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room temperature;
e.g.
styrene was converted to epoxide (89%) and aldehyde (10%)
within 9 h in the 100% conversion. Murahashi
et al.
also used an aldehyde
(heptanal) for aerobic oxidation of alkanes and alkylated arenes.
420
Iron
powder/acetic acid was used as the most effective catalyst, though and
were also examined. Oxo-iron species, which may be formed
via
peracids from acetic acid, was assumed as an active species for hydrogen abstraction
from alkanes and epoxidation of olefins. Kesavan
et al
.
421
used nanostructured
amorphous iron and alloy like for the oxidation of adamantane under 40
atm and at 28 °C in the presence of isobutyraldehyde and acetic acid. Only
alcohols and ketone (l-ol : 2-ol : 2 -one = 17 : 2 : 1) were obtained in the 52 %
conversion. Oxo-iron species was also assumed to explain the high selectivity for
the tertiary alcohol.
ortho-
phenylenebis(oxamato) as a moderately efficient catalyst for the aerobic epoxidation
of alkenes with co-oxidation of pivalaldehyde.
422
Characteristic results are the
stereodependent epoxidation of
cis-
and
trans
-stilbene (conversion rate is
trans >>
cis
Ruiz
et al.
have used an iron(III)-carbonato complex
of
and the rate enhancement by the addition of
N
-methylimidazole. Iron(IV)-
acylperoxo or iron(v)-oxo species derived by oxygen-oxygen bond cleavage of the
acylperoxo group was assumed as a probable candidate of active species. In this
connection, Nam
et al.
demonstrated the formation of a metal-acylperoxo complex
in the auto-oxidation of aldehyde.
423
)
4.4.3 Mono-Iron Oxygen Species
In the mechanism of cytochrome P450, it is assumed that the high-valent
iron-oxo species is formed from that may derive from the one-
electron reduction of oxy adducts, probably
via
an It is
well assumed that these types of iron-oxygen species are involved in the
mechanisms of nonheme iron oxygenases. As an activated bleomycin (BLM),
formation of a low spin by the reaction of with or
by with was shown kinetically and by ESI-MS.
424, 425
As a synthetic
high spin species, has been identified by resonance
Raman and other spectroscopies.
426,427
In recent years, formation of
and its deprotonated form
with different ligands have appeared. Kim
et
al.
detected species of
and
by ESI-MS in the co-injection solution of
, and TBHP.
428
Bernal
et al.
detected a low-spin
species by
ESI-MS and ESR in the solution of
and
(
L
:
N
-methyl-
N
,
N
',
N
'-
tris(2-pyridylmethyl)ethane-l,2-diamine).
429
Nguyen
et al.
detected a low-spin
species
and
by
ESR in the reaction of
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