Novel dithienylethenes with extended π-systems: Synthesis by aldol condensation and photochromic properties

Article abstract of DOI:10.1002/ejoc.201000721

A facile and stereoselective route to symmetric π-extended dithienylethene derivatives is described. The key step of this route is an aldol condensation of 1,2-bis(5-formyl-2-methylthiophen-3-yl)cyclopentene with a large variety of acyl compounds. All synthesized photoswitches can be reversibly converted into the closed form by irradiation with visible light. The photochromic properties of nine new dithienylethenes are discussed. A new synthetic pathway leading to π-extended dithienylethenes is presented. Nine new photoswitches are obtained in a facile and very stereoselective procedure and their photochromic properties are discussed.

Full text of DOI:10.1002/ejoc.201000721

FULL PAPER
DOI: 10.1002/ejoc.201000721
Novel Dithienylethenes with Extended π-Systems: Synthesis by Aldol
Condensation and Photochromic Properties
Kai Altenhöner,[a] Jan-Hendrik Lamm,[a] and Jochen Mattay*[a]
Keywords: Photochromism / Photoswitches / Alkenes / Aldol reactions / Dithienylethene
A facile and stereoselective route to symmetric π-extended
dithienylethene derivatives is described. The key step of this
route is an aldol condensation of 1,2-bis(5-formyl-2-methyl-
thiophen-3-yl)cyclopentene with a large variety of acyl com-
pounds. All synthesized photoswitches can be reversibly con-
verted into the closed form by irradiation with visible light.
The photochromic properties of nine new dithienylethenes
are discussed.
heating to reflux was necessary for all other reactions. After
completion of the reaction water was added to precipitate
the chalcones 11–19. Mostly the compounds were obtained
in high purity. In some cases (13, 17, 18) further purifica-
tion had to be performed by column chromatography on
silica gel. All shown compounds 11–19 could be isolated
in good or moderate yield (see Table 1). The synthesized
Introduction
Dithienylethenes display extremely favourable photo-
chromic properties. Because of their high fatigue resistance
and thermal stability this class of photoswitches is the tar-
get of increased interest for applications in fields of optical
data storage and photoswitchable devices.[1–4] A large per-
centage of known dithienylethenes can only be switched by
UV light. In an earlier publication we showed how to
achieve a successive shift of the absorption bands of dif-
ferent dithienylethenes to the visible region of the electro-
magnetic spectrum by elongation of the conjugated π-sys-
tem by using Wittig-type reactions. In most cases these di-
thienylethenes were obtained as mixtures of up to three iso-
mers (E-E, E-Z, Z-Z).[5]
1
chalcones 11–19 were characterized by H and 13C NMR
and UV spectroscopy as well as by mass spectrometrical
methods.
Results and Discussion
Figure 1. Aldol condensation reaction of 1 with different acyl com-
pounds 2–10 leading to dithienylethenes 11–19.
Herein we report a facile and stereoselective synthetic
route to π-extended photochromic dithienylethenes. This
route only leads to one isomer and gives a new access to
dithienylethene chalcone derivatives with absorption bands
in the visible range of the electromagnetic spectrum.
Aldol condensation reactions have been well studied for
more than a century. This procedure can be used as a
powerful tool for a selective synthesis of new dithienyleth-
enes with extended conjugated π-systems. Starting from the
well known 1,2-bis(5-formyl-2-methylthiophen-3-yl)cyclo-
pentene 1[6] and a large variety of acyl compounds 2–10 we
performed several aldol condensation reactions in methanol
simply by adding an excess of KOH (Figure 1). The reac-
tion progress was monitored by TLC. In two cases (using 5
and 7) the reaction proceeded at room temperature whereas
Due to the reaction pathway of an aldol condensation all
the isolated compounds 11–19 were obtained as pure E-E
isomers (shown in Figure 1). No other isomers were ob-
served in the NMR spectra. All measured coupling con-
stants were between 15 and 16 Hz which is typical for trans
orientated double bond protons.[7] As shown in an earlier
publication the values for cis orientated double bond pro-
tons in comparable systems were in a range of 11–12 Hz.[5]
The E-E configuration is stable even after irradiation with
1
350 nm light for several minutes. H NMR spectra show a
mixture of the open and the closed isomers of the obtained
chalcones 11–19 in E-E configuration but no E-Z or Z-Z
isomer.
For a study of the photochromic behaviour and spectro-
scopic properties of the new dithienylethenes with altering
the moiety R (see Figure 1) different types of functional
groups were attached to the core unit 1 (aliphatic 11, aro-
View this journal online at
[a] Organische Chemie I, Universität Bielefeld,
Postfach 100131, 33501, Bielefeld, Germany
Fax: +49-(0)521-1066417
E-mail: oc1jm@uni-bielefeld.de
wileyonlinelibrary.com
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6033

K. Altenhöner, J.-H. Lamm, J. Mattay
FULL PAPER
Table 1. Applied acyl components 2–10, reaction times and yields.
derivative 11 differed from these values (354 nm). UV/Vis
spectra of selected chalcone derivatives are presented in
Figure 3.
Table 2. Absorption maxima of the synthesized chalcones 11–19 in
ethanol (open and closed form).
Chalcone
λmax (open) [nm]
λmax (closed) [nm]
(ε [103 Lcm–1mol–1])
(ε [103 Lcm–1mol–1])[a]
11
12
13
14
15
16
17
18
19
354 (29.2)
379 (10.2)
388 (36.9)
370 (33.3)
381 (38.1)
375 (34.3)
390 (34.1)
372 (19.4)
383 (12.5)
612 (17.5)
644 (7.0)
650 (9.5)
634 (13.8)
644 (24.1)
638 (20.0)
652 (19.1)
635 (4.8)
644 (5.5)
[a] At photostationary state.
[a] The reaction mixture was heated at reflux temperature. [b] The
reaction mixture was stirred at room temperature.
matic with different functional groups 12–16, phenylethen-
ylic 17 and heteroaromatic moieties 18–19) and UV/Vis
spectra were recorded.
All chalcones 11–19 can be reversibly switched between
their open and closed form and irrespective of the attached
functionality all compounds could be transferred to the
corresponding closed form by irradiation with 400 (or
less) nm light. The back reaction could be induced by irra-
diation with 590 nm light (see Figure 2). The colour of the
measured solutions changed form slightly yellow to green
or blue.
Figure 3. Comparison between UV/Vis absorption bands of chal-
cones 11, 12, 17 and 19 in ethanol.
Attachment of extended π-conjugated moieties R (Fig-
ure 1) to the chalcone core unit did not affect the absorp-
tion maximum significantly. The same trend could be ob-
served for the corresponding closed form isomers of the di-
thienylethenes 11c–19c. Absorption maxima of the here
presented chalcones were only slightly depending on the
length of the conjugated system of the attached moiety. Es-
pecially this becomes obvious by comparing chalcones 12
and 17. The extension of the conjugated system in R only
leads to a small change in the absorption maximum of
12 nm in the open form and 8 nm in the closed form. How-
ever, elongation of the conjugated π-system of the chalcone
core unit by two additional double bonds leads to a ba-
thochromic shift in the absorption maxima of 20 nm in the
Figure 2. Photochromic reaction of dithienylethene chalcone deriv-
atives 11–19 upon irradiation.
In comparison the absorption maxima of the open iso- open form and 37 nm in the closed form as shown in former
mers of dithienylethenes 12–19 deviate only in a small re- publications using comparable switches.[5] The most signifi-
gion of the electromagnetic spectrum. All compounds pos- cant change in the absorption properties is caused by the
sessing aromatic moieties 12–19 showed absorption maxima exchange of the aliphatic substituent (R = tert-butyl 11) by
between 370 and 390 nm (see Table 2). Solely the aliphatic a phenyl moiety (e.g., 12) which leads to a bathochromic
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Novel Dithienylethenes with Extended π-Systems
(4:1). After evaporation of the solvents 9 was obtained as a brown
oil; yield 1.190 g (8.58 mmol, 61%) (compound 9 was identified by
1H NMR spectroscopy, by comparison with data from the litera-
shift of 24/32 nm (open/closed form). Additional substitu-
ents on the benzene ring only slightly affect the absorption
properties.
1
ture[8]) H NMR (500 MHz, CDCl3, 25 °C): δ = 2.26 (s, 3 H), 2.37
As an example for the switching process Figure 4 shows
a complete open-close cycle of compound 11. After irradia-
tion at 400 nm the solution quickly turned blue. In the ab-
sorption spectrum the UV bands are diminished whereas
a new band arises in the visible region at 610 nm. During
successive irradiation an isosbestic point at 387 nm was ob-
served. The conversion back to the open form could be per-
formed with 590 nm light without any changes to the start-
ing spectrum.
(s, 3 H), 2.55 (s, 3 H), 6.20 (s, 1 H, 4-H) ppm.
2-Acetyl-5-methylthiophene (10): Acetyl chloride (0.81 mL,
11.36 mmol) was added to
a suspension of AlCl3 (1.680 g,
12.60 mmol) in CH2Cl2 (70 mL) at 0 °C followed by dropwise ad-
dition of 2-methylthiophene (1.00 mL, 10.33 mmol). After 1.5 h
stirring at 0 °C the reaction was quenched with water (30 mL). The
organic phase was separated and the aqueous layer was extracted
twice with CH2Cl2 (40 mL). The combined organic phases were
washed with satd. NaHCO3 solution (40 mL) and dried with
MgSO4. After evaporation of all volatile components in vacuo 10
was obtained as
a yellow crystalline solid; yield 1.420 g
(10.13 mmol, 98%) (compound 10 was identified by 1H NMR spec-
troscopy, by comparison with data from the literature[9]). 1H NMR
(500 MHz, CDCl3, 25 °C): δ = 2.48 (s, 3 H, SCCH3), 2.50 (s, 3 H,
3
3
COCH3), 6.77 (d, JH,H = 3.8 Hz, 1 H, 3-H) 7.48 (d, JH,H
=
3.8 Hz, 1 H, 4-H) ppm.
General Procedure for the Aldol Condensation Reactions Leading to
Chalcones 11–19: (see Figure 5) An excess of KOH and of the re-
spective acetyl compound 2–10 (applied amounts are listed below)
were dissolved in methanol (20–30 mL). Aldehyde 1 (200 mg,
0.63 mmol) was added to this solution and the mixture was stirred
at room temperature for 1 h. If after this time TLC controls showed
no new photochromic compound the reaction mixture was heated
to reflux. Reaction progress was monitored by TLC (reaction times
were given in Table 1 and below). After completion of the reaction
the mixture was cooled to room temperature and was diluted with
water. The resulting precipitate was collected by filtration and dried
in vacuo. In some cases the resulting solid needed to be purified by
column chromatography [silica gel, cyclohexane/ethyl acetate
(80:20)].
Figure 4. UV/Vis absorption spectrum of 11 in ethanol; a: before
irradiation, b: after 30 s at 400 nm and c–h: after continuous irradi-
ation time with 590 nm light after 6, 12, 18, 24, 30 and 36 min.
Conclusions
Several new dithienylethenes with an extended π-system
were synthesized by a facile and stereoselective aldol con-
densation. These compounds can be switched reversibly be-
tween the open and closed forms by using visible light.
Experimental Section
General: Aldehyde 1 was prepared according to a literature pro-
cedure.[6] Furan 9 and thiophene 10 were prepared as described
below. All other carbonyl compounds 2–8, solvents and reactants
were purchased from commercial sources and used without further
purification.
3-Acetyl-2,5-dimethylfuran (9): Acetyl
chloride (1.1 mL,
15.41 mmol) was added to suspension of AlCl3 (2.350 g,
a
17.62 mmol) in CH2Cl2 (70 mL) at 0 °C followed by dropwise ad-
dition of Dimethylfuran (1.50 mL, 14.12 mmol). After 2.5 h stirring
at 0 °C the reaction was quenched with water (50 mL). The organic
phase was separated and the aqueous solution was extracted twice
with CH2Cl2 (40 mL). The combined organic phases were washed
with satd. NaHCO3 solution (40 mL) and dried with MgSO4. All
volatile components were removed in vacuo. The brown oily residue
was filtered through silica gel eluting with cyclohexane/ethyl acetate
1
Figure 5. Proton labelling for H NMR signal assignment.
Chalcone 11: KOH (380 mg, 6.77 mmol); pinacolone (2) (0.20 mL,
1.68 mmol); reflux for 8 h; yield 230 mg (0.48 mmol, 73%); Rf =
0.70 (cyclohexane/ethyl acetate). 1H NMR (500 MHz, CDCl3,
25 °C): δ = 1.21 (s, 18 H, 7-H), 1.99 (s, 6 H, 3-H), 2.08 (m, 2 H, 1-
Eur. J. Org. Chem. 2010, 6033–6037
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6035

K. Altenhöner, J.-H. Lamm, J. Mattay
FULL PAPER
H), 2.79 (t, JH,H = 7.5 Hz, 4 H, 2-H), 6.73 (d, JH,H = 15.1 Hz, 2
3JH,H = 7.5 Hz, 4 H, 2-H), 3.85 (s, 6 H, 12-H), 6.93 (d, 4 H, 8-H,
3
3
3
3
H, 5-H), 6.96 (s, 2 H, 4-H), 7.65 (d, JH,H = 15.7 Hz, 2 H, 6-H) 10-H), 7.00 (s, 2 H, 4-H), 7.15 (d, JH,H = 15.1 Hz, 2 H, 5-H), 7.77
ppm. 13C NMR (125 MHz, CDCl3, 25 °C): δ = 14.9, 22.9, 26.1,
(d, JH,H = 15.4 Hz, 2 H, 6-H), 7.98 (d, 4 H, 7-H, 11-H) ppm. 13C
3
38.3, 43.0, 118.6, 133.2, 134.6, 135.5, 136.5, 136.9, 138.5, NMR (125 MHz, CDCl3, 25 °C): δ = 14.9, 22.9, 38.4, 55.5, 113.8,
204.0 ppm. MS (EI, 70 eV): m/z (%) = 480.19 (41) [M]+, 465.16
(28) [M – CH3]+, 423.12 (75) [M – tBu]+. HRMS: found for
C29H36O2S2 [m/z]: 480.21460, calcd. [m/z]: 480.21567, deviation:
1.07 mmu, 2.23 ppm.
119.6, 130.7, 131.2, 133.4, 134.7, 136.6, 136.7, 137.0, 139.1, 163.3,
188.1 ppm. EI, 70 eV): m/z (%) = 580.15 (17) [M]+, 565.13 (45)
[M
–
CH3]+, 135.02 (100) [C8H7O2]+. HRMS: found for
C35H32O4S2 [m/z]: 580.17300, calcd. [m/z]: 580.17420, deviation
[mmu]: 1.20, [ppm]: 2.07.
Chalcone 12: KOH (624 mg, 11.12 mmol); acetophenone (3)
(0.16 mL, 1.39 mmol); reflux for 6 h; yield 180 mg (0.35 mmol,
55%); Rf = 0.59 (cyclohexane/ethyl acetate); H NMR (500 MHz,
Chalcone 17: KOH (340 mg, 6.06 mmol); benzalacetone (8)
(240 mg, 1.64 mmol); stirring at room temperatur for 48 h; Col-
umn: silica gel [cyclohehane/ethyl acetate (80:20)]; yield 107 mg
(0.18 mmol, 30%); Rf = 0.35 (cyclohexane/ethyl acetate); 1H NMR
(600 MHz, CDCl3 25 °C): δ = 1.99 (s, 6 H, 3-H), 2.06 (m, 2 H, 1-
1
[D8]THF, 25 °C): δ = 2.04 (s, 6 H, 3-H), 2.13 (m, 2 H, 1-H), 2.88
3
3
(t, JH,H = 7.5 Hz, 4 H, 2-H), 7.29 (s, 2 H, 4-H), 7.34 (d, JH,H
=
15.2 Hz, 2 H, 5-H), 7.51 (m, 4 H, 8-H, 11-H), 7.58 (m, 2 H, 10-H),
3
3
3
3
7.85 (d, JH,H = 15.2 Hz, 2 H, 6-H), 8.05 [d, J(H,H) = 7.3 Hz, 4
H, 7-H, 12-H] ppm. 13C NMR (125 MHz, [D8]THF, 25 °C): δ =
15.0, 27.8, 39.2, 120.4, 129.1, 129.4, 133.3, 134.5, 135.7, 137.3,
137.9, 138.2, 139.4, 139.4, 188.6 ppm. EI, 70 eV): m/z (%) = 520.39
(61) [M]+, 505.35 (100) [M – CH3]+. HRMS: found for C33H28O2S2
[m/z]: 520.15307, calcd. [m/z]: 520.15160, deviation: 1.47 mmu,
2.83 ppm.
H), 2.78 (t, JH,H = 7.5 Hz, 4 H, 2-H), 6.69 (d, JH,H = 15.8 Hz, 2
3
H, 8-H), 6.97 (d, JH,H = 15.8 Hz, 2 H, 5-H), 6.99 (s, 2 H, 4-H),
3
7.37 (m, 6 H, 10-H, 11-H), 7.57 (m, 4 H, 9-H), 7.67 (d, JH,H
=
15.8 Hz, 2 H, 7-H), 7.70 (d, JH,H = 15.8 Hz, 2 H, 6-H) ppm. 13C
NMR (125 MHz, CDCl3, 25 °C): δ = 15.0, 22.9, 38.4, 123.2, 125.7,
128.4, 129.0, 130.4, 133.6, 134.7, 134.9, 136.0, 136.5, 137.1, 139.6,
142.9, 188.3 ppm. EI, 70 eV): m/z (%) = 572.17 (70) [M]+, 557.14
(100) [M – CH3]+. HRMS: found for C37H32O2S2: [m/z]: 572.18610,
calcd. 572.18437, deviation [mmu]: 1.73, [ppm]: 3.02.
3
Chalcone 13: KOH (380 mg, 6.77 mmol); p-iodoacetophenone (4)
(39 mg, 1.60 mmol); reflux for 6 h. Column: silica gel [cyclohehane/
ethyl acetate (80:20)]; yield 133 mg (0.17 mmol, 27%); Rf = 0.88
(cyclohexane/ethyl acetate); 1H NMR (500 MHz, CDCl3, 25 °C): δ
Chalcone 18: KOH (400 mg, 7.11 mmol); 3-acetyl-2,5-dimethyl-
furan (9) (360 mg, 2.60 mmol); reflux for 9 h; Column: silica gel
[cyclohehane/ethyl acetate (80:20)]; yield 86 mg (0.15 mmol, 24%);
Rf = 0.55 (cyclohexane/ethyl acetate); 1H NMR (500 MHz, CDCl3,
25 °C): δ = 1.95 (s, 6 H, 3-H), 2.24 (m; 8 H, 1-H, 8-H), 2.56 (s, 6
3
= 1.99 (s, 6 H, 3-H), 2.06 (m, 2 H, 1-H), 2.78 (t, JH,H = 7.5 Hz, 4
3
H, 2-H), 7.01 (s, 2 H, 4-H), 7.06 (d, JH,H = 15.1 Hz, 2 H, 5-H),
7.66 (d, 3JH,H = 8.2 Hz, 4 H, 8-H, 10-H), 7.77 (d, 3JH,H = 15.1 Hz,
2 H, 6-H), 7.81 (d, 3JH,H = 8.2 Hz, 4 H, 7-H, 11-H) ppm. 13C NMR
(125 MHz, CDCl3, 25 °C): δ = 15.3, 38.3, 100.4, 129.7, 129.8, 134.7,
136.3, 137.1, 137.5, 137.7, 137.8, 138.8, 137.9, 139.8, 188.8 ppm.
EI, 70 eV): m/z (%) = 771.90 (51) [M]+, 756.88 (71) [M –
CH3]+. HRMS: found for C33H26I2O2S2 [m/z]: 771.94740, calcd.
[m/z]: 771.94636, deviation: [mmu]: 1.04 [ppm]: 1.35.
H, 9-H), 2.76 (t, 3JH,H = 7.5 Hz, 4 H, 2-H), 6.25 (s, 2 H, 7-H), 6.76
3
(d, 3JH,H = 15.1 Hz, 2 H, 5-H), 6.92 (s, 2 H, 4-H), 7.62 (d, JH,H
=
15.1 Hz, 2 H, 6-H) ppm. 13C NMR (125 MHz, CDCl3, 25 °C): δ =
13.2, 14.4, 14.9, 22.9, 38.3, 105.6, 122.0, 122.5, 133.3, 134.7, 135.4,
136.5, 137.0, 138.9, 150.0, 157.6, 185.4 ppm. EI, 70 eV): m/z (%)
= 556.14 (50) [M]+, 541.11 (57) [M – CH3]+. HRMS: found for
C33H32O4S2 [m/z]: 556.17530, calcd. [m/z]: 556.17420, deviation
[mmu]: 1.10, [ppm]: 1.98.
Chalcone 14: KOH (380 mg, 6.77 mmol); o-methoxyacetophenone
(5) (0.22 mL, 1.60 mmol); reflux for 20 h; yield 234 mg (0.40 mmol,
1
63%); Rf = 0.52 (cyclohexane/ethyl acetate); H NMR (500 MHz,
Chalcone 19: KOH (380 mg, 6.77 mmol); 2-acetyl-5-methylthio-
phene (10) (270 mg, 1.93 mmol); reflux for 8 h; yield 212 mg
(0.38 mmol, 60%); Rf = 0.43 (cyclohexane/ethyl acetate); 1H NMR
(500 MHz, CDCl3, 25 °C): δ = 1.97 (s, 6 H, 3-H), 2.06 (m, 2 H, 1-
CDCl3 25 °C): δ = 1.96 (s, 6 H, 3-H), 2.04 (m, 2 H, 1-H), 2.76 (t,
3JH,H = 7.5 Hz, 4 H, 2-H), 3.87 (s, 6 H, 12-H), 6.94–7.01 (m, 8 H),
7.41–7.45 (m, 2 H), 7.56–7.59 (m; 4 H) ppm. 13C NMR (125 MHz,
CDCl3, 25 °C): δ = 14.9, 22.8, 38.3, 55.7, 111.6, 120.7, 124.9, 129.2,
130.2, 132.7, 133.2, 134.6, 135.9, 136.7, 136.9, 139.1, 158.0,
192.2 ppm. EI, 70 eV): m/z (%) = 580.13 (25) [M]+, 565.11 (41)
[M – CH3]+. HRMS: found for C35H32O4S2 [m/z]: 580.17450, calcd.
[m/z]: 580.17420, deviation: [mmu]: 0.30, [ppm]: 0.52.
3
H), 2.53 (s, 6 H, 9-H), 2.78 (t, JH,H = 7.5 Hz, 4 H, 2-H), 6.80 (d,
3
3JH,H = 3.2 Hz, 2 H, 8-H), 6.97 (d, JH,H = 15.1 Hz, 2 H, 5-H),
7.00 (s, 2 H, 4-H), 7.60 (d, 3JH,H = 3.8 Hz, 2 H, 7-H), 7.76 (d, 3JH,H
= 15.7 Hz, 2 H, 6-H) ppm. 13C NMR (125 MHz, CDCl3, 25 °C):
δ = 14.9, 16.1, 22.9, 38.3, 119.3, 126.9, 132.1, 133.5, 134.7, 135.9,
136.4, 137.0, 139.2, 143.5, 149.8, 181.2 ppm. EI, 70 eV): m/z (%)
= 560.08 (43) [M]+, 545.05 (72) [M – CH3]+, 125.00 (100)
[C6H5OS]+. HRMS: found for C31H28O2S4 [m/z]: 560.09710, calcd.
[m/z]: 560.09721, deviation [mmu]: 0.11, [ppm]: 0.20.
Chalcone 15: KOH (380 mg, 6.77 mmol); m-methoxyacetophenone
(6) (0.22 mL, 1.60 mmol); stirring at room temperature for 72 h;
yield 273 mg (0.47 mmol, 75%); Rf = 0.60 (cyclohexane/ethyl acet-
1
ate). H NMR (500 MHz, CDCl3, 25 °C): δ = 1.99 (s, 6 H, 3-H),
3
2.07 (m, 2 H, 1-H), 2.79 (t, JH,H = 7.5 Hz, 4 H, 2-H), 3.86 (s, 6
3
H, 12-H), 7.03 (s, 2 H, 4-H), 7.10 (d, 2 H, 10-H), 7.12 (d, JH,H
=
Acknowledgments
15.7 Hz, 2 H, 5-H), 7.38 (t, 2 H, 11-H), 7.49 (s, 2 H, 7-H), 7.54 (d,
3
2 H, 12-H), 7.78 (d, JH,H = 15.1 Hz, 2 H, 5-H) ppm. 13C NMR
This work was supported by the Biophotonics Initiative of the Ger-
man Ministry of Research and Education (BMBF) (grants
13N9234).
(125 MHz, CDCl3, 25 °C): δ = 15.0, 38.4, 55.5, 112.7, 119.2, 119.8,
120.9, 129.5, 133.8, 134.7, 136.6, 137.1, 137.4, 139.5, 139.7, 151.6,
160.0, 189.6 ppm. EI, 70 eV): m/z (%) = 580.13 (54) [M]+, 565.11
(100) [M – CH3]+. HRMS: found for C35H32O4S2 [m/z]: 580.17570,
calcd. [m/z]: 580.17420; deviation [mmu]: 1.50, [ppm]: 2.58.
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Chalcone 16: KOH (380 mg, 6.77 mmol); p-methoxyacetophenone
(7) (240 mg, 1.60 mmol); reflux for 7 h; yield 274 mg (0.47 mmol,
1
75%); Rf = 0.31 (cyclohexane/ethyl acetate); H NMR (500 MHz,
CDCl3, 25 °C): δ = 1.98 (s, 6 H, 3-H), 2.07 (m, 2 H, 1-H), 2.78 (t,
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Eur. J. Org. Chem. 2010, 6033–6037

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Received: May 19, 2010
Published Online: August 25, 2010
Eur. J. Org. Chem. 2010, 6033–6037
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