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Bridged [14]Annulenes with a Phenanthrene-Perimeter syn-1 6 7 12-Bismethano[14]annulene.

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according to the I3C-NMR spectrum, the constitution of
the product recovered is indeed that of the dipotassiurn dihydroacepentalenediide 22Q/2K@(Table l).[91But the assignment of the very weak signal of C-10 is not absolutely
certain because 22Q/2K@slowly decomposes in THF,
even at -40 "C, and hence signals of other products appear in the spectrum. An unequivocal proof of the constitution was, however, provided by the trapping reaction
with chlorotrimethylsilane. When a suspension of 22Q/
2Ke in n-hexane is stirred at room temperature for 48 h
with an approximately equimolar amount of Me3SiC1, decolorization of the mixture occurs, and, after the usual
work-up, a product can be isolated (60-70% yield based o n
1) in which two components with M , = 272 can be detected
by combined GC-MS. According to the 'H-NMR spectrum (Table 1) the components are the isomeric bis(trimethylsilyl)tricyclo[5.2.1.04~'o]decatetraenes 5 and 6 (ratio
61:39).
I
Me3SiC1
5
lMe3SiC'
6
It is especially remarkable that 6 is formed along with 5 ,
since the tricycl0[5.2.1.O~~'~]deca-1,3,5,8-tetraeneskeleton
of 6, according to force field calculations, is about 18.2
kcal/mol more strainedt4]than the skeleton of 5 , which is
easily accessible in the form of 4,7-bis(dialkylamino)derivative^.^^^ According to MNDO calculations the charge
distribution in dihydroacepentalenediide 2 2 o is best explained in terms of the structure a, a trisetheno-bridged
trimethylenemethane dianion; structure b plays only a
subordinate role.'31 Hence, the 4-trimethylsilyl anion 3
should be formed first in a kinetically controlled reaction
of Z Z Q with Me3SiC1; this could partially rearrange into
the thermodynamically more stable 10-trimethylsilyl anion
4 with a Ion-perimeter by 1,2- o r 1,5-silatropic
before it reacts further to give the bis(trimethylsily1) derivative. As expected, 5 is thermodynamically more stable than
6 ; under modified conditions 5 and 6 are formed in the
ratio 83:17 o r 1OO:O. The isomer 6 rearranges into 5 , rapidly upon MeSiC1-catalysis at room temperature, but at
best only slowly upon heating above 90 OC.['']
Received: March 24, 1986 [Z 1708 IE]
German version: Angew. Chem. 98 (1986) 734
720
0 VCH VerlagsgesellschaJi mbH, 0.6940 Weinheim. I986
CAS Registry numbers:
1 , 6053-74-3; 2, 103148-72-7; 5 , 103148-69-2; 6 , 103148-70-5
[ I ] Contrary to the IUPAC rules for nomenclature the dihydropentalenediide has often been called pentalenediide in the literature, cf. T. G.
Katz, M. Rosenberger, J. Am. Chem. SOC.84 (1962) 865.
[2] J. J. Stezowski, H. Hoier, D. Wilhelm, T. Clark, P. von R. Schleyer, J.
Chem. SOC.Chem. Commun. 1985. 1263.
131 H . Butenschon, A. de Meijere, Helu. Chim. Acta 68 (1985) 1658.
[4j Cf. H. Butenschon, A. de Meijere, Chem. Ber. 118 (1985) 2557.
[5] a) A. Streitwieser, Jr.: Molecular Orbital Theory for Organic Chemists,
Wiley, New York 1961, p. 290f.; b) R. Zahradnik, J. Michl, J. Koutecky,
CON. Czech. Chem. Commun. 29 (1964) 1932; c) R. Zahradnik, J. Michl,
ibid. 30 (1965) 3529; d) B. A. Hess, Jr., L. J. Schaad, J. Org. Chem. 36
(1971) 3418; e) F. Tomas, J. 1. Fernandez-Alonso, A n . Quim. 72 (1976)
122; f) 1. Gutman, N. Trinajstic, Croat. Chem. Acta 47 (1975) 35; g) I.
Gutman, M. Milun, N. Trinajstic, J. Am. Chem. SOC. 99 (1977) 1692.
[6] K. Mullen, H. Butenschon, A. de Meijere, unpublished, results.
171 Cf. L. Lochmann, J. Pospisil, D. Lim, Tetrahedron Lett. 1966, 257; cf. M .
Schlosser, S. Strunk, ibid. 25 (1984) 741.
[8] Analogous to the synthesis of numerous polyanions by metalation-elimination: D. Wilhelm, T. Clark, T. Friedl, P. von R. Schleyer, Chem. Ber.
I16 (1983) 751; D. Wilhelm, T. Clark, P. von R. Schleyer, Tetrahedron
Lerr. 23 (1982) 4077.
191 All experimental findings with other systems are consistent with the
presence of a dipotassium salt. Cf. D. Wilhelm, T. Clark, P. von R.
Schleyer, J. L. Courtneidge, A. G. Davies, J . Organomet. Chem. 273
(1984) CI.
[lo] According to MNDO calculations the 10-Me,Si anion 4 is about 2.9
kcal/mol more stable than the 4-Me3Si anion 3. Accordingly, 4 shows
hardly any bonding alternance in the lox-perimeter. T. Clark, unpublished results.
[ I l l This is surprising in view of the reports that the silatropic 1,5-shift o f
cyclopentadienes is lo6 times more rapid than the prototropic shift. C.
A. J. Asche 111, J. Am. Chem. SOC.92 (1970) 1233; S . McLean, G. W. B.
Reed, Can. J. Chem. 48 (1970) 3110; C. W. Spangler, Chem. Rev. 76
(1976) 187.
Bridged I14IAnnulenes with a Phenanthrene-Perimeter :
syn-1,6 :7,12-Bismethano[ 14]annulene**
By Emanuel Vogel,* Wilhelm Piittmann,
Walter Duchatsch, 7'homas Schieb, Hans Schmickler,
and Johann Lex
Dedicated to Professor Heinz A . Staab on the occasion
of his 60th birthday
The syn/anti-isomeric 1,6:8,13-bismethano[l4]annulenes
l1I1and 2['l with an anthracene-perimeter are exemplary
models for correlating aromaticity and molecular geometry.131O n the basis of spectral141and structural chemical criteria, the syn-isomer 1 clearly qualifies as an aromatic
compound, even though the annulene ring is noticeably
bent-mainly as a result of steric repulsion of the internal
bridge hydrogen atoms. In the anti-isomer 2, on the other
hand, the annulene ring is strongly puckered, so that the
cyclic n-electron delocalization can no longer be sustained,
and consequently 2 constitutes a highly reactive olefinic
molecule.
3,syn
4,anti
[*] Prof. Dr. E. Vogel, Dr. W. Piittmann, Dr. W. Duchatsch,
[**I
Dr. T. Schieb, Dr. H. Schmickler, Dr. J. Lex
lnstitut fur Organische Chemie der Universitat
Greinstrasse 4, D-5000 Koln 41 (FRG)
This work was supported by the Deutsche Forschungsgemeinschaft
0570-0833/86/0808-0720 $ 02.50/0
Angew. Chem. Int. Ed. Engl. 25 (1986) No. 8
A similar geometrically induced loss of aromaticity as
observed with 1 / 2 should, according to model considerations, occur in the case of the syn/anti-isomeric 1,6:7,12bismethano[ 14lannulenes 3 and 4 derived from phenanthrene. The annulene ring of 3 appears to be more deformed than that of its counterpart 1, yet aromatic character should still be associated with 3, since the torsional angles of the CC bonds d o not exceed values of 40-50°.[51 In
the case of 4 the annulene ring is puckered to about the
same extent as that in 2, so one can safely assume that 4 is
also olefinic.[” The experimental verification of this concept is the subject of this and the following communication.”]
The stepwise coupling of terminally suitably substituted
cycloheptatrienes, preferentially of-hitherto unknown6-halogeno-1,3,5-cycloheptatriene-l-carboxylic
acid derivatives (cf. 7), promised a relatively simple entry to 3 and/
o r 4. Using this strategy we succeeded, first of all, in synthesizing the syn-1,6:7,12-bismethano[l4]annulene 3,
which, because of non-bonding interactions between the
internal bridge hydrogen atoms, is a sterically very demanding species.
As cycloheptatriene synthetic building block we chose
6-iodocycloheptatriene-1-carbonitrile7. The preparation
of 7 was based on our previous observation that cyclopropabenzene 5Ix1upon reaction with iodine affords 1,6-diiodocycloheptatriene 6.[8“1As the yield of 6 reached in the
original procedure is maximally 5%, advantage had to be
taken of the efficient synthesis of 5 by B i l l ~ p s and
[ ~ ~ of
] the
finding that the iodination of 5 is a radical process optimizable by UV irradiation.[’] 6 is thus accessible on a preparative scale.
under high dilution conditions (the more advantageous
method) o r with tungsten hexachloride/butyllithium,[’219
undergoes annulene ring closure to give, surprisingly, the
syn-isomer 3 stereoselectively in both cases (yield 35-40%
and lo%, respectively). After work-up by chromatography
on alumina (Brockmann act. IV; pentane) the annulene 3,
which is air-stable, is recrystallized from pentane thus furnishing orange-colored rhombs of m. p. 93-94 “C.
The ‘H-NMR spectrum of 3 (see Fig. 1 and Table 1)
indicates-as would be expected for an aromatic compound-the presence of a diamagnetic ring current (signals for the annulene and bridge protons at relatively low
and high field, respectively), which, however, is weaker
than that in 1, and even more so than that in bridged
[14]annulenes with essentially planar annulene rings. Comparison of the mean positions of the signals of the annulene protons of 3 (6=7.19), l (7.59) and 4[’] (6.45)places
3 intermediate between 1 and 4, which according to all its
a)
!
b)
2.64
6
5
NC
1.70
7
I
1
I
1
9
8
7
6
9
3
I
4
I
I
I
3
2
1
I
I
0
-
1
Fig. 1. ‘H-NMR spectra of a) syn-1,6.7,12-bismethano[14]annulene3 and b)
anti-1,6:7,12-bisrnethano[
14jannulene 4 (300 MHz, CD,CI,).
4
Upon heating the diiodide 6 together with copper(])
cyanide (molar ratio 1 :1) in dimethylformamide (DMF) at
120 “C (6 h) a mixture of 7 and 1,6-~ycloheptatrienedicarbonitrile[” was obtained, from which 7 could be readily
separated by chromatography on silica gel (pentanelether
3:l) [colorless rhombs (from pentane/ether 1 :l); m.p.
73 “C; yield 28%]. When 7 is slowly added to the NiO-reagent prepared from bis(triphenylphosphane)nickel(ii)
chloride, triphenylphosphane and activated zinc in
DMF,[Io1reductive CC coupling with formation of the dinitrile 8 is achieved [m.p. 188-189°C; yellow needles
(from methanol); yield 69%]. Reduction of 8 with diisobutylaluminum hydride (DIBAH) in toluene smoothly affords the dialdehyde 9 [m. p. 132 “ C ; orange-colored needles (from ether); yield 82%]. Upon reaction with titanium
tetrachloride/zinc/pyridine[”] in tetrahydrofuran (THF)
Anyew Chrm. In!. Ed. Engl. 25 (1986) N o 8
I
5
-6
CHO
OHC
CN
8
i
2.35
Table I. ‘H-NMR data (6 values and vicinal coupling constants [Hz]) of the
bridged [14]annulenes 3 and 4 and of phenanthrene [a] at 300 MHz in
CD2CI2.
3
4
Phenanthrene
3
4
Phenanthrene
H-2
H-3
H-4
H-5
H-13
H-15a
H-15i
6.91
6.23
7.06
6.67
7.27
6.69
7.52
6.26
7.18
6.40
-0.37
1.70
2.35
2.64
7.99
7.71
7.75
8.76
7.84
-
-
6.96
5.94
10.26
11.03
7.1 1
5.27
11.8
11.2
8.00
7.04
8.44
8.8
[a] For comparison, the annulene nomenclature has been used for phenanthrene. The NMR analysis was carried out in connection with this work; for
data published earlier, see R. C. Fahey, G. C. Graham, J . Phys. Chem. 69
(1965) 4417. [b] The J(13,14) coupling could be determined from the ”Csatellites of the ‘H-resonance.
0 VCH Verlagsgesellschafi mbH. 0-6940 Weinheim. 1986
0570-0833/86/0808-0721$ 02.50/0
72 1
properties is to be regarded as a purely olefinic compound.
3 also-takes a position between 1 and 4 with respect to the
ratio of the vicinal coupling constants 3JH,H, that is a
measure of the degree of bond
From the
33H.H values it can be concluded that of the two nonequivalent resonance structures of the annulene 3 that with cycloheptatriene units has special weight. This finding conforms with the observation that the n-bonds in the olefinic
species 4 are localized as shown in the structural formula.[71The downfield position of the signals of the internal
bridge protons (H-15, H-16i) of 3 must largely be due to a
proximity effect, which, as inferred from the analogous
case of 1, should cause a deshielding of the order of 1-2
ppm.[']
The electronic spectrum of 3 (in cyclohexane, see Table
2) is of the same type as that of benzene and as the spectra
' ~ ~ from the
of other delocalized [4n 2 1 a n n ~ l e n e s . ~Apart
extinction of the most intense band being reduced and the
longest wavelength band being relatively weak, it closely
agrees with the spectrum of 1, whereas it is markedly different1l5Ifrom the spectrum of its anti-isomer 4 .I7]
The X-ray structure
of 3 (Fig. 2) not only
provides unequivocal proof of the syn arrangement of the
bridges, but also confirms the conclusion drawn from
models that x-orbital overlap in the annulene ring is less
favorable in 3 than in 1 . Torsional angles of u p to 45" are
observed for the C C bonds of the ring, as compared to 34"
for those in 1 and 84" for those in 4.I7l The bond alternation ensuing from the coupling constants 3JH,H locally varies in its degree quite noticeably. In the cycloheptatriene
units the alternation lies within the range of lengths for
aromatic CC bonds, whereas in the ring segment C12-Cl3C14-CI it approximates to those in polyenes, such' as the
anti-isomer 4. This dichotomy apparently has its origin in
the steric forces which the repulsion of the internal bridge
hydrogen atoms (H,H distance ca. 1.87 A) imposes on the
annulene ring.
+
,-
Fig. 2. Molecular structure of 3 in the crystal; selected-bond lengths [A].
Transannular CC distances: CI . . . C 6 s C 7 . . . C12 2.336 A; bridge bond an- C I ~(mean values for the four indepengles: C I - C I ~ - C ~ G C ~ - C I ~102.6"
dent molecules in the unit cell).
From the investigations on the x-electron structure of
3 one arrives at the conclusion that the physical methods
employed-especially
'H-NMR spectroscopy, electron
spectroscopy and X-ray structure analysis-respond with
different sensitivity to the steric hindrance of resonance in
3 and other nonplanar (4n + 2)n-electron systems.
The availability of 3 stimulated attempts to use this hydrocarbon, in analogy to the conversion of 1,6-methano[ IOIannulene to cyclopropabenzene,[*"I for a synthesis of
the extremely strained di(cyc1opropa)benzene 10. The target molecule, however, did not materialize since 3 reacts
722
0 VCH Verlagsgesellschaft mbH. 0-6940 Weinherm. 1986
6
NC
-CH2
~
CN
CH -
-
10
11
with acetylenedicarbonitrile (DCA) (in boiling acetone)
with formation of 11 [decomp. above 235°C; yellow
rhombs (from chloroform); yield SS%].
Table 2. Some spectral data of the new compounds. ' H - N M R : 300 MHz,
"C-NMR: 75.5 MHz, both in CDC13 (exception: 3 in CD,CI,); MS: 70 eV;
UV/VlS in dioxane (exception: 3 in cyclohexane).
3 : 'H-NMR see Table I : "C-NMR: 6=33.51, 113.97. 115.98, 127.78, 128.27,
129.04, 130.53, 131.53; MS: m / z 206 (Me,
72%). 191 (100); IR (Csl): 3030,
nm (&=8300),300 (47 loo), 367 (7400),
1573, 1488 c m - ' ; UV/VIS:A,,,=245
450 (340) sh
7 : 'H-NMR: 6 = 3.14 ( s , 2 H). 6.49 (dd, 1 H), 6.57 (dd, 1 H), 6.82 (d, I H), 6.90
(d, I H); "C-NMR: 6 ~ 4 4 . 3 3 .83.89, 100.56, 118.80, 128.53, 136.07, 137.59,
138.59; MS: m / z 243 (Me,
7%), 116 (100); I R (KBr): 2198 (C=N) c m - ' ;
UV/VIS: A2,,,=320 nm (&=4500)
8 : 'H-NMR: 6=2.82 ( s , 4H), 6.62 (dd, 2H). 6.71 (d, 2H), 6.87 (d, 2H), 6.95
(dd, 2H); "C-NMR: 6=31.97, 102.20, 119.08, 125.14, 128.98, 132.87, 136.07,
138.53; MS: m / z 232 (Me,
lOO%), IR (KBr): 2204 (C=N) crn-'; UV/VIS:
A,, = 237 nm (&= 54400), 294 (3600), 377 ( 1 1400)
9:'H-NMR:6=2.79(~,4H),6.74(dd,2H),6.95(d,2H),7.01(dd,2H),7.10
(d, 2H), 9.42 ( s , 2H); "C-NMR: 6=25.70, 124.43, 128.86, 132.58, 135.23,
137.14, 142.02, 191.19; MS: m / z 238 (M', 97%), 165 (100); 1R (Csl): 1662
(C=O) c m - ' ; UV/VIS: A2,,,,=245 nm (&=49500), 305 (3400). 410 (9300)
11: ' H - N M R : 6 = 1.33 and 3.54(AX,4H, '1'- 11.71 Hz), 6.06(d, 2H),6.72
( s , 2H), 7.07 (dd, 2H), 7.88 (d, 2 H ) ; "C-NMR: 6=34.52, 110.09, 115.05,
124.20, 126.59, 128.53, 130.44, 132.29, 134.23, 138.15; MS: m / z 280 (Me,
88%), 265 (100): IR (KBr): 2220 (C=N) c m - ' ; UV/VIS: A,.,,=223 nm
(&=41 IOO), 280 (29600), 325 (10300) sh
Received: March 17, 1986 [Z 1703 IE]
German version: Angew Chem. 98 (1986) 727
CAS Registry numbers:
3, 85385-68-8; 5,4646-69-9; 6 , 4642-24-4; 7 , 103148-65-8; 8, 103148-66-9; 9,
103148-67-0; 11, 103148-68-1; 1,6-~ycloheptatrienedicarbonitrile
73172-88-0;
acetylenedicarbonitrile (DCA) 1071-98-3.
[I] a) E. Vogel, J. Sombroek, W. Wagemann, Angew. Chem. 87 (1975) 591 ;
Angew. Chem. Int. Ed. Engl. 14 (1975) 564; b) for the X-ray structure
analysis, see: R. Destro, T. Pilati, M. Simonetta, Actu Ciystallogr. B33
(1977) 940; c) the transition from 1 to syn-l,6-ethano-8,13-methano[l4]annulene is-analogously to that from 1 to 2-associated with a
loss of aromaticity: E. Vogel, H. M. Deger, P. Hebel, J. Lex, Angew.
Chem. 92 (1980) 943; Angew. Chem. I n / . Ed. Engl. 19 (1980) 913; H.
Giinther, H . von Puttkamer, H. M. Deger, P. Hebel, E. Vogel, ibid. 92
(1980) 944 and 19 (1980) 921; d ) the question as to how the n-orbital
conjugation in a bridged annulene is influenced by rehybridization has
recently been investigated by R. C. Haddon, L. T. Scott, Pure Appl.
Chem. 58 (1986) 137.
[2] a ) E. Vogel, U. Haberland, H. Giinther, Angew. Chem. 82 (1970) 510;
Angew. Chem. lnt. Ed. Engl. 9 (1970) 513; b) X-ray structure analysis of
the 7-carboxylic acid methyl ester of 2 : C. M. Gramaccioli, A. S. Mirnun,
A. Mugnoli, M. Sirnonetta, ./ Am. Chem. SOC.95 (1973) 3149; M. Simonetta, Pure Appl. Chem. 52 (1980) 1597.
[3] 1 and 2 are conformationally stable even at 400°C in the gas phase
(flow apparatus).
[4] J. Dewey, H. M. Deger, W. Frolich, B. Dick, K. A. Klingensmith, G.
Hohlneicher, E. Vogel, J. Michl, J . Am. Chem. SOC.102 (1980) 6412.
[5] 1,5-Methano[l0]annulene may be regarded as an extreme case of a deformed [4n +2]annulene still qualifying as aromatic according to spectroscopic criteria: a) S. Masamune, D. W. Brooks, Tetrahedron Lett. 1977.
3239; b) L. T. Scott, W. R. Brunsvold, J Am. Chem. SOC. 100 (1978)
4320; c) for the resonance energy of bridged [IO]annulenes, see: W. R.
Roth, M. Bohm, H.-W. Lennartz, E. Vogel, Angew. Chem. 95 (1983)
1011; Angew Chem. Int. Ed. Eng1. 22 (1983) 1007; Angew. Chem. Suppl.
1983. 1379.
[6] a) Irrespective of their configuration (cis or trans), the bridged [14]annulenes with "pyrene perimeter" art' aromatic: V. Boekelheide, J. B. Phillips, J . Am. Chem. SOC.85 (1963) 1545: 89 (1967) 1695; R. H. Mitchell,
V. Boekelheide, ibid. 96 (1974) 1547; R. H. Mitchell, T. K. Vinod, G. J.
0570-0833/86/0808-0722 $ 02.50/0
Angew. Chem. Int. Ed. Engl. 25 (1986) No. 8
Bodwell, K. S. Weerawarna, W. Anker, R. V. Williams, G. W. Bushnell,
Pure Appl. Chem. 58 (1986) 15; b) the same holds for the bridged [14]annulenes with "azupyrene perimeter" (annelated systems of two azulene
units): W. Huber, J. Lex, T. Meul, K. Miillen, Angew. Chem. 93 (1981)
401: Angew Chem. In/. Ed. Engl. 20 (1981) 391; W. Huber, W. Irmen, J.
Lex, K. Mullen, Tetrahedron Lett. 23 (1982) 3889.
[7] E. Vogel. T Schieb, W. H. Schulz, K. Schmidt, H. Schmickler, J. Lex,
Anyew Chem. 98 (1986) 729: Angew. Chem. In/. Ed Engl. 25 (1986)
723.
[S] Cyclopropabenzene syntheses: a) E. Vogel, W. Grimme, S. Korte, Tetrahedron Lett. IY65, 3625; b) W. E. Billups, A. J. Blakeney, W. Y . Chow,
Chem. Commun. 1971. 1461; Org. Synth. 55 (1976) 12.
[9] R. Okazaki, M. 0 - o k a , N. Tokitoh, Y. Shishido, N. Inamoto, Angew.
Chem. 93 (1981) 833: Angew. Chem. Int. Ed. Engl. 20 (1981) 799.
[ 101 a) A. S. Kende. L. S. Liebeskind, D. M. Braitsch. Tetrahedron Lett. 1975,
3375: b) M. Zembdyashi, K. Tamao, J. Yoshida, M. Kumada, rbid. 1977.
4089: c ) R. H. Mitchell, M. Chaudhary, T. W. Dingle, R. V. Williams, J.
Am Chem. Soc. 106 (1984) 1776. and references cited therein.
1111 a ) T. Mukaiyama, T. Sato, J. Hanna, Chem. Lett. 1973. 1041; b) J . E.
McMurry, M . P. Fleming, J . Am. Chem. Soc. 96 (1974) 4708; J . E.
McMurry, Acc. Chem. Res. 16 (1983) 405: c) D. Lenoir, Synrhesis 1977,
553. We thank W H. Schulz for the optimization of the reductive coupling of 9 with titanium tetrachloride/zinc/pyridine.
1121 a) K. B. Sharpless, M. A. Umbreit, M. T. Nieh, T. C. Flood, J. Am.
Chem. SOC.94 (1972) 6538: b) E. Vogel in H. Nozaki (Ed.): Current
Trend.s in Organic S-wthesis. Pergamon Press, Oxfotd 1983, p. 379.
[I31 H Ciinther, Tetrahedron Lett. 1967. 2967. The statements about the
bond alternation in 3 still hold when taking into account the dependence of the coupling constants 'JH.H on the dihedral angle; see hereto:
M. Karplus, J . Am. Chem. Soc. 84 (1962) 2458.
[I41 H.-R. Blattmann, W. A. Boll, E. Heilbronner, G. Hohlneicher, E. Vogel,
JLP. Weber, Helu. Chim. Acta 49 (1966) 2017.
[ 151 Electronic spectra of 3 and 4 : B. Boersch-Pulm, M. Demmer, P. S. Murthy, J . Lex, T. Schieb, G. Hohlneicher, J. Michl, E. Vogel, J. Am. Chem.
Soc.. submitted for publication.
1161 3 crystallizes in the triclin-ic system; space group PI, 0=9.503(1),
h= lI.210(l), c=21.919(1) A, a=84.31(1), /7=83.27(1), y=76.53(1)",
Z = 8 ; 6716 reflections, R=0.052. Further details of the crystal structure
investigation are available on request from the Fachinformationszentrum Energie, Physik, Mathematik GmbH, D-7514 Eggenstein-Leopoldshafen 2, on quoting the depository number CSD-51939, the names o f the
authors, and the full citation of the journal.
Bridged I141Annulenes with a Phenanthrene-Perimeter :
anti-1,6 :7,12-Bismethano[l41annulene**
By Emanuel Vogel, * Thomas Schieb, Wolfgang H . Schulz,
Klaus Schmidt, Hans Schmickler, and Johann Lex
The syn-1,6:7,12-bismethano~l4]annulene1 derived
from phenanthrene, a bridged [14]annulene with a
markedly bent annulene ring, is kind of a borderline case
of an aromatic molecule regarding its n-electron structure."] In the case of the still unknown anti-1,6:7,12-bismethan01 14lannulene 2 the predictions are that one is dealing
with a n olefinic molecule since, according to models, 2
possesses a puckered annulene ring in which the CC bonds
are, in part, strongly twisted (maximum torsional angle 8085 "). Following the successful synthesis of
we are
now also able to report the synthesis of 2.
1
CO,CH,
8
[*] Prof. Dr. E. Vogel, Dr. T. Schieb, W. H. Schulz, K. Schmidt,
Dr. H. Schmickler, Dr. J. Lex
lnstitut fur Organische Chemie der Universitat
Greinstrasse 4, D-5000 Koln 41 (FRG)
This work was supported by the Deutsche Forschungsgemeinschaft
Anyew Chrm I n t . Ed Engl 25 (1986) No 8
j?
1
G 3O COOH
o H
H3C0,C
2
~
[**I
The surprising observation that reductive coupling of
1,l '-bis(~ycloheptatrienyl)-6,6'-dicarbaldehydeexclusively
affords the syn-isomer 1 suggested the idea of approaching
2 by way of its dihydro derivative 1 1 . Compound 11
should be formed, albeit not necessarily stereoselectively,
by reductive cyclization of 6,6'-bis(bromomethyl)- 1,l'bis(cycloheptatrieny1) 9.
The diester 8 could be obtained-more advantageously
than via the cyclopropabenzene route"]-from the readily
accessible cycloheptatriene-l,6-dicarboxylic acid 3,"'
either A) via the dicarboxylic acid dichloride 4, or B) via
the methyl half ester 6Izb1(Scheme
Route A): The
compound 4 (m. p. 63 " C ;yield SO%), prepared by reaction
of 3 with sulfinyl chloride, undergoes selective monodecarbonylation on heating with tris(tripheny1phosphane)rhodium(r) chloride[41as catalyst to give 6-chlorocycloheptatriene-1-carboxylicacid chloride, which after distillation from the reaction mixture is allowed to react with
methanol yielding 5 . Upon chromatographicisolation(silica
gel, ether/pentane l:9), 5 is obtained as an NMR-spectroscopically pure oil, so that for practical purposes a distillation (yellowish liquid of b. p. 62-63 " U 0 . 2 torr;
m. p. 26 " C ; yield 65%) is not required. Treatment of 5
with bis(triphenylphosphane)nickel(Il) chloride (catalytic
amounts) and zinc in tetrahydrofuran (THF) in the presence of tetraethylammonium iodide,Is1 brings about reductive CC coupling to give 8, which after purification by
chromatography (silica gel, ether) and recrystallization
(from methanol) is obtained in the form of yellow rhombs
(m.p. 126-127 " C ; yield 70%). Route B): The half ester 6,
best prepared by hydrolysis of the dimethyl esterlZh1with
aqueous methanolic sodium hydroxide (yield 450/0), can
be decarboxylatively brominated to 7 according to the
method of Barton"] (an alternative to the Hunsdiecker degradation) in that it is converted by reaction with N-hydroxypyridine-2( 1 H)-thione and dicyclohexylcarbodiimide
into the thiohydroxamic ester and the latter then heated in
bromotrichloromethane. After isolation by chromatography (silica gel, ether/pentane I :9) and subsequent distillation, 7 is collected as a yellowish liquid (b. p. 75-76 "C/O. 1
torr; m.p.= 22 " C ; yield 48%). Reductive coupling of 7,
carried out as in the case of 5, affords 8 in 70% yield (no
increase in yield on going from the chloro to the bromo
&H,C
CH,Br
9
Scheme I . A, B see text. a : SOC12, CH2Cl2, reflux, 8 h ; b: tris(tripheny1phosphane)rhodium(~)chloride (Wilkinson catalyst), 165 "C, 3 h; c : methanol, CH2C12, RT, I h ; d : NaOH, methanol/water, RT, 24 h: e : N-hydroxypyridine-2( Ihl)-thione, dicyclohexylcarbodiimide,CBrCli, 120 "C, 4 h: f :
bis(triphenylphosphane)nickel(~~)chloride, tetraethylammonium iodide, Zn,
THF, RT, 18 h; g: DIBAH, ether, RT, 1 h: h : PBr,, pyridine, benzene, 70°C.
5 h.
0 VCH Verlagsgesellschafi mbH. 0-6940 Wemherm, 1986
0570-0833/86/0808-0723
$
!
02.5010
723
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annulenes, phenanthrene, syn, annulene, bridge, perimeter, bismethano
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