Chemistry Reference
In-Depth Information
SCHEME 4.10.
Products of hydrolysis of
N
-acetoxy-
N
-acetyl-2-aminofluorene,
32a
.
Product analyses showed that for all esters the OH
and buffer-dependent
components generated
33
.The
k
o
term also predominately led to
33
for all esters
.
86
Hydrolysis products of
except
32a
and
32e
32a
at neutral pH included the
(Scheme 4.10).
86
Addition of reducing
rearranged materials
34a,b
and phenols
35a,b
.
86
It appeared that the singlet
ion is reduced without the involvement of the triplet.
86
Underwood and Callahan found that
k
o
for hydrolysis of
N
-acetoxyacetanilides
with
agents led to formation of
36
at the expense of
35a,b
s
þ
>
0.3 for the aryl substituent correlated with
s
to give a
r
of
þ
1.5 and
.
87
For those esters with
s
þ
<
s
þ
with a
hydrolysis led to
33
0.3,
k
o
correlated with
r
þ
of
O bond cleavage were isolated.
87
Substituent effects of rate constant for reactions that apparently lead to nitrenium
ions are very solvent sensitive. Gassman and Granrud showed that
k
obs
for
rearrangement of
6.2 and products consistent with N
s
þ
with a
r
þ
37a-g
in CDCl
3
(Scheme 4.11) correlated with
9.2.
88
The study by Novak and coworkers of hydrolysis of esters of hydroxamic
acids
18,89-96
has been reviewed.
54
The pH-independent hydrolysis rate constants
of
of
s
þ
with
38a-f
in 5 vol% CH
3
CN-H
2
O (Schemes 4.12 and 4.13) correlated with
r
þ
4.5 at 25
C.
18
This is less negative than
r
þ
for N
O bond cleavage of similar
esters in less polar solvents,
87,88
but the trend is in the expected direction and the
magnitude of the effect is consistent with rate limiting formation of a nitrenium ion.
18
The hydrolysis products of
are summarized in Scheme 4.12.
18,89-93
These products, and those observed by others,
84,86,88
show that esters of
N
-arylhy-
droxamic acids do undergo N
38a-d
and
39
O bond cleavage, but alternative acyl or sulfonyl
SCHEME 4.11.
Rearrangement of
N
-methanesulfonate oxy acetanilides.
