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-gamma-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.