1,x-Elimination reactions: Extending the limits of a classical organic reaction

Article abstract of DOI:10.1002/chem.200700827

α,ω)-Dibromo derivatives in ich the two terminal carbon atom are separated by an unsaturated spacer unit (ππ spacer") undergo 1,x-elimination reactions (with x = 6, 8, 10, and 14), using Mori's reagent (nBu₃SnSiMe₃/CsF). The resulting cumulenic intermediates cyclodimerize in a subsequent step yielding novel macrocyclic acetylenic and bridged aromatic compounds (cyclophanes). Thus 1,6-eliminations were carried out with dibromide 17 to yield 1,3,7,9-cyclododecatetrayne (20) and with benzylbromide 24 to provide cyclophanes 26 and 27. By 1,8-eliminations the 16-membered macrocycle 33 could be prepared from enediyne 31, the benzannelated 1,5-cyclooctadiyne 41 from dibromide 38, and a mixture of cyclophanes 45 and 46 from the precursor 43. 1,10-Eliminations were carried out successfully with dibromides 47, 50, and 53 yielding the corresponding unsaturated cyclophanes ("cyclophynes") 49, 52, and 55. The influence of the solvent on the cyclodimerization 47→49 was investigated, with acetonitrile providing the highest yields. The heterophanes 59a and b were obtained by 1,10-elimination of the precursor dibromides 57 a and b, and in an elimination experiment involving a 1:1 mixture of the dibromides 50 and 57 b the "mixed dimer" 60 was isolated, besides the homodimers 52 and 59 b. The method reached its limits with the 1,14-elimination of 68, 70, and 74 providing the cyclophanes 69, 71, and 75 in varying amounts. Two final debrominations with 76 and 77, which in principle could undergo 1,16- and 1,20-eliminations reactions, respectively, failed. The structures of the new cyclophanes 49, 50, 59 a, and 59 b were established by X-ray structural analysis; all other structure assignments rest on the usual spectroscopic and analytical data.

Full text of DOI:10.1002/chem.200700827

DOI: 10.1002/chem.200700827
1,x-Elimination Reactions: Extending the Limits of a Classical Organic
Reaction
Christian Werner,[a] Henning Hopf,*[a] Ina Dix,[a] Peter Bubenitschek,[a] and
Peter G. Jones[b]
Dedicated to Professor Steen Steenken on the occasion of his 70th birthday
Abstract: a,w-Dibromo derivatives in
which the two terminal carbon atom
are separated by an unsaturated spacer
unit (“p spacer”)undergo 1, x-elimina-
tion reactions (with x = 6, 8, 10, and
1,5-cyclooctadiyne 41 from dibromide
38, and a mixture of cyclophanes 45
and 46 from the precursor 43. 1,10-
Eliminations were carried out success-
fully with dibromides 47, 50, and 53
yielding the corresponding unsaturated
cyclophanes (“cyclophynes”) 49, 52,
and 55. The influence of the solvent on
the cyclodimerization 47!49 was in-
vestigated, with acetonitrile providing
the highest yields. The heterophanes
59a and b were obtained by 1,10-elimi-
nation of the precursor dibromides 57a
and b, and in an elimination experi-
ment involving a 1:1 mixture of the di-
bromides 50 and 57b the “mixed
dimer” 60 was isolated, besides the ho-
modimers 52 and 59b. The method
reached its limits with the 1,14-elimina-
tion of 68, 70, and 74 providing the cy-
clophanes 69, 71, and 75 in varying
amounts. Two final debrominations
with 76 and 77, which in principle
could undergo 1,16- and 1,20-elimina-
tions reactions, respectively, failed. The
structures of the new cyclophanes 49,
50, 59a, and 59b were established by
X-ray structural analysis; all other
structure assignments rest on the usual
spectroscopic and analytical data.
14),
using
Moriꢀs
reagent
(nBu3SnSiMe3/CsF). The resulting cu-
mulenic intermediates cyclodimerize in
a subsequent step yielding novel mac-
rocyclic acetylenic and bridged aromat-
ic compounds (cyclophanes). Thus 1,6-
eliminations were carried out with di-
bromide 17 to yield 1,3,7,9-cyclodode-
catetrayne (20)and with benzylbro-
mide 24 to provide cyclophanes 26 and
27. By 1,8-eliminations the 16-mem-
bered macrocycle 33 could be prepared
from enediyne 31, the benzannelated
Keywords:
cycloaddition
cumulenes
cyclophanes
·
·
·
dimerization · elimination
Introduction
of substrate 1 into 2 (Scheme 1), in which two groups Y and
Z are removed from a “carrier” X. X can contain or consist
of carbon and/or hetero atoms, Y and Z may be simple
atoms (e.g. hydrogen)or complex functional groups. Numer-
ous mechanisms are possible for the transformation, and it
may be induced with very different reagents and under a
wide variety of conditions. Y and Z may be bonded to one
and the same atom or to different positions of the substrate.
If X is carbon, the 1!2 transformation translates into the
conversion of 3 into 4, in which “C” symbolizes a general or-
ganic fragment, which could be called a spacer, and can con-
sist of 1, 2 …, n carbon atoms (C1-, C2- …, Cn spacer).
Some general remarks on elimination reactions: Together
with pericyclic reactions, substitutions and redox reactions,
elimination reactions—and their converse: additions—
belong to the elementary processes of chemistry. In a more
general form they may be expressed by the transformation
[a] Dr. C. Werner, Prof. Dr. H. Hopf, Dr. I. Dix,
Dipl.-Chem. P. Bubenitschek
Institut für Organische Chemie
Technische Universität Braunschweig
Hagenring 30, 38106 Braunschweig (Germany)
Fax : (+49)531-391-5388
E-mail: H.Hopf@tu-bs.de
[b] Prof. Dr. P. G. Jones
Institut für Anorganische und Analytische Chemie
Technische Universität Braunschweig, Postfach 3329
38023 Braunschweig (Germany)
Scheme 1. An elimination reaction in general form.
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FULL PAPER
Scheme 2 shows these considerations in greater detail and
summarizes the typical text book elimination reactions
(without taking their different mechanisms into account),
that is, a-elimination to carbenes 5 (the bonds from C1 may
lead to the same atom as in the decomposition of azo com-
pounds), b elimination to olefins 6 and g elimination to cy-
clopropane and its derivatives 7.
Scheme 4. A selection of known 1,4-elimination reactions.
If a 1,2-disubstituted benzene ring is inserted between the
two leaving group carrying carbon atoms, as in the o-xylyl-
dihalide 12, the elimination leads to o-xylylenes (o-quinodi-
methanes), 13, long known as very useful diene components
for the construction of complex natural[3] and non-natural
carbon frameworks.[4]
Scheme 2. The classical textbook eliminations.
The unsaturated spacers in 8, 10, and 12 can easily be ex-
tended by combining them with unsaturated units of either
the same or of a different type, thus creating a diene, diyne,
enyne, etc. separating unit. Combination with aromatic units
could lead to diethynylbenzene or ethynylvinylbenzene
spacers, for example. If aromatic or heteroaromatic subunits
are employed, though, they must be connected in ortho-
(1,2-)or para- (1,4-)fashion. Any meta-substitution pattern
results in the formation of non-KekulØ structures[5] after
elimination.
The main purpose of the present paper consists in demon-
strating how the variation of the length and the electronic
nature of the spacer element “C” affects product formation.
Excluding hetero atoms the spacer unit can either contain
an odd or an even number of carbon atoms, and the spacer
can be saturated or unsaturated (Scheme 3), the most impor-
tant unsaturated “separating units” being the double and
the triple bond, and the benzene ring.
A selection of examples with odd unsaturated spacers is
finally listed in Scheme 5; substrates of this type are not dis-
cussed in the present publication, but certainly also deserve
more attention than they have hitherto attracted.
Scheme 3. A general Scheme for elimination reactions.
As a practical illustration the three well known examples
in Scheme 4 may be cited, with halide substituents as leaving
groups in all cases. Whereas reductive elimination of 1,4-
dihalo-2-butenes 8 furnishes 1,3-butadienes 9,[1] change of
the C2 spacer to an acetylene moiety (1,4-dihalo-2-butynes,
10)results in the formation of [3]cumulene 11.[2]
Scheme 5. Several elimination reactions involving odd spacers.
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9463

H. Hopf et al.
Results and Discussion
20 has been prepared previously by Sondheimer and co-
workers in the course of their studies on the preparation of
cyclic oligomers of 1,5-hexadiyne (19),[9,10] which, in turn,
served as precursors for their famous higher annulenes. Tet-
raacetylene 20 could be obtained in small amounts (ca.
10%)by Glaser coupling of 19, but apparently was never
isolated in pure form.
As far as the mechanism of formation of 20 is concerned,
the simplest route involves debromination of 17 to provide
1,2,3,4,5-pentahexaene (18), which subsequently dimerizes
to 20. There are no experimental hints for the formation of
the presumably very reactive (and unknown)[5] cumulene; its
tetramethyl derivative, though, has been described in the lit-
erature[11] and has been shown to undergo dimerization to
the octamethyl derivative of 20.[12,13] Alternatively, the cyclo-
dimerization of 17 could be initiated by a halogen–metal ex-
change with 15, forming an organocesium intermediate that
could then couple with a second molecule of 17. Repetition
of these steps on the resulting a,w-dibromide would ulti-
mately lead to 20. Whether these two pathways compete (or
occur simultaneously)can only be established by detailed
mechanistic experiments. Such intermediate bromides could
not be isolated in any of our experiments so far.
Before the first 1,x-elimination reactions were carried out,
we had to decide on both the leaving groups Y and Z to be
used, and on the elimination reagent and conditions. Be-
cause dibromides have often been employed in 1,4-elimina-
tions of the type presented in Scheme 4 (above), we also de-
cided to concentrate on substrates with Y=Z=Br. Usually
these are easy to prepare from their corresponding allylic,
propargylic or benzylic alcohols. As far as the actual elimi-
nation is concerned, the conditions were more restrictive.
Not only are all of the expected products (see below)highly
unsaturated, but the intermediates leading to them contain
an even higher number of p electrons, and are hence expect-
ed to be highly reactive; therefore, a method was needed in
which room temperature should not be significantly exceed-
ed. For example, the Hofmann elimination, which has been
used successfully in several vinylogous eliminations reac-
tions,[6] was disqualified from the very beginning because it
has to be carried out in refluxing toluene. A promising
method, however, is the elimination developed by Mori and
co-workers,[7] which employs the tributylstannyl anion (15),
generated in situ by cesium fluoride treatment of tributyl-
(trimethylsilyl)stannane (14, Scheme 6).
A 1,6-elimination involving an aromatic spacer element
was carried out with the dibromide 24, readily available by
Sonogashira coupling of 2-iodobenzylalcohol (22)with prop-
argyl alcohol (23), followed by bromination with phosphorus
tribromide (total yield 65%, Scheme 8).
Debromination with 14/CsF under the above conditions
furnished a complex product mixture, the components of
which could only be partially separated. In the end (after
several separation cycles by radial chromatography on silica
with petrol ether)only one of the hydrocarbon products
could be isolated in pure form in poor yield (2.2%): the
[2.6]orthocyclophane 26. Its structure assignment follows
from its spectroscopic and analytical data (see Experimental
Section), in particularly from the two singlets for methylene
protons at d=2.75 ppm (4H, propargylic hydrogen atoms)
and 3.07 (4H, benzylic hydrogen atoms), respectively. The
isomer of 26, the [4.4]orthocyclophane 27, could not be
freed from impurities; nevertheless, two triplets (J=7.1 Hz)
between d=2.5–3.5 ppm are indicative of an absence of a
plane of symmetry, and hence coupling between two methyl-
Scheme 6. Moriꢀs reagent.
The Japanese group has used this commercially available
reagent successfully for numerous 1,2- and 1,4-eliminations,
including the preparation of dehydrobenzene, o-xylylene
(13)and other highly unsaturated hydrocarbons and inter-
mediates.[8] In our hands this elimination reagent also turned
out to be the reagent of choice.
1,6-Eliminations: As a first example of a 1,x-elimination 1,6-
dibromo-2,4-hexadiyne (17), prepared from the correspond-
ing diol 16 by treatment with triphenylphosphine/bromine in
dichloromethane, was subjected to the above treatment with
Moriꢀs reagent in DMF at room temperature. We were
pleased to isolate
a
small
amount (10%)of 1,3,7,9-cyclo-
dodecatetrayne (20)from the
reaction mixture. Although this
hydrocarbon is unstable, it can
be purified by chromatography
on silica gel and obtained in
pure form as a colorless solid,
which quickly turns brown
(Scheme 7).
The tetrayne was character-
ized by its NMR spectra and its
complete hydrogenation to cy-
clododecane (21). Interestingly, Scheme 7. A 1,6-elimination leading to non-aromatic cyclic hydrocarbons.
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1,x-Elimination Reactions
FULL PAPER
(ꢀ258C). The structure assign-
ment of the hydrocarbon, for
which we propose the bis-cu-
mulene 32 as a precursor, rests
on its mass spectrum (m/z 204),
its 1H NMR spectrum (singlets
at d=5.95 and 2.58, respective-
ly), and its catalytic hydrogena-
tion to cyclohexadecane (36).
With its double enediyne struc-
ture, the hydrocarbon immedi-
Scheme 8. A 1,6-elimintion leading to aromatic cyclic hydrocarbons (cyclophanes).
ately suggests itself for a double
Bergman cyclization.[15] The ap-
propriate experiment (heating
ene groups. The two isomers, which can be regarded as the
head-to-head and the head-to-tail dimers of the cumulenic
intermediate 25, are produced in approximately equal
amounts (1H NMR analysis).
of 33 in benzene from 100 to 2008C in the presence of a
huge excess of 1,4-cyclohexadiene)proceeded inconclusive-
ly: because of partial peak overlap in the GC/MS spectrum
of the pyrolysate, the signals of the expected product 34
could not be assigned unambiguously. Furthermore, lack of
material precluded enrichment of the [2.2]orthocyclophane.
An aromatic version of the elimination of 31 was next
tried with 1,2-bis-(3-bromo-1-propynyl)benzene (38), pre-
pared by coupling o-dibromobenzene (37)with 23 followed
by bromination with phosphorus tribromide; the overall
yield of 28% is only mediocre in this case. On treatment of
38 with 14/CsF no dimer was isolated but instead the cy-
clized product 40, this time in excellent yield (62%). Evi-
dently intermediate 39—if formed at all—prefers ring clo-
sure to cycloisomer 41 over dimerization. Since ortho-xylyl-
enes have been used as dienes in countless cycloadditions[16]
we repeated the experiment in the presence of dimethyl
acetylene dicarboxylate (DMAD)as a trapping agent. The
expected product 40 or prod-
1,8-Eliminations: The first 1,8-elimination was carried out
with the acyclic precursor 31, obtained from (Z)-1,2-dichloro-
ethene (28)according to a procedure by Kçnig et al.
(Scheme 9).[14]
Thus 28 was coupled to the protected propargyl alcohol
29; the resulting bis-THP-ether 30 yielded the dibromide 31
directly on treatment with triphenylphosphine/bromine.
Mori debromination as described above provided a complex
and unstable product mixture from which we could isolate
cyclohexadeca-1,9-dien-3,7,11,15-tetrayne (33)in approxi-
mately 5% yield by silica gel chromatography. On removal
of residual solvent traces, 33 started to decompose; however,
the dimer is stable in dilute solution at low temperatures
ucts
derived
there
from
(dimers?)were, however, not
obtained (Scheme 10).
Although diyne 41 is stable
in ether or toluene solution, its
crystals, obtained by recrystalli-
zation from pentane, rapidly
change color from colorless to
brown, then black, upon stand-
ing, not only in air but also
under nitrogen or polyfluorinat-
ed silicon oil. If 41 is left stand-
ing in air for one week and the
resulting product mixture sub-
sequently admitted to the mass
spectrometer (temperature of
the inlet system up to 4008C), a
mass spectrum is registered
with peaks at m/z 720, 721, and
722 in a ratio of 1:0.67:0.21,
practically identical with the
signals of C60 in that spectral
region.[17]
Scheme 9. A 1,8-elimination leading to non-aromatic cyclic hydrocarbons.
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H. Hopf et al.
ics were included. The two types of eliminations/dimeriza-
tions will be discussed in turn.
The chain-extended dibromides 47, 50, and 53 were pre-
pared from the corresponding aromatic dihalides by the
methods discussed above; in all cases the overall yields for
the individual steps were between 80 and 95% (Scheme 12).
The Mori elimination took place as expected and the cy-
clophanes 49, 52, and 55 were obtained in variable yields.
The structures of these hydrocarbon were derived from
their spectroscopic and analytical data (see Experimental
Section); for 49 and 52, single crystals X-ray structural in-
vestigations could be performed (see below). Cyclophane 49
was used as a model system for optimisation, since it is the
most readily available macrocycle studied in this series; it is
also more stable than many of its analogues. In particular,
we varied the solvent used for the debromination step. For
the examples described in the literature DMF is usually em-
ployed.[7,8] As shown in Scheme 12, it was successful in our
example as well. In dichloromethane, no dimerization of 47
took place, and in THF only traces of the [6.6]paracy-
Scheme 10. A 1,8-elimination providing an ortho-cyclophane.
The isomer of 24, 1-bromomethyl-4-(3-bromo-1-propyn-
yl)-benzene (43), prepared from the benzyl alcohol 42 and
23 by Pd-mediated coupling and treatment of the resulting
diol with PBr3, is also structurally preconditioned to undergo
a 1,8-elimination (Scheme 11).
Indeed, on treatment with 14/CsF under the usual condi-
tions, a 1:1 mixture of the two isomeric cyclophanes 45 and
46 is obtained in a combined yield of 4.5%. All attempts to
separate the two isomers failed.
Scheme 11. Paracyclophandiynes by a 1,8-elimination.
Still, they can be readily distin-
guished by the signals for the
methylene protons in their
1H NMR spectra, which are
registered as singlets for the
head-to-head dimer of 44, hy-
drocarbon 45, and as triplets for
the head-to-tail dimer 46 (see
Experimental Section). Since
these signals are well separated,
they can also be used to deter-
mine the ratio of the two re-
gioisomers, which is approxi-
mately 1:1, that is, there is no
selectivity in the dimerization
of 44.
1,10-Eliminations: Two types of
1,10-eliminations were carried
out: in the first type an aromat-
ic ring system was part of the
spacer unit, whereas in the
second category heteroaromat- Scheme 12. Carbocyclic paracyclophanes by a 1,10-elimination.
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1,x-Elimination Reactions
FULL PAPER
clophane tetrayne were obtained. However, when we
changed the solvent to acetonitrile, 49 was produced in 46%
yield, allowing the preparation of 25 mg batches per experi-
ment. The reason for this drastic increase in yield is unclear
at present. It was observed that 14/CsF forms two phases
with acetonitrile, and possibly the cumulenic intermediate
48 migrates into the acetonitrile phase, where, because of
concentration effects, intramolecular dimerization is pre-
ferred over a side product producing intermolecular oligo-
merization. Interestingly, in THF we could isolate 1-(3-
fluoro-1-propynyl)-4-(1-propnyl)benzene as a side product
(5%), a formal 1,10-addition product of HF to 48. Unfortu-
nately the solvent effect was discovered at a late stage of
this investigation, so that most debrominations were per-
formed in DMF.
The X-ray structure of 49 has already been briefly dis-
cussed in a short communication describing its formation
from 47.[18] The compound displays two independent mole-
cules, each with crystallographic inversion symmetry
(Figure 1)and thus with exactly parallel six-membered rings.
The molecular conformations are however different; in mol-
ecule 1 the rings are eclipsed (torsion angle C2-C1-C12#1-
C11#1 9.9(8)8)with an intercentroid distance of 3.84 Š, but
in molecule 2 the larger torsion angle of 41.9(5)8 causes the
rings to be laterally displaced, with an intercentroid distance
of 4.00 Š but a perpendicular separation of only 3.43 Š. The
angle between the ring plane and the plane of the immedi-
ate substituents in the phane bridges (C3, C10 and equiva-
lents)is 89.1(1) 8 in molecule 1 but only 55.3(1)8 in molecule
2. It is noteworthy that, given the inversion symmetry, this
interplanar angle and the torsion angle about the single
bond are the only real degrees of freedom in the molecule.
The molecular strain is seen not in any non-planarity of the
six-membered rings (<0.02 Š)but rather in the displace-
ment of the substituents out of the ring planes (by 0.21–
0.28 Š)and the distorted “linear” bond angles of 169–172 8
(av. 170.28)at the triple bond systems.
The main feature of the packing of 49 is a C-H···p interac-
ꢀ
ꢀ
tion from C12 H12B to the centroid of the ring C4’ C9’,
ꢀ
with H···Cent 2.82 Š (C H normalised to 1.08 Š), angle
1448, operator x,1+y,z.
A surprising result was also noted in the reductive cycliza-
tion of the naphthalene derivative 50. Not only did the di-
merization take place with a surprising yield of 51%, but it
provided, as shown by X-ray analysis, one isomer only: the
syn-configured hydrocarbon 52. Intuitively one would have
predicted the preferred production of the anti-isomer, even
more so since in the synthesis of the parent system [2.2]-
A
preferentially[19] or exclusively.[20]
The structure of compound 52 is not of high quality; de-
spite low temperature measurements, the displacement pa-
rameters are high, especially around the single bonds of the
phane bridges, and libration effects are severe. Combined
with the effects of the non-centrosymmetric space group,
this makes the data weak, and results should be interpreted
with caution. Nevertheless, the unexpected syn configuration
(Figure 2)is unequivocally established. There is no imposed
Figure 2. Structure of compound 52 in the crystal, seen from two alterna-
Figure 1. Structure of compound 49 in the crystal. Top: molecule 1; ellip-
soids represent 30% probability levels. Bottom: molecule 2, arbitrary
radii. Only the asymmetric unit is numbered. Dimensions at the triple
tive view directions. Ellipsoids represent 30% probability levels. Dimen-
ꢀ
ꢀ
sions at the triple bond systems [Š, 8]: C1 C2 1.193(13), C5 C6
ꢀ
ꢀ
1.168(12), C17 C18 1.176(12), C21 C22 1.184(13), C2-C1-C26 169.2(11),
C1-C2-C3 169.0(11), C4-C5-C6 170.7(13), C5-C6-C7 167.9(10), C10-C17-
C18 172.3(10), C17-C18-C19 167.0(11), C20-C21-C22 166.5(13), C21-C22-
C23 172.4(11).
ꢀ
bond systems [Š, 8; values for two molecules]: C2 C3 1.189(5), 1.186(6),
ꢀ
C10 C11 1.176(5), 1.192(5), C1-C2-C3 169.6, 169.1, C2-C3-C4 172.0,
170.4, C7-C10-C11 170.4, 169.8, C10-C11-C12 169.9, 170.7 (all esdꢀs 0.58).
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H. Hopf et al.
symmetry, but the naphthalene ring systems are approxi-
mately parallel (interplanar angle 4.1(4)8); they are mutually
Debromination of 57a and b furnished the heterophanes
59a and b in acceptable yield, although the reaction was car-
ried out in DMF. Again, we postulate the formation of cu-
mulenes (58a and b)as reactive intermediates. Both dimers
(for the spectroscopic data see the experimental section)
were stable enough to be recrystallized, allowing the prepa-
ration of single crystals suitable for X-ray structural analysis
(see below). The two heterophanes can be kept under inert
gas for several months at room temperature; however, when
exposed to air the surface of the crystals turns brown within
minutes and black on extended oxygen contact.
displaced
such
that
the
phane-substituted
ring
C7,8,9,10,11,16 overlaps with the ring C27–C32, with an in-
tercentroid distance of 3.55 Š. The torsion angles about the
single bonds are ꢀ5(2)8 about C3-C4 and ꢀ24(2)8 about
ꢀ
C19 C20 (but see the above caveat). The angles between
the naphthalene ring planes and the substituent plane
(C1,6,17,22)are 56.6(2)and 60.6(2) 8. The substituent atoms
are displaced from the ring planes by 0.22–0.28 Š, and the
triple bond angles lie in the range 166–1738 (av. 169.48). The
packing involves no noteworthy contacts.
The furan derivative 59a displays crystallographic inver-
sion symmetry (Figure 3)and the rings are thus exactly par-
The other analytical and spectroscopic data confirm the
structure assignment of 52 (see Experimental Section).
The formation of the anthracenophane 55 from dibromide
53 took place as expected (in DMF, Scheme 12). However,
this dimer is chemically extremely sensitive. The presence of
air is especially detrimental, and the purification of 55 by
column chromatography was only successful if both the
silica gel and the eluents had been degassed prior to use.
Even then the column material turned black during chroma-
tography, and the change to flash vacuum chromatography
and coarser silica gel led to no real improvement. From an
oxygen-free solution of 55 in CDCl3, yellow-green crystals
precipitated in the cold. However, on contact with air and/
or in the presence of daylight these were converted into in-
soluble, black material. [4+4]Cycloadditions of [2.2]anthra-
cenophane have been reported in the literature, and possibly
comparable reactions also take place here.[21]
The heterocyclic bis-propargylic bromides 57a and b were
prepared by coupling 2,5-dibromofuran (56a)and its thio-
phene analogue 56b with the protected propargyl alcohol 29
and treating the resulting bis-THP ethers with triphenyl-
phosphine and bromine; in both cases the total yields were
in the 60–70% range (Scheme 13). Although the corre-
sponding N-methyl pyrrol bis-ether could be prepared, its
conversion to the dibromide failed. It should be pointed out
that some of these intermediates could be toxic; for example,
when small amounts of 56a were inhaled during the prepa-
rative work, nausea immediately set in.
ꢀ
allel. The torsion angle of 48.9(2)8 about C5 C6 leads to an
extreme lateral displacement of the rings (intercentroid dis-
tance 5.98 Š). In contrast to the previous two structures, in
which the ring systems subtended large angles to the plane
of their four immediate substituents, the furan rings lie ap-
proximately parallel to the plane of C3, C8 and their equiva-
lents (interplanar angle 10.4(1)8). The intramolecular O···O
distance is 3.645(2)Š. The geometrical requirements of the
five-membered rings are significantly different from those of
the six-membered rings in the two previous structures; the
vectors corresponding to an extension of the substituent
ꢀ
bonds (here C8 C9 and C2#1-C3#1)subtend an angle of 55 8
rather than being approximately parallel to each other. It
seems that this is sufficient to relieve the worst of the strain
seen in 49 and 52; the ring substituents lie only 0.03–0.06 Š
out of the ring plane, and the triple bond angles are almost
ideally linear at 176.3–177.38. There are no exceptional in-
termolecular contacts.
Figure 3. Structure of compound 59a in the crystal, seen from two alter-
native view directions. Ellipsoids represent 30% probability levels. Only
the asymmetric unit is numbered. Dimensions at the triple bond systems
ꢀ
ꢀ
[Š, 8]: C3 C4 1.193(2), C7 C8 1.192(2), C2-C3-C4 176.34(16), C3-C4-C5
176.96(16), C6-C7-C8 177.06(15), C7-C8-C9 177.30(15).
Scheme 13. Heteroaromatic paracyclophanes by a 1,10-elimination.
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1,x-Elimination Reactions
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Having rationalised the structure of 59a to some extent, it
is disappointing that the structure of 59b is so irregular and
does not conform to the same principles. The molecule
(Figure 4)has no imposed symmetry and the interplanar
In a final 1,10-elimination a crossing experiment was car-
ried out. Thus an equimolar mixture of the dibromides 50
and 57b was treated in acetonitrile with the Mori reagent at
room temperature. Since the debromination should lead to
a mixture of 51 and 58b we expected the formation of one
hetero- and two homodimers (Scheme 14).
Scheme 14. Mixed paracyclophanes by a crossing experiment.
This is indeed the case. The homodimers 52 (9.5%)and
59b (2.7%)were identified by comparison with the authen-
tic products (see above), and the structure of the main prod-
1
uct 60 (10%; product composition by H NMR analysis)was
derived from its spectroscopic data (see Experimental Sec-
tion). Unfortunately a complete separation of the three cy-
clodimers was not possible: on silica gel the three com-
pounds possess practically the same Rf values. They could
be enriched, however, when the silica gel had been impreg-
nated with picric acid. The separation is additionally made
difficult by the instability of 60.
Figure 4. Structure of compound 59b in the crystal, seen from two alter-
native view directions. Ellipsoids represent 30% probability levels. Di-
ꢀ
ꢀ
mensions at the triple bond systems [Š, 8]: C3 C4 1.188(3), C7 C8
ꢀ
1.191(3), C12 C13 1.185(3), C16-C17 1.195(3), C2-C3-C4 169.5(2), C3-
C4-C5 172.6(2), C6-C7-C8 170.8(2), C7-C8-C9 172.6(2), C11-C12-C13
171.0(2), C12-C13-C14 171.4(2), C15-C16-C17 174.7(2), C16-C17-C18
172.4(2).
1,14- and higher eliminations: Not unexpectedly, with grow-
ing distance between the two groups to be eliminated it be-
comes more difficult to observe and isolate 1,x-elimination
products. Still, as several of the following examples demon-
strate the process does not yet break down.
Whereas the starting dibromide 64 could be prepared
readily and in good yield via the doubly protected tetrayne
63 (itself obtain by Cadiot–Chodkiewicz coupling of 61 with
the 1-bromo alkyne 62, Scheme 15), its debromination did
not yield the desired cyclophane 65.
From the product mixture we could isolate an extremely
unstable component that might have been 65 (soluble in or-
ganic solvents, Rf value comparable with structurally similar
compounds such as 49). However, it decomposed to a black,
insoluble material before we could obtain its spectroscopic
data. The feasibility of 1,14-eliminations when the number
of triple bonds is reduced in starting materials and products
was demonstrated with the biphenyl derivative 68, prepared
by the established protocol from the commercial substrate
66 via the bis-ether 67. The cyclophane could not only be
purified by column chromatography, but it is stable under
angle between the thiophene rings is 25.5(1)8; the intercent-
roid distance is 5.00 Š and the intramolecular S···S distance
ꢀ
ꢀ
is 3.4966(5)Š. The torsion angles about C5 C6 and C14
C15 are 52.5(3)and ꢀ49.0(3)8 respectively. The intervector
ꢀ
ꢀ
ꢀ
ꢀ
angles C2 C3/C17 C18 and C8 C9/C11 C12 are both 388
(appreciably less than in 59a). In other respects the two
rings differ considerably. For the ring based on S1, the sub-
stituents C3 and C17 lie only 0.08 and 0.11 Š out of the ring
plane and the interplanar angle to the plane of all four sub-
stituent atoms (C3,8,12,17)is 39.9(1) 8. For the ring based on
S10, the corresponding distances are 0.21, 0.28 Š for C8 and
C12, and the corresponding angle is 65.4(1)8. The triple
bond angles of 169.5–174.78 (av. 171.98)show some strain. It
is possible that the following intermolecular contacts may be
associated with the irregularities: C20-H20···Cent(S1-ring)
G
1
with H···Cent 2.70, angle 1398, operator = ꢀx,1= +y,z; C6-
2
2
1
H6B···S1 with H···S 2.71, angle 1448, operator = +
2
x,1= ꢀy,1ꢀz; C21-H21···S10 with H···S 2.82, angle 1498, oper-
2
ator 1ꢀx,ꢀ = +y,1= ꢀz.
1
2
2
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9469

H. Hopf et al.
Scheme 15. 1,14-Eliminations leading to novel extended paracyclophanes.
inert gas for extended periods of time. Unfortunately we
could not obtain crystals of X-ray quality; its structure is
clearly shown by the spectroscopic data (Experimental Sec-
tion). Formally connecting two ortho-positions in 68 by a
methylene group leads to 70, which on debromination with
Mori reagent in DMF provides small amounts of the fluore-
nophane 71 (2.5%). The determination of its exact structure
(syn- or trans-configured, see 52 and 59a, b above), awaits
the preparation of single crystals for X-ray structural analy-
sis. Provided that sufficient amounts of the hydrocarbon can
be obtained, its conversion into metallocenophanes is also
of interest.
For a final 1,14-elimination we prepared the thiophene
derivative 74 from the diacetylene 72 as described in
Scheme 16. Again, the preparation of the precursor com-
pounds could be carried out in satisfactory yields.
Dimerization of 74 to the thiaphane 75 took place in ac-
ceptable yield (18%), although the compound could not be
obtained free of solvent. Like its sister molecule 65 it quick-
ly decomposes to a black material and, as in 71, the orienta-
tion of the (hetero)aromatic decks remains undetermined
for the time being.
In a last series of experiments we tried to find experimen-
tal hints for the occurrence of a 1,16- and a 1,20-elimination,
and selected the two dibromides 76 and 77 (Scheme 17)for
that purpose.
Scheme 16. Preparation of an extended thiaphane by 1,14-elimination.
Both precursors were again prepared without problems
from commercially or easily available substrates by the cou-
pling processes described above. However, in neither case
did the debromination lead to cyclodimerization products.
Since lack of stability is an unlikely cause for this, we pro-
pose that the above concept of “extended eliminations” has
reached its limit with 74, that is, with a 1,14-elimination pro-
cess.
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1,x-Elimination Reactions
FULL PAPER
a short silica gel column and the solvent was removed by rotary evapora-
tion. The resulting residue was purified by column chromatography.
General procedure 3 (GP 3): Elimination reactions with Moriꢀs reagent:
The dihalide (1 mmol)and cesium fluoride (1.5 mmol)were dissolved at
room temperature under nitrogen in the appropriate anhydrous solvent
(in most experiments: DMF). To this solution was added tributyl(trime-
thylsilyl)stannane (14, 1.5 mmol)within 1 h. After stirring for an addi-
tional 4 h at room temperature dichloromethane (100 mL)was added to
the reaction mixture, followed by 10% aqueous ammonia solution
(300 mL), and the aqueous phase was thoroughly extracted with dichloro-
methane. The organic phases were combined, dried, and filtered through
silica gel. The elimination product (hydrocarbon)was purified by column
chromatography (silica gel).
1,6-Dibromo-2,4-hexadiyne (17): According to GP 1 1,6-dihydroxy-2,4-
hexadiyne (16, 1.33 g (12.1 mmol)was treated in dichloromethane
(100 mL)with triphenylphosphine (7.6 g, 29.0 mmol)and bromine
(1.33 g, 29.0 mmol). After work-up 17 (2.3 g, 81%)was isolated as a col-
orless oil that solidifies in the refrigerator. M.p. ca. 08C; 1H NMR
(400 MHz, CDCl3): d=3.99 ppm (s, 4H, 1-, 6-H); 13C NMR (100 MHz,
CDCl3): d=13.96 (t, C-1, -6), 70.29 (s, C-3, -4), 75.27 ppm (s, C-2, -5); IR
(film): n˜ =2954 (s), 2924 (s), 2852 (s), 2256 (w), 2155 (w), 1198 (s),
608 cmꢀ1 (vs); UV (acetonitrile): lmax (log e)=200 (4.41), 262 nm (3.65);
MS (70 eV): m/z (%): 238 (20) [M+], 236 (38)[ M+], 234 (20)[ M+], 157
(98), 155 (100), 76 (52); elemental analysis calcd (%) for C6H4Br2: C
30.55, H 1.71; found: C 30.42, H. 1.58.
Scheme 17. Attempted 1,16- and 1,20-eliminations.
Conclusion
Recently the concept of “expanded structures” has received
increasing attention in the chemical literature. Typical exam-
ples are the [N]pericyclynes,[22] “exploded” radialenes,[23] ex-
panded cubanes[24] or the aromatic ring carbomers.[25] With
this publication we wish to extend this concept in the literal
sense and suggest applying it to chemical reactivity as well.
For example 1,12-additions of organocuprates to extended
unsaturated esters have already been reported.[26] In the
area of substitutions reactions, several 1,5-processes have
been described.[27]
1,3,7,9-Cyclododecatetrayne (20): According to GP 3 17 (1.00 g,
4.24 mmol)was treated with 14 (2.31 g, 6.36 mmol)and cesium fluoride
(0.97 g, 6.36 mmol)in DMF (70 mL), giving 20 (64 mg, 10%)as colorless
plates that turned brown in air and then black quickly. 1H NMR
(400 MHz, CDCl3): d=2.63 ppm (s, -CH2-); 13C NMR (100 MHz, CDCl3):
d=19.84 (t, C-5, -6, -11, -12), 72.94 (s, C-3, -3, -8, -9), 86.58 ppm (s, C-1,
-4, -7, -10); GC/MS (40 eV): m/z (%): 152 (100) [M+], 76 (54). A sample
of 20 (16 mg, 0.11 mmol)was dissolved in degassed ethyl acetate (50 mL)
and hydrogenated over Pt under normal pressure at room temperature.
After 12 h the catalyst was removed by filtration, the solvent was re-
moved in vacuo and the residue (15 mg, 86%)identified as cyclodode-
cane by GC/MS comparison with an authentic sample.
It appears likely that many other examples can be de-
signed and subsequently developed in the chemical labora-
tory.
[2.6]Orthocyclophan-1,5-diyne (26)
a) ortho-(3-Bromopropynyl)benzyl bromide (24): A solution of ortho-io-
dobenzyl alcohol (22, 5.0 g, 21.3 mmol), propargyl alcohol (23, 2.5 mL,
46.5 mmol), and [Pd(PPh3)4] (1.23 g, 1 mmol)in anhydrous propylamine
A
Experimental Section
(100 mL)was refluxed under nitrogen for 1.5 h. The reaction mixture
was cooled to room temperature and hydrolyzed with saturated aqueous
ammonium chloride solution (200 mL). After thorough extraction with
Et2O and dichloromethane the organic phases were combined, the solu-
tion filtered through a pad of silica gel, and the solvent evaporated in
vacuo. Column chromatography (silica gel, Et2O)provided o-(3-hydroxy-
propynyl)benzyl alcohol (3.2 g, 93%) as colorless crystals. M.p. 63 8C;
1H NMR (400 MHz, CDCl3): d=3.44 (s, 1H, OH), 3.77 (s, 1H, OH), 4.42
(s, 2H, -CH2-), 4.74 (s, 2H, -CH2-), 7.22–7.41 ppm (m, 4H, arom. H);
13C NMR (100 MHz, CDCl3): d=51.17 (t), 63.65 (t), 82.97 (s), 92.02 (s),
121.35 (s), 127.59 (d), 127.87 (d), 128.73 (d), 132.28 (d), 142.29 ppm (s);
IR (KBr): n˜ =3314 (vs), 3307 (vs), 2232 (vw), 1635 (s), 1629 (s), 1042
(vs), 1025 (vs), 757 cmꢀ1 (vs); UV (acetonitrile): lmax (log e)=196 (sh,
4.21), 206 (4.36), 244 (4.07), 250 nm (sh, 4.00); MS (70 eV): m/z (%): 162
(8)[ M+], 144 (78), 115 (100); elemental analysis calcd (%) for C10H10O2
(162.19): C 74.05, H 6.21; found: C 74.32, H 6.22.
General remarks: Column chromatography: Silica gel 60 (70–230 mesh,
Merck); aluminium oxide, activity II–III (Woelm). Melting points: Kofler
hot stage (uncorr.)NMR: Bruker AC 200
(
1H: 200 MHz; 13C:
50.3 MHz); Bruker AM 300 (1H: 300 MHz; 13C: 75.5 MHz); Bruker WM
400 and Bruker AM 400 (1H: 400 MHz; 13C: 100.6 MHz)in CDCl 3, TMS
as internal standard. IR: Perkin-Elmer 1420 as KBr pellets. MS: Finnigan
MAT 84530 (70 eV, EI). UV: Beckman UV 5230.
General procedure 1 (GP 1): Preparation of propargyl bromides: Bro-
mine (1.2 equiv)was added under nitrogen at 0 8C to a solution of triphe-
nylphosphine (1.2 equiv)in anhydrous dichloromethane (100 mL.) After
stirring for 5–10 min a slightly yellow homogenous solution had formed,
to which the appropriate propargyl alcohol (1 equiv)or its THP ether
(see GP 2)was added, if necessary dissolved in a small amount of di-
chloromethane. After stirring for 1 h at 08C, the reaction was completed
by stirring for an additional hour at room temperature. The solution was
passed through a pad of silica gel, and the solvent was removed by rotary
evaporation. For further purification the propargyl bromides were puri-
fied by chromatography on silica gel.
To a solution of this diol (3.0 g, 18.5 mmol)in anhydrous Et 2O (40 mL),
cooled to 08C, was added under nitrogen PBr3 (1.3 mL, 13.6 mmol)to
which pyridine (0.1 mL)had been added. After stirring for 1 h at 0 8C,
the reaction mixture was refluxed for an additional hour. To the cooled
solution was added saturated aqueous sodium bicarbonate solution
(100 mL), and the mixture was thoroughly extracted with Et2O. The com-
bined organic phases were filtered through silica gel, the solvent was re-
moved by rotary evaporation, and the remaining crude product purified
by column chromatography (silica gel, petrol ether): 24 (3.7 g, 70%)as
colorless needles. M.p. 378C; 1H NMR (400 MHz, CDCl3): d=4.21 (s,
2H, -CH2-), 4.64 (s, 2H, -CH2-), 7.26–7.44 ppm (m, 4H, arom. H);
General procedure 2 (GP 2): Coupling of halides with 2-(2-propynyloxy)-
3,4,5,6-tetrahydro-2H-pyran (29): The appropriate aryl halide (5 mmol),
ether 29 (6.25 mmol), 1–4 mol% of [Pd(PPh3)4], and 2–8 mol% of CuI
R
were dissolved in anhydrous triethylamine (50 mL), and the solution
heated to 808C for 1–8 h. The reaction mixture was hydrolyzed with satu-
rated aqueous ammonium chloride solution (300 mL), and extracted sev-
eral times with Et2O. The combined organic layers were filtered through
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H. Hopf et al.
13C NMR (100 MHz, CDCl3): d=14.93 (t), 31.52 (t), 83.75 (s), 89.74 (s),
121.93 (s), 128.40 (d), 129.36 (d), 129.74 (d), 132.79 (d), 139.66 ppm (s);
IR (KBr): n˜ =3058 (w), 3026 (w), 2221 (m), 1485 (vs), 1449 (s), 1218 (vs),
1202 (vs), 1192 (vs), 765 cmꢀ1 (vs); UV (acetonitrile): lmax (log e)=218
(4.39), 258 nm (4.10); MS (70 eV): m/z (%): 290 (12) [M+], 288 (19)[ M+],
286 (12)[ M+], 209 (98), 207 (100), 128 (98); elemental analysis calcd
(%)for C 10H10Br2: C 41.71, H 2.80; found: C 41.23, H 2.99.
9.6 mmol). After work-up (see GP 3), the crude product was pre-purified
by column chromatography on silica gel with dichloromethane. A second
chromatography (silica gel, pentane)provided 41 (0.3 g, 62%)as color-
less needles. The hydrocarbon polymerized quickly at room temperature
yielding
a
solid material that did not melt below 3008C. 1H NMR
(400 MHz, CDCl3): d=2.99 (s, 4H, -CH2CH2-), 7.27–7.28 ppm (AA’BB’-
m, 4H, arom. H); 13C NMR (100 MHz, CDCl3): d=20.98 (t), 96.14 (s),
110.99 (s), 126.59 (d), 127.42 (d), 131.74 ppm (s); IR (KBr): n˜ =3079 (w),
2922 (w), 2159 (s), 1555 (vs), 1540 (m), 1450 (vs), 1438 (vs), 1420 (vs),
1282 (s), 1033 (s), 751 cmꢀ1 (vs); UV (acetonitrile): lmax (log e)=200
(4.38), 222 (4.28), 232 (4.43), 250 nm (sh, 4.12); MS (70 eV): m/z (%):
152 (100)[ M+], 126 (18). When the debromination experiment was re-
peated in the presence of dimethyl acetylene dicarboxylate as trapping
reagent no addition product(s)was (were)obtained.
b) Debromination of 24 to 26: According to GP 3 24 (1.0 g, 3.48 mmol)
was treated with cesium fluoride (0.58 g, 3.85 mmol)and 14 (1.39 g,
3.85 mmol)at 0 8C. After stirring for 24 h at room temperature the reac-
tion mixture was hydrolyzed and worked-up (see GP 3). After solvent re-
moval in vacuo the remaining oil was purified by radial chromatography
(silica gel, petrol ether), giving 26 (10 mg, 2.2%)as colorless, microcrys-
talline solid. 1H NMR (400 MHz, CDCl3): d=2.75 (s, 4H, -CH2CH2-),
3.07 (s, 4H, -CH2CH2-), 7.16–7.39 ppm (m, 4H, arom. H); 13C NMR
(100 MHz, CDCl3): d=19.66 (t), 37.72 (t), 81.05 (s), 91.87 (s), 122.94 (s),
125.99 (d), 128.11 (d), 129.24 (d), 131.50 (d), 144.72 ppm (s); IR (KBr):
n˜ =3061 (w), 3018 (w), 2923 (m), 2191 (w), 1705 (s), 1483 (s), 1449 (s),
1069 (s), 1043 cmꢀ1 (s); UV (acetonitrile): lmax (log e)=210 (4.58), 240
(4.32), 252 nm (4.10); MS (70 eV): m/z (%): 256 (100) [M+], 241 (58),
228 (28); HRMS: m/z: calcd for C20H16: 256.12500, found: 256.125. The
isomer 27 could never be completely separated from side-products. The
1H NMR data mentioned in the main section indicated its formation, as
do signals in the IR and MS spectra comparable to those reported for 26.
A
a) p-(3-Bromopropynyl)-benzyl bromide (43): As described for the con-
version of 22 into 24 above, p-bromobenzyl alcohol (42)was converted
into dibromide 43 in an overall yield of 35%. After chromatography
(silica gel, petrol ether)it was obtained in the form of colorless needles.
M.p. 648C; 1H NMR (400 MHz, CDCl3): d=4.16 (s, 2H, -CH2-), 4.47 (s,
2H, -CH2-), 7.34–7.41 ppm (AA’XX’-m, 4H, Jm =3.5, Jp =8.3 Hz);
13C NMR (100 MHz, CDCl3): d=15.03 (t), 32.69 (t), 85.03 (s), 86.07 (s),
122.22 (s), 128.99 (d), 132.21 (d), 138.42 ppm (s); IR (KBr): n˜ =3030
(vw), 2970 (vw), 2266 (vw), 2215 (w), 1508 (m), 1412 (m), 1276 (m), 1225
(s), 1194 (s), 841 (s), 603 cmꢀ1 (vs); UV (hexane): lmax (log e)=196
(4.44), 204 (sh, 4.38), 266 nm (4.37); MS (70 eV): m/z (%): 290 (8) [M+],
288 (14)[ M+], 286 (7)[ M+], 209 (80), 207 (82), 128 (100); elemental
analysis calcd (%)for C 10H8Br2: C 41.71, H 2.80; found: 41.23, H 2.70.
1,9-Cyclohexadecadien-3,7,11,15-tetrayne (33): According to GP 3 (Z)-
1,8-dibromo-4-octen-2,6-diyne (31, 1.0 g, 3.81 mmol), prepared from (Z)-
[14]
1,2-dichloroethene (28)by the method of Kçnig et al.,
was debromi-
nated with 14 (2.07 g, 5.72 mmol)and cesium fluoride (0.87 g, 5.72 mmol)
in DMF (50 mL). After work-up hydrocarbon 33 (ca. 40 mg, 5%)was ob-
tained, which started to decompose rapidly at room temperature.
1H NMR (400 MHz, CDCl3): d=2.58 (s, 8H, -CH2CH2-), 5.95 ppm (s,
4H, -CH=CH-); GC/MS (40 eV): m/z (%): 204 (35) [M+], 202 (100),
189 (15), 152 (10), 102 (268), 76 (30).
b) Debromination of 43 to 45/46: According to GP 3 43 (1.0 g,
3.47 mmol)was debrominated with 14 (1.26 g, 3.47 mmol)and cesium
fluoride (0.53 g, 3.47 mmol)in anhydrous DMF (50 mL)at ꢀ308C. The
reaction mixture was brought to room temperature and stirred for 2 d.
After work-up as described above, the product mixture was pre-purified
by column chromatography on silica gel with dichloromethane and subse-
quently fractionated by radial chromatography (silica gel, petrol ether):
1:1 mixture of 45 and 46 (20 mg, 4.5%)as colorless needles. The follow-
ing spectroscopic data were derived from the hydrocarbon mixture.
1H NMR (400 MHz, CDCl3)for 45: d=2.67 (s, 4H, -CH2CH2-), 2.98 (s,
4H, -CH2CH2-), 6.82–6.91 ppm (AA’XX’-m, 8H, arom. H); 13C NMR
(100 MHz, CDCl3)for 45: d=19.74 (t), 34.33 (t), 86.09 (s), 92.7 (s),
121.82 (s), 128.99 (d), 130.96 (d), 139.25 ppm (s); 1H NMR (400 MHz,
CDCl3)for 46: d=2.68 (t, 4H, J=7.0 Hz, -CH2CH2-), 2.92 (t, 4H, J=
7.0 Hz, -CH2CH2-), 6.51–6.82 ppm (m, 4H, arom. H); 13C NMR
(100 MHz, CDCl3)for 46: d=20.30 (t), 33.01 (t), 88.12 (s), 94.75 (s),
121.82 (s), 130.85 (d), 131.10 (d), 140.35 ppm (s); IR (KBr) for 45/46: n˜ =
3073 (w), 3038 (w), 2947 (s), 2924 (vs), 2855 (s), 2216 (w), 1506 (vs), 1408
(m), 1095 (m), 815 (s), 723 cmꢀ1 (s); UV (acetonitrile) for 45/46: lmax
(log e)=194 (4.60), 198 (4.59), 240 (sh, 4.33), 246 (4.38), 260 nm (4.05);
MS (70 eV)for 45/46: m/z (%): 256 (76) [M+], 241 (20), 152 (8), 128
(100), 102 (18); HRMS: m/z: calcd for C20H16: 256.1252; found: 256.125.
A sample of 33 (10.0 mg, 0.05 mmol)was dissolved in degassed ethyl ace-
tate (20 mL), and the solution hydrogenated under normal pressure over
platinum for 20 h at room temperature. After solvent removal by rotary
evaporation 36 (10 mg, 89%)was obtained, identical in its GC/MS be-
havior with a sample prepared by hydrogenation of commercial cyclohexa-
deca-1,3-diene.
For a Bergman cyclization a few mg of 33 was dissolved in 1,4-cyclohexa-
diene (1 mL)and the solution heated in a sealed ampoule to 200 8C.
Analysis of the pyrolysate by GC/MS revealed peaks that agreed with
those expected for 34, but since no authentic material was available for
comparison the experiment remained ambiguous.
3,4-Benzocycloocta-3-en-1,5-diyne (41)
a) 1,2-Bis-(3-bromo-1-propynyl)benzene (38):
(1.66 mL, 17.7 mmol)and pyridine (0.1 mL)was added under nitrogen at
08C to solution of 1,2-bis-(3-hydroxy-1-propynyl)benzene (4.50 g,
A mixture of PBr3
a
24.2 mmol), prepared from the coupling of propargyl alcohol (23)with
ortho-dibromobenzene (37)according to ref. [28],) in anhydrous Et 2O
(20 mL). After stirring for 1 h at that temperature the bromination was
completed by refluxing the reaction mixture for 1 h. The red product
mixture was hydrolyzed with saturated aqueous sodium bicarbonate solu-
tion (100 mL), and the aqueous phase was thoroughly extracted with
Et2O. The combined organic phases were filtered through silica gel, and
the solvent was removed. Column chromatography (silica gel, dichloro-
methane/petrol ether 5:2)furnished colorless 36 (4.5 g, 60%)as low
melting needles. M.p. 30–338C; 1H NMR (400 MHz, CDCl3): d=4.22 (s,
4H, -CH2-), 7.28–7.43 ppm (AA’BB’-m, 4H, arom. H); 13C NMR
(100 MHz, CDCl3): d=15.06 (t), 84.93 (s), 88.36 (s), 125.05 (s), 128.78
(d), 131.91 ppm (d); IR (KBr): n˜ =3061 (w), 3008 (w), 2227 (w), 1719
(m), 1655 (m), 1637 (m), 1592 (m), 1480 (s), 1440 (s), 1291 (s), 1202 (vs),
983 (s), 759 (vs), 609 cmꢀ1 (vs); UV (acetonitrile): lmax (log e)=198
(4.27), 243 (4.44), 268 nm (4.12); MS (70 eV): m/z (%): 314 (10) [M+],
312 (20)[ M+], 310 (10)[ M+], 233 (82), 231 (83), 152 (100); elemental
analysis calcd (%)for C 12H8Br2: C 46.20, H 2.58; found: C 46.21, H 2.42.
A
a) 1,4-Bis-(3-bromo-1-propynyl)benzene (47): A solution of 1,4-dibromo-
benzene (10.0 g, 42.3 mmol), propargyl alcohol (23, 7.6 mL, 0.13 mol)and
of [Pd(PPh3)4] (1.27 g, 1.1 mmol)in propylamine (130 mL)was refluxed
U
under nitrogen for 3 d. For work-up the reaction mixture was hydrolyzed
with saturated aqueous sodium bicarbonate solution (200 mL), extracted
thoroughly with Et2O, and the combined organic phases dried with mag-
nesium sulfate. Solvent removal provided a solid residue that was recrys-
tallized from Et2O to yield colorless plates (7.5 g, 94%). M.p. 1228C;
1H NMR (400 MHz, CDCl3): d=4.39 (s, 4H, -CH2-), 7.37 ppm (s, 4H,
arom. H); 13C NMR (100 MHz, CDCl3): d=52.74 (t), 86.43 (s), 92.27 (s),
125.86 (s), 134.1 ppm (d); IR (KBr): n˜ =3359 (s), 3363 (s), 2904 (w), 2241
(w), 1507 (s), 1497 (s), 1440 (m), 1425 (s), 1030 (vs), 839 cmꢀ1 (s); UV
(acetonitrile): lmax (log e)=196 (4.36), 212 (4.26), 218 (4.24), 268 (4.56),
280 (4.60), 294 nm (3.36); MS (70 eV): m/z (%): 186 (100) [M+], 169
(12), 157 (32), 128 (44); elemental analysis calcd (%) for C12H8O2: C
77.40, H 5.41; found: C 77.55, H 5.40. To a solution of this diol (5.0 g,
b) Debromination of 38 to 41: According to GP 3 38 (1.0 g, 3.2 mmol)
was debrominated with 14 (3.50 g, 9.6 mmol)and cesium fluoride (1.47 g,
26.9 mmol)in anhydrous Et 2O (30 mL)was added a mixture of PBr
3
9472
www.chemeurj.org
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 9462 – 9477

1,x-Elimination Reactions
FULL PAPER
(1.85 mL)and pyridine (0.1 mL)at 0 8C. After stirring for 30 min at this
temperature the reaction was completed by refluxing the mixture for fur-
ther 30 min. The product mixture was hydrolysed (100 mL of saturated
aqueous sodium bicarbonate solution), the phases were separated and
the aqueous phase thoroughly extracted with ether. The combined organ-
ic layers were dried (magnesium sulfate), the solvent was removed in
vacuo, and the residue purified by column chromatography (silica gel,
petrol ether): 47 (5.7 g, 68%)as colorless needles. M.p. 103 8C; 1H NMR
(400 MHz, CDCl3): d=4.16 (s, 4H, -CH2-), 7.38 ppm (s, 4H, arom. H);
13C NMR (100 MHz, CDCl3): d=14.9 (t), 85.97 (s), 86.20 (s), 122.55 (s),
131.72 ppm (d); IR (KBr): n˜ =3000 (w), 2926 (vw), 2270 (vw), 2218 (m),
1505 (m), 1274 (m), 1199 (vs), 831 (s), 601 cmꢀ1 (s); UV (hexane): lmax
(log e)=196 (4.46), 218 (4.24), 282 (4.54), 290 nm (sh, 4.51); MS (70 eV):
m/z (%): 314 (10) [M+], 312 (20)[ M+], 310 (9), [M+], 233 (95), 231 (93),
152 (100); elemental analysis calcd (%) for C 12H8Br2: C 46.20. H 2.58;
found: C 46.30, H 2.80.
decomp. at 1008C. 1H NMR (400 MHz, CDCl3): d=2.91 (s, 8H,
-CH2CH2-), 6.75 (s, 4H, arom. H), 7.21–8.11 ppm (AA’BB’-m, 8H, arom.
H); 13C NMR (100 MHz, CDCl3): d=19.86 (t), 84.64 (s), 95.71 (s), 121.12
(s), 125.90 (d), 126.06 (d), 128.62 (d), 132.37 ppm (s); IR (KBr): n˜ =3059
(w), 2925 (w), 2212 (w), 1568 (w), 1384 (m), 836 (s), 764 cmꢀ1 (s); UV
(acetonitrile): lmax (log e)=192 (4.71), 210 (4.43), 234 (4.87), 316 (4.54),
346 nm (4.28); MS (70 eV): m/z (%): 404 (100) [M+], 387 (14), 215 (10),
202 (52); elemental analysis calcd (%) for C 32H20: C 95.02, H 4.98;
found: C 94.57, H 4.97.
A
N
a) 9,10-Bis-(3-bromo-1-propynyl)anthracene (53): According to GP 2
9,10-diiodoanthracene (2.3 g, 5.35 mmol)was coupled with 29 (1.65 g,
11.8 mmol)in the presence of [Pd (PPh3)4] (0.247 g, 0.21 mmol)and cupr-
E
ous iodide (0.1 g, 0.53 mmol)in triethylamine (100 mL)for 8 h at 80 8C.
After work-up (see above)the bis-THP ether of 9,10-bis-(3-hydroxy-1-
propynyl)anthracene (1.90 g, 78%) was obtained as yellow-orange
prisms. M.p. 1138C; 1H NMR (400 MHz, CDCl3): d=1.50–1.97 (m, 12H,
THP-ring), 3.52–3.66 (m, 2H, THP-ring), 3.96–4.02 (m, 2H, THP-ring),
4.83 (s, 4H, propargyl-CH2-), 5.10 (t, J=3.3 Hz, 2H, -CH(O)2), 7.57–7.60
and 8.54–8.58 ppm (AA’BB’-m, 8H, arom. H); 13C NMR (100 MHz,
CDCl3): d=19.13 (t), 25.39 (t), 30.40 (t), 55.18 (t), 62.20 (t), 82.35 (s),
97.09 (d), 98.06 (s), 118.04 (s), 126.71 (d), 127.06 (d), 132.19 ppm (s); IR
(KBr): n˜ =3058 (w), 2940 (w), 2202 (vw), 1436 (s), 1389 (s), 1208 (s),
1119 (vs), 1079 (vs), 1039 (vs), 768 cmꢀ1 (vs); UV (acetonitrile): lmax (log
e)=192 (4.23), 218 (3.80), 268 (4.86), 366 (3.39), 384 (3.79), 406 (4.13),
430 nm (4.24); MS (70 eV): m/z (%): 454 (36) [M+], 354 (24), 252 (100),
239 (51), 85 (10); elemental analysis calcd (%) for C30H30O4: C 79.27, H
6.65; found: C 78.94, H 6.71.
b) Debromination of 47 to 49: According to GP 3 47 (1.0 g, 3.2 mmol)
was debrominated with cesium fluoride (0.34 g, 3.5 mmol)and 14 (1.3 g,
3.5 mmol)in anhydrous DMF (50 mL). The reaction mixture was stirred
for 6 h at 08C, followed by 12 h at room temperature. After work-up (see
above)the solvent was removed by rotary evaporation, and the residue
purified by column chromatography (alumina, pentane)and recrystalliza-
tion (methanol): 49 (40 mg, 7.5%)as colorless needles. M.p. 190 8C
(decomp); 1H NMR (400 MHz, CDCl3): d=2.69 (s, 8H, -CH2CH2-),
6.92 ppm (s, 8H, arom. H); 13C NMR (100 MHz, CDCl3): d=19.32 (t),
85.58 (s), 91.96 (s), 123.00 (s), 130.72 ppm (d); IR (KBr): n˜ =3034 (vw),
2909 (w), 2835 (w), 2217 (w), 1503 (s), 834 cmꢀ1 (vs); UV (hexane): lmax
(log e)=194 (4.56), 212 (4.45), 264 (4.76), 286 nm (4.30); MS (70 eV):
m/z (%): 304 (100) [M+], 276 (16), 152 (62); HRMS: m/z: calcd for
C24H16: 304.1252; found: 304.125. When the experiment was repeated in
acetonitrile the yield increased to 245 mg (46%). Although several at-
tempts were undertaken, we could not obtain a satisfactory elemental
analysis of 49.
According to GP 1 this bis-ether (1.40 g, 3.08 mmol)was treated with tri-
phenylphosphine (1.94 g, 7.39 mmol)and bromine (1.18 g, 7.39 mmol)in
dichloromethane (50 mL). After work-up (see GP 1) 53 (1.13 g, 96%)
was obtained as yellow-orange prisms (dichloromethane). M.p. 1728C;
1H NMR (400 MHz, CDCl3): d=4.50 (s, 4H, -CH2-), 7.60–8.54 ppm
(AA’BB’-m, 8H, arom. H); 13C NMR (100 MHz, CDCl3): d=15.32 (t),
83.65 (s), 96.95 (s), 117.69 (s), 126.89 (d), 127.13 (d), 132.11 ppm (s); IR
(KBr): n˜ =3060 (vw), 2207 (s), 1436 (m), 1203 (s), 1192 (s), 761 cmꢀ1 (vs);
UV (acetonitrile): lmax (log e)=192 (4.60), 268 (4.92), 390 (3.96), 410
(4.22), 434 nm (4.34); MS (70 eV): m/z (%): 414 (7) [M+], 412 (14)[ M+],
410 (6)[ M+], 333 (54), 331 (54), 252 (98), 250 (100); elemental analysis
calcd (%)for C 20H12Br2: C 58.29, H 2.93; found: C 58.31, H 2.96.
syn-[6.6](1,4)Naphthalenocyclophan-1,5,18,22-tetrayne (52)
R
a) 1,4-Bis-(3-bromo-1-propynyl)naphthalene (50): According to GP 2 1,4-
dibromonaphthalene (3.0 g, 10.5 mmol)was coupled with THP-ether 29
(3.68 g, 26.3 mmol)in the presence of [Pd (PPh3)4] (0.363 g, 0.315 mmol)
N
and cuprous iodide (0.120 g, 0.63 mmol)in triethylamine (100 mL); reac-
tion time 4 h at 808C. After work-up (see above, GP 2), 3.8 g (90%) of
the bis-THP ether of 1,4-bis(3-hydroxy-1-propynyl)naphthalene was ob-
tained, colorless solid. M.p. 758C; 1H NMR (400 MHz, CDCl3): d=1.56–
1.92 (m, 12H, THP-ring), 3.57–3.63 (m, 2H, THP-ring), 3.91 (m, 2H,
THP-ring), 4.62 and 4.67 (AX-q, J=15.9 Hz, 4H, propargyl-CH2-), 4.98
(t, J=3.3 Hz, 2H, -CH(O)2), 7.50–7.60 and 8.32–8.36 (AA’BB’-m, 4H,
arom. H), 7.61 ppm (s, 2H, arom. H); 13C NMR (100 MHz, CDCl3): d=
19.04 (t), 25.34 (t), 30.29 (t), 54.66 (t), 62.08 (t), 83.59 (s), 91.63 (s), 96.12
(s), 121.12 (s), 126.47 (d), 127.14 (d), 129.87 (d), 133.06 ppm (s); IR
(KBr): n˜ =3065 (vw), 2945 (w), 2226 (vw), 1447 (w), 1202 (m), 1026 cmꢀ1
(s); UV (hexane): lmax (log e)=192 (4.56), 212 (4.17), 242 (4.68), 324
(4.40), 340 nm (4.44); MS (70 eV): m/z (%): 404 (16) [M+], 304 (43), 262
(20), 204 (51), 203 (98), 202 (100), 85 (14); elemental analysis calcd (%)
for C26H28O4: C 77.20, H 6.98; found: C 76.82, H. 7.01. According to
GP 1 this bis-ether (2.4 g, 5.94 mmol)was treated with triphenylphos-
phine (3.74 g, 14.3 mmol)and bromine (0.73 g, 14.3 mmol)in dichlorome-
thane (100 mL). After work-up 50 (2.06 g, 95%)was obtained as color-
b) Debromination of 53 to 55: According to GP 3 53 (0.8 g, 1.94 mmol)
was treated with 14 (1.06 g, 2.91 mmol)and cesium fluoride (0.44 g,
2.91 mmol)in DMF (70 mL.) After work-up (see above) 55 (24 mg, ca.
5%)was obtained as yellow needles. As soon as the solvent had been re-
moved completely, the hydrocarbon started to decompose (transforma-
tion first into brown, then black material). This instability prevented the
recording of a mass spectrum and determination of an elemental analysis.
1H NMR (400 MHz, CDCl3): d=3.18 (s, 8H, -CH2CH2-), 7.96–8.00 ppm
(AA’BB’-m, 16H, arom. H); 13C NMR (100 MHz, CDCl3): d=20.53 (t),
84.07 (s), 101.05 (s), 117.88 (s), 124.95 (d), 126.37 (d), 130.75 ppm (s); IR
(KBr): n˜ =2923 (w), 1622 (s), 760 cmꢀ1 (s); UV (acetonitrile, qualitative):
lmax =192, 256, 372, 388, 404, 428, 442 nm.
A
N
1
less needles (cyclohexane). M.p. 1058C; H NMR (400 MHz, CDCl3): d=
AHCTREUNG
4.32 (s, 4H, -CH2-), 7.61 (s, 2H, arom. H), 7.61–8.33 ppm (AA’BB’-m,
4H, arom. H); 13C NMR (100 MHz, CDCl3): d=15.03 (t), 84.54 (s), 90.72
(s), 120.93 (s), 126.31 (d), 127.51 (d), 129.95 (d), 133.04 ppm (s); IR
(KBr): n˜ =3050 (vw), 2212 (w), 1565 (w), 1369 (m), 1198 (s), 761 (s), 605
(s); UV (acetonitrile): lmax (log e)=192 (4.35), 242 (4.38), 330 (4.19),
344 nm (4.19); MS (70 eV): m/z (%): 364 (14) [M+], 362 (28)[ M+], 360
(15)[ M+], 283 (86), 281 (85), 202 (100); elemental analysis calcd (%) for
C16H10Br2: C 53.08, H 2.78; found: C 53.23, H 2.72.
ous iodide (0.134 g, 0.70 mmol)in triethylamine (100 mL)for 7 h at
808C. After work-up (see GP 2)the bis-THP ether of 2,5-bis-(3-hydroxy-
1-propynyl)furan (9.8 g, 80%) was isolated as a colorless oil, which solidi-
fied around 08C. 1H NMR (400 MHz, CDCl3): d=1.43–1.81 (m, 12H,
THP-ring), 3.45–3.50 (m, 2H, THP-ring), 3.75–3.81 (m, 2H, THP-ring),
4.38–4.43 (AB-q, J=16.2 Hz, 4H, propargyl-CH2-), 4.78 (t, J=3.3 Hz,
2H, -CH(O)2), 6.47 ppm (s, 2H, -CH=); 13C NMR (100 MHz, CDCl3):
d=18.86 (t), 25.23 (t), 30.08 (t), 54.30 (t), 61.64 (t), 75.55 (s), 90.36 (s),
96.78 (d), 116.32 (d), 136.93 ppm (s); IR (film): n˜ =3119 (w), 2943 (s),
2870 (m), 2852 (m), 1515 (m), 1389 (s), 1121 (vs), 1058 (s), 1028 (vs),
901 cmꢀ1 (s); UV (acetonitrile): lmax (log e)=204 (4.02), 280 (4.45), 284
(4.45), 296 nm (4.42); MS (70 eV): m/z (%): 344 (40) [M+], 243 (100),
b) Debromination of 50 to 52: According to GP 3 50 (0.82 g, 2.25 mmol)
was treated with 14 (2.45 g, 6.75 mmol)and cesium fluoride (2.04 g,
13.5 mmol)in acetonitrile (100 mL.) After work-up (see above)
52
(230 mg, 51%)was isolated as colorless prisms (dichloromethane,)
Chem. Eur. J. 2007, 13, 9462 – 9477
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9473

H. Hopf et al.
144 (40), 115 (60), 85 (39); elemental analysis calcd (%) for C20H24O5: C
69.75, H 7.02; found: C 69.55, H 7.06.
analysis calcd (%)for C 20H12S2: C 75.91, H 3.82, S 20.26; found: C 75.48,
H 3.73, S 19.83.
Cross-dimerization
A sample of the bis-protected ether (1.60 g, 4.65 mmol), was treated ac-
cording to GP 1 with triphenylphosphine (2.92 g, 11.2 mmol)and bro-
mine (1.79 g, 11.2 mmol)in dichloromethane (100 mL.) After work-up
(see GP 2 above)the dibromide 57a (1.22 g, 97%)was obtained as color-
less needles (dichloromethane). M.p. 79–828C; 1H NMR (400 MHz,
CDCl3): d=4.15 (s, 4H, -CH2-), 6.60 ppm (s, 2H, =CH-); 13C NMR
(100 MHz, CDCl3): d=14.11 (t), 76.17 (s), 98.49 (s), 117.22 (d),
136.95 ppm (s); IR (KBr): n˜ =3154 (s), 3125 (s), 3002 (s), 2954 (s), 2226
(m), 1516 (s), 1200 (s), 1010 (vs), 801 cmꢀ1 (vs); UV (acetonitrile): lmax
(log e)=192 (4.13), 300 nm (4.45); MS (70 eV): m/z (%): 304 (12) [M+],
302 (22)[ M+], 300 (12)[ M+], 223 (98), 221 (100), 142 (64); elemental
analysis calcd (%)for C 10H6Br2O: C 39.78, H 2.00; found: C 39.94, H
1.92.
A
N
cording to GP 3 a mixture of 50 (0.569 g, 1.57 mmol)and 57b (0.550 g,
1.57 mmol)was treated with 14 (3.42 g, 4.71 mmol)and cesium fluoride
(1.42 g, 9.42 mmol)in acetonitrile (100 mL.) Yield: 110 mg of a mixture
of 52 (9.5%), 59b (2.7%), and 60 (10%), the ratio being determined by
1H NMR analysis. The mixed dimer 60 is an unstable compound that de-
composed during column chromatography on silica gel. Its NMR spectra
were determined in the above mixture, subtracting the signals for the
known cyclodimers 52 and 59b.
Compound 60: 1H NMR (400 MHz, CDCl3): d=2.76–2.79 (m, 8H, -CH2
CH2-), 6.56 (s, 2H, thiophene ring), 7.51–8.33 (AA’BB’-m, 4H, unsubst.
naphthalene ring), 7.57 ppm (s, 2H, subst. naphthalene ring); 13C NMR
(100 MHz, CDCl3): d=19.28 (t), 20.16 (t), 76.30 (s), 84.32 (s), 93.14 (s),
97.01 (s), 122.14 (s), 124.93 (s), 126.84 (d), 126.76 (d), 128.09 (d), 129.66
(d), 134.13 ppm (s).
b) Debromination of 57a to 59a: According to GP 3 57a (1.00 g,
3.31 mmol)was treated with 14 (1.80 g, 4.96 mmol)and cesium fluoride
(0.754 g, 4.96 mmol)in DMF (50 mL.) After work-up (see above) 59a
(122 mg, 26%)was obtained as colorless plates (dichloromethane/metha-
nol). M.p. 1008C (decomp); 1H NMR (400 MHz, CDCl3): d=2.71 (s, 8H,
-CH2CH2-), 6.39 ppm (s, 4H, -CH=); 13C NMR (100 MHz, CDCl3): d=
19.19 (t), 73.52 (s), 92.43 (s), 113.43 (s), 137.77 ppm (d); IR (KBr): n˜ =
3127 (w), 3114 (w), 2953 (s), 2915 (s), 2850 (m), 2227 (w), 2172 (w), 1702
(m), 1520 (s), 1418 (s), 1308 (s), 1192 (s), 1005 (vs), 787 cmꢀ1 (vs); UV
(acetonitrile): lmax (log e)=206 (4.26), 264 (4.51), 272 (4.67), 286 (4.25),
298 nm (4.18); MS (70 eV): m/z (%): 284 (100) [M+], 226 (38), 114 (14);
HRMS: calcd for C20H12O2: 284.083, found 284.083.
Attempted preparation of [10.10]paracyclophan-1,3,7,9,17,19,23,25-oc-
tayne (65)
a) 1,4-Bis-(5-bromo-1,3-pentadiynyl)benzene (64): To methanol (150 mL)
and aqueous ethylamine solution (70%, 50 mL)was added 1,4-bis(trime-
thylsilylethynyl)benzene (61, 4.00 g, 14.8 mmol), and the mixture was
stirred for 30 min at room temperature. Subsequently hydroxylamine hy-
drochloride (200 g)and cuprous chloride (0.3 g)were added, followed by
the addition of 1-bromopropargyl THP ether 62 (7.1 g, 32.6 mmol). After
stirring for 1 h at room temperature, the reaction temperature was raised
to 558C, and the mixture stirred for an additional hour. For work-up the
cooled solution was poured into saturated aqueous ammonium chloride
solution (400 mL), and the coupling product 63 isolated by careful extrac-
tion with Et2O. The combined organic phases were filtered through a pad
of silica gel, the solvent was removed by rotary evaporation and the re-
maining solid purified by column chromatography on silica gel with di-
chloromethane to yield 1,4-bis-(5-tetrahydropyran-2-yloxy-1,3-pentadiy-
nyl)benzene (63, 3.86 g, 65%)as colorless needles. M.p. 88 8C; 1H NMR
(400 MHz, CDCl3): d=1.51–188 (m, 12H, THP-ring), 3.53–3.58 (m, 2H,
THP-ring), 3.81–3.97 (m, 2H, THP-ring), 4.41 (ps-s, 4H, propargyl-CH2-),
4.48 (ps-t, J=3.3 Hz, 2H, -CH(O)2), 7.42 ppm (s, 4H, arom. H);
13C NMR (100 MHz, CDCl3): d=18.89 (t), 25.24 (t), 30.11 (t), 54.56 (t),
61.99 (t), 70.16 (s), 75.90 (s), 77.00 (s), 80.26 (s), 96.96 (d), 122.30 (s),
132.44 ppm (d); IR (KBr): n˜ =2943 (m), 2240 (w), 1344 (m), 1149 (s),
1022 (s), 872 (s), 816 cmꢀ1 (s); UV (acetonitrile): lmax (log e)=196 (4.73),
228 (4.74), 292 (4.50), 306 (4.76), 328 nm (4.90); MS (70 eV): m/z (%):
402 (35)[ M+], 302 (100), 234 (28), 218 (64), 202 (95), 85 (45); elemental
analysis calcd (%)for C 26H26O4: C 77.59, H 6.51; found: C 77.58, H 6.53.
A
N
a) 2,5-Bis-(3-bromo-1-propynyl)thiophene (57b): According to GP 2 2,5-
dibromothiophene (56b, 5.00 g, 20.7 mmol)was coupled with 29 (7.23 g,
88.4 mmol)in the presence of [Pd (PPh3)4] (0.48 g, 0.41 mmol)and cupr-
T
ous iodide (0.078 g, 0.41 mmol)in triethylamine (80 mL)for 7 h at 60 8C.
After work-up (see above)the bis-THP ether of 2,5-bis-(3-hydroxy-1-pro-
pynyl)thiophene (5.75 g, 77%) was isolated as a colorless solid. M.p.
508C (cyclohexane); 1H NMR (400 MHz, CDCl3): d=1.51–1.90 (m, 12H,
THP-ring), 3.53–3.58 (m, 2H, THP-ring), 3.83–3.89 (m, 2H, THP-ring),
4.44–4.51 (AB-q, J=15.9 Hz, 4H, propargyl-CH2-), 4.85 (t, J=3.3 Hz,
2H, -CH(O)2), 7.05 ppm (s, 2H, -CH=); 13C NMR (100 MHz, CDCl3):
d=18.09 (t), 25.27 (t), 30.14 (t), 54.67 (t), 61.89 (t), 78.44 (s), 90.08 (s),
96.90 (d), 123.98 (s), 132.05 ppm (d); IR (film): n˜ =2942 (s), 2870 (m),
2851 (m), 2222 (w), 1343 (m), 1201 (s), 1120 (vs), 1056 (vs), 1026 (vs),
902 cmꢀ1 (s); UV (acetonitrile): lmax (log e)=208 (3.97), 216 (4.02), 300
(4.41), 304 nm (4.41); MS (70 eV): m/z (%): 360 (14) [M+], 260 (60), 259
(40), 159 (100), 85 (66); elemental analysis calcd (%) for C20H24O4S: C
66.64, H 6.71, S 8.89; found: C 66.48, H 6.81, S (8.88).
b) 1,4-Bis-(5-bromo-1,3-pentadiynyl)benzene (64): According to GP 1 63
(1.00 g, 2.49 mmol)was treated with triphenylphosphine (1.56 g,
5.97 mmol)and bromine (0.96 g, 5.97 mmol)in dichloromethane
(70 mL). After work-up (see above) 64 (0.86 g, 96%)was obtained as
slightly yellow needles (dichloromethane). M.p. 1388C; 1H NMR
(400 MHz, CDCl3): d=4.06 (s, -CH2-), 7.50 ppm (s, 4H, arom. H);
13C NMR (100 MHz, CDCl3): d=14.23 (t), 70.93 (s), 75.68 (s), 78.30 (s),
78.81 (s), 122.21 (s), 132.23 ppm (d); IR (KBr): n˜ =2984 (w), 2240 (w),
2217 (w), 1403 (m), 1195 (s), 830 cmꢀ1 (s); UV (acetonitrile): lmax (log
e)=200 (4.70), 238 (4.26), 314 (4.72), 334 nm (4.75); MS (70 eV): m/z
(%): 362 (10) [M+], 360 (24)[ M+], 358 (11)[ M+], 281 (60), 279 (60),
200 (100), 100 (38); elemental analysis calcd (%) for C16H8Br2: C 53.38,
H 2.24; found: 53.36, H 2.29.
A sample of the bis-protected ether (2.50 g, 6.94 mmol), was treated ac-
cording to GP 1 with triphenylphosphine (4.36 g, 16.6 mmol)and bro-
mine (2.66 g, 16.7 mmol)in dichloromethane (100 mL.) After work-up
(see above)the dibromide 57b (2.07 g, 95%)was obtained as colorless
needles (dichloromethane/pentane). M.p. 628C; 1H NMR (400 MHz,
CDCl3): d=4.16 (s, 4H, -CH2-), 7.08 ppm (s, 2H, -CH=); 13C NMR
(100 MHz, CDCl3): d=14.84 (t), 79.25 (s), 89.34 (s), 124.01 (s),
132.73 ppm (d); IR (KBr): n˜ =3004 (w), 2994 (w), 2223 (s), 1198 (vs),
809 cmꢀ1 (s); UV (acetonitrile): lmax (log e)=192 (4.28), 316 nm (4.45);
MS (70 eV): m/z (%): 320 (10) [M+], 318 (20)[ M+], 316 (9)[ M+], 239
(100), 237 (98), 158 (92); elemental analysis calcd (%) for C10H6SBr2: C
37.77, H 1.90, S 10.08; found: C 37.42, H 1.90, S 10.29.
b) Debromination of 57b to 59b: According to GP 3 57b (1.00 g,
3.15 mmol)was treated with 14 (1.72 g, 4.73 mmol)and cesium fluoride
(0.714 g, 4.73 mmol)in DMF (50 mL.) After work-up (see above) 59b
(150 mg, 30%)was isolated as colorless needles (dichloromethane/meth-
anol). M.p. 1208C (decomp); 1H NMR (400 MHz, CDCl3): d=2.70 (s,
8H, -CH2-), 6.89 ppm (s, 4H, -CH=); 13C NMR (100 MHz, CDCl3): d=
19.89 (t), 77.21 (s), 95.32 (s), 125.25 (s), 129.01 ppm (d); IR (KBr): n˜ =
2929 (w), 2210 (w), 1450 (m), 1188 (m), 1045 (m), 933 (m), 817 (s),
809 cmꢀ1 (s); UV (acetonitrile): lmax (log e)=210 (4.32), 218 (4.40),
296 nm (4.55); MS (70 eV): m/z (%): 316 (100) [M+], 158 (33); elemental
c) Attempted debromination of 64: According to GP 3 several attempts
were undertaken to debrominate 64 to the cyclophane 65. Although a
spot was detected on the TLC plate having a Rf value in agreement with
the expected hydrocarbon, in no case could this material be enriched or
even purified. In all cases it was observed that this spot turned brown,
and later black quickly.
A
a) 4,4’-Bis-(3-tetrahydropyran-2-yloxy-1-propynyl)biphenyl (67): Accord-
ing to GP 2 4,4’-dibromobiphenyl (66, 5.0 g, 16.0 mmol)was coupled with
9474
www.chemeurj.org
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 9462 – 9477

1,x-Elimination Reactions
FULL PAPER
29 (5.61 g, 40.0 mmol)in the presence of [Pd
and cuprous iodide (0.122 g, 0.64 mmol)in triethylamine (200 mL;) 67
(6.5 g, 95%)as colorless needles (dichloromethane. ) M.p. 112 8C;
(PPh3)4] (0.370 g, 0.32 mmol)
(acetonitrile): lmax (log e)=206 (4.60), 308 (4.61), 332 nm (4.79); MS
(70 eV): m/z (%): 402 (8) [M+], 400 (20)[ M+], 398 (10)[ M+], 312 (64),
319 (63), 240 (100); elemental analysis calcd (%) for C19H12Br2: C 57.04,
H 3.02; found: C 57.18, H 3.03.
1H NMR (400 MHz, CDCl3): d=1.52–1.92 (m, 12H, THP-ring), 3.55–3.60
(m, 2H, THP-ring), 3.87–3.93 (m, 2H, THP-ring), 4.47–4.54 (AB-q, J=
15.7 Hz, 4H, propargyl-CH2-), 4.91 (t, J=3.3 Hz, 2H, -CH(O)2), 7.49–
7.54 ppm (AA’BB’-m, 8H, arom. H); 13C NMR (100 MHz, CDCl3): d=
19.00 (t), 25.33 (t), 30.24 (t), 54.75 (t), 61.96 (t), 85.50 (s), 86.06 (s), 96.85
(d), 122.00 (s), 126.72 (d), 132.26 (d), 140.10 ppm (s); IR (KBr): n˜ =3072
(w), 2943 (s), 2924 (s), 2869 (s), 2223 (vw), 1495 (s), 1117 (s), 1024 cmꢀ1
(vs); UV (acetonitrile): lmax (log e)=204 (4.65), 216 (sh, 4.38), 296 nm
(4.70); MS (70 eV): m/z (%): 430 (18) [M+], 346 (10), 329 (38), 246 (45),
230 (100), 85 (22); elemental analysis calcd (%) for C28H30O4: C 78.11, H
7.02; found: C 77.96, H 7.04.
b) Debromination of 70 to 71: According to GP 3 70 (1.00 g, 2.50 mmol)
was treated with 14 (1.36 g, 3.75 mmol)and cesium fluoride (0.566 g,
3.75 mmol)in DMF (100 mL.) After work-up (see above)
71 (15 mg,
2.5%)was obtained as colorless platelets (dichloromethane). M.p. 140 8C
(decomp); 1H NMR (400 MHz, CDCl3): d=2.74 (s, 4H, fluorene-CH2),
2.75 (s, 8H, -CH2CH2-), 6.99 (s, 4H, arom. H), 7.40 (d, Jo =8.0 Hz, 4H,
arom. H), 7.66 ppm (d, Jo =8.0 Hz, 4H, arom. H); IR (KBr): n˜ =3053
(w), 2927 (w), 2908 (w), 2223 (w), 1467 (s), 821 cmꢀ1 (s); UV, qual. (ace-
tonitrile): lmax =194, 202, 296, 302, 318, 330 nm; MS (70 eV): m/z (%):
480 (100)[ M+], 240 (52); HRMS: m/z: calcd for C38H24: 480.1879;
found: 480.187.
b) 4,4’-Bis-(3-bromo-1-propynyl)biphenyl (68): According to GP 1 67
(4.00 g, 9.3 mmol)was treated with triphenylphosphine (5.84 g,
22.3 mmol)and bromine (3.57 g, 22.3 mmol)in dichloromethane
(200 mL). After work-up (see above) 68 (3.35 g, 93%)was obtained as
colorless needles (cyclohexane). M.p. 1158C; 1H NMR (400 MHz,
CDCl3): d=4.19 (s, 4H, -CH2-), 7.50–7.56 ppm (AA’BB’-m, 8H, arom.
H); 13C NMR (100 MHz, CDCl3): d=15.22 (t), 85.15 (s), 86.38 (s), 121.48
(s), 126.85 (d), 132.35 (d), 140.46 ppm (s); IR (KBr): n˜ =3040 (vw), 2222
(w), 1495 (m), 1204 (s), 824 cmꢀ1 (vs); UV (acetonitrile): lmax (log e)=
202 (4.70), 220 (sh, 4.38), 304 nm (4.75); MS (70 eV): m/z (%): 390 (12)
[M+], 388 (21)[ M+], 386 (10)[ M+], 309 (62), 307 (63), 228 (100); ele-
mental analysis calcd (%)for C 18H12Br2: C 55.71, H 3.12; found: C 55.69,
H. 3.08.
A
N
a) 2,5-Bis-(5-tetrahydropyran-2-yloxy-1,3-penadiynyl) thiophene (73): As
described for the preparation of 63 above, the bis-ether 73 was prepared
from 2,5-bis-(trimethylsilylethynyl)thiophene (72, 5.5 g, 20.0 mmol; pre-
pared according to ref. [29])and 62 (9.64 g, 44.0 mmol)using methanol
(150 mL), aqueous ethylamine solution (70%, 50 mL), hydroxylamine
hydrochloride (2.0 g)and cuprous chloride (0.3 g.) After work-up (see
above) 73 (4.2 g, 52%)was obtained as a yellow, glassy solid. M.p. 37 8C;
1H NMR (400 MHz, CDCl3): d=1.48–1.86 (m, 12H, THP-ring), 3.50–3.56
(m, 2H, THP-ring), 3.78–3.84 (m, 2H, THP-ring), 4.39 (s, 4H, propargyl-
CH2), 4.80 (t, J=3.3 Hz, 2H, -CH(O)2), 7.12 ppm (s, 2H, -CH=);
13C NMR (100 MHz, CDCl3): d=18.87 (t), 25.23 (t), 30.10 (t), 54.53 (t),
61.97 (t), 69.95 (s), 69.97 (s), 78.79 (s), 82.20 (s), 96.95 (d), 124.19 (s),
134.06 ppm (d); IR (KBr): n˜ =2942 (m), 2870 (w), 2229 (w), 1344 (m),
1202 (m), 1121 (s), 1045 cmꢀ1 (s); UV (acetonitrile): lmax (log e)=196
(4.77), 226 (4.27), 236 (4.54), 248 (4.15), 260 (4.01), 344 (4.56), 362 nm
(4.66); MS (70 eV): m/z (%): 408 (30) [M+], 308 (100), 307 (44), 207
(56), 163 (45), 85 (44); elemental analysis calcd (%) for C24H24O4S: C
70.56, H 5.92; found: C 70.26, H 5.99.
c) Debromination of 68 to 69: According to GP 3 68 (0.530 g, 1.36 mmol)
was treated with 14 (0.741 g, 2.04 mmol)and cesium fluoride (0.308 g,
2.04 mmol)in DMF (100 mL.) After work-up (see above) 69 (13.8 mg,
5%)was obtained as colorless platelets (dichloromethane.) M.p. 150 8C
(decomp); 1H NMR (400 MHz, CDCl3): d=2.75 (s, 8H, -CH2CH2-),
7.05–7.17 ppm (m, 16, arom. H); 13C NMR (100 MHz, CDCl3): d=19.39
(t), 84.89 (s), 91.09 (s), 122.83 (s), 126.19 (s), 131.79 (d), 139.30 ppm (s);
IR (KBr): n˜ =2922 (m), 2215 (vw), 1491 (m), 820 cmꢀ1 (s); UV, qual.
(acetonitrile): lmax =200, 288 nm; MS (70 eV): m/z (%): 456 (100) [M+],
228 (74); HRMS: m/z: calcd for C32H24: 456.187; found: 456.187.
b) 2,5-bis-(5-bromo-1,3-pentadiynyl)thiophene (74): According to GP 1
73 (1.00 g, 2.45 mmol)was treated with triphenylphosphine (1.54 g,
5.88 mmol)and bromine (0.94 g, 5.88 mmol)in dichloromethane
(100 mL). After work-up (see above) 74 (0.85 g, 95%)was isolated as
yellow, thin needles (cyclohexane). M.p. 958C; 1H NMR (400 MHz,
CDCl3): d=4.06 (s, 4H, -CH2-), 7.15 ppm (s, 2H, -CH=); 13C NMR
(100 MHz, CDCl3): d=14.11 (t), 70.23 (s), 71.77 (s), 78.61 (s), 80.18 (s),
124.22 (s), 134.47 ppm (d); IR (KBr): n˜ =3098 (w), 2949 (w), 2225 (m),
1193 (s), 799 cmꢀ1 (s); UV (acetonitrile): lmax (log e)=194 (4.71), 242
(4.44), 346 (4.60), 368 nm (4.58); MS (70 eV): m/z (%): 368 (15) [M+],
366 (28)[ M+], 364 (16)[ M+], 287 (81), 285 (79), 206 (100), 161 (26), 103
(25); elemental analysis calcd (%) for C 14H6Br2S: C 45.93, H 1.65, S 8.76;
found: C 45.72, H 1.69, S 8.39.
A
N
a) 2,7-Bis-(3-bromo-1-propynyl)-9H-fluorene (70): According to GP 2
2,7-dibromofluorene (5.0 g, 15.4 mmol)was coupled with 29 (5.40 g,
38.6 mmol)in the presence of [Pd (PPh3)4] (0.36 g, 0.31 mmol)and cupr-
R
ous iodide (0.116 g, 0.31 mmol)in triethylamine (200 mL)for 7 h at
808C. After work-up (see above)the bis-THP ether of 2,7-bis-(3-hy-
droxy-1-propynyl)fluorene (6.6 g, 97%) was isolated as colorless needles
(dichloromethane). M.p. 948C; 1H NMR (400 MHz, CDCl3): d=1.42–
1.92 (m, 12H, THP-ring), 3.55–3.60 (m, 2H, THP-ring), 3.83 (s, 2H, fluo-
rene-CH2), 3.87–3.93 (m, 2H, THP-ring), 4.48–4.54 (AB-q, J=15.7 Hz,
4H, propargyl-CH2), 4.92 (t, J=3.3 Hz, 2H, -CH(O)2), 7.46 (d, Jo =
7.9 Hz, 2H, arom. H), 7.60 (s, 2H, arom. H), 7.66 ppm (d, Jo =7.9 Hz,
2H, arom. H); 13C NMR (100 MHz, CDCl3): d=19.02 (t), 25.35 (t), 30.26
(t), 36.42 (t), 54.80 (t), 61.96 (t), 85.36 (s), 86.28 (s), 96.81 (d), 119.90 (d),
121.19 (s), 128.35 (d), 130.79 (d), 141.18 (s), 143.33 ppm (s); IR (KBr):
n˜ =3066 (w), 2938 (s), 2924 (s), 2870 (m), 2226 (w), 1468 (s), 1131 (s),
1117 (s), 1033 (s), 1025 cmꢀ1 (s); UV (acetonitrile): lmax (log e)=210
(4.63), 294 (4.56), 304 (4.68), 312 (4.63), 320 (4.65), 324 nm (4.88); MS
(70 eV): m/z (%): 442 (30) [M+], 358 (13), 341 (39), 258 (63), 242 (100),
203 (48), 85 (21); elemental analysis calcd (%) for C29H30O4: C 78.71, H
6.83; found: C 78.81, H 6.82.
c) Debromination of 74 to 75: According to GP 3 74 (0.78 g, 2.13 mmol)
was treated with 14 (2.32 g, 6.39 mmol)and cesium fluoride (1.93 g,
12.78 mmol)in acetonitrile (50 mL.) After work-up (see above)
75
(80 mg, 18%)was isolated, as an unstable yellow solid. 1H NMR
(400 MHz, CDCl3): d=2.65 (s, 8H, -CH2CH2-), 7.04 ppm (s, 4H, -CH=);
13C NMR (100 MHz, CDCl3): d=16.59 (t), 68.14 (s), 68.70 (s), 79.86 (s),
85.41 (s), 125.22 (s), 131.88 ppm (s).
Bis-(4-(3-bromo-1-propynyl)-phenyl)acetylene (76)
a) Bis-(4-bromophenyl)acetylene: A mixture of 1-bromo-4-ethynylben-
zene (2.0 g, 11.0 mmol), 1-bromo-4-iodobenzene (3.13 g, 11.0 mmol), and
[Pd(PPh3)4] (0.254 g, 0.22 mmol)was stirred under nitrogen in propyla-
A
The bis-ether (1.99 g, 4.5 mmol)was treated according to GP 1 with tri-
phenylphosphine (2.83 g, 10.8 mmol)and bromine (1.73 g, 10.8 mmol)in
dichloromethane (10 mL). After work-up (see above) the dibromide 70
(1.68 g, 93%)was isolated as colorless needles (dichloromethane.) M.p.
1718C; 1H NMR (400 MHz, CDCl3): d=3.84 (s, 2H, fluorene-CH2), 4.24
(s, 4H, propargyl-CH2), 7.45 (dd, Jo =7.9, Jm =0.4 Hz, 2H, arom. H), 7.61
(d, Jm =0.4 Hz, 2H, arom. H), 7.68 ppm (d, Jo =7.9 Hz, 2H, arom. H);
13C NMR (100 MHz, CDCl3): d=15.54 (t), 36.50 (t), 84.61 (s), 87.32 (s),
120.16 (d), 120.75 (s), 128.51 (d), 130.98 (d), 141.59 (s), 143.50 (s) ppm;
IR (KBr): n˜ =3002 (w), 2216 (m), 1468 (s), 1202 (s), 813 cmꢀ1 (s); UV
mine and pyridine (1:1, 50 mL)for 24 h at room temperature. For hydrol-
ysis saturated aqueous ammonium chloride solution was added (300 mL),
and the reaction mixture thoroughly extracted with dichloromethane.
The combined extracts were filtered through a pad of silica gel, the sol-
vent was removed in vacuo, and the remaining solid purified by column
chromatography on silica gel with pentane to yield the dibromide (2.83 g,
77%)as colorless plates (dichloromethane.) M.p. 176
8C; 1H NMR
(400 MHz, CDCl3): d=7.36–7.50 ppm (AA’BB’-m, arom. H); 13C NMR
(100 MHz, CDCl3): d=89.41 (s), 121.88 (s), 122.78 (s), 131.69 (d),
Chem. Eur. J. 2007, 13, 9462 – 9477
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9475

H. Hopf et al.
132.99 ppm (d); MS (70 eV): m/z (%): 338 (52) [M+], 336 (100)[ M+],
334 (54)[ M+], 176 (59).
lmax (log e)=196 (4.74), 280 (4.763), 294 (4.98), 330 nm (4.53); MS
(70 eV): m/z (%): 554 (7) [M+], 470 (20), 452 (15), 386 (38), 368 (36),
352 (42), 339 (77), 326 (50), 176 (35), 85 (100); elemental analysis calcd
(%)for C 38H34O4: 82.28, H 6.18; found: C 82.26, H 6.22.
b) Bis-(4-(3-tetrahydro-2H-2-pyranyloxy-1-propynyl)acetylene: Accord-
ing to GP 2 the above dibromide (2.0 g, 5.95 mmol)was coupled with 29
(1.84 g, 13.11 mmol)in the presence of [Pd
A
c) 8,10-Bis-(4-(3-bromo-1-propynyl)phenyl-ortho-diethynylbenzene (77):
According to GP 1 the bis-THP-ether (1.40 g, 2.53 mmol), prepared as
above, was treated with triphenylphosphine (1.59 g, 6.07 mmol)and bro-
mine (0.97 g, 6.07 mmol)in dichloromethane (50 mL.) After work-up
(see GP 1) 77 (1.1 g, 85%)was obtained as a colorless powder (dichloro-
methane). M.p. 1178C; 1H NMR (400 MHz, CDCl3): d=4.18 (s, 4H,
-CH2-), 7.31–7.35 and 7.53–7.57 (AA’BB’-m, 4H, ortho-subst. arom. ring),
7.39–7.43 and 7.48–7.51 ppm (AA’BB’-m, 8H, para-subst. arom. ring);
13C NMR (100 MHz, CDCl3): d=15.09 (t), 86.19 (s), 86.29 (s), 90.34 (s),
93.18 (s), 122.21 (s), 123.75 (s), 125.61 (s), 128.38 (d), 131.53 (d), 131.88
(d), 131.92 ppm (d); IR (KBr): n˜ =2996 (w), 2213 (w), 1508 (s), 1201 (s),
834 (s), 750 (s), 608 cmꢀ1 (s); UV (acetonitrile): lmax (log e)=196 (4.78),
296 (4.95), 332 nm (4.56); MS (70 eV): m/z (%): 514 (22) [M+], 512 (40)
[M+], 510 (22)[ M+], 352 (62), 351 (100), 350 (92), 176 (60); elemental
analysis calcd (%)for C 28H16Br2: C 65.65, H 3.15; found: 65.67, H 3.20.
propylamine (50 mL)by heating the reaction mixture for 18 h under
reflux. After work-up (see GP 2)the bis-protected propargyl ether
(2.65 g, 98%)was isolated as colorless needles (dichloromethane.) M.p.
1258C; 1H NMR (400 MHz, CDCl3): d=1.55–1.91 (m, 12H, THP-ring),
3.54–3.60 (m, 2H, THP-ring), 3.86–3.92 (m, 2H, THP-ring), 4.46–4.53
(AB-q, J=15.8 Hz, 4H, propargyl-CH2-), 4.89 (t, J=3.3 Hz, 2H,
-CH(O)2), 7.41–7.51 ppm (AA’BB’-m, 8H, arom. H); 13C NMR
(100 MHz, CDCl3): d=19.06 (t), 25.39 (t), 30.30(t), 54.77 (t), 62.06 (t),
85.42 (s), 87.20 (s), 90.75 (s), 122.82 (s), 123.01 (s), 131.46 (d), 131.80 ppm
(d); IR (KBr): n˜ =2940 (m), 2849 (w), 2238 (w), 1517 (s), 1200 (s), 1120
(s), 1029 (s), 841 cmꢀ1 (s); UV (acetonitrile): lmax (log e)=198 (4.67), 218
(4.34), 312 (4.80), 334 nm (4.80); MS (70 eV): m/z (%): 454 (25) [M+],
354 (23), 353 (28), 270 (35), 254 (100), 85 (15); elemental analysis calcd
(%)for C 30H30O4: C 79.29, H 6.65; found: C 79.18, H 6.62.
d) Debromination of 77: On debromination of 77 according to GP 3 no
dimeric hydrocarbons could be isolated from the reaction mixture.
c) Bis-(4-(3-bromo-1-propynyl)phenyl)acetylene (76): According to GP 1
the above bis-THP ether (2.00 g, 4.40 mmol)was treated with triphenyl-
phosphine (2.77 g, 10.56 mmol)and bromine (1.69 g, 10.56 mmol)in di-
chloromethane (100 mL). After work-up (see GP 1) 76 (1.54 g, 85%)was
obtained as slightly yellow needles (dichloromethane). M.p. 1948C;
1H NMR (400 MHz, CDCl3): d=4.17 (s, 4H, propargyl-CH2), 7.41–
7.48 ppm (AA’BB’-m, 8H, arom. H); 13C NMR (100 MHz, CDCl3): d=
15.08 (t), 86.19 (s), 86.25 (s), 90.96 (s), 122.23 (s), 123.36 (s), 131.56 (d),
131.89 ppm (d); IR (KBr): n˜ =2998 (w), 2216 (w), 1517 (s), 1202 (s), 839
(s), 609 cmꢀ1 (s); UV (acetonitrile): lmax (log e)=198 (4.72), 220 (4.34),
318 (4.79), 338 nm (4.74); MS (70 eV): m/z (%): 414 (10) [M+], 412 (20)
[M+], 410 (9)[ M+], 333 (61), 331 (60), 252 (100), 215 (84), 163 (13), 126
(33), 84 (56); elemental analysis calcd (%) for C20H12Br2: C 58.29, H
2.93; found: C 58.46, H 2.93.
X-Ray structure determinations: Crystal data and refinement details are
presented in Table 1. Data collection and reduction: Crystals were
mounted in inert oil on glass fibres and transferred to the cold gas stream
Table 1. Crystallographic data for compounds 52, 59a, and 59b.
52
C32H20
59a
59b
formula
Mr
C20H12O2
C20H12S2
316.42
404.48
284.30
habit
yellow tablet
0.45”0.4”0.11
orthorhombic
Pca21
colourless tablet
0.8”0.35”0.15
monoclinic
P21/c
colourless tablet
0.5”0.4”0.18
orthorhombic
Pbca
cryst. size [mm]
crystal system
space group
cell constants:
a [Š]
d) Debromination of 76: On debromination of 76 according to GP 3 no
dimeric hydrocarbons could be isolated from the reaction mixture.
8,10-Bis-(4-(3-bromo-1-propynyl)phenyl-ortho-diethynylbenzene (77)
9.265(2)9.060(3) 13.1532(12)
14.683(3)9.864(3) 15.1378(18)
15.750(3)8.670(2) 15.6714(16)
b [Š]
c [Š]
a) 1-(4-Bromophenyl)-3-tetrahydro-2H-2-pyranyloxy-1-propyne: Accord-
ing to GP 2 1-bromo-4-iodobenzene (5.0 g, 35.3 mmol)and 29 (5.93 g,
a [8]
90
90
90
42.4 mmol)were coupled in the presence of [Pd (PPh3)4] (0.800 g,
R
b [8]
90
90
2142.6
4
1.254
0.07
107.91(2)90
90
737.2
2
1.281
0.08
1312
ꢀ130
55
0.71 mmol)in anhydrous propylamine (80 mL)at room temperature (re-
action time: 24 h). After work-up (see above) the THP-ether (8.69 g,
84%)was isolated by kugelrohr distillation (170 8C, 1 Torr)as a colorless
oil. 1H NMR (400 MHz, CDCl3): d=1.53–1.90 (m, 6H, THP-ring), 3.53–
3.58 (m, 1H, THP-ring), 3.84–3.90 (m, 1H, THP-ring), 4.42–4.50 (AB-q,
J=15.8 Hz, 2H, propargyl-CH2), 4.79 (t, J=3.4 Hz, 1H, CH(O)2), 7.28–
7.43 ppm (m, 4H, arom. H); 13C NMR (100 MHz, CDCl3): d=18.95 (t),
25.30 (t), 30.19 (t), 54.63 (t), 61.89n (t), 84.61 (s), 86.36 (s), 96.83 (d),
121.63 (s), 122.60 (s), 131.45 (d), 133.19 ppm (s); IR (KBr): n˜ =2943 (s),
2870 (m), 2246 (w), 1486 (s), 1120 (s), 1026 (s), 1011 (s), 824 cmꢀ1 (s);
UV (acetonitrile): lmax (log e)=198 (4.39), 250 (4.40), 260 nm (4.36); MS
(70 eV): m/z (%): 296 (7) [M+], 294 (8)[ M+], 195 (100), 193 (99), 115
(52), 85 (43); elemental analysis calcd (%) for C14H15O2Br: C 56.97, H
5.12; found: C 56.87, H 5.14.
g [8]
90
3120.6
8
1.347
0.33
V [Š3]
Z
1x [Mgmꢀ3
]
m [mmꢀ1
(000)848
]
F
A
296
T [8C]
2qmax
ꢀ130
50
ꢀ100
50
refl. measured
refl. indep.
Rint
3859
1957
0.097
289
1811
1700
0.018
100
3256
2743
0.028
199
0
parameters
restraints
301
0
wR(F2, all refl.)0.193
0.114
0.072
b) 8,10-Bis-(4-phenyl-1-(3-tetrahydro-2H-2-pyranyloxy-1-propyne)-ortho-
R
S
G
0.076
1.03
0.23
0.044
1.02
0.22
0.034
0.86
0.18
diethynylbenzene:
7.0 mmol), the bromide (4.6 g, 15.49 mmol) prepared under a), and [Pd-
(PPh3)4] (0.69 g, 0.62 mmol)in propylamine (80 mL)was heated under
A
mixture of ortho-diethynylbenzene (0.89 g,
max. D1 [eŠ
]
ACHTREUNG
reflux for 24 h. Work-up as described under GP 2 provided the bis-THP-
ether (1.7 g, 44%), amorphous solid (dichloromethane). M.p. 918C;
1H NMR (400 MHz, CDCl3): d=1.49–1.91 (m, 12H, THP-ring), 3.54–3.59
(m, 2H, THP-ring), 3.86–3.92 (m, 2H, THP-ring), 4.46–4.53 (AB-q, J=
15.8 Hz, 4H, propargyl-CH2), 4.90 (t, J=3.4 Hz, 2H, -CH(O)2), 7.29–7.31
and 7.53–7.56 (AA’BB’-m, 4H, ortho-subst. arom. ring), 7.33–7.43 and
7.47–7.52 ppm (AA’BB’-m, 8H, para-subst. arom. ring); 13C NMR
(100 MHz, CDCl3): d=18.99 (t), 25.33 (t), 30.23 (t), 54.70 (t), 85.37 (s),
87.19 (s), 89.98 (s), 93.21 (s), 96.86 (d), 122.78 (s), 123.15 (s), 125.57 (s),
128.20 (d), 131.39 (d), 131.71 (d), 131.77 ppm (d); IR (KBr): n˜ =2940 (s),
2214 (w), 1510 (m), 1119 (s), 1024 (s), 836 cmꢀ1 (s); UV (acetonitrile):
of the diffractometer (52, 59a: Stoe STADI-4; 59b: Siemens P4, with ap-
propriate low temperature attachments). Measurements were performed
with monochromated MoKa radiation. Structure refinement: The struc-
tures were refined anisotropically against F2 (program SHELXL-97, G.
M. Sheldrick, University of Gçttingen). Hydrogen atoms were included
with a riding model. For 52, intensity data were weak and displacement
parameters were therefore restrained with the commands DELU and
SIMU. In the absence of significant anomalous scattering, the Flack pa-
rameter is meaningless.
9476
www.chemeurj.org
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 9462 – 9477

1,x-Elimination Reactions
FULL PAPER
CCDC-645858 (52), -645859 (59a), -645860 (59b)contains the supple-
mentary crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. The structure determination of
compound 49 was reported in our earlier communication,[18] and the data
were deposited under the number CSD-401565; the Cambridge refcode
is ZEZSIG.
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Acknowledgements
We thank the Fonds der Chemischen Industrie for the generous and con-
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Received: May 31, 2007
Published online: October 26, 2007
Chem. Eur. J. 2007, 13, 9462 – 9477
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9477