Functional model oxygenations by nonheme iron complexes - Advances in Catalytic Activation of Dioxygen by Metal Complexes - page 193

be transformed to in the presence of olefins. 290 Non free radical process was
also proposed for aromatic hydroxylation by Fe 11 complexes
The oxygenation by this system, i.e. the oxygenated Fenton
chemistry, was summarized by Sawyer. 293,294
Barton et al. studied the mechanism of alkane functionalization of alkanes
(cyclohexane, adamantane, 3-ethylpentane, cyclododecane, etc. ) by experiments of
the catalytic oxygenation systems using and as

iron species and and Geletii and Shilov used and
for the oxidation of cyclohexane in the presence of pyridine 301 and compared the
ketone/alcohol ratio with the Gif system. 302 Barton et al. proposed the intermediate
formation of the iron-carbon species and a as the reactive
species 295-300 and formation of alkyl hydroperoxide as an intermediate. 303, 304 The
formation of an intermediate containing an Fe-C bond was further supported by the
efficient capture of the bond by iodine and iodide ion to give the corresponding alkyl
iodide 305 or by PhSeH. 306 Using completely regiospecific oxidation of
a methylene group of Binor S into a ketone was accomplished. 307 Non radical
mechanism in this system via an iron-alkyl species was suggested on the
bromination of saturated hydrocarbons. 308 Using and Barton et al.
indicated that the oxygen atoms in the alkyl hydroperoxide do not arise directly from
hydrogen peroxide but from formed in situ by the well-known iron(III)-
catalyzed decomposition of hydrogen peroxide. 309 The radical trapping experiment
with Tempo (2,2,6.6-tetramethyl-l-piperidinyloxy) also supported for the nonradical
nature of the first intermediate in the reaction. 309, 310 As an active species, formation
of a complex from an isolated complex was
proposed. 311 The carboxylate ligands such as picolinate are thought important for
the formation of a species as a key intermediate in the hydrocarbon
activation chemistry. 312 Important role of the pyridine bases in the Fe(III)
complexes for the efficient ketonization within the manifold 313 and of a
suitable carboxylic acid as ligand within the manifold was reported. 314 In
the studies on the role of pyridine, the use of 4- tert -butylpyridine was found to
permit the isolation of cyclohexanone and cyclohexanol by simple distillation. 315 As
an extended application of Gif systems, Barton et al. have developed the
carboxylation of saturated hydrocarbons by in

pyridine-acetic acid 316 or by These results in Gif Chemistry have

been reviewed by Barton. 318, 319
Trapper et al . 320 have reinvestigated a typical Gif system to lend support to
the proposition of a preponderant, carbon- and oxygen-centered radical pathway
rather than the nonradical pathway by Barton and Doller. 321 The monomeric