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Dibenzo[fg mn]octalene and Cycloocta[def]phenanthrene.

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Table 2. 'H[6,,]- and ''C[&]-NMR chemical shifts of I , Li21, and Lidl [a].
T ["CI
H2-H7,
H2'-H7'
5.68-5.55
5.75-5.53
5.72-5.40
5.66-5.20
5.67-5.45
C I , C8
H9a'. H9b'.
Hlla', H l l b '
2.36 (s)
2.42 (AB), 2.25 (AB)
2.42 (s)
2.38 (AB)
3.48 (5)
3.53 (s). 3.33 (s)
3.52 (s)
CI', C8'
C2-C7
98.7
133.2, 132.7, 132.1
133.6, 133.2, 131.1
87.0, 86.7, 85.0
86.7, 85.7, 85.0
140.5
141.3
99.3
H9a, H9b,
Hlla, Hllb
C2' -C7'
c 9 , c11
C9', C11'
CIO
52.0
48.3
47.4
45.9
52.2
60.7
59.9
[a] [Da]THF; 200 MHz ('H), 50 MHz ("'2)
excess charge remains localized in a single eight-membered ring and, as a consequence, a charged and a neutral
71-unit are present alongside each other. The equivalence of
H9a and H1 l a and non-equivalence of H9a' and H1 la' observable at - 60°C points to planarity of the charged eightmembered ring and the tub conformation of the uncharged
eight-membered ring (Scheme 2). Above 10°C, a rapid inversion of the uncharged ring, recognizable by the coalescence of the signals of H9a' and Hlla', takes place. No
change in the I3C-NMR spectra is observed on heating to
40"C, so that an intramolecular electron transfer on the
time scale accessible in the experiment can be ruled out.
1
Scheme 2. NMR spectroscopically derived structures of 1, lZe, and lAe.
During the reduction of 1, the NMR signals of 1 and
1 2 Q are observed alongside each other without significant
line-broadening. This shows that no rapid intermolecular
electron transfer takes place and that the intermediate
disproportionates. The ion 1 Be, which
radical anion 1
apparently is present in only low concentration, cannot be
detected ESR spectroscopically. Its characterization can
only be achieved if it is generated from the dianion by
photooxidation. The ESR coupling constants a H(0.40 (6H,
COT-ring), 0.40 (2 H, CHJ, 0.88 mT (2 H, CH,)) show that
the unpaired electron is localized in one COT moiety.
Take-up of an electron by 1 forces, as also in COT 2, a
planarization of the eight-membered ring, which contains
the additional electron. Such a change of conformation
would have to occur alternately in the two eight-membered
rings if an intramolecular charge fluctuation between the
subunits were to take place in l o oor 1". As a result of
the associated increased reorganization
the excess charge of 1 O G and 120 therefore remains localized in
one subunit. The activation energy for the ring inversion of
Angew. Chem. Int. Ed. Engl. 26 (1987) No. I2
the uncharged ring of 1 ' O , which we determined as 12 kcal
mol-', should comply with the activation barrier of the
charge fluctuation. This is also consistent with the fact that
the spatial separation of COT subunits is not solely responsible for the charge localization, since rapid intramolecular electron transfer processes can take place in ion
pairs with separate rigid subunits.r131
Received: June 30, 1987;
revised: September 9, 1987 [ Z 2320 IE]
German version: Angew. Chem. 99 (1987) 1305
[I] J. R. Miller, L. T. Calcaterra, G. L. Closs, J. Am. Chem. Sac. 106 (1984)
3047.
[Z] S. Mazur, V. M. Dixit, F. Gerson, 1. A m . Chem. Sac. 102 (1980) 5343.
[3] W. Huber, H. Unterberg, K. Mullen, Angew. Chem. 95 (1983) 239; Angew. Chem. b t . Ed. Engl. 22 (1983) 242.
141 W. Huber, K. Miillen, Ace. Chem. Res. 19 (1986) 300.
[5] J. Fiedler, W. Huber, K. Miillen, Angew. Chem. 98 (1986) 444; Angew.
Chem. Inr. Ed. EngL 25 (1986) 443.
[6] W. Irmen, W. Huber, J. Lex, K. Miillen, Angew. Chem. 96 (1984) 800;
Angew. Chem. lni. Ed. Engl. 23 (1984) 818.
171 L. Echegoyen, R. Maldonado, J. Nieves, A. Alegria, J . A m . Chem. Sac.
106 (1984) 7692.
[8] S. W. Staley, C. K. Dustman, K. L. Facchine, G. E. Linkowsky, J. Am.
Chem. Sac. 107 (1985) 4003.
191 B. Eliasson, U. Edlund, S. W. Staley, EUCHEM Conf: Electron Transfer
Reoct. Urg. Chem., Visby (Sweden), June 1987.
[lo] L. A. Paquette, S. V. Ley, R. H. Meisinger, R. K. Russell, M. Oku, J. A m .
Chem. SOC.96 (1974) 5806.
[ l l ] K. Miillen, Angew. Chem. 99 (1987) 192; Angew. Chem. Int. Ed. Engl. 26
(1987) 204.
[I21 The yield of 1 of only 6% referred to 2 is explained by the formation of
5 also occurring under these reaction conditions and by the large losses
in the HPLC separation of 1 and 5.
[I31 F. Gerson, W. Huber, W. B. Martin, Jr., P. Caluwe, T. Pepper, M.
Szwarc, Helm Chim. Acto 67 (1984) 416.
DibenzoIfg,mmnloctalene and
CyclooctaIdefphenanthrene. New Models for the
Conformational Analysis of Biphenyl Systems**
By Willi Heinz, Peter Langensee, and Klaus Miillen*
Dedicated to Professor Klaus Hafner on the occasion of
his 60th birthday
An important step in the conformational analysis of biphenyl systems is the bridging of the ortho
The compounds 1, 2, and 3r3,41
are particularly attractive
[*] Prof. Dr. K. Miillen, DipLChem. W. Heinz, Dr. P. Langensee
Institut fur Organische Chemie der Universitat
J.-J.-Becher-Weg 18-20, D-6500 Mainz 1 (FRG)
[**I This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
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1291
because rotation about the biphenyl single bond occurs simultaneously with the inversion of the octalene and/or cyclooctatetraene moieties. Compounds 1-3 are of addi4
1
2
31,
5b. R=COOEt
R=R;H
3b, R = H .R’=CHMe,
6
8
9
3c. R =CH,. R’=CHHe,
tional importance in view of the recently described finding
that the energy profiles of conformational conversions can
be influenced by electron transfer proce~ses.~’-~~
Herein we
describe the synthesis, structure, and redox chemistry of
the new compounds dibenzolfg,mn]octalene 1 and cycloocta[deflphenanthrene 2 and the saturated analogues
5a, 6 and 8, and 10-12, respectively, derived therefrom.
In the case of the dianion of 1 it was possible to demonstrate a symmetry deformation by charge localization.
The key step of the synthesis of 1 is the reaction of
2,2’,6,6’-tetra(bromomethyl)biphenyl 4 with the dipotassium salt of ethyl ethanetetracarboxylate to give the octaester 5b, in which two condensed eight-membered rings
are formed in one step (Scheme 1). For transformation into
1 the diene 6 obtainable from 5b by hydrolysis/decarboxylation and subsequent oxidative decarboxylati~n[~l
was
converted by bromine addition into a tetrabromide, dehydrobromination of which however, for conformational reasons, did not furnish l but only 7. Therefore 6 was first
subjected to a base-induced isomerization. The resulting
7 :3 mixture of 8 (syn/unri) and 9 after bromination with
N-bromosuccinimide (NBS) and dehydrobromination affords compound 1 [m.p. 188°C (hexane), colorless needles]. The cyclooctaIdeflphenanthrene 2 is synthesized
analogously from 4,5-di(brornomethyl)phenanthrene via
10 (Scheme 1). The partially hydrogenated analogues 5a
as well as 11 and 12 are formed upon reduction of the
precursors 6 and 10, respectively, with H2. Characteristic
data of the new compounds are listed in Tables 1 and 2.
Table 1. Melting points (apart for 15) and ‘H-NMR spectroscopic data of
the compounds 5a, 6, 10-13, and 15.
5a, m.p. 123°C; ‘H-NMR (C2D2Cl4, 300 MHz, 110°C): 6=7.31 (t. 2 H ; p-
H,,,,),
7.15 (d, 4 H ; m-Haro,), 2.69 (m. 4H), 2.15-2.05 (m, 8H), 1.56 (m,
4 H)
6 , m.p. 204-205°C; ’H-NMR (CDCI,, 400 MHz): 6=7.29 (t, 2 H ; ,D-H~,~,),
7.05 (d, 4 H ; m-Haro,), 5.81 (m, 4 H ; Hole(),3.09, 2.90(AB system, 8 H )
10, m.p. 86.5”C; ‘H-NMR (CD2C12,300 MHz, 2OOC): 6(H,,,,)=7.68
(d,
2H), 7.55 (t, 2H), 7.51 (s, 2H), 7.38 (d, 2H), 6=6.32 (t, 2 H ; Hole,), 3.22 (d,
4 H)
11, m.p. 88.5”C; ‘H-NMR (CD2C12,300 MHz, -30°C): 6(H,,,,)=7.66
(d,
2H), 7.52(s,2H), 7.56-7.47(m,4H),6(H,,,,,)=2.91 (m, 2H),2.33 (m, 2H),
2.21 (m,2H). 1.99 (m,2 H )
12, m.p. 87°C; ‘H-NMR (CDCI,, 300 MHz, 20°C): 6=7.30-7.16 (m.6 H :
H,,,,), 2.89-2.66 (m, 6H), 2.23-2.15 (m.4H), 1.80-1.73 (m. 2 H )
13, m.p. 149-150°C; ‘H-NMR (C2D2C14,300 MHz, 12OOC): 6=7.39-7.26 (m,
SH;H,,,,),2.74(m,2H),2.25-2.lO(m,4H),
1.60(m,2H)
15, ‘H-NMR (CDCI,, 200 MHz, 20°C): 6=7.27-6.90 (m,6 H ; H,,,,),
6.73,
6.03 (AA‘BB’ system, 4 H ; “butadiene” H), 5.84 (m,2 H ; H,,,,), 3.57 (m,2 H ;
2CH-CH3),0.47(d,6H: 2CH3)
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Scheme 1. a) Dimethoxyethane/toluene (ill), l l 0 ” C ; 25%. b) KOH, ethylene glycol, 200°C; 84%. c) Pb(OAc),, pyridine, 65°C; 23%. d) Br,, CCI,,
toluene, 110°C; 27% referred to 6 .
0°C. e) 1,5-diazabicyclo[4.3.0]non-5-ene,
f) {BuOK, THF, 65°C. g) NBS, CC14, 80°C. h) rBuOK, THF, 20°C: 40% referred to 6. i) H2 (2 equiv.), Pd/C (sO/O), ethyl acetate, 25OC; 81%. j) BrZr
CCL/hexane, - 80°C; 90%. k) 1,8-Diazabicyclo[5.4.O]undec-7-ene,
benzene,
80°C; 43%. I) Analogous to (i) (I equiv. H2); 80%. m) Analogous to (I);
91%.
The twisting with respect to the CS-CS’ bond brought
about by the tub conformation of the unsaturated eightmembered rings of 1 and 2 as well as the bond alternation
are confirmed by the small value for the vicinal coupling
constant 3J(H8,H8’) (see Table 2). According to the X-ray
structure analysis[s1the eight-membered ring subunit of 2
is more flattened than that of 3a[91(twist angles of the biphenyl moiety: 33.0 and 68.5”;of the butadiene moiety:
51.2 and 58.O0).
If one takes the position of the conjugation band of the
respective biphenyl unit‘’]in the UV spectrum as a measure
of the twist [A [nm] ( E ) : 1, 217 (32000); 3a, 230 (24000);
5a, 220 (13000); 12,260 (12300); 13,235 (11 SOO)], the interplanar angle of the biphenyl system should, firstly, be
greater in 1 than in 3a, secondly, remain unaltered in the
transition from 1 and 3a to 5a and 13, respectively, and,
thirdly, be smallest in the dihydrophenanthrene system
12.
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Angew. Chem. h i . Ed. Engl. 26 (1987) No. I2
Table 2. 'H[cS,,]- and "C[G,]-NMR chemical shifts as well as the magnitudes of the vicinal couplings ' J [Hz] of 1, 2, 3a and K 2 - l , Liz-2, K2-3a [a].
H/C
I
2
-
-
140.9
111.3
139.7
144.3
'2'2,
-
6, ( 2 )
6c ( 2 )
6,(2'O)
& (3a'O)
(3a2')
-
-
6H
SM
(1
)
sdl;O
&(I-)
&i
137.9
109.5
-
108.1
3
4
6.96
7.25
5.03
6.36
127.2
126.1
100.0
115.3
7.72
7.57
6.34
6.43
126.8-128.2
106.2
111.1
5.93
6.37
104.9
113.2
131.OIbI
139.5
8.02
134.9
5
6
6.96
7.66
127.2
133.5
7.25
7.58
-
129.4IbI
7.78
135.9
139.7
114.8
-
134.2 [b]
118.0
-
115.3
7
8
6.65
6.04
133.8
90.2
6.25
5.40
133.1
88.4 [b]
6.12
91.1
6.00
5.90
130.7
96.2
6.47
6.19
131.8
88.7 [bl
6.43
95.3
9
6.65
5.60
133.8
135.2
7.53
7.14
Icl
129.9 [b]
-
10
'J(H7,HS)
'J(H8,HS')
6.00
6.17
130.7
130.4
11.6
10.8
2.5
12.9
-
10.9
9.6
3.3
10.1
10.2
10.6
-
[a] Measurement conditions: 1: (Ds]THF, 200 MHz ('H), 50 MHz (I3C), 25°C; 128: [D81THF, 200 MHz, -80°C ('H), SO MHz, 50°C ("C); 2: CD2C12;300 MHz
('H), 75 MHz ("C), 25°C; 2": [Ds]THF, 300 MHz, -60°C ('H),75 MHz, -20°C ( " C ) ; 3 2 e : [Ds]THF, 200 MHz, -80°C ('H), 50 MHz, -40°C ("C). [b]
Assignment not confirmed experimentally. [c] One of the signals between S= 126.8 and 128.2.
The synthesis of the salts M2-1 and M2-2 was achieved
by treatment of 1 and 2, respectively, with alkali metal
(M = Li, K) in [D,]THF. The NMR spectroscopic characterization of the ions (see Table 2) revealed the relationCharacteristic of both species
ship of 2" and 3a2Q.I10,111
are the distribution of the charge over the whole n-electron
system (as derived from the chemical shifts), the diatropism of the ions, and the formation of p h a r i z e d eightmembered rings with n-bond delocalization [see the adjustment of the vicinal H,H couplings 3J(H7,H8) and
3J(HS,HS')].
Whereas the number of the NMR signals is consistent
with a D2 symmetry for the neutral compound 1, a lowering of the symmetry is observed in l Z Q
The
. number and
position of the signals of l Z ecan only be interpreted in
terms of the excess charge of the dianion remaining localized in a dibenzocyclooctene moiety (see lazQ).Whereas
the charged substructure becomes more planar, the uncharged butadiene bridge remains bent. The strain associated with a flattening of the whole molecule is apparently so great that it does not permit a symmetric structure
with electrostatically preferred charge delocalization. Even
at room temperature there is no fluctuation of charge between charged and uncharged subunits in lZQ.
The charge localization in 1 2 Q has characteristic chemical consequences. The kinetically controlled attack of electrophiles on dianion- intermediate^"^' preferentially takes
place at the site of highest charge density; in the case of a
charge delocalization in 1 2 Q (DZh),this would, according
to a simple MO consideration, be at C1 and Cl'. These
bridgehead centers are the centers of highest charge density in 142Q,as has been shown by preparatively useful reductive transformations via Li2-14.f'41
That the charge dis-
15
tribution in l Z Q
corresponds to that in 3a2' but not to that
in 14", follows from the reaction of K2-1 with dimethyl
sulfate: exclusively the dimethyl adduct 15 is formed.
Received: June 30, 1987;
revised version: September 9, 1987 [Z 2321 IE]
German version: Angew. Chem. 99 (1987) 1306
CAS Registry numbers:
1, 111409-90-6; K2-1, 111410-04-9; 2, 111409-91-7: Liz-& 111410-08-3; K23 a , 111410-06-1; 4, 257-55-6; 5 a , 111409-92-8; 5 b , 111410-02-7; 6, 11140993-9: 7, 111409-94-0; 8, 111409-95-1; 9 , 111409-96-2: 10, 111409-97-3; 11,
111409-98-4; 12, 111409-99-5; 13, 1082-12-8; 15, 111410-01-6.
K. Mislow, M. A. W. Glass, H. B. Hopps, E. Simon, G. H. Wahl, Jr., J.
Am. Chem. Soc. 86 (1964) 1710.
lazo
14
The conformationally determined charge localization in
lZQ
invites comparison with 3b, 3c, and 14:
-
-
ion formation in 3b effects a flattening or drastically
reduces the inversion barrier of the eight-membered
ring;'6.71only strong steric interactions as in 3c lead to
non-planar dianions;171
the dianion of octalene 14 has D2,, symmetry even at
- 145"C; i.e. should structures with charge localization
( 14aZ0)occur, then they rapidly interconvert.["]
Angew. Chem. Inr. Ed. Engl. 26 (1987) No. I 2
P. Rashidi-Ranjbar, J. Sandstrom, Tetrahedron Lett. 28 (1987) 1537.
E. Vogel, W. Frass, J. Wolpers, Angew. Chem. 75 (1963) 979; Angew.
Chem. Int. Ed. Engl. 2 (1963) 625.
F. Sondheimer, H. N. C. Wong, J. Org. Chem. 45 (1980) 2438.
R. H. Baughman, 1. L. Bredas, R. R. Chance, R. L. Elsenbaumer, L. W.
Shacklette, Chem. Reu. 82 (1982) 209.
W. Huber, K. Miillen, Acc. Chem. Res. 19 (1986) 300.
W. Heinz, P. Langensee, K. Miillen, J . Chem. SOC.Chem. Commun.
1986, 947.
W. Heinz, P. Langensee, J. Lex, K. Miillen, unpublished.
N. Z. Huang, T. C. W. Mak, J . Mol. Struct. 101 (1983) 135.
K. Miillen, Helu. Chim. Acta 61 (1978) 1296.
H. Giinther, A. Shyouk, D. Crerner, K.-H. Frisch, Justus Liebigs Ann.
Chem. 1978, 165.
K. Miillen, J. F. M. Oth, H.-W. Engels, E. Vogel, Angew. Chem. 91
(1979) 251; Angew. Chem. Int. Ed. Engl. 18 (1979) 229.
K. Miillen, Angew. Chem. 99 (1987) 192; Angew. Chem. I n t . Ed. Engl. 26
(1987) 204.
E. Vogel, H.-W. Engels, W. Huber, J. Lex, K. Miillen, J . Am. Chem. SOC.
104 (1982) 3729.
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