Synthesis and photochromism of novel chromene derivatives bearing a monoazacrown ether moiety

Article abstract of DOI:10.1002/ejoc.200300070

Crowned chromenes - four novel naphthopyrans (chromenes) bearing monoaza-12-crown-4, -15-crown-5, -18-crown-6, and a noncyclic analogue at the 5-position-were synthesized, and their photochromism in acetonitrile was examined in the presence of alkali and alkaline-earth metal ions. Incorporation of crown ether units to chromene moieties facilitated to a great extent both the thermal isomerization and photoisomerization of the chromene moiety, reflecting the metal-ion-binding ability of the crown ether moiety. Comparison of the crowned chromenes with the corresponding crowned spirobenzopyrans reveals that photochromism of the crowned chromene reflects an interaction between the metal ion and the crown ether moiety that is stronger than that of the crowned spirobenzopyran, and shows only positive photochromism with significant red-shifts in the UV/Vis absorption spectra, in contrast to the crowned spirobenzopyrans reported previously. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).

Full text of DOI:10.1002/ejoc.200300070

FULL PAPER
Synthesis and Photochromism of Novel Chromene Derivatives Bearing a
Monoazacrown Ether Moiety
[a]
[a]
[a]
[c]
Saleh A. Ahmed, Mutsuo Tanaka,* Hisanori Ando, Hitoshi Iwamoto, and
Keiichi Kimura*[
c]
Keywords: Crown compounds / HostϪguest systems / Photochromism
Crowned chromenes
−
four novel naphthopyrans
responding crowned spirobenzopyrans reveals that photo-
chromism of the crowned chromene reflects an interaction
between the metal ion and the crown ether moiety that is
stronger than that of the crowned spirobenzopyran, and
shows only positive photochromism with significant red-
shifts in the UV/Vis absorption spectra, in contrast to the
crowned spirobenzopyrans reported previously.
(chromenes) bearing monoaza-12-crown-4, -15-crown-5,
-18-crown-6, and a noncyclic analogue at the 5-position −
were synthesized, and their photochromism in acetonitrile
was examined in the presence of alkali and alkaline-earth
metal ions. Incorporation of crown ether units to chromene
moieties facilitated to a great extent both the thermal iso-
merization and photoisomerization of the chromene moiety,
reflecting the metal-ion-binding ability of the crown ether
moiety. Comparison of the crowned chromenes with the cor-
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
Introduction
known photochromic materials. Since the discovery of
photochromic behavior of the chromene by Becker and co-
[
3]
workers, extensive studies have been devoted to chro-
menes because of their excellent resistance to photodegrad-
ation, which is similar to that of spirooxazines. The pho-
tochromic behavior of chromene is based on reversible py-
ran ring opening, in which its colorless closed form is con-
verted by UV irradiation into a set of corresponding
colored open forms that return thermally to the closed form
Photochromism is a reversible photoinduced phenom-
enon in which a photosensitive substrate is transformed
into another isomer exhibiting a different absorption spec-
trum in the visible region. In the last few decades, the inves-
tigation of photochromic molecules[1] has became an im-
portant field because of a large number of potential appli-
cations, such as optical variable-transmission materials, op-
[
4]
tical switches, and memories,[
2]
(Scheme 1). Because of the quasi planarity of the open
form, extended π-electron conjugation is achieved and a
distinct absorption, typically in the visible region, is ob-
served. A noteworthy difference among the pyran com-
based on their
photoreversibility. The investigated characteristics that have
been studied are: (1) coloration by sunlight (heliochromism)
and thermal decoloration, (2) absorption in the visible re-
gion upon irradiation, (3) rate of decoloration, (4) color-
ation efficiency upon irradiation (colorability), and (5) re-
sistance to photodegradation (photofatigue resistance).
Pyran compounds such as benzo- and naphthopyrans
[
5]
[6]
pounds is that chromenes and spirooxazines take a qui-
[
7]
noidal open form, but spiropyran prefers the zwitterionic
open form.
(chromenes), spiropyrans, and spirooxazines are well-
[
a]
Special Division for Human Life Technology, AIST
Kansai, 1-8-31, Midorigaoka, Ikeda, Osaka 563-8577, Japan
Fax: (internat.) ϩ 81-72/751-9629
E-mail: mutsuo-tanaka@aist.go.jp
[
[
b]
JSPS Fellow: Permanent Address; Chemistry Department,
Faculty of Science, Assiut University,
Scheme 1. Photoisomerization of chromene
7
1516, Assiut, Egypt
c]
Department of Applied Chemistry, Faculty of Systems
Engineering, Wakayama University,
On the other hand, incorporating the features of both
photochromic and metal ion recognition molecules has
been reported to afford bifunctional molecules in which the
photochromic moiety controls the metal-ion-binding be-
havior or the metal ion recognition moiety dominates the
9
30, Sakae-dani, Wakayama, Wakayama 640-8510, Japan
Fax: (internat.) ϩ 81-73/457-8255
E-mail: kkimura@mail.sys.wakayama-u.ac.jp
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
Eur. J. Org. Chem. 2003, 2437Ϫ2442
DOI: 10.1002/ejoc.200300070
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2437

S. A. Ahmed, M. Tanaka, H. Ando, H. Iwamoto, K. Kimura
FULL PAPER
photochromism. The incorporation of crown ether units crowned chromenes 1؊3 and the analogue 4 were obtained
[
8]
[9]
into azobenzene and diarylethene shows the former in moderate to good yields (42Ϫ79%).
[10]
tendency, and incorporation into spirooxazine and spiro-
Photochromism of Crowned Chromenes: UV/Vis absorp-
[
11,12]
benzopyran
indicates the latter behavior. To the best tion spectra of the crowned chromenes 1؊3 and the ana-
Ϫ4
Ϫ3
of our knowledge, however, there has been only one report logue 4 were measured in acetonitrile (1 ϫ 10 mol·dm
)
on chromene derivatives bearing a crown ether moiety. In in the presence of a metal perchlorate (1 ϫ 10 mol·dmϪ3)
[
13]
Ϫ4
a continuation of our previous work dealing with crowned before and after UV irradiation (365 nm, 3 min) at room
[
14,15]
[16]
[18]
spirobenzopryran
and spirooxazine, in this paper we temperature.
As shown in Figure 1, the spectra of 1 are
report chromene derivatives bearing a monoazacrown ether hardly changed by addition of the equimolar amount of
moiety, namely crowned chromenes.
an alkali metal ion. This observation means that thermal
isomerization to the quinoidal form does not proceed, in
contrast to the situation found for the corresponding
crowned spirobenzopyran, the pyran ring of which is
Results and Discussion
[
19]
opened readily without UV irradiation.
Upon UV ir-
ϩ
Synthesis: The synthesis of crowned chromenes 1؊3 and radiation, the Li solution shows the most significant
their analogue 4 was carried out according to the synthetic spectral change with a remarkable red-shift, and the Na
ϩ
route outlined in Scheme 2. 5-Bromomethylchromene was solution indicats a slight spectral change. The facilitated
ϩ
prepared according to a method similar to that found in photoisomerization with Li is clearly derived from the me-
[
17]
the literature.
The reaction of 5-bromomethylchromene tal-ion binding ability of the 12-crown-4 moiety. In the case
with monoazacrown ethers was undertaken in the presence of alkaline-earth metal ions, Ca2 induces a considerable
of triethylamine in dry THF under reflux for 6 h under ni- thermal isomerization. On the other hand, the facilitated
trogen. For comparison with the crowned chromenes, the photoisomerization was observed for all solutions with sig-
noncyclic analogue 4 was prepared in a similar fashion. In nificant red-shifts (Figure 2).
ϩ
all cases, the products were isolated by GPC (gel per-
For the crowned chromene 2, a slight thermal isomeriz-
ϩ
meation chromatography) in their protonated forms. De- ation is observed in the presence of Li (Figure 3), re-
ϩ
protonation of the products was carried out by washing flecting the strong interaction between Li and 2. Upon
ϩ
ϩ
with aqueous potassium carbonate solution, and the UV irradiation, both Li and Na induce drastic changes
in the absorption spectra. This enhancement of photoiso-
Figure 1. Absorption spectra of 1 in acetonitrile in the presence of
alkali-metal ions
Figure 2. Absorption spectra of 1 in the presence of alkaline-earth
Scheme 2. Synthetic approach
438
metal ions in acetonitrile
2
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 2437Ϫ2442

Synthesis and Photochromism of Novel Chromene Derivatives
FULL PAPER
ϩ
ϩ
merization by Na for 2, compared with that for 1, may be change. Furthermore, K facilitated the photoisomeriz-
attributed to the ring-size enlargement of the crown ether ation considerably. With alkaline-earth metal ions (Fig-
moiety. In the presence of alkaline-earth metal ions, the ure 6), the observed tendency is similar to that for 1 (Fig-
thermal isomerization of 2 is more significant than that of ure 2), where Ca2 induces the most significant thermal iso-
ϩ
1
, as shown in Figure 4. Of the alkaline-earth metal ions, merization and photoisomerization.
2
ϩ
Mg induces the most significant thermal isomerization
and the photoisomerization having the most notable red-
shift.
Figure 6. Absorption spectra of 3 in the presence of alkaline-earth
metal ions
On the other hand, the non-cyclic analogue 4 did not
show any significant thermal isomerization in the presence
of any metal ions, as was anticipated from its metal-ion-
complexing ability. Similarly, the facilitated photoisomeriz-
ation was hardly observed in any case, and only Ca2
induced a slight facilitated photoisomerization (Figure 7
and 8).
Figure 3. Absorption spectra of 2 in the presence of alkali-metal
ions
ϩ
Figure 4. Absorption spectra of 2 in the presence of alkaline-earth
metal ions
In the case of 3, no significant thermal isomerization was
observed in the presence of alkali metal ions, an obser-
vation similar to that of 1 (Figure 5). UV irradiation in-
ϩ
duced the most drastic spectral change for the Na solu- Figure 7. Absorption spectra of 4 in the presence of alkali-metal
ϩ
ions
tion, and the Li solution also showed a significant spectral
Figure 5. Absorption spectra of 3 in the presence of alkali-metal
ions
Figure 8. Absorption spectra of 4 in the presence of alkaline-earth
metal ions
Eur. J. Org. Chem. 2003, 2437Ϫ2442
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2439

S. A. Ahmed, M. Tanaka, H. Ando, H. Iwamoto, K. Kimura
FULL PAPER
reflects that the metal-ion-binding ability of their crown
ether moieties is stronger than that in the crowned spirob-
enzopyran, since the interaction of the metal ion with the
carbonyl group in the crowned chromene is weaker than
that with the phenolate anion moiety in the crowned spirob-
enzopyran.
For the crowned chromenes, the wavelengths at the maxi-
mum absorption point for the solutions undergoing facili-
tated photoisomerizations show significant red-shifts,
whereas blue-shifts appeared for the crowned spirobenzopy-
ran. It has been reported that both red- and blue-shifts can
Scheme 3. Interaction of the metal ion with the carbonyl group
and the crown ether unit of the trans form.
[
20]
be induced by solvation, and the quinoidal form of chro-
As depicted in Scheme 3,[4] dual interactions of the metal mene shows a slight red-shift in polar solvents. The most
ion with the crown ether moiety and the carbonyl group are significant red-shift (104 nm), when compared with the
possible in the quinoidal form of the crowned chromene in solution absent the metal ion, was observed for the Mg2
[21]
ϩ
2
ϩ
a similar manner to that in the merocyanine form of the solution of 2, indicating a strong interaction between Mg
crowned spirobenzopyran.[ The alkali metal ion that in- and the quinoidal form. A H NMR spectrum of a solution
duced the greatest facilitated photoisomerization changed of 2 (1 ϫ 10 mol·dm ) in the presence of an excess of
15]
1
Ϫ2
Ϫ3
ϩ
ϩ
2ϩ
Ϫ1
Ϫ3
from Li to Na when the size of the crown ether moiety Mg
ions (1 ϫ 10
mol·dm ) showed a significant
was increased from 12- to 18-membered rings. In the case of downfield shift (ca. 0.4 ppm) for the protons of the crown
ϩ
the corresponding crowned spirobenzopyrans, Li always ether moiety resulting from the formation of a complex
ϩ
induced the most remarkable thermal isomerization, re- with Mg2 . In the previous study on photochromism of
gardless of the ring size of the crown ether moiety, which the crowned spirobenzopyran, negative photochromism was
ϩ
reflects the strong ionic interaction of Li with the phenol- induced when a strong interaction was observed between
[
15]
ate anion moiety in the merocyanine form of the crowned the metal ion and the crowned spirobenzopiran.
An at-
[
19]
spirobenzopyran.
4
Furthermore, the non-cyclic analogue tempt, however, to induce negative photochromism for 2 (1
Ϫ4
Ϫ3
did not show a thermal isomerization, whereas significant ϫ 10 mol·dm ) in the presence of a high concentration
ϩ
thermal isomerization appeared for the corresponding spi- of Mg2 (5 ϫ 10 mol·dm ) was not successful, again
Ϫ3
Ϫ3
ϩ
robenzopyran in the presence of Li . Therefore, this ring- showing different behavior than that of the crowned spirob-
size dependency in the crown ether moiety implies that the enzopyran.
interaction of metal ions with the crown ether moiety,
Stabilization Effect of Metal Ions on the Quinoidal Form:
rather than with the carbonyl group, is predominant in de- To evaluate the stabilization effect of metal ions on the qui-
termining the tendency for photochromism in crowned noidal form of the crowned chromenes, we determined rate
2
ϩ
chromenes. Among alkaline-earth metal ions, Ca showed constants for thermal decoloration in a similar fashion as
[
18]
the most significant influence on both the thermal isomeriz- that reported earlier.
Unfortunately, the crowned chro-
ation and photoisomerization of 1, 3, and 4, while Mg2
ϩ
menes 1؊3, as well as the non-cyclic analogue 4, showed
was the most effective for 2. A similar independence of the poor resistance to photodegradation in the absence of metal
ring size in the crown ether moiety also was observed for ions, which hampered determination of the rate constants.
the crowned spirobenzopyrans. The charge density of alka- Similarly, the serious photodegradation resulted in a failure
line-earth metal ions is much higher than that of alkali me- to determine reliable rate constants when no significant fa-
tal ions and, therefore, the effect of alkaline-earth metal cilitated photoisomerization was observed, even in the pres-
ions on the isomerization may be stronger than that of alk- ence of metal ions. In contrast, reliable rate constants were
ali-metal ions through stronger interactions between the obtained for the solutions that showed notable facilitated
metal ion and the carbonyl group, a situation similar to photoisomerization, namely, those with a strong interaction
that observed for the phenolate anion moiety of crowned between the metal ions and the quinoidal form. This tend-
[
15]
spirobenzopyrans.
A comparison of crowned chromenes ency implies that the strong interaction of metal ions with
with the corresponding crowned spirobenzopyrans suggests the crowned chromene enhances the resistance to photodeg-
that the enhanced photochromism of crowned chromenes radation as well as the facilitated photoisomerization. The
Table 1. Decoloration rate constants (10Ϫ2 sϪ1
)
Without metal ion[a]
Li
ϩ
Na
ϩ
K
ϩ
Rb
ϩ
Cs
ϩ
Mg2ϩ
Ca2ϩ
Sr2ϩ
Ba2ϩ
1
2
3
4
n.d.
n.d.
n.d.
n.d.
4.5
0.063
1.8
n.d.
1.6
1.7
n.d.
n.d.
4.9
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
0.0069
n.d.
0.097
0.019
0.0075
n.d.
0.40
0.45
0.11
0.23
n.d.
0.063
0.038
n.d.
n.d.
n.d.
n.d.
n.d.
[
a]
n.d.: Reliable constant was not determined.
440
2
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 2437Ϫ2442

Synthesis and Photochromism of Novel Chromene Derivatives
FULL PAPER
smaller rate constants for decoloration mean that there are ganic phase was dried overnight on anhydrous sodium sulfate. The
solids were filtered off and the product was obtained by evapor-
ation of the solvent.
greater stabilization effects on the quinoidal form of the
crowned chromenes. The rate constants are summarized in
Table 1.
Among alkali-metal ions, distinct stabilization effects ried out according to the general procedure described above, and
Monoaza-12-crown-4-chromene (1): The preparation of 1 was car-
ϩ
ϩ
ϩ
ϩ
were observed with Li for 1, Li and Na for 2, and Li , the product (0.211 mmol, 110 mg, 42%, C H NO , MW 521.65)
3
4
35
1
4
ϩ
ϩ
3
Na and K for 3. This tendency clearly reflects the metal- was obtained as a viscous, yellow-brown oil: H NMR (CDCl ,
400 MHz, 25 °C): δ ϭ 2.83 (t, J ϭ 4.6 Hz, 4 H, NCH
2
), 3.6Ϫ3.8
ion-binding ability of the crown ether moiety depends on
the ring size. Pronounced stabilization effects were observed
when the crowned chromenes interacted with alkaline-earth
metal ions. Specifically, Ca showed a strong stabilization
effect for all the crowned chromenes. The trends in the rate
constants for decoloration are consistent with those in the
UV/Vis absorption spectra.
(
m, 12 H, OCH ), 3.94 (s, 2 H, PhCH ), 6.20 (d, J ϭ 9.6 Hz, 1 H,
2
2
CHϭ), 7.2Ϫ7.5 (m, 13 H, ArH, CHϭ), 7.72 (d, J ϭ 8.0 Hz, 1 H,
ArH), 7.93 (d, J ϭ 8.0 Hz, 1 H, ArH), 8.02 (s, 1 H, ArH) ppm. IR
2
ϩ
Ϫ1
(
neat): ν˜ ϭ 2855 (CH
2
), 1110 (OCH
·H
found C 76.07, H 6.58, N 2.47.
2
), 753 (CϭC) cm . MS:
ϩ
m/z ϭ 521 [M ]. C34
H35NO
4
2
O: calcd. C 75.67, H 6.91, N 2.60;
Monoaza-15-crown-5-chromene (2): The preparation of 2 was car-
ried out according to the general procedure described above, and
the product (0.394 mmol, 223 mg, 79%, C36
was obtained as a viscous, yellow-brown oil: H NMR (CDCl ,
3
H
39NO
5
, MW 565.71)
Conclusion
1
4
(
00 MHz, 25 °C): δ ϭ 2.88 (t, J ϭ 6.0 Hz, 4 H, NCH
m, 16 H, OCH ), 3.94 (s, 2 H, PhCH ), 6.20 (d, J ϭ 9.6 Hz, 1 H,
CHϭ), 7.2Ϫ7.6 (m, 13 H, ArH, CHϭ), 7.71 (d, J ϭ 8.0 Hz, 1 H,
2
), 3.6Ϫ3.7
The metal-ion-binding ability of the crown ether moiety
in crowned chromenes drastically influences photochro-
2
2
mism in a similar way to that observed for crowned spirob- ArH), 7.83 (s, 1 H, ArH), 7.91 (d, J ϭ 8.4 Hz, 1 H, ArH) ppm. IR
Ϫ1
enzopyran. A comparison of the crowned chromene with (neat): ν˜ ϭ 2867 (CH
), 1121 (OCH
2
), 753 (CϭC) cm . MS:
2
ϩ
m/z ϭ 565 [M ]. C36
C 76.05, H 7.09, N 2.51.
H39NO : calcd. C 76.43, H 6.95, N 2.48; found
5
the corresponding crowned spirobenzopyran revealed the
following three features: (1) the photochromism of the
crowned chromenes reflects an interaction between the me-
tal ions and the crown ether moieties that is stronger than
Monoaza-18-crown-6-chromene (3): The preparation of 3 was car-
ried out according to the general procedure described above, and
that of the crowned spirobenzopyran because the metal ion the product (0.349 mmol, 213 mg, 70%, C H NO , MW 609.74)
3
8
43
1
6
interacts more weakly with the carbonyl group in the was obtained as a viscous, yellow-brown oil: H NMR (CDCl
crowned chromenes than with the phenolate anion moiety 400 MHz, 25 °C): δ ϭ 2.87 (t, J ϭ 6.0 Hz, 4 H, NCH ), 3.5Ϫ3.8
), 6.21 (d, J ϭ 10 Hz, 1 H,
3
,
2
(
2 2
m, 20 H, OCH ), 3.93 (s, 2 H, PhCH
in the crowned spirobenzopyran; (2) a strong interaction
between the metal ion and the crowned chromene caused a
significant red-shift in the UV/Vis absorption spectrum in
contrast to the blue-shift observed for the crowned spiro-
benzopyran; (3) the crowned chromene did not show the
negative photochromism that was observed with the
crowned spirobenzopyran.
CHϭ), 7.2Ϫ7.5 (m, 13 H, ArH, CHϭ), 7.71 (d, J ϭ 8.4 Hz, 1 H,
ArH), 7.82 (s, 1 H, ArH), 7.92 (d, J ϭ 8.4 Hz, 1 H, ArH) ppm. IR
Ϫ1
(
neat): ν˜ ϭ 2905 (ϪCH
2
Ϫ), 1106 (OCH
·H
found C 72.99, H 7.05, N 2.24.
2
), 755 (CϭC) cm . MS:
ϩ
m/z ϭ 609 [M ]. C38
H43NO
6
2
O: calcd. C 72.70, H 7.22, N 2.23;
3
,9-Dioxa-6-monoazaundecane-chromene (4): Preparation was of 4
carried out according to the general procedure described above,
and the product (0.305 mmol, 155 mg, 61%, C34
H
37NO
3
, MW
1
507.67) was obtained as a viscous, dark-yellow oil: H NMR
Experimental Section
(
2
3
CDCl
3
, 400 MHz, 25 °C): δ ϭ 1.14 (t, J ϭ 7.0 Hz, 6 H, CH
.84 (t, J ϭ 6.2 Hz, 4 H, NCH ), 3.38 (q, J ϭ 7.1 Hz, 4 H, OCH
.51 (t, J ϭ 6.2 Hz, 4 H, OCH ), 3.96 (s, 2 H, PhCH
3
),
),
2
2
General Remarks: All chemicals for synthesis were of available pu-
rity and used without further purification. For spectral measure-
ments, spectroscopic-grade acetonitrile was used as the solvent,
while all metal perchlorates were the highest grade available and
were employed as received. The procedures for the spectral meas-
urement and the determination of the rate constants for decolor-
ation are described in reference [ . 5-Bromomethylchromene and
2
2
), 6.20 (d,
J ϭ 9.6 Hz, 1 H, CHϭ), 7.2Ϫ7.6 (m, 13 H, ArH, CHϭ), 7.70 (d,
J ϭ 8.4 Hz, 1 H, ArH), 7.83 (s, 1 H, ArH), 7.92 (d, J ϭ 8.4 Hz, 1
H, ArH) ppm. IR (neat): ν˜ ϭ 2864 (CH
), 1110 (OCH
·1/2H O: calcd. C 79.04,
H 7.41, N 2.71; found C 79.24, H 7.37, N 2.62.
2
), 749 (Cϭ
2
Ϫ1
ϩ
C) cm . MS: m/z ϭ 507 [M ]. C34
H37NO
3
2
18]
3
,9-dioxa-6-monoazaundecane were prepared according to the
[17]
[18]
methods reported in ref. and ref. , respectively. For the meas- Acknowledgments
urement of NMR spectra, [D ]acetonitrile and magnesium per-
3
We are very much indebted to the Japan Society for Promotion of
Science (JSPS) for the financial support of this work by a Grant-
in-Aid for JSPS fellows. The present work was partially supported
by a Grant-in-Aid-for Scientific Research (B) (no. 15350043)
from the Ministry of Education, Culture, Sports, Science, and
Technology, Japan.
chlorate were used at room temperature.
Synthesis of Chromenes. General Procedure: Under nitrogen,
monoaza-crown ether (0.5 mmol), 5-bromomethylchromene
(214 mg, 0.5 mmol), triethylamine (150 mg, 1.5 mmol), and dry
THF (50 mL) were placed into a three-necked flask, and the reac-
tion mixture was refluxed for 6 h. The product obtained by solvent
evaporation was purified by GPC (gel permeation chromatography)
in its protonated form. The chloroform solution obtained by GPC
was washed with 5-wt% aqueous potassium carbonate, and the or-
[1] [1a]
Organic Photochromic and Thermochromic Compounds,
(Eds.: J. C. Crano, R. J. Guglielmetti), Kluwer Acdamic/Ple-
num, New York and London, 1999, vol. 1 and 2. [ Photochro-
1b]
Eur. J. Org. Chem. 2003, 2437Ϫ2442
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2441

S. A. Ahmed, M. Tanaka, H. Ando, H. Iwamoto, K. Kimura
FULL PAPER
mism - Molecules and System, (Eds.: H. Dürr, H. Bouas-Laur-
ent), Elsevier, Amsterdam, 1990.
Isagawa, Angew. Chem. Int. Ed. Engl. 1994, 33, 1163Ϫ1166.
[12c]
M. Inouye, M. Ueno, T. Kitao, J. Org. Chem. 1992, 57,
[
2] [2a]
[2b]
M. Irie, Chem. Rev. 2000, 100, 1685Ϫ1716.
G. Berkovic,
1639Ϫ1641.
V. Krongauz, Chem. Rev. 2000, 100, 1741Ϫ1754. [ S. Kawata,
2c]
[13]
M. T. Stauffer, D. B. Knowles, C. Brennan, L. Funderburk, F.
Lin, S. G. Weber, Chem. Commun. 1997, 287Ϫ288.
14] [14a]
Y. Kawata, Chem. Rev. 2000, 100, 1777Ϫ1788.
[
[
[
3]
4]
K. Kimura, T. Yamashita, M. Yokoyama, J. Phys. Chem.
R. S. Becker, J. Michl, J. Am. Chem. Soc. 1966, 88, 5931Ϫ5933.
It has been reported that several isomers are possible for the
1992, 96, 5614Ϫ5617. [
14b]
K. Kimura, T. Yamashita, M.
[
14c]
[1a]
Yokoyama, J. Chem. Soc., Perkin Trans. 2 1992, 613Ϫ619.
K. Kimura, S. Kado, H. Sakamoto, A. Sakai, M. Yokoyama,
open form of chromenes. See ref.
ref.
(vol. 1, chapter 3) and
[
5]
[
5]
6]
M. Tanaka, J. Chem. Soc., Perkin Trans. 2 1999, 2538Ϫ2544.
J. Berthet, S. Delbaere, D. Levi, A. Samat, R. Guglielmetti, G.
Vermeersch, Photochem. Photobiol. Sci. 2002, 1, 665Ϫ672.
J. Berthet, S. Delbaere, V. Lokshin, C. Bochu, A. Samat, R.
Guglielmetti, G. Vermeersch, Photochem. Photobiol. Sci. 2002,
[14d]
K. Kimura, T. Teranishi, M. Yokoyama, S. Yajima, S. Mi-
[
yake, H. Sakamoto, M. Tanaka, J. Chem. Soc., Perkin Trans.
1999, 119Ϫ204.
15] [15a]
2
[
M. Tanaka, T. Ikeda, Q. Xu, H. Ando, Y. Shibutani, M.
Nakamura, H. Sakamoto, S. Yajima, K. Kimura, J. Org. Chem.
1
, 333Ϫ339.
M. Inouye, M. Ueno, T. Kitao, K. Tsuchiya, J. Am. Chem. Soc.
990, 112, 8977Ϫ8979.
[
[
7]
[15b]
2
002, 67, 2223Ϫ2227.
M. Tanaka, M. Nakamura, A. M.
1
A. Salhin, T. Ikeda, K. Kamada, H. Ando, Y. Shibutani, K.
8] [8a]
S. Shinkai, T. Nakaji, T. Ogawa, K. Shigematsu, O. Man-
[15c]
Kimura, J. Org. Chem. 2001, 66, 1533Ϫ1537.
Salhin, M. Tanaka, K. Kamada, H. Ando, T. Ikeda, Y. Shibut-
A. M. A.
abe, J. Am. Chem. Soc. 1981, 103, 111Ϫ115. [ S. Shinkai,
T. Ogawa, Y. Kusano, O. Manabe, K. Kikukawa, T. Goto, T.
Matsuda, J. Am. Chem. Soc. 1982, 104, 1960Ϫ1967. [ S. Shin-
8b]
ani, S. Yajima, M. Nakamura, K. Kimura, Eur. J. Org. Chem.
8c]
2002, 655Ϫ662.
kai, T. Minami, Y. Kusano, O. Manabe, J. Am. Chem. Soc.
[16] [16a]
K. Kimura, T. Yamashita, M. Kaneshige, M. Yokoyama,
8d]
1
982, 104, 1967Ϫ1972. [ S. Shinkai, T. Minami, Y. Kusano,
[16b]
J. Chem. Soc., Chem. Commun. 1992, 969Ϫ970.
K. Ki-
[8e]
O. Manabe, J. Am. Chem. Soc. 1983, 105, 1851Ϫ1856.
S.
mura, M. Kaneshige, T. Yamashita, M. Yokoyama, J. Org.
Chem. 1994, 59, 1251Ϫ1256.
[17] [17a]
Shinkai, K. Miyazaki, O. Manabe, J. Chem. Soc., Perkin Trans.
1
Manabe, J. Chem. Soc., Perkin Trans. 1 1982, 2735Ϫ2739.
1987, 449Ϫ456. [ S. Shinkai, K. Shigematsu, M. Sato, O.
8f]
A. Samat, V. Lokshin, K. Chamontin, D. Levi, G. Pepe,
[8g]
[17b]
R. Guglielmetti, Tetrahedron 2001, 57, 7349Ϫ7359.
K.
S. Shinkai, M. Ishihara, K. Ueda, O. Manabe, J. Chem. Soc.,
Perkin Trans. 2 1985, 511Ϫ518. [ W. Wei, T. Tomohiro, M.
Kodaka, H. Okuno, J. Org. Chem. 2000, 65, 8979Ϫ8987.
M. Takeshita, M. Irie, J. Org. Chem. 1998, 63, 6643Ϫ6649.
Chamontin, V. Lokshin, V. Rossollin, A. Samat, R. Gugliel-
metti, Tetrahedron 1999, 55, 5821Ϫ5830.
M. Tanaka, K. Kamada, H. Ando, K. Kitagaki, Y. Shibutani,
K. Kimura, J. Org. Chem. 2000, 65, 4342Ϫ4347.
8h]
[18]
[19]
[
9]
[
10] [10a]
M. Inouye, M. Ueno, K. Tsuchiya, N. Nakayama, T. Koni-
The supporting information shows the UV/Vis absorption
spectra indicating the thermal isomerization tendencies of the
corresponding crowned spirobenzopyrans, for supporting in-
formation see also the footnote on the first page of this article.
C. Reichardt, Chem. Rev. 1994, 94, 2319Ϫ2358.
shi, T. Kitao, J. Org. Chem. 1992, 57, 5377Ϫ5383. [
10b]
O. A.
Fedorova, S. P. Gromov, Y. V. Pershina, S. S. Sergeev, Y. P.
Strokach, V. A. Barachevsky, M. V. Alfimov, G. Pepe, A. Sa-
mat, R. Guglielmetti, J. Chem. Soc., Perkin Trans. 2 2000,
[20]
563Ϫ570.
[21] [21a]
J. Pozzo, A. Samat, R. Guglielmetti, R. Dubest, J. Aubard,
[
[
11]
[21b]
H. Sasaki, A. Ueno, J. Anzai, T. Osa, Bull. Chem. Soc., Jpn.
986, 59, 1953Ϫ1956.
Helv. Chim. Acta 1997, 80, 725Ϫ738.
J. Pozzo, V. Lokshin,
1
A. Samat, R. Guglielmetti, R. Dubest, J. Aubard, J. Photo-
chem. & Photobiol. A: Chem. 1998, 114, 185Ϫ191.
Received February 6, 2003
12] [12a]
M. Inouye, K. Akamatsu, H. Nakazumi, J. Am. Chem.
Soc. 1997, 119, 9160Ϫ9165. [
12b]
M. Inouye, Y. Noguchi, K.
2442
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 2437Ϫ2442