Olefins iron oxidation chemistry

Recently, iron catalysis gained general importance. Its catalytic chemistry has been summarized ([2] recent reviews [3, 4]). Iron(II) and iron(III) salts have a long history in radical chemistry. The former are moderately active in atom-transfer reactions as well as initiators for the Fenton reaction with hydrogen peroxide or hydroperoxides (reviews [5-12]). Important applications of this principle are the Kharasch-Sosnovsky reaction (the allylic oxidation of olefins) [13], which often... 

Rare earth oxides are useful for partial oxidation of natural gas to ethane and ethylene. Samarium oxide doped with alkali metal halides is the most effective catalyst for producing predominantly ethylene. In syngas chemistry, addition of rare earths has proven to be useful to catalyst activity and selectivity. Formerly thorium oxide was used in the Fisher-Tropsch process. Recently ruthenium supported on rare earth oxides was found selective for lower olefin production. Also praseodymium-iron/alumina catalysts produce hydrocarbons in the middle distillate range. Further unusual catalytic properties have been found for lanthanide intermetallics like CeCo2, CeNi2, ThNis- Rare earth compounds (Ce, La) are effective promoters in alcohol synthesis, steam reforming of hydrocarbons, alcohol carbonylation and selective oxidation of olefins. 

The discovery of iron complexes that can catalyze olefin czs-dihydroxylation led Que and coworkers to explore the possibility of developing asymmetric dihydroxylation catalysts. Toward this end, the optically active variants of complexes 11 [(1R,2R)-BPMCN] and 14 [(1S,2S)- and (lP-2P)-6-Me2BPMCN] were synthesized [35]. In the oxidation of frans-2-heptene under conditions of limiting oxidant, 1R,2R-11 was foimd to catalyze the formation of only a minimal amount of diol with a slight enantiomeric excess (ee) of 29%. However, 1P-2P-14 and 1S,2S-14 favored the formation of diol (epoxide/diol = 1 3.5) with ees of 80%. These first examples of iron-catalyzed asymmetric ds-dihydroxylation demonstrate the possibility of developing iron-based asymmetric catalysts that may be used as alternatives to currently used osmium-based chemistry [45]. 

TT-cation radical complexes.In the reactions, oxoiron(IV) porphyrin rr-cation radicals of electron-rich porphyrins reacted fast with ROOH (i.e., catalase and peroxidase type of chemistry one-electron oxidation of ROOH) (Scheme 2, pathway A). On the other hand, oxoiron(IV) porphyrin rr-cation radicals of electron-deficient porphyrins reacted fast with olefins to yield epoxide products (i.e., cytochrome P450 type of chemistry oxygen atom transfer) (Scheme 2, pathway B). These results demonstrated that electron-deficient iron porphyrin complexes are better catalysts in hydrocarbon oxygenations by hydroperoxides, since these complexes can avoid the facile decomposition of oxoiron intermediates by ROOH (Scheme 2, pathway A). Indeed, highly electron-deficient iron(III) porphyrin complexes efficiently catalyze alkane hydroxylations by H2O2 in aprotic solvents. 

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