Successive Waste as Reagent: Two More Steps Forward in a Pinnick Oxidation

The successful development of the classical Pinnick oxidation into a new and promising oxidative lactonization reaction is reported. Chiral 3-oxindolepropionic aldehydes, Michael adducts of 3-olefinic oxindoles with aliphatic aldehydes, are directly converted to spirocyclic oxindole-γ-lactones solely by sodium chlorite via a tandem Pinnick oxidation/chlorination/substitution sequence. This reaction uses waste ClO– generated in the initial Pinnick oxidation as an ecofriendly halogenating agent for the subsequent chlorination, and then it utilizes the byproduct OH– formed in the chlorination to facilitate the final internal substitution.