Synthesis of aryl-terminated polyenaldehydes and polyenetriethoxysilanes for preparation of self-assembled monolayers on silicon surfaces

Article abstract of DOI:10.1055/s-2001-15224

The synthesis of αω-terminally functionalized polyenes with arenes or hetarenes at one end and either an aldehyde or a triethoxysilyl function at the other end, capable of reacting with H-terminated or oxidized silicon surfaces, is described. Analogous to known Wittig reactions, polyenedialdehydes 1 and 3, the latter derived from 1 and phosphonium chloride 2 in a twofold Wittig olefination, were converted with phosphonium bromides 4 to give the (all-E)-arylpolyenaldehydes 5 and 6. A terminal alkyl chain was introduced in dialdehydes 1a and 3a by reaction with P,P-didecyldibenzophospholium bromide 8, resulting in polyenals 9. Wittig olefination of 5c and 9a with phosphonium chloride 2 afforded the (2-thienyl)tridecahexaenal 7 and the docosahexaenal 10. With respect to monolayer formation on oxidized Si(100) surfaces, (9-anthryl)- and (2-thienyl)-ω-functionalized polyenetriethoxysilanes 16 and 17 were prepared in a reaction sequence involving the introduction of a terminal triple bond with [3-(trimethylsilyl)prop-2-ynyl]triphenylphosphonium bromide (11), desilylation of the resulting arylpolyeninetrimethylsilanes 12, 13 with Bu₄NF·3H₂O, and subsequent hydrosilylation of the arylpolyenines 14, 15 using triethoxysilane under dichlorocyclooctadienylplatinum(II) catalysis.

Full text of DOI:10.1055/s-2001-15224

1368
PAPER
Synthesis of Aryl-Terminated Polyenaldehydes and Polyenetriethoxysilanes
for Preparation of Self-Assembled Monolayers on Silicon Surfaces
Synthesis of
P
r
olyenald
a
ehydes
a
nd
n
Polyenetriet
z
hoxysilane
s
Effenberger,* Markus Wezstein1
Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
Fax +49(711)6854269; E-mail: franz.effenberger@po.uni-stuttgart.de
Received 12 January 2001; revised 8 March 2001
the molecular building blocks to existing information sys-
Abstract: The synthesis of , -terminally functionalized polyenes
with arenes or hetarenes at one end and either an aldehyde or a tri-
ethoxysilyl function at the other end, capable of reacting with H-ter-
minated or oxidized silicon surfaces, is described. Analogous to
tems (e.g., microelectronic silicon components). An-
thracene-polyene pyridinium compounds have been
investigated first with respect to such kind of ordering of
known Wittig reactions, polyenedialdehydes 1 and 3, the latter de- single molecules.11,12 As amphiphiles these compounds
rived from 1 and phosphonium chloride 2 in a twofold Wittig olefi-
nation, were converted with phosphonium bromides 4 to give the
are able to form ordered monolayers on the water/air sur-
face which are transferable onto solid supports (e.g. glass)
(all-E)-arylpolyenaldehydes 5 and 6. A terminal alkyl chain was in-
by the Langmuir–Blodgett technique. The labile bonding
troduced in dialdehydes 1a and 3a by reaction with P,P-dide-
of these functionalized monolayers to the solid support is
cyldibenzophospholium bromide 8, resulting in polyenals 9. Wittig
a crucial disadvantage for possible applications of LB
films in “molecular electronics . We have therefore fo-
cused our investigations to the Self-Assembly technique
as second method to form ordered monolayers (SAMs) on
solid substrates.13 In the last few years the formation of
SAMs of alkanethiols on gold and of trichloro- and tri-
alkoxysilanes on oxidized silicon surfaces has been inves-
tigated intensively.14 By the photoinduced reaction of
long-chain aldehydes with hydrogen-terminated Si(111)
surfaces15 a procedure was developed to prepare well-or-
dered monolayers on oxide-free silicon surfaces, which
might have some technological potential in microelec-
tronic applications.
olefination of 5c and 9a with phosphonium chloride 2 afforded the
(2-thienyl)tridecahexaenal 7 and the docosahexaenal 10. With re-
spect to monolayer formation on oxidized Si(100) surfaces, (9-an-
thryl)- and (2-thienyl)- -functionalized polyenetriethoxysilanes 16
and 17 were prepared in a reaction sequence involving the introduc-
tion of a terminal triple bond with [3-(trimethylsilyl)prop-2-
ynyl]triphenylphosphonium bromide (11), desilylation of the re-
sulting arylpolyeninetrimethylsilanes 12, 13 with Bu4NF 3H2O, and
subsequent hydrosilylation of the arylpolyenines 14, 15 using tri-
ethoxysilane under dichlorocyclooctadienylplatinum(II) catalysis.
Key words: aldehydes, electron transfer, hydrosilylations, Wittig
reactions
In donor-acceptor-substituted conjugated polyenes and In the present publication we report on the synthesis of
oligothiophenes a quantitative energy transfer from the conjugated polyenes bearing at the one end an excitable
photoexcited donor, for example anthracene, to the accep- donor or acceptor and at the other end either a trialkoxy-
tor, for example tetraphenyl porphyrin, could be proved silyl group for linkage to oxidized silicon or an aldehyde
by fluorescence spectroscopy.2–6 Replacement of the por- function for linkage to H-terminated Si(111) surfaces.
phyrin in these supermolecules by stronger electron ac- Analogous to LB films,12 alkyl groups were incorporated
ceptors such as fullerene, pyridines or pyridinium in the polyene chain to improve the flexibility of the con-
moieties, respectively, enables an uni-directed intramo- jugated polyenes for optimizing the monolayer formation.
lecular electron transfer from the photoexcited anthracene An electron transfer through a SAM via conjugated -sys-
donor to the respective acceptor.7–9 In contrast to the ener- tems has recently been demonstrated by scanning tunnel-
gy transfer mentioned above, the electron transfer in these ing microscopy (STM) investigations of SAMs on gold
conjugated -systems can already be interrupted by a me- surfaces.16
thylene group as saturated spacer. This offers the possibil-
Dialdehydes are well known as starting materials in the
ity of incorporating, for example, photochemically
synthesis of polyenals.11 While crocetin dialdehyde (3a)
switchable organic molecules10 in donor-acceptor substi-
has already been used successfully, 2,15-dimethyl-6,11-
diethylheptaenedial 3b was prepared for the first time as
outlined in Scheme 1.
tuted conjugated -systems in order to realize suitable
components for electronic devices on a molecular level.
Any application of the described isolated molecules as
components in “molecular electronics , however, re-
quires the formation of supramolecular structures, for ex-
ample well-ordered monomolecular layers and bonding of
Prior to use, the starting dialdehyde 1b11,17 was purified by
filtration on silica gel and subsequently irradiated at 360
nm for 16–18 h in the presence of catalytic amounts of I2
to isomerize the cis-isomer to the all-trans compound 1b.
Recrystallization from MeOH finally gave isomerically
pure (all-E)-1b. In a twofold Wittig olefination analogous
Synthesis 2001, No. 9, 29 06 2001. Article Identifier:
1437-210X,E;2001,0,09,1368,1376,ftx,en;T00701SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
to a known method18 1b was reacted with the phosphoni-
um chloride 211,18 to give the hexadecaheptaenedial 3b.
ISSN 0039-7881

PAPER
Synthesis of Polyenaldehydes and Polyenetriethoxysilanes
1369
Scheme 1
After chromatographic purification, however, 3b was ob-
tained as an isomeric mixture with 68% cis product re-
ferred to the newly formed double bonds. After irradiation
in CH2Cl2 at 360 nm for 16 h with I2 as catalyst and recrys-
tallization from toluene–MeOH, (all-E)-3b was isolated
in 46% yield.
The preparation of the aryl-terminated polyenaldehydes 5,
6 by reaction of dialdehydes 1 and 3 with phosphonium
bromides 4a,11 and 4b–d, based on literature procedures,
is shown in Scheme 2.
(2-Thienyl)phosphonium salt 4b was obtained by reacting
freshly distilled 2-bromomethylthiophene19 with triphe-
nylphosphine in anhydrous THF under inert gas atmo-
sphere. After 18 hours reaction time, analytically pure 4b
was obtained in 88% yield.
Scheme 2
The preparation of the bipyridine-derived phosphonium
salts 4c and 4d started from 4-methyl20 and 4,4’-dimethyl-
2,2’-bipyridine,21 which were first brominated with
N-bromosuccinimide (NBS) in CCl4.22 The resulting bro-
mides tend to decompose and were reacted without further
purification with triphenylphosphine in THF under inert
atmosphere to give the products 4c and 4d in 38% and
36% yield, respectively.
hydes 1 and 3. In case of the (2-thienyl)polyenaldehydes
5b,c and 6b,c an excess of phosphonium bromide 4b
based on BuLi was applied in order to avoid metalation of
thiophene in 4 position (Table 1). As already published,23
also in the Wittig reaction of 1 and 3 with bromide 4b the
twofold terminally substituted dithienylpolyenes 5’b,c
According to the published procedure for (9-anthryl)poly- and 6’b,c were formed as byproducts (Scheme 2), which
enals 5a, 6a,11 the aryl-functionalized polyenals 5b,c and could readily be separated by chromatography. The crude
6b–e were prepared via Wittig olefination. A solution of products were recrystallized from toluene-MeOH, giving
the respective ylide, formed from phosphonium bromides the arylpolyenaldehydes 5b,c and 6b,c in 16–78% yield
4b–d by treatment with a base, was added to the dialde- with >99% all-E (Table 1).
Table 1 Preparation of (2-Thienyl)polyenaldehydes 5b,c and 6b,c from Dialdehydes 1,3 and Bromide 4b
Starting Materials
Prod-
uct
Yield
(%)
all-E
mp
(°C)
Appearance
(%)a
1, 3
1a
(mmol)
4b (mmol)
14.2
BuLi (mmol)
13.4
11.2
6.9
19.2
12.2
8.0
5b
5c
6b
6c
31
78
31
16
>99
91
112
–
yellow solid
red oil
1b
3a
12.2
8.1
>99
>99
202
172
violet solid
violet solid
3b
3.3
3.6
3.5
a Assignment by coupling constant 3JH,H in 1H NMR spectra and chemical shift.
Synthesis 2001, No. 9, 1368–1376 ISSN 0039-7881 © Thieme Stuttgart · New York

1370
F. Effenberger, M. Wezstein
PAPER
In the preparation of the bipyridinepolyenals 6d and 6e
BuLi was replaced by lithium methoxide as base in order
to exclude possible butylation of the pyridine ring. The
base was added at room temperature to an excess of alde-
hyde 3b and the respective bipyridyl phosphonium salts
4c and 4d. After chromatography and recrystallization,
products 6d and 6e were isolated in 24% and 45% yield,
respectively, with >95% all-E.
Following the preparation of 3b, the elongation from 4 to
6 conjugated double bonds was achieved: reacting 9-(2-
thienyl)-2,7-diethylnonatetraenal 5c and phosphonium
chloride 2 with LiOMe gave (2-thienyl)-6,11-diethyl-2-
methyltridecahexaenal 7 which was obtained in analyti-
cally pure form in 28% yield (>99% all-E) after chromato-
graphic purification and recrystallization from toluene-
MeOH.
The isomeric purity of the products was determined by
HPLC23,24 and NMR spectroscopy,25 respectively, and the
assignment followed from comparison with literature da-
ta. The all-E isomers of arylpolyenaldehydes are known to
show the longest retention time in the chromatography.11
1
The structural assignment in H NMR spectroscopy is
3
based on the JH,H coupling constants: J = 14–17 Hz for
trans olefinic protons and J = 9–11 Hz for cis pro-
tons.11,23,24 Moreover, the Z-configuration leads to a
chemical shift of 0.3–0.9 ppm for the protons in adjacent
position to the Z-configurated double bond.11,25 Addition-
ally, UV/Vis spectroscopy supported the assignments.26
Scheme 3
The formation of monolayers on Si(111)-H surfaces can
be detected by FTIR spectroscopy. In order to increase the
intensity of the C-H vibration of the polyene chain in com-
bination with the decrease of melting points, compounds
9a,b and 10 with terminal alkyl chain were prepared
(Scheme 3).
The Wittig olefination of aldehydes by using phosphole
derivatives has already been described intensively.27,28
Since phosphole-derived reagents are known to be consis-
tently E-selective,28 P,P-didecyldibenzophospholium
bromide (8) was synthesized as olefination agent accord-
ing to
a
literature procedure27 by reacting P-
phenyldibenzophosphole27 with bromodecane in the pres-
ence of lithium. The primarily formed P-decyldibenzo-
phosphole, which could be isolated after bulb-to-bulb
distillation in 83% yield, was heated in bromodecane at
130°C for 3 hours to give the phospholium bromide 8.
Compound 8 was purified by filtration through silica gel
and recrystallization from diglyme. By using lithium
bis(trimethylsilyl)amide [LiN(SiMe3)2] as base phosphole
derivative 8 in diglyme was converted to the correspond-
ing ylide, which was added to a solution of the respective
dialdehyde 1a and 3a in diglyme. While 1a could be react-
ed at room temperature, dissolving of 3a required higher
temperature (60°C) due to its reduced solubility. After
heating at 120°C for 3 hours to induce decomposition of
the intermediate oxaphosphetanes,28 nonylpolyenalde-
hydes 9a and 9b were obtained in 33% and 11% yield, re-
spectively, with approximately 94% all-E.
Scheme 4
Synthesis 2001, No. 9, 1368–1376 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Synthesis of Polyenaldehydes and Polyenetriethoxysilanes
1371
Table 2 Preparation of Arylpolyeninetrimethylsilanes 12 and 13
from Polyenaldehydes 5,6
The polyene chain of 9a was extended by two additional
double bonds by reacting with the acetal phosphonium
salt 2. Under the reaction conditions described for 3b tri-
methyldocosahexaenal 10 was isolated after chromatogra-
phy on silica gel in 60% yield as an isomeric mixture
(58% all-E).
Starting Materials
Prod- Yield Mp
all-E
uct
(%)
(°C)
(%)
5, 6
11
BuLi
(mmol) (mmol) (mmol)
5a
5b
6a
6b
3.8
1.8
1.3
1.0
3.9
3.5
2.6
2.0
4.8
3.7
2.6
2.2
12a
12b
13a
13b
61
70
51
64
167
123
>99
>99
The formation of monolayers on oxidized Si(100) surfac-
es requires silyl functionalized polyenes. Therefore, as
outlined in Scheme 4, the triethoxysilyl terminated
arylpolyenes 16 and 17 were prepared (Scheme 4).
190–191 >99
188 >99
The arylpolyenaldehydes 5a, 5b and 6a, 6b were used as
starting material. Since the direct introduction of a termi-
nal triple bond with 2-propargyltriphenylphosphonium
bromide according to a known method29 was not success-
ful, the phosphonium bromide 11, which was prepared
analogously to a literature procedure,30 was applied for in-
troducing the terminal triple bond. Compound 11 was
converted with BuLi at –78°C to –40°C to the ylide,
which was added in the absence of light to a solution of
the respective aldehyde 5 or 6 in CH2Cl2. After 16 hours
reaction time, the arylpolyeninetrimethylsilanes 12 and 13
were obtained (Table 2).
anhydrous toluene or CH2Cl2 under inert gas atmosphere
at room temperature in the absence of light (Table 3). The
desired arylpolyenetriethoxysilanes 16 and 17 were puri-
fied by chromatography on silica gel with anhydrous
CH2Cl2. The isomeric ratios of the products were deter-
mined by NMR, giving >95% all-E percentage in all cas-
es.
Mps were determined on a Büchi SMP-20 apparatus and are uncor-
rected. Unless otherwise stated, 1H NMR spectra were recorded on
a Bruker AC 250 F (250 MHz) or a Bruker ARX 500 (500 MHz)
instrument with TMS as internal standard; signals with an asterisk
cannot be assigned unambiguously. UV/Vis spectra were recorded
on a Perkin Elmer Lambda 7 photospectrometer with quartz cuvette
(d = 1 cm). Preparative column chromatography was carried out on
columns packed with Al2O3 Alumina Woelm B super 1, basic
(Woelm Pharma) or with silica gel S (Riedel-de Haen, grain size:
0.032–0.063 mm). All reactions were carried out under argon in
flame-dried glassware. All solvents were purified and dried, and the
starting compounds were distilled or recrystallized and dried.
Chromatographic purification gave the silanes 12 and 13
as E/Z-isomeric mixtures with 81–85% all-E, which were
recrystallized to the isomerically pure all-E compounds.
Desilylation of 12 and 13 to arylpolyenines 14 and 15 was
performed
with
tetrabutylammonium
fluoride
(Bu4NF 3H2O)31 in THF. The results are summarized in
Table 3.
With the exception of the polyenine derivative 14a (92%
all-E) an all-E percentage of >95% was determined by
NMR for all compounds 14 and 15, which were character-
ized by mass spectrometry (Table 3) and, due to their in-
stability, were reacted as crude products without further
purification. Crude 14 and 15 were hydrosilylated using
an excess of triethoxysilane in presence of dichlorocy-
clooctadienylplatinum(II) (Cl2PtCOD)32 as a catalyst in
6,11-Diethyl-2,15-dimethylhexadeca-2,4,6,8,10,12,14-hepta-
enedial [(all-E)-3b]
To a suspension of Li (0.39 g, 56.2 mmol) in MeOH (100 mL) was
added CH2Cl2 (100 mL) followed by addition of a solution of 1b
(3.81 g, 19.8 mmol) in CH2Cl2 (100 mL) and a 1.03 M solution of 2
Table 3 Desilylation of Trimethylsilanes 12,13 to Arylpolyenines 14, 15 and their Hydrosilylation to Arylpolyenetriethoxysilanes 16, 17
Starting Materials Conditions Arylpolyenines 14, 15 Arylpolyenetriethoxysilanes 16,17
12,13
Bu4NF THF Time
(mmol) (mmol) (mL) (h)
Yield
(%)
MS (EI, 70 eV)
Formula Calcd/Found
Yield Mp
MS (EI, 70 eV)
Formula Calcd/Found
(%)a
(°C)
12a 1.2
12b 2.1
13a 0.5
13b 0.7
0.25
0.12
0.05
0.05
80
2
1
2
1
14a quant. C28H24 360.18764/
16a
16b
38
95
C34H40O3Si 524.27247/
524.27298b
360.18764b
c
d
100
40
14b 95
15a 91
15b 87
C18H18S 266.11292/
266.11315
29
33
29
-
C24H34O3SSi -
C38H36 492.3/492.3 17a
C28H30S 398.61/398.0 17b
280 (dec) C44H52O3Si 656.36857/
656.36902
80
280 (dec) C34H46O3SSi 562.293696/
562.294260
a Yield from the crude products.
b FAB-MS (NBA matrix).
c Yellow oil.
d Anal. Calcd: C, 66.93; H, 7.96; S, 7.44. Found: C, 66.82; H, 7.97; S, 7.42.
Synthesis 2001, No. 9, 1368–1376 ISSN 0039-7881 © Thieme Stuttgart · New York

1372
F. Effenberger, M. Wezstein
PAPER
in MeOH (65 mL, 66.9 mmol) dropwise over 4 h. After stirring for
12 h at r.t. (TLC control), the mixture was washed with H2O (200
mL), and the aqueous layer was extracted with CH2Cl2 (3 100
mL). The combined organic layers were dried (MgSO4), concentrat-
ed to ca. 50 mL and filtered through a SiO2 column with CH2Cl2.
Concentration and recrystallization from toluene-MeOH gave 3b as
a cis/trans isomeric mixture (determined by HPLC). In order to
isomerize the cis product, I2 (ca. 2 mg) was added to the solution of
isomeric 3b in CH2Cl2 (250 mL), and the mixture was irradiated at
360 nm (Camag-Universal TLC UV lamp fitted with a Philips 8 W
tube) for 12 h. I2 was removed with aq sat. Na2S2O3 solution (100
mL). Concentration and recrystallization from toluene-MeOH fi-
nally gave 2.97 g (46%) of (all-E)-3b as a violet solid; mp 176°C.
1H NMR (500 MHz, CDCl3): = 1.14 (t, 6 H, J = 7.6 Hz, CH2CH3),
1.91 (s, 6 H, CH3), 2.52 (q, 4 H, J = 7.6 Hz, CH2CH3), 6.40 (d, 2 H,
J = 7.9 Hz, H-7,10), 6.65 (d, 2 H, J = 15.0 Hz, H-5,12), 6.73–6.79
(m, 4 H, H-4,8,9,13), 6.94 (d, 2 H, J = 11.6 Hz, H-3,14), 9.47 (s, 2
H, CHO).
17.8 mmol) in 36% yield as a colorless solid with occluded THF;
mp 248°C (dec).
1H NMR (250 MHz, CDCl3): = 2.44 (s, 3 H, CH3), 5.68 (d, 2 H,
J = 15.5 Hz, CH2), 7.17 (dd, 1 H, J = 5.1, 0.7 Hz, H-5'), 7.29 (dd, 1
H, J = 5.1, 1.7 Hz, H-5), 7.52–7.91 (m, 15 H, phenyl H), 8.08 (s, 1
H, H-3), 8.18 (d, 1 H, J = 0.6 Hz, H-3'), 8.43 (d, 1 H, J = 5.1 Hz, H-
6'), 8.46 (d, 1 H, J = 5.1 Hz, H-6).
Arylpolyenaldehydes 5b,c and 6b,c; General Procedure
To a suspension of bromide 4b in THF (40–80 mL) was added a 1.6
M solution of BuLi in hexane by a syringe, and the mixture was
stirred for 2 h (Table 1). In order to remove the excess of BuLi,
CH2Cl2 or EtOH was added. After stirring for a further 30 min, the
ylide solution was transferred to the dropping funnel fitted to a sec-
ond flask via cannula, and added dropwise to a solution of 1a,b or
3a,b in CH2Cl2 (150–300 mL) over 30–60 min (Table 1). The mix-
ture was stirred at r.t. for 16 h, concentrated, and the residue was
taken up in CH2Cl2 and filtered through SiO2 with CH2Cl2 as eluent.
Chromatography on SiO2 with CH2Cl2 as eluent and recrystalliza-
tion from toluene–MeOH gave products 5b,c or 6b,c (Table 4).
Anal. Calcd for C22H28O2: C, 81.43; H, 8.70. Found: C, 81.37; H,
8.93.
Bipyridylpolyenaldehydes 6d,e; General Procedure
2-Thienylmethyltriphenylphosphonium Bromide (4b)
A solution of 2-bromomethylthiophene19 (11.05 g, 62.4 mmol) and
Ph3P (16.4 g, 62.7 mmol) in THF (60 mL) was stirred at r.t. for 16
h. The white precipitate was filtered off under inert gas, washed
with THF (3 20 mL) and dried under high vacuum; yield: 24.12 g
(88%).
1H NMR (500 MHz, CDCl3): = 5.72 (d, 2 H, J = 13.2 Hz, CH2),
6.82–6.86 (m, 1 H, thienyl H-5), 7.12–7.15 (m, 2 H, thienyl H-3,4),
7.63–7.67 (m, 6 H, phenyl H-2,6), 7.74–7.80 (m, 9 H, phenyl H-
3,4,5).
To a stirred mixture of bromide 4c or d in MeOH and 3a in CH2Cl2
at r.t. was added dropwise over 1 h a ca. 1 M solution of LiOMe,
prepared from MeOH and BuLi. After stirring for 16 h, the mixture
was washed with H2O, and the aqueous layer was extracted with
CH2Cl2. The combined organic layers were dried (MgSO4) and con-
centrated. The residue was filtered through SiO2 with CH2Cl2 as
eluent to remove unreacted 3a. Chromatography on SiO2 with
CHCl3 as eluent and recrystallization from toluene-MeOH or EtOH
gave products 6d,e.
17-(2,2'-Bipyridyl-4-yl)-2,6,11,15-tetramethylheptadeca-
2,4,6,8,10,12,14,16-octaenal (6d)
Anal. Calcd for C23H20BrPS: C, 62.88; H, 4.59; Br, 18.18; P, 7.05;
S, 7.30. Found: C, 62.79; H, 4.56; Br, 18.21; P, 7.07; S, 7.34.
Compound 6d was obtained from 4c (0.56 g, 1.07 mmol) in MeOH
(20 mL), 3a (0.56 g, 1.88 mmol) in CH2Cl2 (40 mL) and LiOMe pre-
pared from a 1.6 M solution of BuLi in hexane (0.75 mL, 1.20
mmol) and MeOH (20 mL) in 24% yield as a violet solid (>95% all-
E); mp 205°C (EtOH).
1H NMR (500 MHz, CDCl3): = 1.90, 2.02, 2.03, 2.07 (each s, 3 H,
2,6,11,15-CH3), 6.35 (d, 1 H, J = 11.6 Hz, H-14), 6.45 (d, 3 H,
J = 14.5, 10.7 Hz, H-7,10,12), 6.48 (d, 1 H, J = 15.9 Hz, H-16), 6.68
(dd, 1 H, J = 14.8, 10.1 Hz, H-4), 6.70–6.75 (m, 2 H, H-8,9), 6.74
(d, 1 H, J = 14.4 Hz, H-5), 6.77 (dd, 1 H, J = 14.2, 11.1 Hz, H-13),
6.94 (d, 1 H, J = 10.5 Hz, H-3), 7.20 (d, 1 H, J = 15.9 Hz, H-17), 7.30
(dd, 1 H, J = 5.1, 1.6 Hz, bipyridyl H-5), 7.33 (ddd, 1 H, J = 7.4, 4.7,
0.9 Hz, bipyridyl H-5'), 7.83 (dt, 1 H, J = 7.6, 1.0 Hz, bipyridyl H-
4'), 8.41 (d, 1 H, J = 7.9 Hz, bipyridyl H-3'), 8.43 (d, 1 H, J = 0.7 Hz,
bipyridyl H-3), 8.58 (d, 1 H, J = 5.1 Hz, bipyridyl H-6), 8.70 (dd, 1
H, J = 4.7, 1.0 Hz, bipyridyl H-6'), 9.45 (s, 1 H, CHO).
2,2’-Bipyridyl-4-methylphosphonium Bromides 4c,d; General
Procedure
Following a published method,22 a suspension of the respective bi-
pyridine and NBS in CCl4 (150 mL) was stirred at r.t. under argon
for 30 min. After addition of dibenzoyl peroxide with 25% H2O
(1.0–1.1 mmol), the mixture was refluxed for 6 h. Precipitated suc-
cinimide was filtered off, the filtrate was concentrated, and the res-
idue was filtered through SiO2 (40 g) with CHCl3 as eluent. The
eluate containing the respective bromomethylbipyridine was con-
centrated, taken up in THF (30 mL) and added by syringe to a solu-
tion of Ph3P in THF (40 mL). The mixture was stirred at r.t. for 12
h. The precipitated product was filtered off under inert gas, washed
with THF and dried under high vacuum. Further product precipitat-
ed after 2 d from the filtrate.
(4-Methyl-2,2’-bipyridyl-4-yl)triphenylphosphonium Bromide (4c)
Compound 4c was obtained from 4-methyl-2,2'-bipyridine20,22
(2.83 g, 16.6 mmol), NBS (3.28 g, 18.4 mmol), and Ph3P (4.19 g,
15.9 mmol) in 38% yield as a light brown solid with occluded THF;
mp 230°C (dec).
UV (CH2Cl2):
(111700).
( ) = 287 (28000), 474 (122026), 502 nm
max
Anal. Calcd for C31H32N2O: C, 83.00; H, 7.19; N, 6.25. Found: C,
82.65; H, 7.29; N, 6.18.
1H NMR (250 MHz, CDCl3): = 5.71 (d, 2 H, J = 15.6 Hz, CH2),
7.28 (m, 1 H, H-5'), 7.47 (dd, 1 H, J = 7.5, 2.9 Hz, H-5), 7.52–7.88
(m, 16 H, H-4', phenyl H), 8.04 (s, 1 H, H-3), 8.27 (d, 1 H, J = 7.9
Hz, H-3'), 8.44 (d, 1 H, J = 4.9 Hz, H-6), 8.56 (d, 1 H, J = 4.9 Hz, H-
6').
17-(4'-Methyl-2,2'-bipyridyl-4-yl)-2,6,11,15-tetramethylhepta-
deca-2,4,6,8,10,12,14,16-octaenal (6e)
Compound 6e was obtained from 4d (0.36 g, 0.68 mmol) in MeOH
(20 mL), 3a (0.28 g, 0.96 mmol) in CH2Cl2 (40 mL), and LiOMe
prepared from a 1.6 M solution of BuLi in hexane (0.7 mL, 1.12
mmol) and MeOH (20 mL) in 45% yield as a violet solid (>95% all-
E); mp 190°C (toluene–MeOH, 1:1).
(4,4'-Dimethyl-2,2’-bipyridyl-4-yl)triphenylphosphonium
Bromide (4d)
Compound 4d was obtained from 4,4'-dimethyl-2,2'-bipyridine21
(3.15 g, 17.1 mmol), NBS (3.18 g, 17.9 mmol), and Ph3P (4.66 g,
Synthesis 2001, No. 9, 1368–1376 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Synthesis of Polyenaldehydes and Polyenetriethoxysilanes
1373
Table 4 Spectroscopic and UV/Vis Data of Compounds 5, 6 and 12–17
Producta
1H NMR (500 MHz, CDCl3/TMS), , J (Hz)
UV/Vis (CH2Cl2), 25°C
max (nm), [ (L mol–1
cm–1)]
5b
1.89 (s, 3 H, 2-CH3), 2.05 (s, 3 H, 7-CH3), 6.37 (d, 1 H, J = 11.7, H-6), 6.70 (dd, 1 H, J = 14.3, 297 (8500), 402 (43500)
11.5, H-4), 6.71 (d, 1 H, J = 15.7, H-8), 6.87 (d, 1 H, J = 15.7, H-9), 6.96 (d, 1 H, J = 11.7, H-
3), 6.99–7.01 (m, 1 H, thienyl H-4), 7.03–7.06 (m, 2 H, H-5, thienyl H-3), 7.21 (d, 1 H, J = 5.0,
thienyl H-5), 9.46 (s, 1 H, CHO)
5cb
1.04 (t, 3 H, J = 7.5, 7-CH2CH3), 1.16 (t, 3 H, J = 7.5, 2-CH2CH3), 2.41 (q, 2 H, J = 7.5, 7-
CH2CH3), 2.55 (q, 2 H, J = 7.5, 2-CH2CH3), 6.23 [d, 1 H, J = 11.8, H-3 (cis C4-C5)], 6.31 [d, 1
H, J = 11.8, H-3 (trans C4-C5)], 6.61 (d, 1 H, J = 15.8, H-8), 6.72 (dd, 1 H, J = 14.2, 11.7, H-
5), 6.87–6.96 (m, 2 H, H-4,6), 6.99–7.05 (m, 3 H, H-9, thienyl H-3,4), 7.20–7.24 (m, 1 H, thie-
nyl H-5), 9.43 (s, 1 H, CHO)
299 (17500), 403 (46000)
6bb
6c
1.90 (s, 3 H, 2-CH3), 2.01 (s, 9 H, 6,11,15-CH3), 6.28–6.47 (m, 4 H, H-7,10,12,14), 6.60–6.77 299 (17500), 367 (22000),
(m, 7 H, H-3,4,5,8,9,13,16), 6.92–6.99 (m, 3 H, H-17, thienyl H-3,4), 7.15 (dd, 1 H, J = 4.4,
475 (101100)
1.7, thienyl H-5), 9.45 (s, 1 H, CHO)
1.12 (t, 3 H, J = 7.5, 6-CH2CH3), 1.13 (t, 3 H, J = 7.5, 11-CH2CH3), 1.90 (d, 3 H, J = 0.7, 2-CH3), 299 (15900), 369 (10200),
2.01 (s, 3 H, 15-CH3), 2.49 (q, 2 H, J = 7.5, 6-CH2CH3), 2.51 (q, 2 H, J = 7.5, 11-CH2CH3), 6.24 482 (83800)
(d, 1 H, J = 11.8, H-7), 6.31 (d, 1 H, J = 15.4, H-12), 6.31 (d, 1 H, J = 10.1, H-10), 6.39 (d, 1 H,
J = 11.7, H-14), 6.61–6.77 (m, 7 H, H-3,4,5,8,9,13,16), 6.92–6.99 (m, 3 H, H-17, thienyl H-
3,4), 7.15 (dd, 1 H, J = 4.4, 1.1, thienyl H-5), 9.45 (s, 1 H, CHO)
12ab
0.20 [s, 9 H, cis Si(CH3)3], 0.22 [s, 9 H, trans Si(CH3)3], 1.85 (s, 3 H, 5-CH3), 2.26 (s, 3 H, 10- 248 (70300), 258 (63600),
CH3), 5.44 (d, 1 H, J = 12.0, H-3 cis), 5.65 (d, 1 H, J = 15.9, H-3 trans), 6.24 (d, 1 H, J = 10.8, 355 (37800), 372 (57100),
H-9), 6.33 (d, 1 H, J = 10.8, H-6), 6.56–6.78 (m, 4 H, H-4,7,8,11), 7.43–7.48 (m, 5 H, H-12,
anthryl H-2,3,6,7), 7.94–8.00 (m, 2 H, anthryl H-4,5), 8.26–8.30 (m, 2 H, anthryl H-1,8), 8.34
(s, 1 H, anthryl H-10)
414 (49000)
12bb
13a
0.20 [s, 9 H, Si(CH3)3], 1.86 (s, 3 H, 5-CH3), 1.98 (s, 3 H, 10-CH3), 5.42 (d, 1 H, J = 11.5, H-3 310 (4100), 390 (33600),
cis), 5.64 (d, 1 H, J = 15.8, H-3 trans), 6.25 (d, 1 H, J = 11.4, H-6), 6.31 (d, 1 H, J = 11.5, H-9), 411 (52400), 437 (49000)
6.39 (dd, 1 H, J = 14.4, 11.5, H-7), 6.45–6.56 (m, 4 H, H-4,8,11,12), 6.75–6.79 (m, 2 H, thienyl
H-3,4), 6.94 (d, 1 H, J = 4.9, thienyl H-5)
0.19 [s, 9 H, cis Si(CH3)3], 0.20 [s, 9 H, trans Si(CH3)3], 1.86 (s, 3 H, 5-CH3), 1.95 (s, 3 H, 9- 255 (92300), 346 (21200),
CH3), 2.02 (s, 3 H, 14-CH3), 2.29 (s, 3 H, 18-CH3), 5.41 (d, 1 H, J = 11.9, H-3 cis), 5.65 (d, 1
H, J = 15.9, H-3 trans), 6.23 (d, 1 H, J = 11.4, H-6), 6.28 (d, 1 H, J = 9.5, H-10), 6.30 (d, 1 H,
J = 7.8, H-13), 6.33 (d, 1 H, J = 11.5, H-17), 6.41 (d, 1 H, J = 14.9, H-8), 6.42 (d, 1 H, J = 14.8,
H-15), 6.57 (dd, 1 H, J = 14.8, 11.5, H-7), 6.60–6.67 (m, 2 H, H-11,12), 6.72 (d, 1 H, J = 16.1,
H-19), 6.73 (d, 1 H, J = 15.8, H-4), 6.76 (dd, 1 H, J = 14.8, 11.5, H-16), 7.41 (d, 1 H, J = 16.2,
H-20), 7.44–7.47 (m, 4 H, anthryl H-2,3,6,7), 7.97–8.00 (m, 2 H, anthryl H-4,5), 8.29–8.31 (m,
2 H, anthryl H-1,8), 8.35 (s, 1 H, anthryl H-10)
476 (109200)
13bb
14a
14b
0.20 [s, 9 H, Si(CH3)3], 1.88 (s, 3 H, 5-CH3), 1.96 (s, 3 H, 9-CH3), 1.98 (s, 3 H, 14-CH3), 2.00 310 (18100), 375 (6900),
(s, 3 H, 18-CH3), 5.40 (d, 1 H, J = 12.0, H-3 cis), 5.60 (d, 1 H, J = 15.9, H-3 trans), 6.24 (d, 1 457 (64600), 484 (94200),
H, J = 11.5, H-6), 6.27 (d, 1 H, J = 9.5, H-10), 6.30 (d, 1 H, J = 7.8, H-13), 6.39 (d, 1 H, J = 14.9, 517 (85100)
H-8), 6.41 (d, 1 H, J = 14.8, H-15), 6.58 (dd, 1 H, J = 14.8, 11.2, H-7), 6.62–6.76 (m, 7 H, H-
4,11,12,16,17,19,20), 6.94–6.97 (m, 2 H, thienyl H-3,4), 7.14 (dd, 1 H, J = 4.0, 2.0, thienyl H-
5)
1.88 (s, 3 H, 5-CH3), 2.28 (s, 3 H, 10-CH3), 3.09 (d, 1 H, J = 2.1, H-1 (C3-C4 trans)], 3.29 [d, 249 (978000), 258
1 H, J = 2.8, H-1 (C3-C4 cis)], 5.41 (dd, 1 H, J = 12.0, 2.8, H-3 cis), 5.60 (dd, 1 H, J = 15.9, 2.0, (113800), 351 (40600), 369
H-3 trans), 6.31 (d, 1 H, J = 11.5, H-6), 6.35 (d, 1 H, J = 11.7, H-9), 6.63 (dd, 1 H, J = 14.3,
11.6, H-7), 6.72 (d, 1 H, J = 16.2, H-11), 6.78 (d, 1 H, J = 14.0, H-4), 6.81 (dd, 1 H, J = 14.1,
11.9, H-8), 7.43–7.48 (m, 5 H, H-12, anthryl H-2,3,6,7), 7.98–8.00 (m, 2 H, anthryl H-4,5),
8.28–8.32 (m, 2 H, anthryl H-1,8), 8.36 (s, 1 H, anthryl H-10)
(55000), 409 (47200)
1.88 (s, 3 H, 5-CH3), 1.99 (s, 3 H, 10-CH3), 3.08 (d, 1 H, J = 2.3, H-1), 5.59 (d, 1 H, J = 15.8,
308 (3800), 387 (23800),
H-3), 6.27 (d, 1 H, J = 11.4, H-6), 6.31 (d, 1 H, J = 11.5, H-9), 6.59 (dd, 1 H, J = 14.4, 11.5, H- 407 (36700), 432 (34100)
7), 6.67–6.77 (m, 4 H, H-4,8,11,12), 6.96–6.99 (m, 2 H, thienyl H-3,4), 7.15 (d, 1 H, J = 4.8,
thienyl H-5)
Synthesis 2001, No. 9, 1368–1376 ISSN 0039-7881 © Thieme Stuttgart · New York

1374
F. Effenberger, M. Wezstein
PAPER
Table 4 Spectroscopic and UV/Vis Data of Compounds 5, 6 and 12–17 (continued)
Producta
1H NMR (500 MHz, CDCl3/TMS), , J (Hz)
UV/Vis (CH2Cl2), 25°C
max (nm), [ (L mol–1
cm–1)]
15a
1.90 (s, 3 H, 5-CH3), 1.96 (s, 3 H, 9-CH3), 2.03 (s, 3 H, 14-CH3), 2.30 (s, 3 H, 18-CH3), 3.07
[d, 1 H, J = 2.4, H-1 (C3–C4 trans)], 3.28 [d, 1 H, J = 2.8, H-1 (C3–C4 cis)], 5.38 (dd, 1 H,
J = 11.9, 2.4, H-3 cis), 5.56 (dd, 1 H, J = 15.9, 2.2, H-3 trans), 6.25 (d, 1 H, J = 11.4, H-6), 6.29
(d, 1 H, J = 9.5, H-10), 6.31 (d, 1 H, J = 9.0, H-13), 6.34 (d, 1 H, J = 10.9, H-17), 6.44 (d, 2 H,
J = 14.9, H-8,15), 6.58 (dd, 1 H, J = 14.8, 11.4, H-7), 6.62–6.69 (m, 2 H, H-11,12), 6.74 (d, 1
H, J = 16.7, H-19), 6.75 (d, 1 H, J = 16.7, H-4), 6.77 (dd, 1 H, J = 14.4, 11.4, H-16), 7.42 (d, 1
H, J = 16.2, H-20), 7.44–7.48 (m, 4 H, anthryl H-2,3,6,7), 7.99–8.01 (m, 2 H, anthryl H-4,5),
8.30–8.32 (m, 2 H, anthryl H-1,8), 8.37 (s, 1 H, anthryl H-10)
255 (79800), 346 (9200),
351 (9500), 474 (110400)
15bb
16a
1.90 (s, 3 H, 5-CH3), 1.97 (s, 3 H, 9-CH3), 1.99 (s, 3 H, 14-CH3), 2.01 (s, 3 H, 18-CH3), 3.07
(d, 1 H, J = 2.4, H-1), 5.57 (dd, 1 H, J = 15.9, 2.4, H-3), 6.26 (d, 2 H, J = 12.3, H-6,17), 6.31 (d, 455 (82700), 478 (102700),
2 H, J = 12.3, 11.6, H-10,13), 6.40 (d, 1 H, J = 14.8, H-8), 6.43 (d, 1 H, J = 14.8, H-15), 6.59
(dd, 1 H, J = 14.8, 11.6, H-7), 6.62–6.80 (m, 6 H, H-4,11,12,16,19,20), 6.94–6.97 (m, 2 H, thie-
nyl H-3,4), 7.14 (dd, 1 H, J = 4.1, 2.0, thienyl H-5)
306 (20600), 372 (16800),
511 (81300)
1.25 (t, 9 H, J = 7.0, OCH2CH3), 1.92 (s, 3 H, 5-CH3), 2.28 (s, 3 H, 10-CH3), 3.85 (q, 6 H,
J = 7.0, OCH2CH3), 5.62 (d, 1 H, J = 18.4, H-1), 6.31–6.36 (m, 3 H, H-3,6,9), 6.45 (d, 1 H,
250 (70900), 258 (88600),
359 (29300), 375 (40500),
J = 15.2, H-4), 6.65 (dd, 1 H, J = 14.3, 11.6, H-8), 6.72 (d, 1 H, J = 16.2, H-11), 6.76 (dd, 1 H, 411 (36800)
J = 14.3, 11.6, H-7), 6.91 (dd, 1 H, J = 18.4, 10.2, H-2), 7.43 (d, 1 H, J = 16.0, H-12), 7.45–7.49
(m, 4 H, anthryl H-2,3,6,7), 7.98–8.00 (m, 2 H, anthryl H-4,5), 8.28–8.31 (m, 2 H, anthryl H-
1,8), 8.36 (s, 1 H, anthryl H-10)
16b
17a
1.25 (t, 9 H, J = 7.0, OCH2CH3), 1.92 (s, 3 H, 5-CH3), 1.99 (s, 3 H, 10-CH3), 3.84 (q, 6 H,
J = 7.0, OCH2CH3), 5.59 (d, 1 H, J = 18.3, H-1), 6.29 (d, 1 H, J = 10.9, H-6), 6.32 (d, 1 H,
J = 11.5, H-9), 6.33 (dd, 1 H, J = 15.0, 10.5, H-3), 6.43 (d, 1 H, J = 15.2, H-4), 6.60–6.68 (m, 2
H, H-7,8), 6.71 (d, 2 H, J = 7.5, H-11,12), 6.91 (dd, 1 H, J = 18.3, 10.0, H-2), 6.96–6.99 (m, 2
H, thienyl H-3,4), 7.15 (d, 1 H, J = 4.8, thienyl H-5)
395 (39800), 415 (47900),
441 (38600)
1.25 (t, 9 H, J = 7.0, OCH2CH3), 1.94 (s, 3 H, 5-CH3), 1.97 (s, 3 H, 9-CH3), 2.03 (s, 3 H, 14-
255 (61600), 353 (10400),
CH3), 2.29 (s, 3 H, 18-CH3), 3.85 (q, 6 H, J = 7.0, OCH2CH3), 5.58 (d, 1 H, J = 18.4, H-1), 6.25– 479 (90700)
6.35 (m, 5 H, H-3,6,10,13,17), 6.40 (d, 1 H, J = 14.6, H-4), 6.43 (d, 1 H, J = 14.2, H-8), 6.44 (d,
1 H, J = 15.4, H-15), 6.59–6.70 (m, 3 H, H-11,12,16), 6.73 (d, 1 H, J = 16.2, H-19), 6.76 (dd, 1
H, J = 15.0, 11.5, H-7), 6.92 (dd, 1 H, J = 18.3, 10.2, H-2), 7.41 (d, 1 H, J = 16.2, H-20), 7.44–
7.48 (m, 4 H, anthryl H-2,3,6,7), 7.98–8.01 (m, 2 H, anthryl H-4,5), 8.30–8.32 (m, 2 H, anthryl
H-1,8), 8.36 (s, 1 H, anthryl H-10)
17bb
1.24 (t, 9 H, J = 7.0, OCH2CH3), 1.94 (s, 3 H, 5-CH3), 1.97 (s, 3 H, 9-CH3), 1.98 (s, 3 H, 14-
CH3), 2.01 (s, 3 H, 18-CH3), 3.82 (q, 6 H, J = 7.0, OCH2CH3), 5.58 (d, 1 H, J = 18.3, H-1), 6.26– 459 (91000), 484 (112500),
6.34 (m, 5 H, H-3,6,10,13,17), 6.41 (d, 2 H, J = 15.0, H-4,8), 6.43 (d, 1 H, J = 15.4, H-15), 6.60– 516 (83000)
6.69 (m, 4 H, H-7,11,12,16), 6.71 (s, 2 H, H-19,20), 6.92 (dd, 1 H, J = 18.3, 10.2, H-2), 6.96–
6.98 (m, 2 H, thienyl H-3,4), 7.14 (dd, 1 H, J = 4.5, 1.1, thienyl H-5)
311 (23800), 377 (22700),
a Satisfactory microanalysis or mass spectrum obtained for each compound.
b Recorded at 250 MHz.
1H NMR (500 MHz, CDCl3): = 1.90, 2.00, 2.01, 2.05 (each s, 3 H,
2,6,11,15-CH3), 2.44 (s, 3 H, CH3), 6.35 (d, 1 H, J = 11.4 Hz, H-14),
6.44 (d, 2 H, J = 11.2 Hz, H-7,10), 6.46 (d, 1 H, J = 14.5 Hz, H-12),
6.59 (d, 1 H, J = 15.9 Hz, H-16), 6.67 (dd, 1 H, J = 14.8, 10.1 Hz, H-
4), 6.70–6.75 (m, 2 H, H-8,9), 6.73 (d, 1 H, J = 14.4 Hz, H-5), 6.77
(dd, 1 H, J = 14.2, 11.1 Hz, H-13), 6.93 (d, 1 H, J = 10.4 Hz, H-3),
7.14–7.25 (m, 1 H, bipyridyl H-5'), 7.20 (d, 1 H, J = 15.9 Hz, H-17),
7.27 (dd, 1 H, J = 5.0, 1.4 Hz, bipyridyl H-5), 8.24 (s, 1 H, bipyridyl
H-3), 8.42 (s, 1 H, bipyridyl H-3'), 8.55 (d, 1 H, J = 4.9 Hz, bipyridyl
H-6'), 8.58 (d, 1 H, J = 5.1 Hz, bipyridyl H-6), 9.45 (s, 1 H, CHO).
13-(2-Thienyl)-6,11-diethyl-2-methyltrideca-2,4,6,8,10,12-
hexaenal (7)
To a suspension of Li (0.16 g, 23.0 mmol) in MeOH (40 mL) under
argon at r.t. was added CH2Cl2 (40 mL) by a syringe and subse-
quently a mixture of a 1.03 M solution of 2 (25 mL, 25.7 mmol) and
5c (1.0 g, 3.7 mmol) in CH2Cl2 (40 mL) dropwise over 2 h. After
stirring for 16 h, the mixture was washed with 1 M HCl and H2O
(100 mL each). Both aqueous layers were extracted with CH2Cl2 (3
50 mL), and the combined organic layers were dried (MgSO4) and
concentrated. Chromatography on SiO2 with CH2Cl2 as eluent and
recrystallization from toluene–MeOH gave 0.35 g (28%) of 7 as a
red solid; mp 188°C.
UV (CH2Cl2):
(101700).
( ) = 287 (26700), 474 (110500), 502 nm
max
1H NMR (500 MHz, CDCl3): = 1.12, 1.14 (each t, 3 H, J = 7.5 Hz,
6,11-CH2CH3), 1.90 (s, 3 H, 2-CH3), 2.49, 2.51 (each q, 2 H, J = 7.5
Hz, 6,11-CH2CH3), 6.28 (d, 1 H, J = 11.6 Hz, H-10), 6.39 (d, 1 H,
J = 11.6 Hz, H-7), 6.61 (d, 1 H, J = 15.9 Hz, H-5), 6.63 (d, 1 H,
J = 14.6 Hz, H-12), 6.67–6.78 (m, 3 H, H-4,8,9), 6.81 (d, 1 H,
J = 15.8 Hz, H-13), 6.95 (d, 1 H, J = 15.2 Hz, H-3), 6.97–7.01 (m, 2
HRMS (EI, 70 eV): m/z Calcd for C32H34N2O: 462.2671. Found:
462.2669.
Synthesis 2001, No. 9, 1368–1376 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Synthesis of Polyenaldehydes and Polyenetriethoxysilanes
1375
H, thienyl H-3,4), 7.17 (d, 1 H, J = 4.8 Hz, thienyl H-5), 9.45 (s, 1
H, CHO).
1.87 (s, 3 H, 2-CH3 trans), 1.95 (s, 3 H, 7-CH3 trans), 2.04 (s, 3 H,
7-CH3 cis), 2.16 (dt, 2 H, J = 7.0, 7.0 Hz, CH=CH2 trans), 2.32 (dt,
2 H, J = 7.0, 6.8 Hz, CH=CH2 cis), 5.51 (dt, 1 H, J = 11.9, 7.4 Hz,
H-9 cis), 5.90 (dt, 1 H, J = 15.5, 7.4 Hz, H-9 trans), 6.15 (d, 1 H,
J = 14.9 Hz, H-8), 6.17 (d, 1 H, J = 10.8 Hz, H-6), 6.63 (dd, 1 H,
J = 14.4, 11.5 Hz, H-4), 6.95 (d, 1 H, J = 11.0 Hz, H-3), 7.00 (dd, 1
H, J = 14.4, 11.6 Hz, H-5), 9.45 (s, 1 H, CHO).
UV (CH2Cl2): max ( ) = 271 (14700), 448 nm (89000).
Anal. Calcd for C22H26OS: C, 78.06; H, 7.74; S, 9.47. Found: C,
77.93; H, 7.76; S, 9.25.
P-Decyldibenzophosphole Following a Known Method27
A mixture of P-phenyldibenzophosphole27 (10.0 g, 38.4 mmol) in
THF (90 mL) and Li (0.5 g, 72.0 mmol) was heated to reflux for 12
h. Then bromodecane (17.0 g, 76.9 mmol) was added dropwise over
30 min, and the mixture was heated at 70°C for 4 h. After being
cooled to r.t., aq sat. NH4Cl (40 mL) was added by syringe. The ex-
cess of lithium compounds was hydrolyzed, and the organic layer
was taken by syringe under argon. The aqueous layer was extracted
with Et2O (3 40 mL) under argon. The combined organic layers
were dried (MgSO4) and concentrated. Bulb-to-bulb distillation un-
der high vacuum gave 10.34 g (83%) of P-decyldibenzophosphole
as a yellow oil, bp 175°C/0.001 Torr.
1H NMR (500 MHz, CDCl3): = 0.87 (d, 3 H, J = 6.9 Hz, CH3),
1.28–1.45 (m, 16 H, 8 CH2), 1.57–1.77 (m, 2 H, CH2), 7.29–7.37
(m, 2 H, aryl H-6,13), 7.44 (dt, 2 H, J = 7.4, 1.1 Hz, aryl H-7,12),
7.67–7.74 (m, 2 H, aryl H-8,11), 7.92 (d, 2 H, J = 7.7 Hz, aryl H-
9,10).
UV (CH2Cl2): max = 369 nm ( = 30000).
HRMS (EI, 70 eV): m/z Calcd for C20H32O: 288.24524. Found:
288.2452.
2,6,11,15-Tetramethylhexacosa-2,4,6,8,10,12,14,16-octaenal (9b)
Compound 9b was obtained from 3a (2.09 g, 7.0 mmol), 8 (0.074
M solution, 80 mL), LiN(SiMe3)2 (12 mL), stirring at 120°C for 3 h
in 11% yield as a red solid (93% all-E); mp 115°C.
1H NMR (500 MHz, CDCl3): = 0.88 [t, 3 H, J = 6.8 Hz,
(CH2)8CH3], 1.27–1.46 [m, 14 H, (CH2)7], 1.90, 1.92, 1.99, 2.00
(each s, 3 H, 2,15,6,11-CH3), 2.13 (dt, 2 H, J = 7.0 Hz, CH=CH2
trans), 2.30 (dt, 2 H, J = 7.0, 6.9 Hz, CH=CH2 cis), 5.40 (dt, 1 H,
J = 11.9, 7.4 Hz, H-17 cis), 5.75 (dt, 1 H, J = 15.0, 7.4 Hz, H-17
trans), 6.09* (d, 1 H, J = 11.5 Hz), 6.14* (d, 1 H, J = 15.5 Hz), 6.26*
(d, 1 H, J = 11.7 Hz), 6.33* (d, 1 H, J = 14.9 Hz), 6.44* (d, 1 H,
J = 11.6 Hz), 6.59–6.78* (m, 5 H), 6.93 (dd, 1 H, J = 10.9, 1.1 Hz,
H-3), 9.48 (s, 1 H, CHO).
Anal. Calcd for C22H29P: C, 81.44; H, 9.01; P, 9.55. Found: C,
81.51; H, 9.08; P, 9.47.
UV (CH2Cl2): max ( ) = 268 (21900), 458 nm (68800).
HRMS (EI, 70 eV): m/z Calcd for C30H44O: 420.33908. Found:
420.3391.
P,P-Didecyldibenzophospholium Bromide (8)
A mixture of decyldibenzophosphole (10.34 g, 31.9 mmol) and bro-
modecane (9.48 g, 42.9 mmol) was heated at 130°C for 3 h. After
cooling to r.t., the mixture was dissolved in CH2Cl2 (50 mL) and
chromatographed on SiO2 first with CH2Cl2 as eluent to remove un-
reacted bromodecane and subsequently with acetone to elute the
product. Recrystallization from diglyme afforded 13.4 g (77%) of 8
as colorless crystals; mp 81°C.
1H NMR (500 MHz, CDCl3): = 0.83 (d, 6 H, J = 7.0 Hz, CH3),
1.06–1.27 (m, 32 H, 16 CH2), 3.62 (dt, 4 H, J = 14.6, 7.4 Hz, CH2),
7.62–7.66 (m, 2 H, aryl H-7,12), 7.79 (dt, 2 H, J = 7.6, 1.1 Hz, aryl
H-9,10), 7.95 (dd, 2 H, J = 7.6, 2.5 Hz, aryl H-8,11), 8.75 (d, 2 H,
J = 8.4 Hz, aryl H-6,13).
2,6,11-Trimethyldocosa-2,4,6,8,10,12-hexaenal (10)
As described above for 3b, a cis/trans isomeric mixture of com-
pound 10 was obtained from Li (0.19 g, 27.4 mmol) in MeOH (40
mL), CH2Cl2 (40 mL), 9a (0.34 g, 1.2 mmol) in CH2Cl2 (40 mL), a
1.03 M solution of 2 in MeOH (31 mL, 31.9 mmol), and chromatog-
raphy on SiO2 with petroleum ether–CH2Cl2 (3:1) as eluent in 60%
yield as a red oil (58% all-E).
1H NMR (500 MHz, CDCl3): = 0.88 [t, 3 H, J = 6.3 Hz,
(CH2)8CH3], 1.26–1.31 [m, 14 H, (CH2)7], 1.55 (s, 3 H, 2-CH3 cis),
1.87 (s, 3 H, 6-CH3 cis), 1.90 (s, 3 H, 2-CH3 trans), 1.91 (s, 3 H, 11-
CH3 trans), 1.92 (s, 3 H, 6-CH3 trans), 1.99 (s, 3 H, 11-CH3 cis),
2.16 (dt, 2 H, J = 7.0 Hz, CH=CH2 trans), 2.32 (dt, 2 H, J = 7.0 Hz,
CH=CH2 cis), 5.81 (m, 1 H, H-13 cis/trans), 6.13 (d, 1 H, J = 11.5
Hz, H-5), 6.14 (d, 1 H, J = 14.9 Hz, H-8), 6.43 (d, 1 H, J = 11.6 Hz,
H-7), 6.52–6.69 (m, 3 H, H-4,9,10), 6.73 (d, 1 H, J = 14.8 Hz, H-12),
6.93 (d, 1 H, J = 11.2 Hz, H-3), 9.45 (s, 1 H, CHO).
Anal. Calcd for C32H50BrP: C, 70.44; H, 9.24. Found: C, 70.32; H,
9.43.
HRMS (EI, 70 eV): m/z Calcd for C32H50P+: 465.3663. Found:
465.36628.
Alkylpolyenaldehydes 9; General Procedure
UV (CH2Cl2): max ( ) = 297 (21700), 413 nm (54800).
To a solution of 8 in diglyme was added a 0.5 M solution of
LiN(SiMe3)2 in diglyme within 30 min. After stirring at r.t. for 2 h,
the mixture was transferred by cannula to the dropping funnel fitted
to a second apparatus and added dropwise over 1 h to a solution of
1a or 3a in diglyme (80 or 120 mL) at r.t. (1a) or 60°C (3a). After
stirring at 120°C for 3–4 h, diglyme was distilled off under vacuum,
and the residue was taken up in CH2Cl2 and filtered through SiO2
using CH2Cl2 as eluent (remaining phosphine oxide was eluted with
acetone and redistilled bulb-to-bulb). Chromatography on SiO2
with petroleum ether–CH2Cl2 (3:1) as eluent gave products 9 as cis/
trans isomeric mixtures.
HRMS (EI, 70 eV): m/z Calcd for C25H38O: 354.29208. Found:
354.2921.
Arylpolyeninetrimethylsilanes 12,13; General Procedure
To a suspension of 1130 in THF (40–60 mL) at –78°C was added
dropwise a 1.6 M solution of BuLi in hexane over 0.5–1 h. Then the
mixture was allowed to warm to –40°C within 1 h. After cooling
again to –78°C, the mixture was stirred for 1 h and transferred to the
dropping funnel (cooled to –78°C) fitted to a second apparatus by a
cannula and added dropwise to a solution of the respective aldehyde
5, 6 in CH2Cl2 in the absence of light over 1–2 h. After stirring for
16 h, the mixture was concentrated and dried under vacuum. The
residue was dissolved in CH2Cl2 and filtered through SiO2 with
CH2Cl2 as eluent to separate Ph3PO. Chromatography on SiO2 with
petroleum ether–CH2Cl2 (3:1), recrystallization from CH2Cl2–
EtOH and drying under high vacuum gave products 12,13
(Tables 2, 4).
2,7-Dimethyloctadeca-2,4,6,8-tetraenal (9a)
Compound 9a was obtained from 1a (2.16 g, 13.1 mmol), 8 (0.12 M
solution, 68 mL), LiN(SiMe3)2 (16 mL), stirring at 120°C for 4 h
and at r.t. for 16 h in 33% yield as a yellow oil (94% all-E).
1H NMR (250 MHz, CDCl3): = 0.88 [t, 3 H, J = 6.3 Hz,
(CH2)8CH3], 1.26–1.41 (m, 14 H, (CH2)7), 1.64 (s, 3 H, 2-CH3 cis),
Synthesis 2001, No. 9, 1368–1376 ISSN 0039-7881 © Thieme Stuttgart · New York

1376
F. Effenberger, M. Wezstein
PAPER
Arylpolyenines 14, 15; General Procedure
(13) (a) Tillmann, N.; Ulman, A.; Penner, T. L. Langmuir 1989,
5, 101. (b) Sailor, M. J.; Lee, E. J. Adv. Mater. 1997, 9, 783.
(14) (a) Harder, P.; Bierbaum, K.; Woell, C.; Grunze, M.; Heid,
S.; Effenberger, F. Langmuir 1997, 13, 445. (b) Heid, S.;
Effenberger, F.; Bierbaum, K.; Grunze, M. Langmuir 1996,
12, 2118. (c) Bierbaum, K.; Kinzler, M.; Woell, C.; Grunze,
M.; Hähner, G.; Heid, S.; Effenberger, F. Langmuir 1995,
11, 512.
To a solution of the respective silane 12, 13 in THF at r.t. in the ab-
sence of light was added a 0.5 M solution of Bu4NF 3H2O in THF,
and the mixture was stirred for the given time (Table 3, TLC con-
trol). The mixture was then washed with H2O (40 mL), and the
aqueous layer extracted with CH2Cl2 (3 20 mL). The combined or-
ganic layers were dried (MgSO4) and concentrated. The residue was
filtered through SiO2 with CH2Cl2 as eluent to remove Bu4NF.
Products 14, 15 (Tables 3, 4) were used in the next step without fur-
ther purification.
(15) Effenberger, F.; Götz, G.; Bidlingmaier, B.; Wezstein, M.
Angew. Chem., Int. Ed. Engl. 1998, 37, 2462.
(16) (a) Bumm, L. A.; Arnold, J. J.; Cygan, M. T.; Dunbar, T. D.;
Burgin, T. P.; Jones, L. II; Allara, D. L.; Tour, J. M.; Weiss,
P. S. Science 1996, 271, 1705. (b) Cygan, M. T.; Dunbar, T.
D.; Arnold, J. J.; Bumm, L. A.; Shedlock, N. F.; Burgin, T.
P.; Jones, L. II; Allara, D. L.; Tour, J. M.; Weiss, P. S. J. Am.
Chem. Soc. 1998, 120, 2721.
Arylpolyenetriethoxysilanes 16, 17; General Procedure
To a solution of crude 14a,b (1.2 or 2.1 mmol) or 15a,b (0.5 mmol)
in anhyd toluene (14b, 15b) or CH2Cl2 (40–80 mL) under argon at
r.t. in the absence of light was added HSi(OEt)3 (1.5–6.0 equiv with
reference to 14, 15) and the Pt catalyst (0.016–0.027 mmol), and the
mixture was stirred for 16 h. After concentration under vacuum, the
mixture was chromatographed on SiO2 (80 g) with anhyd CH2Cl2 as
eluent. Concentration and drying under high vacuum gave products
16, 17 (Tables 3, 4).
(17) Arbeitsvorschrift der BASF AG.
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Acknowledgement
We would like to thank the Deutsche Forschungsgemeinschaft
(SFB 329) and the Fonds der Chemischen Industrie for financial
support, and Dr. A. Baro for preparing the manuscript.
(22) Ziessel, R.; Lehn, J.-M. Helv. Chim. Acta 1990, 73, 1149;
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(23) Effenberger, F.; Schlosser, H. Synthesis 1990, 1085.
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Synthesis 2001, No. 9, 1368–1376 ISSN 0039-7881 © Thieme Stuttgart · New York