Functionalisation of 2-(1-naphthyl)-5-phenyl-1,3,4-oxadiazole with alkoxysilanes

Article abstract of DOI:10.1055/s-2001-13420

A short route for the synthesis of 2,5-diaryl-1,3,4-oxadiazoles with rigid connections to alkoxysilanes 7, 8, 9 via Heck reaction of the bromo compound 3 with vinylalkoxysilanes 4, 5, 6, and also via palladium-catalysed vinylation to the styrene 11 and cross-metathesis with vinyl silanes is described. An extension of the conjugated system to 14 is possible with silyl-substituted styrene 13.

Full text of DOI:10.1055/s-2001-13420

PAPER
893
Functionalisation of 2-(1-Naphthyl)-5-phenyl-1,3,4-oxadiazole with
Alkoxysilanes
Erli Sugiono, Heiner Detert*
Institut für Organische Chemie, Johannes Gutenberg-Universität Mainz, Duesbergweg 10–14, 55099 Mainz, Germany
Fax +49(0)61313925396; E-mail: detert@mail.uni-mainz.de
Received 19 December 2000; revised 5 March 2001
include those units in the main chain10–13 or as side
chains.14–16 In this paper, we report the synthesis of naph-
thyl-oxadiazolylstyrenes and -stilbene with alkoxysilane
units, compounds which can be useful for UV absorbing
Abstract: A short route for the synthesis of 2,5-diaryl-1,3,4-oxadi-
azoles with rigid connections to alkoxysilanes 7, 8, 9 via Heck reac-
tion of the bromo compound 3 with vinylalkoxysilanes 4, 5, 6, and
also via palladium-catalysed vinylation to the styrene 11 and cross-
metathesis with vinyl silanes is described. An extension of the con- or luminescent coatings and also for curable electron
jugated system to 14 is possible with silyl-substituted styrene 13.
transport layers in electro-optical devices.
Key words: Heck reaction, heterocycles, metathesis, silicon, mate-
rials science
The synthesis of the title compounds required the con-
struction of the 1,3,4-oxadiazole and the connection of the
aromatic unit and the alkoxysilane. Due to the sensitivity
of the latter towards acids and hydrolysis, the former was
Organodi- and trialkoxysilanes hydrolyse to reactive sil-
anols condensing to oligomers or three-dimensional silox-
ane networks with covalently linked organic groups. The
mild conditions of this process allow the synthesis of or-
ganic-inorganic hybrid materials and coatings with a vari-
ety of potential applications depending on the organic
moiety. Aromatic hydrocarbons with extended π-systems
have been directly coupled with alkoxysilanes1–3 and re-
cently, some electro-optically active molecules were
linked to aminopropyltrialkoxysilanes4–6 and converted to
hybrid materials. 2,5-Diaryl-1,3,4-oxadiazoles are widely
used as additives in liquid and plastic scintillators7 and as
hole blocking/electron transporting materials in organic
light emitting diodes.8 Small molecules like 5-(4-tert-bu-
tylphenyl)-2-(4-diphenyl)-1,3,4-oxadiazole are applied as
vacuum-deposited layers, however, the stability of these
films is only moderate.9 Polymers for these applications
prepared first. Besides, the cyclocondensation of acyl hy-
drazides,17 the acylation of tetrazoles and thermal ring
transformation (Huisgen reaction)18 is a general method
for the synthesis of 1,3,4-oxadiazoles. Tetrazole 119 and
the acid chloride 2 were transformed to 3 – a unit well
known for its high electron affinity and good electron
transport capability.15 A bromine atom on the phenyl ring
of 3 serves as reactive site for the coupling of the chro-
mophore to the vinyl silanes. The connection of the aro-
matic unit
3
with the commercially available
ethoxysilanes 4–6 was performed via Heck reactions with
palladium(II)acetate and tris(2-methylphenyl)phosphine
as catalyst using anhydrous DMF as solvent (Scheme 1).
Among the different silanes 4–6 applied, allyltriethoxysi-
lane 6 gave the best results in the Heck reaction: 68% of 9
(115 °C, 3 hours). Comparable conditions were used for 4
(120 °C, 2 hours) and 5 (120 °C, 5 hours) to yield 42% of
Scheme 1 Synthesis of alkoxysilane-substituted diaryloxadiazoles
7 and 54% of 8, respectively. In contrast to the reactions
of 4 and 6 with 3, the more sluggish reaction of 5 to 8 was
accompanied by the competitive formation of small
amounts of diphenyl 1021 as a by-product. In a separate
Synthesis 2001, No. 6, 04 05 2001. Article Identifier:
1437-210X,E;2001,0,06,0893,0896,ftx,en;Z12100SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

894
E. Sugiono, H. Detert
PAPER
experiment under the same conditions but in the absence in a Barbier−Grignard reaction. The Pd-catalysed cou-
of vinylsilanes, 10 was formed from 3 in an Ullmann-type pling of 3 and 13 yielded stilbene 14 (31%), again accom-
reaction.22 Prolonged reaction times (5 hours) in the trans- panied by the formation of diphenyl 10.
formation of 3 and 4 to 7 gave rise to a secondary reaction;
the fission of the vinyl-silicon bond of 7 to yield styrene
11.
The alkoxysilanes 7, 8, and 9 are fairly stable towards hy-
drolysis and can be purified by chromatography using sil-
ica gel, on the condition that the crude product is
Vinyl silanes were proven reactive substrates23 in cross- separated from the solvents and salts of the reaction mix-
metathesis reactions. The ruthenium-catalysed cross-met- ture. These impurities particularly promote the hydrolysis
athesis was investigated as an alternative route to alkoxys- of the diethoxymethyl compound 14, resulting in a mix-
ilyl-substituted chromophores. A styrene carrying an ture of oligomeric siloxanes.
1,3,4-oxadiazole was prepared by Prasad et al.24 in three
We have described a brief synthesis of 2,5-diaryl-1,3,4-
steps via Wittig reaction and used for the synthesis of
oxadiazoles with rigid connections to ethoxysilyl groups
multi-branched structures. Starting from 3, a Pd-catalysed
(7−9, 14) by the Heck reactions of the 4-bromophenyl
vinylation with compressed ethene25,26 led to styrene 11 in
substituted heterocycle 3 and the vinyl-substituted silanes
4–6, and 13. The reactivity of the vinyl compounds is
strongly controlled by the silane, with ethene and allylsi-
69% yield (Scheme 2). This was subjected to cross-met-
athesis reactions with 523 and Grubbs catalyst27 [Cl2
(PCy3)2Ru=CHPh] 12 under continuous removal of
lane 6 giving the best results, followed by 5 which is su-
ethene by a gentle flow of dry and oxygen-free nitrogen.
perior to 4 and 13. In case of 5, a catalytic Ullmann
After a short time, the very clean reaction of 11 and 5
coupling to biaryl 13 was observed. Due to the ethoxysilyl
stopped (only 5, 8, and 11 could be detected by mass spec-
moieties, 7–9 and 14 are interesting as conjugated systems
troscopy) and neither additional catalyst nor elevated tem-
with high electron affinity for the preparation of polysi-
perature nor sonication was suitable to promote the
loxanes and organic-inorganic hybrid materials for appli-
conversion. Work-up by chromatography gave 8 in 12%
cations like coatings or electro-optical devices.4,5
yield and 83% of unchanged 11; while the reaction of 4
with 11 generated only traces of 7.
IR spectra: Beckman Acculab 4. NMR spectra: CDCl3, Bruker AC
200 and AM 400. Chemical shifts are reported in ppm and refer-
enced to the solvent as internal standard. Mass spectra: 70 eV, Vari-
an MAT 711 (EI), MAT 95 (FD). The elemental analyses were
performed at the microanalytical laboratory of the Chemical Insti-
tute of the Johannes Gutenberg–Universität, Mainz, Germany. Mps
are uncorrected. Chemicals were used as received; solvents were
dried according to standard procedures and distilled. DMF was
stirred with CaH2 for 5 h at 120 °C, distilled in vacuum and stored
over activated molecular sieves.
2-(4-Bromophenyl)-5-(1-naphthyl)-1,3,4-oxadiazole (3)
A mixture of tetrazole 1 (6.5 g, 0.033 mol) and anhyd pyridine
(35 mL) was stirred and 4-bromobenzoyl chloride 2 (8.0 g, 0.036
mol) was added in portions of 1 g. The mixture warmed up, N2 was
evolved, and finally a solid separated. After the gas evolution
ceased, the mixture was heated to 100 °C for 1.5 h and poured into
MeOH (70 mL). H2O (30 mL) was added and the solid was isolated
by filtration and recrystallised from toluene. Yield: 10.1 g (87%),
slightly brownish crystals, mp 140 °C.
IR (KBr): ν = 3025, 1590, 1520, 1470, 1397, 1240, 1087, 1070,
1002, 830, 800, 765 cm−1.
Scheme 2 Alkoxysilyl-substituted diaryloxadiazoles via Heck reac-
1H NMR (CDCl3): δ = 7.55 (m, 2H, 3-H, 6-H, naph), 7.68 (d, 2H,
tions and cross-metathesis
J = 8.5 Hz, 3-H, 5-H, ph), 7.70 (m, 1H, 7-H, naph), 7.92 (d, 1H,
J = 8.2 Hz, 5-H, naph), 8.04 (d, 3H, J = 8.5 Hz, 2-H, 6-H, ph; 4H,
naph), 8.24 (d, 1H, J = 7.4 Hz, 2-H, naph), 9.25 (d, 1H, J = 8.8 Hz,
8-H, naph).
13C NMR (CDCl3): δ = 120.0, 122.6, 126.3, 129.8, 133.6 (Cq), 124.6
(C-3, naph), 126.0 (C-8, naph), 126.6 (C-6, naph), 128.0 (C-7,
A further extension of the conjugated system of 7–9 will
alter the optical and electrical properties of the chro-
mophore. 1,3,4-Oxadiazoles are strong activating groups
for methyl arenes in the Siegrist synthesis of stilbenes,28
naph), 128.1 (C-2, C-6 ph), 128.5 (C-5, naph), 132.2 (C-3, C-5, ph),
but the reaction conditions are not suitable for the sensi-
132.5 (C-4, naph), 163.1, 164.5 (C-2, C-5, oxd).
tive alkoxysilanes, and alkoxysilyl-substituted benzalde-
hydes or aniles are not available. A Heck reaction with
styrene 13 was successful for the preparation of a com-
MS (EI): m/z = 350.4 (51) Br-pattern [M+], 183 (22) Br-pattern
+
[C6H4BrCO+], 155 (100) [C10H7CO+], 127 (69) [C10H7 ].
pound with an additional phenylene unit separating the
2-(1-Naphthyl)-5-(4-vinylphenyl)-1,3,4-oxadiazole (11)
A solution of 3 (1.0 g, 2.8 mmol), Pd(OAc)2 (40 mg, 0.18 mmol),
alkoxysilyl and vinyl groups (Scheme 2). Silane 1320 was
prepared from 4-bromostyrene and triethoxymethylsilane
tris-o-tolylphosphine (160 mg, 0.53 mmol) and Et3N (0.6 g, 0.60
Synthesis 2001, No. 6, 893–896 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Functionalisation of 2-(1-Naphthyl)-5-phenyl-1,3,4-oxadiazole with Alkoxysilanes
895
mmol) in anhyd DMF (30 mL) was placed in an autoclave, purged
with N2, and stirred under ethene (30 bar) for 40 h at 100 °C. The
cooled mixture was diluted with H2O (100 mL), extracted with
CHCl3 (3 × 50 mL), and the combined organic solutions were
washed with H2O (3 × 100 mL), and dried (MgSO4). The solvent
was evaporated and the residue was purified by chromatography on
silica gel (petroleum ether−EtOAc, 5:1). Yield: 0.58 g (69%),
slightly yellowish crystals, mp 134 °C.
with an efficient reflux condenser and bubble counter, and a gentle
flow of dry and O2-free N2 was bubbled through the solution to re-
move ethene (16 h, ambient temperature). The solvent was stripped
off and the residue purified by chromatography. Yield: 55 mg
(12%) of 8 and 250 mg (83%) of 11.
IR (neat): ν = 3040, 2960, 2915, 1595, 1567, 1520, 1483, 1450,
1380, 1290, 1195, 1161, 1097, 1070, 958, 802, 772, 750 cm−1.
1H NMR (CDCl3): δ = 1.30 (t, 9H, J = 7.0 Hz, CH3), 3.90 (q, 6H,
J = 7.0 Hz, OCH2), 6.35 (d, 1H, J = 19.6 Hz, vin), 7.24 (d, 1H,
J = 19.6 Hz, vin), 7.53–7.73 (m, 5H, ph, naph), 7.95 (d, 1H, J = 8.0
Hz, naph), 8.04 (d, 1H, J = 8.0 Hz, naph), 8.16 (d, 2H, J = 8.0 Hz, 2-
H, 6-H, ph), 8.26 (dd, 1H, J = 8.0, 1.0 Hz, naph), 9.29 (d, 1H, J = 8.4
Hz, naph).
13C NMR (CDCl3): δ = 18.3 (CH3), 58.7 (OCH2), 120.5, 123.7,
130.1, 133.9, 140.8 (Cq), 121.1, 124.9, 126.3, 126.8, 127.3 (2C),
127.4 (2C), 128.2, 128.4, 128.7, 132.7, 147.6 (CH), 164.0, 164.6
(C-2, C-5, oxadiazole).
IR (KBr): ν = 3070, 3040, 2990, 2910, 1615, 1600, 1565, 1520,
1485, 1400, 1242, 1090, 1070, 1008, 980, 925, 900, 842, 820, 770,
715, 696, 655 cm−1.
1H NMR (CDCl3): δ = 5.39 (d, 1H, J = 10.7 Hz, vin), 5.87 (d, 1H,
J = 17.5 Hz, vin), 6.77 (dd, 1H, J = 17.5, 10.7 Hz, vin), 7.59 (m, 3H,
ph, naph), 7.71 (2 × t, 2 × 1H, J = 8.5 Hz, naph), 8.15 (d, 2H, J = 8.0
Hz, ph), 7.93, 8.05, 8.26, 9.28 (4 d, 4 × 4 × 1H J = 8.4 Hz, 2-H, 4-H,
5-H, 8-H, naph).
13C NMR (CDCl3): δ = 116.4, 124.9, 126.3, 126.8, 126.9 (2C),
127.9 (2C), 128.2, 128.4, 128.7, 132.6, 135.9 (CH), 120.5, 123.0,
130.1, 133.9, 140.9 (Cq), 167.5, (oxd) (1 signal of the heterocycle is
missing).
MS (FD): m/z = 922 (1) [M2 ], 461 (100) [M+], 230.7 (1) [M2+].
+
2-(1-Naphthyl)-5-{4-[(1E)-3-(triethoxysilyl)-1-
propenyl]phenyl}-1,3,4-oxadiazole (9)
MS (EI): m/z = 298 (46) [M+], 241 (77), 215 (100).
Pd(OAc)2 (20 mg, 0.09 mmol), tris-o-tolylphosphine (55 mg,
0.18 mmol), and Et3N (0.43 g, 4.2 mmol) were added to a solution
of 3 (0.3 g, 0.85 mmol) and 6 (0.17 g, 0.85 mmol) in anhyd DMF
(30 mL) and stirred under N2 for 3 h at 115 °C. Extraction with tol-
uene-cyclohexane (1:1, 3 × 20 mL), washing with iced water, and
drying (MgSO4) was followed by chromatography on silica gel (tol-
uene−EtOAc, 5:1) to yield 270 mg (68%) of a slightly yellow solid,
mp 82 °C.
2-{4-[Diethoxy(methyl)silyl]ethenylphenyl}-5-(1-naphthyl)-
1,3,4-oxadiazole (7)
Prepared from 3 and 4 according to the procedure (a) described for
8. The reaction time was 2 h. The crude product was purified by col-
umn chromatography (silica gel, CHCl3−petroleum ether, 3:1).
Yield: 250 mg (42%) as a slowly crystallising yellowish oil, mp
98 °C.
The cross metathesis of 11 and 4, according to procedure (b) de-
scribed for 8, yielded <3% of 7.
IR (neat): ν = 3040, 2960, 2910, 2870, 1630, 1600, 1550, 1519,
1480, 1380, 1242, 1160, 1060, 955, 860, 802, 770, 740 cm−1.
IR (neat): ν = 3040, 2960, 2915, 1600, 1565, 1535, 1520, 1500,
1480, 1430, 1405, 1380, 1320, 1290, 1250, 1210, 1195, 1160, 1097,
1070, 1005, 802, 760, 735 cm−1.
1H NMR (CDCl3): δ = 0.30 (s, 3H, Si-CH3), 1.26 (t, 6H, J = 7.0 Hz,
CH3), 3.85 (q, 4H, J = 7.0 Hz, OCH2), 6.45 (d, 1H, J = 19.6 Hz, vin),
7.15 (d, 1H, J = 19.6 Hz, vin), 7.52–7.78 (m, 5H, ph, naph), 7.93 (d,
1H, J = 8.0 Hz, naph), 8.05 (d, 1H, J = 8.0 Hz, naph), 8.16 (d, 2H,
J = 8.0 Hz, 2-H, 6-H, ph), 8.26 (dd, 1H, J = 8.0, 1 Hz, naph), 9.27 (d,
1H, J = 8.8 Hz, naph).
13C NMR (CDCl3): δ = −4.2 (Si-CH3), 18.4 (CH3), 58.5 (OCH2),
120.5, 123.6, 130.2, 133.9, 141.0 (Cq), 124.9, 125.8, 126.3, 126.8,
127.3 (2C), 128.2, 128.4, 128.7, 132.6, 146.0 (CH), 164.0, 164.6
(C-2, C-5, oxadiazole).
1H NMR (CDCl3): δ = 1.28 (t, 9H, J = 7.0 Hz, CH3), 1.87 (dd, 2H,
J = 8.0, 1.0 Hz, Si-CH2), 3.86 (q, 6H, J = 7.0 Hz, OCH2), 6.42 (m,
2H, vin), 7.48 (d, 2H, J = 8.0 Hz, ph), 7.53–7.72 (m, 3H, naph), 7.94
(d, 1H, J = 8.0 Hz, naph), 8.04 (d, 1H, J = 8.0 Hz, naph), 8.11 (d, 2H,
J = 8.0 Hz, 2-H, 6-H, ph), 8.27 (dd, 1H, J = 8.0, 1.0 Hz, naph), 9.28
(d, 1H, J = 8.4 Hz, naph).
13C NMR (CDCl3): δ = 7.7 (Si-CH2), 18.2 (CH3), 22.7 (CH2), 40.5
(N-CH2), 58.4 (OCH2), 112.1 (2C), 115.0, 120.8, 126.2, 126.6,
127.9, 128.0, 128.3, 128.6, 130.0 (2C), 132.1, 133.8 (CH, Cq, 1 sig-
nal superimposed), 151.4 (C-N), 161.5, 164.9 (oxadiazole).
MS (FD): m/z = 475 (100) [M+].
2-(1-Naphthyl)-5{[4′-5(1-naphthyl)-1,3,4-oxadiazol-2-yl][1,1′-
biphenyl]-4-yl}-1,3,4-oxadiazole (10)
Procedure (a)
MS (FD): m/z = 431 (100) [M+], 215.7 (5) [M2+].
2-(1-Naphthyl)-5-{4-[(E)-2-(triethoxysilyl)ethenyl]phenyl}-
1,3,4-oxadiazole (8)
Procedure (a)
Synthesised according to the procedure described for 8 without add-
ing silane. After stirring for 5 h at 130–135 °C, the cooled mixture
was diluted with MeOH (60 mL) and the product was isolated by fil-
tration and washed with MeOH, CH2Cl2, and MeOH and dried.
Light orange plates with very poor solubility, yield: 153 mg, (6%);
mp 317 °C (Lit:21 mp 319–324 °C).
Pd(OAc)2 (20 mg, 0.089 mmol) and tris-o-tolylphosphine (50 mg,
0.180 mmol) were added to a solution of 3 (0.30 g, 0.89 mmol),
Et3N (0.45 g, 4.45 mmol) and silane 5 (0.17 g, 0.89 mmol) in anhyd
DMF (30 mL). The mixture was purged with N2 and stirred at
120 °C for 5 h. The cooled reaction mixture was stirred with a mix-
ture of cyclohexane and toluene (2:1, 4 × 40 mL) for 1 h, and the
combined hydrocarbon solutions were washed with iced water (3 ×
50 mL), and dried (MgSO4). Compound 8 was purified by chroma-
tography on silica gel (toluene−EtOAc, 5:1). Yield: 0.22 g (54%) as
a slowly crystallising yellowish oil, mp 118 °C.
Procedure (b)
A solution of α-naphthoylchloride (200 mg, 1.1 mmol) and 4,4′-
bis(5-tetrazolyl)biphenyl (145 mg, 0.5 mmol) in pyridine (3 mL)
was heated to 135 °C for 2 h. The hot mixture was poured into
MeOH (10 mL) and diluted with H2O (10 mL). The greenish solid,
isolated by filtration, was recrystallised from toluene. Yield: 155
1
mg (57%), orange powder. The spectra (IR, H NMR and MS) of
Procedure (b)
the compounds from both sources were identical.
Grubbs catalyst [Ru(PCy3)2(H5C6CH)]Cl2 (12, 2 mg) was added to
a solution of 5 (180 mg, 1 mmol) and 11 (300 mg, 1 mmol) in anhyd
benzene (8 mL) placed in a 2-necked round bottom flask equipped
IR (KBr): ν = 1570, 1503, 1470, 1398, 1245, 1185, 1125, 1090,
1070, 1025, 980, 960, 828, 797, 762, 735 cm−1.
Synthesis 2001, No. 6, 893–896 ISSN 0039-7881 © Thieme Stuttgart · New York

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E. Sugiono, H. Detert
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1H NMR (CDCl3): δ = 7.56–7.76 (m, 6H, naph), 7.88 (d, 4H, J = 8.2
Hz, ph), 7.96 (d, 2H, J = 8.6 Hz, naph), 8.07 (d, 2H, J = 8.3 Hz,
naph), 8.28–8.36 (m, 4H, ph + 2H naph), 9.31 (d, 2H, J = 8.3 Hz, 8-
H, naph).
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Mg turnings (2.7 g, 0.11 mol) were added to a magnetically stirred
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5.78 (d, 1H, J = 17.6 Hz, vin), 6.71 (dd, 1H, J = 10.8, 17.6 Hz, vin),
7.40 (d, 2H, J = 7.8 Hz, ph), 7.58 (d, 2H, J = 7.8 Hz, ph).
13C NMR (CDCl3): δ = −0.2 (Si-CH3), 18.4 (CH3), 58.5 (OCH2),
114.4 (CH2 vin), 125.6, 133.5, 136.8 (CH), 134.0 (Cq) (1 Cq super-
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(19) Jaiseval, J.; Jaiseval, N.; Parmar, S. S.; James, E. C. J.
Heterocycl. Chem. 1983, 20, 615.
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1968, 4, 357.
(22) Hassan, J.; Penalva, V.; Lavenot, L.; Gozzi, C.; Lemaire, M.
Tetrahedron 1998, 54, 13793.
(23) Pietraszuk, C.; Marciniec, B.; Fischer, H. Organometallics
2000, 19, 913.
2-[4-((E)-2-{4-[Diethoxy(methyl)silyl]phenyl}ethenyl)phenyl]-
5-(1-naphthyl)-1,3,4-oxadiazole (14)
Synthesised from 3 (220 mg, 0.62 mmol) and 13 (150 mg,
0.62 mmol) according to the procedure described for 8. Purification
by chromatography on silica gel (petroleum ether-toluene, 1:5), fol-
lowed with EtOAc eluted 14. Yield: 100 mg (31%) of a slightly yel-
low solid; mp 158 °C.
IR (CDCl3): ν = 3025, 2950, 2860, 1592, 1572, 1535, 1520, 1478,
1411, 1385, 1258, 1160, 1112, 1065, 1008, 950, 860, 833, 800, 770,
740, 720 cm−1.
1H NMR (CDCl3): δ = 0.36 (s, 3H, Si-CH3), 1.27 (t, 6H, J = 7.0 Hz,
CH3), 3.82 (q, 4H, J = 7.0 Hz, OCH2), 7.22 (m, 2H), 7.52–7.70 (m,
9H, ph, vin, naph), 7.94 (d, 1H, J = 7.8 Hz, naph), 8.05 (d, 1H,
J = 7.8 Hz, naph), 8.18 (d, 2H, J = 8.3 Hz, ph), 8.18 (d, 1H, J = 7.2
Hz, naph), 9.29 (d, 1H, J = 8.3 Hz, naph).
(24) Chung, S. J.; Kim, K. S.; Lin, T. C.; He, G. S.; Swiatkiewicz,
J.; Prasad, P. N. J. Phys. Chem. B 1999, 103, 10741.
(25) Heitz, W.; Brügging, W.; Freund, L.; Gailberger, M.;
Greiner, A.; Jung, H.; Kampschulte, U.; Nießner, N.; Osan,
F.; Schmidt, H.-W.; Wicker, M. Makromol. Chem. 1988,
189, 119.
13C NMR (CDCl3): δ = −4.2 (Si-CH3), 18.2 (CH3), 58.5 (OCH2),
120.6, 122.7, 124.8, 126.1 (2C), 126.2, 126.7, 127.0 (2C), 127.3
(2C), 128.1, 128.1, 128.3, 128.6, 130.1, 131.0, 132.5, 133.9, 134.4
(2C), 135.1, 138.1, 140.7(CH, Cq), 164.0, 164.5 (C-2, C-5, oxd).
MS (FD): m/z = 507.2 (100) [M+].
(26) Detert, H.; Sugiono, E. J. Prakt. Chem. 1999, 341, 358.
(27) Schwab, P.; France, M. B.; Ziller, J. W.; Grubbs, R. H.
Angew. Chem., Int. Ed. Engl. 1995, 34, 2039.
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(b) Garmatter, J.; Siegrist, A. E. Helv. Chim. Acta 1974, 57,
945.
Acknowledgement
Financial support from the Deutsche Forschungsgemeinschaft and
Prof. Dr. H. Meier is gratefully acknowledged.
Synthesis 2001, No. 6, 893–896 ISSN 0039-7881 © Thieme Stuttgart · New York