding γ-aryl-γ-butyrolactones, and selective coupling of active methylene compounds with non-activated monoolefins, unconjugated dienes or 5-arylpent-1-enes.