Chemistry Reference
In-Depth Information
TABLE 5-2. The Results of Cleavage of 1 and Its Derivatives With
FeSO
4
in Aqueous CH
3
CN
Entry
Compound
Products (yields)
1
159a (1)
160a (28) (25%)
161a (15) (67%)
Others (
<
10%)
2
159b (123)
160b (37%)
161b (45%)
161e (4%, a
þ
b)
3
159c (125)
160c (45%)
161c (23%)
161e (25%)
4
159d
160d* (39%)
161d (56%)
5
159e (98)
160e (46%)
161e (25%)
6
159f
160f (59%)
161f (25%)
Note: Hydrolysis of 160d led to a dialdehyde.
During this project, an electron spin resonance (ESR) signal of secondary
carbon-centered free radical (163) was detected in the reaction of 1 and equivalent
ferrous sulfate in aqueous acetonitrile with MNP as a trapping agent.
279
In the same
year, Butler et al. detected the ESR signals of both primary (162) and secondary
free radicals (163) with DMPO and DBNBS as trapping agents.
280
Figures 5-3
and
5-4
show
the
ESR
spectra
with
MNP
and
DBNBS
as
trapping
agent,
respectively.
Based on these new evidences and the results published from other laboratories,
the reaction mechanism of 1 and ferrous ion was revised so that this
reaction proceeded through short-lived oxygen-centered free radicals and then
Figure 5-3. The ESR signal recorded in a run in aq. CH
3
CN with qinghaosu as substrate in
the presence of 1 equiv. of FeSO
4
with MNP as trapping agent.
Search WWH ::
Custom Search