Chemistry Reference
In-Depth Information
1
N
N
3
NHCH
2
CH
3
O
S
O
O
S
O
CH
3
O
S
O
h
v
-N
2
+
67
CH
3
CH
3
CH
3
CH
3
60a
H
3
C
NH
NH
2
CH
3
O
S
O
O
S
O
CH
3
+
+ tars
H
3
C
O
2
S
N
CH
3
CH
3
CH
3
68
63a
SCHEME 12.32.
Photolysis of tosyl azide (
60a
)in
p
-xylene.
142
The reactions of sulfonyl nitrenes with aromatics have been extensively studied
by Abramovitch and coworkers
6,134,139,141,144
, Hoyle et al.,
142
and Renfrow and
Devadoss.
143
The isolated products are
N
-arylsulfonamides. However, the interme-
diate azepines have been trapped in some cases.
6,134,141
For instance, photolysis of
60a
in
p
-xylene afforded three products: amide
63a
,
N
-(
a
67
-xyly1)-tosylamide (
),
).
142
It was observed that the yields of products
and
N
-(2,5-dimethylphenyl)-tosylamide (
68
varied with the time
between the completion of the photolysis and the start of the HPLC analysis. An
unidentified peak was also detected by HPLC with a half-life of about 40min at
room temperature. Decay of this peak was accompanied by the formation of
63a
and
68
63a
and
68
. The following mechanism of photolysis of
60a
in
p
-xylene was proposed
(Scheme 12.32).
142
Therefore, it is clear that singlet sulfonyl nitrenes are formed upon photolysis and
thermolysis of sulfonyl azides. The sulfonyl nitrenes have a triplet ground state.
However, the identified products of the sulfonyl azide photolysis and thermolysis are
mainly derived from the singlet nirene reactions. Maloney and coworkers studied the
ns LFP of tosyl azide (
60a
) in ethanol and cyclohexane in order to detect triplet tosyl
nitrene
3
61a
and to study its reactivity.
146
LFP of
in methanol resulted in a
transient spectrum with two maxima at 325 and 460 nm, whereas in cyclohexane, a
single maximum was observed at 310 nm. The short-wavelength transient absorp-
tions were assigned to the triplet nitrene
3
61a
60a
.
146
Note that the transient absorption
spectrum detected in methanol coincides fairly well with the spectrum of the product
of tosyl azide photolysis in EPA matrix at 77 K. As aforementioned, the latter
spectrum was also assigned to
3
61a
.
