Fluorous biphasic catalytic oxidation of sulfides by molecular oxygen/2,2-dimethylpropanal

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 biphasic system. The addition of ve ry small amounts of a C-11-tetraarylporphyrin (Co-4) led to increased subst rate conversions (67-100%). Sulfoxide was generally obtained as the main pr oduct, together with variable quantit ies of sulfone (0-100%), depending on the nature of the substrate. A perfluoroalkyl-substituted Co-11-phthalocya nine (Co-6) proved to be less efficient with regard to substrate conversion (40-78%), but afforded sulfoxides selectively. Although the mechanism has not been investigated in detail, the reaction probably proceeds through a f ree-radical oxidative process, initiated by the Co-11 complexes. The attemp ts at recycling the catalysts through phase separation were partly ineffect ual owing to their instability under the reaction conditions, which is more pronounced in the case of Co-6.