An efficient modular synthesis of conjugated ω-(p-hexyloxyphenyl)-polyenals

Article abstract of DOI:10.1055/s-2001-18711

Convenient precursors (α,β-unsaturated aldehydes 1-5) for all-E conjugated ω-(p-hexyloxyphenyl)polyenals having two (15), four (16), five, (19), six (17) and eight (18) conjugated double bonds were synthesized in a modular synthesis using reactive silyl enol ethers [1-(trimethylsilyloxy)-1,3-butadiene or 1-(trimethylsilyloxy)-1,3,5-hexatriene)] as building blocks, and 5,5-diethoxypenta-2-enal (1) as a template. Polyene 8 containing three conjugated double bonds in its structure was obtained from ω-(p-hexyloxyphenyl)propenal (6) and butadienyl ethyl ether as starting materials.

Full text of DOI:10.1055/s-2001-18711

PAPER
2463
An Efficient Modular Synthesis of Conjugated -(p-Hexyloxyphenyl)-
polyenals
An
Efficient Mod
e
ular Synthe
a
sis of Conj
t
ugate
d
a
-
(
p-Hexyloxyp
W
henyl)polyenals . Domagalska,a Ludwik Syper,b Kazimiera A. Wilk*a
a
Institute of Organic and Polymer Technology, Wroc aw University of Technology, Wybrze e Wyspia skiego 27, 50-370 Wroc aw,
Poland
Fax +48(71)3203678; E-mail: kaw@itots.ch.pwr.wroc.pl
b
Institute of Organic Chemistry, Biochemistry and Biotechnology, Wroc aw University of Technology, Wybrze e Wyspia skiego 27,
50-370 Wroc aw, Poland
Received 6 June 2001; revised 17 September 2001
boration reaction.18 Knoevenagel condensation affords a
possibility for incorporation of a double bond and donor
or acceptor entity at one time and is commonly used to
prepare conjugated polyenes with various functional
Abstract: Convenient precursors ( , -unsaturated aldehydes 1–5)
for all-E conjugated -(p-hexyloxyphenyl)polyenals having two
(15), four (16), five, (19), six (17) and eight (18) conjugated double
bonds were synthesized in a modular synthesis using reactive silyl
enol ethers [1-(trimethylsilyloxy)-1,3-butadiene or 1-(trimethylsi- groups.19
lyloxy)-1,3,5-hexatriene)] as building blocks, and 5,5-diethoxypen-
Although the synthetic achievements in the area of conju-
ta-2-enal (1) as a template. Polyene 8 containing three conjugated
double bonds in its structure was obtained from -(p-hexyloxyphe-
nyl)propenal (6) and butadienyl ethyl ether as starting materials.
gated double-bond compounds are of great importance,
they might be unsatisfactory for the structures containing
more than five conjugated double bonds. Most of the
known procedures3b,11 for n 5 reveal many by-products,
low yields and poor or limited chemo- and stereoselectiv-
ity. In our paper we report a convenient synthetic ap-
proach for -(p-hexyloxyphenyl)polyenals containing
between 2–6 and 8 double bonds in the molecular struc-
ture. Thus, in a modular synthesis, which involves reac-
tive silyl enol ethers [i.e., 1-(trimethylsilyloxy)-1,3-buta-
diene and 1-(trimethylsilyloxy)-1,3,5-hexatriene20] as
building blocks, a series of oligomeric precursors [i.e.,
5,9,9-triethoxynona-2,6-dienal (2), 5,9,13,13-tetraetho-
xy-2,6,10-trienal (3), 5,9,13,17,17-pentaethoxyheptade-
ca-2,6,10,14-tetraenal (4), and 7,11,11-triethoxyundeca-
2,4,8-trienal (5)] are obtained in a reaction which is relat-
ed to aldol-type homologations. For the synthesis of 7-(4-
hexyloxyphenyl)-5-ethoxyhepta-2,6-dienal (7) butadienyl
ethyl ether had to be applied as building block. As shown
in Schemes 1 and 2, we envisaged the use of 5,5-dietho-
xypenta-2-enal (1)21 or -(p-hexyloxyphenyl)propenal
(6) (both comprising conjugation in their structure) as a
template to generate the chain extended derivatives.
Key words: acetals, aldehydes, aldol reactions, alkenes, elimina-
tions
Conjugated polyene chains, consisting of alternating dou-
ble and single carbon–carbon bonds, are widespread mo-
lecular architectures encountered in many systems (like
carotenoids,1 retinal proteins,2 antibiotics,3 metabolites,4
natural pigments,5 antioxidating agents6) exhibiting dis-
tinct biological activities. Terminally substituted conju-
gated all-E polyenes have often been used as model
compounds for a variety of applications including elec-
tron transfer,7 light harvesting,7b,8 nonlinear optics,9 and
conductivity.7a
The central point of the synthesis of such -conjugated
structures consists mainly in the double bond-forming
procedures to access given polyenic backbones, which
can, therefore, be grafted on the electron-releasing and/or
electron-withdrawing end groups. The polyene segment
can be accessed either in a single step (by combining two
carotenoide-type polyenes,10 or via a sequential vinylic
homologation.11 In the latter case, a variety of polyene al-
dehyde and dialdehyde precursors, bearing various donor
and/or acceptor units, have been extensively applied.12
Each particular step of the designed iterative process, in-
dependently of the applied template, involves two steps.
The first one (reaction 1 in Schemes 1 and 2) denotes the
acetalization of respective , -unsaturated aldehyde with
triethyl orthoformate in the presence of pyridinium p-tol-
uenesulfonate (PPTS). The second one (reaction 2 in
Schemes 1 and 2) represents the reaction of the nucleo-
philic building block to the above mentioned acetal in the
presence of catalytic amounts of ZnCl2, giving rise to -
ethoxy- , -unsaturated aldehydes. The presented synthet-
ic approach allowed to access precursors 2–5 and 7 with
yields of 82%, 86%, 78%, 60% and 80%, respectively. All
these compounds were found to be well soluble in organic
solvents and showed chemical stability. Additionally, the
derivatives 2–5 are well suited to a nucleophilic reaction
with a Grignard reagent (Scheme 3). Thus, by reacting the
The most representative method of the double-bond for-
mation in the conjugated system is the Wittig reaction or
one of its variants (Wittig–Horner, WH; Horner–Wad-
sworth–Emmons, HWE).10,13 A site of unsaturation in the
conjugated structure can also be generated by means of
ring opening metathesis oligomerization,14 retro-Diels–
Alder reaction,15 transition-metal-catalyzed reaction,16
homocoupling reaction of unsaturated silanes17 or allyl-
Synthesis 2001, No. 16, 30 11 2001. Article Identifier:
1437-210X,E;2001,0,16,2463,2469,ftx,en;T04101SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

2464
B. W. Domagalska et al.
PAPER
Scheme 2
pyridinium hydrobromide24 (Schemes 2 and 3) give ther-
modynamically stable pure all-E isomers comprising two,
three, four, five, six and eight double bonds. The overall
yields for the given series of amphiphilic conjugated poly-
enes 8 and 15–19 ranged between 40–49%.
Scheme 1 i. (EtO)3OH, EtOH, PPTS, r.t.,
ii. CH2=CHCH=CHOSiMe3, ZnCl2, Et2O, 5 °C,
iii. CH2=CH(CH=CH)2OSiMe3, ZnCl2, Et2O, 5 °C.
All synthesized precursors 1–5 (structures 1 and 2 have
previously been reported21) and conjugated polyenals 8
and 15–19 were purified by column chromatography or/
and radial chromatography in darkness under N2 and iden-
tified unambiguously by NMR and IR spectroscopy. The
structure and stereochemistry of precursors 1–5, 7 and
alkoxyphenylmagnesium bromide 9 with compounds 1–5
under the standard Grignard reaction conditions22 the ad-
ducts 10–14 could be obtained in 68%, 65%, 59%, 55%
and 56% yield, respectively. In order to complete the syn-
thesis of conjugated -(p-hexyloxyphenyl)polyenals, wa-
ter or/and ethanol must be eliminated, double bonds
shifted and the acetal moiety hydrolyzed in a cascade of
four simultaneous reactions. The intermediates are car-
bocations, which are stable because of their allylic charac-
ter.23 The mentioned process carried out in the presence of
1
conjugated polyenals 8 and 15–19 were studied by H
NMR spectroscopy using one- (1H, 13C) and two-dimen-
sional spectra (1H-1H and 1H-13C correlated spectroscopy
- COSY). At 300 MHz these two methods allowed identi-
Scheme 3
Synthesis 2001, No. 16, 2463–2469 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
An Efficient Modular Synthesis of Conjugated -(p-Hexyloxyphenyl)polyenals
Table 1 Compounds 3–5
2465
fication of almost all protons of the studied polyenic
chains and determination of the coupling constants JCH=CH
(14.0–14.5 Hz and 14.7–15.5 Hz for precursors 1–5 and
polyenals, respectively) and JCH–CH (6.1–7.7 Hz and 10.2–
11.2 Hz for precursors 1–5 and polyenals 8 and 15–19, re-
spectively), which are characteristic for all-E structures.25
The stereochemical homogeneity of all obtained aldehyde
structures was evidenced by the presence of a single dou-
blet (at about 9.5 ppm for structures 1–5 and 9.6 ppm for
8 and 15–19) corresponding to the CHO.
Com- Yield 1H NMRa
IR (film, cm–1)
MS
pd.
, ppm (J [Hz])
(MH+)b
3
86% 1.2 (4 t, 12 H), 1.82– 3363, 3020, 2935,
369.1
1.98 (m, 4 H), 2.24
(dd, 2 H, J = 5.8, 6.6), 1659, 1478, 1443,
3.5 (m, 8 H), 4.16– 1368, 1345, 1225,
2811, 2745, 1695,
4.21 (m, 2 H), 4.66 (t, 1218, 1212, 1136,
1 H, J = 5.8 ), 5.60 (2 1125 , 1058, 972,
dd, 2 H), 5.79 (2 dd, 965, 920, 851, 554.
2 H), 6,05 (dd, 1H, J =
7.8, 14.9), 6.8 (dd, 1 H,
J = 14.0, 6.1), 9.51 (d,
Summing up, we have described a new efficient synthetic
route to obtain a number of polyene aldehydes containing
long polyenic backbones convenient reagents for the
synthesis of push-pull structures.26 The obtained -conju-
gated skeletons do not deform into bond alternant geome-
try.27 The presented synthetic approach reveals the
following features: rapid construction of carbon skeleton,
readily available building blocks, chemical stability of in-
termediate products, chemical versatility of precursors,
conjugation state systems, which sometimes can be unsta-
ble, generated under mild conditions in the last synthetic
step and all-E configuration of the system.
1 H, J = 7.8).
4
78% 1.23 (5 t, 15 H, J = 3369, 3025, 2930,
7.0), 1.78–1.98 (m, 6 2795, 1700, 1668,
H), 2.25 (dd, 2 H, J = 1473, 1445, 1370,
5.9, 6.7), 3.52 (m, 10 1340, 1250, 1210,
467.1
H), 4.18–4.23 (m, 3
H), 4.68 (t, 1 H, J =
5.9), 5.58 (3 dd, 3
H), 5.80 (3 dd, 3 H),
6.07 (dd, 1 H, J = 7.7,
14.4), 6.81 (dd, 1 H, J
= 14.5, 7.7), 9.48 (d, 1
H, J = 7.9).
1140, 1122, 1218,
1055, 970, 960, 921,
852, 549.
Starting materials were of the highest commercial quality and were
used without further purification. 5,5-Diethoxypenta-2-enal (1),
5,9,9-triethoxynona-2,6-dienal (2) and 1-(trimethylsilyloxy)-1,3,5-
hexatriene were synthesized as published in the literature.20, 21 All
reactions were carried out under a protective atmosphere of N2 gas
using oven-dried glassware. THF was freshly distilled from LiAlH4
prior to use. Electrospray ionization (ESI) spectra were obtained
with a Finnigan TSQ-700 mass spectrometer (San Jose, CA). Mps
were determined on a Kofler block and are uncorrected. Nuclear
magnetic resonance (NMR) spectra were recorded with a Bruker
AMX-300 spectrometer (Karlsruhe, Germany). 1H chemical shifts
(at 300.13 MHz) are referenced in CDCl3 to residual protons of
CDCl3 (7.24 ppm). Coupling constants (J) are given in Hz. 13C
chemical shifts we determined at 75.5 MHz with the CDCl3 signal
as reference (77.5 ppm). IR spectra were obtained on a Perkin Elmer
System 2000 FT-IR spectrometer. Elemental analyses were carried
out with a Perkin Elmer 2400 CHN analyzer (Norwalk, CT). Chro-
matographic purification was accomplished by column chromatog-
raphy using Silica Gel 60 (Merck, particle size 70–230 mesh) or/and
radial chromatography28 at 60 rpm on Silica Gel 60 GF254 (Merck,
layer thickness 2 mm, flow rate 6 mL/min) with Chromatotron ap-
paratus (Harrison Research).
5
60% 1.19 (t, 9 H, J = 6.8), 3360, 3025, 2930,
2.28 (dd, 2 H, J = 6.8, 2795, 1700, 1668,
5.7), 2.6 (dd, 2 H, J = 1670, 1473, 1445,
296.2
6.6, 5.8), 3.51 (m, 6
1370, 1340, 1250,
H), 4.15 (m, 1 H), 4.68 1210, 1140, 1122,
(t, 1 H, J = 5.65), 5.65 1218, 1055, 970,
(dd, 1 H, J = 14.1, 6.2), 960, 921, 852, 549.
5.8 (dd, 1 H, J = 14.1,
7.0), 6.05 (dd, 1 H, J =
7.8, 14.8), 6.16 (dd, 1
H, J = 7.2, 15.1), 6.8
(m, 1 H), 6.82 (dt, 1 H,
J = 7.0, 15.2), 9.48 (d,
1 H, J = 8.2).
a CDCl3.
b ESI MS.
Anal. Calcd for C21H36O5 (368.51): C, 68.45; H, 9.85. Found: C,
68.70; H, 9.75.
5,9,13,13-Tetraethoxydodeca-2,6,9-trienal (3)
5,9,13,17,17-Pentaethoxyheptadeca-2,6,10,14-tetraenal (4)
A mixture of 3 (8.0 g, 22 mmol), CH(OEt)3 (10 mL, 60 mmol) and
PPTS (100 mg, 0.40 mmol) in anhyd Et2O (10 mL) was stirred at r.t.
for 85 h. Then the mixture was poured into 5% aq NH4OH solution
(50 mL) and the aqueous layer was extracted with Et2O (4 100
mL). The combined organic layers were washed with brine, dried
with K2CO3 and the solvent was evaporated under reduced pressure.
Then the residual oil was dissolved in a solution of ZnCl2 (1.0 g,
7.34 mmol) in anhyd Et2O (5 mL). To this mixture 1-trimethylsilyl-
oxy-1,3-butadiene (3.3 g, 23 mmol) in anhyd Et2O was added drop-
wise. After 9 h of stirring at 5 °C the reaction mixture was poured
into cold water (200 mL) and Et2O (200 mL) was added. The organ-
ic phase was washed with brine, dried with MgSO4 and evaporated.
The residue was purified by flash and then radial chromatography
(hexane–EtOAc, 3:1 v/v). Yield: 8.0 g (78%). Spectroscopic data
are reported in Table 1.
A mixture of 2 (13.0 g, 48 mmol), CH(OEt)3 (10 mL, 60 mmol) and
PPTS (100 mg, 0.40 mmol) in anhyd Et2O (10 mL) was stirred at r.t.
for 80 h. Then the mixture was poured into 5% aq NH4OH solution
(50 mL) and the aqueous layer was extracted with Et2O (4 100
mL). The combined organic layers were washed with brine, dried
with K2CO3 and the solvent was evaporated under reduced pressure.
Then the residual oil was dissolved in a solution of ZnCl2 (1.0 g,
7.34 mmol) in anhyd Et2O (5 mL), 1-trimethylsilyloxy-1,3-butadi-
ene (10.0 g, 70 mmol) in anhyd Et2O (10 mL) was added dropwise.
After 6 h of stirring at 5 °C the reaction mixture was poured into
cold water (200 mL) and Et2O (200 mL) was added. The organic
phase was washed with brine, dried with MgSO4 and evaporated.
The residue was purified by column chromatography (hexane–
EtOAc, 3:1 v/v). Yield: 15.20 g (86%). Spectroscopic data are re-
ported in Table 1.
Synthesis 2001, No. 16, 2463–2469 ISSN 0039-7881 © Thieme Stuttgart · New York

2466
B. W. Domagalska et al.
PAPER
Anal. Calcd for C27H46O6 (466.66): C, 69.49; H, 9.94. Found: C,
69.66; H, 9.78.
drops). The reaction mixture was stirred at r.t. for 24 h and at 50 °C
for 10 h. Then the reaction mixture was cooled to –15 °C and fil-
tered to remove the solid, which was washed with cold acetone and
dried under reduced pressure. The products were crystallized from
CH3CN to obtain red-brown fine crystals, mp. 91–93 °C. Spectro-
scopic data for 8 are reported in Table 2.
1-(Trimethylsilyloxy)-1,3,5-hexatriene
The labile 1-(trimethylsilyloxy)-1,3,5-hexatriene was obtained ac-
cording to the method described by Iqubal and Khan20a starting
from 2,4-hexadienal (12.50 g, 130 mmol) and Me3SiCl (13.60 g,
125 mmol). The product was distilled under reduced pressure (12
mmHg, 78–80 °C, Lit. 90–100 °C/10 mmHg20a) and immediately
used after distillation. Yield: 13.40 g (63.5%, lit. 60%20).
Anal. Calcd for C19H24O2 (284.40): C, 80.24; H, 8.51. Found: C,
80.09; H, 8.66.
Compounds 10–14; General Procedure
Anal. Calcd for C9H16OSi (168.31): C, 64.23; H, 9.58. Found: C,
64.01; H, 9.66.
To a stirred solution of freshly obtained Grignard reagent 9 (10
mmol) in anhyd THF (20 mL) solution was added the appropriate
acetal 1–5 (10 mmol) in anhyd THF (50 mL) at 5 °C. Then the mix-
ture was stirred at 5 °C for 2–6 h and at r.t. for 1 h. The crude prod-
uct was isolated by liquid chromatography (hexane–AcOEt, 3:1).
7,11,11-Triethoxyundeca-2,4,8-trienal (5)
A mixture of 1 (8.0 g, 22 mmol), CH(OEt)3 (10 mL, 60 mmol) and
PPTS (100 mg, 0.40 mmol) in anhyd Et2O (10 mL) was stirred at r.t.
for 80 h. Then the mixture was poured into 5% aq NH4OH solution
(50 mL) and the aqueous layer was extracted with Et2O (4 80 ml).
The combined organic layers were washed with brine, dried with
K2CO3 and the solvent was evaporated under reduced pressure. 1-
Trimethylsilyloxy-1,3,5-hexatriene (11.0 g, 36 mmol) in anhyd
Et2O (20 mL) was then added dropwise to a well-stirred, ice-cooled
solution of bis-acetal and ZnCl2 (1.0 g, 7.34 mmol) in anhyd Et2O
(20 mL). After 36 h of stirring at 5 °C the reaction mixture was
poured into ice-water (100 mL). The organic phase was shaken with
sat. aq NaHCO3 solution and water, dried with MgSO4 and the sol-
vent was removed in vacuo. The residue was purified by column
chromatography (hexane–EtOAc, 3:1 v/v). Yield: 5.30 g (60%).
Spectroscopic data are reported in Table 1.
5-(4-Hexyloxyphenyl)-1,1-diethoxy-5-hydroxypenta-3-ene (10)
Yield 2.40 g (68%).
Anal. Calcd for C21H34O4 (350.5): C, 71.96; H, 9.78. Found: C,
71.66; H, 9.89.
1H NMR: = 0.9 (t, 3 H, J = 6.9), 1.20 (t, 6 H, J = 7.2), 1.30–1.83
(m, 8 H), 2.46 (dd, 2 H, J = 5.8), 3.50–3.65 (m, 4 H), 3.97 (t, 2 H,
J = 6.54), 4.39–4.5 (ddt, 2 H), 5.59 (dd, 1 H, J = 9.4, 14.9), 5.70 (d,
1 H, J = 9.0), 6.02 (dd, 1 H, J = 6.9, 14.0), 6.86 (d, 2 H, J = 8.7),
7.36 (d, 2 H, J = 8.8).
IR (film): 3430, 2932, 2870, 1724, 1676, 1618, 1591, 1512, 1467,
1422, 1266, 1239, 1154, 1139, 1122, 1083, 1014, 969, 801, 754,
613 cm–1.
Anal. Calcd for C17H28O4 (296.41): C, 68.89; H, 9.52. Found: C,
68.61; H, 9.66.
9-(4-Hexyloxyphenyl)-1,1,5-triethoxy-9-hydroxynona-3,7-diene
(11)
Yield: 2.90 g (65%).
3-(4-Hexyloxyphenyl)propenal (6)
The synthesis was performed according to the procedure described
by Reddy et al.,29 starting from 4-hexyloxybenzaldehyde. Spectro-
scopic data for 6 are reported in Table 2. Mp. 32–34 °C.
Anal. Calcd for C27H44O5 (448.64): C, 72.28; H, 9.89. Found: C,
72.11; H, 9.99.
1H NMR: = 0.90 (t, 3 H, J = 7.0), 1.18 (t, 9 H, J = 7.1), 1.31–1.83
(m, 8 H), 2.08 (dd, 2 H, J = 6.0), 2.50 (dd, 2 H, J = 5.9, 6.0), 3.40
(m, 6 H), 3.97 (t, 2 H, J = 7.1), 4.0 (m, 1 H), 4.38–4.48 (ddt, 2 H),
5.60 (dd, 1 H, J = 8.8, 14.6), 5.72 (d, 1 H, J = 8.8), 5.85 (m, 1 H),
6.0 (dd, 1 H, J = 7.1, 14.0), 6.68 (m, 1 H), 6.88 (d, 2 H, J = 8.8), 7.34
(d, 2 H, J = 8.9).
Anal. Calcd for C15H20O2 (232.32): C, 77.55; H, 8.68. Found: C,
77.37; H, 8.77.
7-(4-Hexyloxyphenyl)-5-ethoxyhepta-2,6-dienal (7)
A mixture of 6 (7.0 g, 30 mmol), CH(OEt)3 (10 ml, 60 mmol) and
PPTS (100 mg, 0.40 mmol) in anhyd Et2O (25 mL) was stirred at r.t.
for 10 h. Then the mixture was poured into 5% aq NH4OH solution
(50 mL) and the aqueous layer was extracted with Et2O (4 80 mL).
The combined organic layers were washed with brine, dried with
K2CO3 and the solvent was evaporated under reduced pressure. A
solution of ZnCl2 (2.0 g, 14.68 mmol) in EtOAc (5 mL) was then
added to a well-stirred ice-cooled solution of acetal (27 mmol) and
butadienyl ether (4.0 g, 41 mmol) in CH2Cl2 (30 mL). After 3 h of
stirring at 5 °C and 5 h at r.t. the reaction mixture was poured into
cold water and CH2Cl2 was added. The phases were separated, the
organic phase washed with water, dried over MgSO4 and evaporat-
ed. The residue was purified by column chromatography (silicagel,
hexane–isopropylether, 7:3 v/v) to give 7.90 g (80%) of 7.
IR (film): 3433, 2930, 2869, 1728, 1680, 1610, 1599, 1515, 1466,
1420, 1270, 1235, 1150, 1135, 1119, 1091, 1015, 971, 800, 754
cm–1.
13-(4-Hexyloxyphenyl)-1,1,5,9-tetraethoxy-13-hydroxy-tride-
ca-3,7,9-triene (12)
Yield: 3.20 g (59%).
Anal. Calcd for C33H54O6 (546.79): C, 72.49; H, 9.95. Found: C,
72.31; H, 10.1.
1H NMR: = 0.91 (t, 3 H, J = 7.0), 1.18, (4 t, 12 H, J = 6.8), 1.29–
1.85 (m, 8 H), 2.1 (dd, 2 H, J = 6.0), 2.50 (dd, 2 H, J = 6.0), 2.55
(dd, 2 H, J = 6.0), 3.35 (m, 8 H), 4.00 (m, 2 H), 4.05 (t, 2 H, J = 7.1),
4.39–4.49 (dd+t, 2 H), 5.62, (dd, 1 H, J = 6.9, 15.0), 5.71 (d, 1 H,
J = 8.9), 5.90 (m, 3 H), 6.10 (dd, 1 H, J = 7.1, 14.2), 6.68 (m, 1 H),
6.85 (d, 2 H, J = 8.6), 7.41 (d, 2 H, J = 8.8).
Anal. Calcd for C21H30O3 (330.47): C, 76.33; H, 9.15. Found: C,
76.15; H, 9.28.
1H NMR: = 0.91 (t, 3 H, J = 7.1), 1.2 (m, 3 H), 1.32–1.80 (m, 6
H), 1.82 (m, 2 H, J = 6.7), 2.5 (m, 2 H), 3.9 (t, 2 H, J = 6.8), 3.5 (m,
3 H), 4.17 (m, 1 H), 5.65 (dd, 1 H, J = 6.6, 14.8), 6.10 (dd, 1 H,
J = 8.0, 15.0), 6.25 (d, 1 H, J = 14.9), 6.7–6.9 (m, 3 H), 7.33 (d, 2
H), 9.51 (d, 1 H, J = 8.1).
IR (film): 3624, 3035, 3023, 2845, 1670, 1632, 1550, 1514, 1462,
1382, 1230, 1235, 1157, 1050, 970, 790 cm–1.
17-(4-Hexyloxyphenyl)-1,1,5,9,13-pentaethoxy-17-hydroxy-
heptadeca-3,7,11,15-tetraene (13)
Yield: 3.41 g (55%).
7-(4-Hexyloxyphenyl)hepta-2,4,6-trienal (8)
To a solution of 7 (6.60 g, 20 mmol) in acetone (30 mL) was added
pyridine hydrobromide (0.60 g), H2O (2 mL) and HBr (62%, two
Anal. Calcd for C39H64O7 (644.93): C, 72.63; H, 10.00. Found: C,
72.41; H, 10.15.
Synthesis 2001, No. 16, 2463–2469 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
An Efficient Modular Synthesis of Conjugated -(p-Hexyloxyphenyl)polyenals
2467
1H NMR: = 0.91 (t, 3 H, J = 6.9), 1.2 (5 t, 15 H, J = 6.8), 1.27–
1.84 (m, 8 H), 2.1 (dd, 2 H, J = 6.2), 2.49 (m, 6 H), 3.35 (m, 10 H),
4.0 (t, 2 H, J = 7.1), 4.1 (m, 3 H), 4.39–4.45 (tdd, 2 H), 5.62 (dd, 1
H, J = 15, 7.0), 5.70 (d, 1 H, J = 8.9), 5.85 (m, 2 H), 5.91 (m, 3 H),
6.1 (dd, 1 H, J = 7.0, 14.2), 6.68 (m, 1 H), 6.81 (d, 2 H, J = 8.8), 7.40
(d, 2 H, J = 8.9).
Anal. Calcd for C29H46O5 (474.68): C, 73.38; H, 9.77. Found: C,
73.18; H, 9.93.
1H NMR: = 0.89 (t, 3 H, J = 6.9), 1.2 (3 t, 9 H, J = 7.1), 1.25
– 1.82 (m, 8 H), 2.2 (dd, 2 H, J = 6.2, 7.0), 2.50 (m, 2 H), 3.35 (m,
6 H), 3.97–4.15 (m, 4 H), 4.93 (t, 1 H, J = 6.9), 5.67 (m, 1 H), 5.72
(d, 1 H, 8.9), 5.70 (dd, 1 H, J = 7.1, 15, 0), 6.08–6.16 (2 dd, 2 H),
6.79 (d, 2 H, J = 8.8), 6.80–6.83 (m, 2 H), 7.38 (d, 2 H, J = 8.8).
IR (film): 3625, 3033, 3025, 2850, 1668, 1630, 1625, 1548, 1515,
1460, 1380, 1350, 1232, 1234, 1152, 1051, 967, 788 cm–1.
IR (film): 3625, 3033, 3025, 2850, 1668, 1630, 1625, 1548, 1515,
1460, 1380, 1350, 1232, 1234, 1152, 1051, 967, 788 cm–1.
11-(4-Hexyloxyphenyl)-1,1,5-triethoxy-11-hydroxyundecka-
3,7,9-triene (14)
Yield: 2.63 g, 56%.
Table 2 Amphiphilic Conjugated Polyenes C6H13OC6H4(CH=CH)nCHO
Compd. Yield 1H NMRa
, ppm (J, Hz)
13C NMRa
, ppm
IR (cm–1)
MSb
(MH+)
6
8
40% 0.90 (t, 3 H, J = 6.9), 1.30–1.80 (m, 6 H), 1.81 (m, 2 14.7, 23.09, 26.5, 29.9, 33.8, 2932, 2859, 1677, 1621, 1602, 233.1
H, J = 6.5), 3.99 (t, 2 H, J = 6.6), 6.35 (dd, 1 H, J = 66.1, 111.0 (2C), 123.0, 127.1 1571, 1512, 1250, 1175, 1127,
15.4, 7.8), 6.95 (d, 2 H, J = 8.7), 7.40 (d, 1 H, J =
(2C), 149.1, 151.4, 152.5,
971
15.4), 7.50 (d, 2 H, J = 8.7), 9.60 (d, 1 H, J = 7.71). 193.3.
57% 0.90 (t, 3 H, J = 6.9), 1.29–1.80 (m, 6 H), 1.80 (m, 2 14.4, 23.3, 26.0, 29.8, 33.1,
3023, 2940, 2857, 1665, 1622, 285.1
H, J = 6.6), 3.97 (t, 2 H, J = 6.5), 6.21 (dd, 1 H, J = 66.1, 112.0 (2C), 120.9, 126.5, 1586, 1510, 1472, 1423, 1408,
15.2, 7.9), 6.55 (dd, 1 H, J = 14.4, 11.3), 6.78 (d, 1 H, 128.5 (2C), 131.0, 138.8, 142.6, 1395, 1314, 1302, 1291, 1237,
J = 14.8), 6.82 (dd, 1 H, J = 14.5, 11.2), 6.85 (d, 2 H, 146.8, 152.6, 155.4, 193.3
J = 8.7), 6.89 (dd, 1 H, J = 14.7, 11.2), 7.19 (dd, 1 H,
J = 15.1, 11.2), 7.36 (d, 2 H, J = 8.6), 9.56 (d, 1 H, J
= 8.0)
1256, 1177, 1146, 1109, 1058,
1027, 1019, 997, 858, 826, 796,
730, 644, 626, 593, 528
15
16
58% 0.90 (t, 3 H, J = 6.9), 1.30–1.79 (m, 6 H), 1.80 (m, 2 14.8, 23.1, 27.0, 29.4, 33.6,
2940, 2851, 1665, 1590, 1510, 259.2
H, J = 6.6), 3.97 (t, 2 H, J = 6.54), 6.21 (dd, 1 H, J = 66.1, 118 (2C), 121.3, 124.0, 1471, 1396, 1309, 1249, 1180,
15.1, 8.0), 6.84 (d, 1 H, J = 15.7), 6.91 (dd, 1 H, J = 128.5 (2C), 130.9, 142.6, 150.0, 1028, 970, 844, 796, 640
10.2, 15.7), 6.97 (d, 2 H, J = 8.7), 7.24 (dd, 1 H, J = 152.0, 193.3
15.1, 10.2), 7.43 (d, 2 H, J = 8.8), 9.58 (d, 1 H, J =
8.0)
58% 0.90 (t, 3 H, J = 7.0), 1.30–1.81 (m, 6 H), 1.83 (m, 2 15.0, 22.8, 26.1, 29.2, 33.5,
3022, 2950, 2858, 1730, 1640, 311.2
H, J = 6.5), 3.96 (t, 2 H, J = 6.9), 6.16 (dd, 1 H, J = 59.9, 119.9 (2C), 120.9, 126.3 1620, 1601, 1575, 1511, 1248,
7.9, 15.2), 6.39 (dd, 1 H, J = 15.1, 11.2), 6.45 (dd, 1 (2C), 129.0, 130.3, 130.6,
H, J = 11.0, 15.2), 6.62–6.64 (2 dd, 2 H), 6.72–7.75 132.5, 136.5, 139.6, 142.2,
(2 dd, 2 H), 6.90 (dd, 2 H, J = 8.7), 7.13 (dd, 1 H, J 150.1, 152.5, 193.2
= 11.0, 15.0), 7.40 (dd, 2 H, J = 8.8), 9.63 (d, 1 H, JHH
1180, 1025, 975, 835, 795, 645,
615, 532
= 8.0)
17
18
47% 0.91 (t, 3 H, J = 6.9), 1.33–1.80 (m, 6 H), 1.82 (m, 2 14.1, 22.7, 25.7, 29.2, 31.6,
3027, 2961, 2937, 2853, 1677, 363.1
H, J = 6.6), 3.94 (t, 2 H, J = 6.5), 6.24 (dd, 1 H, J = 68.1, 114.8 (2C), 126.8, 127.8 1586, 1508, 1471, 1392, 1302,
15.3, 7.3), 6.32–6.45 (4 dd, 4 H), 6.54–6.58 (3 dd, (2C), 129.7, 130.7, 131.3,
3 H), 6.55 (d, 1 H, J = 15.0), 6.72 – 6.75 (2 dd, 2 131.8, 133.9, 136.1, 137.0,
1289, 1254, 1237, 1175, 1146,
1118, 1109, 1026, 1011, 989,
923, 855, 828, 795, 643, 625,
533
H), 6.84 (d, 2 H, J = 8.7), 7.13 (dd, 1 H, J = 10.1,
139.1, 142.8, 143.6, 149.9,
15.1), 7.35 (d, 2 H, J = 8.7), 9.56 (d, 1 H, J = 8.3) 151.8, 159.2, 193.5.
38% 0.91 (t, 3 H, J = 6.9), 1.33–1.80 (m, 6 H), 1.82 (m, 2 14.0, 22.6, 25.7, 29.3, 31.7,
H, J = 6.6), 3.94 (t, 2 H, J = 6.9), 6.24 (dd, 1 H, J = 66.2, 111.2 (2C), 120.3, 126.9,
15.5, 7.9), 6.32–6.45 (6 dd, 6 H), 6.54–6.58 (5 dd, 127.9 (2C), 129.6, 130.2, 130.8,
5 H), 6.55 (d, 1 H, J = 15.0), 6.72–6.75 (2 dd, 2 H), 131.2, 131.7, 134.7, 136.2,
6.84 (d, 2 H, J = 8.8), 7.23 (dd, 1 H, J = 10.5, 15.5), 137.8, 138.5, 139.2, 142.8,
415.2
7.34 (d, 2 H, J = 8.8), 9.56 (d, 1 H, J = 8.3)
143.2, 146.8, 149.0, 149.5,
151.8, 193.4
19
47% 0.90 (t, 3 H, J = 6.9), 1.34–1.82 (m, 6 H), 1.83 (m, 2 14.3, 22.6, 25.7, 29.2, 31.9,
3022, 2950, 2858, 1731, 1640, 337.2
H, J = 6.5), 3.97 (t, 2 H, J = 6.6), 6.15 (dd, 1 H, J = 66.1, 111.9 (2C), 120.8, 126.1 1636, 1630, 1625, 1601, 1575,
15.0, 8.0), 6.36–6.45 (3 dd, 3 H), 6.53–6.56 (2 dd, (2C), 129.4, 130.1, 130.5,
2 H), 6.58 (d, 1 H, J = 14.9), 6.72–6.75 (2 dd, 2 H), 131.0, 131.6, 134.4, 137.1,
6.84 (d, 2 H, J = 8.8), 7.32 (dd, 1 H, J = 15.2, 11.0), 139.2, 142.9, 151.9, 193.5
7.48 (d, 2 H, J = 8.8), 9.56 (d, 1 H, J = 8.3).
1511, 1248, 1180, 1025, 975,
832, 793, 645, 610, 531
a CDCl3. b ESI M.
Synthesis 2001, No. 16, 2463–2469 ISSN 0039-7881 © Thieme Stuttgart · New York

2468
B. W. Domagalska et al.
PAPER
(6) Traber, B.; Pfander, H. Tetrahedron 1998, 54, 9011.
(7) (a) Spangler, C. W. J. Mater. Chem. 1999, 9, 2013.
(b) Gust, D.; Moore, T. A.; Moore, A. L. Acc. Chem. Res.
1993, 26, 198.
(4-Hexyloxyphenyl)polyenals C6H13OC6H4(CH=CH)nCHO 15
19 (n = 2, 4, 5, 6, 8); General Procedure
The appropriate acetal (10–14) was added to a solution of a pyridine
hydrobromide (0.10 g, 600 mmol) in acetone containing water (0.2
mL). The mixture was stirred at 40 °C for 20–46 h, then poured into
cold water (25 mL) and extracted with anhyd Et2O (2 25 mL). The
organic phase was washed with cold water, dried with MgSO4 and
evaporated. The residue was purified first by column and than by ra-
dial chromatography (hexane–EtOAc, 3:1 4:1) to give polyenals
15–19. Yields and spectroscopic data for polyenals 15–19 are re-
ported in Table 2.
(8) Danishefsky, S. J.; Shair, H. D. Liebigs Ann. / Recueil 1997,
2205.
(9) (a) Garito, A. F.; Jen, A. K.-Y.; Lee, C. Y.-C.; Dalton, L. R.
In Electrical, Optical, and Magnetic Properties of Organic
Solid State Materials, Vol. 328; MRS: Pittsburg, 1984.
(b) Prasad, P. N.; Williams, D. J. Introduction to Nonlinear
optical effects in molecules and polymers; Wiley: New York,
1991. (c) Nonlinear Optical Properties of Organic
Molecules and Crystals, Vol. 1 and 2; Chemla, D. S.; Zyss,
J., Eds.; Academic Press: New York, 1987. (d) ACS
Symposium Series 455, Materials for Nonlinear Optics:
Chemical Properties; Marder, S. R.; Sohn, J. E.; Stucky, G.
D., Eds.; ACS: Washington, 1991. (e) Fort, A.; Muller, J.;
Mager, L. Chem. Phys. 1999, 243, 115. (f) Beckmann, S.;
Etzbach, K.-H.; Krämer, P.; Lukaszuk, K.; Matschiner, R.;
Schmidt, A. J.; Schuhmacher, P.; Sens, R.; Seybold, G.;
Wortmann, R.; Würthner, F. Adv. Mater. 1999, 11, 536.
(g) Stecher, R.; Gompf, B.; Münter, J. S. R.; Effenberger, F.
Adv. Mater. 1999, 11, 927. (h) Barlow, S.; Marder, S. R.
Chem. Commun. 2000, 1555.
(2E,4E)-5-(4-Hexyloxyphenyl)penta-2,4-dienal (15)
Pale, fine, yellow crystals, mp 76–78 °C.
Anal. Calcd for C17H22O2 (258.36): C, 79.03; H, 5.58. Found: C,
78.99; H, 5.64.
(2E,4E,6E,8E)-9-(4-Hexyloxyphenyl)nona-2,4,6,8-tetraenal
(16)
Brown, fine crystals, mp 100–101 °C.
Anal. Calcd for C21H26O2 (310.44): C, 81.25; H, 8.44. Found: C,
81.12; H, 8.52.
(2E,4E,6E,8E,10E,12E)-13-(4-Hexyloxyphenyl)trideca-
2,4,6,8,10,12-hexaenal (17)
Brown, fine crystals, mp 121–123 °C.
(10) (a) Effenberger, F.; Schlosser, H.; Bäuerle, S. M.; Maier, S.;
Port, H.; Wolf, H. C. Angew. Chem., Int. Ed. Engl. 1988, 27,
281. (b) Duhamel, L.; Guillemont, J.; Gallic, Y. L.; Plé, G.;
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Anal. Calcd for C25H30O2 (362.51): C, 72.43; H, 8.34. Found: C,
72.2; H, 8.21.
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890. (b) von Märkl, G.; Pöl, A.; Aschenbrenner, N. G.;
Schmaus, C.; Troll, T.; Kreitmeier, P. Helv. Chim. Acta
1996, 79, 1497. (c) Friedli, A. C.; Yang, E.; Marder, S. R.
Tetrahedron 1997, 53, 2717.
(2E,4E,6E,8E,10E,12E,14E,16E)-17-(4-Hexyloxyphenyl)-hep-
tadeca-2,4,6,8,10,12,14,16-octaenal (18)
Dark, brown solid, mp 135–137 °C.
Anal. Calcd for C29H34O2 (414.59): C, 84.02; H, 8.27. Found: C,
83.9; H, 8.3.
(13) (a) Maryanoff, B. E.; Reitz, A. B. Chem. Rev. 1989, 89, 863.
(b) Elandaloussi, E. H.; Frere, P.; Roncali, P.; Richomme, P.;
Jubault, M.; Gorgues, A. Adv. Mater. 1995, 7, 390.
(c) Raimunda, J. M.; Blanchard, P.; Ledoux-Rak, I.; Hierle,
M.; Roncali, J. Chem. Commun. 2000, 1579.
(2E,4E,6E,8E,10E)-11-(4-Hexyloxyphenyl)undeca-2,4,6,8,10-
pentaenal (19)
Brown, fine crystals, mp 113–115 °C.
Anal. Calcd for C23H28O2 (336.47): C, 82.1; H, 8.39. Found: C,
82.0; H, 8.50.
(d) Effenberger, F.; Heid, S.; Merkle, R.; Zimmermann, P.
Synthesis 1995, 1115. (e) Mladenova, M.; Ventelon, L.;
Blanchard-Desce, M. Tetrahedron Lett. 1999, 40, 6923.
(f) Alain, V.; Blanchard-Desce, M.; Ledoux-Rak, I.; Zyss, J.
Chem. Commun. 2000, 353. (g) Alain, V.; Redoglia, S.;
Blanchard-Desce, M.; Lebus, S.; Lukadzuk, K.; Wortmann,
R.; Gubler, U.; Bosshard, C.; Günter, P. Chem. Phys. 1999,
245, 145. (h) Marder, I. R.; Takeheng, L.; Tiemman, B. G.;
Friedli, A. C.; Blanchard, –. D. e. s. c. e. M.; Perry, J. W.;
Skindhoj, J. Science 1995, 264, 487. (i) Blanchard-Desce,
M.; Runser, C.; Fort, A.; Barzoukas, M.; Lehn, J.-M.; Bloy,
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D.; Beutner, S.; Briviba, K.; Martin, H. D.; Paust, J.; Peters,
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Liebigs Ann./Recueil 1997, 1887. (k) Alain, V.; Blanchard-
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353.
Acknowledgments
Support of this work by the State Committee of Scientific Research
(Grants No. 2P 303 072 07 and 7 T09A 063 20) is gratefully ack-
nowledged.
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Synthesis 2001, No. 16, 2463–2469 ISSN 0039-7881 © Thieme Stuttgart · New York