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Methylenenorbornadiene a Bicycloheptafulvene.

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The monothiolate first formed was converted by the
trapping isothiocyanate into the intermediate ( 3 ) which
cyclized immediately by attack of the nucleophilic sulfur
on the triple bond1'], yielding ( 4 ) and thus preventing
Of the second phenylacetylene group' By
working, the bicyclic thiolate ( 4 ) containing the eightmembered ring could be isolated. When even gently warmed it loses elemental mercury and passes by. ring- contraction into the dithiazepine (5). The thiourea component
may be ( I ) with a five- or a six-membered ring; the seven-
7,8-Dikydro-3-pkenyl-5-tkio-5H-imidazo~2,I-b]-[I,5,3]ditkiazepine ( 6 )
( 5 a ) (1.7 g, 0.005 mol) is heated with sulfur (1g) in CS,
(100ml) for some hours under reflux. After a short time
the yellow compound (6) separates and can be recrystallized from pyridine [m.p, 168-1710~ (dec., loss of cs,);
yield 1.3 g, 93x1.
Received: February 17, 1972 [Z 613 IE]
German version: Angew. Chem. 84,535 (1972)
Table I.Properties and spectroscopic data for the dithiazepines ( 5 )
IR (cm-')
NMR (6, ppm)
3115 ( = C H )
4.65 (4H/s)
6.8-7.7 (11 H/m)
60 MHz
3100 ( = CH)
2.06 (3 H/s)
4.63 (4 H/s)
67-7.7 (10H/m)
60 MHz
1.72 (2H/m)
3.42 (4 Him)
5.52 (1H/s)
7.0-7.5 (10H/rn)
100 MHz
M. p. (uncorr.)
Recryst. from
n -Butanol
3090 ( = C H )
2310 ( = CD)
[a] Internal standard : hexarnethyldisiloxane (HMDSO).
membered ring analog, however, apparently yields the
carbodiimide with loss of HgS. Only reactive isothiocyanates such as phenyl or o-tolyl isothiocyanate can be used as
isothiocyanate component.
Satisfactory elemental analyses and IR, NMR, and mass
spectra prove the assigned structures (see Table 1). The
molecular ion does not appear in the mass spectra since it
at once splits off the isothiocyanate which forms the reference mass line. By using deuterated thioureas ( I ) it can be
shown that the original N-H proton appears in the product (5) as the olefinic C-H proton.
The phenylimino group in compound ( 5 a ) can be split
off by several hours' heating with sulfur in carbon disulfide,
being replaced by a thiooxo group (6).
To the best of our knowledge the bicyclic dithiazepines
prepared by this single-batch process belong to a new
heterocyclic system, whose parent compound is unknown.
This synthesis would not be possible without collaboration
of the mercury atom as bonding agent.
-5H-imidazo[2,I-h]-[1,5,3]ditkiazepine( 5 a )
Equimolar amounts of 2-imidazolidinethione ( I ) , n = 2,
mercury bis(pheny1acetylide) and phenyl isothiocyanate
were heated in pyridine for about 30min under reflux.
Mercury separates. After the filtrate has been concentrated,
the yellow-white ( 5 a ) crystallizes either directly or on addition of ether. (5b) and (5c) are prepared analogously.
[I]Part of the Dissertation of R. Oxenius, Universitiit Frankfurt 1972.
We thank the Hermann-Schlosser-Stiftung for a stipendium.
[ I ] J . R. Johnson and W L. McEwen. J. Amer. Chem. SOC.48, 474
(1 926).
[3] W Ried, W Merkel. and R. Oxenius, Chem. Ber 103, 32 (1970).
[4] N . R. Euston and
D. R. Cmsady, J. Org. Chem. ZY, 1851 (1964).
Methylenenorbornadiene, a Bicycloheptafulvene['][*1
By Reinkard W. HofSmann, Reinkard Schiittler,
Werner Sckafer, and Armin Schweig"'
The reactivity of heptafulvene is to be ascribed to strong
polarization with formation of an aromatic systemcz1.
This phenomenon is not restricted to classical aromatic
compounds but can be demonstrated also for bicycloaromatic systems, as we wish to illustrate for methylenenorbornadiene ( I ) [31.
Crossed longicyclic interaction[41of the exocyclic double
bond of ( I ) with the norbornadiene x-system should
destabilize the norbornadiene
This interaction
can be demonstrated by photoelectron s p e c t r o ~ c o p y [in~ * ~ ~
a comparison with norbornadiene (2) and 7-methylenenorbornane (3). It can be seen in Figures 1 and 2 that the
HOMO (highest occupied MO) of (I) is raised by 0.2 eV
relative to that of (2). A direct consequence of this interaction is the tendency to formation of the bicycloaromatic
state ( 4 ) , which causes polarization of the exocyclic double
bond of ( I ) .
Prof. Dr. R. W. Hoffmann and DipLChem. R. SchuttIer
Fachbereich Chemie der Universitat
355 Marburg, Lahnberge (Germany)
DipLChem. W. Schafer and Prof. Dr. A. Schwelg
Physikalisch-Chemisches lnstitut der Universitat
355 Marburg, Biegenstrasse 12 (Germany)
[**] This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. The calculations
were carried out by the Deutsches Rechenzentrnm a t Darmstadt.
Angew. Chem. internut. Edit. 1 Vol. 11 (1972) 1 N O . 6
lower field from TMS) shows clearly the strong polarization of the exocyclic double bond of ( I ) .
The chemical shift and thus the charge density at C-8 of
( I ) are comparable with those at the p-C atom of enol
ethers (6 = 89-83 ppm"]), whilst the chemical shift for C-7
lies in the region typical of carbonyl-C atoms. The other
"C-NMR signals of ( 1 ) and (3) are at positions similar
to those of comparable parent compounds (f3 ppm)"'].
IP IeVl-
Fig. 1. Photoelectron spectrum of methylenenorbornadiene ( 1 ) [12].
Fig. 2. Vertical ionization potentials of the relevant n-bands of norbornadiene ( 2 ) [6], 7-methylenenorbornane ( 3 j , and methylenenorbornadiene (1). The x-MO's are classified relative to the C1-C'-C4
plane (s symmetrical, a antisymmetrical).-The assignments made for
(1) are supported by the orbital sequence obtained by the MIND0/2
method [13].
is evident even in the 'H-NMR spectrum: Thus the signal of the methylene protons of ( I ) at
T = 6.48 appears at unusually high field, about 0.9 pprn
higher than in the comparison system (3)[*l (r=5.55).
Received: February 8,1972 [Z 611 a IE]
German version: Angew. Chem. 84,533 (1972)
[l] Theory and Application of Photoelectron Spectroscopy, Part 6.Part 5 : [14].
[2] D. Lloyd: Carbocyclic Non-Benzenoid Aromatic Compounds.
Elsevier, Amsterdam 1966, p. 153.
[3] Prepared from quadricyclanone by a Wittig reaction in THF,
giving 3-methylenetetracycl0[]
heptane (50%)[b. p. 143"C;
NMR (CCI,): s=4.95 (s), 8.17 (d), 8.52 ppm (1) as 2:4:2; IR: 3075,
1680, 1232, 748 cm-'1, and rearrangement thereof to ( 1 ) by catalysis
with norbornadiene-palladium chloride. After gas-chromatographic
separation, yield 40% [b.p. 119°C; NMR (CCI,): s=3.28 (t), 6.26 (p),
6.48 (s) as 4:2:2; UV (CH,OH): shoulder at 235 nm (&=60);IR:
3070,2995, 1685,1665,850,730,720,623 cm-'; mje=104,103, 781.
[4] M . J . Goldstein and R. Hoffmann, J. Amer. Chem. SOC.93, 6193
[5] E. Heilhronner and H . D. Martin, Helv. Chim. Acta, in press.
discuss extensively this type of interaction for a derivative of (1). cf.
H . D. Martin and B. Forster, Angew. Chem. 84, 65 (1972); Angew.
Chem. internat. Edit. 11, 54 (1972).
[6] P. Bischof; J . A. Hashmall, E . Heilbronner, and I.: Hornung, Helv.
Chim. Acta 52, 1745 (1969).
A dipole moment of 0.76 D for ( I ) can be estimated from
the change in the chemical shift by 19 ppm. A CNDO/2
calculation'"] gave the same value ;the experimental value
was 0.71 D. Thus ( I ) is more than merely formally a bicycloheptafulvene.
[7] 9-Methylenebicyclo[4.2.l]nona-2,4,7-triene should have the opposite polarization; this is under investigation.
[8] Prepared from 7-norbornanone by a Wittig reaction in T H F
[b.p. 118.5"C; NMR (CC1,): s=5.55 (s), 7.75 (p), 8.55 ppm (m) as
2:2:8; IR: 1675,885,685 cm-I].
[9] K. Hatada, K. Nagata, and H . Yuki, Bull Chem. SOC.Japan 43,
3195, 3267 (1970); cf. R. C. Haddon, !L R . Haddon, and L. M . Jackman,
Fortschr. Chem. Forsch. 16, 103 (1971).
[lo] J . B. Grutzner, M . Jaurelat, J . B. Dence, R. A. Smitk, and J . D.
Roherrs, J. Amer. Chem. SOC.92, 7107 (1970).
[11] J . A . Pople and D. L. Beceridge: Approximate Molecular Orbital
Theory. McGraw-Hill, New York 1970.
1123 The He1 (584 photoelectron spectra were determined with a
PS 16 spectrometer from Perkin-Elmer Ltd., Beaconsfield (England).
[I31 M . J . S . Dewar. The Molecular Orbital Theory of Organic
Chemistry. McGraw-Hill, New York 1969.
[I41 U . Weidner and A. Schweig, J. Organometal. Chem., in press.
Sigmatropic [1,5]-Ester Migrations[**I
While this difference may or may not be solelv the coilsequence of a charge effect, more sensitive and more certain
information about the charge distribution may be obtained
from 13C-NMR ~pectra'~].
Thus comparison of the 13CNMR spectra of ( I ) and (3) (chemical shifts in ppm to
A6 = cl9ppm
Angew. Chem. internat. Edit. / Vol. 11 (1972j 1 No. 6
Dedicated to Professor B. Heyerich on his 85th birthday
There has recently been increasing interest in migration
of ester groups['] : Thus, sigmatropic [1,5]-ester migrations
on the 1,3-cyclohexadiene skeleton have been reported to
[*] Dr. P. Schmidt, Prof. Dr. R. W. Hoffmann,
and Dipl.-Chem. J. Backes
By Peter Schmidt, Reinhard W Hoffmann, and
Jutta Backes"'
Fachbereich Chemie der Universitat
355 Marburg, Lahnberge (Germany)
[**I This work was supported by the Verband der Chemischen
Industrie and the Max-Buchner-Forschungsstiftung.
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methylenenorbornadiene, bicycloheptafulvene
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