Ruthenium catalyzed selective oxidation of aryl thiophenes using hydrogen peroxide

Highly selective catalytic oxidations of (sterically hindered) aryl thiophenes using stoichiometric amounts of hydrogen peroxide (35% in water)
and cis-Ru(II) bis(substituted phenanthroline) complexes (as low as 0.1%) were carried out in acetonitrile at 75 oC, affording the corresponding
sulfones in high yields and selectivities. The products were recovered quantitatively by simple crystallization from the reaction mixture.