The use of perfluoroalkyl-substituted cobalt complexes as catalysts for the oxidation of alkyl aryl sulfides with molecular oxygen/2,2-dimethypropanal has been studied in a fluorous organic biphasicsystem. The addition of very small amounts of a CoII−tetraarylporphyrin (Co-4) led to increased substrate conversions (67−100%). Sulfoxide was generally obtained as the main product, together with variable