NIH shift in haemin–iodosylbenzene-mediated hydroxylations

Iron porphyrins-catalysed oxidation of α-alkyl substituted mono and dimethoxylated benzyl alcohols

“…The higher reactivity of FeTMPyPCl as compared to that of FeTSPPCl is likely due to the presence of stronger electron withdrawing substituents on the porphyrin ligand that not only increase the stability of the ironoxo complex in the oxidative reaction conditions but also increase the redox potential of the catalyst [22,23,39,40]. The observation that nuclear oxidation products are observed only in the oxidations catalysed by FeTMPyPCl and not in those catalysed by FeTSPPCl is also in accordance with the greater reactivity of the former catalyst.…”

“…Mesotetrakis(4-N-methylpyridyl)porphyrin iron (III) chloride (FeTMPyPCl) and meso-tetrakis(4-sulfonatophenyl) porphyrin iron (III) chloride (FeTSPPCl) have been used as catalysts in aqueous solution in combination with KHSO 5 as the oxygen atom donor. For the reactions in organic solvent (CH 2 Cl 2 ) the efficient catalyst Mesotetrakis(pentafluorophenyl)porphyrin iron (III) chloride (FeTPFPPCl) has been used [22][23][24][25][26] [27,28]. …”

Chemical model systems for drug‐metabolizing cytochrome‐P‐450‐dependent monooxygenases

“…The four reactions observed upon cytochrome-P-450-dependent oxidation of alkenes, i. e. the stereospecific epoxidation of the double bond [82,831, the hydroxylation of allylic C-H bonds [84], the minor formation of aldehydes RCH2CH0 from RCH = CH2 [82, 85, 861 and the transformation of the iron-porphyrin catalyst into an Nalkyl-porphyrin (see section 111-3), have also been reproduced by these model systems. Moreover, hydroxylation of aromatic hydrocarbons occurs with migration of the hydrogen (or deuterium) atom present at the hydroxylation site to the ortho position ("NIH shift") (72% retention of deuterium in pmethoxy-phenol formed by hydroxylation of (p-D)anisole [87]) (Fig. 7).…”

A manganese(III) porphyrin/rhodium(III) bipyridine/formate catalyst system for the reductive activation of molecular oxygen

“…Within 1 h of reaction time, the M nmTPP molecule was completely degraded. Even more robust por phyrins [22][23][24][25][26] such as the 'second-generation' ori/io-substituted chloro-porphyrins, and the penta-substituted chloro-and fluoro-porphyrins were either completely degraded during the course of the reaction or, in the case of M nmTpentaFPP, were unreactive. The reason for this fast oxidative degradation of the M nm por phyrin catalysts is most likely due to a rhodium -superoxo species that forms as a result of the interaction between the reduced rhodium bipyridyl complex and molecular oxygen.…”

“…We chose M nmTPP complexes that are modified with electron-withdrawing substituents at the ortho positions in the phenyl rings as well as porphyrins with completely substituted phenyl rings. These so-called 'second genera tion' porphyrins [22][23][24][25][26] are less susceptible to attack at the meso-positions due to both steric effects from the substituents and the electronwithdrawing effect which makes the m eso-posi tion less favorable to electrophilic degradation. The results of epoxidation reactions carried out with these catalysts are shown in Table 2.…”