Chemistry Reference
In-Depth Information
0cm
1
).
146
In fluoro-
lube, the triplet tosyl nitrene was reported to be stable for 18 h,
79
whereas in the EPA
(ether, pentane, alcohol mixture) glassy matrix it slowly decayed.
146
In conjunction with the observation of the characteristic EPR spectrum of
3
61a
0.984 cm
1
,
characteristic of tolyl nitrene (
j
D
/
hc
j¼
j
E
/
hc
j¼
,
the electronic absorption spectrum was observed upon irradiation of
(75 s,
254 nm) in an EPA glassy matrix.
146
This spectrum had an intense band at 315 nm,
less intense band at 460 nm, and a shoulder at about 540 nm. It was also assigned to
3
60a
.
146
Note that this spectrum is very similar to that of triplet phenyl nitrene,
although the visible band and shoulder of the former are shifted at about 100 nm to
the red comparing to those of the latter (380 and
61a
440 nm).
14,15,130
Unfortunately, the chemistry of sulfonyl nitrenes is not well established because of
problems with the sulfonyl azide precursors.
6
For example, photolysis of sulfonyl
azides in aprotic solvents gave mostly dark, amorphous precipitates, which were hard
to characterize.
6,133
Despite the triplet multiplicity of the sulfonyl nitrene ground
states, thermolysis, and photolysis of sulfonyl azides generally leads to negligible
amounts of the products characteristic for the triplet nitrene reactions.
6,137-142,146
The possibility of reactions of the azide excited states hampers the interpretation of
the available data on the sulfonyl azide photochemistry.
6,131,133,134,141
Elimination of
SO
2
was observed in the thermolysis of various alkyl- and arylsulfonyl azides.
6,132
For these reasons, sulfonyl azides have been called only occasionally useful
precursors to sulfonyl nitrenes.
6,26,133
Nevertheless, the products characteristic of sulfonyl nitrene reactions were
reported in many papers devoted to the thermolysis and photolysis of sulfonyl
azides.
6,131-148
The insertion of singlet mesyl nitrenes (
61b
) into the C
H and
).
136
a Irradiation of
O
H bonds was observed upon photolysis of mesyl azide (
60b
60b
in a mixture of cyclohexane and dichloromethane (1:1) at 0
C gave
N
-cyclo-
hexylmethanesulfonamide (
62b
63b
, 18.3%) and methanesulfonamide (
, 38.4%).
60b
in ethanol gave
N
-ethoxymethanesulfonamide (
64b
Irradiation of
, 48.8%) and
63b
(43.3%).
136a
Formation of these products suggests the intermediacy of nitrene
61b
. The N-substituted sulfonamides
62b
and
64b
are formed due to the C
H and
H insertion of singlet nitrene
1
61b
O
, respectively. The sulfonamide
63b
is most
likely formed by the triplet nitrene
3
61b
abstraction of hydrogen atom from the
solvent molecules (Scheme 12.29).
CH
3
SO
2
NHC
6
H
11
62b
1
61b
h
v
-N
2
CH
3
SO
2
N
1
CH
3
SO
2
N
3
CH
3
SO
2
NHOEt
64b
60b
cyc-C
6
H
12
or EtOH
CH
3
SO
2
N
3
3
61b
CH
3
SO
2
NH
2
63b
SCHEME 12.29.
Photolysis of mesyl azide in the presence of ethanol and cyclohexane.
136a
