Oxygen atom transfer iodosylbenzene

N—Fe(IV)Por complexes. Oxo iron(IV) porphyrin cation radical complexes, [O—Fe(IV)Por ], are important intermediates in oxygen atom transfer reactions. Compound I of the enzymes catalase and peroxidase have this formulation, as does the active intermediate in the catalytic cycle of cytochrome P Q. Similar intermediates are invoked in the extensively investigated hydroxylations and epoxidations of hydrocarbon substrates cataly2ed by iron porphyrins in the presence of such oxidizing agents as iodosylbenzene, NaOCl, peroxides, and air. 

Chromium(III) salen will form chromium(V) derivatives in much the same way as porphyrin complexes do. By reaction of iodosylbenzene with chromium(III)salen oxochromium(V) complexes are obtained (equation 74) which will effect oxygen atom transfer to phosphines and alkenes such as norbornene (equation 75) in stoichiometric and catalytic systems.1270 The... 

Porphyrin hgands also allow the preparation of Cr complexes. For example, reaction of [(TPP)CrCl] with iodosylbenzene provides [(TPP)Cr(0)Cl], a six-coordinate complex, which is stable in solution for several hours. Its reaction with alkenes involves oxygen atom transfer and yields alcohols and epoxides. Another Cr porphyrin complex is the nitride [(TPP)CrN]. A crystal-stmcture determination has confirmed the square pyramidal structure with a very short bond distance to the apical lutrido ligand (Cr N, 156.5 pm). 

Cr salen also reacts with iodosylbenzene and yields cationic Cr 0x0 complexes. These catalyze oxygen atom transfer to alkenes. ... 

Groves and coworkers [45] were the first to translate these results to a model system. They described the use of iron(III) meso-tetraphenylporphyrin (TPP) chloride in combination with iodosylbenzene for the epoxidation of olefins and hydroxylation of alkanes. Subsequently, chromium [46] and manganese [47] TPP complexes were shown to catalyze oxygen atom transfer from PhIO to an olefin or an alkane. 

Imidoiodanes and especially A-tosyliminoiodanes, ArINTs (Section 2.1.12.4), have found broad synthetic application as useful nitrene precursors in transition metal catalyzed aziridination of aUcenes and amidation of various organic substrates [584, 761]. Mansuy and coworkers in 1984 first reported the aziridination of alkenes with tosyliminoiodane PhINTs in the presence of iron- or manganese-porphyrins [762]. This reaction has a mechanism similar to the metal-catalyzed oxygen atom transfer reactions of iodosylbenzene (Section 3.1.20) and involves a metal-nitrene complex as the intermediate. 

Jacobsen applied manganese(III)-salen complexes for sulfide oxidation [57a]. It turned out that sodium hypochlorite was too reactive for the selective oxidation of sulfides but when employing iodosylbenzene as the oxygen atom transfer agent, no over-oxidation to sulfone was observed [106]. Disadvantages of iodosylbenzene are the poor solubility, low oxygen atom efficiency and high cost for practical application. 

Iodosylbenzene has been extensively utilized over the last few years for its ability to cleanly transfer oxene oxygen atoms to metals and possibly generate high-valent reactive metal-oxo species. PhIO has been successfully used instead of 02+NADPH in conjunction with cytochrome P-450 to hydroxylate alkanes,81 and has found a variety of interesting applications as a two-electron oxidant in the presence of first-row transition metal porphyrins. 

According to Ullrich [25] and Groves et aJ. [36-39], iodosylbenzene can serve as the source of 0-atoms in the catalytic epoxidation of olefins (and oxygenation of alkanes) in the presence of metalloporphyrin complexes. The reason for the considerable success of this oxygen source is that PhIO and the iodobenzene (Phi) formed upon 0-atom transfer are both quite stable to oxidation. So the otherwise unstable oxometal species generated from a metalloporphyrin and PhIO for example remains unchanged for extended periods of time, permitting spectroscopic characterization and/or selective reactions with oxidizable substrates. The 0-atom of PhIO is, however, activated for... 

Oxometal species have been variously invoked as intermediates in O-transfer reactions, especially in connection with single oxygen atom donors, such as iodosylbenzene, persulfate, N-oxides and peroxy compounds ". Oxocobalt(IV) was proposed as the active intermediate in the cobaloxime(II)-catalyzed oxidation of hydrazobenzene with 02 ... 

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