Photoinduced isomerization of allyl alcohols to carbonyl compounds using dendrimer disulfide as catalyst

Article abstract of DOI:10.1002/hc.20504

Allyl alcohols were isomerized to car- bonyl compounds using diphenyl disulfide derivatives upon photoirradiation. Especially, dendrimer disulfide catalyzed the isomerization of allyl alcohols. Photoinduced isomerization in water was also succeeded by the use of water-soluble dendrimer disulfide.

Full text of DOI:10.1002/hc.20504

Heteroatom Chemistry
Volume 20, Number 1, 2009
Photoinduced Isomerization of Allyl Alcohols
to Carbonyl Compounds Using Dendrimer
Disulfide as Catalyst
Takaaki Tsuboi, Yutaka Takaguchi, and Sadao Tsuboi
Graduate School of Environmental Science, Okayama University, Tsushima-Naka 3-1-1,
Okayama 700-8530, Japan
Received 5 March 2008; revised 14 July 2008
tional groups using disulfide as a photocatalyst.
ABSTRACT: Allyl alcohols were isomerized to car-
Meanwhile, with a growing demand for environ-
bonyl compounds using diphenyl disulfide deriva-
mentally benign reactions, catalytic reactions that
tives upon photoirradiation. Especially, dendrimer
are atom efficient receive increasing attention [13].
disulfide catalyzed the isomerization of allyl alcohols.
Isomerization of allyl alcohols forms an elegant
Photoinduced isomerization in water was also suc-
shortcut to carbonyl compounds in a completely
ceeded by the use of water-soluble dendrimer disul-
atom-economical process that offers several use-
ꢀ
C
fide.
2009 Wiley Periodicals, Inc. Heteroatom Chem
ful applications in natural-product syntheses and
in bulk chemical processes [14]. Although many re-
ports described isomerization of allyl alcohols us-
ing metal catalysts [15–18] such as Ru complexes
[16,17] and Fe-carbonyl complexes [15,18], isomer-
ization without metal catalyst was quite rare [19].
In this paper, we describe photoinduced isomeriza-
tion of allyl alcohols to carbonyl compounds using
diphenyl disulfide. Especially, dendrimer disulfide
catalyzed the isomerization of allyl alcohols. Pho-
toinduced isomerization in water by the use of water-
soluble dendrimer disulfide is also examined.
20:1–11, 2009; Published online in Wiley InterScience
(www.interscience.wiley.com). DOI 10.1002/hc.20504
INTRODUCTION
Photoreactivity of diphenyl disulfide derivatives has
attracted scientific attention in the past few decades
[1,2]. Sulfanyl radical generated by homolytic cleav-
age of the S–S bond plays important roles in
photoinitiated reactions such as sulfenylation of
aryl halides [3] and hindered phenols [4], vinyl
polymerization [5], and vicinal dichalcogenation of
unsaturated compounds [6–10]. A few examples
of transformation of the functional groups using
photoreaction of disulfide were also reported [11].
Recently, we have reported the photoinduced ox-
idation of allyl alcohols to acrylaldehydes using
diphenyl disulfide derivatives [12]. However, much
less is known about the transformation of func-
RESULTS AND DISCUSSION
In previous work, we reported that diphenyl disul-
fide derivatives mediate oxidation of various allyl al-
cohols to give acrylaldehydes upon photoirradiation
[12]. A plausible mechanism of photoinduced oxida-
tion of allyl alcohol is shown in Scheme 1. The reac-
tion was triggered by the sulfanyl radical generated
by photolysis of the diphenyl disulfide. Then, the ab-
straction of an α-hydrogen, which occurred from the
allyl alcohol to the sulfanyl radical, produced the al-
lylic radical and thiophenol. Next, a single electron
transfer (SET) occurred from the allylic radical to
another sulfanyl radical, and an allylic cation was
1
Correspondence to: Yutaka Takaguchi; e-mail: yutaka@cc.
okayama-u.ac.jp.
Contract grant sponsor: The Ministry of Education, Culture,
Sports, Science and Technology (MEXT), Japan.
Contract grant number: 19010105.
2009 Wiley Periodicals, Inc.
c
ꢀ

2
Tsuboi, Takaguchi, and Tsuboi
We followed the time course of this reac-
tion by an NMR and observed that citronellal (4),
isomerized product, was not formed until 20 min
after the start of the reaction, although oxidized
product, citral (3), was observed immediately af-
ter the start of the reaction [12]. A catalytic cycle
was proposed to explain this isomerization result
as Scheme 3. The first step was photolysis of disul-
fide. Subsequent oxidation of allyl alcohols yields
acrylaldehydes and thiols. Final hydrogenation of
acrylaldehydes produces isomerized products and
disulfides.
Komiya reported that isomerization of 2-
cyclohexene-1-ol using Ru catalyst gave higher yield
of isomerized product than yields of products of
the isomerization of 3-buten-2-ol or 1-phenylallyl
alcohol [16]. This result prompted us to inves-
tigate isomerization of 2-cyclohexene-1-ol using
diphenyl disulfide derivatives. A benzene solution of
2-cyclohexene-1-ol (5) in the presence of diphenyl
disulfide (6) was irradiated with a high-pressure
mercury lamp (λ > 300 nm) through a Pyrex filter
at room temperature under an argon atmosphere
for 5.5 h to give 2-cyclohexenone (7) and cyclo-
hexanone (8) in 14% and 56% yields, respectively
(Table 1, entry 1). Reactions in the dark or in the
absence of diphenyl disulfide (6) did not proceed.
Hence, the isomerization is a photoreaction medi-
ated by diphenyl disulfide (6). Isomerization of 3-
methyl-2-cyclohexene-1-ol (9) was also examined,
since photoinduced oxidation of trisubstituted allyl
alcohol gave higher yield of oxidized product than
SCHEME 1 Plausible mechanism of oxidation of allyl alco-
hol using photolysis of diphenyl disulfide.
formed. The thiolate anion, which was generated by
SET, abstracted the proton of OH group to give
the oxidized product and thiophenol. Interestingly,
photoirradiation of geraniol (1) in the presence of
dendrimer disulfide (2) gave isomerization product,
3,7-dimethyl-6-octenal (citroneral, 4), in 54% yield
(Scheme 2).
SCHEME 3 Catalytic cycle of photoinduced isomerization
of allyl alcohol.
SCHEME 2 Photoinduced oxidation of geraniol (1) using
dendrimer disulfide 2.
Heteroatom Chemistry DOI 10.1002/hc

Photoinduced Isomerization of Allyl Alcohols to Carbonyl Compounds Using Dendrimer Disulfide as Catalyst
TABLE 1 Photoinduced Isomerization of Allyl Alcohols Using Diphenyl Disulfide Derivativesa
3
Entry
1
Disulfide
Allyl Alcohol
OH
Time
Conversion
Product
O
Yieldb
14%
5.5 h
>99%
S
2
6
5
7
O
56%
trace
60%
81%
16%
79%
8
OH
O
2
5.5 h
>99%
S
2
6
9
10
O
11
O
OH
3
4
Dendrimer 12
Dendrimer 12
2.5 h
2.5 h
>99%
>95%
5
OH
8
O
9
10
O
11
aReactions initiated with UV-light (high-pressure mercury lamp, λ > 300 nm) in benxene at rt.
bGC yield (based on consumed starting material).
the result of oxidation of nonsubstituted allyl alco-
hol [12]. Photoinduced isomerization of allyl alcohol
9 using diphenyl disulfide (6) gave trace amount of
3-methyl-2-cyclohexenone (10) and 60% yield of 3-
methylcyclohexanone (11) (entry 2). Trace amount
of by-products, which might be formed by the addi-
tion reaction of disulfide or thiol to the olefins, was
observed in each photoreactions by GC analysis.
Although UV–vis spectra (λmax and ε) of den-
drimer disulfide is almost the same as diphenyl
disulfide, dendrimer disulfide is a good mediator
of photoinduced oxidation reaction of allyl alcohols
because dendritic substituents are quite effective to
inhibit side reactions initiated by the addition of sul-
fanyl radical to unsaturated bonds [12]. Hence, we
carried out the isomerization using dendrimer disul-
fide 12. Surprisingly, photoinduced isomerization of
allyl alcohol 5 using dendrimer disulfide 12 gave ke-
tone 8 as a sole product in 81% yield (entry 3). The
reaction of allyl alcohol 9 afforded product 11 in 79%
yield (entry 4). In this case, enone 10, a product of
oxidation of allyl alcohol 9, was also obtained in 16%
yield. These results indicated dendrimer disulfide 12
was effective for photoinduced isomerization.
Heteroatom Chemistry DOI 10.1002/hc

4
Tsuboi, Takaguchi, and Tsuboi
tion of 2-cyclopentene-1-ol (14) using 10 mol % of
dendrimer 12 gave corresponding cyclopentanone
(15) in 90% yield (entry 4).
Although the exact reaction mechanism is not
completely clear, a plausible mechanism of the cat-
alytic isomerization was shown in Scheme 4. The
oxidation step of isomerization was triggered by
the sulfanyl radical generated by the photolysis of
the diphenyl disulfide. Then, the abstraction of an
α-hydrogen, which occurred from the allyl alcohol
to the sulfanyl radical, produced the allylic radi-
cal and thiophenol. Next, a single electron transfer
(SET) occurred from the allylic radical to another
sulfanyl radical, and an allylic cation was formed.
The thiolate anion, which was generated by SET,
abstracted the proton of alcohol to give the oxidized
product and thiophenol. The hydrogenation step of
isomerization was initiated by the addition of sul-
fanyl radical to the C C bond of enone, a product
of oxidation. Next, the abstraction of hydrogen oc-
curred from the thiol to the carbon radical, and a
sulfide was formed (path A). This sulfide could also
be formed by the ionic addition reaction in the dark
(path B). After the tautomerization from keto-form
to enol-form, another sulfanyl radical (path C) or
thiolate anion (path D) attacked C S bond to form
disulfide. Finally, the abstraction of hydrogen (path
C) or proton (path D) occurred from the thiol and
hydrogenated product was formed. Recently, Ogawa
Because of the high reactivity, dendrimer disul-
fide 12 was expected to catalyze the isomerization of
allyl alcohols. We carried out the isomerization us-
ing 10 mol % of dendrimer disulfide 12. Results were
shown in Table 2. Isomerization of 2-cyclohexene-
1-ol (5) using 10 mol % of dendrimer disulfide 12
afforded cyclohexanone (8) in 90% yield (entry 1).
This result proved that the photoinduced isomer-
ization was a catalytic reaction. Unfortunately, pho-
toreaction in the presence of 1 mol % of dendrimer
disulfide was not completed (entry 2). Even though
longer reaction time was required, isomerization of
3-methyl-2-cyclohexene-1-ol (9) using 10 mol % of
dendrimer disulfide 12 gave 3-methylcyclohexanone
(11) in 91% yield (entry 3). Furthermore, isomeriza-
TABLE 2 Photoinduced Isomerization of Allyl Alcohols Using Dendrimer Disulfide 12 As Catalystsa
Entry
1
Disulfide (mol %)
Allyl Alcohol
OH
Time
Conversion
Product
O
Yieldb
90%
Dendrimer 12
(10 mol %)
2.5 h
>99%
5
OH
8
O
2
3
4
Dendrimer 12
(1 mol %)
12 h
12 h
2.5 h
54%
34%
91%
90%
5
OH
8
O
Dendrimer 12
(10 mol %)
>99%
>99%
11
O
9
OH
Dendrimer 12
(10 mol %)
14
15
aReactions initiated with UV-light (high-pressure mercury lamp, λ > 300 nm) in benxene at rt.
bGC yield (based on consumed starting material).
Heteroatom Chemistry DOI 10.1002/hc

Photoinduced Isomerization of Allyl Alcohols to Carbonyl Compounds Using Dendrimer Disulfide as Catalyst
5
1-ol (5) to cyclohexanone (8) is −59.86 kJ mol−1,
and that from 3-methyl-2-cyclohexene-1-ol (9) to
3-methylcyclohexanone (11) is −43.92 kJ mol−1. The
stabilization by isomerization from geraniol (1) to
citroneral (4) is −27.96 kJ mol−1, which is the small-
est value among these three examples. These cal-
culated results are in good accordance with the dif-
ference of reactivity among 2-cyclohexene-1-ol (5),
3-methyl-2-cyclohexene-1-ol (9), and geraniol (1).
To extend the scope of the reaction, we carried
out the photoinduced isomerization using water-
soluble dendrimer disulfide as a catalyst in wa-
ter. Water-soluble dendrimer disulfide 16, which
has sugar moiety at the terminals, was synthesized
as Scheme 5. The treatment of dendrimer disul-
fide 12 with ethylenediamine produced dendrimer
disulfide 17. Subsequently, 17 was allowed to re-
act with glucono-δ-lactone to give dendrimer disul-
fide 16 (66%, two steps). The structure of dendrimer
and coworkers have been reported photoinduced re-
duction of conjugate dienes using a PhSH-(PhSe)2
binary system [20]. The reaction mechanism of the
reduction of diene was similar to the plausible mech-
anism of hydrogenation step of our isomerization.
There could be alternative pathways, that is, direct
isomerizations via the formation of cation radical of
allyl alcohol by photoinduced SET process or the hy-
drogen atom donation from a thiol to an allyl radical
instead of SET process [21,22]. However, since we
observed the enone as an intermediate, the alterna-
tive pathway might be excluded.
On the contrary to dendrimer 12, higher gen-
eration dendrimer disulfide 13 was not so effective
to mediate photoinduced isomerization (Table 3,
entries 3 and 4). This result might indicate that
dendrimer having too bulky dendritic wedge inhib-
ited not only side reactions but also isomerization
reaction.
disulfide 16 was confirmed by 1H NMR spectroscopy
and MALDI-TOF-MS. The MALDI-TOF-MS spec-
trum of dendrimer disulfide 16 showed the parent
peak at m/z 1559.34, which was consistent with the
calculated data (1559.64 [MH+]), as shown in Fig. 2.
We then carried out photoinduced isomerization
of allyl alcohols using dendrimer disulfide 16 in wa-
ter (Scheme 6). Photoirradiation of 2-cyclohexene-
1-ol (5) in the presence of 10 mol % of dendrimer
disulfide 16 gave cyclohexanone (8) in 60% yield.
3-Methyl-2-cyclohexene-1-ol (9) was also employed
for this reaction to achieve stereoselective isomeriza-
tion. However, racemic 3-methylcyclohexanone (11)
was obtained in 56% yield.
It is notable that the products of the photore-
action, oxidized product or isomerized product, do
not depend on the reaction conditions but depend
on ꢀG◦ of the reaction, that is, the difference of
thermodynamic stability between allyl alcohols
(starting materials), carbonyl compounds (oxidized
products), and saturated carbonyl compounds
(isomerized products). The heats of formation (ꢀH )
f
of allyl alcohols, allyl carbonyl compounds, and
carbonyl compounds derived from PM3 calculations
were shown in Fig. 1. The change in the ꢀH before
f
and after photoinduced isomerization proved sta-
bilization by the photoinduced isomerization. The
stabilization by isomerization from 2-cyclohexene-
Heteroatom Chemistry DOI 10.1002/hc

6
Tsuboi, Takaguchi, and Tsuboi
EXPERIMENTAL SECTION
General Method
The NMR spectra was measured using a spectrom-
eter (AL300; JEOL, Tokyo, Japan). Matrix-assisted
laser desorption ionization time-of-flight mass spec-
troscopy (MALDI-TOF-MS) was performed on a
mass spectrometer (Autoflex; Bruker Daltonics Inc.,
Tokyo, Japan). Gas chromatography (GC) analyses
were carried out on a gas chromatograph (GC18A;
Shimadzu Corp., Tokyo, Japan) equipped with an
FID detector and a fused silica capillary column (30
m × 0.53 mm i.d., coating DB-1; J&W Scientific Inc.,
Tokyo, Japan). The oven was maintained at 40◦C
for 5 min, programmed at 2◦C min−1 between 40
and 100◦C, and programmed at 20◦C min−1 between
100 and 270◦C. The GC-MS analyses were performed
on a GC-MS workstation (QP5000; Shimadzu Corp.,
Tokyo, Japan) with a fused silica capillary column
(30 m × 0.25 mm i.d., coating TC-5; GL Science Co.
Ltd., Tokyo, Japan). Optical rotations were recorded
on a polarimeter (SEPA-300; HORIBA Corp., Tokyo,
Japan, λ = 589 nm). Photoirradiation was carried
out using a Pyrex reactor. Prior to irradiation, sol-
vents were degassed with nitrogen for 30 min. A 500
W high-pressure mercury lamp (EHB-500; Eikosha
Corp., Osaka, Japan) was used as the light source.
Unless otherwise noted, the reagents were obtained
from Wako Pure Chemical Industries Ltd. (Tokyo,
Japan), Tokyo Kasei Kogyo Co. Ltd. (Tokyo, Japan),
Kanto Kagaku (Tokyo, Japan), or Aldrich Chemical
Co. Inc. (Tokyo, Japan). The Et2O used in reactions
was further purified using a general method. Other
solvents and reagents were used as received with-
out further purification. Dendrimer disulfide 12 and
13 were synthesized according to the previously re-
ported method [10,12].
SCHEME
4
Plausible mechanism of photoinduced
isomerization.
3-Methyl-2-cyclohexen-1-ol (10)
3-Methylcyclohexen-1-one (11) (5.00 g, 45.4 mmol)
in dry Et2O (5 mL) was added simultaneously
over 20 min to lithium aluminum hydride (0.86 g,
22.7 mmol) in dry Et2O (10 mL) at −50◦C. After
stirring at −50◦C for 1 h, ice-cold water (1.5 mL),
4 N aqueous solution of NaOH (1.5 mL), and water
(7 mL) were added in order. The aqueous slurry was
extracted with Et2O. Et2O layer was washed with
brine, dried over MgSO4, and evaporated under ice
cooling. The residue was purified using distillation
(bp 52◦C) and silica gel column chromatography
(eluent, chloroform:methanol = 40:1) to afford 3-
methyl-2-cyclohexen-1-ol (10) (1.34 g, 11.9 mmol) as
a colorless liquid in 26% yield, identically to that of
an authentic sample [23]: 1H NMR (300 MHz, CDCl3)
CONCLUSION
In summary, we disclosed a novel photoinduced iso-
merization of allyl alcohols mediated by diphenyl
disulfide. In particular, an effective isomerization of
allyl alcohol was accomplished by the use of den-
drimer disulfides as catalysts. The reaction using
water-soluble dendrimer disulfide in water was also
succeeded. Further work is in progress to explore the
applications and advantages of photoinduced iso-
merization using dendrimer disulfide.
Heteroatom Chemistry DOI 10.1002/hc

Photoinduced Isomerization of Allyl Alcohols to Carbonyl Compounds Using Dendrimer Disulfide as Catalyst
7
TABLE 3 Photoinduced Isomerization of Allyl Alcohols Using Dendrimer 12 and Higher Generation Dendrimer 13a
Entry
1
Disulfide (mol%)
Allyl Alcohol
OH
Time
Conversion
Product
O
Yieldb
90%
Dendrimer 12
(100 mol %)
2.5 h
>99%
8
5
2
3
Dendrimer 12
(10 mol %)
2.5 h
2.5 h
>99%
90%
O
OH
8
5
Dendrimer 13
(100 mol %)
55%
trace
O
7
O
66%
8
4
Dendrimer 13
(10 mol %)
2.5 h
27%
trace
O
7
O
72%
8
aReactions initiated with UV-light (high-pressure mercury lamp, λ > 300 nm) in benxene at rt.
bGC yield (based on consumed starting material).
δ 1.33 (dd, J = 2.7 and 9.0 Hz, 1H), 1.50–1.61 (m,
2H), 1.69 (s, 3H), 1.74–1.80 (m, 2H), 1.87–1.96 (m,
2H), 4.17 (s, 1H), 5.50 (s, 1H).
was cooled at <0◦C for 18 h. A white precipitate was
filtered, washed with Et2O, and dried to afford the
dendrimer disulfide 16 (725 mg, 0.46 mmol) as a
1
white solid in 66% yield: H NMR (300 MHz, D2O)
δ 2.29 (m, 4H), 2.50–2.80 (m, 7H), 3.00–3.20 (m 8H),
3.23 (s, 2H), 3.30–3.75 (m, 12H), 3.96 (s, 2H), 4.17
(s, 2H), 7.51 (d, J = 8.4 Hz, 2H), 7.59 (d, J = 7.8 Hz,
2H); MALDI-TOF-MASS (matrix, sinapic acid): m/z
1559.34 ([MH]+). Calcd. for C142H238N28O46S2: m/z
1559.64; [α]2D2 = +19.1 (c = 1.06, water).
Preparation of the Dendrimer Disulfide 16
A solution of dendrimer disulfide 12 (511 mg,
0.70 mmol) in methanol (38 mL) was added drop-
wise to ethylenediamine (38 mL, 556 mmol) under
ice cooling. The mixture was stirred at room tem-
perature for 13 h. After removal of the solvent under
reduced pressure at 45◦C, the residue was reprecipi-
tated from a methanol–ether solution to obtain den-
drimer disulfide 17, which was used for the following
reaction without further purification.
Photoinduced Isomerization of the 2-Cyclo-
hexene-1-ol (5) Using 100 mol % of Diphenyl
Disulfide (6)
A solution of 17 in methanol (5 mL) was added
to a vigorously stirred solution of Glucono-δ-lactone
(2.48 g, 13.9 mmol) in methanol (139 mL) at 50◦C.
After stirring at 50◦C for 2 h, the reaction mixture
A mixture of 2-cyclohexene-1-ol (5) (18.4 mg,
0.19 mmol) and diphenyl disulfide (6) (41.5 mg,
0.19 mmol) in benzene (3.2 mL) was irradiated
with a high-pressure mercury lamp for 5.5 h at
Heteroatom Chemistry DOI 10.1002/hc

8
Tsuboi, Takaguchi, and Tsuboi
perature. The resulting mixture was analyzed by GC.
Decane was used as the internal standard. Cyclo-
hexanone (8) was identified with the retention time
9.0 min (81%).
Photoinduced Isomerization of the 2-Cyclo-
hexene-1-ol (5) Using 10 mol % of Dendrimer
Disulfide 12
A mixture of 2-cyclohexene-1-ol (5) (34.8 mg,
0.36 mmol) and dendrimer disulfide 12 (26.1 mg,
0.036 mmol) in benzene (6 mL) was irradiated with
a high-pressure mercury lamp for 2.5 h at room tem-
perature. The resulting mixture was analyzed by GC.
Decane was used as the internal standard. Cyclo-
hexanone (8) was identified with the retention time
9.0 min (90%).
Photoinduced Isomerization of the 2-Cyclo-
hexene-1-ol (5) Using 1 mol % of Dendrimer
Disulfide 12
FIGURE 1 Heats of formation (ꢀHf) of allyl alcohols, α,β-
unsaturated carbonyl compounds, and saturated carbonyl
compounds derived from PM3 calculations.
A mixture of 2-cyclohexene-1-ol (5) (33.4 mg,
0.34 mmol) and dendrimer disulfide 12 (2.5 mg, 3.4
× 10−3 mmol) in benzene (5.7 mL) was irradiated
with a high-pressure mercury lamp for 12 h at room
temperature. The resulting mixture was analyzed by
GC. Decane was used as the internal standard. Two
compounds were identified with the following reten-
tion times: (a) retention time 9.0 min, cyclohexanone
(8) (18%); (b) retention time 9.4 min, 2-cyclohexene-
1-ol (5) (46%).
room temperature. The resulting mixture was
analyzed by GC. Decane was used as the internal
standard. Three compounds were identified with
the following retention times: (a) retention time
9.0 min, cyclohexanone (8) (56%); (b) retention time
9.4 min, 2-cyclohexene-1-ol (5) (trace); (c) retention
time 11.0 min, 2-cyclohexenone (7) (14%).
Photoinduced Isomerization of the 3-Methyl-
2-cyclohexene-1-ol (9) Using 100 mol % of
Diphenyl Disulfide (6)
Photoinduced Isomerization of the 3-Methyl-
2-Cyclohexene-1-ol (9) Using 100 mol % of
Dendrimer Disulfide 12
A
mixture of 3-methyl-2-cyclohexene-1-ol (9)
(21.3 mg, 0.19 mmol) and diphenyl disulfide (6)
(41.5 mg, 0.19 mmol) in benzene (3.2 mL) was
irradiated with a high-pressure mercury lamp for
6 h at room temperature. The resulting mixture
was analyzed by GC. Decane was used as the in-
ternal standard. Two compounds were identified
with the following retention times: (a) retention time
12.7 min, 3-methylcyclohexanone (11) (60%); (b)
retention time 19.7 min, 3-methyl-2-cyclohexenone
(10) (trace).
A mixture of 3-methyl-2-cyclohexene-1-ol (9) (38 mg,
0.34 mmol) and dendrimer disulfide 12 (249 mg,
0.34 mmol) in benzene (5.7 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.
Three compounds were identified with the follow-
ing retention times: (a) retention time 12.7 min, 3-
methylcyclohexanone (11) (75%); (b) retention time
15.5 min, 3-methyl-2- cyclohexene-1-ol (9) (5%);
(c) retention time 19.7 min, 3-methyl-2-cyclo-
hexenone (10) (15%).
Photoinduced Isomerization of the 2-Cyclo-
hexene-1-ol (5) Using 100 mol % of Dendrimer
Disulfide 12
Photoinduced Isomerization of the 3-Methyl-
2-Cyclohexene-1-ol (9) Using 10 mol % of
Dendrimer Disulfide 12
A mixture of 2-cyclohexene-1-ol (5) (15.0 mg,
0.15 mmol) and dendrimer disulfide 12 (110 mg,
0.15 mmol) in benzene (2.5 mL) was irradiated with
a high-pressure mercury lamp for 2.5 h at room tem-
A
mixture of 3-methyl-2-cyclohexene-1-ol (9)
(35.1 mg, 0.31 mmol) and dendrimer disulfide 12
Heteroatom Chemistry DOI 10.1002/hc

Photoinduced Isomerization of Allyl Alcohols to Carbonyl Compounds Using Dendrimer Disulfide as Catalyst
9
SCHEME 5 Synthesis of water-soluble dendrimer disulfide 16.
(23.0 mg, 0.031 mmol) in benzene (5.3 mL) was
irradiated with a high-pressure mercury lamp for
12 h at room temperature. The resulting mixture
was analyzed by GC. Decane was used as the inter-
nal standard. 3-Methylcyclohexanone (11) was iden-
tified with the retention time 12.7 min (91%).
0.17 mmol) in benzene (2.9 mL) was irradiated with
a high-pressure mercury lamp for 2.5 h at room tem-
perature. The resulting mixture was analyzed by GC.
Decane was used as the internal standard. Three
compounds were identified with the following reten-
tion times: (a) retention time 9.0 min, cyclohexanone
(8) (18%); (b) retention time 9.4 min, 2-cyclohexene-
1-ol (5) (73%); (c) retention time 11.0 min, 2-
cyclohexenone (7) (trace).
Photoinduced Isomerization of the 2-Cyclo-
pentene-1-ol (14) Using 10 mol % of Dendrimer
Disulfide 12
A mixture of 2-cyclopentene-1-ol (14) (33.7 mg,
0.40 mmol) and dendrimer disulfide 12 (29.7 mg,
0.040 mmol) in benzene (5.0 mL) was irradiated with
a high-pressure mercury lamp for 2.5 h at room tem-
perature. The resulting mixture was analyzed by GC.
Decane was used as the internal standard. Cyclopen-
tanone (15) was identified with the retention time
7.2 min (90%).
Photoinduced Isomerization of the 2-Cyclo-
hexene-1-ol (5) Using 10 mol % of Dendrimer
Disulfide 13
A mixture of 2-cyclohexene-1-ol (5) (34.8 mg,
0.36 mmol) and dendrimer disulfide 13 (26.1 mg,
0.036 mmol) in benzene (6 mL) was irradiated with
a high-pressure mercury lamp for 2.5 h at room tem-
perature. The resulting mixture was analyzed by GC.
Decane was used as the internal standard. Three
compounds were identified with the following reten-
tion times: (a) retention time 9.0 min, cyclohexanone
(8) (36%); (b) retention time 9.4 min, 2-cyclohexene-
1-ol (5) (45%); (c) retention time 11.0 min, 2-
cyclohexenone (7) (trace).
Photoinduced Isomerization of the 2-Cyclo-
hexene-1-ol (5) Using 100 mol % of Dendrimer
Disulfide 13
A mixture of 2-cyclohexene-1-ol (5) (17.1 mg,
0.17 mmol) and dendrimer disulfide 13 (268 mg,
Heteroatom Chemistry DOI 10.1002/hc

10 Tsuboi, Takaguchi, and Tsuboi
Photoinduced Isomerization of the 3-Methyl-
2-cyclohexene-1-ol (9) Using 10 mol % of
Dendrimer Disulfide Having Sugar Moiety 15
A
mixture of 3-methyl-2-cyclohexene-1-ol (9)
(21.3 mg, 0.19 mmol) and dendrimer disulfide 15
(30.0 mg, 0.019 mmol) in deionized water (3.2 mL)
was irradiated with a high-pressure mercury lamp
for 18 h at room temperature. The resulting mixture
was analyzed by GC. Cyclohexanone was used as the
internal standard. 3-Methylcyclohexanone (11) was
identified with the retention time 12.7 min (56%).
Calculations
The semiempirical calculations by the PM3 method
were performed using MOPAC version 6.02 [24] with
parameters in Ref. [25]. In the calculation, totally
optimized molecular geometries in the ground state
were used.
FIGURE 2 MALDI-TOF-MS spectrum of dendrimer sulfide
16.
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SCHEME 6 Photoinduced isomerization using dendrimer
16 in water.
Heteroatom Chemistry DOI 10.1002/hc

Photoinduced Isomerization of Allyl Alcohols to Carbonyl Compounds Using Dendrimer Disulfide as Catalyst 11
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Heteroatom Chemistry DOI 10.1002/hc