9-Oxabicyclo[3.3.1]nona-2,6-diene. Short access and allylic bromination

Article abstract of DOI:10.1515/znb-2005-1106

9-Oxabicyclo[3.3.1]nona-2, 6-diene (3) has been synthesized from cycloocta-1, 5-diene in two steps in an overall yield of 88%. The dihedral-angle dependence of its ¹H solution NMR data and the double signal set of its ¹³C CP MAS NMR spectrum correspond to the results of the single crystal structure analysis. Reaction of 3 with N-bromosuccinimide in the presence of sodium peroxodisulfate or benzoylperoxide has led in good yield to a dibromo derivative 4, and a tribromo derivative 5, respectively. Compounds 4 and 5 feature two allylic bromine suestituents, while an additional vinylic bromine atom is present in 5. According to a single crystal structure study the lattice of 4 consists of pairs of enantiomers similar to those found in the case of 3.

Full text of DOI:10.1515/znb-2005-1106

9-Oxabicyclo[3.3.1]nona-2, 6-diene. Short Access and Allylic Bromination
Ghada Bassionia, Fernando S. Delgadob, Matthieu Jaeggya, Frank H. Ko¨hlera,
Stefan Nogaia, and Catalina Ruiz-Pe´rezb
a Department Chemie, Technische Universita¨t Mu¨nchen, D-85747 Garching, Germany
b Laboratorio de Rayos X y Materiales Moleculares, Departamento de Fisica Fundamental II,
Universidad de La Laguna, Avda Astrofisico Francisco Sanchez, E-38204 La Laguna, Spain
Reprint requests to Prof. Dr. F. H. Ko¨hler. E-mail: f.h.koehler@lrz.tu-muenchen.de
Z. Naturforsch. 60b, 1143 – 1148 (2005); received June 26, 2005
9-Oxabicyclo[3.3.1]nona-2, 6-diene (3) has been synthesized from cycloocta-1, 5-diene in two
steps in an overall yield of 88%. The dihedral-angle dependence of its1H solution NMR data and the
double signal set of its 13C CP MAS NMR spectrum correspond to the results of the single crystal
structure analysis. Reaction of 3 with N-bromosuccinimide in the presence of sodium peroxodisulfate
or benzoylperoxide has led in good yield to a dibromo derivative 4, and a tribromo derivative 5,
respectively. Compounds 4 and 5 feature two allylic bromine substituents, while an additional vinylic
bromine atom is present in 5. According to a single crystal structure study the lattice of 4 consists of
pairs of enantiomers similar to those found in the case of 3.
Key words: Bicyclic Ether, Allylic Bromination, Vinylic Bromination, Crystal Structure
Introduction
O
The parent bicyclic ether 9-oxabicyclo[3.3.1]nona-
2, 6-diene (cf. 3 in Scheme 1; for simplicity, the same
atom numbering is used for both enantiomers) has been
known for almost four decades [1], and yet it attracts
current interest, because it is a potential ligand of cat-
alytically active metal complexes [2, 3]. Thus, a zirco-
nium complex derived from 3 has been claimed to cat-
alyze the polymerization of ethylene and the copoly-
merization of ethylene and 1-butene [3]. For this sort
of studies and for the preparation of substituted deriva-
tives an efficient synthesis of 3 was necessary. An ef-
fort has been made by Eaton and Millikan [4] who
have reviewed early work and designed an improved
synthesis, which led to a 7/1 mixture of 3 and the
isomer 9-oxabicyclo[4.2.1]nona-2, 4-diene, 3’. Check-
ing their procedure [5] showed that the overall yield
of 29% starting from cycloocta-1,5-diene could not be
improved. Also, attempts to replace the toxic solvent
HMPT by quinoline gave 3 and 3’ in a ratio of only 2/1,
while N-methylpyrrolidone failed to give any bicyclic
ether. Therefore, we have worked out a new procedure
2b
2a
NIS, MeOH
95%
I
I
+
O
1
KOH, MeOH
92%
I I
O
O
5
1
4
3
8
2
6
7
+
3a
3b
O
3'
< 1%
Scheme 1.
Results and Discussion
When using cycloocta-1, 5-diene (1), as starting
and thoroughly characterized the title compound. Par- compound for the synthesis of 3 the key problem is to
allel to this work [5, 6] the group of Haufe has obtained avoid the formation of any 9-oxabicyclo[4.2.1]nonane
similar results [7]. As a basis for further studies, first derivatives as a byproduct of the desired 9-oxabi-
steps towards functionalizing the allylic position of 3 cyclo[3.3.1]nonane isomers. The best procedure is the
gave two new bromo derivatives.
reaction of 1 with N-iodosuccinimide with a 85% yield
c
0932–0776 / 05 / 1100–1143 $ 06.00 ꢀ 2005 Verlag der Zeitschrift fu¨r Naturforschung, Tu¨bingen · http://znaturforsch.com
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G. Bassioni et al. · 9-Oxabicyclo[3.3.1]nona-2, 6-dienes
◦
Fig. 1. 13C CP MAS NMR spectrum of 3 at −15 C and
ν
rot = 5 kHz. Spinning sidebands are labeled by asterisks.
of the diiodo derivatives 2 and with only 1% contami-
nation of the [4.2.1]-bicyclic analogue [8] (Scheme 1).
It turned out that the yield of 2 can be increased to 95%.
Two single crystal X-ray studies [7, 9] have shown that
the synthesis yields the enantiomers 2a and 2b. As has
been demonstrated previously, dehydrohalogenationof
2a and 2b gives 3 in 18% and 90% yield when using
KOH [10] and dicyclohexylmethylamine [11], respec-
tively. We have optimized the first procedure (92%),
while Haufe’s group [7] has applied the second one
with virtually the same result (88%). It is worth noting
that because of the high volatility of 3 careful control
is advisable for any solvent removal.
Fig. 2. Organization of 9-oxa bi cyclo[3.3.1]nona-2, 6-diene
˚
molecules (3) in the unit cell. Selected bond lengths [A]
and angles [◦]: C1-C2 1.5059(18), C5-C6 1.5061(17), C2-
C3 1.3241(19), C6-C7 1.3257(17), C3-C4 1.5017(17), C7-
C8 1.5006(18), C4-C5 1.5311(17), C1-C8 1.5291(17), O-C1
1.4406(14), O-C5 1.4404(14), O-C1-C2 110.60(9), O-C5-
C6 110.57(9), O-C1-C8 108.54(10), O-C5-C4 109.15(10),
C2-C1-C8 112.40(12), C4-C5-C6 111.65(10), C1-O-C5
109.96(9).
The 1H and 13C NMR signal shifts of 3 in so-
lution mostly confirmed previous reports [2, 12, 13]
within the experimental error limits. This work adds
proton coupling constants (Table 1, Experimental Sec-
tion), which reflect the geometry of 3 as far as three-
bond couplings and their dihedral angle dependence
are concerned (for details see below). The 1H NMR
signals showed symmetric many-line patterns originat-
ing from couplings as small as 0.4 Hz. Small cou-
plings are not given in Table 1, because the assignment
was ambiguous. The two multiplet components of the
signal of H4/8exo (separation 17.2 Hz) are somewhat
asymmetric so that the coupling constants are less
precise.
of enantiomers 3a and 3b are present in the unit cell
(Fig. 2) in accordance with the centrosymmetric space
group P21/c. The molecules are arranged such that ir-
regular stacks of only R, R or S, S enantiomers are
formed in a and b direction of the unit cell, while along
the c direction the stacks are made up from alternat-
ing enantiomers. Enantiopure samples of 3a and 3b
have been prepared recently [2], but no solid-state stud-
ies have been performed. The intermolecular olefinic
˚
C···C distances of 3a and 3b exceed 5.4 A, which con-
firms the absence of π interactions as indicated by the
13C MAS NMR data. The molecules adopt a distorted
double-chair conformation of two six-membered rings
that are fused at C1, C5, and O9. This entails dihedral
In the solid-state 13C NMR spectrum of 3 (Fig. 1) angles of φ(H3, C3, C4, H4exo)= 73.8◦, φ(H7, C7,
signals were found at positions very close to those of C8, H8exo)= 74.6◦, φ(H3, C3, C4, H4endo)= 45.2◦,
and φ(H7, C7, C8, H8endo)= 44.3◦. The dihedral an-
gle dependence of vicinal coupling constants is well
the solution spectrum, which means that intermolec-
ular π interactions must be small. The olefinic sig-
nals showed a pronounced shift anisotropy as ex- known [15, 16] and can be expressed as 3J(H,H) =
7 − cosφ + 5cos2φ. Inserting mean angles into the
pected [14]. Surprisingly, however, two sets of signals
were found rather than one in solution. This could be
equation yields 3J(H,H) values (Table 1) which are in
due to two different molecules in the asymmetric unit agreement with the experimental data. The fragment
or to a change from C2 symmetry in solution to C1 H7, C7, C8, H8 yields very similar values. It follows
that in solution and in the crystal the structure of 1 is
very similar, and if rapid conformational changes like
in the solid state. A single crystal X-ray study estab-
lished symmetry lowering to be responsible. Two pairs
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G. Bassioni et al. · 9-Oxabicyclo[3.3.1]nona-2, 6-dienes
O
1145
O
Br
Br
Br
Br
4a
4b
NBS, Na2S2O8, 95%
O
O
3a
3b
NBS, (Ph2CO2)2, 75%
O
Br
Br
5
Br
Scheme 2.
Fig. 3. Organization of the exo, exo-4, 8-dibromo-9-oxabi-
cyclo[3.3.1]nona-2, 6-diene molecules◦(4) in the unit cell.
C5-C6 1.496(35), C2-C3 147(2), C6-C7 1.482(18), C3-
C4 1.462(21), C7-C8 1.493(19), C4-C5 1.519(20), C1-
C8 1.504(34), O-C1 1.421(16), O-C5 1.420(15), C4-Br1
1.984(43), C8-Br2 1.981(12), O-C1-C2 110.2(9), O-C5-C6
112.1(9), O-C1-C8 109.9(9), O-C5-C4 108.8(9), C2-C1-C8
110.2(11), C4-C5-C6 109.6(9), C1-O-C5 109.8(8).
chair-boat flips occur, the distorted double-chair must
be more stable.
˚
Selected bond lengths [A] and angles [ ]: C1-C2 1.485(27),
The entry to 9-oxabicyclo[3.3.1]nona-2, 6-dienes
which are substituted in the allylic position was
achieved by Wohl-Ziegler bromination [17, 18]. As
illustrated in Scheme 2, the reaction of 3 with N-
bromosuccinimide (NBS) did not only lead to substi-
tution in the allylic but also the vinylic positions. The
reaction turned out to depend strongly on the radical
starter. Thus, when dibenzoylperoxidewas used the tri-
bromo derivative 5 was obtained in 85% yield, while
in the case of 2, 2’-azoisobutyronitrile only a tetra-
bromo derivative lacking double bonds was detected
by GC/MS and NMR analysis. In contrast, sodium per-
oxodisulfate gave a 95% yield of the enantiomeric di-
bromo derivatives 4a and 4b. Quite notably, the reac-
tion is stereoselective with bromine only in the exo po-
sition of 4 and 5 as established by the coupling con-
gles for C1, C2, C3, C4 (4: 0.85◦, 3: 2.0◦) and C5, C6,
C7, C8 (4: −3.3◦, 3: 1.9◦), while those of O, C5, C4,
C3 (4: 49.2◦, 3: 47.3◦) and O, C1, C8, C7 (4: 50.2◦,
3: 45.6◦) are only 10 – 15◦ smaller than expected for
3
undistorted rings. The calculation of the J(H,H) cou-
pling constants from the dihedral angle pairs φ(H3, C3,
C4, H4endo)= 45.2◦, and φ(H7, C7, C8, H8endo)=
44.3◦ as well as φ(H1, C1, C8, H8endo)= 76.7◦
and φ(H5, C5, C4, H4endo)= 73.3◦ gave values
which are in good agreement with the experiment
(Table 1).
3
stants J(H3/7, H4/8) (5.2 to 5.6 Hz in Table 1) and
confirmed by X-ray analysis of 4.
The tribromo derivative 5 has been established by
In the crystal exo, exo-4, 8-dibromo-9-oxabi- elemental analysis as well as by mass spectrometry and
cyclo[3.3.1]nona-2, 6-diene features two pairs of enan- NMR spectroscopy. In particular, the three-bond pro-
tiomers 4a and 4b in line with the space group Cc ton coupling constants of H4 and H8 leave no doubt
(Fig. 3). The alignment of 4 in the crystal resembles that the allylic bromo substituents are in exo position.
that of 3 after rearranging the crystal axes, and the ge- All coupling patterns of the 1H NMR spectrum are
ometric data do not depend strongly on the substitu- comparatively simple and prove to be helpful for the
tion. Likewise, the conformation of 4 is similar to that assignment of the correspondingspectra of compounds
of 3. There is a distortion of the double chair due to the 3 and 4. Work aiming at metal-halogen exchange is
olefinic carbon atoms which entail small dihedral an- now in progress.
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G. Bassioni et al. · 9-Oxabicyclo[3.3.1]nona-2, 6-dienes
Table 1. NMR dataa of compounds 3, 4, and 5.
3
4
5
δ(C1/5) solid
δ(C1/5)
67.2, 66.6
66.3
4.31
72.7
4.79
4.1
δ(H1/5)
4.77 (H1), 4.76 (H5)
4.1 (H5, H6)
3J(H1/5, H2/6)
3J(H1/5, H8/4exo)
3J(H1/5, H8/4endo)
4J(H1/5, H3/7)
∼ 3.8
∼ 7.0 (6.0)
b
b
1.8 (2.4)
1.5
b
1.4 (H5, H7)
δ(C2/6) solid
δ(C2/6)
124.3, 122.5
122.6
5.50
10.2
3.8
125.8
5.88
10.0
4.1
δ(H2/6)
5.82 (H6)
10.1 (H6, H7)
4.1 (H6, H5)
3J(H2/6, H3/7)
3J(H2/6, H1/5)
4J(H2/6, H4/8exo)
2.6
δ(C3/7) solid
δ(C3/7)
132.5, 130.0
130.0
5.62
10.2
5.5 (6.3)
128.1
5.98
10.0
δ(H3/7)
6.24 (H3), 6.02 (H7)
10.1 (H7, H6)
5.6 (H3, H4), 5.2 (H7, H8)
3J(H3/7, H2/6)
3J(H3/7, H4/8endo)
3J(H3/7, H4/8exo)
4J(H3/7, H1/5)
5.2 (5.9)
2.0 (2.5)
b
1.5
1.4 (H7, H5)
δ(C4/8) solid
28.6, 27.2
28.3
2.33
δ(C4/8)
41.6
δ(H4/8exo)
3J(H4/8exo, H4/8endo)
3J(H4/8exo, H5/1)
3J(H4/8exo, H3/7)
4J(H4/8exo, H2/6)
17.2
∼ 7.0 (6.0)
∼ 2.0 (2.5)
∼ 2.6
1.39
17.1
δ(H4/8endo)
4.25
4.54 (H4endo), 4.30 (H8endo)
2J(H4/8endo, H4/8exo)
3J(H4/8endo, H3/7)
4J(H4/8endo, H5/1)
5.6 (6.3)
5.2 (5.9)
1.8 (2.4)
5.6 (H4, H3), 5.2 (H8, H7)
b
b
a
δ-Values (ppm) in solution unless stated otherwise; coupling constants in Hz,3J couplings calculated from X-ray results in italics (see
b
text);
assignment of coupling ambiguous.
Experimental Section
9-Oxabicyclo[3.3.1]nona-2, 6-diene (3a/b): A solution of
2 (40.5 g, 107 mmol) and KOH (43.6 g, 0.78 mol) in 270 ml
of dry methanol was heated at 150 ◦C in a stainless steel au-
toclave. The HI elimination was monitored by integrating the
1H NMR spectra. Thus, after 24 h the reaction mixture con-
tained 2, the monoiodo derivative, and 3 in the ratio 21/27/52.
The ratio shifted to 49/20/31 and 26/31/43 after two and three
days, respectively, until the reaction was complete after four
days. The autoclave was allowed to reach ambient temper-
ature. To its content was added diethylether until a homo-
geneous phase was obtained, and the reaction mixture was
worked up with water, a saturated solution of NH4Cl in water
and brine. The organic layer was dried with MgSO4 and the
solvent was distilled off slowly by using a Vigreux column
leaving behind brown crystals. Recrystallization from hexane
All starting chemicals were commercially available ex-
cept for endo, endo-2, 6-diiodo-9-oxabicyclo[3.3.1]nonane
(2) which was synthesized from cis, cis-cyclooca-1, 5-
diene [8]. The NMR spectra were recorded with Jeol Delta
400 (for solutions) and Bruker Avance 300 (for solid 3) spec-
trometers. The mass spectra were obtained through GC/MS
coupling by using a Hewlett Packard 5890 Series II gas chro-
matograph equipped with a HP-1 capillary (crosslinked sili-
cone gum, 12 m × 0.2 mm × 0.33 µm film) and a HP 5971
mass detector, temperature program SPLTL500.M; masses
are given for 79Br. Elemental analyses were carried out by
the microanalytical laboratory of the Department Chemie at
Garching.
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G. Bassioni et al. · 9-Oxabicyclo[3.3.1]nona-2, 6-dienes
1147
Table 2. Crystallographic data
3a/b
4a/b
and details of the data collec-
tion and structure refinement
for compounds 3a/b and 4a/b.
Empirical formula
Chemical formula weight
Unit cell dimensions
C8H10
122.16 g/mol
a = 5.4167 (1) A
b = 11.5589 (3) A
O
C8H8OBr2
279.96 g/mol
a = 9.242 (2) A
˚
˚
˚
˚
˚
b = 11.6221 (2) A
˚
a
w = 1/[σ2(Fo2) + (ap)2 + bp];
c = 10.2632 (2) A
c = 8.959 (2) A
α = 90.00◦
α = 90.00◦
p = (Fo2 +2F2)/3.
c
β = 100.66 (10)◦
β = 111.04 (3)◦
γ = 90.00◦
γ = 90.00◦
3
3
˚
˚
V = 631.50 (2) A
V = 898.1 (3) A
Cell formula units
Density
Crystal system, space group
Rad. wavelength λ (MO-Kα )
4
4
1.285 g cm−3
2.071 g cm−3
monoclinic, Cc
monoclinic, P21/c
0.71073 A
˚
˚
0.71073 A
Temperature
Exptl. Absorption coefficient
F(000)
143(2) K
0.083 mm−1
264
293(2) K
8.966 mm−1
536
Index region
0 ≤ h ≤ 6,
−12 ≤ h ≤ 11,
−13 ≤ k ≤ 15,
−11 ≤ l ≤ 9
6.5◦ < θ < 27.5◦
97.9%
0 ≤ k ≤ 13,
−12 ≤ l ≤ 12
2.68◦ < θ < 25.11◦
93.5%
Diffraction reflections θ
Completeness to θ = 25.11
Absorption correction
None
None
Reflections collected / unique
Reflection number > 2σ(I)
13829 / 1058 [R(int) = 0.030]
1348
2835 / 1581 [R(int) = 0.1092]
1348
Data / restraints / parameters
Extinction coefficient
Goodness-of-fit
1058 / 0 / 83
0.108 (18)
1.064
1581 / 2 / 107
none
1.110
Final R indices [I > 2σ(I)]
R Indices (all data)
R1 = 0.0392, wR2 = 0.1057
R1 = 0.0394, wR2 = 0.1060
0.167 and −0.185 eA−3
a = 0.0628/b = 0.1817
R1 = 0.0622, wR2 = 0.1497
R1 = 0.0763, wR2 = −0.31616
˚
Largest diffract. peak and hole
1.345 and −0.664 eA
Weighing schemea
a = 0.0759/b = 6.2911
gave 3a/b as a white microcrystalline powder. Yield 12.1 g placing Na2S2O8 by 10 mg of dibenzoylperoxide. After
(92%). – MS (EI, 70 eV): m/z (%) = 122 (90) [M+], 104 workup a white microcrystalline powder was obtained which
(20) [C8H8+], 91 (65) [C7H7+], 77 (85) [C6H5+], 68 (100) according to GC/MS consisted of 2, exo, exo-4, 8-tribromo-
[C4H4O+]. – C8H10O (122.16): calcd. C 78.65, H 8.25; 9-oxabicyclo-[3.3.1]nona-2, 6-diene (5) and 4 in the ratio
found C 78.63, H 8.32. Experimental and calculated NMR 85/15. Yield 2.5 g (5: 75%, 4: 13%). – MS (EI, 70 eV):
data are collected in Table 1.
m/z (%) = 359 (2) [M+], 281 (14) [MH+−Br], 277 (13)
[M+−Br], 199 (14) [M+−2Br], 172 (14) [M+−2Br], 169
(100) [M+−2Br], 119 (27) [M+−3Br].
exo, exo-4, 8-Dibromo-9-oxabicyclo[3.3.1]nona-2, 6-di-
ene (4a/b): N-Bromosuccinimide (2.9 g, 16.3 mmol) was
suspended in a solution of 3 (1.0 g, 8.2 mmol) in 85 ml of dry
CCl4. After addition of 0.15 g Na2S2O8 the suspension was
heated to reflux for 40 h. The hot reaction mixture was fil-
tered, water (100 ml) was added, the phases were separated,
and the organic layer was dried with MgSO4. After removal
of CCl4 by using a rotary evaporator brown crystals were
obtained which after washing with clean CCl4 became col-
orless. Yield 1.5 g (95%). – MS (EI, 70 eV): m/z (%) = 282
(15) [MH+], 278 (6) [M+], 199 (100) [M+−Br], 119 (38)
[M+−2Br]. – C8H8Br2O (279.96): calcd. C 34.32, H 2.88;
found C 34.35, H 2.96. Experimental and calculated NMR
data are collected in Table 1.
Single crystal X-ray structure determination of compounds
3a/b and 4a/b
Suitable crystals of 3a/b and 4a/b were grown by recrys-
tallization from hexane and by slow evaporation of a satu-
rated solution in CH2Cl2, respectively. Crystal data and de-
tails of the structure determination are summarized in Ta-
ble 2.
3a/b: A crystal of suitable quality and size was mounted
on the end of a quartz fiber in inert perfluoropolyalkylether
and used for intensity data collection on a Nonius DIP2020
diffractometer, employing graphite-monochromated Mo-Kα
˚
Bromination of 3 with N-bromosuccinimide/dibenzoylper- radiation (λ = 0.71073 A). Data reduction was done us-
oxide: The same quantities and the same procedure as de- ing the DENZO\SCALEPACK [19] suite of programs. The
scribed in the previous paragraph were used except for re- structure was solved by direct methods and refined with full-
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1148
G. Bassioni et al. · 9-Oxabicyclo[3.3.1]nona-2, 6-dienes
matrix least-squares calculations on F2 using the SHELXS- (WINGX) [21]. The structure was solved by direct methods
97 [20] and SHELXL-97 [20] programs. Thermal motion and refined with full-matrix least-squares technique on F2
was treated anisotropically for all non-hydrogen atoms. All using the SHELXS-97 [20] and SHELXL-97 [20] programs.
hydrogen atoms were calculated in ideal positions and re- The hydrogen atoms were positioned from and refined with
fined after a riding model. A summary of the crystallographic isotropic temperature factors. The final geometrical calcula-
data and structure refinement is given in Table 2.
tions were carried out with PARST97 [22] program. A sum-
4a/b: A single crystal of the compound was mounted mary of the crystallographic data and structure refinement is
on a Bruker-Nonius KappaCCD diffractometer. Orienta- given in Table 2. – CCDC reference numbers 279270 (3a/b),
tion matrix and lattice parameters were obtained by least- 286021 (4a/b).
squares refinement of the reflections obtained by a θ-χ
scan (Dirax/lsq method). Diffraction data were collected
Acknowledgements
employing graphite-monochromated Mo-Kα radiation (λ =
Helpful discussion with Dr. E. Herdtweck and financial
support by the Deutsche Forschungsgemeinschaft are grate-
fully acknowledged.
˚
0.71073 A). All calculations for data reduction, structure
solution, and refinement were done by standard procedures
[13] E. Cuthbertson, D. D. McNicol, J. Chem. Soc., Perkin
Trans. 1893 (1974).
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Unauthenticated
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