Chemistry Reference
In-Depth Information
N
N
h
ν
Ph
113
hν
>550 nm
?
310-390 nm
H
N
3
N
h
ν
CN
CN
N
Ph
N
Ph
?
N
111
112
CPh
114
Ph
Photochemical reactions
H
hν
FVT
118
FVT
N
3
H
N
N
FVT
FVT
Thermal reactions
N
N
Ph
N
Ph
115
112
111
FVT
FVT
N
NH
2
N
N
Ph
117
116
SCHEME 8.20.
amines is diagnostic for triplet nitrenes, even in low-pressure gas-phase
reactions.
18,22
The formation of indoloquinoline
116
on FVT presumably occurs
via the 7
H
-intermediate
l
max
330, 400 nm) is also the end reaction in the matrix photolysis, which eventually
results in loss of the observable intermediates
115
(Scheme 8.20). Most likely, cyclization to
115
(
(Scheme 8.20).
40
113
and
114
Tetrazolyl quinazoline
119
and triazolo quinazoline
120
also afforded the
in 67-98% yield on FVT at 400-600
C, but no traces of indolo-
3-cyanoindole
118
quinoline
were detectable (Scheme 8.21). This is in agreement
with the conclusion reached for 4-quinazolinyl carbene above (Scheme 8.19), that ring
contraction takes placevia the pathway 2-phenyl-4-quinazolinyl carbene
116
or the amine
117
121!
cyclic
ketenimine
113!
nitrile ylide
114!118
. The data demonstrate that carbene
121
does
not
convert
. In other words, carbene-nitrene
rearrangements are known to occur (see above), but they may be bypassed when
other reactions, for example, ring opening to nitrile ylides, become more favorable.
thermally into nitrene
112
8.4.1.1 4-Pyrimidinyl Nitrenes and 2-Pyrazinyl Nitrenes. 2-Pyrazinyl nitrene
123
125
and 4-pyrimidinyl nitrene
were generated by Ar matrix photolysis of the
respective tetrazoloazines (Scheme 8.22). Both triplet nitrenes were observed by
ESR spectroscopy, giving rise to typical aryl nitrene-type transitions (
123
:
0.0012 cm
1
).
20,41
Using matrix IR spectroscopy, an intermediate appeared at 1973 and 840 cm
1
0.000 cm
1
;
D
/
hc
¼
1.014;
E
/
hc
¼
125
:
D
/
hc
¼
1.1937;
E
/
hc
¼
