Metalloporphyrin-catalysed epoxidation using hydrogen peroxide

The catalysis by S, 1 0, IS,20-tetrakis(pentafluorophenyl)-21H,23H-porphyrin iron(III) chloride (F20 TPPFeCl) of alkene epoxidation by H20 2 has been investigated. Extensive catalyst decomposition was observed during the reaction. A kinetics and product yield analysis has shown that this decomposition does not occur via either the oxoperferryl intermediate (F 20 TPP·+)F e =0 or the oxoferryl intermediate (F20 TPP)Fe IV =0, but appears to involve direct oxidation of the porphyrin in parallel with the catalytic epoxidation cycle. The catalytic epoxidation cycle involves formation of an oxoperferryl intermediate which reacts with cyclooctene to give epoxide and regenerate F20 TPPFe IlI . However, this reaction of the oxoperferryl intermediate with cyclooctene is in competition with reaction of the oxoperferryl intermediate with H20 2, which also regenerates F20 TPPFe III probably via the oxoferryl intermediate. In the absence of organic substrate, the decomposition by hydrogen peroxide is probably via the oxoperferryl and oxoferryl species. In order to investigate the effect of catalyst structure on epoxidation efficiency and catalyst stability, metalloporphyrins (S, 1 0, IS,20-tetrakis(p-hydroxyphenyl)-21H,23Hporphyrin iron(III) chloride (THPPFeCl), S,10,IS,20-tetraphenyl-21H,23H-porphyrin iron(III) chloride (TPPF eCl), S, 1 0, IS ,20-tetrakis(p-sulfonatophenyl)-21 H,23 Hporphyrin manganese(III) chloride (TSPPMnCl), S,10,IS,20-tetraphenyl-21H, 23Hporphyrin manganese(III) chloride (TPPMnCl), S, 1 0, IS,20-tetrakis(p-hydroxyphenyl) -21H,23H-porphyrin manganese(III) chloride (THPPMnCl) and S, 1 0, IS,20-tetrakis (pentafluorophenyl)-21H,23H-porphyrin iron(III) chloride (F20 TPPFeCl)) catalysed epoxidation reactions have been studied. Of these, THPPFeCl was synthesised from pyrrole and phydroxybenzaldehyde (via p-acetylbenzaldehyde), with the metal being inserted using refluxing FeCbAH20 in DMF. THPPMnCl was prepared by