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Bridged Hetero[11]annulenes.

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reported photochemical behavior of diethyl trans,trans-ophenylenedia~rylate'~~,
Received: NoLember 8, 1971 [Z 550 IE]
German version. Angew. Chem. 84,206 (1972)
[I]R . J . Spungler and J . C . Sutton, unpublished.
[2] H . A . Staab and J . Ipaktschi, Chem. Ber. IOI, 1457 (1968).
[3] Prepared by the method of M . P . Caca and R. J. Pohl, J. Amer.
Chem. SOC.82, 5242 (1960).
[4] The stereochemistry about the double bonds of (3) has been
determined to be anti,anti: R . J . Spungler and J . C. Sutton, unpublished
[5] D.F . Tacares and W H . Plodder, Tetrahedron Lett. 1970, 1567.
[6] E . M i l l e r , H . Meier, and M . Sauerbier, Chem. Ber. 103,1356 (1970).
[7] J . Meinwald and J . W Young, J. Amer. Chem. SOC.93, 725 (1971).
[8] R. B. Woodward and R. Hoffmann: The Conservation of Orbital
Symmetry. Verlag Chemie GmbH, Weinheim/Bergstr. 1970, pp. 73, 74.
Bridged Hetero[ll]ann~lenes[~~
By Emanuel Vogel, Ruiner Feldmann, Helmut Diiwel,
Hans-Dieter Cremer, and Harald Giinther[*I
Advances in annulene chemistry have recently encouraged
a number of research teams to take up the study of heteroannulenes having medium and large rings, especially the
homologs of furan, pyrrole, and thiophene[']. Since the
members of homologous heteroannulene series, like the
simple annulenes, differ considerably in conformation and
mobility of the ring skeleton, attempts to establish correlations between physical and chemical properties of the
respective compounds meet with difficulties. In the case of
heteroannulenes having medium-sized rings, a planar
skeleton desirable for comparative studies seems attainable
only by introduction of bridges or triple bonds.
The present communication describes the bridged hetero[ll]annulenes 4,9-methanothia[ll]annulene ( I a ) and
-oxa[ll]annulene ( I b ) , which can be regarded as potential 12n-electron systems. These compounds can adopt
conformations with an approximately planar heteroannulene ring while incurring only a moderate degree of
ring strain ;however, owing to lack of resonance stabiIization they are likely to prefer the almost strain-free conformations with the hetero atom syn or anti to the bridge
[(Za) and ( 2 b ) ; (3a) and ( 3 b ) l .
4,9-Methanothia[Il]annulene ( I a) was synthesized by a
Wittig reaction : Cycloheptatriene-1,6-dialdehyde( 4 ) 13] in
dimethylformamide was allowed to react for 24 h at room
temperature with thiodimethylenebis(tripheny1phosphonium bromide) ( 5 a ) and lithium methoxide as a base
[*] Prof. Dr. E. Vogel, Dr. R. Feldmann, Dr. H. Diiwel,
Dip].-Chem. H.-D. Cremer, and Prof. Dr. H. Giinther
Institut fur Organische Chemie der Universitat
5 Koln 1, Zulpicher Strasse 47 (Germany)
Angew. Chem. internat. Edit. Vol. 1 I (1972) 1 N o . 3
(added in methanol to the reaction mixture). Compound
( I a), isolated in 30% yield as red crystals (m. p. 27-28"C,
from ethanol), underwent a fairly rapid change above
50°C, partly decomposing to 1,6-methano[lO]annulene
( 8 ) and sulfur[41and partly polymerizing.
4,9-Methanooxa[I Ilannulene ( I b) could be obtained
similarly to ( l a ) , albeit in only 2% yield, by reaction of
(4) with (5b) ;the oxa compound is an air-sensitive yellow
liquid (b. p. z 7OaC/0.1 torr) best kept in an argon atmosphere.
The hetero[ll]annulene structures (1 a ) and ( I b) of the
two compounds were proved by their NMR spectra, which
also provided evidence favoring the syn conformations
(2a) and ( 2 b) [51.
The NMR spectrum of ( I a) (in CCl,) (Fig. 1a) shows an
AAXX' system at r=3.46 (H-6, H-7) and 3.91 (H-5, H-8)
for the heteroannulene protons of the cycloheptatriene
part of the molecule, an AX system at T = 3.55 (H-3, H-10)
and 5.22 (H-2, H-11) with J=9.6Hz16] for those in the
vicinity of the sulfur atom, and an AX system at r=3.72
(H-12b) and 8.76 (H-12a) with J = - 11.5 Hz for the bridge
protons. The A part of the bridge-proton AX system, which
is superposed on the absorption of the heteroannulene
protons (see Fig. la), was located by double resonance.
The possibility of ( l a ) being in rapid equilibrium with a
significant quantity of its 1,6-methano[lO]annulene 3,4episulfide valence tautomer (7) can be ruled out since a)
the NMR spectrum shows no temperature dependence
and b) the heteroannulene protons of the cycloheptatriene
part exhibit practically the same chemical shifts and coupling constants (J5,,=5.78, J6,7=10.38, J5.,=0.3O, J5.8
= 1.29Hz) as the corresponding protons ofthe hydrocarbon
bicyclo[5.4.l]dodeca-2,5,7,9,ll-pentaene (6) [ 3 . 71 (Fig. 1c).
From the remarkable agreement in chemical shifts shown
by the protons of the cycloheptatriene parts of (1 a) and
( 6 ) it follows that ( I a) does not sustain a significant paramagnetic ring current. The resonance of the bridge proton
H-12 b at exceptionally low field-difference in chemical
shifts between H-12b and H-I2a=5 ppm!-is only in
apparent discord with the above observations and is readily
explained by the combined effects of the diamagnetic anisotropy of the S-C bonds['], the field effect of the sulfur
atomtg1,and possibly also a steric compression['01 of the
sulfur atom and the bridge proton H-12 b, assuming that
the molecule adopts the syn conformation ( 2 a ) .
The UV spectrum of ( I a) with maxima at 233 ( E = 31 200),
284 (27000), and 395 nm (427) (in cyclohexane) differs
markedly from that of the hydrocarbon ( 6 ) ,thus indicating
that the sulfur atom electronically interacts with the double
bond system in spite of the clearly non-planar arrangement
of the heteroannulene ring.
In its NMR spectrum (CCl,) (Fig. 1b), and specifically
with regard to the bridge-proton absorption, 4,9-methanooxa[l I]annulene ( I b) occupies an intermediate position
between ( I a ) and (6). The spectrum of the oxa compound
contains an AAXX' system at T = 3.33 (H-6, H-7) and 3.85
(H-5,H-8)(J5,, = 5.96, J6,7
= 10.54,J5,7
=0.08,J5,, = 1.51Hz),
an AX system at z=4.29 (H-3, H-10) and 4.52 (H-2, H-11)
with J=6.2 Hz, as well as another AX system at T = 5.48
(H-12b) and 9.37 (H-12a) with J = - 10.4 Hz. Remarkably,
326 370
-tlppml -L-
Fig. 1. NMR spectra of a) 4,9-methanothia[ll]annulene ( l a ) , b) 4,9methanooxaC1l]annulene (1b ) ,and c) bicyclo[5.4.l]dodeca-2,5,7,9,11pentaene (6) in CCI, (60 MHz; TMS as internal standard).
the difference between the chemical shifts of the bridge
protons decreases by 1.2 ppm on going from ( I a ) to ( 1 b).
From analogies with comparable compounds[' 'I the
magnitude of this decrease suggests that ( l a ) and ( I b )
have similar conformationsi"'.
The UV spectrum of ( I b), which exhibits maxima at 248
328 nm (2450) (in cyclohexane), is almost
superimposable with that of the hydrocarbon (6). It therefore follows that ( I b) and (6) definitely belong to the same
(E = 39200) and
conformational type and, furthermore, that the oxygen
not transmit
function in ( I b)-as in oxonin'*"'-does
cyclic conjugation.
Elimination of sulfur from
above 50°C most
probably proceeds via the hitherto undetected 1,6-methano218
[IOlannulene 3,4-episuIfide (7) formed by a symmetry
allowed electrocyclic process. Attempts to trap (7) with
dienophiles were unsu~cessful~~~1.
Received: November 15,1971 [Z 552a IE]
German version: Angew. Chem. 84,207 (1972)
[l] Based on a lecture by E . Vogel at the XXIII IUPAC Congress,
Boston, Mass., July 1971.
[2] a) Hetero[9]annulenes: A . G. Anastassiou, S . W Eachus, R . P. Cellura, and J . H . Gebrian, Chem. Commun. 1970, 1133, and further
literature cited therein pertaining to the work of this research group;
S. Masamune, S . Takada, and R . T Seidner, J. Amer. Chem. SOC.91,7769
(1969); S. Masamune, K . Hojo, and S. Takada, Chem. Commun. 1969,
1204; b) fused or alkylated thia[ll]- and thia[13]annulenes: A . 8.Holmes and F . Sondheimer, J. Amer. Chem. SOC.92, 5284 (1970); Chem.
Commun., in press; c) hetero[l7]annulenes: G. Schroder, G. Heil,
R. Neuberg, G. Plinke, and J . F. M . 0 t h : lecture by G. Schroder at the
XXIII IUPAC Congress, Boston, Mass., Juiy 1971.
[3] E. Vogel, R. Feldmann, and H . Diiwel, Tetrahedron Lett. 1970,1941.
[4] This reaction corresponds to the elimination of sulfur from thiepines; J . M . Hoffman j r . and R. H . Schlessinger, J. Amer. Chem. SOC.
92, 5263 (1970), and further literature cited therein.
[5] Further studies designed to settle the question of the conformations of (Ja), ( I b ) , and (6) are still in progress.
[6] In contrast to the situation in a,O-unsaturated thioethers, the
protones a, a' to the sulfur atom in (10) absorb at higher field.
[7] For the NMR analysis of (6) see K . Miillen, Dissertation, Universitat Basel 1971 ;cf. W Grimme, J . Reisdofl, W Jiinemann, and E. Vogel, J. Amer. Chem. SOC.92, 6335 (1970), footnote 13. Regarding the
coupling constants of the olefinic protons in 1,3-~yclohexadienesand
cycloheptatrienes, see H. Giinther and H . H . Hinrichs, Liebigs Ann.
Chem. 706, l(1967).
[8] For examples, see M . Tomoeda, M . Inuzuka, and T Furuta, Tetrahedron Lett. 1964,1233,
191 A . D.Buckingham, Can. J. Chem. 38, 300(1960).
[lo] S . Winstein, P . Carter, F. A . L. Aner, and A . J . R . Bourn, J. Amer.
Chem. SOC.87, 5247 (1965).
[ i l l C. R. Johnson and D.C. Vegh, Chem. Commun. 1969, 557; P. T
Lansbury, Accounts Chem. Res. 2, 210 (1969).
[I21 The large difference in the resonances of the bridge protons,
which is also observed in the NMR spectrum of (6), appears unusual. A discussion of the spectrum will appear elsewhere.
[13] After completion ofthe present manuscript, DipLChem. M . Mann
succeeded in synthesizing 1,6-methano[l2]annulene, an orange-red
compound of m. p. 30-31 "C that is isoelectronic with ( l a ) and ( I b ) .
The NMR spectrum (CCI,) of the hydrocarbon shows an AAXX'
system at ~ = 3 . 8 5and 4.29 as well as a narrow multiplet at ~ = 4 . 5 2
for the annulene protons and an AX system at T = 3.00 and 7.72 with
J = - Z 1.4 Hz for the bridge protons.
2-Hydroxy-4,9-methano[ 1l]annulenone,
a 10 x-Electron Analog of Tropolonef"
By Josef Reisdor-and Emanuel Vogeli*'
Identification of the 1,6-methano[ll]annulenium ion
( I ) [ z ]as an aromatic Ion-electron analog of the tropylium
ion suggested the interesting possibility that keto- and
ketohydroxy derivatives of ( I ) might exhibit physical and
chemical properties similar to those of tropone and tropolone, respectively. As recently reported, this expectation
was impressively confirmed for the keto derivatives of ( I )
(five structural isomers in all) by the synthesis of 4,9-methano[ll]annulenone (2)13' and of the isomeric 3,8- and
2,7-methan0[11]annulenones~'~. We now wish to describe
the preparation of 2-hydroxy-4,9-methano[l l]annulenone
(3),one of 36 possible isomers, whose properties justify its
being regarded as a Ion-electron analog of tropolone.
[*] Dr. J. Reisdorff and Prof. Dr. E. Vogel
Institut f i r Organische Chemie der Universitat
5 Koln 1, Ziilpicher Strasse 47 (Germany)
Angew. Chem. internal. Edit.
VoI. 11 (1972) No. 3
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annulenes, bridge, hetero
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