Brominated methanes as photoresponsive molecular storage of elemental Br2

Article abstract of DOI:10.1002/asia.201200322

The photochemical generation of elemental Br₂ from brominated methanes is reported. Br₂ was generated by the vaporization of carbon oxides and HBr through oxidative photodecomposition of brominated methanes under a 20 W low-pressure mercury lamp, wherein the amount and situations of Br₂ generation were photochemically controllable. Liquid CH ₂Br₂ can be used not only as an organic solvent but also for the photoresponsive molecular storage of Br₂, which is of great technical benefit in a variety of organic syntheses and in materials science. By taking advantage of the in situ generation of Br₂ from the organic solvent itself, many organobromine compounds were synthesized in high practical yields with or without the addition of a catalyst. Herein, Br₂ that was generated by the photodecomposition of CH₂Br₂ retained its reactivity in solution to undergo essentially the same reactions as those that were carried out with solutions of Br₂ dissolved in CH ₂Br₂ that were prepared without photoirradiation. Furthermore, HBr, which was generated during the course of the photodecomposition of CH₂Br₂, was also available for the substitution of the OH group for the Br group and for the preparation of the HBr salts of amines. Furthermore, the photochemical generation of Br₂ from CH₂Br₂ was available for the area-selective photochemical bleaching of natural colored plants, such as red rose petals, wherein Br₂ that was generated photochemically from CH ₂Br₂ was painted onto the petal to cause radical oxidations of the chromophoric anthocyanin molecules. The generation of Br ₂ from brominated methanes occurred upon photoirradiation under O₂. The solutions that contained elemental Br₂ were useful for the synthesis of organobromine compounds and the macroscopic photochemical bleaching of colored plants. Copyright

Full text of DOI:10.1002/asia.201200322

DOI: 10.1002/asia.201200322
Brominated Methanes as Photoresponsive Molecular Storage of Elemental
Br2
Kazumitsu Kawakami and Akihiko Tsuda*[a]
Chem. Asian J. 2012, 00, 0 – 0
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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FULL PAPER
Abstract: The photochemical genera-
tion of elemental Br2 from brominated
methanes is reported. Br2 was generat-
ed by the vaporization of carbon
oxides and HBr through oxidative pho-
todecomposition of brominated meth-
anes under a 20 W low-pressure mercu-
ry lamp, wherein the amount and situa-
tions of Br2 generation were photo-
chemically controllable. Liquid CH2Br2
can be used not only as an organic sol-
vent but also for the photoresponsive
molecular storage of Br2, which is of
great technical benefit in a variety of
organic syntheses and in materials sci-
ence. By taking advantage of the in
situ generation of Br2 from the organic
solvent itself, many organobromine
compounds were synthesized in high
practical yields with or without the ad-
dition of a catalyst. Herein, Br2 that
was generated by the photodecomposi-
tion of CH2Br2 retained its reactivity in
solution to undergo essentially the
same reactions as those that were car-
ried out with solutions of Br2 dissolved
in CH2Br2 that were prepared without
photoirradiation. Furthermore, HBr,
which was generated during the course
of the photodecomposition of CH2Br2,
was also available for the substitution
of the OH group for the Br group and
for the preparation of the HBr salts of
amines. Furthermore, the photochemi-
cal generation of Br2 from CH2Br2 was
available for the area-selective photo-
chemical bleaching of natural colored
plants, such as red rose petals, wherein
Br2 that was generated photochemical-
ly from CH2Br2 was painted onto the
petal to cause radical oxidations of the
chromophoric anthocyanin molecules.
Keywords: bleaching · bromine ·
molecular storage · photochemistry ·
vaporization
Introduction
sulting bromine water can bring about bromination reac-
tions.[4] Whilst, N-bromosuccinimide (NBS) can also gener-
ate elemental Br2 in CCl4 upon heating, photoirradiation, or
by reaction with a base, it is actually used as the bromine
source in free-radical bromination reactions.[5,6] However,
the generation of elemental Br2 from these reagents occurs
under specific conditions with the chemical contamination
of the system by the resulting side-products and/or the
added reagents. Against this background, herein, we report
the photochemical generation of Br2 from brominated meth-
anes with the vaporization of the side-products, such as
carbon oxides and HBr, upon exposure to UV light under
O2 (Scheme 1, Equation (2)). The resulting sample solutions
Elemental Br2 is one of the most-useful reagents for the syn-
theses of organobromine compounds and is used in a wide
variety of organic reactions;[1] however, it is extremely cor-
rosive, as well as toxic to living organisms. Br2 is a fuming
red/brown liquid at room temperature and it slowly vaporiz-
es at room temperature, even when it is stored in screw-type
vials through the interface of the glass wall and plastic cap.
Thus, it is usually stored in glass ampules and corrosive-re-
sistant steel tanks in the laboratory and in industrial settings,
respectively. To avoid experimental hazards, chemists can
temporarily convert toxic/caustic reagents into different
compounds with non- or low toxicity/causticity or into easy-
to-handle liquids or solids and utilize them in the target re-
actions through their in situ chemical regeneration. For ex-
ample, phosgene, which has the chemical formula COCl2
and is an extremely toxic gas at room temperature but is
a very important building block for the industrial synthesis
of a variety of compounds, is frequently used by its in situ
generation through the decomposition of triphosgene with
a base.[2] Effectively, triphosgene performs the molecular
storage of phosgene. In the same way, the chemical storage
of Br2, instead of the conventional physical procedures, also
furnishes great technical benefits, as well as scientific ad-
vancements, for a variety of organic syntheses and in materi-
al sciences.[3] Some inorganic salts that contain bromine,
such as KBr, have been known to generate Br2 through re-
actions with oxidizing reagents in acidic water and the re-
Scheme 1. Thermochemical storage (1) and photochemical release (2) of
Br2 by using brominated methanes.
that contained elemental Br2 are useful for a variety of ap-
plications, such as the synthesis of organobromine com-
pounds in high practical yields and the macroscopic photo-
chemical bleaching of colored plants that contain natural
dye compounds. Because brominated methanes can be pre-
pared from the thermal bromination reactions of CH4 with
Br2, wherein Uner and co-workers have achieved above
90% conversion of CH4 with high CH2Br2 selectivity (above
90%; Scheme 1, Equation (1)),[7] the reactions presented
herein have accomplished the complete chemical storage
and release of elemental Br2 by using brominated methanes.
[a] K. Kawakami, Prof. Dr. A. Tsuda
Department of Chemistry, Graduate School of Science
Kobe University
1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501 (Japan)
Fax : (+81)78-803-5671
E-mail: tsuda@harbor.kobe-u.ac.jp
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201200322.
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Photoresponsive Molecular Storage of Elemental Br2
The photodecomposition of chlorinated methanes has
been actively studied in environmental science and sustaina-
ble chemistry because of their potential hazard to life and
health and their properties as environmental pollutants.[8–14]
For example, the photodecomposition of CHCl3 proceeds
through the generation of highly toxic COCl2, CO, Cl2, and
HCl, together with CO2 under an O2 atmosphere. Some ex-
amples related to the photodecomposition of brominated
methanes have also been reported at the analytical level.
Lin and co-workers succeeded in detecting the molecular
elimination of Br2 in 248 nm photolysis of bromoform
(CHBr3) by using cavity ring-down absorption spectrosco-
py.[15c] North and co-workers reported a computational study
of the atmospheric oxidation of CH2Br2 and CHBr3 that was
initiated by UV photolysis,[16] but no example has been re-
ported for the experimental photodecomposition of the less-
brominated CH2Br2. Because the photodecomposition of
brominated methanes is still an ambiguous qualitative
issue,[15–19] the use of their photodecomposed products has
hardly attracted any attention as practically available ele-
mental sources in organic synthesis and material sciences.
Herein, we report that brominated methanes, in particular
CH2Br2, upon exposure to UV light efficiently generate ele-
mental Br2, which is practically available for a variety of ap-
plications.
Results and Discussion
Photochemical Generation of Br2 from Brominated
Methanes
Low-pressure mercury lamps, most of which have low elec-
trical power consumption, typically generate ultraviolet light
with wavelengths of 184.9 and 253.7 nm, which cover the
electronic absorption bands of brominated methanes that
À
À
are due to s s* and/or n s* transitions (see the Supporting
Information, Figure S1).[15,20] Thus, the lamp (20 W, 24ꢁ
120 mm) was inserted into the solution in a 28 mm quartz-
glass jacket that was fixed in the center of a cylindrical flask
(42 mm; Figure 1a). For example, in this glass vessel, the ex-
posure of liquid CH2Br2 (10 mL) to UV light under a flow
of O2 (30 mLminÀ1) at 408C caused a gradual color change
from colorless to brownish orange. Moreover a 4.6% de-
Abstract in Japanese:
Figure 1. Photodecomposition of CH2Br2 upon exposure to UV light
under a flow of O2 at 408C with a 20 W low-pressure mercury lamp.
a) Photographs before and after photoirradiation. b) Changes in the ab-
sorption spectra of CH2Br2, measured upon 150-fold dilution with
MeOH. c) GCMS and d) 1H and 13C NMR spectroscopy (CDCl3) of pho-
todecomposed CH2Br2 after photoirradiation for 3 h.
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Kazumitsu Kawakami and Akihiko Tsuda
FULL PAPER
crease in weight and approximately 0.8% volatilization
versus the reference experiment without photoirradiation
were observed after 3 hours, most likely owing to the gener-
ation of volatile photodecomposed products from CH2Br2.
The absorption spectra of the sample solution, upon dilution
with MeOH, showed a characteristic absorption band that
corresponded to Br2 in the UV/Vis region (lmax =379 nm,
Figure 1b).[21] GCMS, which was used to qualitatively evalu-
ate the photodecomposed products of CH2Br2, also indicat-
ed the presence of Br2 and COBr2 at m/z=160 and 188, re-
spectively, with their characteristic isotope patterns (Fig-
ure 1c).[16] However, no notable peaks for the photodecom-
posed products of comparable integration with those of
thereby resulting in an increase in Br2 concentration in the
system (Scheme 2). We expected that these reactions could
also generate possible higher-brominated hydrocarbons
owing to radical cross-coupling and bromination reactions of
the halomethane radicals in the proposed mechanism. How-
ever, magnified NMR spectra (Figure 1d) indicated that the
resulting sample solution only contained an extremely small
amount of the higher-brominated CHBr3, which had a chemi-
cal shift of d=6.83 ppm. Hence, elemental Br2 that was gen-
erated in the CH2Br2 solution was stable in the closed ves-
sels at room temperature, tolerant of long-term storage, and
available for use in a variety of applications.
The higher-brominated CHBr3, which also existed as
a liquid at room temperature, showed an analogous color
change upon photoirradiation and the degree of photogener-
ation of Br2 was more rapid compared with CH2Br2 (see the
Supporting Information, Figure S2). The fully brominated
methane, CBr4, which exists as a solid, generated a brownish
gas upon exposure to UV light, without any notable changes
in its crystalline structure (see the Supporting Information,
Figure S3). These brominated-methane compounds did not
show the color change owing to Br2 generation in common
organic solvents, such as n-hexane, benzene, acetone, or
simple alcohols, which were capable of reacting with Br2 or
reducing the radical photolysis of the carbon–bromine
bonds. However, when solutions that contained the bromi-
nated methanes in CCl4, CHCl3, or CH2Cl2 were exposed to
UV light, they showed the characteristic color changes
owing to Br2 generation. Representatively, the solutions of
the brominated methanes in CHCl3 after exposure to UV
light for 1 hour showed stronger absorbance owing to Br2
generation in the order CBr4, CHBr3, and CH2Br2
(Figure 2). The concentrations of Br2 in sample solutions
that were prepared from solutions of the brominated meth-
anes (1m) in CHCl3 (10 mL) were approximately 0.80, 0.43,
and 0.21m, respectively. Thus, the chlorinated methane sol-
vents may accelerate the photolysis of the carbon–bromine
bonds, in harmony with their radical photolysis of the
carbon–chlorine bonds.[13] As a control reaction, N-bromo-
1
CH2Br2 were observed in both the H and 13C NMR spectra
(Figure 1d). The concentration of Br2 steadily increased
with the photoirradiation time (Figure 1b) and was deter-
mined by UV/Vis spectroscopy to be 0.92m after 3 hours by
reference to a standard solution of Br2 in CH2Br2. The
change in absorbance upon photoirradiation clearly deceler-
ated under a flow of Ar, instead of O2, thereby indicating
that the oxidative photodecomposition of CH2Br2 actually
accelerated the generation of Br2, presumably owing to the
formation of carbon oxides. Elemental Br2, which has a boil-
ing point of 58.88C (neat), was condensed with a little va-
porization in the solution by the photodecomposition of
CH2Br2, but most of the other photodecomposed products
with low boiling points, such as HBr and carbon oxides,
could have escaped out of the system under a flow of O2 at
408C (Scheme 1, Equation (2)). HBr could actually be
trapped by amines to form their corresponding HBr salts
outside of the system (see below). The reactions may pro-
ceed through two possible mechanisms: the initial photolytic
cleavage of a carbon–bromine bond (path a) or through the
radical substitution of a hydrogen atom in CH2Br2 by the
bromine radical (path b).[16] Subsequent reactions of the re-
sulting halomethane radicals with oxygen would generate
the corresponding peroxy radicals to give formaldehyde,
formyl bromide, and bromophosgene in a Russell mecha-
nism.[22] The carbonyl compounds that carry bromine atoms
further decompose to give carbon monoxide and dioxide,
À
succinimide (NBS), which contains a N Br bond that is
Scheme 2. Possible photodecomposition pathways of CH2Br2.
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Photoresponsive Molecular Storage of Elemental Br2
Table 1. Bromination reactions of anisole with photodecomposed bromi-
nated methanes.[a]
Entry
Brominated methane
t [h][b]
Yield [%][c]
1Br
1Br2
1
2
3
4
5
6
7
CH2Br2
CH2Br2
CHBr3
0.5
24
93
51
90
18
65
65
17
–
39
–
–
–
0.5
0.5
0.5
0.5
0.5
CH2Br2 in CHCl3
CHBr3 in CHCl3
CBr4 in CHCl3
CBr4 in CH2Cl2
21
–
[a] Reactions were carried out by using mixtures of anisole (1.5 mmol)
and liquid brominated methanes (10 mL) or chlorinated methane solu-
tions (10 mL) that contained brominated methane (10 mmol), which had
been exposed to UV light with a 20 W low-pressure mercury lamp.
[b] Stirring time after the addition of anisole. [c] Yield of isolated prod-
uct; the distribution of the mono- and disubstituted products was deter-
Figure 2. Absorption spectra (top) and the evaluated concentrations of
Br2 (bottom) of photodecomposed solutions of CH2Br2, CHBr3, and CBr4
in CHCl3 measured upon 150-fold dilution with MeOH at 208C. The
CHCl3 solutions were exposed to UV light under a flow of O2 at 408C
for 1 h with a 20 W low-pressure mercury lamp.
1
mined by H NMR spectroscopy.
the products to 67% without recovery, presumably owing to
the photodegradation of both the substrate and the prod-
ucts.[23] Moreover, the reactions in photodecomposed solu-
tions of CH2Br2 that were prepared upon exposure to UV
light under a flow of air or Ar instead of O2 led to lower
yields of 4-bromoanisole (40% and 13%, respectively);
these results can be reasonably explained by the decelera-
tion in the generation of Br2, as described above.
À
weaker than that of a typical C Br bond, also decomposed
in CHCl3 at 408C upon photoirradiation to generate Br2
(see the Supporting Information, Figure S4); the concentra-
tion of Br2 after 1 hour was approximately 0.26m, which re-
sulted from 52% consumption of NBS. Although brominat-
ed methanes have the potential advantage over NBS of car-
rying multiple bromine atoms in a molecule, CBr4 and
CHBr3 can actually generate larger amounts of Br2 in the
system and even CH2Br2 attained a comparable concentra-
tion to NBS.
Liquid CHBr3, which can rapidly generate a large amount
of Br2 upon photoirradiation, also allowed the monobromi-
nation of anisole in 90% yield under essentially identical
conditions (Table 1, entry 3). Furthermore, the bromination
reactions also occurred with photodecomposed solutions of
CH2Br2, CHBr3, or CBr4 in CHCl3 or CH2Cl2. When anisole
(0.16 g, 1.5 mmol) was added into solutions of the brominat-
ed methane (6.7 equiv, 10 mmol) in CHCl3 (10 mL) that had
been exposed to UV light under a flow of O2 for 3 hours,
only 4-bromoanisol was obtained from CH2Br2 and CHBr3
in 18% and 65% yield, respectively (Table 1, entries 4 and
5, respectively). Moreover, a 3:1 mixture of the mono- and
dibrominated products were obtained in a combined 86%
yield with a solution of CBr4 in CHCl3 (Table 1, entry 6).
From the UV/Vis spectra of the series of brominated meth-
anes in CHCl3 after photoirradiation (Figure 2), the ob-
served yields of the bromination reactions mainly depended
on the amount of Br2 that was generated in the reaction sys-
tems. As expected from our above hypothesis, the radical
species that were generated from chlorinated methane sol-
vents under exposure to UV light accelerated the photode-
composition of the brominated methanes, only 17% yield of
4-bromoanisole was obtained with a photoirradiated solu-
tion of CBr4 in CH2Cl2, whose solvent had a higher stability
under UV light (Table 1, entry 7).
Bromination Reactions of Anisole with Photodecomposed
Brominated Methanes
These results for the photogeneration of Br2 from brominat-
ed methanes were applied in the bromination of anisole 1 in
photodecomposed neat liquids of CH2Br2 or CHBr3, or solu-
tions of the brominated methanes in CHCl3. Anisole
1 (0.16 g, 1.5 mmol) was added directly into photodecom-
posed CH2Br2 (10 mL), which was prepared upon exposure
to UV light under a flow of O2 for 3 hours at 408C, and the
sample solution was stirred at 208C. 4-Bromoanisole (1Br)
was isolated in 93% yield after stirring for 0.5 hours
(Table 1, entry 1), whilst a mixture of compound 1Br and di-
bromoanisole (1Br2) were obtained in 51% and 39% yield,
respectively, upon prolonging the reaction time to 24 hours
(Table 1, entry 2). When an excess amount of compound
1 was added into the solution of CH2Br2, the brownish color
of the CH2Br2 solution, which originated from Br2, immedi-
ately disappeared and compound 1Br was obtained with the
recovery of the unreacted substrate. A one-pot reaction,
which was performed upon the direct photoirradiation of
a solution of compound 1 in CH2Br2, decreased the yield of
Here, one must notice that the these decomposed chloro-
methane solutions need careful handling because they con-
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tain extremely toxic phosgene (COCl2) together with other
inorganic products, such as Cl2 and HCl, which may bring
about unexpected side-reactions.[13,24] However, the corre-
sponding bromophosgene (COBr2) is known to be unstable
and thus likely to decompose immediately at room tempera-
ture or under exposure to light to produce Br2, as well as
carbon oxides (Scheme 2).[25–28] To avoid chemical hazards,
as well as unexpected side-reactions in synthetic applications
(see below), the neat liquid brominated methanes may be
highly preferred in a variety of applications.
the addition of Br2 to the triple bonds, thereby affording the
dibrominated adduct in 76% yield and a 5:1 mixture of the
di- and tetrabrominated compounds in a combined 98%
yield (Table 2, entries 10 and 11). a-Bromination reactions
occurred upon the addition of carbonyl compounds into the
photodecomposed liquid CH2Br2. Acetophenone (13) gave
a dibromination product in 97% yield and dibenzoylme-
thane (14) also predominantly underwent dibromination at
the a-carbon atoms (Table 2, entries 12 and 13, respective-
ly). Furthermore, the addition of toluene (15) to the photo-
decomposed CH2Br2 solution gave benzyl bromide (15Br) in
75% yield, together with a small amount of dibrominated
15Br2 in 4% yield, as reported previously in the radical bro-
mination reaction of toluene with Br2 (Table 2,
entry 14).[29,30]
General Synthesis of Organobromine Compounds with
Photodecomposed CH2Br2
We have demonstrated the bromination reactions of a varie-
ty of compounds that are capable of reacting with Br2 in
photodecomposed CH2Br2 (Table 2). These reactions were
carried out by the addition of 1.5 mmol of the substrate into
photodecomposed CH2Br2 (10 mL) that was prepared upon
exposure to UV light with a 20 W low-pressure mercury
lamp at 408C for 1 hour or 3 hours and the reaction was
monitored by TLC and/or HPLC. Veratrol (2) allowed the
monobromination at the 4-position to give product 2Br in
93% yield with the solution that was prepared upon expo-
sure to UV light for 1 hour, but dibromination at the 4,5-po-
sitions occurred to give product 2Br2 in 99% yield with the
solution that was prepared upon prolonged photoirradiation
for 3 hours (Table 2, entry 1). Compared with the reaction
of compound 1, methyl p-anisate (3), which contained an
electron-withdrawing methyl ester group, slowly underwent
bromination at the 3-position to give only the monobromi-
nated product in 83% yield (Table 2, entry 2). Anthracene 4
quantitatively gave dibrominated products (Table 2,
entry 3). Although non-substituted five-membered heterocy-
clic pyrrole and furan gave turbid complicated reaction mix-
tures in photodecomposed CH2Br2, probably owing to oxi-
dation reactions, thiophene (5) and 2,3,4-trisubstituted pyr-
role 6 afforded their corresponding dibromination and a-
bromination products in 83% and 78% yield, respectively
(Table 2, entries 4 and 5). Acetanilide 7 underwent bromina-
tion at the 4-position of the phenyl ring and nitrogen atom
of the amide group to give the dibrominated product in
93% yield (Table 2, entry 6).
The photochemically generated Br2 in the CH2Br2 solu-
tion also brought about the bromination of alkenyl com-
pounds. 1-Decene (8) allowed the dibromination reaction in
97% yield, whilst (Z)-cyclooctene (9) produced trans-1,2-di-
bromocyclooctane in 89% yield (Table 2, entries 7 and 8, re-
spectively). (E)-Stilbene (10) also underwent dibromination
to give mixtures of the anti-adducts with meso-configura-
tions and the thermally more-stable racemic (1S,2S) and
(1R,2R) isomers in 15% and 52%, respectively, in the initial
stage of the reaction (Table 2, entry 9). The reaction pro-
ceeded with an accompanying isomerization step to give
only the latter racemic isomers in 82% yield by prolonging
the reaction time to 10 hours. Alkynyl compounds, such as
1,4-butynediol (11) and p-ethynyltoluene (12), also allowed
Oxidative Bromination Reactions of Aniline and Phenol
Derivatives
The addition of aniline (16) into photodecomposed CH2Br2
afforded a turbid, complicated reaction, most likely owing
to its oxidation and condensation in the acidic media,
whereas p-toluidine (17), which contained a methyl group at
the 4-position, predominantly afforded the 2,6-dibrominated
compound (17Br2) in 37% yield, together with tetrabromi-
nated azotoluene (17Br2)2 in 14% yield (Table 3, entries 1
and 2, respectively; also see the Supporting Information,
Figure S5). Because p-toluidine (17) is known to cause an
oxidative coupling reaction to form azotoluene, the forma-
tion of compound (17Br2)2 is reasonable in this reaction
system.[31] Notably, we could not find the formation of any
of the urea derivatives, which was a possible side-product if
COBr2 had formed (Scheme 2);[32] COBr2 was detected by
GCMS (Figure 1c) in the photodecomposition of CH2Br2.
These results, together with the 13C NMR study (Figure 1d),
indicated that the photodecomposed CH2Br2 solution con-
tained very little COBr2, probably owing to its instability as
described above (Scheme 2).
On the other hand, similar to the case of anisole (1;
Table 1, entry 1), phenol (18) gave 2,4-dibromophenol in
93% yield (Table 3, entry 3). 2,4-Di-tert-butylphenol (19)
underwent a monobromination reaction at the 6-position to
give compound 19Br in 62% yield, but 4,6-dibrominated
19Br2, which had an oxidized dienone structure, was also ob-
tained in 28% yield (Table 3, entry 4). The structure of com-
pound 19Br2 was determined by spectroscopic measure-
ments and by single-crystal X-ray crystallography. In the
single-crystal structure, the 6-membered ring included an sp3
carbon at the 4-position and C2=C3, C5=C6, and C1=O1
double bonds with lengths 1.32, 1.32, and 1.22 ꢂ, respective-
ly (Figure 3).[33] Because the isolated 19Br was successfully
converted into 19Br2 in 93% isolated yield when it was
added into photodecomposed CH2Br2 and stirred at 208C
for 4 hours, compound 19Br2 was most likely formed
through the temporal formation of 19Br.
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Photoresponsive Molecular Storage of Elemental Br2
pounds 1, 3, 10, and 13 (1.5 mmol) by mixing with elemental
Br2 in CH2Br2 without photoirradiation (Scheme 3). For an
accurate evaluation, a solution of Br2 in 1m CH2Br2 (10 mL)
was prepared for all of the reactions wherein the amount of
Control Bromination Reactions with Elemental Br2
To assess the reactivity of Br2 in the solutions of photode-
composed CH2Br2, we performed control reactions of com-
Table 2. Synthesis of organobromine compounds with photodecomposed CH2Br2 solutions.[a]
Entry
Substrate
Products
t [h]
Photoirradiation
T [8C]
Yield [%][c]
Stirring[b]
2Br: 93
2Br2: 4
2Br: 0
1
3
1
1
50
50
1
2
2Br2: 99
3
12
40
83
3
4
3
3
2
2
20
20
99
83
5
6
3
3
2
2
20
40
78
93
7
8
3
3
2
2
20
0
97
89
meso: 15
rac: 52
meso: 0
rac: 82
3
3
2
20
20
9
10
10
11
1
1
1
1
40
40
76
12Br: 81
12Br2: 17
12
3
2
0
97
14Br: 17
14Br2: 73
13
14
3
3
2
6
20
20
15Br: 75
15Br2: 4
[a] Reactions were carried out upon mixing 1.5 mmol of substrate and photodecomposed CH2Br2 (10 mL), which was prepared upon exposure to UV light
with a 20 W low-pressure mercury lamp at 408C. [b] Stirring time after the addition of the reaction substrates. [c] Yield of isolated product; the distribution
1
of the mono- and disubstituted products was determined by H NMR spectroscopy.
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Table 3. Bromination reactions of aniline and phenol derivatives in solutions of photodecomposed CH2Br2.[a]
Entry
Substrate
Products
t [h]
Photoirradiation
Yield [%][c]
Stirring[b]
1
1
complicated mixture
3
–
17Br2: 37
2
3
4
3
3
3
1
2
2
ACHTUNGTRENNUNG
93
19Br: 62
19Br2: 28
[a] Reactions were carried out at 208C upon mixing the substrate (1.5 mmol) and photodecomposed liquid CH2Br2 (10 mL), which was prepared upon expo-
sure to UV light with a 20 W low-pressure mercury lamp at 408C. [b] Stirring time after the addition of the substrates. [c] Yield of isolated product; the dis-
1
tribution of the mono- and disubstituted products was determined by H NMR spectroscopy.
other hand, dibrominated stilbene (10Br2) in the photode-
composed CH2Br2 likely accelerated the structural rear-
rangement from meso-10Br2 into a thermally stable rac-
10Br2 in the presence of HBr.[35]
Bromination Reactions with HBr in Photodecomposed
CH2Br2
Because the solution of photodecomposed CH2Br2 not only
contains Br2 but also saturated HBr, it should also be appli-
cable to acid-catalyzed bromination reactions with HBr. A
substitution reaction of a hydroxy group of a tertiary alcohol
with a bromine atom has been known to occur with HBr
Figure 3. ORTEP of 19Br2. Ellipsoids set at 50% probability, hydrogen
atoms are omitted for clarity.[33]
through an SN1 mechanism. When 1-adamantanol (20) was
added into a solution of photodecomposed CH2Br2 and
Br2 in the absorption spectra was approximately the same as
that prepared from CH2Br2 upon exposure to the light for
3 hours at 408C. Interestingly, the observed brominated
products and the yields of the control reactions were similar
to the reactions in photodecomposed CH2Br2, thus indicat-
ing that the elemental Br2 that was generated by photoirra-
diation actually kept its reactivity in the resulting CH2Br2
solution. However, the small differences that appeared in
the ratios of the mono- and dibrominated products in the re-
action of compound 1 and between the meso- and racemic
isomers in the reaction of compound 10 (Scheme 3a versus
Table 1, entry 1, and Scheme 3c versus Table 2, entry 9, re-
spectively) indicated that other photodecomposed products,
such as HBr, contributed to the reactions. Because electron-
withdrawing groups decreased the reactivity of the attached
phenyl ring for the electrophilic substitution of Br2, com-
pound 1 in the photodecomposed CH2Br2 solution might de-
crease the electron density of the phenyl ring through weak
interactions of the alkoxide group with H+ ions.[34] On the
stirred under reflux for 10 hours, the hydroxy group was suc-
cessfully converted into a bromine group to give compound
20Br in 99% yield (Scheme 4, top). However, cyclohexanol
(21), a secondary alcohol, upon addition into a solution of
photodecomposed CH2Br2, underwent mono- and dibromi-
nation to provide compounds 21Br and trans-21Br2 in 49%
and 31% yield, respectively (Scheme 4, bottom). These re-
actions can be explained by an acid-catalyzed mechanism
owing to the generation of HBr by the photodecomposition
of CH2Br2, as well as the possible radical-bromination reac-
tions of CH2Br2 by the photochemically generated Br2. In
the reaction of compound 20, initial dehydration catalyzed
by H+ ions may allow the formation of a tertiary carbocat-
ion and subsequent addition of BrÀ would result in the for-
mation of compound 20Br. In the reaction of compound 21,
a similar dehydration step may initially occur to generate
a secondary carbocation for the formation of a double bond
in the cyclic ring; subsequent addition of Br2 into the double
bond gives dibrominated compound trans-21Br2.
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Photoresponsive Molecular Storage of Elemental Br2
reactions. No bromination reac-
tion of benzene was observed
in photodecomposed CH2Br2 at
408C.
However,
when
1.2 equivalents of iron powder
was added into the solution and
the mixture was stirred for
2 hours,
1,2,4-tribromobenzene,
1,4-dibromobenzene,
and
1,2,4,5-tetrabromobenzene were
obtained in 11%, 27%, and
60%
yield,
respectively
(Scheme 5; also see the Sup-
porting Information, Figure S6).
This result indicates that iron in
photodecomposed CH2Br2 is ac-
tually converted into FeBr3
through a reaction with Br2 and
brings about the catalytic bro-
mination reactions of benzene
in the solution.[3f,36,37]
Multiple Bromination
Reactions of Large Aromatic
Compounds
Scheme 3. Control bromination reactions of compounds 1, 3, 10, and 13 with liquid Br2.
Large disk-shaped aromatic compounds, such as hexaphe-
nylbenzene (HPB) and metalloporphyrin derivatives that
don’t contain lipophilic substituents, generally have poor sol-
ubility into organic solvents, whereas they show relatively
higher solubility into halomethane solvents. Thus, these sol-
utions of photodecomposed brominated methane are consid-
ered to be suitable as a medium for bromination reactions.
It has been known that HPB allows hexabromination in
neat Br2 and meso-substituted metalloporphyrins also under-
go octabromination in CHCl3 solutions that contain Br2.[38,39]
When we carried out the reaction of HPB with photodecom-
posed CH2Br2, which was prepared upon exposure to UV
light for 6 hours at 408C, the multibromination reaction pro-
ceeded very slowly under reflux conditions. To increase the
concentration of Br2 in the reaction system, we chose
CHBr3 as a solvent. HPB was successfully converted into
the hexabrominated form of hexakis(4-bromophenyl)ben-
zene as the sole product in 86% yield in photodecomposed
CHBr3, which was prepared upon exposure to UV light for
6 hours at 408C, by heating at reflux for 7 days (Scheme 6,
Scheme 4. Bromination reactions of compounds 20 and 21 in photode-
composed CH2Br2.
On the other hand, considering the bromine-atom econo-
my, the vaporized HBr should also be useful for other reac-
tions, such as the formation of the HBr salts of amines. We
also found that the HBr salts of amines were efficiently ob-
tained by using the photodecomposed gas of CH2Br2 outside
of the photoreaction system. For example, the exposure of
1.0 mmol solutions of triethylamines in MeOH to photode-
composed CH2Br2 gas for 5 hours actually provided their
corresponding HBr salts in 88% yield.
IronACHTUNGTRENNUNG
Because the solution of photodecomposed CH2Br2 includes
Br2 without any notable chemical contamination, this solu-
Scheme 5. Iron
ACHTUNGTREN(NUGN III)-catalyzed bromination reaction of benzene in photo-
tion was also applicable to ironACTHNUTRGNEUGN(III)-catalyzed bromination
decomposed CH2Br2.
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Kazumitsu Kawakami and Akihiko Tsuda
FULL PAPER
Figure 4. Photochemical bleaching of red rose petals with CH2Br2.
a) Before (left) and after (right) exposure of the rose petal to UV light in
CH2Br2 (1 mL) for 10 min at 208C under a flow of O2 with a 20 W low-
pressure mercury lamp. b) Chemical structure of rose anthocyanin. c) A
cross-shape appeared on
a rose petal through painting with liquid
CH2Br2 and subsequent UV irradiation.
of quinoidal structures, which are highly dependent on the
environmental pH value, thereby resulting in color changes
or bleaching.[44] As one can expect from the oxidative bro-
mination reaction of compound 19 in photodecomposed
CH2Br2, which afforded dienone 19Br2 (Table 3, entry 4),
the radical oxidation of the flavylium ions owing to Br2 is
one of the plausible pathways to decolorize the anthocyanin
dye. Because Br2 can form HOBr, a strong oxidant, in
water, HOBr may also contribute to the oxidation of the an-
thocyanin molecules in the petal.[45] Then, by taking advant-
age of CH2Br2, a photoresponsive liquid-chemical storage of
Br2, we succeeded in drawing on the petal. Crossed lines
were painted on the petal with CH2Br2 and the petal was
subsequently exposed to UV light under a flow of O2. The
painted area was gradually bleached and clear crossed lines
appeared as shown in Figure 4c. The liquid CH2Br2 that was
adsorbed onto the surface or penetrated into the petal may
generate Br2 upon exposure to the light, thereby resulting in
the local oxidation of the anthocyanin molecules that are in-
volved in the painted area.
Scheme 6. Bromination reactions of hexaphenylbenzene and PdII–por-
phyrin in photodecomposed CH2Br2.
top). Moreover, a solution of 5,10,15,20-tetrakis(3,5-di-tert-
butylphenyl)porphyrinato palladium(II) in photodecom-
posed CH2Br2 allowed octabromination at the pyrrole b-po-
sitions in 84% yield by heating at reflux for 2 hours
(Scheme 6, bottom).
Photochemical Bleaching of Colored Natural Plants
Radical reagents, such as H2O2 and 2,2’-azobis-2-methyl-
propanimidamide dihydrochloride (AAPH), have been
known to bleach colored natural materials.[40] Finally, we
demonstrated the photochemical bleaching of flower petals
by the photochemical generation of Br2 from liquid CH2Br2.
A red rose petal was immersed in a solution of CH2Br2
(1 mL) and exposed to UV light under a flow of O2 at 208C
for 10 min. The red color of the rose became gradually de-
colorized upon photoirradiation, but no change was ob-
served without CH2Br2 or photoirradiation (Figure 4a). De-
colorization also occurred when the petal was immersed di-
rectly in photodecomposed CH2Br2. Thus, Br2 that is gener-
ated in photodecomposed CH2Br2 most likely brings about
the observed decolorization of the rose petal. It is well-
known that the color of the rose petals originates from an
anthocyanin dye that is composed of a chromophoric flavyli-
um ion and hydrophilic sugar components (cyanidine 3,5-O-
diglucoside; Figure 4b).[41–43] Oxidation of the flavylium ions,
which contain multiple hydroxy groups, allows cleavage of
the C=O+ bond of the benzopyrylium ring and/or formation
Conclusions
In this study, we have reported the photochemical genera-
tion of elemental Br2 from brominated methanes upon pho-
toirradiation with a 20 W low-pressure mercury lamp and
successfully used these events in organic synthesis and in
materials science. Despite the low electric power of the
lamp, the brominated methanes, such as CH2Br2, can effi-
ciently decompose to give Br2 with the vaporization of
carbon oxides, as well as HBr, upon simple UV irradiation.
The liquid brominated methanes can be used not only as or-
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Photoresponsive Molecular Storage of Elemental Br2
analysis was performed on a YANACO CHN Corder MT-5. X-ray dif-
fraction data were collected on a Bruker SMART APEX II Ultra CCD
diffractometer by using MoKa radiation (l=0.71073 ꢂ) at 298 K. An em-
pirical absorption correction was applied by using the SADABS program.
The structure was solved by direct methods and refined by full-matrix
least-squares calculations on F2 by using the SHELXTL 97 program
package.[48] All non-hydrogen atoms were refined anisotropically and hy-
drogen atoms were added to the calculated positions. The packing dia-
grams were drawn by using ORTEP-3. GCMS was performed on
a Thermo Scientific TRACE GC Ultra spectrometer that was equipped
with a Thermo Scientific ISQ single-quadrupole mass spectrometer and
ganic solvents but also for the photoresponsive molecular
storage of Br2, wherein the amount and situations of Br2
generation are photochemically controllable. By taking ad-
vantage of the in situ generation of Br2 from the organic sol-
vent itself without any notable chemical contamination of
the system, many organobromine compounds can be con-
veniently synthesized in high practical yields with or without
the addition of a catalyst, wherein Br2 that is generated in
CH2Br2 maintains its potential reactivity for the bromination
reactions. As one of the characteristic features of the reac-
tions with photodecomposed CH2Br2, the generated HBr is
available as a reagent for various reactions, such as the sub-
stitution of a hydroxy group, salt formation, and working as
an acid catalyst. Furthermore, liquid CH2Br2 shows the area-
selectable photochemical bleaching of dye molecules that
are involved in natural plants. Although the liquid brominat-
ed methanes, especially CH2Br2, have been mainly used as
organic solvents, this study presents a new potential function
of the brominated methanes in the photoresponsive molecu-
lar storage of elemental Br2, which will furnish great techni-
cal benefits, as well as scientific advancements, in a wide va-
riety of applications.
a
Thermo Scientific TG-SQC capillary column (15 mꢁ0.25 mmꢁ
0.25 mm) and He as the carrier gas.
Typical Procedure for Bromination Reactions
A cylindrical flask (42 mm) was equipped with a 30 mm quartz-glass
jacket at the center of the flask, including a low-pressure mercury lamp,
and charged with CH2Br2 (10 mL). The solution was stirred vigorously in
a flow of O2 at 408C under photoirradiation for 1–3 h. After the photoir-
radiation, the substrate (1.5 mmol) was added into the solution and the
mixture was stirred for 0.5–12 h at 0–508C. After the reaction, the
sample solution was mixed with aqueous NaHCO3 under vigorous stir-
ring. The organic layer was then washed with aqueous Na2S2O3 (2%) and
water. The sample solution was dried over anhydrous Na2SO4 and evapo-
rated to dryness to give the brominated products.
Bromination of Hexaphenylbenzene (HPB)
A cylindrical flask (42 mm) was equipped with a 30 mm quartz-glass
jacket at the center of the flask, including a low-pressure mercury lamp,
and charged with CHBr3 (10 mL). The solution was stirred vigorously in
a flow of O2 at 408C under photoirradiation for 6 hours. After the photo-
irradiation, HPB (50 mg, 0.09 mmol) was added into the solution and the
mixture was heated to reflux for 7 days. The sample solution after the re-
action was evaporated to dryness. The residue was recrystallized with
CHCl3/n-hexane to give hexabrominated HPB as a white solid in 86%
yield (78.0 mg).
Experimental Section
Materials
Unless otherwise stated, all reagents and solvents were used as received.
1,2-Dimethoxybenzene (>99%), anthracene (>97%), cyclooctene
(>95%), acetophenone (>98.5%), and 2,4-di-tert-butylphenol (>97%)
were purchased from Tokyo Kasei Co., Ltd. (TCI). Dibromomethane
(>98%), tetrabromomethane (>98%), aniline (>99%), thiophene
(>98%), 2-butyn-1,4-diol (>98%), 1-adamantanol (>99%), benzene
(>99%), and Na2S2O3·5H2O (>99%) were purchased from Nacalai
Tesque, Inc. Bromoform (>97%), bromine (>99%), methyl p-anisate
(>98%), acetanilide (>99%), 1-decene (>95%), E-stilbene (>98%), p-
ethynyltoluene (>97%), dibenzoylmethane (>98%), toluene (>99%),
p-toluidine (>98%), phenol (>99%), iron powder (À150 mm,>99.9%),
hexaphenylbenzene (>98%), cyclohexanol (>99%), anhydrous
NaHCO3 (>99.5%), and anhydrous Na2SO4 (>99%) were purchased
from Wako Pure Chemical Industries Ltd. CHCl3 (>99%) was purchased
from Kishida Chemical Co. Ltd. Trisubstituted pyrrole 6 and 5,10,15,20-
tetrakis(3,5-di-tert-butylphenyl)porphyrinato palladium(II) were synthe-
sized according to literature procedures.[46,47] Bromoform, including a sta-
bilizer (about 10–20 vol.% EtOH), was washed with water and dried
over Na2SO4 and then freshly distilled under low pressure prior to use.
Most of the brominated products were unambiguously characterized by
1H NMR and IR spectroscopy with reference to the previous studies and
the Aldrich FTNMR and FTIR Libraries (ver. 4.0). New compounds
were characterized by 1H NMR, 13C NMR, and IR spectroscopy, MS
(FAB), elemental analysis, and X-ray diffraction.
Bromination of 5,10,15,20-Tetrakis(3,5-di-tert-butylphenyl)porphyrinato
palladium(II)
A cylindrical flask (42 mm) was equipped with a 30 mm quartz-glass
jacket at the center of the flask, including a low-pressure mercury lamp,
and charged with CH2Br2 (5 mL). The solution was stirred vigorously in
a flow of O2 at 408C under photoirradiation for 1 hour. After the photoir-
radiation, 5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)porphyrinato palla-
dium(II) (10 mg, 0.009 mmol) was added into the solution and the mix-
ture was heated at reflux for 2 h. After the reaction, the sample solution
was mixed with aqueous NaHCO3 under vigorous stirring. The organic
layer was then washed with aqueous Na2S2O3 (2%) and water. The
sample solution was dried over anhydrous Na2SO4 and evaporated to dry-
ness to give the octabrominated PdII–porphyrin as a deep-red solid in
84% yield (13.6 mg).
IronACTHNUTRGNE(UNG III)-Catalyzed Bromination of Benzene
A cylindrical flask (42 mm) was equipped with a 30 mm quartz-glass
jacket at the center of the flask, including a low-pressure mercury lamp,
and charged with CH2Br2 (10 mL). The solution was vigorously stirred in
flowing O2 gas at 408C under photoirradiation for 5 hours. After the pho-
toirradiation, benzene (1.5 mmol) and iron powder (100 mg, 1.8 mmol)
were added into the solution, and stirred for 2 hours at 408C. After the
reaction, the sample solution was mixed with aqueous NaHCO3 under
vigorous stirring. The organic layer was then washed with water. The
sample solution was dried over anhydrous Na2SO4 and evaporated to dry-
ness to give a mixture of 1,4-dibromobenzene, 1,2,4-tribromobenzene,
and 1,2,4,5-tetrabromobenzenes in 11%, 27%, and 60% yield, respec-
tively (total weight: 520 mg).
Measurements
1H and 13C NMR spectra were recorded on a Varian INOVA 400 spec-
trometer (400 MHz for 1H nuclei and 100 MHz for 13C nuclei) or on
a Bruker AVANCE 500 spectrometer (500 MHz for H nuclei). Chemical
shifts (d) are reported in ppm with respect to tetramethylsilane or CDCl3
as the internal standard. Electronic absorption spectra were recorded on
a JASCO type V-670 UV/VIS/NIR spectrometer that was equipped with
a JASCO type ETC-717 temperature/stirring controller. IR absorption
spectra were recorded on a JASCO FT/IR-4200 Fourier transform infra-
red spectrometer. MS (FAB) was performed on a JEOL JMS-BU30 LC
Mate spectrometer with 3-nitrobenzylalcohol as the matrix. Elemental
1
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Synthesis of the Triethylamine HBr Salt
sphere 1994, 29, 1671–1682; d) H. Shirayama, Y. Tohezo, S. Taguchi,
Water Res. 2001, 35, 1941–1950; e) L. Prager, E. Hartmann, J. Pho-
A cylindrical flask (42 mm) was equipped with a 30 mm quartz-glass
jacket at the center of the flask, including a low-pressure mercury lamp,
and charged with CH2Br2 (10 mL). The solution was stirred vigorously in
a flow of O2 at 408C under photoirradiation. A solution of triethylamine
(101 mg, 1.0 mmol) in MeOH (5 mL) was bubbled with the discharged
gas flowing from the cylindrical flask for 5 hours at RT. After the reac-
tion, the sample solution was evaporated to dryness to give the HBr salt
of triethylamine as a white solid in 88% yield (160 mg).
tochem. Photobiol.
Cheng, H. Chen, G.-W. Li, T. Miao, J. Hazard. Mater. 2006, 128,
158–163.
A 2001, 138, 177–183; f) G.-M. Zuo, Z.-X.
[15] a) J. P. Simons, A. J. Yarwood, Trans. Faraday Soc. 1961, 57, 2167–
2175; b) W. S. McGivern, O. Sorkhabi, A. G. Suits, A. Derecskei-
Kovacs, S. W. North, J. Phys. Chem. A 2000, 104, 10085–10091;
c) H. Y. Huang, W. T. Chuang, R. C. Sharma, C. Y. Hsu, K. C. Lin, J.
Chem. Phys. 2004, 121, 5253–5260; d) P. Zou, J. Shu, T. J. Sears,
G. E. Hall, S. W. North, J. Phys. Chem. A 2004, 108, 1482–1488;
e) C. Romanzin, S. Boye-Peronne, D. Gauyacq, Y. Benilan, M. C.
Gazeau, S. Douin, J. Chem. Phys. 2006, 125, 114312/1–114312/9.
[16] W. S. McGivern, H. Kim, J. S. Francisco, S. W. North, J. Phys. Chem.
A 2004, 108, 7247–7252.
Acknowledgements
This work was sponsored by a Grant-in-Aid for Scientific Research (B)
(No. 22350061) from the Ministry of Education, Science, Sports, and Cul-
ture, Japan, the TEPCO Research Foundation, and a Toray Science and
Technology Grant.
[17] R. Hossaini, M. P. Chipperfield, B. M. Monge-Sanz, N. A. D. Ri-
chards, E. Atlas, D. R. Blake, Atmos. Chem. Phys. 2010, 10, 719–
735.
[18] P. H. Chen, S. D. Richardson, S. W. Krasner, G. Majetich, G. L.
Glish, Environ. Sci. Technol. 2002, 36, 3362–3371.
[19] a) P. Calza, C. Minero, A. Hiskia, E. Papacostantinou, E. Pelizzetti,
Appl. Catal. B 1999, 21, 191–202; b) C. Zhao, X. Lin, M. Kwok, X.
Guan, Y. Du, D. Wang, K. F. Hung, D. L. Phillips, Chem. Eur. J.
2005, 11, 1093–1108.
[20] R. B. Russell, O. L. Edwards, W. J. Raymonda, J. Am. Chem. Soc.
1973, 95, 2129–2133.
[21] a) R. M. Keefer, L. J. Andrews, J. Am. Chem. Soc. 1950, 72, 4677–
4681; b) D. J. Serery, D. J. Britton, Phys. Chem. 1964, 68, 2263–
2266.
[22] a) G. A. Russell, J. Am. Chem. Soc. 1957, 79, 3871–3877; b) J. A.
Howard, K. U. Ingold, J. Am. Chem. Soc. 1968, 90, 1056–1058.
[23] a) Y. Kajii, K. Obi, N. Nakashima, K. Yoshihara, J. Phys. Chem.
1987, 87, 5059–5063; b) M. E. Kurz, T. Noreuil, J. Seebauer, S.
Cook, D. Geier, A. Leeds, C. Stronach, B. Barnickel, M. Kerkemey-
er, M. Yandrasits, J. Witherspoon, F. J. Frank, J. Org. Chem. 1988,
53, 172–177; c) X. Li, W. S. Jenks, J. Am. Chem. Soc. 2000, 122,
11864–11870; d) C.-M. Tseng, Y. T. Lee, C.-K. Ni, J. Phys. Chem. A
2009, 113, 3881–3885.
[1] M. J. Dagani, H. J. Barda, T. J. Benya, D. C. Sanders, Ullmannꢀs En-
cyclopedia of Industrial Chemistry: Bromine Compounds, Wiley-
VCH, Weinheim, 2002.
[2] a) H. Eckert, B. Forster, Angew. Chem. 1987, 99, 922–923; Angew.
Chem. Int. Ed. Engl. 1987, 26, 894–895; b) P. Majer, R. S. Randad,
J. Org. Chem. 1994, 59, 1937–1938; c) S. Fuse, N. Tanabe, T. Takaha-
shi, Chem. Commun. 2011, 47, 12661–12663.
[3] a) V. Kavala, S. Naik, B. K. Patel, J. Org. Chem. 2005, 70, 4267–
4271; b) O. A. Attanasi, S. Berretta, G. Favi, P. Filippone, G. Mele,
G. Moscatelli, R. Saladino, Org. Lett. 2006, 8, 4291–4293; c) M.
Eissen, D. Leonir, Chem. Eur. J. 2008, 14, 9830–9841; d) R. Cristia-
no, K. Ma, G. Pottanat, R. G. Weiss, J. Org. Chem. 2009, 74, 9027–
9033; e) X. Jia, D. Yang, W. Wang, F. Luo, J. Cheng, J. Org. Chem.
2009, 74, 9470–9474; f) K. Kikushima, T. Moriuchi, T. Hirao, Tetra-
hedron 2010, 66, 6906–6911; g) K. Ohkubo, K. Mizushima, R. Iwata,
S. Fukuzumi, Chem. Sci. 2011, 2, 715–722.
[4] a) T. Moriuchi, M. Yamaguchi, K. Kikushima, T. Hirao, Tetrahedron
Lett. 2007, 48, 2667–2670; b) A. Tsoukala, L. Liguori, G. Occhipinti,
H. R. Bjorsvik, Tetrahedron Lett. 2009, 50, 831–833.
[24] The results will be published elsewhere.
[5] C. Djerassi, Chem. Rev. 1948, 43, 271–317.
[25] A. R. Katrizsky, O. Meth-Cohn, C. W. Wees, Organic Functional
Group Transformations 6, Elsevier, Amsterdam, The Netherlands,
1995. pp. 417–418.
[26] T. A. Ryan, C. Ryan, E. A. Seddon, K. R. Seddon, Phosgene and Re-
rated Carbonyl Halides, Elsevier, Amsterdam, The Netherlands,
1996.
[27] a) M. J. Parkington, T. A. Ryan, K. R. Seddon, J. Chem. Soc. Dalton
Trans. 1997, 251–256; b) M. J. Parkington, T. A. Ryan, K. R.
Seddon, J. Chem. Soc. Dalton Trans. 1997, 257–261.
[28] J. E. Tuttle, G. K. Rollefson, J. Am. Chem. Soc. 1941, 63, 1525–1530.
[29] a) H. Shaw, H. D. Perlmutter, C. Gu, S. D. Arco, T. O. Quibuyen, J.
Org. Chem. 1997, 62, 236–237; b) D. Kikuchi, S. Sakaguchi, Y. J.
Ishii, Org. Chem. 1998, 63, 6023–6026; c) S. Bedel, G. Ulrich, C.
[6] a) G. A. Heropoulos, G. Cravotto, C. G. Screttas, B. R. Steele, Tetra-
hedron Lett. 2007, 48, 3247–3250; b) P. K. Chhattise, A. V. Ramasw-
amy, S. B. Waghmode, Tetrahedron Lett. 2008, 49, 189–194; c) M.
Jereb, M. Zupan, S. Stavber, Helv. Chim. Acta 2009, 92, 555–566;
d) J. M. Yan, D. Qiu, F. Li, Y. Zhang, J. Wang, Angew. Chem. 2010,
122, 2072–2076; Angew. Chem. Int. Ed. 2010, 49, 2028–2032;
e) R. B. Bedford, M. F. Haddow, C. J. Mitchell, R. L. Webster,
Angew. Chem. 2011, 123, 5638–5641; Angew. Chem. Int. Ed. 2011,
50, 5524–5527; f) T. A. Salama, Z. Novak, Tetrahedron Lett. 2011,
52, 4026–4029.
[7] V. Degirmenci, D. Uner, A. Yilmaz, Catal. Today 2005, 106, 252–
255.
[8] C. Kent, Basics of Toxicology, Wiley, New York, 1998.
[9] a) A. M. Clover, J. Am. Chem. Soc. 1923, 45, 3133–3138; b) A. T.
Chapman, J. Am. Chem. Soc. 1935, 57, 419–422; c) J. W. T. Spinks,
Chem. Rev. 1940, 26, 129–139.
[10] D. D. Davis, J. F. Schmidt, C. M. Neeley, R. J. Hanrahan, J. Phys.
Chem. 1975, 79, 11–17.
[11] M. T. Vogel, S. C. Criddle, L. P. McCary, Environ. Sci. Technol. 1987,
21, 722–736.
[12] a) M. M. Kondo, W. F. Jardim, Water Res. 1991, 25, 823–827; b) M.
Halmann, A. J. Hunt, D. Spath, Sol. Energy Mater. Sol. Cells 1992,
26, 1–16; c) J. C. S. Wong, A. Linsebigler, G. Lu, J. Fan, J. T., Jr.
Yates, J. Phys. Chem. 1995, 99, 335–344; d) M.-T. Chen, C.-F. Lien,
L.-F. Liao, J.-L. Lin, J. Phys. Chem. B 2003, 107, 3837–3843.
[13] T. Alapi, A. Dombi, Chemosphere 2007, 67, 693–701.
[14] a) E. Sanhueza, I. C. Hisatsuna, J. Heicklen, Chem. Rev. 1976, 76,
801–826; b) L. A. Pruden, Ollis, J. Catal. 1983, 82, 404–417; c) R.
Gꢃrtler, U. Mçller, S. Sommer, H. Mꢃller, K. Kleinermanns, Chemo-
ˇ
Picard, Tetrahedron Lett. 2002, 43, 1697–1700; d) A. Podgorsek, S.
Stavber, M. Zupan, J. Iskra, Tetrahedron Lett. 2006, 47, 1097–1099;
ˇ
e) A. Podgorsek, S. Stavber, M. Zupan, J. Iskra, Tetrahedron 2009,
65, 4429–4439.
[30] a) S. W. Benson, J. H. Buss, J. Phys. Chem. 1957, 61, 104–109;
b) B. R. Giri, J. M. Roscoe, J. Phys. Chem. A 2009, 113, 8001–8010.
[31] a) A. Grirrane, A. Corma, H. Garcia, Science 2008, 322, 1661–1664;
b) W. Lu, C. Xi, C. G. Screttas, B. R. Steele, Tetrahedron Lett. 2008,
49, 4011–4015; c) C. Zhang, N. Jiao, Angew. Chem. 2010, 122, 6310–
6313; Angew. Chem. Int. Ed. 2010, 49, 6174–6177; d) L. Zhang, J.
Xia, Q. Li, X. Li, S. Wang, Organometallics 2011, 30, 375–378.
[32] S. Kawai, Yakugaku Zasshi 1966, 86, 1125–1132.
[33] CCDC 876076 (19Br2) contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.a-
c.uk/data_request/cif.
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&
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ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 0000, 00, 0 – 0
ÝÝ These are not the final page numbers!

Photoresponsive Molecular Storage of Elemental Br2
[34] a) T. Oberhauser, J. Org. Chem. 1997, 62, 4504–4506; b) P. Bovon-
sombat, P. Khanthapura, M. M. Krause, J. Leykajarakul, Tetrahedron
Lett. 2008, 49, 7008–7011; c) P. Bovonsombat, R. Ali, C. Khan, J.
Leykajarakul, K. Pla-on, S. Aphimanchidakul, N. Pungcharoenpong,
N. Timsuea, A. Arunrat, N. Punpongjareorn, Tetrahedron 2010, 66,
6928–6935.
[35] a) P. D. Bartlett, D. S. Tarbell, J. Am. Chem. Soc. 1936, 58, 466–474;
b) M.-F. Ruasse, J.-E. Dubois, J. Org. Chem. 1974, 39, 2441–2444;
c) G. Bellucci, C. Chiappe, F. Marioin, J. Am. Chem. Soc. 1987, 109,
515–522; d) A. R. Suarez, M. R. Mazzieri, J. Org. Chem. 1987, 52,
1145–1147; e) R. Bianchini, C. J. Chiappe, Org. Chem. 1992, 57,
6474–6478.
[41] J. B. Harborne, The Flavonoids, Advances in Research since 1986,
Chapman&Hall, London, 1994. pp. 565–588.
[42] O. M. Andersen, J. Monica, The anthocyanins, In Flavonoids,
Chemistry, Biochemistry and Applications (Eds.: O. M. Anderson,
K. R. Markham), CRC Press, Florida, 2006, pp. 471–551.
[43] K. Yoshida, M. Mori, T. Kondo, Nat. Prod. Rep. 2009, 26, 884–915
(Review).
[44] a) L. Jurd, J. Org. Chem. 1964, 29, 2602–2605; b) L. Jurd, Tetrahe-
dron 1968, 24, 4449–4457; c) G. A. Iacobucci, J. G. Sweeny, Tetrahe-
dron 1983, 39, 3005–3038; d) Y. Lu, L. Y. Foo, H. Wong, Tetrahe-
dron Lett. 2002, 43, 6621–6624; e) T. Borkowski, H. Szymusiak, A.
Gliszczynska-Swiglo, I. M. C. M. Rietjens, B. Tyrakowska, J. Agric.
Food Chem. 2005, 53, 5526–5534; f) P. Lopes, T. Richard, C. Saucier,
P.-L. Teissedre, J.-P. Monti, Y. Glories, J. Agric. Food Chem. 2007,
55, 2698–2704.
[36] a) K. Tanemura, T. Suzuki, Y. Nishida, K. Satsumabayashi, T. Hora-
guchi, Chem. Lett. 2003, 32, 932–933; b) D. Qlu, F. Mo, Z. Zheng,
Y. Zhang, J. Wang, Org. Lett. 2010, 12, 5474–5477.
[37] C. Bolm, J. Legros, J. Le Paih, L. Zani, Chem. Rev. 2004, 104, 6217–
6254.
[45] a) P. S. Monks, F. L. Nesbitt, M. Scanlon, L. J. Stief, J. Phys. Chem.
1993, 97, 11699–11705; b) R. J. Barnes, M. Lock, J. Coleman, A.
Sinha, J. Phys. Chem. 1996, 100, 453–457; c) P. A. Denis, J. Phys.
Chem. A 2006, 110, 5887–5892.
[46] J. L. Sessler, M. R. Johnson, S. E. Creager, J. C. Fettinger, J. A.
Ibers, J. Am. Chem. Soc. 1990, 112, 9310–9329.
[38] a) J. Wu, M. D. Watson, K. Mꢃllen, Angew. Chem. 2003, 115, 5487–
5491; Angew. Chem. Int. Ed. 2003, 42, 5329–5333; b) R. Rathore,
C. L. Burns, I. A. Guzei, J. Org. Chem. 2004, 69, 1524–1530; c) S.
Lei, V. Heyen, S. D. Feyter, M. Surin, R. Lazzaroni, S. Rosenfeldt,
M. Ballauff, P. Lindner, D. Mossinger, S. Hoger, Chem. Eur. J. 2009,
15, 2518–2535.
[47] A. D. Adler, F. R. Longo, J. D. Finarelli, J. Goldmacher, J. Assour,
L. Korsakoff, J. Org. Chem. 1964, 17, 1028.
[39] a) B. Chen, S. Wo, A. Li, F. Liang, X. Zhou, X. Cao, Z. He, Tetrahe-
dron 2006, 62, 5487–5497; b) J. Pellegrino, S. E. Bari, D. E. Bikiel, F.
Doctorovich, J. Am. Chem. Soc. 2010, 132, 989–995.
[48] G. M. Sheldrick, SHELXTL 5.10 for Windows NT: Structure Deter-
mination Software Programs, Bruker Analytical X-ray Systems, Inc.,
Madison, WI, 1997.
[40] a) H. Yamasaki, H. Uefuji, Y. Sakihama, Arch. Biochem. Biophys.
1996, 332, 183–186; b) T. Ichiyanagi, Y. Hatano, S. Matsuo, T. Ko-
nishi, Chem. Pharm. Bull. 2004, 52, 434–438; c) T. Ichiyanagi, Y.
Hatano, S. Matsuo, T. Konishi, Chem. Pharm. Bull. 2004, 52, 1312–
1315.
Received: April 11, 2012
Revised: April 20, 2012
Published online: && &&, 0000
Chem. Asian J. 2012, 00, 0 – 0
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FULL PAPER
Photochemistry
The generation of Br2 from bromi-
nated methanes occurred upon photo-
irradiation under O2. The solutions
that contained elemental Br2 were
useful for the synthesis of organobro-
mine compounds and the macroscopic
photochemical bleaching of colored
plants.
Kazumitsu Kawakami,
Akihiko Tsuda*
&&&& — &&&&
Brominated Methanes as Photorespon-
sive Molecular Storage of Elemental
Br2
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ÝÝ These are not the final page numbers!