Star-Shaped Compounds Having 1,3,5-Triazine Cores

Article abstract of DOI:10.1002/ejoc.200300132

The 1,3,5-triazine derivatives 1-4 having styryl or higher oligo(phenylenevinylene) chains in the 2-, 4-, and 6-positions represent star-shaped push-pull compounds. Alkoxy or dimethylamino groups on the peripheral benzene rings, which act as electron donors, and the central 1,3,5-triazine ring, which acts as an electron acceptor, cause intramolecular charge transfer (ICT) to occur in the absorption S₀→S ₁. Protonation of the 1,3,5-triazine core enhances the effect, as demonstrated by a bathochromic shift; a secondary protonation on the dimethylamino groups, however, leads to the breakdown of the ICT. Thus, the yellow compound Id first becomes violet and then colorless upon the addition of trifluoroacetic acid. In neutral solution, the long-wavelength absorption of the series 1f, 2b, 3, and 4 converges to λ_∞ = 427 nm (with an effective conjugation length n_ECL = 7). The absorption of the corresponding protonated compounds approaches λ_∞ = 515 nm (n_ECL = 6). Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejoc.200300132

FULL PAPER
Star-Shaped Compounds Having 1,3,5-Triazine Cores
Herbert Meier,*[a] Hans Christof Holst,[a] and Annette Oehlhof[a]
Keywords: Absorption / Conjugation / Oligomerizations / Push-pull effects
The 1,3,5-triazine derivatives 1−4 having styryl or higher oli-
go(phenylenevinylene) chains in the 2-, 4-, and 6-positions
represent star-shaped push-pull compounds. Alkoxy or di-
methylamino groups on the peripheral benzene rings, which
act as electron donors, and the central 1,3,5-triazine ring,
which acts as an electron acceptor, cause intramolecular
breakdown of the ICT. Thus, the yellow compound 1d first
becomes violet and then colorless upon the addition of tri-
fluoroacetic acid. In neutral solution, the long-wavelength
absorption of the series 1f, 2b, 3, and 4 converges to λϱ
=
427 nm (with an effective conjugation length nECL = 7). The
absorption of the corresponding protonated compounds ap-
charge transfer (ICT) to occur in the absorption S0ǞS1. Pro- proaches λϱ = 515 nm (nECL = 6).
tonation of the 1,3,5-triazine core enhances the effect, as
demonstrated by a bathochromic shift; a secondary pro-
tonation on the dimethylamino groups, however, leads to the
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
Introduction
Conjugated oligomers are attracting increased attention
because their optical, electrical, and optoelectronic proper-
ties lead to interesting applications in materials science;
moreover, they are model compounds for their correspond-
ing conjugated polymers.[1Ϫ20]
The building blocks of these oligomers, for example, 1,4-
phenylenevinylene units, are in most cases linearly arranged,
but instances of the use of cyclic,[21] dendritic,[22Ϫ29] and
star-shaped structures[16,30] are also known. Recently, we
found that a terminal donorϪacceptor substitution in lin-
ear systems causes an unexpected behavior to occur in their
optical properties.[31Ϫ39] This article focuses on the star-like
systems 1Ϫ4, which have an electron-deficient 1,3,5-triazine
core and styryl or oligo(1,4-phenylenevinylene) (OPV) arms
that feature terminal electron-releasing substituents.
Scheme 1 displays the general formula of these compounds.
Scheme 1. Star-shaped compounds 1Ϫ4 having 1,3,5-triazine cores,
which behave as electron acceptors, and OPV arms featuring ter-
minal donor substituents
Results and Discussion
The high reactivity of 2,4,6-trimethyl-1,3,5-triazine (5) in
alkaline condensation reactions with aldehydes is well
known; however, the product of its reaction with benzal-
dehyde (6a), namely 2,4,6-tristyryl-1,3,5-triazine (1a), is
mentioned sparingly in the literature.[34Ϫ36] We prepared the
para-substituted derivatives 1bϪe by treating 5 with the al-
dehydes 6bϪe (Scheme 2). The reaction times at room tem-
perature amounted to several days. The aldehyde 6d reacts
particularly slowly because of its low nucleophilicity. Thus,
the twofold condensation product, 2,4-bis{(E)-2-[4-
(dimethylamino)phenyl]ethenyl}-6-methyl-1,3,5-triazine
(1dЈ), is still present after a reaction time of 7 d.
The push-pull effect in the three arms becomes evident
by the polarization of the olefinic bridges, which is ex-
pressed by considerable differences in the chemical shifts
[a]
Institut für Organische Chemie der Johannes Gutenberg-
Universität,
1
observed in 13C and H NMR spectra. According to the
Duesbergweg 10Ϫ14, 55099 Mainz, Germany
Fax: (internat.) ϩ 49-6131/3925396
E-mail: hmeier@mail.uni-mainz.de
trend of their increasing donor strengths, the ∆δ (13C) val-
ues of the two olefinic carbon atoms increase in the series
Eur. J. Org. Chem. 2003, 4173Ϫ4180
DOI: 10.1002/ejoc.200300132
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H. Meier, H. C. Holst, A. Oehlhof
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Scheme 2. Preparation of the (E,E,E)-2,4,6-tristyryl-1,3,5-triazines
1aϪe
1a, 1e, 1b, 1c, 1d (15.4, 16.0, 16.7, 17.0, and 19.9 ppm,
respectively), as do the values of ∆δ (1H) of the olefinic
protons (1.11, 1.14, 1.20, 1.20, and 1.26 ppm, respectively).
Table 1 summarizes the 1H and 13C NMR spectroscopic
data of compounds 1aϪe.
Scheme 3. Preparation of 2,4,6-tris[(E)-2-(4-{(E)-2-[4-(hexyloxy)-
phenyl]ethenyl}phenyl)ethenyl]-1,3,5-triazine (2a)
To extend the conjugated arms of the star-shaped com-
pounds 1, we transformed 1e into the triphosphonate 1f by
The push-pull effect in 2a causes a polarization of the
a WohlϪZiegler bromination with NBS and a subsequent olefinic bonds, which is reduced relative to that of 1c. The
Arbusov reaction with triethyl phosphite. The values of ∆δ(13C) and ∆δ(1H) for the inner double bond are
WittigϪHorner olefination of 1f with 4-(hexyloxy)benzal- 15.4 and 1.12 ppm, respectively, and for the outer double
dehyde (6c) gave the target compound 2a (Scheme 3).
bond they are 3.8 and 0.16 ppm, respectively.[37]
1
Table 1. H and 13C NMR spectroscopic data of compounds 1aϪe (δ values in CDCl3, relative to TMS as internal standard; coupling
3
constants Jtrans in Hz)
Triazine
Cq
Vinylene
Phenyl(ene)
Side chain
HCi(nner) HCo(uter) 3JH,H i-C
o-CH
m-CH
p-C(H)
1a
1b
1c
7.17
126.3
7.01
124.3
7.00
8.28
141.7
8.21
141.0
8.20
16.0
15.8
15.7
7.69
135.5 128.2
7.62
128.5 129.7
7.61
7.41
128.9
6.94
114.4
6.92
7.41
129.7
171.3
171.4
3.85 (OCH3)
55.4 (OCH3)
3.99 (OCH2)
161.1
1.79 (CH2)
1.46 (CH2)
1.34 (2CH2)
31.6 (CH2)
29.2 (CH2)
25.7 (CH2)
22.6 (CH2)
0.90(CH3)
14.0(CH3)
171.4
124.1
141.1
128.3 129.7
114.9
160.7
68.2 (OCH2)
1d
1e
6.92
121.5
7.10
125.5
8.18
141.4
8.24
141.5
15.9
16.0
6.71
123.8 129.7
7.58
132.9 128.1
7.57
112.0
7.22
3.02 (NCH3)
40.2 (NCH3)
2.38 (CH3)
171.3
171.4
151.3
140.1
129.6
21.4 (CH3)
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Star-Shaped Compounds Having 1,3,5-Triazine Cores
FULL PAPER
Because of the moderate yields of 2a, we explored an-
other route for the preparation of the star-shaped 1,3,5-tria-
zines 2Ϫ4 having extended conjugated arms and terminal
donor substituents. Starting with 3,4,5-tris(hexyloxy)ben-
zaldehyde (11a), we prepared the OPV aldehydes 11b, 11c,
and 11d. The phosphonate 10, which contains a protected
formyl group, proved to be very valuable for this purpose.
In the acidic workup of the WittigϪHorner reaction be-
tween 11a and 10, a deprotection occurred, such that alde-
hyde 11b was obtained, which could be extended by the
same procedure to 11c and further to 11d (Scheme 4). The
purified aldehydes did not show any traces of cis-configured
1
isomers when analyzed by H and 13C NMR spectroscopy
(detection limit ϭ 3%). The synthon 10, which we have used
earlier,[28,30,38] was prepared using a new route that resulted
in much higher yields. 4-Bromomethylbenzonitrile (7) was
first transformed into 4-bromomethylbenzaldehyde (8),
whose quantitatively formed diethyl acetal (9) was subjected
to an Arbusov reaction with triethyl phosphite (Scheme 4).
Scheme 5. Preparation of the 1,3,5-triazines 1g, 2b, 3, and 4 having
conjugated OPV arms and threefold terminal hexyloxy substitution
the monostyryl compound 12 and the distyryl system 13 as
the major products (Scheme 6).
Scheme 6. Stepwise condensation of 5 and 11a to yield 12 and 13
Scheme 4. Extension of the conjugated OPV chain in the series of
the aldehydes 11aϪd
1
The H and 13C NMR spectroscopic data of the olefinic
units in 1g, 2b, 3, and 4 are summarized in Table 2. The
polarization of the inner double bond α,αЈ is strong and
slightly reduced by the extension of the conjugation; the
The convergent synthesis of 1Ϫ4 was then accomplished polarization of the other double bonds is low and also
by the alkaline condensation of 2,4,6-trimethyl-1,3,5-tri- changes slightly with the length of the OPV chain.
azine (5) with the aldehydes 11aϪd. The yields decrease
within this series from 79 to 15% (Scheme 5).
The length of the conjugated chain has, of course, a
strong influence on the UV/Vis spectra. Because of cross-
When the condensation reaction between 5 and 11a was conjugation on the central triazine ring, the long-wave-
performed with less than 3 mol-equiv. of 11a, we obtained length maxima do not depend significantly on the number
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H. Meier, H. C. Holst, A. Oehlhof
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1
Table 2. H and 13C NMR spectroscopic data of the polarized vinylene bridges in the OPV arms of 1g, 2b, 3, and 4 (δ values in CDCl3,
3
relative to TMS as internal standard; coupling constants Jtrans in Hz; the symbols α to δЈ correspond to the olefinic positions from the
core to the periphery)[37]
Olefinic double bonds
α-HC
αЈ-HC
3J
15.7
β-HC
βЈ-HC
3J
γ-HC
γЈ-HC
3J
δ-HC
δЈ-HC
3J
1g
2b
3
7.00
125.1
7.15
125.9
7.13
126.0
7.11
8.15
141.8
8.25
141.1
8.23
141.0
8.22
15.9
15.6
15.7
6.97
126.9
7.10
127.6
7.08
7.08
130.1
7.16
129.4
7.14
16.2
16.4
16.0
6.95
127.1
7.08
7.02
129.0
7.08
16.0
[a]
4
6.94
7.00
16.0
126.0
140.6
127.7
129.1
127.9
128.2
127.1
128.9
[a]
AB spin pattern collapsed to a singlet.
of arms present in 12, 13, and 1g. The absorption intensities
increase regularly, however, on proceeding from 12 to 13
and further to 1g (Figure 1). The push-pull effect causes
an intramolecular charge transfer (ICT), which results in a
bathochromic shift of the lowest-energy electron transition:
the parent system 1a has an absorption maximum at λ ϭ
327 nm, the methoxy derivative 1b at λ ϭ 356 nm and the
p-dimethylamino compound 1d at λ ϭ 425 nm (measure-
ments in CH2Cl2). Extension of the conjugation in the
series 1g, 2b, 3, and 4 leads to a systematic bathochromic
and hyperchromic effect (Figure 2). The convergence limit,
calculated on the basis of exponential functions[39] is pre-
dicted as λϱ ϭ 427Ϯ3 nm (Figure 3). Interestingly, the effec-
tive conjugation length nECL ϭ 7 is smaller than that in the
open-chained OPV series, where nECL ϭ 11 was estab-
lished.[19]
Figure 2. UV/Vis spectra of the series 1g, 2b, 3, and 4 in CH2Cl2
Figure 1. UV/Vis spectra of the mono-, di-, and tristyryl-substi-
tuted 1,3,5-triazines 12, 13, and 1g, respectively (measured in
CH2Cl2)
Figure 3. Long-wavelength absorption maxima of 1g, 2b, 3, and 4
in CH2Cl2; dependence on the number of repeat units n and the
convergence to λϱ (n Ǟ ϱ)
All of the spectroscopic results discussed so far refer to
Figure 4 depicts the change in the long-wavelength ab-
neutral solutions in tri- or dichloromethane. What effects sorption A of 1d in CHCl3 that is caused by protonation
1
occur when trifluoroacetic acid (TFA) is added? We ob- with TFA. The corresponding H NMR spectra in CDCl3
served that the yellow solution of 1d in chloroform first reveal an increasing low-field shift and broadening of all of
turned violet upon the initial addition of TFA and then the signals, as a result of proton exchange processes, upon
became colorless with further addition. We studied the aci- increasing the concentration of TFA. The 13C NMR meas-
1
dochromic behavior by UV/Vis, H NMR, and 13C NMR urements are even more instructive. A two-dimensional
spectroscopy.
shift correlation (HMBC) experiment using the violet solu-
4176
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Star-Shaped Compounds Having 1,3,5-Triazine Cores
FULL PAPER
tion reveals intense high-field shifts for the quaternary car- degree of intramolecular charge transfer (ICT) and then to
bon atoms in the 1,3,5-triazine ring and their adjacent olef- the disappearance of the push-pull effect that causes the
inic carbon atoms (∆δ ϭ Ϫ5.3 and Ϫ7.5 ppm, respectively); ICT. The complete disappearance of the band having a
the other olefinic carbon atoms undergo low-field shifts maximum at 549 nm implies that protonation of the di-
(∆δ ϭ 6.6 ppm). This behavior is typical of the protonation methylamino groups occurs in all three arms; otherwise, an
of an aromatic N-heterocycle.[40] The 13C NMR signals be- unprotonated arm would still be expected to exhibit an ICT.
gin to broaden, particularly those that are shifted to high
All six nitrogen atoms are involved in the proton ex-
field; further addition of TFA causes these signals to disap- change mechanisms, which are fast on the NMR time scale.
pear into the noise. Obviously, the protonation of 1d occurs Thus, the protonated forms of compound 1d never appear
on the 1,3,5-triazine ring first and then on the dimethylam- to lose their threefold symmetry (point group: D3h).
ino groups. To support this explanation is the observation
The protonation of the alkoxy-substituted compounds
that the signal of the methyl group is almost unaffected in 1g, 2b, 3, and 4 with TFA takes place solely at the central
the violet solution but it is shifted to lower field [∆δ(1H) ϭ 1,3,5-triazine ring. The bathochromic shifts amount to 82,
0.42 ppm] in the colorless solution. Scheme 7 illustrates the 92, 93, and 91 nm, respectively, and then remain constant
protonation process, which leads first to an increase in the upon further addition of TFA to the solutions in CH2Cl2.
The convergence for n Ǟ ϱ in the protonated series leads
to λϱ ϭ 515 nm; this limiting value is reached at an effective
conjugation length of nECL ϭ 6.
Finally, we note that compounds 1Ϫ4, which have altog-
ether nine long, flexible, alkoxy chains, form liquid crystals
(columnar mesophases, whose helical arrangements are
now under investigation). The clearing points of these
phases are described in the Exp. Sect.
Summary and Conclusion
The 1,3,5-triazine derivatives 1Ϫ4 having styryl or OPV
arms on C-2, C-4, and C-6 can be prepared readily by con-
densation reactions between 2,4,6-trimethyl-1,3,5-triazine
(5) and the corresponding aldehydes 6. The push-pull
Figure 4. Protonation of 1d in CHCl3/CF3COOH: a) yellow, neu-
character of compounds 1Ϫ4 having terminal donor sub-
tral, 5.068·10Ϫ6  solution of 1d in CHCl3; b) violet solution of 1dЈ
stituents is evidenced by the polarization of the olefinic
bridges observed in the 1H and 13C NMR spectroscopic
data and, particularly, in the UV/Vis spectra that prove the
existence of intramolecular charge transfer (ICT). Ex-
tending the conjugation in the three arms leads to a rela-
tively fast convergence of the absorption to λϱ ϭ 427 nm.
We predict the effective conjugation length (nECL) to be 7
repeat units. Initial protonation on the central 1,3,5-triazine
ring increases the ICT (evidenced by the corresponding ba-
thochromic shift); further protonation on the dimethylam-
ino groups of 1d leads to the disappearance of the push-
pull character and, hence, to a hypsochromic effect. The
acidochromic behavior of 1d is expressed by its color
change from yellow to violet and then to colorless. The
compounds 1Ϫ4, which have nine hexyloxy chains, form
thermotropic columnar mesophases. Moreover, these star-
shaped compounds should exhibit interesting non-linear
optical (NLO) properties.[16,41]
(4-fold excess of TFA); and c) colorless solution of 1dЈЈ (20-fold
excess of TFA)
Experimental Section
General Remarks: UV/Vis: Zeiss MCS 320/340; CHCl3 or CH2Cl2
as solvents. 1H and 13C NMR: Bruker Avance 600, ARX 400,
AMX 400 and AC 300; CDCl3/TMS as internal standard. IR: Nic-
olet 5SXB, LOT-Oriel ATR unit or PerkinϪElmer GX. MS: Finni-
gan MAT 95 (FD; accelerating voltage 5 kV) and Varian MAT
Scheme 7. Protonation of 1d in CDCl3/CF3COOH yields the violet
species 1dЈ and the colorless form 1dЈЈ (R represents the three equal
arms of 1d, 1dЈ, and 1ЈЈ)
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H. Meier, H. C. Holst, A. Oehlhof
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CH7A (EI; 70 eV). Elemental analyses: Microanalytical Labora-
1273, 1255, 1212, 1179, 1114, 1045, 1019, 980, 879, 829, 788, 666,
tory of the Institute of Organic Chemistry, University of Mainz. 652, 504 cmϪ1. FD MS: m/z (%) ϭ 430 (100) [Mϩ]. C30H27N3
DSC: PerkinϪElmer DSC 7 (clearing points, Tcl, measured on se-
cond heating curve). Melting points: Stuart Scientific SMP/3; un-
corrected.
(429.6): calcd. C 83.88, H 6.34, N 9.78; found C 84.12, H 6.19,
N 9.74.
2,4,6-Tris[(E)-2-{4-[(diethoxyphosphoryl)methyl]phenyl}ethenyl]-
1,3,5-triazine (1f): A mixture of NBS (623 mg, 3.5 mmol), 1e
(450 mg, 1.0 mmol) and repeatedly added small portions of AIBN
was heated under reflux in dry CCl4 (50 mL). When the reaction
reached completion, as indicated by the amount of succinimide ap-
pearing at the surface, the mixture was filtered, the volatile parts
were evaporated, and the residue was treated with triethyl phos-
phite (10 mL, 9.69 g, 58.3 mmol). After heating at 150 °C for 5 h
with continuous distillation of the bromoethane that formed, the
excess triethyl phosphite was removed and the residue purified by
column chromatography (7 ϫ 50 cm of SiO2; EtOAc/EtOH, 7:1) to
yield a highly viscous colorless oil; yield: 300 mg (40%). IR (TR):
ν˜ ϭ 2982, 2908, 1680, 1631, 1607, 1568, 1503, 1443, 1421, 1375,
1292, 1231, 1182, 1163, 1097, 1048, 1018, 962, 854 cmϪ1. 1H NMR
(CDCl3): δ ϭ 1.24 (t, 18 H, CH3), 3.18 [d, 2J(H,P) ϭ 21.9 Hz, 6
H, CH2P], 4.02 (m, 12 H, OCH2), 7.13 (d, 3J ϭ 16.0 Hz, 3 H, inner
olefinic H), 7.35, 7.63 (AAЈBBЈ, 12 H, aromat. H), 8.24 (d, 3J ϭ
16.0 Hz, 3 H, outer olefinic H) ppm. 13C NMR (CDCl3): δ ϭ 16.3
[d, 3J(C,P) ϭ 6.1 Hz, CH3], 33.8 [d, 1J(C,P) ϭ 138.1 Hz, CH2P],
62.2 [d, 2J(C,P) ϭ 6.9 Hz, OCH2], 126.2 (inner olefinic CH), 128.3,
130.3 [d, 3J(C,P) ϭ 6.1 Hz, aromat. CH], 133.7 [d, 2J(C,P) ϭ
General Procedure for the Preparation of the 2,4,6-Tristyryl-1,3,5-
triazines 1a؊e: Aldehyde 6a, 6b, 6d, 6e (commercially available), or
6c[43] in methanol (25 mL) was added to 2,4,6-trimethyltriazine
(5)[42] (310 mg, 2.52 mmol) dissolved in 20% methanolic KOH
(25 mL, 7.56Ϫ10.08 mmol). The reaction mixture was stirred under
reflux until TLC (SiO2; toluene) indicated the complete consump-
tion of 5 (3Ϫ6 d). After cooling to 5 °C, the precipitate that formed
was filtered off and carefully washed with cold methanol. Further
purification was achieved by column chromatography (4 ϫ 40 cm
of SiO2; toluene or diethyl ether) and/or recrystallization.
2,4,6-Tris[(E)-2-phenylethenyl]-1,3,5-triazine (1a): Colorless powder,
yield 87%, m.p. 229 °C (ref.[34] 224Ϫ226 °C). Identification was
made by comparison with an authentic sample.[21,22] UV/Vis
(CH2Cl2): λmax ϭ 327 nm; log ε ϭ 5.04.
2,4,6-Tris[(E)-2-(4-methoxyphenyl)ethenyl]-1,3,5-triazine (1b): Yel-
lowish needles, yield 94%, m.p. 228 °C. IR (TR): ν˜ ϭ 3034, 3004,
2964, 2934, 2840, 1633, 1601, 1572, 1496, 1441, 1420, 1371, 1315,
1304, 1288, 1246, 1167, 1111, 1028, 972, 872, 836, 797, 767 cmϪ1
.
UV/Vis (CH2Cl2): λmax ϭ 356 nm; log ε ϭ 5.04. FD MS: m/z (%) ϭ
477 (100) [Mϩ]. C30H27N3O3 (477.6): calcd. C 75.45, H 5.70, N
8.80; found C 75.31, H 5.88, N 8.72.
5
9.9 Hz), 134.2 [d, J(C,P) ϭ 3.8 Hz, aromat. Cq], 141.5 (outer olef-
inic CH), 171.3 (C-2) ppm. FD MS: m/z (%) ϭ 838 (100) [Mϩ].
C42H54N3O9P3 (837.8): calcd. C 60.21, H 6.50, N 5.02; found C
59.87, H 6.81, N 4.93.
2,4,6-Tris{(E)-2-[4-(hexyloxy)phenyl]ethenyl}-1,3,5-triazine
(1c):
Yellow powder, yield 55%, m.p. 94 °C. IR (TR): ν˜ ϭ 2955, 2941,
2921, 2868, 2854, 1628, 1605, 1573, 1501, 1474, 1423, 1407, 1380,
1307, 1295, 1246, 1171, 1119, 1059, 1030, 979, 876, 833, 791, 724
cmϪ1. UV/Vis (CH2Cl2): λmax ϭ 361 nm; log ε ϭ 5.02. FD MS: m/
z (%) ϭ 688 (100) [M ϩ Hϩ]. C45H57N3O3 (687.9): calcd. C 78.56,
H 8.35, N 6.11; found C 78.23, H 8.61, N 5.88.
2,4,6-Tris[(E)-2-(4-{(E)-2-[4-(hexyloxy)phenyl]ethenyl}phenyl)-
ethenyl]-1,3,5-triazine (2a):
A mixture of triphosphonate 1f
(160 mg, 0.214 mmol) and aldehyde 6c (288 mg, 1.4 mmol), dis-
solved in dry DMF (10 mL), was added slowly at room temperature
to a suspension of KOC(CH3)3 (170 mg, 1.5 mmol) in dry DMF
(10 mL). The stirred reaction mixture turned blue and then, some-
what later, green. After 2 h, the temperature was raised to 50 °C
and kept for 30 min before methanol (80 mL) was added. A yellow
precipitate was formed that was recrystallized from CH2Cl2/MeOH
(1:1). The product 2a is a brilliant yellow powder (34 mg, 18%),
m.p. 197 °C. IR (TR): ν˜ ϭ 3023, 2924, 2854, 1625, 1606, 1594,
1574, 1556, 1499, 1470, 1416, 1402, 1372, 1302, 1292, 1271, 1247,
1218, 1172, 1109, 1028, 960, 937, 879, 863, 833, 726 cmϪ1. UV/Vis
(CH2Cl2): λmax ϭ 400 nm; log ε ϭ 5.41. 1H NMR (CDCl3):[37] δ ϭ
0.90 (t, 9 H, CH3), 1.34 (m, 12 H, CH2), 1.46 (m, 6 H, CH2), 1.78
(m, 6 H, CH2), 3.97 (t, 6 H, OCH2), 6.88, 7.44 (AAЈBBЈ, 12 H,
outer aromat. H), 6.96, 7.12 (AB, 3J ϭ 16.2 Hz, 6 H, outer olefinic
H), 7.13, 8.25 (AB, 3J ϭ 15.8 Hz, 12 H, inner olefinic H), 7.52,
7.65 (AAЈBBЈ, 12 H, inner aromat. H) ppm. 13C NMR (CDCl3):[37]
δ ϭ 14.0 (CH3), 22.6, 25.7, 29.2, 31.6 (CH2), 68.1 (OCH2), 114.7,
127.9 (outer aromat. CH), 125.7, 129.5 (outer olefinic CH), 125.7,
141.1 (inner olefinic CH), 126.6, 128.6 (inner aromat. CH), 129.6,
134.3, 139.3 (aromat. Cq), 159.2 (CqO), 171.2 (C-2) ppm. FD MS:
m/z (%) ϭ 995 (100) [M ϩ Hϩ], 498 (20) [M2ϩ]. C69H75N3O3
(994.4): calcd. C 83.34, H 7.60, N 4.23; found C 83.11, H 7.89,
N 4.17.
2,4,6-Tris{(E)-2-[(4-dimethylamino)phenyl]ethenyl}-1,3,5-triazine
(1d): Violet crystals, yield 39%, m.p. 252 °C. IR (TR): ν˜ ϭ 2885,
2852, 2800, 1623, 1596, 1553, 1526, 1484, 1443, 1431, 1413, 1380,
1354, 1279, 1258, 1234, 1214, 1165, 1123, 1067, 1047, 977, 967,
947, 873, 860, 818, 792 cmϪ1. UV/Vis (CH2Cl2): λmax ϭ 425; log
ε ϭ 5.10. FD MS: m/z (%) ϭ 517 (100) [Mϩ]. C33H36N6 (516.7):
calcd. C 76.71, H 7.02, N 16.27; found C 76.64, H 7.06, N 16.30.
After a reaction time of 7 d, the raw material provided a second
fraction (chromatography on 4 ϫ 25 cm of SiO2; CH2Cl2/EtOAc,
19:1) — the twofold condensation product 1dЈ — which became
the major product (52%) when the molar ratio 5/6c was 1:2.
2,4-Bis{(E)-2-[(4-dimethylamino)phenyl]ethenyl}-6-methyl-1,3,5-tri-
˜
azine (1dЈ): Red solid, m.p. 169 °C. IR (TR): ν ϭ 2889, 2852, 2800,
1624, 1598, 1553, 1494, 1429, 1385, 1345, 1290, 1269, 1253, 1178,
1165, 1122, 1062, 975, 945, 869, 817, 793 cmϪ1. UV/Vis (CH2Cl2):
λ
max ϭ 421 nm; log ε ϭ 4.93. 1H NMR (CDCl3): δ ϭ 2.61 (s, 3 H,
6-CH3), 3.02 (s, 12 H, NCH3), 6.69, 7.54 (AAЈBBЈ, 8 H, aromat.
H), 6.87, 8.17 (AB, 3J ϭ 16.0 Hz, olefinic H) ppm. 13C NMR
(CDCl3): δ ϭ 25.8 (6-CH3), 40.2 (NCH3), 111.9, 129.8 (aromat.
CH), 120.8, 142.0 (olefinic CH), 123.6, 151.5 (aromat. Cq), 171.4
(C-2, C-4), 175.4 (C-6) ppm. FD MS: m/z (%) ϭ 385 (100) [Mϩ]. 4-(Bromomethyl)benzaldehyde (8): Prepared and identified accord-
C24H27N5 (385.5): calcd. C 74.77, H 7.06, N 18.17; found C 74.68, ing to the literature by reaction of 4-bromobenzonitrile (7) with DI-
H 6.95, N 18.37.
BAH.[44]
2,4,6-Tris[(E)-2-(4-methylphenyl)ethenyl]-1,3,5-triazine (1e): Color-
1-(Bromomethyl)-4-(diethoxymethyl)benzene (9): A mixture of trie-
less powder, yield 96%, m.p. 231 °C. IR (KBr): ν˜ ϭ 3050, 3023, thoxymethane (9 mL, 8.02 g, 54.1 mmol), 8 (1.05 g, 5.3 mmol) and
2919, 2858, 1634, 1609, 1589, 1514, 1412, 1400, 1377, 1321, 1289, Dowex 50WX 8 (1.0 g) was stirred in dry EtOH (30 mL) for 3 h at
4178
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 4173Ϫ4180

Star-Shaped Compounds Having 1,3,5-Triazine Cores
FULL PAPER
room temperature. Half of the solvent was removed, Na2CO3
(1.0 g) was added, and the mixture then stirred for a further 10 min.
The volatile parts of the filtered solution were then removed. The
raw product (1.29 g, 100%), a colorless oil, was used for the next
step without further purification.
NMR (CDCl3):[37] δ ϭ 0.90 (2 t, 27 H, CH3), 1.34 (m, 36 H, CH2),
1.48 (m, 18 H, CH2), 1.75 (m, 6 H, CH2), 1.81 (m, 12 H, CH2),
3.97 (t, 6 H, OCH2), 4.01 (t, 12 H, OCH2), 6.70 (s, 6 H, aromat.
3
H), 6.95, 7.02 (AB, J ϭ 16.0 Hz, 6 H, outer olefinic H), 7.10, 7.16
3
3
(AB, J ϭ 16.4 Hz, 6 H, middle olefinic H), 7.13, 8.23 (AB, J ϭ
15.6 Hz, 6 H, inner olefinic H), 7.48 (‘‘s’’, 12 H, aromat. H, middle
benzene ring), 7.54, 7.65 (AAЈBBЈ, 12 H, aromat. H, inner benzene
ring) ppm. 13C NMR (CDCl3):[37] δ ϭ 14.0, 14.1 (CH3), 22.6, 22.7,
25.8, 25.8, 29.4, 30.3, 31.6, 31.8 (CH2), 69.1, 73.5 (OCH2), 105.1,
126.7, 126.9, 127.0, 128.6 (aromat. CH), 126.0, 141.0 (inner olefinic
CH), 127.1, 129.0 (outer olefinic CH), 127.6, 129.4 (middle olefinic
CH), 132.4, 134.7, 136.2, 137.1, 138.9 (aromat. Cq), 138.3, 153.3
(CqO), 171.2 (C-1) ppm. FD MS: m/z (%) ϭ 1901 (100) [Mϩ], 951
(77) [M2ϩ]. C129H165N3O9 (1901.7): calcd. C 81.47, H 8.75, N 2.21;
found C 81.51, H 8.66, N 2.15.
Diethyl [4-(Diethoxymethyl)benzyl]phosphonate (10): A mixture of
triethyl phosphite (2.0 mL, 1.94 g, 11.6 mmol) and 9 (1.25 g,
5.1 mmol) was heated at 160 °C. The generated bromoethane was
distilled off, as was the excess triethyl phosphite after a reaction
time of 1 h, and the residue was purified by column chromatogra-
phy (16 ϫ 5 cm of basic Al2O3; EtOAc). Yield: 1.20 g (71%) of a
colorless oil. Identification by comparison with an authentic
sample.[30,38] Preparation of the aldehydes 11aϪd was performed
according to the literature: 11a,[45,46] 11bϪd.[30]
General Procedure for the Preparation of the 1,3,5-Triazine Deriva-
tives 1g, 2b, 3, and 4: A solution of 5 (61.5 mg, 0.50 mmol), alde-
hyde 11aϪd (1.50Ϫ2.00 mmol) and KOC(CH3)3 (168 mg,
1.50 mmol) in dry THF (10Ϫ20 mL) was heated under reflux
(monitored by TLC: SiO2; CH2Cl2). The mixture was cooled to 0
°C and treated with MeOH until precipitation of the product was
complete. Column chromatography (4 ϫ 40 cm of SiO2; CH2Cl2)
yielded the pure target compounds.
2,4,6-Tris[(E)-2-{4-[(E)-2-{4-[(E)-2-(4-{(E)-2-[3,4,5-tris(hexyloxy)-
phenyl]ethenyl}phenyl)ethenyl]phenyl}ethenyl]phenyl}ethenyl]-1,3,5-
triazine (4): Yield: 15%, intensely yellow powder that does not give
an isotropic melt below 300 °C. IR (KBr): ν˜ ϭ 3025, 2955, 2929,
2858, 1629, 1591, 1577, 1505, 1468, 1431, 1378, 1342, 1233, 1175,
1119, 959, 836, 625, 547 cmϪ1. UV/Vis (CH2Cl2): λmax ϭ 420 nm;
log ε ϭ 5.46. 1H NMR (CDCl3):[37] δ ϭ 0.90 (2 t, 27 H, CH3), 1.33
(m, 36 H, CH2), 1.47 (m, 18 H, CH2), 1.74 (m, 6 H, CH2), 1.80
(m, 12 H, CH2), 3.95 (t, 6 H, OCH2), 4.00 (t, 12 H, OCH2), 6.69
2,4,6-Tris{(E)-2-[3,4,5-tris(hexyloxy)phenyl]ethenyl}-1,3,5-triazine
3
(s, 6 H, aromat. H), 6.94, 7.00 (AB, J ϭ 16.0 Hz, 6 H, outer olef-
(1g): Yield: 79%, brilliant yellow wax with clearing point Tcl
109.5 °C. IR (TR): ν˜ ϭ 2954, 2927, 2858, 1633, 1579, 1496, 1467,
1431, 1379, 1327, 1291, 1241, 1111, 972, 926, 876, 835, 725 cmϪ1
ϭ
inic H), 7.08, 7.14 (AB, 3J ϭ 16.0 Hz, 6 H, second inner olefinic
H), 7.11, 8.22 (AB, 3J ϭ 15.7 Hz, 6 H, inner olefinic H), 7.08 (‘‘s’’,
6 H, second outer olefinic H), 7.46 (‘‘s’’, 12 H, aromat. H), 7.48
(‘‘s’’, 12 H, aromat. H), 7.53, 7.64 (AAЈBBЈ, 12 H, aromat. H, inner
benzene ring) ppm. 13C NMR (CDCl3):[37] δ ϭ 14.1, 14.1 (CH3),
22.6, 22.7, 25.8, 25.8, 29.5, 29.7, 30.4, 31.7, 31.8 (CH2), 69.1, 73.5
(OCH2), 105.1, 126.8, 127.0, 127.1, 128.6 (aromat. CH, partly
superimposed), 126.0, 140.6 (inner olefinic CH), 127.1, 128.9 (outer
olefinic CH), 127.7, 129.1 (second inner olefinic CH), 127.8, 128.2
(second outer olefinic CH), 132.4, 134.6, 136.2, 136.3, 136.7, 136.7,
138.6 (aromat. Cq), 138.4, 153.3 (CqO), 170.8 (C-1) ppm. FD MS:
m/z (%) ϭ 2208 (100) [Mϩ], 1104 (59) [M2ϩ]. C153H183N3O9
(2208.2): calcd. C 83.22, H 8.35, N 1.90; found C 83.10, H 8.53,
N 1.81.
.
UV-Vis (CH2Cl2): λmax ϭ 366 nm; log ε ϭ 4.90. 1H NMR
(CDCl3):[37] δ ϭ 0.90 (2 t, 27 H, CH3), 1.33 (m, 36 H, CH2), 1.49
(m, 18 H, CH2), 1.74 (m, 6 H, CH2), 1.82 (m, 12 H, CH2), 3.99 (t,
6 H, OCH2), 4.01 (t, 12 H, OCH2), 6.88 (s, 6 H, aromat. CH), 7.00
3
3
(d, J ϭ 15.7 Hz, 3 H, inner olefinic H), 8.15 (d, J ϭ 15.7 Hz, 3
H, outer olefinic H) ppm. 13C NMR (CDCl3):[37] δ ϭ 14.0, 14.1
(CH3), 22.6, 22.7, 25.7, 25.8, 29.3, 30.3, 31.6, 31.7 (CH2), 69.2,
73.6 (OCH2), 106.7 (aromat. CH), 125.1 (inner olefinic CH), 130.5
(aromat. Cq), 140.2, 153.3 (CqO), 141.8 (outer olefinic CH), 171.2
(C-1) ppm. FD MS: m/z (%) ϭ 1289 (100) [M ϩ Hϩ]. C81H129N3O9
(1288.9): calcd. C 75.48, H 10.09, N 3.26; found C 75.51, H 10.16,
N 3.21.
2,4-Dimethyl-6-{(E)-2-[3,4,5-tris(hexyloxy)phenyl]ethenyl}-1,3,5-tri-
azine (12): A solution of 11a (406 mg, 1.0 mmol) in MeOH (4 mL)
was added slowly at 0 °C to a solution of KOC(CH3)3 (168 mg,
1.5 mmol) and 5 (123.2 mg, 1.0 mmol) in dry MeOH (10 mL).
After vigorous stirring for 30 min, the reaction mixture was kept
at room temperature overnight. The volatile parts were removed
and the residue was purified by column chromatography (5 ϫ
20 cm of SiO2; CH2Cl2/EtOAc, 10:1). After the first fractions
eluted with small amounts of unchanged 11a, 13, and 1g, the title
compound 12 was obtained as a yellow-green viscous oil. Yield:
200 mg (39%). UV/Vis (CH2Cl2): λmax ϭ 362 nm; log ε ϭ 4.47. 1H
NMR (CDCl3): δ ϭ 0.87 (t, 6 H, CH3), 0.88 (t, 3 H, CH3), 1.31
(m, 12 H, CH2), 1.45 (m, 6 H, CH2), 1.72 (m, 2 H, CH2), 1.79 (m,
4 H, CH2), 2.60 (s, 6 H, CH3), 3.97 (t, 6 H, OCH2), 6.82 (s, 2 H,
aromat. H), 6.91, 8.06 (AB, 3J ϭ 15.9 Hz, 2 H, olefinic H) ppm.
13C NMR (CDCl3): δ ϭ 14.0, 14.1 (CH3), 22.6, 22.6, 25.6, 25.7,
29.2, 30.2, 31.5, 31.6 (CH2), 25.6 (2-CH3), 69.0, 73.5 (OCH2), 106.5
(aromat. CH), 124.3, 142.5 (olefinic CH), 130.2 (aromat. Cq),
140.1, 153.2 (CqO), 171.0 (C-6), 175.9 (C-2) ppm. FD MS: m/z
(%) ϭ 512 (100) [M ϩ Hϩ]. C31H49N3O3 (511.7): calcd. C 72.76,
H 9.65, N 8.21; found C 72.58, H 9.84, N 8.05.
2,4,6-Tris[(E)-2-(4-{(E)-2-[3,4,5-tris(hexyloxy)phenyl]ethenyl}-
phenyl)ethenyl]-1,3,5-triazine (2b): Yield: 61%, waxy yellow solid,
Tcl ϭ 96.0 °C. IR (TR): ν˜ ϭ 2952, 2926, 2856, 1627, 1599, 1578,
1558, 1499, 1467, 1430, 1375, 1342, 1317, 1243, 1176, 1111, 977,
956, 833 cmϪ1. UV/Vis (CH2Cl2): λmax ϭ 398 nm; log ε ϭ 5.165.
1H NMR (CDCl3):[37] δ ϭ 0.90 (2 t, 27 H, CH3), 1.34 (m, 36 H,
CH2), 1.49 (m, 18 H, CH2), 1.75 (m, 6 H, CH2), 1.82 (m, 12 H,
CH2), 3.97 (t, 6 H, OCH2), 4.02 (t, 12 H, OCH2), 6.72 (s, 6 H,
aromat. CH), 6.97, 7.08 (AB, 3J ϭ 16.2 Hz, 6 H, outer olefinic H),
7.15, 8.25 (AB, 3J ϭ 15.9 Hz, 6 H, inner olefinic H), 7.61, 7.84
(AAЈBBЈ, 12 H, aromat. H) ppm. 13C NMR (CDCl3):[37] δ ϭ 14.0,
14.1 (CH3), 22.6, 22.7, 25.8, 25.8, 29.4, 30.3, 31.6, 31.8 (CH2), 69.2,
73.5 (OCH2), 105.3, 126.8, 128.6 (aromat. CH), 125.9, 141.1 (inner
olefinic CH), 126.9, 130.1 (outer olefinic CH), 132.2, 134.5, 139.1
(aromat. Cq), 138.6, 153.3 (CqO), 171.2 (C-1) ppm. FD MS: m/z
(%) ϭ 1596 (100) [M ϩ Hϩ], 789 (41) [M2ϩ]. C105H147N3O9
(1595.3): calcd. C 79.05, H 9.29, N 2.63; found C 78.91, H 9.46,
N 2.51.
2,4,6-Tris[(E)-2-{4-[(E)-2-(4-{(E)-2-[3,4,5-tris(hexyloxy)phenyl]-
ethenyl}phenyl)ethenyl]phenyl}ethenyl]-1,3,5-triazine (3): Yield:
44%, orange solid, Tcl ϭ 233.3 °C. IR (TR): ν˜ ϭ 3024, 2924, 2855,
1627, 1593, 1577, 1499, 1468, 1429, 1374, 1341, 1225, 1175, 1109,
954, 832 cmϪ1. UV/Vis (CH2Cl2): λmax ϭ 414; log ε ϭ 5.35. 1H
2-Methyl-4,6-bis{(E)-2-[3,4,5-tris(hexyloxy)phenyl]ethenyl}-1,3,5-
triazine (13): The procedure described for the preparation of 12
Eur. J. Org. Chem. 2003, 4173Ϫ4180
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4179

H. Meier, H. C. Holst, A. Oehlhof
FULL PAPER
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oil (150 mg, 32%). UV/Vis (CH2Cl2): λmax ϭ 362 nm; log ε ϭ 4.75.
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31.5, 31.7 (CH2), 25.8 (2-CH3), 69.0, 73.5 (OCH2), 106.5 (aromat.
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H. Meier, D. Ickenroth, Eur. J. Org. Chem. 2002, 1745Ϫ1749
and references cited therein.
Received March 3, 2003
4180
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 4173Ϫ4180