Novel photoreaction using diphenyl disulfide derivatives: Photoinduced oxidation of allyl alcohol

Article abstract of DOI:10.1246/bcsj.81.361

Allyl alcohols are oxidized to acrylaldehydes using diphenyl disulfide derivatives upon photoirradiation. The reaction occurs via α-hydrogen abstraction by a sulfanyl radical. Interestingly, the oxidation reaction occurs in moderate yield when a dendrimer disulfide is used as a mediator.

Full text of DOI:10.1246/bcsj.81.361

Ó 2008 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 81, No. 3, 361–368 (2008)
361
Novel Photoreaction Using Diphenyl Disulfide Derivatives:
Photoinduced Oxidation of Allyl Alcohol
ꢀ
Takaaki Tsuboi, Yutaka Takaguchi, and Sadao Tsuboi
Graduate School of Environmental Science, Okayama University, 3-1-1 Tsushima-Naka, Okayama 700-8530
Received July 27, 2007; E-mail: yutaka@cc.okayama-u.ac.jp
Allyl alcohols are oxidized to acrylaldehydes using diphenyl disulfide derivatives upon photoirradiation. The
reaction occurs via ꢀ-hydrogen abstraction by a sulfanyl radical. Interestingly, the oxidation reaction occurs in moderate
yield when a dendrimer disulfide is used as a mediator.
Photoreactivity of diphenyl disulfide derivatives has attract-
ed scientific attention in the past few decades. Sulfanyl radicals
generated by homolytic cleavage of the S–S bond play impor-
tant roles in photoinitiated reactions such as sulfenylation of
aryl halides1a and hindered phenols,1b and vinyl polymeriza-
tion.2 Ogawa and Sonoda reported that a binary system of or-
ganic dichalcogenides, i.e., a (PhS)2–(PhSe)2 system, provides
the desired vicinal dichalcogenation of carbon–carbon unsatu-
rated compounds3a–3c and double chalcogenation of isocya-
nides3d under photoirradiation. However, transformation of
functional groups using photoreaction of disulfide is quite
rare.4 Meanwhile, dendrimers containing a photoreactive core
have garnered considerable interest in the fields of material
science and synthetic organic chemistry. In particular, there
is an increasing emphasis on developing applications for den-
drimer disulfide because of various interesting features in su-
pramolecular chemistry,5 host–guest chemistry,6 stabilization
of highly reactive species,7 and material science.8 Recently,
we reported that a photoaddition reaction of C60 with a poly-
(amidoamine) dendrimer disulfide, of which the core is di-
phenyl disulfide, gave a new fullerodendrimer having fuller-
ene–sulfur bonds as a linkage.9 During our studies on dendri-
mer effects of dendrimer disulfides, we found a novel reaction
of diphenyl disulfide derivatives, i.e., allyl alcohols were con-
verted into acrylaldehydes in the presence of diphenyl disulfide
derivatives upon photoirradiation. In this paper, we describe
that diphenyl disulfide derivatives mediate oxidation of various
allyl alcohols to give acrylaldehydes upon photoirradiation. In
particular, an effective oxidation of allyl alcohol was accom-
plished by the use of dendrimer disulfides.
We carried out the same reaction in the presence of various
diphenyl disulfide derivatives to obtain mechanistic insights
into this oxidation (Table 1). Bis(p-nitrophenyl) disulfide (2e)
was difficult to dissolve in benzene; instead, chloroform was
used as the solvent in Entry 5. The use of diphenyl disulfides
having electron-withdrawing substituents resulted in moderate
yields of products (Entries 2–5). On the other hand, the use of
bis(p-methoxyphenyl) disulfide (2f), an electron-rich disulfide,
Table 1. Oxidation of 3-Methyl-2-buten-1-ol (1a) Using
Photolysis of Diphenyl Disulfide Derivatives
disulfide (1.0 mol. amt.)
CHO
OH
benzene, hν, r.t.
1a
3a
Conversion YieldaÞ
Entry
1
Disulfide
Time
/%
/%
S
80 min
63
23
2
2a
MeOOC
Cl
S
2
3
30 min
1 h
45
58
31
44
2
2b
2c
S
2
CF3
S
4
30 min
85
37
Results and Discussion
2
2d
2e
A benzene solution of 3-methyl-2-buten-1-ol (1a) in the
presence of diphenyl disulfide (2a) was irradiated with a high-
pressure mercury lamp (ꢁ > 300 nm) through a Pyrex filter at
room temperature under a nitrogen atmosphere for 80 min to
give 3-methyl-2-butenal (3a) in 23% yield. Reactions in the
dark or in the absence of diphenyl disulfide (2a) did not pro-
ceed. Complex mixtures were obtained when oxygen was
passed through the reaction mixture during the reaction. These
results indicate that oxidation of allyl alcohol 1a is a photore-
action mediated by diphenyl disulfide (2a).
O2N
S
5bÞ
1 h
48
56
30
2
MeO
S
6
2.5 h
trace
2
2f
a) GC yield (based on consumed starting material). b) CHCl3
was used as a solvent.
Published on the web March 13, 2008; doi:10.1246/bcsj.81.361

362 Bull. Chem. Soc. Jpn. Vol. 81, No. 3 (2008)
Photoreactivity of Diphenyl Disulfide
Table 2. Oxidation of Allyl Alcohols Using Photolysis of Disulfide 2b
R1 R3
R1
R3
disulfide 2b (1.0 mol. amt.)
R2
Entry Allyl alcohol
OH
R2
O
benzene, hν, r.t.
Time
Conversion/%
45aÞ
Product
CHO
Yield/%
1
30 min
30 min
31aÞ
OH
OH
3a
1a
1b
CHO
2bÞ
37cÞ
28cÞ
7cÞ
3b
Cl
Cl
3bÞ
2 h
35cÞ (E=Z ¼ 57=43)d),e)
CHO
O
OH
OH
OH
3c
3d
1c
1d
1e
4
5
30 min
20 min
53aÞ
47aÞ
25aÞ
—
a) GC yield (based on consumed starting material). b) CDCl3 was used as a solvent.
c) NMR yield (based on consumed starting material). d) E=Z Ratio was determined by
1H NMR. e) Starting allyl alcohol 1c was recovered in 72%cÞ, E=Z ¼ 54=46dÞ.
h
ν
PhS-SPh
2 PhS
SPh
H
R3
R3
R3
R1
R2
OH
R1
OH
R1
R2
OH
SPh
R2
PhSH
(SET)
R3
R3
H
R3
H
R1
R2
O
R1
R2
O
R1
R2
O
SPh
PhSH
Scheme 1. Plausible mechanism of oxidation of allyl alcohol using photolysis of diphenyl disulfide.
gave trace product (Entry 6). Various allyl alcohols were also
(Entry 4). The reaction of tertiary alcohol 1e gave no oxidized
product (Entry 5). These results show that the ꢀ-hydrogen of
the alcohol is necessary to cause oxidation. In all cases of
the above reactions, thiols corresponding to disulfides were ob-
tained. For example, oxidation of 3-methyl-2-buten-1-ol (1a)
using diphenyl disulfide (2a) gave thiophenol and unchanged
diphenyl disulfide (2a) in 23% and 54% yield, respectively.
Based on the results described above, a plausible mech-
anism is proposed in Scheme 1. The reaction is triggered by
the sulfanyl radical generated by photolysis of the diphenyl di-
sulfide. Then, the abstraction of an ꢀ-hydrogen, which occurs
from the allyl alcohol to the sulfanyl radical, produces the
employed for oxidation using bis(p-methoxycarbonylphenyl)
disulfide (2b) (Table 2). Reaction of allyl alcohol having no
substituent (1b) on the terminal olefin gave low yield of prod-
uct 3b (Entry 2). Although longer reaction time was required,
oxidation of (Z)-3-chloro-2-propenol (1c) gave product 3c in
almost the same yield as the oxidation of allyl alcohol 1a
(Entry 3). The E–Z isomerization of recovered allyl alcohol
1c (E=Z = 54:46) and product 3c (E=Z = 57:43) indicates
that carbon-centered radical intermediate might be formed in
this reaction. The use of secondary alcohol 1d afforded prod-
uct 3d in lower yield than the use of primary alcohol 1a

T. Tsuboi et al.
Bull. Chem. Soc. Jpn. Vol. 81, No. 3 (2008)
363
allylic radical and thiophenol. It is noteworthy that only a
few reactions involving hydrogen abstraction by a sulfanyl
radical have been reported.4 Next, a single electron transfer
(SET) occurs from the allylic radical to another sulfanyl radi-
cal, and an allylic cation is formed. Employing diphenyl di-
sulfides 2b–2e having electron-withdrawing substituent result-
ed in moderate yields, in marked contrast with the reaction by
the use of electron-rich disulfide 2f. Meanwhile, the reaction
efficiency of allyl alcohol 1c having electron-withdrawing
chlorine group is quite low compared to 1a, which has elec-
tron-donating methyl groups. These results might suggest that
sulfanyl radical (or diphenyl disulfide) acts as an electron
acceptor during the SET process. The thiolate anion, which is
generated by SET, abstracts the proton of alcohol to give the
oxidized product and thiophenol. However, the exact reaction
mechanism is not completely clear. Efforts to obtain a better
understanding of the reaction mechanism are in progress.
This oxidation gave only 23–44% yield of products. Poly-
merization of allyl alcohols initiated by the carbon-centered
radical generated from the addition reaction of sulfanyl radical
to the olefin probably causes decreased yield of the products.
Gel permeation chromatography (GPC) analysis of the reac-
tion mixture of 3-methyl-2-buten-1-ol (1a) and bis(2-trifluoro-
methylphenyl) disulfide (2d) showed several peaks in the high-
molecular-weight region. Furthermore, trace amount of by-
product, which might be formed by the addition reaction of
disulfide or thiol to the olefins, were observed by GC analysis.
To decrease the rate of side reactions triggered by the addition
of sulfanyl radical to unsaturated bonds, diphenyl disulfide
having bulky substituents might be expected to be effective.
Okazaki and Goto reported a stable aromatic S-nitrosothiol
bearing a dendrimer steric protection group.10 This protection
group suppresses oxidative dimerization of the S-nitrosothiol
without diminution of reactivity of the S-nitrosothiol core
towards appropriate molecules such as thiols or alcohols. This
result prompted us to investigate oxidation using dendrimer
disulfides 46 (Chart 1) or 5.
Dendrimer 5 was synthesized as shown in Scheme 2. A
known compound 7 was selected as the starting material,
which was prepared according to the literature.11 Compound 7
was treated with NaOH in methanol under reflux for 1 day,
and then acidified with HCl to obtain 5-sulfanylisophthalic
acid (8). Fischer esterification of isophthalic acid 8 with meth-
O
MeO
N
O
O
O
NH
O
S
OMe
OMe
MeO
S
HN
O
N
4
Chart 1.
O
O
O
1) NaOH (6 mol. amt.),
MeOH, reflux, 1 day
HO
HO
MeO
MeO
MeO
O
S
MeOH, H2SO4
NMe2
SH
SH
2) HCl aq
CHCl3, reflux,
13 h
MeO
O
O
O
7
8
9
NH2
H2N
NH2
O
O
O
H2N
O
NH
O
OMe
OMe
I2 (1 mol. amt.),
Et3N
HN
MeO
(400 mol. amt.)
S
S
S
S
MeOH, r.t.
12 h
CHCl3, r.t., 3.5 h
NH
HN
O
MeO
O
NH2
O
6
H2N
10
O
MeO
O
N
OMe
N
O
O
O
O
NH
NH
OMe
O
O
OMe
MeO
HN
HN
(80 mol. amt.)
S
S
MeOH, 45 °C,
4 days
OMe
O
O
MeO
O
N
O
N
O
MeO
OMe
5
Scheme 2. Synthesis of dendrimer disulfide 5.

364 Bull. Chem. Soc. Jpn. Vol. 81, No. 3 (2008)
Photoreactivity of Diphenyl Disulfide
Table 4. Oxidation of Cinnamyl Alcohol (11)
Table 3. Oxidation of 3-Methyl-2-buten-1-ol (1a) Using
Photolysis of Dendrimer Disulfides
CHO
disulfide (1.0 mol. amt.)
OH
disulfide (1.0 mol. amt.)
CHO
benzene, hν, r.t.
OH
11
12
Time Conversion/% YieldaÞ/%
benzene, hν, r.t.
1a
3a
Time/h Conversion/% YieldaÞ/%
Entry
1
Disulfide
Entry
1
Disulfide
S
2a
70 min
52
44
(E=Z > 95=5)bÞ
S
2
2a
2
1
63
23
2
3
Dendrimer 4
Dendrimer 5
2.5
2.5
59
58
63
51
2
3
Dendrimer 4
Dendrimer 5
2.5 h
2.5 h
54
42
58
(E=Z > 95=5)bÞ
46
a) GC yield (based on consumed starting material).
(E=Z > 95=5)bÞ
a) Isolated yield (based on consumed starting material).
1
b) E=Z Ratio was determined by H NMR.
CHO
dendrimer 5
(1.0 mol. amt.)
14 (38%, E/Z = 62/38) a), b)
+
OH
benzene, h
ν
13
r.t., 2.5 h
CHO
15 (54%) a)
a) Isolated yield (based on consumed starting material). b) E/Z Ratio was
determined by 1H NMR.
Scheme 3. Oxidation of geraniol (13).
anol under reflux for 13 h gave dimethyl 5-sulfanylisophthalate
(9). Thiol 9 was oxidized with I2 in the presence of triethyl-
amine at room temperature for 3.5 h to afford bis(3,5-methoxy-
carbonylphenyl) disulfide (6) (58% yield, 3 steps). The treat-
ment of disulfide 6 with ethylenediamine produced the core
of dendrimer 10. Subsequently, 10 was allowed to react with
methyl acrylate to give a dendrimer disulfide 5 (33%, two
steps).
We then carried out oxidation of 3-methyl-2-buten-1-ol (1a)
in the presence of dendrimer disulfides 4 or 5 (Table 3). Their
use gave product 3a in much better yields (63% or 51%) than
by the use of diphenyl disulfide (2a) (23%), although the
conversions of allyl alcohol 1a were almost the same. This
result indicated that the bulky dendritic substituent might in-
hibit side reactions. Dendrimer disulfides were also effective
for oxidation of other allyl alcohols, such as cinnamyl alcohol
(11) (Table 4). Oxidation of cinnamyl alcohol (11) in the pres-
ence of dendrimer disulfides 4 or 5 gave cinnamaldehyde (12)
in 58% or 46% yields, respectively. On the other hand, the use
of diphenyl disulfide (2a) afforded product 12 in 44% yield.
Furthermore, oxidation of geraniol (13) in the presence of
dendrimer disulfide 5 gave citral (14) and 3,7-dimethyl-6-
octenal (citronellal, 15) in 38% and 54% yields (Scheme 3),
respectively. The total amount of oxidation products, alde-
hydes 14 and 15, reached 92% yield. This result might indicate
that the polymerization initiated by the intermediate carbon-
centered radical might be suppressed by the use of a bulky
allyl alcohol. Although the reaction mechanism is not clear,
citronellal (15) might be formed by reduction of citral (14).
We followed the time course of this reaction by NMR and ob-
served that citronellal (15) was not formed until 20 min after
the start of the reaction. Furthermore, we confirmed that photo-
reaction of (E)-citral (16) in the presence of dendron thiol 17
gave citronellal (15) in 8% yield (Scheme 4).
Absorption maximums (ꢁmax) and molar extinction coeffi-
cients (") of disulfides 2a, 4, and 5 are displayed in Table 5.
All three disulfides gave the same absorption maximum at
276 nm and similar values of molar extinction coefficients.
However, oxidations by the use of dendrimer disulfides 4 and
5 gave products in better yields than by the use of diphenyl di-
sulfide (2a). Hence, the difference in reactivity between den-
dritic disulfide and nonsubstituted diphenyl disulfide might
arise from not photoexcitation but the following reactions,
which can be affected by the bulky dendritic substituent.
Conclusion
These results described herein show the first example of ox-
idation of allyl alcohol mediated by diphenyl disulfide deriva-
tives upon photoirradiation. Since dendritic substituents were
quite effective to inhibit unwanted side reactions of the inter-
mediates, dendrimer disulfide was found to be a good mediator
of this oxidation reaction. Further work is in progress to ex-
plore the application and advantages of photoreactivities of
dendrimer disulfides.

T. Tsuboi et al.
Bull. Chem. Soc. Jpn. Vol. 81, No. 3 (2008)
365
O
O
MeO
MeO
N
NH
O
SH
17 (2.0 mol. amt.)
CHO
CHO
15 (8%)
16
benzene, hν, r.t., 12 h
Scheme 4. Photoirradiation of (E)-citral (16) in the presence of dendron thiol 17.
Table 5. Absorption Data for Diphenyl Disulfide Deriva-
tives
Preparation of 2,4-Dimethyl-3-penten-2-ol (1e). A solution
of 4-methyl-3-penten-2-one (3d) (1.00 g, 10.2 mmol) in Et2O
(20 mL) was added dropwise to a stirred solution of 0.93 M methyl
magnesium bromide in THF (32.9 mL, 30.6 mmol) diluted with
Et2O (50 mL). After stirring at room temperature for 1 h, aqueous
saturated NH4Cl (30 mL) was added. The mixture was extracted
with Et2O, dried over MgSO4, and the solvent evaporated under
ice cooling. The residue was distilled to afford 2,5-dimethyl-3-
penten-2-ol (1e) (0.49 g, 4.29 mmol), bp 42 ꢂC (13 mmHg), as a
colorless liquid in 42% yield, with spectral data being identical
to that of an authentic sample:12 1H NMR (300 MHz, CDCl3) ꢂ
1.36 (s, 6H), 1.70 (s, 3H), 1.85 (s, 3H), 5.33 (s, 1H).
Preparation of Bis(4-methoxycarbonylphenyl) Disulfide
(2b). Sulfuric acid (1.6 mL) was added dropwise to a mixture
of 4-sulfanylbenzoic acid (1.60 g, 10.4 mmol), methanol (2.52 mL,
62.2 mmol), and chloroform (6.4 mL). After stirring at 75 ꢂC for
13 h, the solution was extracted with chloroform. The organic
layer was washed with aqueous saturated NaHCO3, dried over
MgSO4, and the solvent evaporated to afford methyl 4-sulfanyl-
benzoate as a yellow solid in 86% yield: 1H NMR (300 MHz,
CDCl3) ꢂ 3.63 (s, 1H), 3.67 (s, 3H), 7.04 (d, J ¼ 8:4 Hz, 2H), 7.63
(d, J ¼ 8:4 Hz, 2H).
Disulfide
ꢁ
max/nmaÞ
"
max/Mꢃ1 cmꢃ1 aÞ
Dendrimer 4
Dendrimer 5
276
276
1:66 ꢁ 104
5:69 ꢁ 103
2a
S
2
276
2:86 ꢁ 103
a) In benzene.
Experimental
Melting points (mp) were determined using a Mel-Temp II
melting point apparatus, Laboratory Devices Inc., and are uncor-
rected. The NMR spectra were measured using a JEOL AL300
spectrometer. The IR and IR-attenuated total reflection (ATR)
spectra were recorded on an Avatar 360T2 spectrometer, Thermo
Nicolet Japan Inc. Matrix-assisted laser desorption ionization
time-of-flight mass spectroscopy (MALDI-TOF-MS) was per-
formed on an Autoflex mass spectrometer, Bruker Daltonics
Inc. Elemental analysis was carried out using a 2400 Series II
CHNS/O elemental analyzer, Perkin-Elmer Inc. The GPC experi-
ments were performed on an appropriate device (LC-918V; Japan
Analytical Industry Co.) using JAIGEL 1H, 2H columns. Chloro-
form was used as the eluting solvent. Gas chromatography (GC)
analyses were carried out on a GC18A gas chromatograph,
Shimadzu Corp., equipped with an FID detector and a fused silica
capillary column (30 m ꢁ 0.53 mm i.d., coating DB-1; J&W Sci-
entific Inc.). The GC-MS analyses were performed on a GC-MS
workstation (QP5000; Shimadzu Corp.) with a fused silica capil-
lary column (30 m ꢁ 0.25 mm i.d., coating TC-5; GL Science Co.,
Ltd.). Photoirradiation was carried out using a Pyrex reactor. Prior
to irradiation, solvents were degassed with nitrogen for 30 min. A
500-W high-pressure mercury lamp (EHB-500; Eikosha Corp.)
was used as the light source. Unless otherwise noted, the reagents
were obtained from Wako Pure Chemical Industries Ltd., Tokyo
Kasei Kogyo Co., Ltd., Kanto Kagaku, or Aldrich Chemical
Co., Inc. The Et2O used in reactions was further purified using
general methods. Other solvents and reagents were used as re-
ceived without further purification. Dendrimer 4 was synthesized
according to a previously reported method.6 Compound 7 was
prepared using a method reported by Portnoy et al.11
Solutions of methyl 4-sulfanylbenzoate (1.40 g, 8.33 mmol) in
chloroform (20 mL) and iodine (1.58 g, 6.24 mmol) in chloroform
(50 mL) were added separately and simultaneously over 1 h to a
vigorously stirred solution of triethylamine (1.74 mL, 12.49 mmol)
in chloroform (20 mL). After stirring at room temperature for
1.5 h, the solution was washed with aqueous saturated Na2S2O3,
dried over MgSO4, and the solvent evaporated. The residue was
purified by silica-gel column chromatography (eluent, chloroform)
and recrystallization from benzene–ethanol (1:1) to afford bis(4-
methoxycarbonylphenyl) disulfide (2b) (1.14 g, 3.36 mmol) as a
white crystalline solid in 81% yield, spectral data being identical
to that of an authentic sample:13 1H NMR (300 MHz, CDCl3) ꢂ
3.90 (s, 6H), 7.53 (d, J ¼ 8:8 Hz, 4H), 7.97 (d, J ¼ 8:6 Hz, 4H).
Preparation of Bis(2-trifluoromethylphenyl) Disulfide (2d).
Solutions of o-trifluoromethylbenzenethiol (0.54 g, 3.03 mmol)
in chloroform (10 mL) and iodine (0.58 g, 2.27 mmol) in chloro-
form (20 mL) were added separately and simultaneously over
1 h to a vigorously stirred solution of triethylamine (0.63 mL,
4.55 mmol) in chloroform (10 mL). After stirring at room temper-
ature for 4 h, the solution was washed with aqueous saturated
Na2S2O3, dried over MgSO4, and the solvent evaporated. The
residue was purified by silica-gel column chromatography (eluent,
chloroform/hexane = 1/4) and recrystallized from methanol to
afford bis(2-trifluoromethylphenyl) disulfide (2d) (0.26 g, 0.73
mmol) as pale yellow plates in 48% yield, with spectral data being
For comparison of reaction rates, the conversion of allyl alco-
hol was set between ca. 40–60%. In the case of the reaction
using bis(2-trifluoromethylphenyl) disulfide (2d), allyl alcohol
was rapidly consumed.

366 Bull. Chem. Soc. Jpn. Vol. 81, No. 3 (2008)
Photoreactivity of Diphenyl Disulfide
identical to that of an authentic sample:14 mp 60 ꢂC (lit. 62 ꢂC);
1H NMR (300 MHz, CDCl3) ꢂ 7.33 (t, J ¼ 7:5 Hz, 1H), 7.49 (t,
J ¼ 7:4 Hz, 3H), 7.64 (d, J ¼ 7:5 Hz, 3H), 7.84 (d, J ¼ 7:8 Hz,
1H); 13C NMR (75 MHz, CDCl3) ꢂ 121.8, 125.4, 126.6, 126.7,
127.1, 129.5, 132.5.
Preparation of Bis(4-nitrophenyl) Disulfide (2e). Solutions
of p-nitrobenzenethiol (1.00 g, 6.44 mmol) in chloroform (25 mL)
and iodine (1.63 g, 6.44 mmol) in chloroform (40 mL) were added
separately and simultaneously over 1 h to a vigorously stirred
solution of triethylamine (1.35 mL, 9.66 mmol) in chloroform
(25 mL). After stirring at room temperature for 4 h, the solution
was washed with aqueous saturated Na2S2O3, dried over MgSO4,
and the solvent evaporated. The residue was washed with meth-
anol to afford bis(4-nitrophenyl) disulfide (2e) (0.74 g, 2.40 mmol)
as a yellow powder in 37% yield, with spectral data identical to
that of an authentic sample:15 1H NMR (300 MHz, CDCl3) ꢂ 7.62
(d, J ¼ 9:6 Hz, 4H), 8.20 (d, J ¼ 9:6 Hz, 4H).
O8S2: C, 53.32; H, 4.05%.
Preparation of Dendrimer Disulfide 5. A suspension of 6
(620 mg, 1.38 mmol) in methanol (37 mL) was added dropwise
to ethylenediamine (37.3 mL, 558 mmol) under ice-cooling. The
mixture was stirred at room temperature for 12 h. After removal
of the solvent under reduced pressure at 45 ꢂC, the residue was
reprecipitated from a methanol–ether solution to obtain dendrimer
disulfide 10, which was used for the following reaction without
further purification.
A mixture of 10, methyl acrylate (9.94 mL, 110 mmol) and
methanol (30 mL) was stirred at 45 ꢂC for 4 days. After removal
of the solvent, the residue was purified by silica-gel column chro-
matography (eluent, chloroform/methanol = 30/1) and GPC with
chloroform as eluent to afford the dendrimer disulfide 5 (560 mg,
0.45 mmol) as a thick yellow oil in 33% yield: 1H NMR (300
MHz, CDCl3) ꢂ 2.44 (t, J ¼ 6:5 Hz, 8H), 2.65 (t, J ¼ 5:7 Hz,
4H), 2.77 (t, J ¼ 6:5 Hz, 8H), 3.54 (q, J ¼ 5:7 Hz, 4H), 3.57 (s,
12H), 7.44 (t, J ¼ 5:3 Hz, 2H), 8.16 (s, 1H), 8.22 (s, 2H);
13C NMR (75 MHz, CDCl3) ꢂ 32.4, 37.7, 48.9, 51.6, 52.6, 124.7,
129.6, 135.9, 137.7, 165.8, 173.1; ATR (neet) 1732, 1660, 1529,
1437 cmꢃ1. MALDI-TOF-MS (matrix, dithranol): m=z 1251.51
(½M þ Hꢄþ). Calcd for C56H82N8O20S2: m=z 1252.43.
Preparation of Bis(4-methoxyphenyl) Disulfide (2f). Solu-
tions of p-methoxybenzenethiol (1.00 g, 7.13 mmol) in chloroform
(25 mL) and iodine (1.81 g, 7.13 mmol) in chloroform (40 mL)
were added separately and simultaneously over 1 h to a vigorously
stirred solution of triethylamine (1.49 mL, 10.7 mmol) in chloro-
form (25 mL). After stirring at room temperature for 1.5 h, the
solution was washed with aqueous saturated Na2S2O3, dried over
MgSO4, and the solvent evaporated. The residue was purified by
silica-gel column chromatography (eluent, chloroform/hexane =
7/1) to afford bis(4-methoxyphenyl) disulfide (2f) (0.94 g, 3.38
mmol) as a yellow liquid in 95% yield, spectral data being
identical to that of an authentic sample:15 1H NMR (300 MHz,
CDCl3) ꢂ 3.79 (s, 3H), 6.83 (d, J ¼ 9:0 Hz, 2H), 7.40 (d, J ¼
8:2 Hz, 1H).
Preparation of Bis(3,5-methoxycarbonylphenyl) Disulfide
(6). Dimethyl 5-(dimethylcarbamoylthio) isophthalate (7) (1.32
g, 4.44 mmol) was added a 1 M solution (27 mL) of NaOH in
methanol. After stirring at 75 ꢂC for 19 h, the solution was cooled,
diluted with ice water (160 mL), and acidified with 6 M HCl
(44 mL). The yellow precipitate was filtered and dried to obtain
the crude product of 5-sulfanylisophthalic acid (8) (0.72 g) as a
yellow powder, which was used for the following reaction without
further purification.
Sulfuric acid (1 mL) was added dropwise to a mixture of 8,
methanol (1.76 mL, 43.6 mmol) and chloroform (5.3 mL). After
stirring at 75 ꢂC for 13 h, the solution was extracted with chloro-
form. The organic layer was washed with aqueous saturated
NaHCO3, dried over MgSO4, and the solvent evaporated to afford
crude dimethyl 5-sulfanylisophthalate (9) (0.71 g) as a pale yellow
solid, which was used for the following reaction without further
purification.
Solutions of 9 (710 mg, 3.14 mmol) in chloroform (25 mL) and
iodine (800 mg, 3.14 mmol) in chloroform (40 mL) were added
separately and simultaneously over 1 h to a vigorously stirred
solution of triethylamine (0.66 mL, 4.71 mmol) in chloroform
(25 mL). After stirring at room temperature for 3.5 h, the solution
was washed with aqueous saturated Na2S2O3, dried over MgSO4,
and the solvent evaporated. The residue was purified by silica-gel
column chromatography (eluent, chloroform) and recrystallized
from benzene–ethanol (1:2) to afford bis(3,5-methoxycarbonyl-
phenyl) disulfide (6) (580 mg, 1.29 mmol) as a white crystalline
solid in 58% yield: mp 156 ꢂC; 1H NMR (300 MHz, CDCl3) ꢂ 3.94
(s, 6H), 8.34 (s, 2H), 8.53 (s, 1H); 13C NMR (75 MHz, CDCl3) ꢂ
52.5, 129.7, 131.7, 132.6, 137.8, 165.3; IR (KBr) 1724, 1586,
1436 cmꢃ1. Anal. Found: C, 53.16; H, 4.07%. Calcd for C20H18-
Preparation of Dendron Thiol 17. NaBH4 (61.6 mg, 1.6
mmol) was added to a solution of dendrimer disulfide 4 (399 mg,
0.54 mmol) in ethanol (5.4 mL) at room temperature under Ar
atmosphere. After stirring for 2 h, water was added. The mixture
was extracted with chloroform. The organic layer was washed
with brine, dried over MgSO4, and the solvent evaporated to af-
ford the dendron thiol 17 (367 mg, 1.00 mmol) as a thick yellow
oil in 92% yield: 1H NMR (300 MHz, CDCl3) ꢂ 2.44 (t, J ¼
6:3 Hz, 4H), 2.62 (t, J ¼ 5:6 Hz, 2H), 2.75 (t, J ¼ 6:3 Hz, 4H),
3.51–3.57 (m, 9H), 7.21 (brs, 1H), 7.28 (d, J ¼ 8:1 Hz, 2H),
7.77 (d, J ¼ 8:4 Hz, 2H); 13C NMR (75 MHz, CDCl3) ꢂ 32.3,
37.0, 48.6, 51.2, 52.5, 127.7, 128.0, 131.5, 135.4, 166.3, 172.9;
MALDI-TOF-MS (matrix, ꢀ-cyano-4-hydroxycinnamic acid):
m=z 368.91 (½M þ Hꢄþ). Calcd for C17H24N2O5S: m=z 369.15.
Photoirradiation of a 3-Methyl-2-buten-1-ol (1a) and Di-
phenyl Disulfide (2a) Mixture. A mixture of 3-methyl-2-butene-
1-ol (1a) (16 mg, 0.19 mmol) and diphenyl disulfide (2a) (41 mg,
0.19 mmol) in benzene (3.2 mL) was irradiated with a high-pres-
sure mercury lamp for 80 min at room temperature. The resulting
mixture was analyzed by GC. Decane was used as the internal
standard.
Photoirradiation of a 3-Methyl-2-buten-1-ol (1a) and Bis(4-
methoxycarbonylphenyl) Disulfide (2b) Mixture. A mixture of
3-methyl-2-buten-1-ol (1a) (16mg, 0.19 mmol) and bis(4-methoxy-
carbonylphenyl) disulfide (2b) (64 mg, 0.19 mmol) in benzene
(3.2 mL) was irradiated with a high-pressure mercury lamp for
30 min at room temperature. The resulting mixture was analyzed
by GC. Decane was used as the internal standard.
Photoirradiation of a 3-Methyl-2-buten-1-ol (1a) and Bis(4-
chlorophenyl) Disulfide (2c) Mixture. A mixture of 3-methyl-2-
buten-1-ol (1a) (16 mg, 0.19 mmol) and bis(4-chlorophenyl) disul-
fide (2c) (53 mg, 0.19 mmol) in benzene (3.2 mL) was irradiated
with a high-pressure mercury lamp for 1 h at room temperature.
The resulting mixture was analyzed by GC. Decane was used as
the internal standard.
Photoirradiation of a 3-Methyl-2-buten-1-ol (1a) and Bis(2-
trifluoromethylphenyl) Disulfide (2d) Mixture. A mixture of 3-
methyl-2-buten-1-ol (1a) (16 mg, 0.19 mmol) and bis(2-trifluoro-
methylphenyl) disulfide (2d) (67 mg, 0.19 mmol) in benzene
(3.2 mL) was irradiated with a high-pressure mercury lamp for

T. Tsuboi et al.
Bull. Chem. Soc. Jpn. Vol. 81, No. 3 (2008)
367
30 min at room temperature. The resulting mixture was analyzed
by GC. Decane was used as the internal standard.
(25 mg, 0.19 mmol) and diphenyl disulfide (2a) (41 mg, 0.19
mmol) in benzene (3.2 mL) was irradiated with a high-pressure
mercury lamp for 70 min at room temperature. After removal of
the solvent, the resulting mixture was purified by silica-gel col-
umn chromatography (eluent, chloroform/hexane = 2/1) to
afford cinnamaldehyde (12) (5.8 mg, 0.044 mmol) in 44% yield
(based on consumed starting material).
Photoirradiation of a 3-Methyl-2-buten-1-ol (1a) and Bis(4-
nitrophenyl) Disulfide (2e) Mixture. A mixture of 3-methyl-2-
buten-1-ol (1a) (15 mg, 0.18 mmol) and bis(4-nitrophenyl) disul-
fide (2e) (56 mg, 0.18 mmol) in chloroform (3.0 mL) was irradiat-
ed with a high-pressure mercury lamp for 1 h at room temperature.
The resulting mixture was analyzed by GC. Decane was used as
the internal standard.
Photoirradiation of a 3-Methyl-2-buten-1-ol (1a) and Bis(4-
methoxyphenyl) Disulfide (2f) Mixture. A mixture of 3-methyl-
2-buten-1-ol (1a) (16 mg, 0.19 mmol) and bis(4-methoxyphenyl)
disulfide (2f) (53 mg, 0.19 mmol) in benzene (3.2 mL) was irradi-
ated with a high-pressure mercury lamp for 2.5 h at room temper-
ature. The resulting mixture was analyzed by GC. Decane was
used as the internal standard.
Photoirradiation of a 3-Methyl-2-buten-1-ol (1a) and Den-
drimer Disulfide 4 Mixture. A mixture of 3-methyl-2-buten-
1-ol (1a) (15 mg, 0.18 mmol) and dendrimer 4 (13 mg, 0.18 mmol)
in benzene (3.2 mL) was irradiated with a high-pressure mercury
lamp for 2.5 h at room temperature. The resulting mixture was
analyzed by GC. Decane was used as the internal standard.
Photoirradiation of a 3-Methyl-2-buten-1-ol (1a) and Den-
drimer Disulfide 5 Mixture. A mixture of 3-methyl-2-buten-
1-ol (1a) (15 mg, 0.18 mmol) and dendrimer 5 (22 mg, 0.18 mmol)
in benzene (3.2 mL) was irradiated with a high-pressure mercury
lamp for 2.5 h at room temperature. The resulting mixture was
analyzed by GC. Decane was used as the internal standard.
Photoirradiation of an Allyl Alcohol (1b) and Bis(4-methoxy-
carbonylphenyl) Disulfide (2b) Mixture. A mixture of allyl
alcohol (1b) (3.4 mg, 0.059 mmol) and bis(4-methoxycarbonyl-
phenyl) disulfide (2b) (20 mg, 0.059 mmol) in CDCl3 (1.0 mL)
was irradiated with a high-pressure mercury lamp for 30 min at
room temperature. The resulting mixture was analyzed by NMR.
t-Butyl acetate was used as the internal standard.
Photoirradiation of a (Z)-3-Chloro-2-propen-1-ol (1c) and
Bis(4-methoxycarbonylphenyl) Disulfide (2b) Mixture. (Z)-
3-Chloro-2-propen-1-ol (1c) was prepared using a method report-
ed by Alami et al.16 A mixture of (Z)-3-chloro-2-propen-1-ol (1c)
(18 mg, 0.19 mmol) and bis(4-methoxycarbonylphenyl) disulfide
(2b) (64 mg, 0.19 mmol) in CDCl3 (3.2 mL) was irradiated with
a high-pressure mercury lamp for 2 h at room temperature. The re-
sulting mixture was analyzed by NMR. t-Butyl acetate was used
as the internal standard.
Photoirradiation of a Cinnamyl Alcohol (11) and Dendri-
mer Disulfide 4 Mixture. A mixture of cinnamyl alcohol (11)
(17 mg, 0.13 mmol) and dendrimer 4 (160 mg, 0.13 mmol) in ben-
zene (2.2 mL) was irradiated with a high-pressure mercury lamp
for 2.5 h at room temperature. After removal of the solvent, the re-
sulting mixture was purified by silica-gel column chromatography
(eluent, chloroform) to afford cinnamaldehyde (12) (7.3 mg, 0.055
mmol) in 58% yield (based on consuming starting material).
Photoirradiation of a Cinnamyl Alcohol (11) and Dendri-
mer Disulfide 5 Mixture. A mixture of cinnamyl alcohol (11)
(21 mg, 0.16 mmol) and dendrimer 5 (120 mg, 0.16 mmol) in ben-
zene (2.7 mL) was irradiated with a high-pressure mercury lamp
for 2.5 h at room temperature. After removal of the solvent, the
resulting mixture was purified using silica-gel column chromatog-
raphy (eluent, chloroform) to afford cinnamaldehyde (12) (3.3 mg,
0.025 mmol) in 46% yield (based on consumed starting material).
Photoirradiation of a Geraniol (13) and Dendrimer Disul-
fide 5 Mixture. A mixture of geraniol (13) (22 mg, 0.14 mmol)
and dendrimer 5 (170 mg, 0.14 mmol) in benzene (2.4 mL) was
irradiated with a high-pressure mercury lamp for 2.5 h at room
temperature. After removal of the solvent, the resulting mixture
was purified by silica-gel column chromatography (eluent, chloro-
form) to afford citral (14) (3.4 mg, 0.022 mmol) and citronellal
(15) (5.0 mg, 0.032 mmol) in 38% and 54% yield, respectively
(based on consumed starting material).
Photoreaction of (E)-Citral (16) with Dendron Thiol 17.
(E)-Citral (16) was prepared by oxidation of geraniol (13) using
MnO2. A mixture of (E)-citral (16) (66 mg, 0.43 mmol) and den-
dron thiol 17 (312 mg, 0.85 mmol) in benzene (7.1 mL) was irra-
diated with a high-pressure mercury lamp for 12 h at room temper-
ature. After removal of the solvent, the resulting mixture was
purified by silica-gel column chromatography (eluent, chloroform)
to afford citronellal (15) (5.5 mg, 0.036 mmol) in 8% yield.
This work was partly supported by a Grant-in-Aid for Sci-
entific Research (No. 19010105) from the Ministry of Educa-
tion, Culture, Sports, Science and Technology (MEXT), Japan.
Photoirradiation of a 4-Methyl-3-penten-2-ol (1d) and Bis-
(4-methoxycarbonylphenyl) Disulfide (2b) Mixture. 4-Methyl-
3-penten-2-ol (1d) was prepared using a method reported by
Cain.17 A mixture of 4-methyl-3-penten-2-ol (1d) (19 mg, 0.19
mmol) and bis(4-methoxycarbonylphenyl) disulfide (2b) (64 mg,
0.19 mmol) in benzene (3.2 mL) was irradiated with a high-pres-
sure mercury lamp for 30 min at room temperature. The resulting
mixture was analyzed by GC. Decane was used as the internal
standard.
Photoirradiation of a 2,4-Dimethyl-3-penten-2-ol (1e) and
Bis(4-methoxycarbonylphenyl) Disulfide (2b) Mixture. A mix-
ture of 2,4-dimethyl-3-penten-2-ol (1e) (22 mg, 0.19 mmol) and
bis(4-methoxycarbonylphenyl) disulfide (2b) (64 mg, 0.19 mmol)
in benzene (3.2 mL) was irradiated with a high-pressure mercury
lamp for 20 min at room temperature. The resulting mixture was
analyzed by GC. Decane was used as the internal standard.
Photoirradiation of a Cinnamyl Alcohol (11) and Diphenyl
Disulfide (2a) Mixture. A mixture of cinnamyl alcohol (11)
Supporting Information
Copies of NMR spectra. This material is available free of
charge on the web at http://www.csj.jp/journals/bcsj/.
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