Functionalized fulgides and fluorophore-photoswitch conjugates

Article abstract of DOI:10.1002/ejoc.201100228

Various fulgides based on benzofuryl and indolyl core units with versatile functionalities were synthesized. Substitution at the phenylic site shows only small effects on the photochromic properties compared to the parent compounds 30 and 31. Fulgide-dye

Full text of DOI:10.1002/ejoc.201100228

FULL PAPER
DOI: 10.1002/ejoc.201100228
Functionalized Fulgides and Fluorophore-Photoswitch Conjugates
Frank Strübe,[a] Susann Rath,[a] and Jochen Mattay*[a]
Keywords: Fulgides / Photochemistry / Photochromism / Click chemistry / Fluorescence
Various fulgides based on benzofuryl and indolyl core units
with versatile functionalities were synthesized. Substitution
at the phenylic site shows only small effects on the photo-
chromic properties compared to the parent compounds 30
and 31. Fulgide–dye conjugates were prepared based on an-
thryl and coumaryl moieties. Fluorophores were introduced
to the fulgide via substitution reaction or copper-catalyzed
azide-alkyne cycloaddition (CuAAC). The synthesized con-
jugates show weak fluorescence and quenching properties
in solution.
Introduction
Results and Discussion
Organic photochromic materials have attracted a lot of
attention during the last decades,[1] e.g. for data storage,[2]
molecular energy transfer reactions,[3] and high resolution
fluorescence microscopy.[4] Due to their inherent switching
characteristics (Scheme 1), fulgides have a high potential for
manifold applications.[5] These applications require efficient
photoswitching and high thermal[6] and photochemical[7]
stability of the photochromic compounds. Herein we pres-
ent the synthesis of fulgides with versatile molecular con-
necting options based on benzofuryl and indolyl core struc-
tures. Different functionalities were introduced by substitu-
tion at the phenylic site, e.g. carboxylic acid, alkene or alk-
yne moieties. These groups offer a wide range of binding
options to any target molecule, e.g. to polymers[8,9] and
dyes. For fluorescence switching purposes, we synthesized
and investigated fulgides linked to fluorophores such as
anthracene and coumarin via substitution or copper-cata-
lyzed azide–alkyne cycloaddition (CuAAC). Modulation of
the fluorophores’ emission intensities should be possible by
switching the fulgide moieties between their open and
closed forms.
Synthesis
The benzofuryl and indolyl core units were synthesized
in Nenitzescu type reactions (Scheme 2).[10] Using glacial
acetic acid as the solvent gave 2 only, whereas a mixture of
3 and 2 was obtained using nitromethane as the solvent.
The indolyl compound 3 was purified by recrystallization
from methanol.
Scheme 2. Nenitzescu-type reaction to form benzofuryl 2 and
indolyl 3 precursors.
For further functionalization, 2 and 3 were dissolved in
dimethylformamide, and the hydroxyl group was deproton-
ated with sodium hydride, followed by substitution with ha-
lides 4–11 to give compounds 12–27 (Table 1). In general,
the substitution products 12–27 were obtained in yields of
65–82%. In the reaction with 1,3-dibromopropane (6), the
monosubstitution products 16 and 17 were formed in small
amounts. Instead, dehydrobromination was the main reac-
tion, leading to 20 and 21. Hence these bromo compounds
were left out from further investigation. Bromination of 12
and 13 gave compounds 28 and 29, respectively (Scheme 3).
A second bromination at the acetylic moiety of benzofuryl
compound 12 was also observed, which could be sup-
pressed by higher dilution and slow addition of bromine.
The benzofuryl and indolyl precursors were used in
Stobbe condensations[11] to obtain the fulgides listed in
Table 2. Condensation with diethyl isopropylidenesuccin-
ate[12] was performed in THF at –78 °C using lithium diiso-
propylamide (LDA) as the base. Intermediate products
Scheme 1. Photochromism of functionalized heterocyclic fulgides
(Y = O or NMe, R = see Table 1).
[a] Organische Chemie I, Universität Bielefeld,
Postfach 100131, 33501 Bielefeld, Germany
Fax: +49-521-1066417
E-mail: mattay@uni-bielefeld.de
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201100228.
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F. Strübe, S. Rath, J. Mattay
FULL PAPER
Table 1. List of substituted ketones.
Table 2. Stobbe condensation[11] of ketones 12–29 and diethyl iso-
propylidenesuccinate[12] and subsequent saponification and dehy-
dration to form fulgides 30–45. Ketones 16 and 17 were left out
from the investigation.
Scheme 3. Bromination of 12 and 13.
were only detected by TLC and were subsequently treated
with potassium hydroxide for saponification and dicyclo-
hexylcarbodiimide for anhydride formation. Fulgides were
purified by column chromatography with mixtures of cyclo-
hexane and ethyl acetate and recrystallization from suitable
solvents. The photochromic compounds were obtained in
yields of 5–15%.[13]
Saponification of the ester functionality of 14 and 15 oc-
curred as a side reaction, leading to carboxylic acids 32 and
33. During the saponification step, the bromo compounds
18 and 19 underwent substitution reactions with ethoxide,
yielding the corresponding ether derivatives 34 and 35.
Furthermore, the synthesis of the alkyne fulgide 38 was not
successful. Formation of a photochromic compound was
The new fulgides offer versatile connecting options to
observed by TLC, but it could not be isolated and charac- biomolecules, polymers and fluorophores. For example, by
terized.
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Functionalized Fulgides and Fluorophore-Photoswitch Conjugates
Scheme 4. Copper-catalyzed azide–alkyne cycloaddition.
be linked to amines. Cross coupling reactions[14] make way spectroscopy. Complete absorption and emission spectra of
for further functionalization of the bromo compounds 40/ 42/43 and 48/49 are available in the Supporting Infor-
41 and 44/45. To demonstrate, we subjected the alkyne fulg- mation. All fulgides showed reversible photoswitching be-
ide 39 to “click” reactions with azide dyes.[15] Anthracene havior (e.g. 39, see Figure 1). As expected, substitution at
and coumarin azides were used as fluorophores, and were the 5-position of the heterocyclic moiety showed only small
prepared according to the literature.[16] 9-(Azidomethyl)- effects on the absorption of the fulgides (Table 3).
anthracene (46) was prepared from 9-(hydroxymethyl)-
anthracene by bromination and subsequent treatment with
sodium azide.[17] 4-Azidomethyl-7-methoxycoumarin (47)
was synthesized in a Pechmann reaction starting from 3-
methoxyphenol and 4-chloroacetoacetate and further treat-
ment with sodium azide.[18] The triazole formation between
the azides and alkyne 39 was catalyzed by [Cu(PPh3)3Br][19]
in chloroform solution at room temperature (Scheme 4).
The cycloaddition products were obtained in moderate
yields of 48% and 60%.
Photochemistry
In this study, only the (E)-forms of the fulgides were iso-
lated and investigated. The photochemical properties of the
synthesized fulgides were analyzed by UV/Vis spectroscopic
methods in dichloromethane solutions. In addition, fluoro-
Figure 1. Absorption spectrum of 39. Solid line: 10–4 m solution in
dichloromethane; dashed line: after 5 min irradiation with λEǞC
=
phore–fulgide conjugates were investigated by emission 405 nm light.
Table 3. UV/Vis data of the synthesized fulgides.
Compound
λmax [nm] (ε [Lmol–1 cm–1]) of E
λmax [nm][a] of C
30
31
32
33
34
35
36
37
39
40
41
42
43
44
45
48
49
339 (7200)
396 (10500)
337 (5900)
397 (5500)
332 (8000)
399 (9300)
338 (7200)
397 (8600)
506
645
508
643
504
646
507
642
635
505
639
506
604
511
628
639
638
396 (8600)
339 (7400)
396 (9300)
387 (8600), 367 (12000), 348 (11400), 334 (9300)[b]
393 (9300),[b] 387 (13700), 368 (13000), 350 (8300), 330 (6100)
335 (5300)
394 (9700)
389 (13100), 369 (13600), 350 (8800), 334 (6100)[b]
395 (8700)
[a] After 5 min irradiation with λEǞC = 365 or 405 nm light, respectively. [b] Superimposed by the anthracene absorption bands.
Eur. J. Org. Chem. 2011, 4645–4653
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F. Strübe, S. Rath, J. Mattay
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Typically the benzofuryl compounds showed absorption modulation of the fluorescence was achieved. Excitation
maxima at 332–339 nm for the open (E)-form, and at 504– with λex = 335 nm light resulted in fluorescence between
511 nm for the closed (C)-form in the photostationary state 350 and 550 nm. By closing the photochromic unit with
upon irradiation with λEǞC = 365 nm light. For the indolyl λEǞC = 405 nm light, the emission decreased to 84%. The
fulgides, the absorption maxima were bathochromically emission between 350 and 420 nm could be recovered to the
shifted to 393–399 nm for the (E)-form and to 604–646 nm initial value upon reopening with λCǞE = 620 nm light,
for the closed (C)-form in the photostationary state upon while the emission between 420 and 550 nm was still re-
irradiation with λEǞC = 405 nm light. The decoloration duced.
could be initiated by irradiation with 530 nm light and 590
In a previous study, we investigated fluorescence modula-
or 620 nm light. For the anthracene-containing conjugates, tion based on dithienylethene photoswitches.[16] These con-
the absorption maxima of the open forms were superim- jugates also contained coumaryl and anthryl units as flu-
posed by the typical absorption bands of the anthracene orophores. The modulation of the emission was very effec-
moieties.
tive, and it could be reduced to 35–10% by switching the
Modulation of the fluorophores was expected for the flu- dithienylethene into the closed form. Reopening of the pho-
orophore–fulgide conjugates by switching the photochro- toswitch almost recovered the initial value of the emission.
mic unit between the open and closed form upon irradia- We proposed a resonance energy transfer (RET) or a pho-
tion. The anthryl–benzofuryl compound 42 showed the typ- toinduced energy transfer mechanisms to be responsible for
ical anthracene emission pattern between 380–480 nm upon the quenching processes.
excitation with λex = 360 nm light (Figure 2). Irradiation
A resonance energy transfer (RET) can be assumed if
with λEǞC = 365 nm light decreased the emission to 66%. sufficient spectral overlap between the emission spectra of
Reopening of the fulgide with λCǞE = 530 nm light almost the fluorophores and the absorption maxima of the photo-
recovered the emission to the starting value. After two switches can be found.[20] For modulation of the emission,
switching cycles, the fluorescence increased well beyond the a change in the overlap integral must be achieved, for exam-
starting value, which indicated decomposition processes.
ple, by changing the absorption maxima upon closing and
reopening the photochromic unit. One drawback of the syn-
thesized fulgides is the undesired photoisomerization be-
tween the open (E)- and (Z)-forms upon irradiation, which
could be proved for compound 30.[21] This competitive reac-
tion to the EǞC ring closing reaction could be a reason
for the weak modulation of the emission. Additionally, the
absorption spectra of the (C)-forms still exhibit an intense
absorption in the region of the absorption maxima of the
(E)-forms. Due to low quantum yields for the coloration
reaction of indolyl fulgides, the concentration of the (C)-
form in the photostationary state appears to be small com-
pared to the (E)- and (Z)-forms.[22] Therefore, there are no
remarkable changes in the UV/Vis spectra for the absorp-
tion maxima near 400 nm. Due to this, the overlap integrals
of the synthesized conjugates exhibit only small differences
in the open and closed forms. We assume these absorption
characteristics of the photoswitches to be responsible for
their low modulation properties.
Figure 2. Emission spectrum of 42 (λex = 360 nm). Solid line:
3ϫ10–6 m in dichloromethane; dashed line: after 20 s irradiation
with λEǞC = 365 nm light; dotted line: after 30 s irradiation with
λCǞE = 530 nm light.
In further studies the exact mechanisms of the quenching
Conjugate 43 showed an inverse emission characteristic processes should be elucidated. Preliminary NMR experi-
compared to 42. Upon excitation with λex = 360 nm light, ments indicate that steric factors may play a role for the
only very weak fluorescence could be observed between modulation properties.
380–480 nm. Irradiation with λEǞC = 405 nm light led to
an increased emission with a maximum at 415 nm. How-
ever, the emission could not be reduced by irradiation with
Conclusions
λCǞE = 620 nm light.
We succeeded in synthesizing a variety of novel function-
Remarkably, the triazole conjugate 48 showed almost no alized benzofuryl and indolyl fulgides. All show photochro-
fluorescence upon excitation with λex = 360 nm light, but mic behavior upon alternating irradiation with UV and vis-
with excitation at λex = 263 nm light, a similar behavior was ible light. We attached fluorophores to an alkyne fulgide via
observed as for 42. Closing 48 by irradiation at λEǞC
=
a “click” reaction. The new fluorophore–fulgide conjugates
405 nm led to a reduced emission at 417 nm to 81%, which exhibit relatively small effects on the switching behavior
could be recovered to the initial value by irradiation with of emission. Only for anthryl–benzofuryl fulgide 42 and
λCǞE = 620 nm light. Longer irradiation led to decomposi- anthryl–indolyl fulgide 48 a substantial modulation of the
tion of the conjugate. For the coumaryl compound 49, little emission was achieved.
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Functionalized Fulgides and Fluorophore-Photoswitch Conjugates
(s, 3 H, CH3), 2.47 (s, 3 H, CH3) ppm. 13C NMR (126 MHz, [D6]-
DMSO): δ = 192.6, 153.0, 144.8, 130.7, 127.0, 112.9, 111.1, 110.5,
105.4, 31.2, 29.6, 12.6 ppm. MS (EI, 70 eV): m/z (%) = 203 (36)
[M+], 189 (13), 188 (100). HRMS (EI): calcd. for C12H13NO2 [M+]
203.09463; found 203.09600.
Experimental Section
General: Commercially available compounds were purchased from
Acros, Alfa Aesar, Sigma Aldrich or VWR, and were used as re-
ceived. Solvents were of analytical grade and dried according to
standard procedures. Column chromatography was performed with
silica gel (0.040–0.063 mm, Macherey–Nagel). NMR spectra were
measured with Bruker DRX 500 and Avance 500 spectrometers,
and measured at room temperature. Substances were dissolved in
CDCl3 (δ =7.24 ppm/77.0 ppm) or [D6]DMSO (δ =2.49 ppm/
39.5 ppm) and referenced to solvent peaks. EI mass spectra were
recorded using an Autospec X magnetic sector mass spectrometer
with EBE geometry equipped with a standard EI source. ESI mass
spectra were recorded using a Bruker Esquire 3000 ion trap mass
spectrometer equipped with a standard ESI/APCI source. HRMS
spectra were performed using a Bruker APEX III Fourier Trans-
form Ion Cyclotron Resonance (FT-ICR) mass spectrometer. Ab-
sorption spectra were recorded with a Perkin–Elmer Lambda 40
spectrometer, and fluorescence spectra were recorded with a Per-
kin–Elmer LS50B spectrometer. For irradiation experiments, LEDs
(365, 405, 530, 590 and 620 nm light) were used. The synthesis of
the azide precursors 46 and 47 was published before.[16]
General Functionalization of 2 and 3: To a stirred solution of 2 or
3 (6 mmol) in dimethyl formamide (DMF, 40 mL), sodium hydride
(0.30 g, 7 mmol, 60% susp.) was added at 0 °C under argon. After
stirring for 1 h, the appropriate halide 4–11 (7 mmol) was added,
and the reaction mixture was stirred for an additional 2 h at room
temperature. The reaction was quenched by addition of aqueous
HCl (50 mL, 2 m) and water (50 mL). The aqueous layer was ex-
tracted with ethyl acetate (3ϫ75 mL). The combined organic layers
were washed with brine and dried with MgSO4, and the solvent
was removed in vacuo. The products were purified by column
chromatography on silica gel with mixtures of cyclohexane and
ethyl acetate. In some cases, addition of aqueous HCl during the
workup procedure led to a precipitate, which could be filtered off
and recrystallized to give the desired product.
1-(5-Methoxy-2-methylbenzofuran-3-yl)ethanone (12): Yield: 1.00 g,
1
4
4.92 mmol, 82%. H NMR (500 MHz, CDCl3): δ = 7.44 (d, JH,H
= 2.6 Hz, 1 H, ArH), 7.29 (d, 3JH,H = 8.9 Hz, 1 H, ArH), 6.85 (dd,
(Z)-4-Methylaminopent-3-en-2-one (1): Methylamine (10 mL,
0.12 mol, 40% aq. sol.) was added to acetyl acetone (10.30 mL,
0.10 mol), and the mixture was stirred for 2 h at room temperature.
After the exothermic reaction ended, the layers were separated, and
the aqueous layer was extracted with diethyl ether (2ϫ30 mL). The
combined organic layers were washed with water and brine and
dried with MgSO4. All volatile compounds were removed in vacuo,
and the product was recrystallized from diethyl ether. Compound
1 was obtained as colorless needles, which sublimed under high
vacuum. Yield: 10.52 g, 90 mmol, 90%. 1H NMR (500 MHz,
CDCl3): δ = 10.67 (br. s, 1 H, NH), 4.95 (s, 1 H, CH), 2.89 (d,
3JH,H = 5.1 Hz, 3 H, NCH3), 1.96 (s, 3 H, CH3), 1.88 (s, 3 H, CH3)
ppm. 13C NMR (126 MHz, CDCl3): δ = 194.6, 164.0, 95.0, 29.3,
28.6, 18.5 ppm. MS (EI, 70 eV): m/z (%) = 113 (50) [M+], 98 (100)
[M – CH3+], 56 (65), 43 (16), 40 (14).
3JH,H = 8.9, JH,H = 2.6 Hz, 1 H, ArH), 3.84 (s, 3 H, CH3), 2.72
4
(s, 3 H, CH3), 2.57 (s, 3 H, CH3) ppm. 13C NMR (126 MHz,
CDCl3): δ = 194.0, 163.3, 156.8, 148.4, 126.8, 117.9, 112.7, 111.2,
104.5, 55.9, 30.9, 15.6 ppm. MS (EI, 70 eV): m/z (%) = 204 (60)
[M+], 190 (12), 189 (100). HRMS (EI): calcd. for C12H12O3 [M+]
204.07864; found 204.07900.
1-(5-Methoxy-1,2-dimethyl-1H-indol-3-yl)ethanone (13): Yield:
1.03 g, 4.74 mmol, 79%. 1H NMR (500 MHz, CDCl3): δ = 7.49 (d,
3
4JH,H = 2.4 Hz, 1 H, ArH), 7.14 (d, JH,H = 8.8 Hz, 1 H, ArH),
3
4
6.85 (dd, JH,H = 8.8, JH,H = 2.4 Hz, 1 H, ArH), 3.86 (s, 3 H,
CH3), 3.58 (s, 3 H, CH3), 2.66 (s, 3 H, CH3), 2.58 (s, 3 H, CH3)
ppm. 13C NMR (126 MHz, CDCl3): δ = 194.0, 155.7, 144.9, 131.6,
127.0, 114.0, 111.0, 109.9, 103.8, 55.8, 31.4, 29.5, 12.8 ppm. MS
(EI, 70 eV): m/z (%) = 217 (47) [M+], 203 (13), 202 (100). HRMS
(EI): calcd. for C13H15NO2 [M+] 217.11028; found 217.10900.
1-(5-Hydroxy-2-methylbenzofuran-3-yl)-ethanone (2): To a solution
of p-benzoquinone (2.13 g, 20 mmol) in glacial acetic acid (80 mL),
compound 1 (2.33 g, 21 mmol) dissolved in glacial acetic acid
(30 mL) was added. In an exothermic reaction, a colorless precipi-
tate was formed after a few minutes. After stirring for 2 h, the pre-
cipitate was filtered off, washed with water and dried in vacuo.
The product 2 was used without further purification, but could be
recrystallized from glacial acetic acid. Yield: 2.19 g, 12 mmol, 58%.
1H NMR (500 MHz, [D6]DMSO): δ = 9.31 (s, 1 H, OH), 7.35 (m,
Ethyl
4-(3-Acetyl-2-methylbenzofuran-5-yloxy)butanoate
(14):
1
Yield: 1.22 g, 4.02 mmol, 67%. H NMR (500 MHz, CDCl3): δ =
7.43 (d, JH,H = 2.5 Hz, 1 H, ArH), 7.29 (d, JH,H = 8.9 Hz, 1 H,
4
3
3
4
ArH), 6.89 (dd, JH,H = 8.9, JH,H = 2.6 Hz, 1 H, ArH), 4.13 (q,
3JH,H = 7.1 Hz, 2 H, CH2), 4.04 (t, 3JH,H = 6.1 Hz, 2 H, CH2), 2.73
3
(s, 3 H, CH3), 2.58 (s, 3 H, CH3), 2.52 (t, JH,H = 7.3 Hz, 2 H,
CH2), 2.11 (m, 2 H, CH2), 1.24 (t, 3JH,H = 7.2 Hz, 3 H, CH3) ppm.
13C NMR (126 MHz, CDCl3): δ = 194.1, 173.2, 163.3, 156.0, 148.4,
126.8, 117.9, 113.1, 111.2, 105.5, 67.6, 60.4, 31.0, 30.8, 24.7, 15.6,
14.2 ppm. MS (EI, 70 eV): m/z (%) = 304 (11) [M+], 217 (14), 175
(39), 115 (94), 87 (100). HRMS (EI): calcd. for C17H20O5 [M+]
304.13107; found 304.13050.
3
4
2 H, ArH), 6.73 (dd, JH,H = 8.8, JH,H = 2.5 Hz, 1 H, ArH), 2.72
(s, 3 H, CH3), 2.53 (s, 3 H, CH3) ppm. 13C NMR (126 MHz, [D6]-
DMSO): δ = 193.8, 163.2, 154.3, 146.9, 126.7, 117.1, 112.9, 111.1,
106.4, 30.8, 15.4 ppm. MS (EI, 70 eV): m/z (%) = 190 (51) [M+],
176 (11), 175 (100), 147 (13), 43 (20).
Ethyl 4-(3-Acetyl-1,2-dimethyl-1H-indol-5-yloxy)butanoate (15):
Yield:1.24 g, 3.9 mmol, 65%. 1H NMR (500 MHz, CDCl3): δ =
1-(5-Hydroxy-1,2-dimethyl-1H-indol-3-yl)ethanone (3): To a solu-
tion of p-benzoquinone (19.11 g, 0.18 mol) in nitromethane
(89 mL), compound 1 (20.00 g, 0.18 mol) dissolved in nitromethane
(177 mL) was added. A colorless precipitate was formed after stir-
ring for 20 h. The precipitate was filtered off, washed with nitro-
methane and a small amount of diethyl ether and dried in vacuo.
The residue contained a mixture of the indolyl and benzofuryl
compounds, and the product 3 was isolated by recrystallization
4
3
7.51 (d, JH,H = 2.3 Hz, 1 H, ArH), 7.16 (d, JH,H = 8.8 Hz, 1 H,
3
4
ArH), 6.87 (dd, JH,H = 8.8, JH,H = 2.3 Hz, 1 H, ArH), 4.17 (q,
3JH,H = 7.1 Hz, 2 H, CH2), 4.09 (t, 3JH,H = 6.2 Hz, 2 H, CH2), 3.60
(s, 3 H, CH3), 2.68 (s, 3 H, CH3), 2.61 (s, 3 H, CH3), 2.58 (t, 3JH,H
3
= 7.4 Hz, 2 H, CH2), 2.17 (m, 2 H, CH2), 1.29 (t, JH,H = 7.1 Hz,
3 H, CH3) ppm. 13C NMR (126 MHz, CDCl3): δ = 194.0, 173.3,
155.0, 145.1, 131.8, 127.1, 114.0, 111.5, 110.0, 104.9, 67.5, 60.9,
from methanol. Yield: 18.77 g, 94 mmol, 53%. 1H NMR 31.5, 30.9, 29.6, 24.9, 14.3, 12.8 ppm. MS (EI, 70 eV): m/z (%) =
4
(500 MHz, [D6]DMSO): δ = 8.97 (s, 1 H, COOH), 7.38 (d, JH,H
317 (30) [M+], 230 (22), 202 (10), 188 (43), 174 (12), 115 (100), 87
(88). HRMS (EI): calcd. for C18H23NO4 [M+] 317.16271; found
317.16190.
= 1.8 Hz, 1 H, ArH), 7.28 (d, 3JH,H = 8.7 Hz, 1 H, ArH), 6.67 (dd,
4
3JH,H = 8.7, JH,H = 2.0 Hz, 1 H, ArH), 3.63 (s, 3 H, CH3), 2.64
Eur. J. Org. Chem. 2011, 4645–4653
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F. Strübe, S. Rath, J. Mattay
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4
3
1-[5-(5-Bromopentyloxy)-2-methylbenzofuran-3-yl]ethanone
(18): 7.59 (d, JH,H = 2.2 Hz, 1 H, ArH), 7.16 (d, JH,H = 8.8 Hz, 1 H,
Yield:1.64 g, 4.86 mmol, 81%. 1H NMR (500 MHz, CDCl3): δ =
ArH), 6.91 (dd, JH,H = 8.8, JH,H = 2.2 Hz, 1 H, ArH), 4.73 (d,
3
4
7.43 (d, JH,H = 2.5 Hz, 1 H, ArH), 7.29 (d, JH,H = 8.9 Hz, 1 H, 4JH,H = 2.1 Hz, 2 H, CH2), 3.59 (s, 3 H, CH3), 2.66 (s, 3 H, CH3),
4
3
3
4
4
ArH), 6.85 (dd, JH,H = 8.9, JH,H = 2.6 Hz, 1 H, ArH), 4.00 (t, 2.58 (s, 3 H, CH3), 2.51 (t, JH,H = 1.9 Hz, 1 H, CH) ppm.
3JH,H = 6.3 Hz, 2 H, CH2), 3.42 (t, 3JH,H = 6.8 Hz, 2 H, CH2), 2.72 13C NMR (126 MHz, CDCl3): δ = 194.0, 153.6, 145.3, 132.2, 126.9,
(s, 3 H, CH3), 2.58 (s, 3 H, CH3), 1.93 (m, 2 H, CH2), 1.82 (m, 2 114.0, 111.7, 109.9, 105.7, 78.9, 75.3, 56.7, 31.4, 29.5, 12.7 ppm.
H, CH2), 1.62 (m, 2 H, CH2) ppm. 13C NMR (126 MHz, CDCl3): MS (EI, 70 eV): m/z (%) = 241 (50) [M+], 226 (13), 203 (14), 202
δ = 194.0, 163.3, 156.1, 148.4, 126.8, 117.8, 113.1, 111.2, 105.4,
68.4, 33.6, 32.5, 31.0, 28.5, 24.8, 15.6 ppm. MS (EI, 70 eV): m/z
(%) = 340 (32) [M(81Br)+], 338 (32) [M(79Br)+], 190 (66), 176 (11),
175 (100), 69 (34). HRMS (EI): calcd. for C16H19O3Br [M+]
338.05176; found 338.04950.
(100), 198 (12), 174 (38), 131 (14). HRMS (EI): calcd. for
C15H15NO2 [M+] 241.11028; found 241.11000.
1-[5-(4-Bromophenoxy)-2-methylbenzofuran-3-yl]ethanone
(24):
1
Yield: 1.53 g, 4.26 mmol, 71%. H NMR (500 MHz, CDCl3): δ =
4
3
7.53 (d, JH,H = 2.6 Hz, 1 H, ArH), 7.49 (d, JH,H = 8.4 Hz, 1 H,
3
1-[5-(5-Bromopentyloxy)-1,2-dimethyl-1H-indol-3-yl]ethanone (19):
ArH), 7.32 (d, 3JH,H = 8.1 Hz, 2 H, ArH), 7.30 (d, JH,H = 8.8 Hz,
1 H, ArH) 6.91 (dd, JH,H = 8.9, JH,H = 2.6 Hz, 1 H, ArH), 5.04
1
3
4
Yield: 1.62 g, 4.62 mmol, 77%. H NMR (500 MHz, CDCl3): δ =
4
3
7.49 (d, JH,H = 2.3 Hz, 1 H, ArH), 7.19 (d, JH,H = 8.8 Hz, 1 H, (s, 2 H, CH2), 2.73 (s, 3 H, CH3), 2.56 (s, 3 H, CH3) ppm. 13C NMR
3
4
ArH), 6.87 (dd, JH,H = 8.8, JH,H = 2.3 Hz, 1 H, ArH), 4.04 (t, (126 MHz, CDCl3): δ = 193.9, 163.4, 155.6, 148.5, 136.0, 131.6,
3JH,H = 6.4 Hz, 2 H, CH2), 3.66 (s, 3 H, CH3), 3.43 (t, JH,H
=
129.1, 126.9, 121.8, 117.9, 113.4, 111.3, 106.0, 70.0, 30.9, 15.6 ppm.
3
6.8 Hz, 2 H, CH2), 2.73 (s, 3 H, CH3), 2.62 (s, 3 H, CH3), 1.94 (m,
MS (EI, 70 eV): m/z (%) =
360 (21) [M(81Br)+], 358 (21)
2 H, CH2), 1.83 (m, 2 H, CH2), 1.65 (m, 2 H, CH2) ppm. 13C NMR [M(79Br)+], 171 (98), 169 (100), 90 (25), 89 (14). HRMS (EI): calcd.
(126 MHz, CDCl3): δ = 194.1, 155.1, 145.0, 131.7, 127.1, 114.0, for C18H15O3Br [M+] 358.02046; found 358.02010.
111.5, 109.9, 104.9, 68.3, 33.7, 32.5, 31.5, 29.6, 28.6, 24.8,
1-[5-(4-Bromobenzyloxy)-1,2-dimethyl-1H-indol-3-yl]ethanone (25):
12.8 ppm. MS (EI, 70 eV): m/z (%) = 353 (37) [M(81Br)+], 351 (37)
Yield:1.47 g, 3.96 mmol, 66%. 1H NMR (500 MHz, CDCl3): δ =
[M(79Br)+], 338 (12), 336 (12), 203 (29), 202 (22), 189 (13), 188
4
3
7.57 (d, JH,H = 2.1 Hz, 1 H, ArH), 7.48 (d, JH,H = 8.3 Hz, 2 H,
(100), 175 (17), 131 (12), 69 (13). HRMS (EI): calcd. for
ArH), 7.32 (d, 3JH,H = 8.2 Hz, 2 H, ArH), 7.16 (d, JH,H = 8.8 Hz,
3
C17H22NO2Br [M+] 351.08339; found 351.07860.
3
4
1 H, ArH), 6.91 (dd, JH,H = 8.8, JH,H = 2.3 Hz, 1 H, ArH), 5.06
(s, 2 H, CH2), 3.61 (s, 3 H, CH3), 2.68 (s, 3 H, CH3), 2.57 (s, 3 H,
CH3) ppm. 13C NMR (126 MHz, CDCl3): δ = 194.0, 154.6, 145.1,
136.4, 131.9, 131.6, 129.1, 127.0, 121.66, 114.1, 111.8, 110.0, 105.4,
70.0, 31.4, 29.6, 12.8 ppm. MS (EI, 70 eV): m/z (%) = 373 (17)
[M(81Br)+], 371 (17) [M(79Br)+], 203 (15), 202 (100), 174 (22).
HRMS (EI): calcd. for C19H18NO2Br [M+] 371.05209; found
371.04990.
1-[5-(Allyloxy)-2-methylbenzofuran-3-yl]ethanone
(20):
Yield:
1.13 g, 4.92 mmol, 82%. 1H NMR (500 MHz, CDCl3): δ = 7.46 (d,
3
4JH,H = 2.5 Hz, 1 H, ArH), 7.29 (d, JH,H = 8.9 Hz, 1 H, ArH),
3
4
3
6.88 (dd, JH,H = 8.9, JH,H = 2.6 Hz, 1 H, ArH), 6.07 (ddt, JH,H
3
3
3
= 17.1, JH,H = 10.6, JH,H = 5.3 Hz, 1 H, CH), 5.43 (dd, JH,H
17.3, JH,H = 1.5 Hz, 1 H, CH), 5.28 (dd, JH,H = 10.5, JH,H
=
=
2
3
2
1.3 Hz, 1 H, CH), 4.57 (dd, 3JH,H = 4.0, 4JH,H = 1.3 Hz, 2 H, CH2),
2.72 (s, 3 H, CH3), 2.57 (s, 3 H, CH3) ppm. 13C NMR (126 MHz,
CDCl3): δ = 194.0, 163.3, 155.7, 148.5, 133.4, 126.8, 117.8, 117.7,
113.3, 111.2, 105.8, 69.7, 30.9, 15.6 ppm. MS (EI, 70 eV): m/z (%)
= 230 (55) [M+], 215 (10), 189 (54), 147 (52), 69 (11). HRMS (EI):
calcd. for C14H14O3 [M+] 230.09429; found 230.09360.
1-[5-(Anthracen-9-yloxy)-2-methylbenzofuran-3-yl]ethanone
(26):
1
Yield: 1.87 g, 4.92 mmol, 82%. H NMR (500 MHz, CDCl3): δ =
3
8.51 (s, 1 H, ArH), 8.31 (d, JH,H = 8.8 Hz, 2 H, ArH), 8.03 (d,
4
3JH,H = 8.2 Hz, 2 H, ArH), 7.77 (d, JH,H = 2.5 Hz, 1 H, ArH),
3
7.54 (m, 2 H, ArH), 7.47 (m, 2 H, ArH), 7.37 (d, JH,H = 8.9 Hz,
3
4
1-[5-(Allyloxy)-1,2-dimethyl-1H-indol-3-yl]ethanone (21): Yield: 2 H, ArH), 7.04 (dd, JH,H = 9.1, JH,H = 2.5 Hz, 1 H, ArH), 6.03
1.17 g, 4.80 mmol, 80%. 1H NMR (500 MHz, CDCl3): δ = 7.51 (d,
(s, 2 H, CH2), 2.77 (s, 3 H, CH3), 2.58 (s, 3 H, CH3) ppm. 13C NMR
(126 MHz, CDCl3): δ = 194.2, 163.5, 156.5, 148.7, 131.5, 131.0,
129.2, 129.0, 127.0, 126.9, 126.6, 125.1, 124.1, 118.0, 113.6, 111.5,
105.9, 63.6, 31.1, 15.7 ppm. MS (EI, 70 eV): m/z (%) = 380 (4)
[M+], 192 (19), 191 (100), 189 (15), 178 (13). HRMS (EI): calcd.
3
4JH,H = 2.3 Hz, 1 H, ArH), 7.15 (d, JH,H = 8.8 Hz, 1 H, ArH),
3
4
3
6.88 (dd, JH,H = 8.8, JH,H = 2.4 Hz 1 H, ArH), 6.09 (ddt, JH,H
3
3
3
= 22.6, JH,H = 10.6, JH,H = 5.4 Hz, 1 H, CH), 5.44 (dd, JH,H
=
=
2
3
2
17.3, JH,H = 1.5 Hz, 1 H, CH), 5.28 (dd, JH,H = 10.5, JH,H
1.3 Hz, 1 H, CH), 4.59 (m, 2 H, CH2), 3.59 (s, 3 H, CH3), 2.67 (s, for C26H20O3 [M+] 380.14124; found 380.13820.
3 H, CH3), 2.58 (s, 3 H, CH3) ppm. 13C NMR (126 MHz, CDCl3):
1-[5-(Anthracen-9-ylmethoxy)-1,2-dimethyl-1H-indol-3-yl]ethanone
δ = 194.0, 154.7, 145.1, 133.7, 131.8, 127.0, 117.5, 114.0, 111.6,
109.9, 105.2, 69.6, 31.4, 29.5, 12.8 ppm. MS (EI, 70 eV): m/z (%) =
243 (39) [M+], 203 (14), 202 (100), 174 (38), 131 (11). HRMS (EI):
calcd. for C15H17NO2 [M+] 243.12593; found 243.12510.
(27): Yield: 1.65 g, 4.20 mmol, 70%. 1H NMR (500 MHz, CDCl3):
3
δ = 8.51 (s, 1 H, ArH), 8.34 (d, JH,H = 8.9 Hz, 2 H, ArH), 8.03
(d, 3JH,H = 8.3 Hz, 2 H, ArH), 7.82 (d, 4JH,H = 2.4 Hz, 1 H, ArH),
3
7.52 (m, 2 H, ArH), 7.48 (m, 2 H, ArH), 7.25 (d, JH,H = 8.7 Hz,
3
4
1-[2-Methyl-5-(prop-2-ynyloxy)benzofuran-3-yl]ethanone
Yield: 1.08 g, 4.74 mmol, 79%. H NMR (500 MHz, CDCl3): δ =
(22):
2 H, ArH), 7.05 (dd, JH,H = 8.8, JH,H = 2.4 Hz, 1 H, ArH), 6.05
1
(s, 2 H, CH2), 3.69 (s, 3 H, CH3) 2.76 (s, 3 H, CH3), 2.61 (s, 3 H,
4
3
7.54 (d, JH,H = 2.6 Hz, 1 H, ArH), 7.31 (d, JH,H = 8.9 Hz, 1 H, CH3) ppm. 13C NMR (126 MHz, CDCl3): δ = 194.2, 155.4, 145.1,
3
4
ArH), 6.92 (dd, JH,H = 8.9, JH,H = 2.6 Hz, 1 H, ArH), 4.72 (d,
131.9, 131.4, 130.9, 129.0, 128.7, 127.3, 127.1, 126.4, 125.0, 124.1,
114.1, 111.9, 110.1, 105.2, 63.5, 31.5, 29.5, 12.8 ppm. MS (EI,
70 eV): m/z (%) = 394 (13), 393 (43) [M+], 216 (13), 215 (78), 203
(14), 192 (19), 191 (75), 189 (20), 188 (32), 187 (15), 179 (16), 178
(100). HRMS (EI): calcd. for C27H23NO2 [M+] 393.17288; found
393.17330.
4JH,H = 2.4 Hz, 2 H, CH2), 2.72 (s, 3 H, CH3), 2.57 (s, 3 H, CH3),
4
2.51 (t, JH,H = 2.4 Hz, 1 H, CH) ppm. 13C NMR (126 MHz,
CDCl3): δ = 193.9, 163.5, 154.6, 148.8, 126.8, 117.8, 113.5, 111.3,
106.39, 78.7, 75.5, 56.7, 30.9, 15.6 ppm. MS (EI, 70 eV): m/z (%) =
228 (43) [M+], 227 (20), 213 (19), 200 (13), 189 (29), 185 (22), 147
(41). HRMS (EI): calcd. for C14H12O3 [M+] 228.07864; found
228.07770.
1-(6-Bromo-5-methoxy-2-methylbenzofuran-3-yl)ethanone (28):
1
Yield: 1.29 g, 4.56 mmol, 76%. H NMR (500 MHz, [D6]DMSO):
1-[1,2-Dimethyl-5-(prop-2-ynyloxy)-1H-indol-3-yl]ethanone
(23): δ = 7.84 (s, 1 H, ArH), 7.51 (s, 1 H, ArH), 3.87 (s, 3 H, CH3), 2.72
Yield: 1.10 g, 4.56 mmol, 76%. H NMR (500 MHz, CDCl3): δ = (s, 3 H, CH3), 2.56 (s, 3 H, CH3) ppm. 13C NMR (126 MHz, [D6]-
1
4650
www.eurjoc.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 4645–4653

Functionalized Fulgides and Fluorophore-Photoswitch Conjugates
DMSO): δ = 193.6, 163.7, 152.5, 147.0, 126.1, 117.1, 115.1, 107.6,
103.5, 56.5, 30.8, 15.4 ppm. MS (EI, 70 eV): m/z (%) = 285 (12),
CH3), 0.92 (s, 3 H, CH3) ppm. 13C NMR (126 MHz, CDCl3): δ =
164.1, 163.8, 154.7, 153.1, 149.4, 136.1, 132.0, 125.0, 121.5, 118.4,
284 (90) [M(81Br)+], 283 (19), 282 (92) [M(79Br)+], 270 (12), 269 116.4, 111.7, 110.0, 101.8, 55.7, 30.0, 26.2, 23.6, 22.6, 12.3 ppm.
(97), 268 (13), 267 (100). HRMS (EI): calcd. for C12H11O3Br [M+]
281.98916; found 281.98900.
MS (EI, 70 eV): m/z (%) = 340 (22), 339 (100) [M+], 324 (14), 296
(23), 294 (13), 280 (13), 266 (37), 252 (30), 240 (12), 200 (20), 175
(53). HRMS (EI): calcd. for C20H21NO4 [M+] 339.14706; found
339.14500.
1-(6-Bromo-5-methoxy-1,2-dimethyl-1H-indol-3-yl)ethanone (29):
1
Yield: 1.49 g, 5.04 mmol, 84%. H NMR (500 MHz, CDCl3): δ =
7.56 (s, 1 H, ArH), 7.40 (s, 1 H, ArH), 3.92 (s, 3 H, CH3), 3.57 (s, (E)-4-(3-{1-[2,5-Dioxo-4-(propan-2-ylidene)dihydrofuran-3(2H)-
3 H, CH3), 2.65 (s, 3 H, CH3), 2.55 (s, 3 H, CH3) ppm. 13C NMR
ylidene]ethyl}-2-methylbenzofuran-5-yloxy)butanoic Acid (32):
(126 MHz, CDCl3): δ = 193.7, 151.7, 144.8, 131.8, 126.3, 114.2, Yield: 239 mg, 0.6 mmol, 6%. H NMR (500 MHz, [D6]DMSO): δ
1
3
113.7, 106.8, 103.5, 56.7, 31.3, 29.8, 12.9 ppm. MS (EI, 70 eV): m/z
(%) = 297 (66) [M(81Br)+], 295 (67) [M(79Br)+], 283 (13), 282 (98),
281 (14), 280 (100), 267 (12), 265 (12), 173 (17), 130 (17). HRMS
(EI): calcd. for C13H14NO2Br [M+] 295.02079; found 295.01880.
= 12.13 (s, 1 H, COOH), 7.41 (d, JH,H = 8.9 Hz, 1 H, ArH), 7.01
4
3
4
(d, JH,H = 2.5 Hz, 1 H, ArH), 6.86 (dd, JH,H = 8.9, JH,H
=
2.5 Hz, 1 H, ArH), 3.97 (m, 2 H, CH2), 2.67 (s, 3 H, CH3), 2.37 (t,
3JH,H = 7.3 Hz, 2 H, CH3), 2.24 (s, 3 H, CH3), 2.15 (s, 3 H, CH3),
3
1.92 (p, JH,H = 6.7 Hz, 2 H, CH2), 1.05 (s, 3 H, CH3) ppm.
General Preparation of Fulgides:[11] A solution of diethyl isopropyl-
idenesuccinate[12] (15 mmol) in dry THF (15 mL) was cooled to
–78 °C, and LDA (7.5 mL, 15 mmol; 2 m, THF/n-heptane/ethylben-
zene) was added under argon. After stirring for 1 h, the appropriate
ketone (10 mmol) dissolved in THF (30 mL) was added via syringe.
The reaction mixture was warmed to room temperature overnight
and stirred for an additional 24 h. The reaction progress was moni-
tored by TLC. The reaction mixture was acidified with aqueous
HCl (2 m), and the aqueous layer was extracted with ethyl acetate
(3ϫ50 mL). The combined organic layers were washed with satu-
rated aqueous NaCl solution, dried with MgSO4, and the solvent
was removed in vacuo. The residue was dissolved in cyclohexane/
13C NMR (126 MHz, [D6]DMSO): δ = 174.1, 163.5, 162.9, 155.0,
154.7, 153.7, 148.1, 144.1, 126.4, 121.2, 120.5, 119.2, 113.1, 111.4,
104.0,67.2, 30.1, 26.1, 24.2, 22.1, 21.7, 13.6 ppm. MS (EI, 70 eV):
m/z (%) = 399 (26), 398 (100) [M+], 383 (24), 381 (45), 339 (26),
312 (73), 311 (23), 297 (71), 295 (46), 269 (30), 268 (22), 267 (33),
253 (32), 251 (22), 239 (24), 225 (37), 232 (25), 165 (25), 152 (23),
148 (31). HRMS (EI): calcd. for C22H22O7 [M+] 398.13655; found
398.13500.
(E)-4-(3-{1-[2,5-Dioxo-4-(propan-2-ylidene)dihydrofuran-3(2H)-
ylidene]ethyl}-1,2-dimethyl-1H-indol-5-yloxy)butanoic Acid (33):
Yield: 288 mg, 0.7 mmol, 7%. 1H NMR (500 MHz, CDCl3): δ =
3
3
4
ethyl acetate (7:3), filtered through silica gel, and the solvent was 7.15 (d, JH,H = 8.8 Hz, 1 H, ArH), 6.83 (dd, JH,H = 8.8, JH,H
=
4
removed in vacuo again. The residue was dissolved in ethanol
(60 mL), and a saturated aqueous solution of KOH (5 mL) was
added. After stirring for 20 h at 70 °C, the reaction mixture was
poured onto ice and acidified with aqueous HCl (2 m). The aque-
ous layer was extracted with ethyl acetate (3 ϫ 50 mL), and the
combined organic layers were washed with saturated aqueous
NaCl, dried with MgSO4, and the solvent was removed in vacuo.
The dark brown residue was dissolved in dichloromethane (50 mL),
and N,NЈ-dicyclohexylcarbodiimide (DCC) (4.13 g, 20 mmol) was
added. After stirring for 48 h, the reaction mixture was filtered
2.3 Hz, 1 H, ArH), 6.74 (d, JH,H = 2.2 Hz, 1 H, ArH), 3.99 (m, 2
H, CH2), 3.64 (s, 3 H, CH3), 2.77 (s, 3 H, CH3), 2.59 (t, JH,H
3
=
7.2 Hz, 2 H, CH3), 2.19 (s, 3 H, CH3), 2.17 (s, 3 H, CH3), 2.11 (m,
2 H, CH2), 0.92 (s, 3 H, CH3) ppm. 13C NMR (126 MHz, [D6]-
DMSO): δ = 174.2, 163.9, 163.5, 153.3, 152.3, 149.1, 137.4, 131.8,
124.8, 121.2, 117.4, 115.5, 111.4, 110.6, 102.7, 67.0, 30.2, 29.9, 25.7,
24.4, 23.4, 22.1, 12.0 ppm. MS (EI, 70 eV): m/z (%) = 412 (24), 411
(81) [M+], 394 (16), 352 (19), 325 (35), 324 (20), 321 (21), 308 (20),
307 (18), 282 (19), 280 (18), 266 (24), 264 (20), 252 (28), 238 (24),
161 (50). HRMS (EI): calcd. for C23H25NO6 [M+] 411.16819; found
through silica gel, and the solvent was removed in vacuo. The prod- 411.16740.
ucts were purified by column chromatography with mixtures of cy-
(E)-3-{1-[5-(5-Ethoxypentyloxy)-2-methylbenzofuran-3-yl]ethyl-
clohexane and ethyl acetate as eluent. Benzofuryl fulgides were
recrystallized from cyclohexane or diethyl ether and indolyl ful-
gides were recrystallized from 2-propanol.
idene}-4-(propan-2-ylidene)dihydrofuran-2,5-dione (34): Yield:
1
213 mg, 0.5 mmol, 5%. H NMR (500 MHz, CDCl3): δ = 7.27 (d,
3
4
3JH,H = 8.9 Hz, 1 H, ArH), 6.84 (dd, JH,H = 8.9, JH,H = 2.5 Hz,
(E)-3-[1-(5-Methoxy-2-methylbenzofuran-3-yl)ethylidene]-4-(propan- 1 H, ArH), 6.71 (d, 4JH,H = 2.5 Hz, 1 H, ArH), 3.92 (m, 2 H, CH2),
3
3
2-ylidene)dihydrofuran-2,5-dione (30): Yield: 325 mg, 1.0 mmol,
3.45 (q, JH,H = 7.0 Hz, 2 H, CH2), 3.42 (t, JH,H = 6.5 Hz, 2 H,
CH2), 2.72 (s, 3 H, CH3), 2.23 (s, 3 H, CH3), 2.20 (s, 3 H, CH3),
1.80 (m, 2 H, CH2), 1.64 (m, 2 H, CH2), 1.53 (m, 2 H, CH2), 1.18
1
3
7%. H NMR (500 MHz, CDCl3): δ = 7.29 (d, JH,H = 9.4 Hz, 1
3
4
H, ArH), 6.85 (dd, JH,H = 9.4, JH,H = 2.5 Hz, 1 H, ArH), 6.70
(d, JH,H = 2.5 Hz, 1 H, ArH), 3.79 (s, 3 H, CH3), 2.72 (s, 3 H,
(t, JH,H = 7.0 Hz, 3 H, CH3), 1.12 (s, 3 H, CH3) ppm. 13C NMR
4
3
CH3), 2.23 (s, 6 H, CH3), 1.12 (s, 3 H, CH3) ppm. 13C NMR (126 MHz, CDCl3): δ = 163.5, 162.9, 155.7, 155.4, 153.2, 148.8,
(126 MHz, CDCl3): δ = 163.6, 163.0, 156.2, 155.5, 153.5, 148.9, 145.1, 126.5, 121.4, 120.7, 119.5, 113.2, 111.5, 103.6, 70.5, 68.6,
145.0, 126.5, 121.5, 120.8, 119.6, 112.9, 111.6, 102.8, 55.9, 26.7,
22.7, 22.0, 14.0 ppm. MS (EI, 70 eV): m/z (%) = 327 (22), 326 (100)
[M+], 311 (43), 309 (12), 283 (20), 281 (12), 267 (41), 265 (15), 253
(13), 239 (17), 223 (11), 204 (11), 165 (11), 162 (21), 152 (12), 115
(13), 106 (12), 91 (12), 77 (10). HRMS (ESI): calcd. for
C1 9 H1 8 O5 Na+ 349.10464; found 349.10480; calcd. for
(C19H18O5)2Na+ 675.22026; found 675.22007.
66.1, 29.5, 29.2, 26.7, 22.8, 22.7, 21.9, 15.2, 14.0 ppm. MS (EI,
70 eV): m/z (%) = 426 (31) [M+], 297 (12), 115 (100), 69 (66).
HRMS (EI): calcd. for C25H30O6 [M+] 426.20424; found 426.20280.
(E)-3-{1-[5-(5-Ethoxypentyloxy)-1,2-dimethyl-1H-indol-3-yl]ethyl-
idene}-4-(propan-2-ylidene)dihydrofuran-2,5-dione (35): Yield:
1
351 mg, 0.8 mmol, 8%. H NMR (500 MHz, CDCl3): δ = 7.15 (d,
3
4
3JH,H = 8.8 Hz, 1 H, ArH), 6.84 (dd, JH,H = 8.8, JH,H = 2.4 Hz,
(E)-3-[1-(5-Methoxy-1,2-dimethyl-1H-indol-3-yl)ethylidene]-4-
(propan-2-ylidene)dihydrofuran-2,5-dione (31): Yield: 305 mg,
1 H, ArH), 6.74 (d, 4JH,H = 2.3 Hz, 1 H, ArH), 3.93 (m, 2 H, CH2),
3
3.63 (s, 3 H, CH3), 3.45 (q, JH,H = 7.0 Hz, 2 H, CH2), 3.43 (t,
1
3
0.9 mmol, 9%. H NMR (500 MHz, CDCl3): δ = 7.16 (d, JH,H
=
3JH,H = 6.6 Hz, 2 H, CH2), 2.77 (s, 3 H, CH3), 2.18 (s, 6 H, CH3),
3
4
8.8 Hz, 1 H, ArH), 6.84 (dd, JH,H = 8.8, JH,H = 2.4 Hz, 1 H,
1.80 (m, 2 H, CH2), 1.64 (m, 2 H, CH2), 1.52 (m, 2 H, CH2), 1.18
ArH), 6.71 (d, 4JH,H = 2.3 Hz, 1 H, ArH), 3.78 (s, 3 H, CH3), 3.65 (t, JH,H = 7.0 Hz, 3 H, CH3), 0.92 (s, 3 H, CH3) ppm. 13C NMR
3
(s, 3 H, CH3), 2.77 (s, 3 H, CH3), 2.21 (s, 3 H, CH3), 2.17 (s, 3 H, (126 MHz, CDCl3): δ = 164.1, 163.8, 154.2, 152.9, 149.5, 135.9,
Eur. J. Org. Chem. 2011, 4645–4653
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4651

F. Strübe, S. Rath, J. Mattay
FULL PAPER
132.0, 125.2, 121.6, 118.5, 116.4, 112.2, 109.9, 102.9, 70.5, 68.5,
66.1, 30.0, 29.6, 29.3, 26.2, 23.6, 22.8, 22.7, 15.2, 12.2 ppm. MS
(EI, 70 eV): m/z (%) = 440 (29), 439 (100) [M+], 252 (17), 161 (14),
(E)-3-{1-[5-(4-Bromobenzyloxy)-1,2-dimethyl-1H-indol-3-yl]ethyl-
idene}-4-(propan-2-ylidene)dihydrofuran-2,5-dione (41): Yield:
740 mg, 1.5 mmol, 15%. 1H NMR (500 MHz, CDCl3): δ = 7.48 (d,
3
115 (53), 69 (38), 59 (28). HRMS (EI): calcd. for C26H33NO5 [M+] 3JH,H = 8.3 Hz, 2 H, ArH), 7.31 (d, JH,H = 8.3 Hz, 2 H, ArH),
3
3
4
439.23587; found 439.23450.
7.17 (d, JH,H = 8.8 Hz, 1 H, ArH), 6.91 (dd, JH,H = 8.8, JH,H =
4
2.3 Hz, 1 H, ArH), 6.80 (d, JH,H = 2.2 Hz, 1 H, ArH), 4.99 (s, 2
H, CH2), 3.64 (s, 3 H, CH3), 2.75 (s, 3 H, CH3), 2.19 (s, 3 H, CH3),
2.18 (s, 3 H, CH3), 0.92 (s, 3 H, CH3) ppm. 13C NMR (126 MHz,
CDCl3): δ = 164.1, 163.8, 153.6, 153.0, 149.3, 136.3, 136.1, 132.3,
131.6, 129.1, 125.1, 121.7, 121.6, 118.7, 116.4, 112.4, 110.1, 103.6,
70.0, 30.0, 26.2, 23.6, 22.7, 12.3 ppm. MS (EI, 70 eV): m/z (%) =
495 (32) [M(81Br)+], 493 (32) [M(79Br)+], 325 (23), 324 (100), 306
(11), 296 (24), 280 (22), 278 (11), 253 (16), 252 (75), 236 (10), 208
(12), 171 (17), 169 (18). HRMS (EI): calcd. for C26H24NO4Br [M+]
493.08887; found 493.08740.
(E)-3-{1-[5-(Allyloxy)-2-methylbenzofuran-3-yl]ethylidene}-4-
(propan-2-ylidene)dihydrofuran-2,5-dione (36): Yield: 387 mg,
1.1 mmol, 11%. 1H NMR (500 MHz, CDCl3): δ = 7.29 (d, 3JH,H
=
3
4
8.9 Hz, 1 H, ArH), 6.88 (dd, JH,H = 8.9, JH,H = 2.5 Hz, 1 H,
4
3
ArH), 6.75 (d, JH,H = 2.5 Hz, 1 H, ArH), 6.04 (ddt, JH,H = 17.2,
3JH,H = 10.5, JH,H = 5.3 Hz, 1 H, CH), 5.40 (ddd, JH,H = 17.3,
3
3
4JH,H = 3.1, JH,H = 1.5 Hz, 1 H, CH), 5.28 (dd, JH,H = 10.5,
2JH,H = 1.4 Hz, 1 H, CH), 4.51 (m, 2 H, CH2), 2.72 (s, 3 H, CH3),
2.23 (s, 3 H, CH3), 2.22 (s, 3 H, CH3), 1.13 (s, 3 H, CH3) ppm.
13C NMR (126 MHz, CDCl3): δ = 163.5, 162.9, 155.5, 155.2, 153.3,
149.0, 145.0, 133.2, 126.5, 121.5, 120.7, 119.5, 117.8, 113.5, 111.6,
104.0, 69.7, 26.7, 22.7, 22.0, 14.0 ppm. MS (EI, 70 eV): m/z (%) =
353 (23), 352 (100) [M+], 337 (15), 312 (13), 311 (61), 293 (20), 283
(22), 268 (13), 267 (56), 265 (12), 239 (16), 165 (13), 152 (13), 115
(11). HRMS (EI): calcd. for C21H20O5 [M+] 352.13107; found
352.12900.
2
3
(E)-3-{1-[5-(Anthracen-9-ylmethoxy)-2-methylbenzofuran-3-yl]ethyl-
idene}-4-(propan-2-ylidene)dihydrofuran-2,5-dione (42): Yield:
1
502 mg, 1.0 mmol, 10%. H NMR (500 MHz, CDCl3): δ = 8.50 (s,
3
3
1 H, ArH), 8.28 (d, JH,H = 8.6 Hz, 2 H, ArH), 8.02 (d, JH,H
=
8.3 Hz, 2 H, ArH), 7.53 (m, 2 H, ArH), 7.47 (m, 2 H, ArH), 7.34
(d, 3JH,H = 9.6 Hz, 1 H, ArH), 7.04 (dd, 3JH,H = 6.4, 4JH,H = 2.5 Hz
2 H, ArH), 5.96 (s, 2 H, CH2), 2.69 (s, 3 H, CH3), 2.29 (s, 3 H,
CH3), 2.21 (s, 3 H, CH3), 1.16 (s, 3 H, CH3) ppm. 13C NMR
(126 MHz, CDCl3): δ = 163.2, 160.9, 157.2, 155.6, 154.4, 149.2,
143.7, 131.4, 130.9, 129.1, 128.9, 127.8, 127.0, 126.5, 125.0, 124.0,
122.8, 121.3, 114.9, 112.5, 111.7, 104.5, 63.7, 27.2, 24.0, 22.4,
13.6 ppm. MS (EI, 70 eV): m/z (%) = 502 (12) [M+], 192 (28), 191
(62), 189 (12), 179 (17), 178 (100). HRMS (EI): calcd. for C33H26O5
[M+] 502.17802; found 502.17650.
(E)-3-{1-[5-(Allyloxy)-1,2-dimethyl-1H-indol-3-yl]ethylidene}-4-(prop-
an-2-ylidene)dihydrofuran-2,5-dione (37): Yield: 292 mg, 0.8 mmol,
1
3
8%. H NMR (500 MHz, CDCl3): δ = 7.16 (d, JH,H = 8.8 Hz, 1
3
4
H, ArH), 6.88 (dd, JH,H = 8.8, JH,H = 2.4 Hz, 1 H, ArH), 6.77
4
3
3
(d, JH,H = 2.3 Hz, 1 H, ArH), 6.06 (ddt, JH,H = 17.1, JH,H
=
=
3
3
2
10.5, JH,H = 5.3 Hz, 1 H, CH), 5.41 (dd, JH,H = 17.3, JH,H
3
2
1.6 Hz, 1 H, CH), 5.26 (dd, JH,H = 10.5, JH,H = 1.4 Hz, 1 H,
CH), 4.51 (d, JH,H = 5.2 Hz, 2 H, ArH), 3.64 (s, 3 H, CH3), 2.77
3
(E)-3-{1-[5-(Anthracen-9-ylmethoxy)-1,2-dimethyl-1H-indol-3-yl]-
ethylidene}-4-(propan-2-ylidene)dihydrofuran-2,5-dione (43): Yield:
(s, 3 H, CH3), 2.18 (s, 3 H, CH3), 2.18 (s, 3 H, CH3) ppm. 13C NMR
(126 MHz, CDCl3): δ = 164.2, 163.8, 153.8, 153.1, 149.4, 136.0,
133.6, 132.2, 125.2, 121.5, 118.6, 117.5, 116.4, 112.3, 110.0, 103.3,
69.6, 30.0, 26.2, 23.6, 22.7, 12.3 ppm. MS (EI, 70 eV): m/z (%) =
366 (25), 365 (100) [M+], 324 (51), 296 (26), 280 (17), 278 (16), 252
(62), 226 (17), 208 (16). HRMS (EI): calcd. for C22H23NO4 [M+]
365.16271; found 365.16080.
1
412 mg, 0.8 mmol, 8%. H NMR (500 MHz, CDCl3): δ = 8.49 (s,
3
3
1 H, ArH), 8.32 (d, JH,H = 8.8 Hz, 2 H, ArH), 8.02 (d, JH,H
=
8.3 Hz, 2 H, ArH), 7.51 (m, 2 H, ArH), 7.46 (m, 2 H, ArH), 7.20
(d, 3JH,H = 8.8 Hz, 1 H, ArH), 7.11 (d, 4JH,H = 2.2 Hz, 1 H, ArH),
3
4
2
6.99 (dd, JH,H = 8.8, JH,H = 2.3 Hz, 1 H, ArH), 5.97 (d, JH,H
=
2
10.8 Hz, 1 H, CH2), 5.94 (d, JH,H = 10.8 Hz, 1 H, CH2), 3.64 (s,
3 H, CH3), 2.78 (s, 3 H, CH3), 2.27 (s, 3 H, CH3), 2.19 (s, 3 H,
CH3), 0.97 (s, 3 H, CH3) ppm. 13C NMR (126 MHz, CDCl3): δ =
164.1, 163.8, 154.3, 153.0, 149.5, 136.0, 132.4, 131.4, 131.0, 129.0,
128.8, 127.2, 126.4, 125.2, 125.0, 124.0, 121.6, 118.5, 116.5, 112.7,
110.1, 103.6, 63.6, 30.0, 26.3, 23.5, 22.7, 12.3 ppm. MS (EI, 70 eV):
m/z (%) = 515 (11) [M+], 325 (22), 252 (11), 192 (47), 191 (100),
189 (21), 178 (44). HRMS (EI): calcd. for C34H29NO4 [M+]
515.20966; found 515.21080.
(E)-3-{1-[1,2-Dimethyl-5-(prop-2-ynyloxy)-1H-indol-3-yl]ethyl-
idene}-4-(propan-2-ylidene)dihydrofuran-2,5-dione (39): Yield:
254 mg, 0.7 mmol, 7%. 1H NMR (500 MHz, CDCl3): δ = 7.18 (m,
1 H, ArH), 6.91 (m, 2 H, ArH), 4.66 (d, 4JH,H = 2.3 Hz, 2 H, CH2),
3
3.65 (s, 3 H, CH3), 2.77 (s, 3 H, CH3), 2.51 (t, JH,H = 2.3 Hz, 1
H, CH), 2.18 (s, 3 H, CH3), 0.93 (s, 3 H, CH3) ppm. 13C NMR
(126 MHz, CDCl3): δ = 164.1, 163.8, 153.2, 152.8, 149.3, 136.1,
132.6, 125.1, 121.5, 118.8, 116.5, 112.4, 110.0, 104.0, 78.8, 75.5,
56.9, 30.0, 26.3, 23.6, 22.7, 12.3 ppm. MS (EI, 70 eV): m/z (%) =
364 (25), 363 (100) [M+], 324 (28), 320 (13), 296 (16), 276 (13), 252
(39), 224 (18), 208 (13), 199 (17). HRMS (EI): calcd. for
C22H21NO4 [M+] 363.14706; found 363.14580.
(E)-3-[1-(6-Bromo-5-methoxy-2-methylbenzofuran-3-yl)ethylidene]-
4-(propan-2-ylidene)dihydrofuran-2,5-dione (44): Yield:285 mg,
0.7 mmol, 7 %. 1H NMR (500 MHz, CDCl3): δ = 7.61 (s, 1 H,
ArH), 6.65 (s, 1 H, ArH), 3.86 (s, 3 H, CH3), 2.72 (s, 3 H, CH3),
2.27 (s, 3 H, CH3), 2.22 (s, 3 H, CH3), 1.12 (s, 3 H, CH3) ppm.
13C NMR (126 MHz, CDCl3): δ = 163.4, 162.8, 155.8, 154.2, 152.5,
148.4, 144.0, 125.5, 121.9, 120.7, 119.5, 115.9, 108.7, 101.8, 56.8,
26.6, 22.7, 22.0, 14.1 ppm. MS (EI, 70 eV): m/z (%) = 407 (20), 406
(100), 405 (22), 404 (100), 391 (26), 389 (34), 363 (16), 361 (22),
347 (32), 345 (40), 310 (17), 165 (22), 152 (17). HRMS (EI): calcd.
for C19H17O5Br [M+] 404.02594; found 404.02450.
(E)-3-{1-[5-(4-Bromobenzyloxy)-2-methylbenzofuran-3-yl]ethyl-
idene}-4-(propan-2-ylidene)dihydrofuran-2,5-dione (40): Yield:
624 mg, 1.3 mmol, 13%. 1H NMR (500 MHz, CDCl3): δ = 7.49 (d,
3
3JH,H = 8.4 Hz, 2 H, ArH), 7.30 (m, 3 H, ArH), 6.92 (dd, JH,H
=
8.9, 4JH,H = 2.5 Hz, 1 H, ArH), 6.78 (d, 4JH,H = 2.5 Hz, 1 H, ArH),
4.99 (s, 2 H, CH2), 2.70 (s, 3 H, CH3), 2.23 (s, 3 H, CH3), 2.22 (s,
3 H, CH3), 1.12 (s, 3 H, CH3) ppm. 13C NMR (126 MHz, CDCl3):
δ = 163.5, 162.9, 155.5, 155.0, 153.5, 149.1, 144.8, 135.2, 131.7,
129.1, 126.5, 121.9, 121.5, 120.7, 119.5, 113.5, 111.7, 104.3, 70.1,
(E)-3-[1-(6-Bromo-5-methoxy-1,2-dimethyl-1H-indol-3-yl)ethyl-
idene]-4-(propan-2-ylidene)dihydrofuran-2,5-dione (45): Yield:
1
26.7, 22.7, 21.9, 14.0 ppm. MS (EI, 70 eV): m/z (%) = 482 (18) 375 mg, 0.9 mmol, 9%. H NMR (500 MHz, CDCl3): δ = 7.47 (s,
[M(81Br)+], 480 (18) [M(79Br)+], 311 (20), 267 (15), 171 (97), 169 1 H, ArH), 6.66 (s, 1 H, ArH), 3.84 (s, 3 H, CH3), 3.63 (s, 3 H,
(100), 90 (22), 89 (12). HRMS (EI): calcd. for C25H21O5Br [M+]
480.05724; found 480.05550.
CH3), 2.75 (s, 3 H, CH3), 2.24 (s, 3 H, CH3), 2.16 (s, 3 H, CH3),
0.91 (s, 3 H, CH3) ppm. 13C NMR (126 MHz, CDCl3): δ = 164.0,
4652
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 4645–4653

Functionalized Fulgides and Fluorophore-Photoswitch Conjugates
163.6, 153.5, 150.7, 148.4, 136.7, 132.0, 124.0, 121.4, 119.1, 116.4,
113.9, 107.0, 101.7, 56.6, 30.1, 26.1, 23.7, 22.6, 12.3 ppm. MS (EI,
70 eV): m/z (%) = 420 (23), 419 (100) [M(81Br)+], 418 (24), 417
(100) [M(79Br)+], 402 (23), 376 (20), 374 (33), 346 (27), 344 (24),
332 (28), 330 (31), 321 (24), 280 (24), 278 (24), 265 (26), 255 (45),
253 (47). HRMS (EI): calcd. for C20H20NO4Br [M+] 417.05757;
found 417.05740.
[1]
[2]
a) B. L. Feringa, Molecular switches, Wiley-VCH, Weinheim,
2003; b) H. Dürr, H. Bouas-Laurent, Photochromism: Mole-
cules and Systems, Elsevier, Amsterdam, 2006.
a) A. S. Dvornikov, E. P. Walker, P. M. Rentzepis, J. Phys.
Chem. A 2009, 113, 13633–13644; b) Y. Chen, T. Li, M. Fan,
X. Mai, H. Zhao, D. Xu, Mater. Sci. Eng. B 2005, 123, 53–56;
c) S. Kawata, Y. Kawata, Chem. Rev. 2000, 100, 1777–1788.
a) J. Fölling, S. Polyakova, V. Belov, A. van Blaaderen, M. L.
Bossi, S. W. Hell, Small 2008, 4, 134–142; b) F. M. Raymo, M.
Tomasulo, Chem. Soc. Rev. 2005, 34, 327.
a) H. Mizuno, P. Dedecker, R. Ando, T. Fukano, J. Hofkens,
A. Miyawaki, Photochem. Photobiol. Sci. 2010, 9, 239; b) J.
Cusido, E. Deniz, F. M. Raymo, Eur. J. Org. Chem. 2009, 2031–
2045.
a) S. Malkmus, F. O. Koller, S. Draxler, T. E. Schrader, W. J.
Schreier, T. Brust, J. A. DiGirolamo, W. J. Lees, W. Zinth, M.
Braun, Adv. Funct. Mater. 2007, 17, 3657–3662; b) B. Yao, Y.
Wang, N. Menke, M. Lei, Y. Zheng, L. Ren, G. Chen, Y. Chen,
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Yokoyama, Chem. Rev. 2000, 100, 1717–1740.
(E)-3-[1-(5-{[1-(Anthracen-9-ylmethyl)-1H-1,2,3-triazol-4-yl]meth-
oxy}-1,2-dimethyl-1H-indol-3-yl)ethylidene]-4-(propan-2-ylidene)-
dihydrofuran-2,5-dione (48): Alkyne indolyl fulgide 39 (53 mg,
0.15 mmol) was dissolved in chloroform (20 mL), and 46 (75 mg,
0.31 mmol) and [Cu(PPh3)3Br] (20 mg, 0.02 mmol) were added. Af-
ter stirring for 20 h at room temperature the solvent was removed
in vacuo, and the residue was purified by column chromatography
to give 48 as a yellow solid. Yield: 46 mg, 0.07 mmol, 48 %.
1H NMR (500 MHz, [D6]DMSO): δ = 8.73 (s, 1 H, ArH), 8.60 (d,
[3]
[4]
[5]
3
3
(
= 8.7 Hz, 2 H, ArH), 8.15 (d, JH,H = 8.4 Hz, 2 H, ArH),
H,H
3
7.63 (m, 2 H, ArH), 7.56 (m, 2 H, ArH), 7.30 (d, JH,H = 8.8 Hz,
1 H, ArH), 6.92 (d, JH,H = 2.2 Hz, 1 H, ArH), 6.74 (dd, JH,H
4
3
=
4
8.9, JH,H = 2.3 Hz, 1 H, ArH),6.64 (m, 2 H, CH2), 5.75 (s, 1 H,
CH), 5.03 (d, 2JH,H = 11.9 Hz, 1 H, CH2), 4.92 (d, 2JH,H = 11.9 Hz,
1 H, CH2), 3.62 (s, 3 H, CH3), 2.62 (s, 3 H, CH3), 2.13 (s, 3 H,
CH3), 2.09 (s, 3 H, CH3), 0.76 (s, 3 H, CH3) ppm. 13C NMR
(126 MHz, [D6]DMSO): δ = 164.3, 164.0, 153.3, 152.7, 149.5,
143.4, 137.7, 132.4, 131.5, 130.8, 129.6, 127.6, 126.2, 125.9, 125.3,
124.5, 124.5, 121.6, 117.8, 115.9, 111.9, 111.0, 103.5, 55.4, 46.0,
30.3, 26.1, 26.0, 23.6, 22.6, 12.5 ppm. MS (ESI): m/z = 619 [M –
[6]
[7]
V. A. Barachevsky, Y. P. Strokach, Y. A. Puankov, M. M.
Krayushkin, J. Phys. Org. Chem. 2007, 20, 1007–1020.
a) A. P. Glaze, H. G. Heller, J. Whittall, J. Chem. Soc. Perkin
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T. I. Mukhanova, L. M. Alekseeva, E. F. Kuleshova, Y. N.
Sheinker, V. G. Granik, Pharm. Chem. J. 1993, 27, 136–142.
[8]
[9]
+
H + Na+]. HRMS (EI): calcd. for C37H33N4O4 597.24963; found
597.24967; calcd for C37H32N4O4Na+ 619.23158; found 619.23168.
[10]
[11]
(E)-3-{1-[5-({1-[(7-Methoxy-2-oxo-2H-chromen-4-yl)methyl]-1H-
1,2,3-triazol-4-yl}methoxy)-1,2-dimethyl-1H-indol-3-yl]ethylidene}-
4-(propan-2-ylidene)dihydrofuran-2,5-dione (49): Alkyne indolyl ful-
gide 39 (53 mg, 0.15 mmol) was dissolved in chloroform (20 mL),
and 47 (58 mg, 0.25 mmol) and [Cu(PPh3)3Br] (20 mg, 0.02 mmol)
were added. After stirring for 25 h at room temperature the solvent
was removed in vacuo, and the residue was purified by column
chromatography to give 49 as a yellow solid. Yield: 50 mg,
0.09 mmol, 60%. 1H NMR (500 MHz, CDCl3): δ = 7.72 (s, 1 H,
C. J. Thomas, M. A. Wolak, R. R. Birge, W. J. Lees, J. Org.
Chem. 2001, 66, 1914–1918.
[12] C. G. Overberger, C. W. Roberts, J. Am. Chem. Soc. 1949, 71,
3618–3621.
[13] Yield over three steps. Isolation and purification of intermedi-
ate products results in no higher yields. In this study only the
(E)-isomers were isolated and investigated.
[14] S. Zarwell, S. Dietrich, C. Schulz, P. Dietrich, F. Michalik, K.
Rück-Braun, Eur. J. Org. Chem. 2009, 2088–2095.
[15] a) V. D. Bock, H. Hiemstra, J. H. van Maarseveen, Eur. J. Org.
Chem. 2006, 51–68; b) H. C. Kolb, M. G. Finn, K. B.
Sharpless, Angew. Chem. Int. Ed. 2001, 40, 2004–2021; c) V. V.
Rostovtsev, L. G. Green, V. V. Fokin, K. B. Sharpless, Angew.
Chem. Int. Ed. 2002, 41, 2596–2599.
[16] O. Tosic, J. Mattay, Eur. J. Org. Chem. 2011, 371–376.
[17] D. E. Stack, A. L. Hill, C. B. Diffendaffer, N. M. Burns, Org.
Lett. 2002, 4, 4487–4490.
[18] a) J. A. Findlay, P. Mebe, Can. J. Chem. 1980, 58, 1427–1434;
b) A. M. Jawalekar, N. Meeuwenoord, J. G. O. Cremers, H. S.
Overkleeft, G. A. van der Marel, F. P. J. T. Rutjes, F. L.
van Delft, J. Org. Chem. 2008, 73, 287–290.
3
ArH), 7.56 (d, 3JH,H = 8.8 Hz, 1 H, ArH), 7.20 (d, JH,H = 8.7 Hz,
3
1 H, ArH), 6.88 (m, 1 H, ArH), 6.87 (s, 1 H, CH), 6.88 (dd, JH,H
4
4
= 8.9, JH,H = 2.3 Hz, 1 H, ArH), 6.83 (d, JH,H = 2.3 Hz, 1 H,
2
ArH), 5.79 (s, 1 H, CH), 5.66 (s, 2 H, CH2), 5.21 (d, JH,H
=
2
12.3 Hz, 1 H, CH2), 5.18 (d, JH,H = 12.3 Hz, 1 H, CH2) 3.83 (s, 3
H, CH3), 3.62 (s, 3 H, CH3), 2.71 (s, 3 H, CH3), 2.15 (s, 3 H, CH3),
2.14 (s, 3 H, CH3), 0.89 (s, 3 H, CH3) ppm. 13C NMR (126 MHz,
CDCl3): δ = 164.0, 163.8, 163.2, 160.2, 155.6, 153.3, 153.1, 149.4,
148.1, 145.4, 136.2, 132.6, 125.2, 124.6, 123.3, 121.4, 118.5, 116.3,
112.9, 112.0, 111.7, 110.4, 110.1, 104.1, 101.3, 62.9, 55.8, 50.2, 30.0,
26.2, 23.4, 22.6, 12.2 ppm. MS (ESI): m/z = 617 [M – H + Na+].
HRMS (ESI): calcd. for C33H31N4O7+ 595.21873; found 595.21843;
calcd. for C33H30N4O7Na+ 617.20067; found 617.20040.
[19] R. Gujadhur, D. Venkataraman, J. Kintigh, Tetrahedron Lett.
2001, 42, 4791–4793.
[20] a) T. Förster, Ann. Phys. 1948, 437, 55–75; b) T. Förster, Dis-
cuss. Faraday Soc. 1959, 27, 7–17.
Supporting Information (see footnote on the first page of this arti-
cle): UV/Vis and emission spectra of conjugates 42/43 and 48/49.
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Received: February 20, 2011
Acknowledgments
This work was supported by the Biophotonics Initiative of the Ger-
man Ministry of Research and Education (BMBF) (grants
13N9234).
Published Online: June 29, 2011
Eur. J. Org. Chem. 2011, 4645–4653
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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