Preparation of 1,2,5,6,9,10-hexaalkoxyhexahelicenes

Article abstract of DOI:10.5560/ZNB.2013-3170

1,2,5,6,9,10-Hexaalkoxyhexahelicenes 3 represent [3]star compounds with a helical core. A multistep synthetic concept for 3 is discussed, in which the final step 16→3 is a twofold oxidative photocyclization. The linearly conjugated compounds 16 contain st

Full text of DOI:10.5560/ZNB.2013-3170

Preparation of 1,2,5,6,9,10-Hexaalkoxyhexahelicenes
Manfred Schwertel, Sabine Hillmann and Herbert Meier
Institute of Organic Chemistry, University of Mainz, Duesbergweg 10–14, 55099 Mainz,
Germany
Reprint requests to Prof. Dr. H. Meier. Fax: +49 (0)6131-3925396. E-mail: hmeier@uni-mainz.de
Z. Naturforsch. 2013, 68b, 1347 – 1355 / DOI: 10.5560/ZNB.2013-3170
Received June 26, 2013
1,2,5,6,9,10-Hexaalkoxyhexahelicenes 3 represent [3]star compounds with a helical core. A multi-
step synthetic concept for 3 is discussed, in which the final step 16 → 3 is a twofold oxidative photo-
cyclization. The linearly conjugated compounds 16 contain stilbene and vinylnaphthalene units.
Key words: Helicenes, Photocyclization, Wittig–Horner Reaction, Siegrist Reaction
Introduction
in this case. We conceived a multi-step procedure,
which starts from benzene and naphthalene deriva-
[3]Star compounds, which consist of conjugated tives.
aromatic cores and three, six or nine alkoxy groups,
represent interesting structures for materials sci- Results and Discussion
ence [1]. 2,3,6,7,10,11-Hexaalkoxytriphenylenes (1)
are prominent examples (Fig. 1). From their first prepa-
Scheme 1 summarizes the preparation of the 2-{2-
rations [2, 3] till our days [4 – 9], a large variety of [4-(2-phenylvinyl)phenyl]vinyl}naphthalenes 16a, b,
compounds 1 have been thoroughly studied. Much which were chosen as precursors for the desired hexa-
less is known about 1,2,5,6,9,10-hexaalkoxycoronenes helicenes 3.
(2) [10, 11], and nothing is known about 1,2,5,6,9,10-
3-Methylbenzene-1,2-diol (4) was alkylated twice
hexaalkoxyhexahelicenes (3). In contrast to 1 and under phase transfer conditions [13, 14]. We used
2, compound 3 has a non-planar, chiral polycyclic long alkyl chains to get high solubilities throughout
core. Many mesophases are known for compounds the whole reaction sequence. The obtained 3-methyl-
1, some for systems 2. This arises the question: 1,2-dialkoxybenzenes 6a, b were subjected to a Bou-
Do chiral thermotropic liquid crystalline phases veault formylation to 7a, b. The formylation was nei-
(LC) exist for 3? Due to the lack of symmetry, ther regioselective nor chemoselective; the CH3 group
the usual synthesis of hexahelicenes on the ba- was also attacked by DMF [15, 16]. Consequently the
sis of 2,7-distyrylnaphthalenes [12], is not useful yields of 7a, b were low. In a second reaction se-
Fig. 1.
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M. Schwertel et al. · Preparation of 1,2,5,6,9,10-Hexaalkoxyhexahelicenes
Scheme 1. Preparation of the 2-{(E)-2-[4-((E)-2-phenylvinyl)phenyl]vinyl}naphthalenes 16a, b: i) KOH, Aliquat 336, 1,4-
dioxane; ii) 1. BuLi, TMEDA, 2. DMF; iii) NBS, CCl4; iv) P(OC2H5)3, 160 ◦C; v) NaH, DME; vi) K2CO3, acetone; vii)
LiAlH4; viii) DDQ, 1,4-dioxane; ix) C6H5-NH2, CHCl3; x) KOC(CH3)3, DMF.
quence, 6a, b were transformed to the phosphonates
The naphthalene moiety of 16a, b was synthesized
9a, b via the bromides 8a, b [14]. Wittig–Horner re- on the basis of the ester 11 [17, 18], which was alky-
actions 7a+9a and 7b+9b gave the (E)-configured stil- lated with the bromoalkanes 5a, b to obtain 12a,
benes 10a and 10b, respectively.
b. Reduction with LiAlH4 yielded the alcohols 13a,
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M. Schwertel et al. · Preparation of 1,2,5,6,9,10-Hexaalkoxyhexahelicenes
1349
Scheme 2. Photoisomerization of (E,E)-16a, b and subsequent cyclizations and oxidations to the hexahelicenes 3a, b: i) I2,
.
b, which were gently oxidized by 2,3-dicyano-5,6- in favor of the (E)-configuration is so high that the (Z)-
dichloro-1,4-benzoquinone (DDQ) to the aldehydes isomers could not be detected in the NMR spectra of
14a, b. The reaction with aniline gave then the Schiff the crude reaction products 16a, b [20].
bases 15a, b. In contrast to the left branch of the syn-
Irradiation of (E,E)-16a, b led to the formation of
thetic Scheme 1, all yields in the right branch are very the two possible (E,Z)-isomers and the (Z,Z)-isomer,
high. The four steps from 11 to 15a have for example which subsequently underwent cyclization and oxida-
an overall yield of 88 × 0.94 × 0.95 × 100 = 78.6%. tion to 17a, b and/or 18a, b (Scheme 2). The sec-
Siegrist reactions [19] of 10a+15a and 10b+15b gave ond photocyclization and oxidation gave 3a and 3b,
then 16a and 16b, respectively. The stereoselectivity respectively, in good overall yields. In principle, an
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M. Schwertel et al. · Preparation of 1,2,5,6,9,10-Hexaalkoxyhexahelicenes
1
Table 1. H NMR spectra of 3a and 3b in CDCl3, TMS as
internal standard. (δ values in ppm, coupling constants J in
Hz)
Proton (spin system)
3a
3b
3-H / 4-H (AB)
8.27 / 8.29
8.7
8.26 / 8.30
8.8
3J
7-H / 8-H (AB)
3J
8.35 / 8.39
8.8
8.32 / 8.38
8.8
11-H (A)
6.33
9.3
6.32
9.2
3J
12-H (B)
13-H (A)
3J
7.15
7.49
8.5
7.13
7.48
8.5
14-H (B)
15-H (C)
16-H (D)
3J
6.60
7.17
8.13
7.9
6.58
7.16
8.11
8.0
10-OCH2 (t)
1-, 2-, 5-, 6-, 9-OCH2 (m)
β-CH2 (m)
γ-CH2 (m)
δ-CH2 (m) and higher
CH3 (m)
3.86
3.83
3.84–4.43
1.86–2.03
1.55–1.75
1.20–1.48
0.84–0.97
3.95–4.45
1.80–2.06
1.51–1.80
1.15–1.51
0.81–1.00
of course any decomposition between −20 and −55 ◦C
could be excluded.
The hexahelicenes 3a, b belong to the point group
C1, they are chiral. Consequently they show ten aro-
matic CH signals, ten Cq and six CqO signals in the 13
C
1
NMR spectra. Most characteristic are their H NMR
signals (Table 1). The aromatic protons give three AB
and one ABCD spin patterns. The signals at highest
field in the aromatic region were found for 11-H at
δ = 6.33 and 6.32 ppm, respectively. The overlap of
Fig. 2. DSC curves of 3a and 3b, measured at a rate of
10 K min−1: H heating curve, C cooling curve.
unsubstituted system 16 would have four cyclization the terminal benzene rings and the high electron den-
modes, which can lead to four different condensed ben- sity, induced by the 10-OR groups, are the reason for
zenoid aromatics; however, the alkoxy groups in 16a, the resonance at unusually high field.
b block three cyclization routes, so that only the route
16a, b→3a, b remains. Iodine served as oxidant and
Conclusion
methyloxirane as scavenger for the generated hydro-
gen iodide [21]. At the stage of the not isolated inter-
The hexahelicenes 3a and 3b are the first examples
of [3]star compounds with a helical core consisting of
a hexahelicene structure. Their preparation in a mul-
tistep synthesis was based on the twofold oxidative
photocyclization of the linearly conjugated 2-(4-styryl-
styryl)naphthalenes 16a and 16b (Schemes 1 and 2).
mediates 17 and/or 18, photoisomerizations have to be
assumed.
The racemates 3a and 3b are pale-yellow oils which
solidify below −20 ◦C. Both compounds exhibit very
different DSC curves (Fig. 2); however, the formation
of thermotropic mesophases could be excluded by po-
larization microscopy. Liquid crystals are very rare in
the series of hexahelicenes [22, 23]. The broad peak
in the heating and cooling curve of 3a is unusual. It
can be possibly due to a superposition of several close-
Experimental Section
NMR spectra were recorded on a Bruker AM 400 spec-
lying phase transitions in the solid state. Impurities and trometer operating at 400 MHz for 1H and 100 MHz for 13C.
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M. Schwertel et al. · Preparation of 1,2,5,6,9,10-Hexaalkoxyhexahelicenes
1351
FD MS (5 kV) and EI MS (70 eV) measurements were per- C20H32O3 (320.5): calcd. C 74.96, H 10.06; found C 74.79,
formed with a Finnigan MAT 95 spectrometer. UV/Vis spec- H 9.82.
tra were obtained with a Zeiss MCS 320/340 diode array
spectrometer. Melting points were taken on a Bu¨chi appara-
2,3-Bis(dodecyloxy)-4-methylbenzaldehyde (7b)
tus and are uncorrected. A Perkin-Elmer DSC 7 instrument
served for the differential scanning calorimetry (DSC). Polar-
ization microscopy was performed with a Leitz Ortholux II
microscope. Elemental analyses were determined in the mi-
croanalytical laboratory of the Chemistry Department of the
University of Mainz.
Colorless oil, yield 1.29 g (12%). – 1H NMR (CDCl3):
δ = 0.84 – 0.95 (m, 6 H, CH3), 1.15 – 1.40 (m, 32 H, CH2),
1.40 – 1.53 (m, 4 H, CH2), 1.68 – 1.84 (m, 4 H, CH2), 2.27
(s, 3 H, CH3), 3.92 (t, 3J = 6.4 Hz, 2 H, OCH2), 4.07 (t, 3J =
6.4 Hz, 2 H, OCH2), 6.94/7.45 (AB, 3J = 8.0 Hz, 2 H, 5-H,
6-H), 10.32 (s, 1 H, CHO). – 13C NMR (CDCl3): δ = 14.0,
The synthetic sequence 4→6a, b→8a, b → 9a, b is de-
16.6 (CH3, partly superimposed), 22.6, 26.0, 26.1, 29.3, 29.4,
29.6, 30.1, 30.4, 31.9 (CH2, partly superimposed), 73.1, 75.2
(OCH2), 122.4 (C-5), 125.9 (C-6), 128.8 (C-1), 140.3 (C-
scribed elsewhere [14].
It was not necessary to isolate the intermediate bromo
compounds 8a, b. However, the oily compound 2,3-
4), 150.9 (C-3), 155.6 (C-2), 189.6 (CHO). – MS (EI): m/z
bis(hexyloxy)benzylbromide (8a) was checked for its pu-
(%) = 488 (14) [M]+, 152 (100). – C32H56O3 (488.8): calcd.
1
rity by NMR control. – H NMR (CDCl3): δ = 0.88 – 1.01
C 78.63, H 11.55; found C 78.51, H 11.60.
(m, 6 H, CH3), 1.25 – 1.45 (m, 8 H, CH2), 1.45 – 1.61 (m,
4 H, CH2), 1.75 – 1.94 (m, 4 H, CH2), 3.95 (t, 3J = 6.3 Hz, Wittig–Horner reaction of 7a, b and 9a, b for the
2 H, OCH2), 4.13 (t, 3J = 6.6 Hz, 2 H, OCH2), 6.83 (dd, preparation of 10a, b
3J = 6.8 Hz, 4J = 2.9 Hz, 1 H, 4-H), 6.89 – 7.02 (m, 2 H, 5-
Phosphonic acid ester 9a, b (2.1 mmol) in 40 mL of
H, 6-H). – 13C NMR (CDCl3): δ = 13.9, 14.0 (CH3), 22.5,
dry dimethoxyethane (DME) was dropped under nitrogen
22.6, 25.7, 25.8, 29.7, 30.3, 31.5, 31.7 (CH2), 28.3 ( CH2Br),
to NaH (420 mg, 10.5 mmol, 60% in paraffin) suspended
in 120 mL of dry DME. Aldehyde 7a, b (2.1 mmol) was
slowly added and the reaction mixture heated to reflux
for 6 h. Then 40 g crushed ice was added and the aqueous
113.7 (C-4), 122.3, 123.7 (C-5, C-6), 131.9 (C-1), 146.7,
152.3 (C-2, C-3). The only visible impurity was the starting
compound 6a, which does not react with triethyl phosphite.
Bouveault formylation of 6a, b to 7a, b
Benzene derivative 6a,
(22.0 mmol) and N,N0-
phase extracted with 100 mL of diethyl ether. The unified
organic phases were dried (MgSO4) and evaporated. The
residue was purified by column chromatography (3 × 40 cm
SiO2, petroleum ether, b. p. 40 – 70 ◦C / CH2Cl2 2 : 1).
b
tetramethylethylendiamine (TMEDA, 3.0 mL, 33.0 mmol)
were dissolved in 100 mL of dry and deoxygenated di-
ethyl ether. A 2.7 M solution of n-butyllithium in hexane
(21.0 mL, 33.0 mmol) was added and the mixture stirred
for 3 h at ambient temperature, before dimethylformamide
(DMF, 2.3 mL, 33.0 mmol) was added. After a further hour
at room temperature, first H2O (10 mL) and then 2 M HCl
(10 mL) were slowly dropped into the mixture. The organic
layer and the extract of the water layer (50 mL diethyl ether)
were unified, neutralized (NaHCO3), dried (MgSO4) and
evaporated. The residue was purified by column filtration
(5×40 cm SiO2, toluene or CH2Cl2).
1-{(E)-2-[2,3-Bis(hexyloxy)phenyl]vinyl}-2,3-bis(hexyloxy)-
4-methylbenzene (10a)
Yield 650 g (52%), viscous oil. – 1H NMR (CDCl3):
δ = 0.82 – 0.94 (m, 12 H, CH3), 1.20 – 1.38 (m, 16 H, CH2),
1.38 – 1.56 (m, 8 H, CH2), 1.63 – 1.88 (m, 8 H, CH2), 2.26
3
(s, 3 H, 4-CH3), 3.95 – 4.02 (m, 8 H, OCH2), 6.78 (d, J =
7.9 Hz, 1 H, 40-H), 6.89 (d, 3J = 8.1 Hz, 1 H, 5-H), 7.00
(t, 3J = 7.9 Hz, 1 H, 50-H), 7.24 (d, 3J = 7.6 Hz, 1 H, 60-
3
H), 7.25 (0s0, 2 H, olefin. H), 7.31 (d, J = 8.0 Hz, 1 H, 6-
H). – 13C NMR (CDCl3): δ = 14.1, 16.2 (CH3, partly su-
perimposed), 22.7, 22.8, 25.9, 30.5, 31.7, 31.8 (CH2, partly
superimposed), 68.7, 73.0, 73.7, 73.9 (OCH2), 112.3, 117.5,
120.3, 123.1, 123.7, 123.8, 125.8 (aromat. and olefin. CH),
130.5, 131.8, 132.4 (aromat. Cq), 146.4, 150.3, 151.1, 152.7
(CqO). – MS (FD): m/z (%) = 594 (100) [M]+. – C39H62O4
(594.9): calcd. C 78.74, H 10.50; found C 78.84, H 10.43.
2,3-Bis(hexyloxy)-4-methylbenzaldehyde (7a)
Colorless oil, yield 0.92 g (13%). – 1H NMR (CDCl3):
δ = 0.85 – 0.95 (m, 6 H, CH3), 1.23 – 1.40 (m, 8 H, CH2),
1.40 – 1.55 (m, 4 H, CH2), 1.70 – 1.90 (m, 4 H, CH2), 2.28
(s, 3 H, CH3), 3.92 (t, 3J = 6.5 Hz, 2 H, OCH2), 4.08 (t,
3J = 6.4 Hz, 2 H, OCH2), 6.95/7.45 (AB, 3J = 8.6 Hz, 2 H,
5-H, 6-H), 10.31 (s, 1 H, CHO). – 13C NMR (CDCl3): δ =
14.0, 16.4 (CH3, partly superimposed), 22.5, 22.6, 25.7, 25.7,
29.0, 30.2, 31.4, 31.6 (CH2), 73.3, 75.3 (OCH2), 122.6 (C-5),
125.1 (C-6), 129.0 (C-1), 140.3 (C-4), 150.9 (C-3), 155.8 (C-
1-{(E)-2-[2,3-Bis(dodecyloxy)phenyl]vinyl}-2,3-bis(do-
decyloxy)-4-methylbenzene (10b)
Yield 1.29 g (66%), viscous oil. – 1H NMR (CDCl3):
2), 189.5 (CHO). – MS (FD): m/z (%) = 320 (100) [M]+. – δ = 0.83 – 0.94 (m, 12 H, CH3), 1.15 – 1.44 (m, 64 H, CH2),
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M. Schwertel et al. · Preparation of 1,2,5,6,9,10-Hexaalkoxyhexahelicenes
1.44 – 1.58 (m, 8 H, CH2), 1.72 – 1.88 (m, 8 H, CH2), 2.25 (%) = 554 (44) [M]+, 186 (100). – C36H58O4 (554.8): calcd.
3
(s, 3 H, 4-CH3), 3.90 – 4.03 (m, 8 H, OCH2), 6.78 (d, J = C 77.93, H 10.54; found C 78.20, H 10.75.
7.9 Hz, 1 H, 40-H), 6.89 (d, 3J = 8.1 Hz, 1 H, 5-H), 6.99 (t,
3J = 7.9 Hz, 1 H, 50-H), 7.24 (d, 3J = 7.8 Hz, 1 H, 60-H),
Reduction of the esters 12a, b to the alcohols 13a, b
7.31 (d, 3J = 8.1 Hz, 1 H, 6-H), 7.41 (0s0, 2 H, olefin. H).
–
To LiAlH4 (190 mg, 5.0 mmol) in 50 mL of dry diethyl
13C NMR (CDCl3): δ = 14.1, 16.1 (CH3, partly superim-
ether, ester 12a, b (5.0 mmol) in 20 mL of diethyl ether
was slowly added at a rate, so that the mixture was gen-
tly boiling. After heating to reflux for 2 h, 10 mL of H2O
and 20 mL of 2 M HCl were added. The separated organic
layer was treated with aqueous NaHCO3, washed with H2O,
dried (MgSO4) and evaporated. The residue was purified by
column filtration (4×30 cm SiO2, CH2Cl2).
posed), 22.7, 26.2, 26.4, 29.4, 29.7, 30.4, 30.5, 31.9 (CH2,
partly superimposed), 68.6, 73.0, 73.7, 73.9 (OCH2), 112.1,
117.4, 120.2, 122.6, 123.7, 123.7, 125.7 (aromat. and olefin.
CH), 130.4, 131.7, 132.3 (aromat. Cq), 146.3, 150.2, 151.0,
152.6 (CqO). – MS (FD): m/z (%) = 931 (100) [M]+. –
C63H110O4 (931.6): calcd. C 81.23, H 11.90; found C 81.14,
H 11.81.
[3,4-Bis(hexyloxy)naphthalen-2-yl]methanol (13a)
Alkylation of 3,4-dihydroxynaphthalene-2-carboxylic acid
methyl ester (11)
Yield 1.69 g (94%), colorless solid, which melted
at 63 – 64 ◦C. – 1H NMR (CDCl3): δ = 0.85 – 0.97 (m, 6 H,
CH3), 1.28 – 1.44 (m, 8 H, CH2), 1.44 – 1.61 (m, 4 H, CH2),
1.73 – 1.93 (m, 4 H, CH2), 4.07 (t, 3J = 6.7 Hz, 2 H, OCH2),
4.13 (t, 3J = 6.6 Hz, 2 H, OCH2), 4.81 (s, 2 H, CH2OH),
7.33 – 7.48 (m, 2 H, aromat. H), 7.51 (s, 1 H, 1-H), 7.71 (d,
3J = 8.1 Hz, 1 H, aromat. H), 8.09 (d, 3J = 8.6 Hz, 1 H,
aromat. H). – 13C NMR (CDCl3): δ = 13.9 (CH3, super-
imposed), 22.5, 25.7, 25.8, 30.4, 31.6 (CH2, partly super-
imposed), 62.0 (CH2OH), 73.5, 73.6 (OCH2), 121.4, 122.0,
124.9, 125.5, 127.6 (aromat. CH), 129.2, 130.8, 134.7 (aro-
mat. Cq), 145.8, 146.4 (CqO). – MS (EI): m/z (%) = 358
(22) [M]+, 172 (100). – C23H34O3 (358.5): calcd. C 77.05,
H 9.56; found C 77.27, H 9.73.
To ester 11 [17, 18] (1.30 g, 5.96 mmol), K2CO3 (2.00 g,
14.5 mmol) and a trace of KI in 60 mL of dry acetone, 1-
bromoalkane 5a, b (14.0 mmol) was added. The vigorously
stirred mixture was heated to reflux under nitrogen for 3 d.
After filtration the solvent was evaporated and the residue pu-
rified by column chromatography (4×50 cm SiO2, toluene).
3,4-Bis(hexyloxy)naphthalene-2-carboxylic acid methyl
ester (12a)
Yield 2.03 g (88%), viscous oil. – 1H NMR (CDCl3):
δ = 0.83 – 0.92 (m, 6 H, CH3), 1.20 – 1.36 (m, 8 H, CH2),
1.36 – 1.52 (m, 4 H, CH2), 1.68 – 1.86 (m, 4 H, CH2), 3.94
(s, 3 H, OCH3), 4.06 – 4.18 (m, 4 H, OCH2), 7.35 – 7.55 (m,
2 H, 6-H, 7-H), 7.80 (d, 3J = 8.0 Hz, 1 H, aromat. H), 8.07 (s,
1 H, 1-H), 8.10 (d, 3J = 8.4 Hz, 1 H, aromat. H). – 13C NMR
(CDCl3): δ = 14.0 (CH3, superimposed), 22.6, 25.7, 25.8,
30.2, 30.4, 31.7 (CH2, partly superimposed), 52.2 (OCH2),
74.1, 74.7 (OCH2), 121.7, 125.6, 126.9, 127.7, 128.6 (aro-
mat. CH), 125.9 (C-4a), 130.0 (C-2), 131.4 (C-4a), 146.6,
147.6 (C-3, C-4), 166.8 (CO). – MS (EI): m/z (%) = 386
(21) [M]+, 186 (100). – C24H34O4 (386.5): calcd. C 74.58,
H 8.87; found C 74.27, H 8.57.
[3,4-Bis(dodecyloxy)naphthalen-2-yl]methanol (13b)
Yield 2.52 g (91%), colorless solid, which melted
at 54 – 56 ◦C. – 1H NMR (CDCl3): δ = 0.85 – 0.96 (m, 6 H,
CH3), 1.20 – 1.40 (m, 32 H, CH2), 1.40 – 1.60 (m, 4 H, CH2),
1.73 – 1.93 (m, 4 H, CH2), 4.04 – 4.19 (m, 4 H, OCH2), 4.82
(s, 2 H, CH2OH), 7.36 – 7.48 (m, 2 H, aromat. H), 7.52
(s, 1 H, 1-H), 7.75 (d, 3J = 8.1 Hz, 1 H, aromat. H), 8.07
(d, 3J = 8.5 Hz, 1 H, aromat. H). – 13C NMR (CDCl3):
δ = 14.1 (CH3, superimposed), 22.7, 26.1, 26.2, 29.4, 29.6,
30.5, 31.9 (CH2, partly superimposed), 62.7 (CH2OH), 73.7,
73.8 (OCH2), 121.5, 122.3, 125.1, 125.7, 127.7 (aromat.
CH), 129.4, 131.0, 134.7 (aromat. Cq), 146.0, 146.7 (CqO). –
MS (EI): m/z (%) = 526 (35) [M]+, 172 (100). – C35H58O3
(526.9): calcd. C 79.79, H 11.10; found C 80.10, H 10.75.
3,4-Bis(dodecyloxy)naphthalene-2-carboxylic acid methyl
ester (12b)
Yield 2.81 g (85%), viscous oil. – 1H NMR (CDCl3):
δ = 0.83 – 0.92 (m, 6 H, CH3), 1.20 – 1.42 (m, 32 H, CH2),
1.42 – 1.60 (m, 4 H, CH2), 1.75 – 1.92 (m, 4 H, CH2), 3.94
(s, 3 H, OCH3), 4.06 – 4.20 (m, 4 H, OCH2), 7.39 – 7.58 (m,
2 H, 6-H, 7-H), 7.79 (d, 3J = 8.1 Hz, 1 H, aromat. H), 8.07
Oxidation of the alcohols 13a, b to the aldehydes 14a, b
4.0 mmol of 13a, b and 2,3-dichloro-5,6-dicyano-1,4-
(s, 1 H, 1-H), 8.11 (d, J = 8.3 Hz, 1 H, aromat. H). – 13C
3
NMR (CDCl3): δ = 14.1 (CH3, superimposed), 22.7, 26.1,
26.2, 29.3, 29.6, 30.3, 30.5, 31.9 (CH2, partly superimposed), benzoquinone (DDQ, 908 mg, 4.0 mmol) were stirred under
52.2 (OCH3), 74.1, 74.7 (OCH2), 121.8, 125.6, 127.0, 127.7, Ar in 20 mL of 1,4-dioxane at room temperature for 12 h.
128.7 (aromat. CH), 125.9 (C-4a), 130.0 (C-2), 131.4 (C- The filtered reaction mixture was concentrated and purified
8a), 146.7, 147.7 (C-3, C-4), 166.8 (CO). – MS (EI): m/z by column chromatography (3×50 cm SiO2, CH2Cl2).
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3,4-Bis(hexyloxy)naphthalene-2-carbaldehyde (14a)
– MS (FD): m/z (%) = 431 (100) [M]+. – C29H37NO2
(431.6): calcd. C 80.70, H 8.64, N 3.25; found C 80.65,
H 8.80, N 3.24.
Yield 1.35 g (95%), colorless solid, which melted
at 43 – 45 ◦C. – 1H NMR (CDCl3): δ = 0.82 – 0.93 (m, 6 H,
CH3), 1.20 – 1.42 (m, 8 H, CH2), 1.42 – 1.62 (m, 4 H, CH2),
1.75 – 1.96 (m, 4 H, CH2), 4.14 (t, 3J = 6.6 Hz, 2 H, OCH2),
4.17 (t, 3J = 6.6 Hz, 2 H, OCH2), 7.41 – 7.62 (m, 2 H, 6-H,
7-H), 7.89 (d, 3J = 8.1 Hz, 1 H, 8-H), 8.11 (d, 3J = 8.5 Hz,
1 H, 5-H), 8.11 (s, 1 H, 1-H), 10.50 (s, 1 H, CHO). – 13C
NMR (CDCl3): δ = 13.9 (CH3, superimposed), 22.5, 25.6,
25.7, 30.0, 30.3, 31.5 (CH2, partly superimposed), 73.9, 74.9
(OCH2), 121.7, 125.0, 125.7, 128.4, 129.8 (aromat. CH),
129.2, 130.0, 132.8 (aromat. Cq), 145.8, 146.4 (CqO), 190.3
(CHO). – MS (FD): m/z (%) = 356 (100) [M]+. – C23H32O3
(356.5): calcd. C 77.48, H 9.05; found C 77.37, H 8.83.
{1-[3,4-Bis(dodecyloxy)naphthalen-2-yl]methylidene}-
phenylamine (15b)
Quantitative yield: 2.04 g, pale-yellow oil. – 1H NMR
(CDCl3): δ = 0.84 – 1.00 (m, 6 H, CH3), 1.20 – 1.44 (m,
32 H, CH2), 1.44 – 1.68 (m, 4 H, CH2), 1.68 – 1.96 (m,
4 H, CH2), 4.11 – 4.22 (m, 4 H, OCH2), 7.23 – 7.57 (m,
7 H, aromat. H), 7.90 (d, 3J = 8.2 Hz, 1 H, aromat. H),
8.12 (d, 3J = 8.3 Hz, 1 H, aromat. H), 8.45 (s, 1 H, 1-
H), 8.98 (s, 1 H, CHN). – 13C NMR (CDCl3): δ = 14.1
(CH3, superimposed), 22.7, 26.2, 29.4,29.5, 29.7, 30.3, 30.5,
31.9 (CH2, partly superimposed), 74.0, 76.4 (OCH2), 121.1,
121.7, 122.8, 125.5, 126.0, 127.1, 129.1 (aromat. CH, partly
superimposed), 129.6, 130.7, 131.3 (aromat. Cq), 146.5,
147.9 (CqO), 152.5 (CqN), 157.0 (CHN). – MS (EI): m/z
(%) = 599 (17) [M]+, 507 (100). – C41H61NO2 (599.9):
calcd. C 82.08, H 10.25, N 2.33; found C 82.05, H 10.27,
N 2.40.
3,4-Bis(dodecyloxy)naphthalene-2-carbaldehyde (14b)
Yield 1.81 g (86%), colorless solid, which melted at
about 30 ◦C. – 1H NMR (CDCl3): δ = 0.82 – 0.92 (m, 6 H,
CH3), 1.20 – 1.49 (m, 32 H, CH2), 1.49 – 1.65 (m, 4 H, CH2),
1.75 – 2.00 (m, 4 H, CH2), 4.10 (t, 3J = 6.6 Hz, 2 H, OCH2),
3
4.22 (t, J = 6.5 Hz, 2 H, OCH2), 7.40 – 7.60 (m, 2 H, aro-
mat. H), 7.89 (d, 3J = 8.1 Hz, 1 H, aromat. H), 8.11 (d,
3J = 8.6 Hz, 1 H, aromat. H), 8.13 (s, 1 H, 1-H), 10.51
(s, 1 H, CHO). – 13C NMR (CDCl3): δ = 14.1 (CH3, su-
perimposed), 22.6, 26.1, 26.2, 29.4, 29.5, 29.6, 30.2, 30.4,
31.9 (CH2, partly superimposed), 74.1, 75.1 (OCH2), 121.8,
125.2, 125.9, 128.5, 129.9 (aromat. CH), 129.3, 130.1, 133.0
(aromat. Cq), 146.9, 148.7 (CqO), 190.6 (CHO). MS (EI):
m/z (%) = 524 (13) [M]+, 188 (100). – C35H56O3 (524.8):
calcd. C 80.10, H 10.75; found C 80.21, H 10.80.
Siegrist reaction of the Schiff bases 15a, b and the
methylstilbenes 10a, b
Methylstilbene 10a, b (3.0 mmol) and Schiff base 15a, b
(3.3 mmol) were treated in 150 mL of dry DMF with 3.8 g
(34.0 mmol) KOC(CH3)3 at room temperature. After 0.5 h
the reaction mixture was heated to 90 ◦C and stirred for 1.5 h.
Then 30 mL of H2O and 50 mL of 2 M HCl were slowly
added. The mixture was extracted with 3 × 120 mL of di-
ethyl ether. The neutralized (NaHCO3) ether solution was
dried (MgSO4) and evaporated. The residue was purified by
column filtration (4×40 cm SiO2, toluene).
Formation of the Schiff bases 15a, b
Aldehyde 14a, b (3.40 mmol) and aniline (400 mg,
4.30 mmol) were dissolved in 60 mL of CHCl3 and heated
to reflux for 1 d, so that the formed H2O was continuously
removed. The volatile parts were distilled off and the residue
dried at 0.1 kPa. The obtained oily products were analytically
pure.
1,2-Bis(hexyloxy)-3-((E)-2-{2,3-bis(hexyloxy)-4-[(E)-2-(2,3-
bis(hexyloxy)phenyl)vinyl]phenyl}vinyl)naphthalene (16a)
Stilbene 10a (1.8 g, 3.0 mmol) and Schiff base 15a (1.4 g,
3.3 mmol) yielded 1.71 g (61%) 16a as yellow oil. – 1H
NMR (CDCl3): δ = 0.83 – 0.96 (m, 18 H, CH3), 1.20 – 1.40
(m, 24 H, CH2), 1.44 – 1.59 (m, 12 H, CH2), 1.75 – 1.90 (m,
12 H, CH2), 3.95 – 4.16 (m, 12 H, OCH2), 6.80 (d, 3J =
{1-[3,4-Bis(hexyloxy)naphthalen-2-yl]methylidene}-phenyl-
amine (15a)
Quantitative yield: 1.46 g, pale-yellow oil. – 1H NMR 8.1 Hz, 1 H), 7.00 (t, 3J = 8.0 Hz, 1 H), 7.26 (d, 3J = 8.0 Hz,
(CDCl3): δ = 0.82 – 0.98 (m, 6 H, CH3), 1.20 – 1.42 (m, 1 H, aromat. H), 7.34 – 7.48 (m, 5 H, aromat. and olefin.
8 H, CH2), 1.42 – 1.65 (m, 4 H, CH2), 1.65 – 1.96 (m, 4 H, H), 7.53 (d, 3J = 16.5 Hz, 1 H, olefin. H), 7.56/7.62 (AB,
CH2), 4.13–4.23 (m, 4 H, OCH2), 7.23 – 7.57 (m, 7 H, aro- 3J = 16.5 Hz, olefin. H), 7.77 (d, 3J = 8.3, 1 H, aromat. H),
mat. H), 7.90 (d, 3J = 8.2 Hz, 1 H, aromat. H), 8.11 (d, 7.87 (s, 1 H, aromat. H), 8.06 (d, 3J = 7.9, 1 H, aromat. H). –
3J = 8.3 Hz, 1 H, aromat. H), 8.44 (s, 1 H, 1-H), 8.97 (s, 1 H, 13C NMR (CDCl3): δ = 14.1 (CH3, superimposed), 22.8,
CHN). – 13C NMR (CDCl3): δ = 14.4 (CH3, superimposed), 25.9, 26.1,29.4, 29.7, 30.4, 31.6, 31.8, 32.8 (CH2, partly
23.0, 26.2, 30.6, 30.8, 32.0 (CH2, partly superimposed), 74.3, superimposed), 68.7, 73.8, 73.9, 74.0, 74.1, 74.2 (OCH2),
76.7 (OCH2), 121.4, 122.0, 123.1, 125.8, 126.3, 127.4, 129.5 112.4, 117.4, 119.9, 120.7, 120.7, 121.7, 123.4, 123.8 123.8,
(aromat. CH, partly superimposed), 129.6, 130.4, 131.1 (aro- 123.9, 124.4, 125.2, 125.5, 127.8 (aromat. and olefin. CH),
mat. Cq), 146.4, 147.8 (CqO), 152.3 (CqN), 157.3 (CHN). 129.2, 131.1, 131.6, 131.9, 132.2, 132.5 (aromat. Cq), 146.5,
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1354
M. Schwertel et al. · Preparation of 1,2,5,6,9,10-Hexaalkoxyhexahelicenes
146.6, 146.7, 150.6, 150.7, 152.7 (aromat. CqO). – MS (FD): 10 – 12 h. The N2 stream was maintained till the process
m/z (%) = 933 (100) [M]+. – C62H92O6 (933.4): calcd. came to an end. The reaction mixture was treated with aque-
C 79.78, H 9.93; found C 79.91, H 10.03.
ous NaHCO3, dried (MgSO4) and evaporated. The crude
product was purified by a twofold column chromatography
(3 × 50 cm SiO2, petroleum ether, b. p. 40 – 70 ◦C / CH2Cl2
5 : 1 to 2 : 1).
1,2-Bis(dodecyloxy)-3-((E)-2-{2,3-bis(dodecyloxy)-4-[(E)-
2-(2,3-bis(dodecyloxy)phenyl)vinyl]phenyl}vinyl)
naphthalene (16b)
1,2,5,6,9,10-Hexakis(hexyloxy)phenanthro[3,4-c]
phenanthrene (3a)
Stilbene 10b (2.8 g, 3.0 mmol) and Schiff base 15b (2.0 g,
3.3 mmol) yielded 3.36 g (78%) 16b as pale-yellow crys-
Yield 440 mg (68%), light-yellow oil. – 1H NMR
(CDCl3): δ = 14.0, 14.1 (CH3, superimposed), 22.7, 25.7,
26.0, 29.4, 29.5, 29.7, 30.5, 31.6, 31.8, 31.9 (CH2, partly
superimposed), 69.5, 73.8, 73.9, 74.0, 74.1, 74.1 (OCH2),
114.3, 120.1, 120.8, 120.9, 121.0, 121.6, 123.6, 124.1, 125.4,
128.0 (aromat. CH), 121.8, 125.4, 125.7, 126.1, 126.7, 127.3,
128.0, 128.1, 128.4, 129.3 (aromat. Cq), 142.4, 142.9, 143.5,
143.6, 144.1, 147.1 (CqO). – MS (FD): m/z (%) = 929 (100)
[M]+. – C62H88O6 (929.4): calcd. C 80.13, H 9.54; found
C 80.15, H 9.86.
1
tals, which melted at 49 – 51 ◦C. – H NMR (CDCl3): δ =
0.85 – 0.98 (m, 18 H, CH3), 1.20 – 1.50 (m, 96 H, CH2),
1.50 – 1.70 (m, 12 H, CH2), 1.83 – 1.96 (m, 12 H, CH2),
4.00 – 4.24 (m, 12 H, OCH2), 6.83 (d, 3J = 8.2 Hz, 1 H),
3
3
7.05 (t, J = 8.1 Hz, 1 H), 7.32 (d, J = 7.8 Hz, 1 H), 7.43
(t, 3J = 8.0 Hz, 1 H, aromat. H), 7.46 – 7.62 (m, 5 H, aro-
mat. and olefin. H), 7.59 (s, 1 H, aromat. H), 7.64/7.70 (AB,
3J = 16.6, 2 H, olefin. H), 7.82 (d, 3J = 7.5 Hz, 1 H, aro-
mat. H), 7.93 (s, 1 H, aromat. H), 8.14 (d, 3J = 7.9 Hz,
1 H, aromat. H). – 13C NMR (CDCl3): δ = 14.1 (superim-
posed), 22.7, 26.3, 26.4, 26.5, 29.4, 29.5, 29.7, 29.8, 30.5, 1,2,5,6,9,10-Hexakis(dodecyloxy)phenanthro[3,4-c]
30.6, 31.8, 32.0 (CH2, partly superimposed), 68.7, 73.7, phenanthrene (3b)
73.9, 74.0, 74.1, 74.2 (OCH2), 112.6, 117.7, 120.0, 120.8,
Yield 700 mg (70%), light-yellow oil. – 1H NMR
120.9, 121.7, 123.6, 123.7, 124.0, 124.1, 124.6, 125.2, 125.5,
(CDCl3): δ = 14.0, 14.1 (CH3, superimposed), 22.7, 26.1,
127.8 (aromat. and olefin. CH), 129.3, 131.2, 131.7, 132.0,
26.4, 29.4, 29.5, 29.7, 30.6, 32.0 (CH2, partly superim-
132.3, 132.6 (aromat. Cq), 146.7, 146.8, 147.8, 150.7, 150.8,
posed), 69.4, 73.7, 73.8, 74.0 (OCH2, partly superimposed),
152.8 (aromat. CqO). – MS (FD): m/z (%) = 1438 (100)
113.8, 120.1, 120.7, 120.8, 120.9, 121.5, 123.6, 124.0, 125.4,
[M]+. – C98H164O6 (1438.4): calcd. C 81.83, H 11.49; found
128.0 (aromat. CH), 121.7, 125.3, 125.6, 126.0, 126.6, 127.3,
C 81.88, H 11.45.
128.0, 128.1, 128.4, 129.2 (aromat. Cq), 142.2, 142.8, 143.5,
143.5, 144.1, 147.4 (CqO). – MS (FD): m/z (%) = 1434
Preparation of the phenanthro[3,4-c]phenanthrenes 3a, b
(100) [M]+. – C98H160O6 (1434.4): calcd. C 82.06, H 11.24;
found C 82.07, H 11.27.
A solution of 0.7 mmol 16a, b and 0.35 g (1.4 mmol) I2
in 2 L of dry benzene was purged by a stream of oxygen-
free nitrogen for 0.5 h. Methyloxirane (4.9 mL, 70 mmol)
was added and the mixture irradiated with a Hanovia-450 W
Acknowledgement
We are grateful to the Deutsche Forschungsgemeinschaft
medium-pressure lamp equipped with a Pyrex filter. The red and the Fonds der Chemischen Industrie for financial sup-
solution bleaches in the course of the reaction which takes port.
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