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The photodecomposition of ethyl azidoformate
Tetrahedron Letters in Great Britain.
No. 7,
pp.
277-280,
1962.
Pergamon Press
Ltd.
Printed
THE PHOTODECOMPfXITION OF ETHYL AZIDOFOPMATE Walter Department
Lwowski and Thomas W. Mattingly
of Chemistry,
Yale
(Received
EVIDENCEhas been presented deficient
and electroneutral
various
organic
called
“nitrene”.* Many of
decomposition
rearrangement.
6
involving
favourable
aryl
Acyl
is
not
clear
A case
of
cyclization
bond formation
of
a short-lived,
analog
azides
of
undergo
whether of
carbene
Curtius
here
involved
acyl
under
of be
the
rearrangement
is
a decomposing carbon
will
394 and involve
a nitrene
to a methyl
electron-
in the decomposition
are intramolecular
and it
circumstances
1962)
intermediate
nitrogen
reported
azides.
New Haven, Connecticut
the occurrence
This
the reaction of
28 February
nitrogen
l-5
azides.
when decomposed,
amide,
for
University,
azide
sterically
in the to an very
has been reported.5
The terms nitrene, imine, and azene are being used in the literature for the species R-R:. All these terms have been used earlier for other, different species. “Nitrene” seems to us to be the best choice, since it stresses the analogy to the iso-electronic carbene, and was used previously to designate compounds containing pentacovalent nitrogen, not likely to be ever found. [cf. C.H. Hassal and A.E. Lippman, J. Chem. Sot. 1059
(1953)l. 1. Curtius, 2. Ansew. Chem. &, III, papers in J. Prakt. Chem. m (1930). J.F. Heacock and MT. Edmison, earlier papers cited therein. P.A.S. Smith At et al Abstracts Chemical Society Meeting, St. 524 (1958) and earlier papers
J.
Apsimon and O.E.
K.R. Brower,
J.
Edwards,
a,
J. Amer. Chem. Sot.
III
(1914);
&& 3460
(1960)
and many and
of papers presented at the American Louis, 1961, pp. 43-50; J. Ors. Chem. a, cited therein.
G. Smolinsky, J. Amer. Chem. Sot. J. Ore. Chem. &, 4108 (1961).
cf.
134 (1913);
g,
Proc.
4717
(1960);
Chem. Sot.
Amer. Chem. Sot. 277
@,
4370
e,
2489,
461 (1961). (1961).
4483
(1961);
278
The photodecomposition of ethyl azidoformate
No.7
Since azidoformatesdo not undergo Curtius rearrangement,we investigated the photodecomposition of ethyl azidoformate7in the presence of cyclohexeneand cyclohexane. Irradiationwas done with a low pressure mercury lamp, such as "OriginalHanau PL 368", having maximum emission at 254 mp. A cyclohexenesolution of ethyl azidoformateproduced a better than 50 per cent yield of the adduct I, 7-carboethoxy-7azabicyclo(4.1.0) heptane. (Found: C, 64.03; H, 8.91; N, 8.22. Calc. for CqH15N02: C, 63.88; H, 8.9.;;N, 8.28.) Infrared spectrum: no N-H band, no C-H above 3000 cm-1 (no C=C unsaturation),CO band at 1720 cm-1. NMR spectrum: ring CH2 groups 3 and 4 + CH of ethyl group: multiplet 8.6 to 8.9~. Ring CH2 groups 2 and 5: 3 8.2~; ring C-H at C-l and 6: 7.5r; CH2 of ethyl group: quartet at 6.0~.
I Compound I was also synthesizedfrom cyclohexeneimine' and ethyl chloroformate. The syntheticcompound and I had identicalIR and NMR spectra and the same retentiontime in gas chromatography. To exclude a triazolineintermediateII, we follqwedthe evolutionof nitrogen during irradiationat room temperatureand compared it with the disappearanceof the azide (by I.R. spectrometry). Nitrogen evolutionand azide disappearancewere simultaneous. Within experimentalerror, all nitrogen correspondingto the amount of azide decomposedwas evolved at 7
M.O. Forster and H.E. Fierz, J. Chem. Sot. s,
81 (1908).
8 O.E. Paris and P.E. Fanta, J. Amer. &em. Sot. &,
3009 (1952).
The photodecomposition
No.7
of
ethyl
279
azidoformate
60 -OC,H, II once,
with
switched More the
no storage off,
nitrogen
decomposition
about
employed
ethyl in
cent
of
for
the
intervention
azidoformate
the
in
cyclohexene
the
When the
an intermediate.
of
H, 10.02;
C, 63.40; N, 8.20%).
no C-H above 8.6-8.8r. compound 1-R. at
3000
N, 8.18.
M.p.:
56.6’-57.2’;
C-H on C-l: was
also
CO band 8.2r,
prepared
in
CH2 in
ethyl
identical,
the
N-H 3455
mixed
ethyl
melting
cm-l,
CH2 and CH3:
quartet and
a yield
C, 63.13;
NMR spectrum:
cyclohexylamine
same
H,
spectrum:
group:
from
obtained.
CgH17N02r
1-R. cm-‘.
was
oc2
for
the
cyclohexane
III’
Calc.
1726
from
were
was
comes
Under
experiments,
N-cyclohexyl-urethane
10.00;
cm -1,
and NMR spectra
5.97.
The
chloroformate.
point
underpressed
56.8’-57.5’. Both
and
the
reactions
of
can
be explained
cyclohexane
EtO-CO-N: 9
H,
a nitrene
cyclohexane.
-co-
(Found:
lamp
ceased.
evidence of
50 per
in
evolution
conclusive
conditions of
nitrogen
A. Skita
(with
the six
and H. Rolfes,
decomposing
electrons Ber.
ethyl
by assuming on nitrogen Dtsch.
azidoformate a nitrene paired,
Chem. Ges.
3,
with
cyclohexene
intermediate singlet
state)
1242 (1920).
or
280
The photodecomposition
EtO-CO-d. singlet
(with species
respectively. ceivably
8762)
might
electrons,
nitrene
- and could
EtO-CO-iH,
in the abstraction
which step,
ethyl
a diradical
add to the double
The triplet
in two steps
form the radical formed
unpaired
of
a hydrogen
then combines
We are indebted to the National in support of this research.
into
add to the double
abstract
with
the observed
Institute
No.7
in the triplet
bond and insert
could
to give
azidoformate
state).
The
the C-H bond, bond - con-
from cyclohexane, the cyclohexyl urethane
of Health
for
to
radical
III. a grant
(RG
No. 7,
pp.
277-280,
1962.
Pergamon Press
Ltd.
Printed
THE PHOTODECOMPfXITION OF ETHYL AZIDOFOPMATE Walter Department
Lwowski and Thomas W. Mattingly
of Chemistry,
Yale
(Received
EVIDENCEhas been presented deficient
and electroneutral
various
organic
called
“nitrene”.* Many of
decomposition
rearrangement.
6
involving
favourable
aryl
Acyl
is
not
clear
A case
of
cyclization
bond formation
of
a short-lived,
analog
azides
of
undergo
whether of
carbene
Curtius
here
involved
acyl
under
of be
the
rearrangement
is
a decomposing carbon
will
394 and involve
a nitrene
to a methyl
electron-
in the decomposition
are intramolecular
and it
circumstances
1962)
intermediate
nitrogen
reported
azides.
New Haven, Connecticut
the occurrence
This
the reaction of
28 February
nitrogen
l-5
azides.
when decomposed,
amide,
for
University,
azide
sterically
in the to an very
has been reported.5
The terms nitrene, imine, and azene are being used in the literature for the species R-R:. All these terms have been used earlier for other, different species. “Nitrene” seems to us to be the best choice, since it stresses the analogy to the iso-electronic carbene, and was used previously to designate compounds containing pentacovalent nitrogen, not likely to be ever found. [cf. C.H. Hassal and A.E. Lippman, J. Chem. Sot. 1059
(1953)l. 1. Curtius, 2. Ansew. Chem. &, III, papers in J. Prakt. Chem. m (1930). J.F. Heacock and MT. Edmison, earlier papers cited therein. P.A.S. Smith At et al Abstracts Chemical Society Meeting, St. 524 (1958) and earlier papers
J.
Apsimon and O.E.
K.R. Brower,
J.
Edwards,
a,
J. Amer. Chem. Sot.
III
(1914);
&& 3460
(1960)
and many and
of papers presented at the American Louis, 1961, pp. 43-50; J. Ors. Chem. a, cited therein.
G. Smolinsky, J. Amer. Chem. Sot. J. Ore. Chem. &, 4108 (1961).
cf.
134 (1913);
g,
Proc.
4717
(1960);
Chem. Sot.
Amer. Chem. Sot. 277
@,
4370
e,
2489,
461 (1961). (1961).
4483
(1961);
278
The photodecomposition of ethyl azidoformate
No.7
Since azidoformatesdo not undergo Curtius rearrangement,we investigated the photodecomposition of ethyl azidoformate7in the presence of cyclohexeneand cyclohexane. Irradiationwas done with a low pressure mercury lamp, such as "OriginalHanau PL 368", having maximum emission at 254 mp. A cyclohexenesolution of ethyl azidoformateproduced a better than 50 per cent yield of the adduct I, 7-carboethoxy-7azabicyclo(4.1.0) heptane. (Found: C, 64.03; H, 8.91; N, 8.22. Calc. for CqH15N02: C, 63.88; H, 8.9.;;N, 8.28.) Infrared spectrum: no N-H band, no C-H above 3000 cm-1 (no C=C unsaturation),CO band at 1720 cm-1. NMR spectrum: ring CH2 groups 3 and 4 + CH of ethyl group: multiplet 8.6 to 8.9~. Ring CH2 groups 2 and 5: 3 8.2~; ring C-H at C-l and 6: 7.5r; CH2 of ethyl group: quartet at 6.0~.
I Compound I was also synthesizedfrom cyclohexeneimine' and ethyl chloroformate. The syntheticcompound and I had identicalIR and NMR spectra and the same retentiontime in gas chromatography. To exclude a triazolineintermediateII, we follqwedthe evolutionof nitrogen during irradiationat room temperatureand compared it with the disappearanceof the azide (by I.R. spectrometry). Nitrogen evolutionand azide disappearancewere simultaneous. Within experimentalerror, all nitrogen correspondingto the amount of azide decomposedwas evolved at 7
M.O. Forster and H.E. Fierz, J. Chem. Sot. s,
81 (1908).
8 O.E. Paris and P.E. Fanta, J. Amer. &em. Sot. &,
3009 (1952).
The photodecomposition
No.7
of
ethyl
279
azidoformate
60 -OC,H, II once,
with
switched More the
no storage off,
nitrogen
decomposition
about
employed
ethyl in
cent
of
for
the
intervention
azidoformate
the
in
cyclohexene
the
When the
an intermediate.
of
H, 10.02;
C, 63.40; N, 8.20%).
no C-H above 8.6-8.8r. compound 1-R. at
3000
N, 8.18.
M.p.:
56.6’-57.2’;
C-H on C-l: was
also
CO band 8.2r,
prepared
in
CH2 in
ethyl
identical,
the
N-H 3455
mixed
ethyl
melting
cm-l,
CH2 and CH3:
quartet and
a yield
C, 63.13;
NMR spectrum:
cyclohexylamine
same
H,
spectrum:
group:
from
obtained.
CgH17N02r
1-R. cm-‘.
was
oc2
for
the
cyclohexane
III’
Calc.
1726
from
were
was
comes
Under
experiments,
N-cyclohexyl-urethane
10.00;
cm -1,
and NMR spectra
5.97.
The
chloroformate.
point
underpressed
56.8’-57.5’. Both
and
the
reactions
of
can
be explained
cyclohexane
EtO-CO-N: 9
H,
a nitrene
cyclohexane.
-co-
(Found:
lamp
ceased.
evidence of
50 per
in
evolution
conclusive
conditions of
nitrogen
A. Skita
(with
the six
and H. Rolfes,
decomposing
electrons Ber.
ethyl
by assuming on nitrogen Dtsch.
azidoformate a nitrene paired,
Chem. Ges.
3,
with
cyclohexene
intermediate singlet
state)
1242 (1920).
or
280
The photodecomposition
EtO-CO-d. singlet
(with species
respectively. ceivably
8762)
might
electrons,
nitrene
- and could
EtO-CO-iH,
in the abstraction
which step,
ethyl
a diradical
add to the double
The triplet
in two steps
form the radical formed
unpaired
of
a hydrogen
then combines
We are indebted to the National in support of this research.
into
add to the double
abstract
with
the observed
Institute
No.7
in the triplet
bond and insert
could
to give
azidoformate
state).
The
the C-H bond, bond - con-
from cyclohexane, the cyclohexyl urethane
of Health
for
to
radical
III. a grant
(RG