Functional model oxygenations by nonheme iron complexes - Advances in Catalytic Activation of Dioxygen by Metal Complexes - page 186

On the other hand, MacFaul et al. have demonstrated that the hydroxylation
of cycloalkanes by involves freely diffusing
cycloalkyl radical (Scheme 4). 222 The radical mechanism proposed by MacFaul et
al.

220, 222

was also applied to selective oxidation of cyclohexane to cyclohexanol
catalyzed by a diiron(II) complex and TBHP (L =
1,4,10,13-tetrakis(2-pyridyl)methyl-1,4,10,13-tetraaz-7,16-dioxacyclo-octadecane).
223

Hydrogen peroxide is no doubt a useful oxygen donor and decomposes to
water, but it is usually treated as an aqueous reagent. Thus the effect of water
should be considered. Functionalization of hydrocarbons with
and using as the
oxidant, was studied by Fish et al.. 224 The results obtained in the oxidation of
cyclohexane was consistent with a free-radical chain mechanism in which an
initially formed cyclohexyl radical is trapped by oxygen gas to give a cyclohexyl
peroxy radical, which abstracts a hydrogen atom to give cyclohexyl peroxide. The
selective abstraction of the tertiary hydrogen of adamantane was shown by the high
values. Participation of hydroxyl radicals in the oxidation of toluene was also
suggested. Similar reactivity was observed by the complex
It is also shown that aromatic hydroxylation of the ligand is
performed by with a diferric complex
prepared in situ (L = N,N '-bis-(2,4,5-trimethoxybenzyl)ethylenediamine N,N ' -
diacetic acid). 213, 226
Meckmouche et al. have pointed out that the oxygenation of hydrocarbons
utilizing hydrogen peroxide proceeds partly by the metal-based mechanism. 227
Using a diiron(III) complex with a chiral ligand, (pb =
4,5(-)pinene-2,2'-bipyridine), enantio-selective catalytic hydroxylation by hydrogen
peroxide was first achieved. White et al. performed an efficient and selective
epoxidation of decene and other alkenes with a mononuclear iron complex

212, 225