Synergistic effect of (RuCl 3 + IrCl 3 ) catalyzed oxidative conversion of rizatriptan benzoate to rizatriptan-N-oxide with N-haloamine: Exploration of scope, reaction behavior and kinetic data

Abstract Synergistic effect of (RuCl 3  + IrCl 3 ) as a binary mixture and alone have been investigated in the oxidation of rizatriptan benzoate (RTB) with chloramine-T (CAT) in aqueous HClO 4 medium at 303 K. The kinetic patterns were found to be different in all the three catalyzed reactions. Activation parameters have been calculated. Under the identical set of experimental conditions, the reaction rate reveals that all the three catalyzed reactions are about 25 to 75-fold faster than the uncatalyzed reactions. The observed catalytic reaction rate sequence follows the order: (RuCl 3  + IrCl 3 ) > IrCl 3  > RuCl 3 . The observed reactivity sequence may be attributed due to the fact that IrCl 3 –Carbon σ complexes are less strong, less localized and less covalent than RuCl 3 –Carbon complexes. Consequently, the present redox system is of great importance as the drug rizatriptan is transformed into rizatriptan-N-oxide On the basis of kinetic data, most plausible mechanisms were proposed.