Laticyclic conjugated double bonds within the framework of oligocondensed bicyclo[2.2.2]octenes

Article abstract of DOI:10.1039/a803481h

The all-syn oligocondensed bicyclo[2.2.2]octenes 3, 5, 20 and 29 with two to five etheno bridges show interaction of their π-orbitals by σ-overlap. This laticyclic conjugation reveals itself in the PE and UV spectra of the series as well as in the site se

Full text of DOI:10.1039/a803481h

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Laticyclic conjugated double bonds within the framework of
oligocondensed bicyclo[2.2.2]octenes
Wolfram Grimme,*,a Jens Wortmann,a Dirk Frowein,a Johann Lex,a
Grace Chenb and Rolf Gleiter*,b
a Universität zu Köln, Institut für Organische Chemie, Greinstraße 4, D-50939 Köln, Germany
b Organisch-Chemisches Institut der Universität Heidelberg, Im Neuenheimer Feld 270,
D-69120 Heidelberg, Germany
The all-syn oligocondensed bicyclo[2.2.2]octenes 3, 5, 20 and 29 with two to five etheno bridges show
interaction of their ð-orbitals by ó-overlap. This laticyclic conjugation reveals itself in the PE and UV
spectra of the series as well as in the site selectivity of the Diels–Alder reaction with inverse electron
demand found for the dehydro derivatives 11 and 26. As shown in the crystal structures of 3, 5 and 20,
the etheno bridges are positioned face to face at a distance which is smaller than the sum of their
van der Waals radii.
Cl4
Introduction
The various ways to achieve cyclic delocalization by joining
chains of conjugated π-systems were studied in 1971 by Hoff-
mann and Goldstein.1 One way they suggested is to arrange the
chains face to face at so close a distance that σ-interaction
between their termini occurs. This so-called laticyclic con-
jugation of unsaturated chains can result in an electronic
stabilization, but it does not if all the chains are of the same
mode. Accordingly, the laticyclic conjugation of ethene units
leads to a set of molecular orbitals, bonding and antibonding
through space, that are all filled and do not provide a net stabil-
isation. However, due to their filled ‘antibonding’ orbitals these
systems should show interesting spectroscopic and chemical
properties.
1
Cl4
Cl4
Rigid molecules with two double bonds facing each other
in close proximity represent the simplest laticyclic conjugated
systems. Many of them are known and in, for example,
isodrine,2 seco-pagodadiene,3 hypostrophene,4 tricyclo-
[6.2.2.22,5]dodeca-1,5-diene5 and pentacyclo[8.2.1.12,5.14,7.18,11]-
hexadeca-1,7-diene6 the through space interaction has been
studied. We have developed a general method for the synthesis
of oligocondensed bicyclo[2.2.2]octenes with all-syn con-
figuration and here describe a series of them with up to five
laticyclic conjugated etheno bridges.
4
2
11
13
9
16
5
5
15
9
10
6
4
12
10
8
4
7
8
6
18
17
20
12
11
14
7
1
1
3
3
2
14
19
13
2
3
5
Scheme 1
or diethylene glycol monoethyl ether to 3 and 5 without the
reduction of double bonds. This result differs from that
obtained when π-conjugated polyenes bearing chloro sub-
stituents are submitted to the same conditions. The triene 1 for
example is dechlorinated with loss of a conjugated double bond
by sodium in ethanol. The empty antibonding MOs of the
π-conjugated diene are responsible for this overreduction.
This route to syn-oligocondensed bicyclo[2.2.2]octenes with
laticyclic conjugated etheno bridges was pursued further by
using dienophiles with an extended bicyclo[2.2.2]octadiene
unit. For the preparation of the next higher homologue with
four etheno bridges syn-dehydrosesquibicyclo[2.2.2]octene 11
was needed as a dienophile. It was synthesized from the
cycloadduct 69 of p-benzoquinone to cyclohexadiene in which
the carbonyl flanked double bond was saturated with zinc in
acetic acid (Scheme 2). The resulting diketone 7 was trans-
formed into tricyclo[6.2.2.02,7]dodeca-3,6,9-triene 9 via the
Shapiro reaction10 of its bis(tosylhydrazone) 8. Cycloaddition
of the acetylene synthon (E)-1,2-ditosylethene11,12 to 9 occurs
to the convex side to give 10 which was detosylated with sodium
amalgam to the triene 11.
Results and discussion
The common starting compound for the synthesis of all-syn
condensed bicyclo[2.2.2]octenes is endo-tetrachlorotricyclo-
[6.2.2.02,7]dodecatriene 1, the product of the Diels–Alder
reaction of tetrachlorothiophene dioxide (TCTD)7 with di-
hydrobarrelene followed by SO2 extrusion.† The diene unit of 1
is activated for the cycloaddition with inverse electron demand8
by the chloro substituents and it reacts with unsaturated hydro-
carbons if their double bond is easily accessible. This is not the
case for the etheno bridge in 1 and therefore it does not add to
itself. However, ethene and dihydrobarrelene undergo cyclo-
addition with 1 below 100 ЊC under a pressure of 7 kbar (Scheme
1). The resulting condensed bicyclo[2.2.2]octenes 2 and 4 with
all-syn configuration are dechlorinated with sodium in ethanol
† The term syn indicates that the functional groups, here double bonds,
are orientated towards each other. Our linear oligocondensed bicyclo-
[2.2.2]octenes are all-syn; in their angular isomers the double bonds
facing each other are marked by numbers, e.g. tetraene 17 is 15,16;
19,20;21,22-syn. The term endo refers to the configuration of Diels–
Alder products with the ‘maximum accumulation of unsaturation’.
J. Chem. Soc., Perkin Trans. 2, 1998
1893

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26
25
R
O
13
18
15
16
14
17
H
11
20
12
7
H
R4
R
2
O
6
1
19
22
24
23
6
7 R = O
9
60%
10
8
9
8 R = N-NHTos
5
3
21
4
17 R = Cl , 18 R = H
R
Me
Cl4
Tos
O
O
+
Me
R
1
10 R = Tos
11 R-R = π-bond
Tos
12
2R0 4
15
16
7
22
8
10
14 19 12 21
13 11
6
26
25
24
9
20%
Me
17
5
1
3
23
2
4
18
O
RO
RO
19 R = Cl , 20 R = H
Me
11
O
13
14 R = H
15 R = Mes
16
Cl4
Scheme 2
59%
Cl4
+
21
+
SO2
TCTD
To synthesize the four-fold syn-condensed bicyclo[2.2.2]-
octene we planned to add two molecules of the diene 1 to
barrelene 1613as the central unit. On our route to barrelene14 we
added in the first step (E)-1,2-ditosylethene to dimethyldioxa-
bicyclo[4.3.0]nonadiene15 to give 12. After forming the second
double bond in the bicyclo[2.2.2]octadiene unit by detosylation
with sodium amalgam, the acetonide 13 was hydrolyzed and the
resulting diol 14 mesylated. Demesylation16 of 15 with sodium
anthracenide17 afforded barrelene 16 in a reasonable overall
yield.
11
12
16
6
5
15
10
8
Cl4
18
17
7
9
4
1
13
27%
3
14
2
22
Scheme 3
The cycloaddition of diene 1 to syn-dehydrosesquibicyclo-
[2.2.2]octene 11 cannot be as straightforward as in the case of
dihydrobarrelene since the two accessible double bonds in 11
have different surroundings. The reaction under high pressure
yielded a mixture of two isomers 17 and 19 (Scheme 3) with the
angular adduct prevailing in a ratio of 3:1. This result can be
rationalized by the laticyclic conjugation in 11 that enriches
one of the double bonds of the bicyclo[2.2.2]octadiene subunit
with electrons and favors its addition to the electron poor diene
1. Both cycloadditions occur exclusively to the convex side
of 1 with endo stereochemistry. After separation by liquid
chromatography, both cycloadducts were dechlorinated with
sodium in diethylene glycol monoethyl ether to the tetraenes
18 and 20, respectively.
H
H
H
H
18
23
+
24
25
The electron poor diene TCTD also discriminates between
the two accessible double bonds of 11, forming at room
temperature two isomeric cycloadducts. The main product is
the tetrachlorobenzo-condensed tetracyclic diene 21 (59%), that
results from cycloaddition to the laticyclic conjugated double
bond of 11 followed by extrusion of SO2 and a dyotropic
hydrogen shift.18 The minor product 22 (27%) is a homologue
of the tetrachlorodiene 1. It adds dihydrobarrelene under high
pressure to give the laticyclic conjugated tetraene 19 in good
yield. This alternative route to 19 offers no advantage as it again
includes the addition of an electron poor diene to the wrong
double bond of 11.
In contrast to the all-syn-condensed bicyclo[2.2.2]octenes 3,
5 and 20 that are thermally stable up to 280 ЊC the angular
tetraene 18 decomposes at 214 ЊC to bicyclo[2.2.2]octene 24,
naphthalene, benzene and ethene (Scheme 4). Monitoring the
reaction by sealed-tube NMR showed that the products are
formed simultaneously in equal amounts. A proposed mechan-
ism for this fragmentation starts with an intramolecular
hydrogen transfer19 in 18 converting it into its dyotropomer 23.
A rapid cascade of three (4 ϩ 2)-cycloreversions then splits 23
+
+
Scheme 4
into the observed products with benzodehydrosesquibicyclo-
[2.2.2]octene 25 and dihydrobarrelene as intermediates.
The two-fold cycloaddition of 1 to barrelene at 110 ЊC and
8.1 kbar over 120 h led to the angular and the linear tetra-
condensed bicyclo[2.2.2]octenes 27 and 28 in a ratio of 1:3.5
(Scheme 5). The monoadduct 26 formed in the first step is a
higher homologue of 11 and again provides a laticyclic con-
jugated and a terminal double bond for the second addition of
the electron poor diene 1. In this case, however, the terminal
double bond is preferred since the four chloro substituents
withdraw electrons from the laticyclic system. Dechlorination
of the linear tetracondensed bicyclo[2.2.2]octene 28 to 29 was
achieved with sodium in diethylene glycol monoethyl ether.
1894
J. Chem. Soc., Perkin Trans. 2, 1998

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Table 1 Vertical ionization energies Ei,v,j of oligocondensed bicyclo-
[2.2.2]octenes and calculated orbital energies, Ϫεj, using the AM1 and
RHF(6-31G*) basis. All values in eV.
Cl4
H
Compound Band Ei,v,j
Assignment Ϫεj (AM1) Ϫεj (RHF)
H
Cl4
Cl4
+
20%
1
2
3
1
2
3
1
2
3
8.1
9.4
9.7
7.5
8.6
9.2
7.4
8.3
9.2
b1(π)
a1(π)
a2(σ)
b1(π)
a1(π)
b1(π)
b1(π)
a1(π)
b1(π)
9.1
10.04
8.34
9.84
10.76
7.85
9.16
10.04
7.58
8.64
9.56
3
5
1
16
27
8.78
9.57
Cl4
8.62
9.24
Cl4
20
+
26
1
double bonds shows little variation. As the four localised
π-orbitals are filled and the same is true for the four laticyclic
orbitals resulting from their linear combination, the bond order
between the etheno bridges is zero. The laticyclic system
thus would drift apart were it not kept together by the rigid
σ-framework.
In order to assign the ionization potentials of the laticyclic
conjugated polyenes we carried out ab initio20 studies on the
compounds 3, 5 and 20. Calculations were performed with the
program GAUSSIAN9421 on IBM RISC-6000 Model 580.
Molecules 3, 5 and 20 were fully optimized within C2v symmetry
constraint using restricted Hartree–Fock theory (RHF) and
density functional theory (DFT)22 applying the hybrid method
Becke3LYP23 together with the 6-31G* basis set. All structures
were confirmed to be minima by analytical vibrational
frequency calculations.
R4
R4
26
17
19
24
7
28
27
15
21
14
12
25
8
10
6
16
18
23
13
32
30
9
11
70%
5
3
1
29
4
31
20
2
22
28 R = Cl, 29 R = H
Scheme 5
The optimized structures of 3, 5 and 20, together with
important structural parameters, are shown in Fig. 1. In
general, they agree very well with the corresponding X-ray
structures. At the RHF/6-31G* level, all ethene- and σ-bond
lengths differ from the corresponding data in the X-ray struc-
tures by less than 0.15 Å. All structures show that the σ-
framework forms an arc and, furthermore, the degree of
bending grows with the number of condensed bicyclo[2.2.2]-
octene units. The distances between the etheno bridges decrease
with the chain getting longer. The calculated contact between
the etheno bridges is 3.14 Å in 3, 3.12 Å in 5 and 3.10 and 3.12
Å in 20. As found in the X-ray structure, for compound 20
the contact of the inner pair is predicted to be closer than that
of the terminal bridges.
The presence of laticyclic conjugation in the all-syn-
condensed bicyclo[2.2.2]octenes is demonstrated by their
PE spectra. In Table 1 the ionization energies of 3, 5 and 20
are listed together with the assignment of the individual
bands. The latter is based on the results of semi-empirical
(AM1)24 and ab initio (RHF/6-31G*) calculations on the
ground state assuming the validity of Koopmans’ theorem.25
The first ionization energies decrease from 9.05 eV in the parent
bicyclo[2.2.2]octene 2426 to 7.4 eV in its three-fold condensed
homologue 20. The second ionization energies also decrease
from 9.4 eV in 3 to 8.3 eV in 20 as does the splitting between the
two upmost laticyclic MOs. Semi-empirical (AM1) and ab initio
(RHF/6-31G*) calculations indicate that all the π-MOs of the
all-syn oligocondensed bicyclo[2.2.2]octenes result from lati-
cyclic conjugation. A detailed analysis by means of the Wein-
hold natural bond orbital localization procedure27 applying the
method of Imamura and Ohsaku28 shows large through space
interactions and very little through bond contributions. The
symmetry of the laticyclic HOMOs and HOMOs-1 in 3, 5 and
20 is the same as that familiar from the two upmost π-MOs
in ethene, the allylic triad and butadiene (Fig. 2).
Fig. 1 Computer generated crystal structure (hydrogen atoms omit-
ted) of all-syn-condensed bicyclo[2.2.2]octenes 3, 5 and 20. Parameters
given are from X-ray structural analysis (in bold type) and from
calculations at the B3LYP/6-31G* (in normal type) and RHF 6-31G*
(in italics) level.
X-Ray structure analyses were performed for the polyenes 3,
5 and 20 with two to four etheno bridges. They show that their
σ-framework is not linear but forms an arc. The etheno bridges
face each other more closely than is expected from the sum
of their van der Waals radii. The contact between the inner
pair of 20 is a little closer (3.04 Å) than that to the terminal
bridges (3.08 Å), but compared to the bond alternation in
π-conjugated chains the distance between the σ-conjugated
The UV spectra of the series of all-syn oligocondensed
bicyclo[2.2.2]octenes show a continuous bathochromic shift
of their long wavelength absorption from λmax = 220 nm for 3
to λmax = 250 nm for 29 with a broad end absorption (Fig. 3).
J. Chem. Soc., Perkin Trans. 2, 1998
1895

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spectra on a Finnigan MAT INCOS 50 spectrometer. For
preparative GC a Varian Aerograph 90 P was used. Reactions
under high pressure were performed in a 10 ml steel autoclave
(Nova Swiss, Neu-Isenburg) shielded by a heavy plastic case
and heated with an electrical coil. The two stage pressure
generator is a product of B. Dieckers, Krefeld. The reaction
mixture was sealed into a polytetrafluoroethene (PTFE)
cramping tube (10 cm, 0.6 cm diameter). Melting points were
determined in open capillaries with a Tottoli apparatus (Büchi,
Flawil). For flash chromatography Silitech 32-64 60A (ICN,
Eschwege) was used in a column (50 × 3 cm) filled to a third
of its height.
HOMO
HOMO-1
endo-3,4,5,6-Tetrachlorobicyclo[6.2.2.02,7]dodeca-3,4,9-triene 1
Dihydrobarrelene (354 mg, 3.34 mmol) in benzene (2 ml) was
added at room temperature to freshly sublimed tetrachloro-
thiophene dioxide (TCTD, 848 mg, 3.34 mmol). The exo-
thermic reaction that evolves SO2 was finished by stirring for
1 h. The mixture was evaporated and the residue in hexane
was filtered through silica gel (1 cm). Concentration in a rotary
evaporator yielded 1 (982 mg, 99%), mp 96–97 ЊC; δH 1.31 (2 H,
BBЈ, 11-Hn, 12-Hn), 1.33 (2 H, AAЈ, 11-Hn, 12-Hn), 3.13 (2 H,
s, 2-H, 7-H), 3.21 (2 H, t, 1-H, 8-H), 6.32 (2 H, q, 9-H, 10-H);
δC 24.08, 33.68, 48.39, 123.03, 132.60, 133.94; λmax(hexane)/nm
280 (ε/dm3 molϪ1 cmϪ1 2500), 292 (5300), 304 (6300), 318
(4400).
Fig. 2 Orbital symmetry of laticyclic conjugated oligocondensed
bicyclo[2.2.2]octenes and of π-conjugated open chains. The HOMO
and HOMO-1 of 3, 5 and 20 are compared with the two upmost π-MOs
of ethene, the allylic triad and butadiene.
syn-3,4,5,6-Tetrachlorotetracyclo[6.2.2.2.3,602,7]tetradeca-4,9-
diene 2
1 (296 mg, 1 mmol) in diethyl ether (25 ml) was filled into the
glass liner of an autoclave (50 ml). After fitting the vessel with a
stopper with a gas inlet and a gas outlet tube it was cooled to
Ϫ100 ЊC and ethene (800 ml) was condensed into the solution.
The glass liner was placed into the cooled (dry ice) steel
autoclave which was closed and heated to 130 ЊC for 90 h.
After cooling to room temperature excess ethene was released
and the reaction mixture was concentrated and recrystallized
Fig. 3 UV absorption spectra of all-syn oligocondensed bicyclo-
[2.2.2]octenes in n-hexane
o
from hexane to afford 2 (310 mg, 95%), mp 84 C; (Found C,
51.89; H, 4.67. Calc. for C14H14Cl4: C, 51.89; H, 4.35); λmax
-
(hexane)/nm 222sh (ε/dm3 molϪ1 cmϪ1 2200); νmax/cmϪ1 3052,
2950, 2918, 2902, 2870, 2860, 1595; δH 1.19–1.24 (2 H, m,
11-Hn, 12-Hn), 1.44–1.51 (2 H, m, 11-Hx, 12-Hx), 1.90–1.96
(2 H, m, 13-Hn, 14-Hn), 2.10–2.16 (2 H, m, 13-Hx, 14-Hx),
2.36 (2 H, s, 2-H, 7-H), 2.90 (2 H, m, 1-H, 8-H), 6.01–
6.03 (2 H, m, 9-H, 10-H); δC 25.39 (C-11, 12), 31.65 (C-1, 8),
38.87 (C-13, 14), 52.81 (C-2, 7), 70.74 (C-3, 6), 127.35 (C-4,
5), 129.60 (C-9, 10); m/z 287 (100%, M Ϫ Cl), 251 (82, M Ϫ
Cl Ϫ HCl).
Additionally, the higher homologues exhibit a second band at
shorter wavelengths. In comparison with π-conjugated open
chain polyenes29 the laticyclic systems absorb at lower wave-
lengths and with extinction coefficients that are smaller by two
orders of magnitude. The complete occupation of all laticyclic
orbitals resulting from the interaction of the bonding ethene
MOs accounts for this effect.
In conclusion, the structural, spectroscopic and chemical
properties of the all-syn oligocondensed bicyclo[2.2.2]octenes
with two to five etheno bridges indicate the presence of lati-
cyclic conjugation. The π-electron configuration of these
systems results from perturbation theory in the same way as
it does for chains of π-conjugated p-atomic orbitals (AOs).
However, in the latter the interaction of singly occupied AOs
affords resonance stabilisation whereas the laticyclic interaction
of filled π-MOs destabilizes the system.
syn-Tetracyclo[6.2.2.23,6.02,7]tetradeca-4,9-diene 3
A solution of 2 (130 mg, 0.4 mmol) in anhydrous ethanol (8 ml)
was heated to reflux under an argon atmosphere. Sodium
(460 mg, 20 mmol) in small pieces was added over 2.5 h to
the stirred solution and heating was continued for a further
30 min. After cooling to room temperature the reaction slurry
was poured on a mixture of ice and water (20 g) and extracted
with hexane (3 × 30 ml). The combined organic layers were
washed with water (2 × 30 ml) and brine (1 × 30 ml) and dried
over MgSO4. The crude product was purified by flash chroma-
tography on silica gel (hexane) and recrystallized from hexane
to yield 3 (52.1 mg, 70%), mp 56 ЊC; λmax(hexane)/nm 220
(ε/dm3 molϪ1 cmϪ1 1150); νmax/cmϪ1 3042, 3034, 2973, 2933,
2899, 2875, 2860, 1648, 688; δH 1.05–1.09 (4 H, m, 11-Hn,
12-Hn, 13-Hn, 14-Hn), 1.43-1.51 (4 H, m, 11-Hx, 12-Hx, 13-Hx,
14-Hx), 1.93 (2 H, s, 2-H, 7-H), 2.28 (4 H, m, 1-H, 3-H, 6-H,
8-H), 5.74–5.77 (4 H, m, 4-H, 5-H, 9-H, 10-H); δC 27.12 (C-11,
12, 13, 14), 35.15 (C-1, 3, 6, 8), 43.69 (C-2, 7), 131.96 (C-4,
5, 9, 10); m/z 186 (Mϩ, 44%), 106 (18, M Ϫ C6H8), 80 (100,
C6H8ϩ), 78 (24, C6H6ϩ); Calc. for C14H18: 186.141, Found
186.140 (MS).
Experimental
NMR spectra were recorded on a Bruker AM 300 spec-
trometer at 300 MHz (1H) and 75.5 MHz (13C) in CDCl3.
Chemical shifts are in ppm relative to internal TMS. Signals
were assigned by C᎐H COSY and NOE methods. Multiplicity
and position of protons are abbreviated as follows: AAЈ, BBЈ
(part of AAЈBBЈ system at low, high field); AB (AB system
centered at the position given); ∆ν (shift difference of the
nuclei of the AB system in Hz); J (coupling constant between
the nuclei of the AB system in Hz); Hn, Hx (hydrogen atoms
in the endo- or exo-position). UV spectra were obtained using
a Perkin-Elmer Lambda 7 spectrometer, IR spectra were
recorded on a Perkin-Elmer 1600 FTIR spectrometer, mass
1896
J. Chem. Soc., Perkin Trans. 2, 1998

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all-syn-1,8,15,16-Tetrachlorohexacyclo[6.6.2.23,6.210,13.02,7.09,14]-
icosa-4,11,15-triene 4
endo-Tricyclo[6.2.2.02,7]dodec-9-ene-3,6-dione
bis(tosylhydrazone) 8
A solution of 1 (424 mg, 1.43 mmol) and bicyclo[2.2.2]octa-
2,5-diene (152 mg, 1.43 mmol) in anhydrous tetrahydrofuran
(THF, 1.5 ml) together with a crystal of 4-tert-butylcatechol
was heated for 96 h to 80 ЊC under a pressure of 7.8 kbar. After
cooling to room temperature the solvent was removed under
vacuum and the product purified by flash chromatography on
silica gel (hexane) and recrystallized from hexane. 4 (486 mg,
85%), mp 198 ЊC (dec.) (Found: C, 59.86; H, 5.03. Calc. for
C20H20Cl4: C, 59.73; H, 5.01%); λmax(hexane)/nm 242sh (ε/dm3
molϪ1 cmϪ1 620); νmax/cmϪ1 3042, 2953, 2906, 2868, 1654, 1601;
δH 1.15–1.19 (4 H, m, 17-Hn, 18-Hn, 19-Hn, 20-Hn), 1.41–1.48
(4 H, m, 17-Hx, 18-Hx, 19-Hx, 20-Hx), 2.30 (4 H, s, 2-H, 7-H,
9-H, 14-H), 2.91–2.92 (4 H, m, 3-H, 6-H, 10-H, 13-H), 5.94–
6.00 (4 H, m, 4-H, 5-H, 11-H, 12-H); δC 25.54 (C-17, 18, 19, 20),
31.48 (C-3, 6, 10, 13), 54.10 (C-2, 7, 9, 14), 74.89 (C-1, 8), 124.59
(C-15, 16), 130.35 (C-4, 5, 11, 12); m/z 402 (Mϩ, 20%), 365
(80, Mϩ Ϫ Cl), 329 (60, M Ϫ Cl Ϫ HCl), 293 (32, M Ϫ Cl Ϫ
2HCl), 80 (100, C6H8ϩ).
The solution of dione 7 (8.6 g, 50 mmol) and tosyl hydrazide
(20.7 g, 0.11 mol) in dry methanol (375 ml) was acidified
with toluene-p-sulfonic acid (0.1 g) and stirred for 2 h at
room temperature. The voluminous precipitate was collected
on a Büchner funnel, washed with methanol and dried in a
desiccator over P4O10. 8: (25.2 g, 96%), mp 140 ЊC (dec.).
endo-Tricyclo[6.2.2.02,7]dodeca-3,5,9-triene 9
The solution of 8 (18.9 g, 36 mmol) in dry THF (550 ml) was
stirred under argon and cooled in an ice bath. n-Butyllithium in
n-hexane (1.6 , 100 ml, 0.16 mol) was added from a dropping
funnel slowly to keep the temperature of the reaction mixture
below 5 ЊC. After stirring at room temperature overnight the
mixture was carefully hydrolyzed with conc. NH4Cl (50 ml),
diluted with water (500 ml) and extracted with pentane (5 × 200
ml). The combined extracts were washed with water (6 × 250
ml) and with brine (250 ml) and dried over MgSO4. After
concentration in a rotary evaporator at 0 ЊC and 25 Torr the
product was flash chromatographed with pentane and recrystal-
lized from n-hexane. 9: (3.56 g, 63%), mp 57 ЊC; δH 1.24 (2 H,
BBЈ), 1.64 (2 H, AAЈ), 2.4 (2 H, d), 2.87 (2 H, s), 5.29 (2 H,
BBЈ), 5.42 (2 H, AAЈ), 6.25 (2 H, q); δC 25.95, 35.88, 40.60,
120.55, 129.87, 134.66.
all-syn-Hexacyclo[6.6.2.23,6.210,13.02,7.09,14]icosa-4,11,15-triene 5
A solution of 3 (486 mg, 1.21 mmol) in diethylene glycol
monoethyl ether (35 ml) was heated to 100 ЊC under an argon
atmosphere. Sodium (1.4 g, 60.5 mmol) was added in small
pieces over 3 h to the stirred solution and heating was con-
tinued for a further 30 min. After cooling to room temperature
the slurry was poured on a mixture of ice and water (50 ml)
and was extracted with hexane (5 × 50 ml). The combined
organic layers were washed with water (5 × 50 ml) and brine
(1 × 50 ml) and dried over MgSO4. After filtration the
solvent was removed under vacuum and the residue purified by
flash chromatography with hexane. 5 (185.3 mg, 58%), mp
197 ЊC; λmax(hexane)/nm 218 (ε/dm3 molϪ1 cmϪ1 1400), 231
(1200); νmax/cmϪ1 3050, 2932, 2902, 2881, 2867, 1654, 1618, 686;
δH 0.99–1.05 (4 H, m, 17-Hn, 18-Hn, 19-Hn, 20-Hn), 1.39–1.49
(4 H, m, 17-Hx, 18-Hx, 19-Hx, 20-Hx), 1.94 (4 H, s, 2-H, 7-H,
9-H, 14-H), 2.23 (6 H, m, 1-H, 3-H, 6-H, 8-H, 10-H, 13-H),
5.21–5.27 ( 2 H, m, 15-H, 16-H), 5.64–5.69 (4 H, m, 4-H, 5-H,
11-H, 12-H); δC 27.29 (C-17, 18, 19, 20), 34.77 (C-3, 6, 10, 13),
41.28 (C-1, 8), 45.59 (C-2, 7, 9, 14), 130.31 (C-15, 16), 132.28
(C-4, 5, 11, 12); m/z 264 (Mϩ, 100%), 236 (16, M Ϫ C2H4), 184
(16, M Ϫ C6H8), 80 (70, C6H8); Calc. for C20H24: 264.188,
Found 264.188 (MS).
syn-11-exo,12-endo-ditosyltetracyclo[6.2.2.23,6.02,7]tetradeca-
4,9-diene 10
A
solution of endo-tricyclo[6.2.2.02,7]dodeca-3,5,9-triene
9
(2.77 g, 17.5 mmol) and (E)-1,2-bis(toluene-p-sulfonyl)ethene
(5.89 g, 17.5 mmol) in 50 ml toluene was heated to reflux
under argon for 24 h. After cooling to room temperature the
solvent was removed under vacuum and the residue purified
by flash chromatography with hexane–ethyl acetate 3:1. 10:
(8.23 g, 95%), mp 178–180 ЊC (dec.); δH 0.99–1.57 (4 H, m,
13-H, 14-H), 2.43 (6 H, br s, 2 CH3), 1.82–3.21 (6 H, 2 m, 1-H,
3-H, 6-H, 8-H, 2-H, 7-H), 3.44–3.99 (2 H, 2 m, 11-H, 12-H),
5.60–5.94 (4 H, m, 4-H, 5-H, 9-H, 10-H), 7.23–7.39 (4 H, m,
2Ј-H, 3Ј-H, 2Љ-H, 3Љ-H), 7.55–7.90 (4 H, m, 1Ј-H, 4Ј-H, 1Љ-H,
4Љ-H).
syn-Tetracyclo[6.2.2.23,6.02,7]tetradeca-4,9,11-triene 11
The ditosylethene adduct 9 (7.42 g, 15 mmol) and sodium
dihydrogenphosphate monohydrate (36 g) were suspended
under an argon atmosphere in anhydrous methanol (300 ml).
The mixture was stirred vigorously for 0.5 h while 2% sodium
amalgam (138 g, 0.12 mol Na) was added in small portions and
the stirring was continued at room temperature overnight.
Mercury and remaining buffer were removed by filtration and
the filter cake was washed thoroughly with hexane. To the
combined organic filtrates water (300 ml) was added and the
aqueous phase was extracted with hexane (3 × 200 ml). The
extracts were washed consecutively with water (2 × 200 ml) and
brine (1 × 200 ml) and dried over MgSO4. After filtration the
solvent was removed under vacuum and the product was puri-
fied by flash chromatography with hexane. 11: (2.07 g, 75%), mp
57 ЊC (Found C, 91.12; H, 8.74. Calc. for C14H16: C, 91.23; H,
8.75%); νmax/cmϪ1 3048, 2948, 2934, 2893, 2860, 1654, 1618; δH
1.11 (2 H, BBЈ, 13-Hn, 14-Hn), 1.42 (2 H, AAЈ, 13-Hx, 14-Hx),
1.89 (2 H, s, 2-H, 7-H), 2.31 (2 H, m, 3-H, 6-H), 3.32 (2 H, m, 1-
H, 8-H), 5.71 (2 H, m, 4-H, 5-H), 5.86 (2 H, m, 9-H, 10-H), 6.38
(2 H, m, 11-H, 12-H); δC 27.15 (C-13, 14), 34.92 (C-3, 6), 42.40
(C-1, 8), 43.02 (C-2, 7), 131.45 (C-4, 5), 132.61 (C-9, 10), 136.80
(C-11, 12); m/z 184 ( Mϩ, 0.5%), 57 (100, C4H9ϩ); Calc. for
C14H16: 184.125, Found 184.125 (MS).
endo-Tricyclo[6.2.2.02,7]dodeca-4,9-diene-3,6-dione 6
Cyclohexa-1,3-diene (8.0 g, 0.10 mol) and freshly steam
distilled p-benzoquinone (11.0 g, 0.10 mol) were boiled in
benzene (90 ml) under reflux for 4 h. After concentration in
a rotary evaporator the product was recrystallized from
ethanol. 6: (16.2 g, 85%), mp 98 ЊC; δH 1.48 (4 H, AAЈBBЈ,
2 CH2), 2.92 (s, 2 H), 3.20 (2 H, AAЈ), 6.15 (2 H, XXЈ), 6.57
(2 H, s).
endo-Tricyclo[6.2.2.02,7]dodec-9-ene-3,6-dione 7
Zinc powder (26.1 g, 0.40 mol, <200 mesh) was stirred in 4 
HCl (50 ml) for 2 min, collected on a Büchner funnel and
washed with acetic acid. The activated metal was suspended in
95% aqueous acetic acid (250 ml), 6 (12.35 g, 65 mmol) was
added and the mixture was stirred vigorously at 70 ЊC for 3 h.
After filtration and washing the filter cake with methylene
chloride (3 × 50 ml), the combined filtrates were brought to
dryness under vacuum. The residue was taken up in methylene
chloride (100 ml), washed consecutively with 2  HCl (3 × 25
ml), conc. NaHCO3 and brine and dried over MgSO4. After
concentration the product was recrystallized from methanol.
7: (9.7 g, 78%), mp 58 ЊC; δH 1.45 (4 H, AAЈBBЈ, 2 CH2), 2.48
(4 H, AAЈBBЈ, 2 CH2), 2.89 (2 H, s), 3.18 (2 H, AAЈ), 6.20 (2 H,
XXЈ).
4,4-Dimethyl-10,11-ditosyl-3,5-dioxatricyclo[5.2.2.02,6]undec-
8-ene 1214
3,3-Dimethyl-2,4-dioxabicyclo[4.2.0]nona-6,8-diene (4.65 g, 30
mmol) and (E)-ditosylethene (10.08 g, 30 mmol) in ethyl acetate
J. Chem. Soc., Perkin Trans. 2, 1998
1897

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(250 ml) were heated to reflux under an argon atmosphere
for 48 h. The scarcely soluble dienophile had reacted almost
completely after this period. The reaction mixture was filtered
and brought to dryness after addition of silica gel (20 g). Flash
chromatography of the residue with hexane–ethyl acetate 3:1
provided the product 12. (11.7 g, 80%), mp 166 ЊC; δH 1.21 (3 H,
s, CH3), 1.24 (3 H, s, CH3), 2.42 (3 H, s, CH3), 2.43 (3H, s, CH3),
3.23 (1 H, m), 3.53 (1 H, m), 3.74 (2 H, s), 4.25 (1 H, m), 4.98
(1 H, m), 6.07 (2 H, AB, ∆ν 21, J 4.1), 7.51 (4 H, AAЈBBЈ), 7.60
(4 H, AAЈBBЈ).
anhydrous THF (2.5 ml) together with a crystal of 4-tert-butyl
catechol was heated to 80 ЊC under a pressure of 7.8 kbar for
96 h. The reaction mixture was concentrated under vacuum
and the products were separated by twice repeated flash
chromatography with hexane followed by fractional recrystal-
lization. 17 (288 mg, 60%), mp 260 ЊC (dec.); λmax(hexane)/nm
247 (ε/dm3 molϪ1 cmϪ1 2800); νmax/cmϪ1 3042, 2949, 2869, 1654,
1602; δH 1.16 (2 H, m, 25-Hn, 26-Hn), 1.21 (2 H, m, 23-Hn, 24-
Hn), 1.40–1.46 (4 H, 2 m, 23-Hx, 24-Hx, 25-Hx, 26-Hx), 1.53
(2 H, s, 4-H, 9-H), 2.15 (2 H, s, 13-H, 18-H), 2.17 (2 H, s, 2-H,
11-H), 2.41 (2 H, m, 5-H, 8-H), 2.77 (2 H, m, 3-H, 10-H), 2.88
(2 H, m, 14-H, 17-H), 5.95 (2 H, m, 15-H, 16-H), 5.99 (2 H, m,
21-H, 22-H), 6.23 (2 H, m, 6-H, 7-H); δC 25.53 (C-25, 26), 27.15
(C-23, 24), 31.52 (C-14, 17), 33.96 (C-5, 8), 36.13 (C-3, 10),
44.44 (C-4, 9), 50.84 (C-2, 11), 54.70 (C-13, 18), 75.09 (C-1, 12),
125.82 (C-19, 20), 130.31 (C-15, 16), 130.48 (C-6, 7), 132.07
(C-21, 22).
19 (96 mg, 20%), mp 252 ЊC (dec.); λmax(hexane)/nm 254
(ε/dm3 molϪ1 cmϪ1 600); νmax/cmϪ1 3056, 3040, 2952, 2942, 2930,
2913, 2880, 2863, 1634, 1602; δH 1.04 (2 H, m, 23-Hn, 24-Hn),
1.15 (2 H, m, 25-Hn, 26-Hn), 1.43 (4 H, 2 m, 23-Hx, 24-Hx,
25-Hx, 26-Hx), 1.90 (2 H, s, 4-H, 9-H), 2.27 (2 H, s, 13-H, 18-H),
2.32 (2 H, s, 2-H, 11-H), 2.30 (2 H, m, 5-H, 8-H), 2.86 (4 H, m,
3-H, 10-H, 14-H, 17-H), 5.51 (2 H, m, 21-H, 22-H), 5.67 (2 H,
m, 6-H, 7-H), 5.94 (2 H, m, 15-H, 16-H); δC 25.59 (C-25, 26),
27.05 (C-23, 24), 31.50 (C-14, 17), 34.44 (C-5, 8), 37.86 (C-3,
10), 43.99 (C-4, 9), 54.33, 56.09 (C-2, 11, 13, 18), 74.64 (C-1,
12), 124.68 (C-19, 20), 128.62 (C-21, 22), 130.32 (C-15, 16),
132.29 (C-6, 7).
4,4-Dimethyl-3,5-dioxatricyclo[5.2.2.02,6]undeca-8,10-diene 1314
The suspension of 12 (11.7 g, 24 mmol) and sodium dihydrogen-
phosphate (57.6 g) in dry methanol (480 ml) was vigorously
stirred under an argon atmosphere while 2% sodium amalgam
(221 g, 0.192 mol Na) was added over 1 h. After stirring
overnight mercury and inorganic salts were filtered off and
washed with methylene chloride. The methanol filtrate was
diluted with water (300 ml) and extracted with methylene
chloride (3 × 300 ml). The combined methylene chloride phases
were dried over MgSO4 and concentrated, leaving a colourless
oil that crystallized in the refrigerator. 13 (4.06 g, 95%), mp
55 ЊC; δH 1.21 (3 H, s, CH3), 1.28 (3 H, s, CH3), 3.79 (2 H, m),
4.18 (2 H, m), 6.25 (2 H, m), 6.32 (2 H, m).
cis-2,3-Dihydroxybicyclo[2.2.2]octa-5,7-diene 1414
The ketal 13 (4.06 g, 23 mmol) was dissolved in acetic acid
(140 ml) and water was added to the solution until it became
turbid. The mixture was heated to 100 ЊC for 2 h whereafter
all volatile components were evaporated at 40 ЊC and 10 Torr.
The residue was flash chromatographed with methylene
chloride–acetonitrile 3:1 yielding 14 (2.54 g, 80%), mp 60–
62 ЊC; δH 2.69 (2 H, br s, OH), 3.77 (4 H, m), 6.20 (2 H, m), 6.41
(2 H, m).
15,16;19,20;21,22-syn-Octacyclo[10.6.2.23,10.25,8.214,17.02,11.04,9.
0
13,18]hexacosa-6,15,19,21-tetraene 18
Tetrachlorotetraene 17 (200 mg, 0.42 mmol) was dissolved in
diethylene glycol monoethyl ether (35 ml) at 100 ЊC and the
stirred solution was kept under argon and treated with finely
cut sodium (283 mg, 12 mmol) over the course of 3 h. After
another 15 min the mixture was cooled to room temperature
and diluted with water (20 ml). The precipitate was collected on
silica gel (50 mg) by filtration and washed with water followed
by methanol. The coated silica gel was dried under vacuum and
subjected to a flash chromatography with hexane. 18 (44.5 mg,
31%), mp 270 ЊC (dec.); λmax(hexane)/nm 232 (ε/dm3 molϪ1 cmϪ1
1100); δH 1.00 (2 H, BBЈ, CH2), 1.20 (2 H, BBЈ, CH2), 1.35 (2 H,
s), 1.42 (4 H, 2 AAЈ, CH2), 1.74 (2 H, s), 1.78 (2 H, s), 2.12 (4 H,
s), 2.20 (2 H, m), 2.32 (2 H, m), 5.24 (2 H, m), 5.65 (4 H, m), 6.21
(2 H, m); δC 27.26, 27.43, 34.23, 34.82, 39.67, 41.49 (double
cis-2,3-Bis(methanesulfonyloxy)bicyclo[2.2.2]octa-5,7-diene 1514
The solution of diol 14 (2.50 g, 18 mmol) in methylene chloride
(100 ml) was treated with triethylamine (6.15 g, 60.9 mmol)
and cooled in an ice bath. Freshly distilled methanesulfonyl
chloride (4.8 g, 41.9 mmol) was dropped into the solution and
stirring was continued for 2 h at 0 ЊC. The mixture was poured
onto ice and water (200 ml) and the organic phase was washed
with 2  HCl, then with 1  sodium hydrogencarbonate
and dried over MgSO4. Concentration in a rotary evaporator
left colourless crystals of 15 (4.07 g, 77%), mp 132 ЊC; δH 3.04
(6 H, s, 2 CH3), 4.12 (2 H, m), 4.68 (2 H, m), 6.35 ( 2 H, m), 6.48
(2 H, m).
intensity), 46.08, 46.25, 129.51, 131.51, 132.27, 134.40; m/z 342
ؒ
(Mϩ, 23%), 262 (50 M Ϫ C6H8 ), 234 (97, C18H18 ϩ), 128 (90,
Bicyclo[2.2.2]octa-2,5,7-triene 1614
᝽
C10H8 ϩ), 80 (100, C6H8).
A solution of sodium anthracenide was prepared by stirring
anthracene (5.34 g, 30 mmol) in dry THF (100 ml) in an argon
atmosphere with finely cut sodium (0.67 g, 30 mmol) for 2 h.
The resulting deep blue solution was added dropwise with
a syringe to the crystals of dimesylate 15 (2.76 g, 9.4 mmol)
that were kept in a two necked flask equipped with a diaphragm
and a balloon filled with argon. After addition of 70 ml of the
blue anthracenide solution its colour persisted in the reaction
flask. The mixture was quenched with a few drops of methanol
and the volatile components were condensed at 40 ЊC and 10
Torr into a trap cooled with liquid nitrogen. The contents of
the trap were reduced to 3 ml by fractional distillation over
a Vigreux column (30 cm) at 760 Torr. The final separation
by preparative GC over 20% reoplex on kieselguhr (1 m,
0.25Љ, 78 ЊC, injector and detector 110 ЊC) yielded barrelene 16
(200 mg, 20.5%).
᝽
Thermolysis of 15,16;19,20;21,21-syn-Octacyclo[10.6.2.23,10
25,8.214,17.02,11.04,9.013,18]hexacosa-6,15,19,21- tetraene 18
.
An NMR probe of 18 in [2H10]xylene was deaerated by two
freeze–thaw cycles and sealed. The tube was heated in the steam
of refluxing n-dodecane (bp 214 ЊC) and the NMR spectrum
was taken at intervals of 24 h. After 4 d the NMR analysis
indicated that 18 had completely decomposed to equal amounts
of bicyclo[2.2.2]octene 24, naphthalene, benzene and ethene.
all-syn-Octacyclo[10.6.2.23,10.25,8.214,17.02,11.04,9.013,18]hexacosa-
6,15,19,21-tetraene 20
A solution of 19 (105 mg, 0.22 mmol) in diethylene glycol
monoethyl ether (20 ml) was heated to 100 ЊC under an argon
atmosphere. Sodium (253 mg, 11 mmol) was added in small
15,16;19,20;21,22-syn-1,12,19,20-Tetrachlorooctacyclo-
[10.6.2.23,10.25,8.214,17.02,11.04,9.013,18]hexacosa-6,15,19,21-tetraene
17 and all-syn-1,12,19,20-tetrachlorooctacyclo[10.6.2.23,10.25,8.
214,17.02,11.04,9.013,18]hexacosa-6,15,19,21-tetraene 19‡
‡ IUPAC names for compounds 17–20, 27–29 (excluding stereo-
chemistry) are: 17–20, 1,12,19,20-tetrachlorooctacyclo[10.6.2.23,10.-
25,8.214,17,02,11.04,9.013.18]hexacosa-6,15,19,23-tetraene;
27–29,
3,10,
14,21,25,26,29,30-octachlorodecacyclo[10.10.2.23,10.25,8.214,21.216,19.02,11
04,9.013,22.015,20]dotriaconta-6,17,23,25,29-pentaene.
.
The solution of 1 (296 mg, 1 mmol) and 11 (184 mg, 1 mmol) in
1898
J. Chem. Soc., Perkin Trans. 2, 1998

View Article Online
pieces over 3 h to the stirred solution and the heating was con-
tinued for a further 15 min. The cooled reaction mixture was
poured into water (20 ml) and the precipitate was collected on
silica gel (50 mg) by filtration. After washing the silica gel with
water and a small amount of methanol it was extracted by flash
chromatography with hexane. The product fraction was con-
centrated and recrystallized from CHCl3. 20 (26 mg, 35%), mp
252 ЊC (dec.); λmax(hexane)/nm 245 (ε/dm3 molϪ1 cmϪ1 600);
νmax/cmϪ1 3042, 2936, 2921, 2905, 2881, 2865, 1619, 683; δH 1.01
(4 H, m, 23-Hn, 24-Hn, 25-Hn, 26-Hn), 1.42 (4 H, m, 23-Hx,
24-Hx, 25-Hx, 26-Hx), 1.91 (4 H, s, 4-H, 9-H, 13-H, 18-H), 1.95
(2 H, s, 2-H, 11-H), 2.15–2.21 (8 H, 2 m, 1-H, 3-H, 5-H, 8-H,
10-H, 12-H, 14-H, 17-H), 5.14 (4 H, m, 19-H, 20-H, 21-H,
22-H), 5.62 (4 H, m, 6-H, 7-H, 15-H, 16-H); δC 27.31 (C-23, 24,
25, 26), 34.74 (C-5, 8, 14, 17), 40.97 (C-1, 3, 10, 12), 45.77 (C-4,
9, 18, 19), 47.66 (C-2, 11), 130.67 (C-19, 20, 21, 22), 132.22
(C-6, 7, 15, 16); m/z 342 (Mϩ, 55%), 262 (100, M Ϫ C6H8), 80
(71, C6H8ϩ); Calc. for C26H30: 342.234, Found: 342.234 (MS).
CHCl3. 27 (69.9 mg, 20%), mp 285 ЊC (dec.); λmax/nm 236 (ε/dm3
molϪ1 cmϪ1 1450); νmax/cmϪ1 3047, 2952, 2937, 2908, 2865, 1654,
1600; δH 1.12–1.22 (4 H, m, Hn on CH2), 1.41–1.48 (4 H, m,
Hx on CH2), 1.99 (2 H, s, 13-H, 22-H), 2.17 (4 H, s, 2-H, 4-H,
9-H, 11-H), 2.25 (2 H, s, 15-H, 20-H), 2.88 (2 H, m, 5-H,
8-H), 2.96 (2 H, m, 16-H, 19-H), 3.38 (2 H, m, 1-H, 12-H), 5.93
(2 H, m, 6-H, 7-H), 6.03–6.07 (4 H, 2 m, 17-H, 18-H, 23-H,
24-H); δC 25.42, 25.54 (C-29, 30, 31, 32), 31.44 (C-5, 8, 16,
19), 33.52 (C-1, 12), 53.66 (C-13, 22), 49.14, 54.11 (C-2, 4,
9, 11), 54.91 (C-15, 20), 73.07, 74.11 (C-3, 10, 14, 21), 125.61,
126.97 (C-25, 26, 27, 28), 129.54 (C-17, 18), 130.28 (C-6, 7),
131.75 (C-23, 24).
28 (240.8 mg, 70%), mp 295 ЊC (dec.) (Found: C, 55.29;
H, 4.09. Calc. for: C32H28Cl8: C, 55.21; H, 4.05%); λmax/nm
256 (ε/dm3 molϪ1 cmϪ1 1030); νmax/cmϪ1 3056, 2978, 2949,
2934, 2923, 2864, 1654, 1604; δH 1.14–1.18 (4 H, BBЈ, Hn on
CH2), 1.40–1.46 (4 H, AAЈ, Hx on CH2), 2.26 (4 H, s, 4-H,
9-H, 15-H, 20-H), 2.28 (4 H, s, 2-H, 11-H, 13-H, 22-H), 2.90
(m, 4 H, 5-H, 8-H, 16-H, 19-H), 3.48 (2 H, m, 1-H, 12-H), 5.78
(2 H, m, 23-H, 24-H), 5.94 (4 H, m, 6-H, 7-H, 17-H, 18-H);
δC 25.53 (C-29, 30, 31, 32), 31.42 (C-5, 8, 16, 19), 35.01 (C-1,
12), 54.17 (C-4, 9, 15, 20), 54.51 (C-2, 11, 13, 22), 73.97 (C-3,
10, 14, 21), 124.87 (C-25, 26, 27, 28), 127.05 (C-23, 24), 130.30
(C-6, 7, 17, 18).
syn-3,4,5,6-Tetrachloropentacyclo[6.6.2.210,13.02,7.09,14]octadeca-
2,4,6,15-tetraene 21 and syn-endo-3,4,5,6-tetrachloropenta-
cyclo[6.6.2.210,13.02,7.09,14]octadeca-3,5,11,15-tetraene 22
The solution of triene 11 (184 mg, 1 mmol) and tetrachloro-
thiophene dioxide (253.8 mg, 1 mmol) in benzene (5 ml) was
stirred at room temperature for 48 h. After evaporation of
solvent the two isomeric cycloadducts were separated by flash
chromatography with hexane followed by crystallization from
the same solvent. 21 (258 mg, 59%), mp 164 ЊC; λmax/nm 245sh
(ε/dm3 molϪ1 cmϪ1 6300); δH 0.43 (2 H, BBЈ, 11-Hin, 12-Hin),
0.93 (2 H, AAЈ, 11-Hout, 12-Hout), 1.45 (4 H, m, CH2), 1.63 (2 H,
s, 10-H, 13-H), 1.91 (2 H, s, 9-H, 14-H), 4.37 (2 H, m, 1-H, 8-H),
6.56 (2 H, m, 15-H, 16-H); δC 21.17 (C-11, 12), 29.00 (C-17, 18),
29.18 (C-10, 13), 40.85 (C-9, 14), 43.07 (C-1, 8), 128.30 (C-3, 6),
128.68 (C-4, 5), 136.48 (C-15, 16), 142.78 (C-2, 7); m/z 374
(Mϩ, 45%), 266 (100, M Ϫ C8H12), 80 (43, C6H8ϩ).
all-syn-Decacyclo[10.10.2.23,10.25,8.214,21.216,19.02,11.04,9.013,22.015,20
]
dotriaconta-6,17,23,25,27-pentaene 29
A solution of 28 (240 mg, 0.35 mmol) in diethylene glycol
monoethyl ether (150 ml) was prepared at 110 ЊC under an
argon atmosphere. To the stirred solution sodium (1.6 g, 70
mmol) was added in small pieces over 5 h. Heating was
continued for a further 15 min and the cooled reaction mixture
was poured on water (100 ml). The precipitate was collected
on silica gel (50 mg) by filtration. The silica gel was washed
thoroughly with water and a small amount of methanol and
continuously extracted with boiling hexane. After 4 d the
extract was concentrated and the residue recrystallized from
CHCl3. 29 (36.8 mg, 25%), mp 305 ЊC (dec.); λmax(n-hexane)/nm
214sh (ε/dm3 molϪ1 cmϪ1 3800), 250 (1020); νmax/cmϪ1(KBr)
3047, 2918, 2906, 2883, 2875, 684; δH(C6D6, 70 ЊC) 1.15 (4 H,
BBЈ, Hn on CH2), 1.48 (4 H, AAЈ, Hx on CH2), 1.89 (8 H, m,
2-H, 4-H, 9-H, 11-H, 13-H, 15-H, 20-H, 22-H), 2.16 (6 H, m,
1-H, 3-H, 10-H, 12-H, 14-H, 21-H), 2.21 (4 H, m, 5-H, 8-H,
16-H, 19-H), 5.19 (2 H, m, 23-H, 24-H), 5.23 (4 H, m, 25-H,
26-H, 27-H, 28-H), 5.72 (4 H, m, 6-H, 7-H, 17-H, 18-H);
m/z 420 (Mϩ, 5%), 91 (55, C7H7ϩ), 80 (85, C6H8ϩ), 79 (100,
C6H7ϩ), 78 (90, C6H6ϩ).
22 (118 mg, 27%), mp 131 ЊC; λmax/nm 269sh (ε/dm3 molϪ1
cmϪ1 2800), 281 (3100), 292 (4300), 305 (4600), 319 (2700); δH
1.11 (2 H, BBЈ, 17-Hn, 18-Hn), 1.48 (2 H, AAЈ, 17-Hx, 18-Hx),
2.02 (2 H, s, 9-H, 14-H), 2.36 (2 H, m, 10-H, 13-H), 3.05 (2 H,
m, 1-H, 8-H), 3.12 ( 2 H, s, 2-H, 7-H), 5.78 (2 H, m, 11-H,
12-H), 5.87 (2 H, m, 15-H, 16-H); δC 26.78 (C-17, 18), 34.45
(C-10, 13), 39.68 (C-1, 8), 42.04 (C-9, 14), 50.14 (C-2, 7), 123.21
(C-4, 5), 131.94 (C-15, 16), 132.13 (C-11, 12), 132.28 (C-3, 6).
Alternative route to all-syn-1,12,19,20-tetrachlorooctacyclo-
[10.6.2.23,10.25,8.214,17.02,11.04,9.013,18]hexacosa-6,15,19,21-tetraene
19
The solution of 22 (93.5 mg, 0.25 mmol) and bicyclo[2.2.2]-
octadiene (27 mg, 0.25 mmol) in THF (1.5 ml) together with a
crystal of 4-tert-butylcatechol was heated to 80 ЊC for 96 h
under a pressure of 7.8 kbar. After transferring the reaction
mixture with CHCl3 into a flask (10 ml) it was brought to dry-
ness and the product was purified by flash chromatography with
hexane. 19 (96.4 mg, 80%).
Crystal data
3: C14H18, M = 186.28. Triclinic, a = 6.268(1), b = 8.387(1),
c = 11.135(1) Å, α = 109.09(1), β = 90.24(1), γ = 111.68(1)Њ,
V = 518.91(11) Å3 (by least-squares refinement on diffracto-
meter angles for 25 automatically centered reflections, λ =
0.710 69 Å), space group P1, Z = 2, Dx = 1.192 g cmϪ3. Crystal
¯
dimensions: 0.25 × 0.25 × 0.03 mm, µ(Mo-Kα) = 0.96 cmϪ1
.
6,7;23,24;25,26-syn-17,18;27,28-syn-3,10,14,21,25,26,27,28-
5: C20H24, M = 264.39. Triclinic, a = 6.376(1), b = 10.376(1),
c = 11.232(1) Å, α = 97.99(2), β = 90.81(2), γ = 107.30(2)Њ, V =
701.01(14) Å3 (by least-squares refinement on diffractometer
angles for 25 automatically centered reflections, λ = 0.710 69 Å),
Octachlorodecacyclo[10.10.2.23,10.25,8.214,21.216,19.02,11.04,9.013,22
.
0
15,20]dotriaconta-6,17,23,25,27-pentaene 27 and all-syn-
3,10,14,21,25,26,27,28-octachlorodecacyclo[10.10.2.23,10.25,8.
214,21.216,19.02,11.04,9.013,22.015,20]dotriaconta-6,17,23,25,27-
pentaene 28
space group P1, Z = 2, Dx = 1.253 g cmϪ3. Crystal dimensions:
¯
0.30 × 0.30 × 0.20 mm.
A solution of bicyclo[2.2.2]octatriene 16 (52 mg, 0.5 mmol) and
1 (518 mg, 1.75 mmol) in anhydrous THF (2.5 ml), together
with a crystal of 4-tert-butylcatechol, was heated to 110 ЊC for
120 h under a pressure of 8.1 kbar. The reaction mixture was
transferred with CH2Cl2 into a flask (10 ml) and concentrated
under vacuum. The product isomers were separated by flash
chromatography on silica gel, first eluting the angular com-
pound 27 with n-hexane and then the all-syn-isomer 28 with
CHCl3. Both products were purified by recrystallization from
20: C26H30, M = 342.50. Triclinic, a = 6.385(2), b = 6.398(2),
c = 24.947(6) Å, α = 86.11(2), β = 86.76(2), γ = 60.27(2)Њ,
V = 882.7(4) Å3 (by least-squares refinement on diffractometer
angles for 25 automatically centered reflections, λ = 0.710 69 Å),
space group P1, Z = 2, Dx = 1.289 g cmϪ3. Crystal dimensions:
¯
0.15 × 0.20 × 0.22 mm.
Data collection
CAD4 diffractometer, ω/2δ mode with
ω scan width =
J. Chem. Soc., Perkin Trans. 2, 1998
1899

View Article Online
0.70 ϩ 0.35 tan θ, ω scan speed 2.2 deg minϪ1, graphite-mono-
chromated Mo-Kα radiation. 3: 2257 reflections measured
(2 < θ < 27Њ), giving 1579 with I > 2σ(I); 5: 4070 reflections
measured (2 < θ < 27Њ), giving 3365 with I > 2σ(I); 20: 4943
reflections measured (2 < θ < 28Њ), giving 2523 with I > 2σ(I).
Linear and approx. isotropic crystal decay, ca 1.6% corrected
during processing.
7 M. S. Raasch, J. Org. Chem., 1980, 45, 856.
8 J. Sauer and H. Wiest, Angew. Chem., Int. Ed. Engl., 1962, 1, 269.
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62, 4162.
Structure analysis and refinement
After data reduction, the structure was solved by direct
methods using the MolEN program package and refined
2
against F0 for all unique reflections using SHELXL-9330
14 This synthesis of barrelene was developed by Andreas Kirst,
Dissertation, University of Cologne, 1995.
(C atoms with anisotropic temperature factors and H atoms
with isotropic ones). Final R1 and wR2 values for reflections
I > 2σ(I) are 3: R1 = 0.056 and wR2 = 0.123; 5: R1 = 0.045
and wR2 = 0.118; 20: R1 = 0.062 and wR2 = 0.159; R1 =
15 N. C. Yang, M.-J. Chen and P. Chen, J. Am. Chem. Soc., 1984, 106,
7310.
16 J. C. Carnahan and W. D. Closson, Tetrahedron Lett., 1972, 3447.
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18 (a) K. Mackenzie, J. Chem. Soc., 1965, 4646; (b) K. Mackenzie,
J. A. K. Howard, R. Siedlecka, K. B. Astin, E. C. Gravett,
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D. J. Woodnutt, Tetrahedron, 1987, 43, 5981.
2
2
2
2
2
¹
²
[Σ||Fo| Ϫ |Fc||/Σ|Fo|], wR2 = {[Σw(Fo Ϫ Fc ) /[Σw(Fo ) ]} ; weight-
2
ing scheme 3: w = 1/[σ2(Fo ) ϩ (0.053 P)2 ϩ 0.162 P]; 5: w = 1/
2
2
[σ2(Fo ) ϩ (0.069 P)2 ϩ 0.109 P]; 20: w = 1/[σ2(Fo ) ϩ (0.094
P)2 ϩ 0.737 P]; where P = (Fo2 ϩ 2Fc2)/3. The calculations were
performed at the Regional Computational Center at the
University of Cologne. Full crystallographic details, excluding
structure factor tables, have been deposited at the Cambridge
Crystallographic Data Center (CCDC). For details of the
deposition scheme, see ‘Instructions for Authors’, J. Chem.
Soc., Perkin Trans. 2, available via the RSC web page (http://
www.rsc.org/authors). Any request to the CCDC for this
material should quote the full literature citation and the
reference number 188/136.
19 W. Grimme, K. Pohl, J. Wortmann and D. Frowein, Liebigs Ann.,
1996, 1905.
20 W. J. Hehre, L. Radom, P. v. Schleyer and J. A. Pople, Ab Initio
Molecular Orbital Theory, Wiley, New York, USA, 1986.
21 GAUSSIAN94, Revision D.2: M. J. Frisch, G. W. Trucks,
H. B. Schlegel, P. M. W. Gill, B. G. Johnson, M. A. Robb,
J. R. Cheeseman, T. Keith, G. A. Peterson, J. A. Montgomery,
K. Raghavachari, M. A. Al-Laham, V. G. Zakryewski, J. V. Ortiz,
J. B. Foresman, J. Cioslowski, B. B. Stefanov, A. Nanayakkara,
M. Challacombe, C. Y. Peng, P. Y. Ayala, W. Chen, M. W. Wong,
J. L. Andres, E. S. Replogle, R. Gomperts, R. L. Martin, D. J. Fox,
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1995.
22 (a) N. H. March, Electron Density Theory of Atoms and Molecules,
Academic Press, San Diego, CA, 1992; (b) Density Functional
Methods in Chemistry, eds. J. K. Labanowski and J. W. Andzelm,
Springer-Verlag, New York, 1991; (c) R. G. Parr and W. Yang,
Functional Theory of Atoms and Molecules, Oxford University Press,
New York, USA, 1989.
23 (a) A. D. Becke, Phys. Rev. A, 1986, 33, 2786; (b) A. D. Becke,
J. Chem. Phys., 1988, 88, 2547; (c) C. Lee, W. Yang and R. G. Parr,
Phys. Rev. B, 1988, 37, 785.
24 J. J. P. Stewart, J. Comput.-Aided Mol. Des., 1990, 4, 1.
25 T. Koopmans, Physica, 1934, 1, 104.
26 P. Bischof, J. A. Hashmall, E. Heilbronner and V. Hornung, Helv.
Chim. Acta, 1969, 52, 1745.
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1985, 83, 735; (b) A. E. Reed and F. Weinhold, J. Chem. Phys., 1983,
78, 4066.
Photoelectron spectra
The He(I) photoelectron spectra of 3, 5 and 20 were recorded
on a Perkin-Elmer PS18 spectrometer. The recording tem-
peratures were as follows: 3: 40 ЊC, 5: 125 ЊC, 20: 160 ЊC. The
calibration was performed with Ar (15.76 and 15.94 eV) and
Xe (12.13 and 13.44 eV). A resolution of 20 meV on the
3P3/2 line was obtained.
Acknowledgements
Financial support by the Deutsche Forschungsgemeinschaft
is gratefully acknowledged. R. G. thanks the Fonds der
Chemischen Industrie for support, G. C. thanks the Alexander
von Humboldt Foundation for a stipend. We are grateful to
Alexander Flatow for recording the He(I) photoelectron
spectra.
References
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Paper 8/03481H
Received 8th May 1998
Accepted 17th June 1998
1900
J. Chem. Soc., Perkin Trans. 2, 1998