Synthesis of photochromic benzopyrans annulated by 15(18)-crown-5(6) ether

Article abstract of DOI:10.1007/s11172-008-0339-6

The reaction of hydroxy-substituted benzo-15(18)-crown-5(6) ether or benzo-18-crown-6 ether with β-phenylcinnamaldehyde in the presence of titanium tetraethoxide yielded crown-annulated 2,2-diphenylbenzopyrans. The compounds are photochromic, and the spectral characteristics of their colored form are unusual for this class of chromenes.

Full text of DOI:10.1007/s11172-008-0339-6

Russian Chemical Bulletin, International Edition, Vol. 57, No. 11, pp. 2381—2384, November, 2008
2381
Synthesis of photochromic benzopyrans
annulated by 15(18)ꢀcrownꢀ5(6) ether
S. V. Paramonov,a O. A. Fedorova,a V. P. Perevalov,a V. Lokshin,b and V. Khodorkovskyb
a D. I. Mendeleev University of Chemistry and Technology of Russia,
9 Miusskaya pl., 125047 Moscow, Russian Federation.
Fax: +7 (495) 609 2964. Eꢀmail: fedorova@ineos.ac.ru
b Centre Interdisciplinaire de Nanoscience de Marseille (CINaM,CNRS),
163 Av. de Luminy,13288 Marseille, France.
Fax: +33 (0)4 91 41 89 16
The reaction of hydroxyꢀsubstituted benzoꢀ15(18)ꢀcrownꢀ5(6) ether or benzoꢀ18ꢀcrownꢀ6
ether with βꢀphenylcinnamaldehyde in the presence of titanium tetraethoxide yielded crownꢀ
annulated 2,2ꢀdiphenylbenzopyrans. The compounds are photochromic, and the spectral charꢀ
acteristics of their colored form are unusual for this class of chromenes.
Key words: photochromism, crown ether, chromene, UVꢀVis absorption spectra, bleaching
kinetics.
Photochromic substances are promising for use in
Ionophoric part
modern technologies when producing devices for inforꢀ
mation recording and molecular electronics.1—6 Modifiꢀ
cation of photochromic systems by ionophoric fragments
substantially extends possibilities of practical use of these
compounds.7—13 Several crownꢀcontaining naphthopyrans
are known to the present time.14—18 Naphthopyrans linked
with the crown fragment through the methylene spacer14—16
and naphthopyran in which azacrown ether is a substituꢀ
ent in one of the phenyl rings were synthesized.17,18 These
compounds were demonstrated to be of interest for both
fundamental research and practical purposes when proꢀ
ducing photochromic polymer materials and in photoꢀ
controlled extraction of metal salts from the aqueous to
organic phase.
Photochromic part
n = 1 (1a), 2 (1b).
Published data on synthesis of photochromic benzoꢀ
or naphthopyrans annulated by the crown ether fragment
are lacking to data. Meanwhile, we believe that the annuꢀ
lation of the photochromic and ionophoric fragments
could provide more considerable mutual influence of two
processes that occur in the molecule: complex formation
and photoinduced transformation. In the present study
we describe the synthesis of benzopyrans 1a,b annulated
by the 15ꢀcrownꢀ5 or 18ꢀcrownꢀ6 fragment as well as a
model compound 2 containing no crown ether fragment.
The key stage of this method is the reaction affording
chromenes 1a,b and 2 from the precursors, viz., crownꢀconꢀ
taining phenols 3a,b and 2,3ꢀdimethoxyphenol 4, respectively.
Crownꢀcontaining phenols 3a,b were obtained by the
fiveꢀstage synthesis using a number of earlier described
procedures (Scheme 1).19,20
Our first attempts to obtain compounds 1a,b and 2 by
the traditional method, namely, the reaction of the correꢀ
sponding phenol with diphenylpropargyl alcohol in the
presence of an acid catalyst,6 gave unsatisfactory results.
It is most likely that this method is not quite compatible
with the presence of electronꢀreleasing substituents in the
phenol molecule. An additional problem is the earlier
observed21 noticeable destruction of the crown ether fragꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2333—2336, November, 2008.
1066ꢀ5285/08/5711ꢀ2381 © 2008 Springer Science+Business Media, Inc.

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Paramonov et al.
Scheme 1
PhCH2Cl
n = 1 (a), 2 (b).
Reagents and conditions: i, benzene, Amberlist; ii, NaOH, dioxane, 100 °C; iii, n = 1, NaOH—H2O, toluene, Bu4NI or n = 2, CH3CN, CsF.
ment under the indicated conditions, Therefore, to
obtain compounds 1a,b and 2, we used the method of
synthesis of chromene based on the reaction of phenol
and βꢀphenylcinnamaldehyde in the presence of titanium
tetraethoxide (Scheme 2).22 The structures of synthesized
benzopyrans 1a,b and 2 were confirmed by a combination
of physicochemical analytical methods (see Experimental).
tion band in the visible region. This reaction is reversible,
and the backward cyclization occurs predominantly unꢀ
der the thermal action, but also can occur upon irradiꢀ
ation with the visible light.
Scheme 3
Scheme 2
R = Me (2, 4); R—R =
(1a, 3a),
(7b, 1b).
The irradiation of toluene solutions of benzopyrans
1a,b and 2 (C ≈ 10–4 mol L–1, T = 20 °C) with the light at
λ = 315 nm results in the appearance in an absorption
band in the visible spectral region. The band includes an
intense maximum at 400 nm and a lowꢀintensity broad
band in the region of 450—650 nm (Fig. 1). Similar
character of spectra is characteristic of photochromic
diphenylbenzopyrans.6,23,24 However, such a weak intenꢀ
sity of the longꢀwavelength band compared to the shortꢀ
wavelength maximum is unusual. Since this spectral feaꢀ
ture is observed for all synthesized compounds, we may
i, Ti(OEt)4, toluene, 100 °C.
Synthesized benzochromenes 1a,b and 2 are colorless
compounds, which solutions transform upon UV irradiaꢀ
tion into colored forms. The photochromic properties of
compounds of the considered type are due to the reversꢀ
ible transformation presented in Scheme 3. The irradiꢀ
ation results in the C—O bond cleavage, formation of the
merocyanine cisꢀisomer, and its fast transformation into
the stable transꢀform, which exhibits an intense absorpꢀ

Photochromic crownꢀannulated benzopyrans
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 11, November, 2008 2383
A
were measured with an accuracy to 0.01 ppm, and spinꢀspin
coupling constant values were determined with an accuracy to
0.1 Hz. Electronic absorption spectra were measured on a Varian
Cary 50 spectrophotometer. TCL monitoring was carried out on
the plates 25 DCꢀAlufolien Kieselgel 60 F254. Melting points
were determined in capillaries and used uncorrected. Column
chromatography was performed using Silica gel 60 (Fluka).
Reagents and solvents from Fluka, Merck, and Aldrich were
used. No additional purification of the starting compounds and
solvents was performed.
0.4
1
0.2
2ꢀEthoxyꢀ4ꢀhydroxyꢀ1,3ꢀbenzodioxol (6),19 4ꢀbenzyloxyꢀ
2ꢀethoxyꢀ1,3ꢀbenzodioxol (7),19 14ꢀphenylmethoxyꢀ1,4,7,10,13ꢀ
pentaoxabenzocyclopentadecyne (8a),27 17ꢀphenylmethoxyꢀ
1,4,7,10,13,16ꢀhexaoxabenzocyclooctadecyne (8b),20 14ꢀhydroxyꢀ
2,3,5,6,8,9,11,12ꢀoctahydroꢀ1,4,7,10,13ꢀpentaoxabenzocycloꢀ
pentadecyne (3a),20 and 17ꢀhydroxyꢀ2,3,5,6,8,9,11,12,14,15ꢀ
decahydroꢀ1,4,7,10,13,16ꢀhexaoxabenzocyclooctadecyne (3b)20
2
0.0
400
600
λ/nm
were synthesized according to earlier described procedures.
18,18ꢀDiphenylꢀ2,3,5,6,8,9,11,12ꢀoctahydroꢀ18Hꢀchromenoꢀ
[7,8ꢀb][1,4,7,10,13]pentaoxacyclopentadecyne (1a). A toluene
solution (2 mL) of titanium tetraethoxide (6 mmol) was added to
a solution of substituted phenol 3a (1.14 g, 4 mmol) and βꢀphenylꢀ
cinnamaldehyde (0.84 g, 4 mmol) in toluene (8 mL). The mixture
was stirred at 100 °C under argon for 6 h. Then the mixture was
cooled to 30—40 °C, and toluene (10 mL), silica gel (0.5 g), and
water (1 mL) were added. The mixture was stirred for 30 min at
80 °C. Then the organic layer was dried, and the solvent was
evaporated. The residue was chromatographed on a column
packed with silica gel using ethyl acetate as eluent. After
treatment with pentane, a yellowish powder of compound 1a
was obtained in a yield of 0.56 g (30%). 1H NMR (CDCl3), δ:
3.70—3.79 (m, 8 H, 4 CH2); 3.83—3.94 (m, 4 H, 2 CH2);
4.04—4.20 (m, 4 H, 2 CH2); 6.08 (d, 1 H, H(17), J = 9.8 Hz);
6.36 (d, 1 H, H(15), J = 8.4 Hz); 6.55 (d, 1 H, H(16), J = 9.8 Hz);
6.67 (d, 1 H, H(14), J = 8.4 Hz); 7.17—7.35 (m, 6 H, 4,5ꢀC6H5);
7.41—7.50 (m, 4 H, 2,6ꢀC6H5). 13C NMR (CDCl3), δ: 68.05,
69.31, 69.93, 70.15, 70.45, 70.50, 70.90, 73.12, 82.49, 105.06,
116.12, 120.93, 123.27, 126.72, 126.78, 127.29, 128.02, 136.82,
144.76, 146.16, 153.31. Found (%): C, 73.82; H, 6.59. C29H30O6.
Calculated (%): C, 73.40; H, 6.37.
Fig. 1. Absorption spectrum of the open form of chromene 1b in
toluene before (1) and after irradiation (2) with the monoꢀ
chromatized light with λ = 315 nm, C = 10–4 M, 20 °C.
conclude that this is an exclusively electronic effect
related to the specific position of the electronꢀreleasing
oxygenꢀcontaining substituents.
It seemed interesting to check a possibility to predict
similar spectral behavior by quantum chemical calꢀ
culations. It turned out that the calculation at the TD
B3LYP/6ꢀ31 G(d,p)//HF/6ꢀ31 G(d)25 level predicts
rather reliably both the positions and intensities of the
both longꢀwavelength electronic transitions. According
to the calculation, the weak longꢀwavelength band is
the superposition of electronic transitions (mainly
HOMO → LUMO and HOMO–1 → LUMO) and
the strong band at 400 nm is the electronic transition
HOMO–2 → LUMO.
Thermal bleaching of the colored form was also
studied. It was shown in a few quantitative benzopyrans
studies that this process obeys, as a rule, a biexponential
law with the rate constant of the slow step about 10–3–10–
4 s–1 (see Refs 23 and 26). Our measurements showed that
in toluene for compounds 1b and 2 thermal bleaching is a
monoexponential process with the rate constants k =
5.6•10–3 s–1 and 8.3•10–3 s–1, respectively, at 20 °C. No
other processes were observed under our experimental
conditions.
2,3,5,6,8,9,11,12,14,15ꢀDecahydroꢀ21,21ꢀdiphenylꢀ21Hꢀ
cromeno[7,8ꢀb][1,4,7,10,13,16]hexaoxacyclooctadecyne (1b).
The starting substituted phenol 3b (0.30 g, 0.91 mmol) and
βꢀphenylcinnamaldehyde (0.31 g, 1.37 mmol) were dissolved in
toluene (8 mL). A toluene solution (2 mL) of titanium tetraethoxide
(1.5 mmol) was added to the resulting solution. The mixture
was stirred at 100 °C under argon for 6 h. Then the mixture was
cooled to 30—40 °C, and toluene (10 mL), silica gel (0.5 g), and
water (1 mL) were added. The mixture was stirred for 30 min at
80 °C. Then the organic layer was dried, and the solvent was
evaporated. The residue was chromatographed on a column
packed with silica gel using ethyl acetate as eluent. After
treatment with pentane, compound 1b was obtained in a yield of
0.14 g (30%) as a white crystalline powder with m.p. 83—84 °C
Thus, the sixꢀstep method for synthesis of benzopyrans
annulated by 15ꢀcrownꢀ5 or 18ꢀcrownꢀ6 ethers to posiꢀ
tions 7 and 8 was proposed. These compounds are the first
representatives of photochromic benzopyrans annulated
by the ionophoric fragment.
1
(pentane). H NMR (CDCl3), δ: 3.69 (s, 4 H, 2 CH2); 3.71 (s,
4 H, 2 CH2); 3.76 (s, 4 H, 2 CH2); (t, 2 H, CH2, J = 5.3 Hz);
3.92—3.98 (m, 2 H, CH2); 4.09—4.16 (m, 4 H, 2 CH2); 6.07 (d,
1 H, H(20), J = 9.8 Hz); 6.39 (d, 1 H, H(18), J = 8.4 Hz); 6.56
(d, 1 H, H(19), J = 9.8 Hz); 6.68 (d, 1 H, H(17), J = 8.4 Hz);
7.20—7.35 (m, 6 H, 4,5ꢀC6H5); 7.42—7.49 (m, 4 H, 2,6ꢀC6H5).
13C NMR (CDCl3), δ: 68.53, 69.69, 70.34, 70.46, 70.64, 70.78,
Experimental
1H and 13C NMR spectra were recorded on a Bruker DRXꢀ
250 spectrometer (working frequency 250 MHz) using CDCl3
(1H and 13C) and DMSOꢀd6 (1H) as solvents. Chemical shifts

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Paramonov et al.
71.04, 71.15, 72.53 (all t); 82.51 (s), 105.66 (d), 116.28 (s);
121.06, 123.27, 126.82, 127.32, 128.04 (all d); 136.71, 144.79,
146.16, 153.24 (all s). Found (%): C, 71.96; H, 6.82. C31H34O7.
Calculated (%): C, 71.80; H, 6.61.
16. O. A. Fedorova, Yu. P. Strokach, A. V. Chebun´kova, T. M.
Valova, S. P. Gromov, M. V. Alfimov, V. Lokshin, A. Sama,
Izv. Akad. Nuak, Ser. Khim., 2006, 280 [Russ. Chem. Bull.,
Int. Ed., 2006, 55, 287].
7,8ꢀDimethoxyꢀ2,2ꢀdiphenylꢀ2Hꢀchromene (2) was obtained
similarly to chromene 1 from dimethoxyphenol 4 and βꢀphenylꢀ
cinnamaldehyde in 23% yield, m.p. 105—106 °C (heptane).
1H NMR (CDCl3), δ: 3.81 (s, 3 H, OCH3); 3.82 (s, 3 H, OCH3);
6.06 (d, 1 H, H(3), J = 9.8 Hz); 6.41 (d, 1 H, H(6), J = 8.4 Hz);
6.58 (d, 1 H, H(4), J = 9.8 Hz); 6.71 (d, 1 H, H(5), J = 8.4 Hz);
7.19—7.37 (m, 6 H, HAr); 7.41—7.53 (m, 4 H, HAr). 13C NMR
(CDCl3), δ: 56.18, 61.43, 82.88 (C(2)), 104.51, 116.43, 121.21,
123.50, 127.05, 127.17, 127.61, 128.28, 137.64, 144.90, 146.19,
154.04. Found (%): C, 80.16; H, 5.81. C23H20O3. Calculꢀ
ated (%): C, 80.21; H, 5.85.
17. E. N. Ushakov, V. B. Nazarov, O. A. Fedorova, S. P. Gromov,
A. V. Chebunґkova, M. V. Alfimov, F. Barigelletti, J. Phys.
Org. Chem., 2003, 16, 306.
18. O. A. Fedorova, F. Maurel, E. N. Ushakov, V. B. Nazarov,
S. P. Gromov, A. V. Chebunkova, A. V. Feofanov, I. S.
Alaverdian, M. V. Alfimov, F. Barigelletti, New J. Chem.,
2003, 27, 1730.
19. F. Dietl, G. Gierer, A. Merz, Synthesis, 1985, 626.
20. K. Hayakawa, K. Kido, K. Kanematsu, J. Chem. Soc., Perkin
Trans. 1, 1988, 511.
21. A. V. Chebun´kova, Ph. D. (Chem) Author´s Abstract, 2006,
Moscow, 25 pp. (in Russian).
This work was financially supported by the Russian
Academy of Sciences (Program on Supramolecular
Chemistry) and the PHENICS International Laboratory.
22. J.ꢀL. Pozzo, V. Lokshin, R. Guglielmetti, J. Chem. Soc.,
Perkin Trans. 1, 1994, 2591.
23. J. N. Moorthy, P. Venkatakrishnan, S. Samanta, D. K.
Kumar, Org. Lett., 2007, 9, 912.
24. J.ꢀL. Pozzo, A. Samat, R. Guglielmetti, V. Lokshin,
V. Minkin, Can. J. Chem., 1996, 74, 1649.
References
25. M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery, Jr., T.
Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S.
Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi,
G. Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji,
M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai,
M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross,
C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann,
O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski,
P. Y. Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J.
Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels,
M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck,
K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G.
Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu,
A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J.
Fox, T. Keith, M. A. AlꢀLaham, C. Y. Peng, A. Nanayakkara,
M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen,
M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian 03, Reviꢀ
sion B.03, Pittsburgh PA: Gaussian Inc., 2003.
1. Ed. G. H. Brown, Photochromism, WileyꢀInterscience, New
York, 1971.
2. Applied Photochromic Polymer Systems, Ed. C. B. McArdle,
Blackie, New York, 1992.
3. Photochromism: Molecules and Systems, Eds H. Durr,
H. BouasꢀLaurent, Elsevier, Amsterdam, 1990.
4. R. S. Becker, J. Michl, J. Am. Chem. Soc., 1966, 88, 5931.
5. J. C. Crano, T. Flood, D. Knowles, A. Kumar, B. van
Gemert, Pure Appl. Chem., 1996, 68, 1395.
6. J. C. Crano, R. J. Guglielmetti, Organic photochromic and
thermochromic compounds, Kluwer Academic/Plenum
Publishers, New York, 1999.
7. M. Inouye, M. Ueno, K. Tsuchia, N. Nakayama, T. Konishi,
T. Kitao, J. Org. Chem., 1992, 57, 5377.
8. K. Kimura, T. Yamashita, M. Yokoyama, J. Chem. Soc.,
Perkin Trans. 2, 1992, 613.
9. M. Tanaka, K. Kamada, H. Ando, T. Kitagaki, Ya. Shibuyani,
K. Kimura, J. Org. Chem., 2000, 6, 4342.
10. M. Nakamura, T. Fujioka, H. Sakamoto, K. Kimura, New J.
Chem., 2002, 26, 554.
26. P. Hannesschlager, P. Brun, Appl. Organometal. Chem., 2000,
14, 686.
27. T. Bogaschenko, S. Basok, C. Kulygina, A. Lyapunov,
N. Lukyanenko, Synthesis, 2002, 2266.
11. O. A. Fedorova, S. P. Gromov, M. V. Alfimov, Izv. Akad.
Nauk, Ser. Khim., 2001, 1882 [Russ. Chem. Bull., Int. Ed.,
2001, 51, 1970].
12. K. Kimura, H. Sakamoto, M. Nakamura, Bull. Chem. Soc.
Jpn, 2003, 76, 225.
13. M. A. Alfimov, O. A. Fedorova, S. P. Gromov, J. Photochem.
Photobiol. A: Chem., 2003, 158, 183.
14. S. A. Ahmed, M. Tanaka, H. Iwamoto, K. Kimura,
Tetrahedron, 2004, 60, 3211.
15. S. A. Ahmed, M. Tanaka, H. Iwamoto, K. Kimura, Eur. J.
Org. Chem., 2003, 2437.
Received April 30, 2008;
in revised form June 30, 2008