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Anisotropic Effects in Heterocyclic Nitrosamines.

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We formulate scission of the carbon-mercury bond by iodine
as an SEi process, depicted in (3) [41. Since this should proceed also with other reagents, it should be possible to prepare
further hetero-substituted diazoacetic esters from the compound ( I ) 151.
Photolysis of (2) (450 W Hanovia lamp, Pyrex filter) gave
ethoxycarbonyliodocarbene (4), from which we obtained
ethyl l-iodo-2,2-dimethylcyclopropanecarboxylate( 5 ) (b.p.
45 "CiO.4 mm; yield 40%; NMR signals of the cyclopropane
protons as an AB spectrum at T = 8.7 with JABw 6 Hz) on
irradiation of (2) in isobutene until evolution of nitrogen
ceased. Products formed by insertion in the C-H bond were
not detectedr61. We conclude that the carbene ( 4 ) is more
selective than ethoxycarbonylcarbene.
[Z 372 IEI
Received: November 1 1th, 1966
German version: Angew. Chem. 79,50 (1967)
16 hr at 110°C. The composition and molecular weight correspond to an adduct of 2 moles of cyclopentadiene t o one of
maleimide and 2 g-atoms of sulfur. IR spectrum in KBr: 1765,
1715,1700cm-1 (imide-CO) ; 1600(C=C); 1550(imide-C=C).
UV spectrum in ethanol: 240 mp (log E = 3.38), 267 (3.85),
424 (3.34). These results indicate a dimercaptomaleimide
system. The NMR spectrum at 90 MHz in CDCI3 [T = 4.34
(2 olefinicprotons), 6.97 (N-CHj), 8.42 (1 H), poorly resolved
multiplet at r=6.4 to 7.9 (9 H)] does not permit unambiguous
decision between the structures (3a) and (36).
The formation of (3a) or (36) is preferred to an asymmetrical
decomposition of ( I ) to a compound (4) V-1 and acetylenedicarboxyimide (5), from which (2) is then obtained. The DielsAlder adduct of cyclopentadiene to (5), not hitherto described, would probably not be stable under the reaction
conditions.
0
0
]*I Dip1.-Chem. F. Gerhart, Prof. Dr. U. Schollkopf, and
Dr. H. Schumacher
Organisch-Chemisches Institut der Universitat
Windausweg 2
34 Gottingen (Germany)
[l] Cf. R. Huisgen, Angew. Chem. 67, 439 (1955).
[2] Chloro- and bromo-diazomethane were recently prepared in
situ; they are stable only below -40 "C. Cf. G. L. Closs and J . J .
Coyle, J. Amer. chem. SOC.87, 4270 (1965).
[3] E. Buchner, Ber. dtsch. chem. Ges. 28, 215 (1895).
[4] For the mechanism of C-Hg fission by iodine see S . Winstein
and T. G. Traylor, J. Amer. chem. SOC.78, 2597 (1956).
[ 5 ] Cf. U. Schollkopf and P. Murkusch, Tetrahedron Letters
1966, 6199.
[6] It is possible that they decompose under the conditions of the
photolysis.
Evidence for the Intermediate Occurrence of
Acetylenedicarboxyimide
By W. Draber[*J
When 1,4-dithiintetracarboxydiimides ( I ) are heated in
pyridine at 120 OC, mellittriimides (2) are obtained in yields
of up to 5 0 % together with sulfur and unidentified brown
products. Small quantities of mellittriimide were also
occasionally obtained in the preparation of the dithiins ( I )
from dichloromaleimides and H2S in the presence of a
material such as CaCO3[" to neutralize the acid formed.
Heating the dithiins without pyridine or in indifferent
solvents such as xylene or ethanol does not lead to formation
of triimides (2).
An indication of the course of the reaction was given by
the formation of a yellow compound,m.p. 137.5-138 "C, yield
7 %, that could be isolated chromatographically together
with the mono- and di-adducts of cyclopentadiene to ( I ) and
24% of (2), after the dithiin ( I ) had been heated with an
excess of dicyclopentadiene and pyridine under nitrogen for
Angew. Chem. internat. Edit.
Vol. 6 (1967)
No. 1
Attempts to prepare the Diels-Alder adduct of cyclopentadiene to acetylenedicarboxylic anhydride from the corresponding acid by dehydration with acetic anhydride gave
a substance that polymerized rapidly even at room temperature.
Received: November 15th, 1966
[Z 377 IE]
German version: Angew. Chem. 79, 51 (1967)
[*] Dr. W. Draber
Shell Grundlagenforschung GmbH
SchloD Birlinghoven
52 Siegburg (Germany)
Present address: Farbenfabriken Bayer
Wissenschaftliches Hauptlaboratorium
509 Leverkusen-Bayerwerk (Germany)
111 W. Druber, unpublished work.
[2] Compounds of 1,2-dithietestructure are known to add readily
to reactive double bonds, yielding 1,4-dithiins: H . E. Simmons,
D . C . Blomstrom, and R. D . Vest, J. Amer. chem. SOC.84, 4782
(1962).
Anisotropic Effects in Heterocyclic Nitrosamines
By Y. L. Chow[*]
The restricted rotation about the partial N-N double bond
of a nitrosamino group derived from a symmetrical amine
gives rise to different NMR chemical shifts for the cis- and
trans-cc-methyleneprotons [**I. A conformationally "frozen"
heterocyclic nitrosamine should allow direct observation of
the long-range shielding of the nitrosamino group, provided
that inversion at the amine center is slow.
The 4-substituted N-nitrosopiperidines ( I b ) and ( I c ) give
four well-separated signals, corresponding to the four ccprotons in different environments (see Table 1). The signals
were assigned on the basis of their splitting pattern and
coupling constant 111 and by decoupling experiments at
100 MHz. The equatorial protons He and Hk, being coplane, absorb at
planar, or nearly so, with the C,-N-N-0
approximately the same (lower) field 121, whereas the axial
protons Ha and H', absorb at higher fields. Since Ha is
situated inside the semi-circular shielding zone of the nitrosamino group, its signal appears at a far higher field. This
anisotropy is even better manifested by an unusually large
75
chemical shift difference (A8 = 2.4-2.9 ppm) between the
axial (Ha) and equatorial (He) protons of the cis-methylene
group. In contrast, the corresponding chemical shift difference
of the trans-methylene groxp is much smaller (A% = 1-1.4
PPm).
1,5-Diazabicyclo[5.4.0]undec-5-ene,a New
Hydrogen Halide Acceptor
By H . Oediger and Fr. MiiNer [*I
1,5-Diazabicyclo-4.3.0]non-5-ene( I ) can be used to introduce double bonds by removal of hydrogen halide[l$21. We
have now found that 1,5-diazabicyclo[5.4.0]undec-5-ene(2),
obtained, analogously to ( I ) [ I s 3 1 from caprolactam and
acrylonitrile by way of compounds (3) and (4), is considerably superior to the base ( I ) for this purpose.
R
The conformationally rigid and unsymmetrical trans-decahydroquinoline gives the anti-nitrosamine (2) as the sole
nitrosation prodact. The Dreiding model shows that the
rigidly held equatorial proton of the P-methylene group in
the cyclohexane ring is close to the oxygen in the syn-configuration and thus destabilizes this configuration. The
chemical shifts of the cis-a-methylene protons and particularly the large difference (2.73 ppm) between the shifts
of the axial and equatorial protons lead unambiguously to
the anti-configuration assignment for the nitrosamine (2).
The NMR spectrum of conformationally mobile N-nitrosopiperidine (la) is considerably simplified due to rapid interconversion of the conformers, whereby the axial and equatorial protons give a n average signal. Since the two conformers are energetically equivalent, the signal of the cis-amethylene protons should occur half-way between the H a
and He signals. The observed signal at T = 6.35 is therefore
assigned to cis-a-methylene protons and that at T = 5.87 to
trans-a-methylene protons. In acyclic nitrosamines cis-amethylene protons also absorb at a higher field than frunsa-methylene protons 131.
As shown in the table, the yields of alkene are considerably
improved by use of the base (2).
~
Bromoalkane
Alkene
4-Bromoheptane
2-Bromoheptane
3-Heptene
1- and 2-Heptene
(cu. 1.4) [a]
1- and 2-Octene
(ca. 1:4) [a]
(1)
2-Bromooctane
Table 1. NMR data of nitrosamines at 60 MHZ (r values, Varian
A 56/60 spectrometer, (CH>)4Si as internal standard).
AS [a1
(ppm)
Ha
He
c&
7.50
7.83
5.15
5.18
2.35
2.65
6.35
6.80
5.38
5.57
0.87
1.23
( I c ) [bl
CCId
CsHs
7.67
8.05
5.17
5.18
2.45
2.87
6.47
7.02
5.38
5.67
I ,09
1.40
i2)
CC14
CCH4
7.63 [c]
7.67
4.90 Id]
4.83
?.73
2.84
6.68
7.11
-
-
( I b ) [b]
ilu)
CC14
CClr
GH6
-
[bl The axial protons show a triplet,each split into doublets,Jgem%Jaa%
12-13 Hz, Jae = 3-4 Hz. The equatorial protons show a doublet that
is further split into multiplets. Jgem = 13 Hz; W*/z = 6-7 Hz.
[cl Determined by decoupling experiments.
[dl Each doublet is further split into multiplets, Jgem
w1i2= 7 n z .
=
I
(21
60
36
91
78
40
84
Method: A mixture of equimolar amounts of bromoalkane
and base is warmed to 80-90°C and the alkene formed is
distilled off. A solvent such as dimethyl sulfoxide may be
added.
Received: October 28th, 1966
[Z 355 1E1
German version: Angew. Chem. 79, 53 (1967)
['I Dr. H. Oediger and Dr. Fr. Moller
[
6.35
6.57
Yield (%) on use of
Wissenschaftliches Hauptlaboratorium
[ Farbenfabriken Bayer AG.
509 Leverkusen (Germany)
111 H. Oediger, H. J. Kabbe, Fr. Moller, and K. Eiter, Chem. Bet-.
99, 2012 (1966).
[2] H . Oediger, K. Eiter, Fr. Moiler, and H . J . Kabbe, German
Pat. 1186063 (15th May, 1962).
131 Fr. Moller, German Pat. Appln. F 47138 IV d/12 p.
14 Hz and
Received: August 15th, 1966; revised October 25th. 1966 [Z 357 IE]
German version: Angew. Chem. 79, 51 (1967)
Free-Radical Decomposition of Azo Compounds
Induced by Organotin Hydrides
[*I Dr. Y.L. Chow
Department of Chemistry
Simon Fraser University
Burnaby, B. C. (Canada)
[**I The same convention of cis-trans a-protons and syn-anti
configuration as in [3]is adopted.
[l] R. U. Lemieux, R. K. Kulling, and R.Y.Moir, J. Amer. chem.
SOC.80, 2237 (1958); R. U.Lemieux, R. K. Kulling, H. J. Bernsfein, and W. G. Schneider, ibid. 80, 6098 (1958);F. A. L. Anet,
R.A. B. Bannard, and L. D. Hall, Canad. J. Chem. 41, 2331 (1963).
[2]He is slightly less shielded than H', by ca. 0.25 ppm since
H e is conformationally in juxtaposition with the high electron
density of nitrosamino oxygen. S. Winstein, P. Carter, F. A. L.
Anet, and A. H. R. Bourn, J. Amer. chem. SOC. 87, 5247 (1965);
A. D . Buckingham, Canad. J. Chem. 38,300 (1960).
[3] G. J. Karabatsos and R. A. Taller, J. Amer. chem. SOC.86,
4373 (1964).
"
76
By W. P . Neumann and H. Lind[*l
We have observed a radical-induced decomposition of the
and R-X-N=N-X-R,
azo compounds R-N=N-X-R'
where X is a covalently bound polar group.
Homolysis of phenyl phenylazo sulfone ( 1 ) I l l in dilute
toluene solution is accelerated ten-fold, even at 80 "C, if an
organotin hydride is present (ti/2 = 8 min). Benzene, Nz, and
a stannyl phenylsulfinate (2), m.p. 67 OC, are formed in equimolar amounts. Occurrence of free phenylsulfonyl radicals
can be excluded; they would afford the sulfinic acid and, with
further hydride, Hz. Stannyl radicals (3) induce the acceleration and their covalent attachment to the sulfonyl group is
synchronous with the detachment of the azo group ( s R 2
mechanism).
Angew. Chem. internat. Edit.
1 VoI. 6 (1967) 1 No. 1
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