Generation of quinone methide from aminomethyl(hydroxy)arenes precursors in aqueous solution

Article abstract of DOI:10.1016/j.tet.2005.04.037

o-Quinone methides (QMs) are an important reactive intermediate for organic synthetic and biological standpoints of view. Photochemical and thermal transformation of N,N-dialkyl-9-aminomethyl-10-phenanthrols and their naphthalene analogs, which act as QM precursors, has been studied. These precursors readily reacted with alkyl vinyl ethers to give 2-alkoxydibenzo[f,h] chroman and 2-alkoxybenzo[f]chroman, respectively. Thermal and photochemical generation of QM was accelerated by the presence of water molecule in reaction solvents and by the formation of anionic micelle and vesicle.

Full text of DOI:10.1016/j.tet.2005.04.037

Tetrahedron 61 (2005) 5735–5740
Generation of quinone methide from
aminomethyl(hydroxy)arenes precursors in aqueous solution
a
a
a
Jin Matsumoto,a, Masayuki Ishizu, Ryu-ichiro Kawano, Daisuke Hesaka,
*
Tsutomu Shiragami,a Yoshimi Hayashi,b Toshiaki Yamashitab and Masahide Yasudaa
aDepartment of Applied Chemistry, Faculty of Engineering, University of Miyazaki, Gakuen-Kibanadai, Miyazaki 889-2192, Japan
bDepartment of Chemical Science and Engineering, Miyakonojo National College of Technology, Miyakonojo, Miyazaki 885-8567, Japan
Received 23 March 2005; revised 20 April 2005; accepted 20 April 2005
Abstract—o-Quinone methides (QMs) are an important reactive intermediate for organic synthetic and biological standpoints of view.
Photochemical and thermal transformation of N,N-dialkyl-9-aminomethyl-10-phenanthrols and their naphthalene analogs, which act as QM
precursors, has been studied. These precursors readily reacted with alkyl vinyl ethers to give 2-alkoxydibenzo[f,h]chroman and
2-alkoxybenzo[f]chroman, respectively. Thermal and photochemical generation of QM was accelerated by the presence of water molecule in
reaction solvents and by the formation of anionic micelle and vesicle.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
reported the photochemical generation of QM using
(2-hydroxybenzyl)trimethylammonium salts as more effec-
tive precursors in water.7 In order to develop the efficient
generation of QMs in aqueous solution, we will report on
solvent and micelle effects on the photochemical and
thermal transformations from aminomethyl(hydroxy)arenes
(1) to QMs.
Photochemical reactions in aqueous solution have been
received much attention from viewpoints of environ-
mentally benign process. However, the advantages of use
of water as reaction solvent are still low, because many
reactions in aqueous solution are inefficient than those in
organic solvents. Recently, much attention has been paid to
the water-enhancing effect on the generation of o-quinone
methide and the analogs (QMs), which are one of the
important reactive intermediates from synthetic and bio-
logical standpoints of view.1 Wan et al., for example, have
reported on the photochemical generation of QMs by the
elimination of water from o-(hydroxymethyl)phenol deriva-
tives.2 They proposed that an intramolecular proton transfer
in the excited state of o-hydroxystyrene was accelerated by
intervention of water molecule that was named ESIPT
(exited state intramolecular proton transfer) mechanism,
resulting in more effective reaction in aqueous organic
solvent than water-free solvents.3 Yate4 and our group5 have
reported the nucleophilic addition to QM via proton transfer
in aqueous solution. Also, Nakatani and his co-workers
have reported on the photochemical generation of QM from
N,N-dimethyl-6-phenyl-2-(aminomethyl)phenol which is
highly accelerated in aqueous solvents.6 Freccero has
2. Results and discussion
2.1. Products
N,N-Dialkyl-9-aminomethyl-10-phenanthrols (1a–b) and
N,N-dialkyl-1-aminomethyl-2-naphthols (1c–e) were easily
prepared by Mannich reactions of 9-phenanthrol and
2-naphthol with the alkylamines in the presence of formalin,
respectively. The thermal reaction of N,N-dimethyl-9-
aminomethyl-10-phenanthrol (1a) with ethyl vinyl ether
(2a) proceeded in aqueous MeOH, MeCN, DMF, and THF
solutions at 50 8C to give 2-ethoxydibenzo[f,h]chroman
(3a), but did not proceed in water-free MeOH and THF
solutions (Table 1). 9,10-Phenanthrenequinone (4) was
produced as a by-product from the thermal reaction of 1a–b
in MeCN–H2O and DMF–H2O.
The photoreactions of 1 with vinyl ethers (2) were carried
out by irradiating a degassed solution containing 1 and 2
by a high-pressure mercury lamp through a Pyrex filter
(lO280 nm) at 20 8C (Scheme 1). The photoreaction of 1a
Keywords: Quinone methide; Cycloaddition; Micelle effect; Photochemical
generation.
*
Corresponding author. Tel./fax: C81 985 58 7315;
e-mail: jmatsu@cc.miyazaki-u.ac.jp
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.04.037

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J. Matsumoto et al. / Tetrahedron 61 (2005) 5735–5740
Table 1. Photoreaction of 1 with 2a in aqueous solution
1
Solvent
Time (h)
Methoda
3 (Yields/%)b
1a
1a
1a
1a
1b
1c
1d
1e
1a
1a
1a
1a
1b
1c
1d
1e
MeCN–H2O (6:4)
DMF–H2O (6:4)
MeOH–H2O (6:4)
THF–H2O (6:4)
MeCN–H2O (6:4)
MeCN–H2O (6:4)
MeCN–H2O (6:4)
MeCN–H2O (6:4)
MeCN–H2O (6:4)
MeOH–H2O (6:4)
DMF–H2O (6:4)
THF–H2O (6:4)
10
10
10
10
10
20
20
20
10
10
10
10
10
10
10
10
A
A
A
A
A
A
A
A
B
B
B
B
B
B
B
B
3a (74) [0]
3a (30) [0]
3a (25) [0]
3a (4) [0]
3a (78)
3d (20, 17c)
3d (30)
3d (43)
3a (50)d [0]
3a (84) [0]
3a (66)e [0]
3a (70) [0]
3a (72)
MeCN–H2O (6:4)
MeCN–H2O (6:4)
MeCN–H2O (6:4)
MeCN–H2O (6:4)
3d (15)
3d (44)
3d (58)
a Method A: photoreaction at room temperature. Method B: thermal reaction at 50 8C.
b The values in the blanket are the yields in the solvents in the absence of water.
c The value is the reported yield (Ref. 6).
d Accompanied by the formation of 9,10-phenanthrenequinone (4) in 32% yield.
e Accompanied by the formation of 4 in 6% yield.
Scheme 1. Photoreactions of 1 with vinyl ethers (2).
with ethyl vinyl ether (2a) in MeCN–H2O (6:4) gave
selectively 3a in 74% yield without the formation of 4.
However, the photoreaction of 1a at higher temperature in
MeCN–H2O gave 3a and 2-ethoxy-4-oxodibenzo[f,h]-
chroman (5a) which was formed as a consequence of
the photoreaction of 4 with 2a. As shown in Table 1, the
reaction yields were depending on the solvent used. The
photoreaction of 1a with 2a proceeded more efficiently in
aqueous MeCN solution compared with that in MeOH–H2O
and THF–H2O. It is noteworthy that no reaction occurred
entirely in the water-free solvents and even in MeOH
regardless of the presence of OH group. Therefore, the
presence of water was requisite for the efficient formation of
3 in the photochemical and thermal reactions.
containing more electron-donating alkyl groups on the
amino group. The yields were slightly improved in thermal
and photochemical reactions.
2.2. Micelle effect
The photocycloaddition of 1a with 2a proceeded efficiently
in aqueous solution of sodium dodecylsulfate (SDS) that
formed a micelle (aggregation number, AN, is 62) in
concentrations higher than critical micelle concentration
(CMCZ8.1 mM). Figure 1 shows the dependence of the
yields of 3a on the concentration of SDS. In the case of the
photochemical reaction, the reaction yields were remark-
ably enhanced in the presence of SDS of concentrations
higher than CMC to reach maximum yield at O9 mM. In
the thermal reaction, however, the yield increased
gradually, showing no sharp enhancing effect at CMC. It
might be due to the disorder of the micelle structure in
higher temperature. The formation of 3 occurred effectively
in aqueous solution of sodium 1,2-bis(alkyloxycarbonyl)-
ethanesulfonate (BESn: nZ10 for decyl and 12 for dodecyl
groups), which was tend to form a vesicle in aqueous
solution.9,10 Figure 2 shows the dependence of the yields of
3 on the concentration of BESn. The yields reached to 60%
The photochemical and thermal reactions of N,N-dimethyl-
1-aminomethyl-2-naphthol (1c) with enamines have been
previously reported.8 However, the yields of the cyclo-
adducts were relatively low compared with the case of 1a.
Also, Nakatani et al. have reported that the photoreaction
of 1c with 2a in MeCN–H2O (6:4) gave 2-ethoxybenzo[f]-
chroman (3d) but the yield was still low.6 In order to
improve the chemical yields of 3d, we performed the
reaction of N,N-dialkyl-1-aminomethyl-2-naphthols (1d–e)

J. Matsumoto et al. / Tetrahedron 61 (2005) 5735–5740
5737
Figure 1. Dependence of the yields on the concentration of SDS in the
photochemical (C) and thermal (B) reactions of 1a with 2a in aqueous
solution.
Figure 3. Dependence of the yields on the concentration of PED in the
photochemical reactions of 1a with 2a in aqueous solution.
can stabilize micelles by the formation of hydrogen bond
with the anionic site on the surface of the micelles
(Scheme 2). In anionic micelle, therefore, the hydrophilic
OH and NR2 groups of 1 might be fixed on the surface of a
by the addition of BESn in concentrations higher than
0.9 mM for BES10 and 1.0 mM for BES12 to the solution.
The advantage of the use of BESn vesicle is to lower the
surfactant concentration than the case of SDS micelle.
Table 2. Photoreaction of 1a with 2a–c in aqueous surfactant solutiona
However, the reaction in nonionic surfactant such as
poly(ethyleneglycol) dodecyl ether (PED; CMCZ
0.09 mM, ANZ400) was ineffective (Fig. 3), and the
reactions in aqueous solution of cationic surfactant such as
hexadecyltrimethylammonium chloride (CTAC; CMCZ
1.3 mM, ANZ78) did not occur at all (Table 2). Also, the
photoreaction of 1a with CH2]CH–OR (2b; RZi-Bu and
2c; RZ–CH2CH2OH) in aqueous SDS solution gave the
corresponding 2-alkoxydibenzo[f,h]chroman (3b–c). But,
the photoreaction of 1a with such other alkenes as 2,3-
dimethyl-2-butene and acrylonitrile gave no products.
Solvent/surfactantb
2
Methodc
3 (Yields/%)
H2O/SDS (30 mM)
H2O/SDS (30 mM)
H2O/BES12 (1 mM)
H2O/BES12 (1 mM)
H2O/BES10 (1 mM)
H2O/PED (30 mM)
H2O/CTAC (30 mM)
H2O/SDS (30 mM)
H2O/SDS (30 mM)
2a
2a
2a
2a
2a
2a
2a
2b
2c
A
B
A
B
A
A
A
A
A
3a (61)
3a (72)
3a (58)
3a (41)
3a (58)
3a (29)
3a (0)
3b (29)
3c (43)
a Reaction time was 10 h.
b The surfactants are as follows:
Although micelle and vesicle operate mainly to dissolve 1
into aqueous solution, the yields were depending on the
surfactant used. Anionic surfactants is well known to
construct the rigid micelle compared with cationic and
nonionic surfactants, because surrounding water molecule
c Method A: photoreaction at room temperature. Method B: thermal
reaction at 50 8C
Figure 2. Dependence of the yields on the concentration of BESn: nZ10
(C), nZ12 (:) in the photoreaction of 1a with 2a in aqueous solution.
Scheme 2. Schematic representation of micelle surface.

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J. Matsumoto et al. / Tetrahedron 61 (2005) 5735–5740
460 nm in MeCN. As an increase of the water contents in
MeCN, the emission of 460 nm decreased and new emission
appeared at 380 nm. It is well known that the phenolic
compounds in the excited singlet state are readily converted
in the presence of a base to the excited singlet state of the
phenolate anion. Therefore, it is safely assigned that the
emission at 460 nm comes from the excited singlet states of
the zwitter ion (6) transformed by the intramolecular proton
transfer from the OH to the NH2 groups of 1a. Moreover, it
is suggested that the emissions at 380 nm come from the
excited singlet states of the intermediate (7) generated by
the protonation on the oxy anion of 6, since, the emissions at
380 nm observed in the MeCN–H2O solution was similar to
the fluorescence of 9-phenanthrol (lmaxZ384 nm). The
photochemically and thermally activated 7 induced the
Hofmann elimination of R2NH to give QM intermediate.
Similar mechanism has been reported for the photochemical
and thermal generation of QM from (2-hydroxybenzyl)-
trimethylammonium iodide (Scheme 3).5
Figure 4. Fluorescence spectra of 1a in MeCN and MeCN–H2O (1:1): The
excitation at 300 nm, the concentration of 1aZ1!10K5 M.
micelle, while the residual aromatic moiety was oriented
toward hydrophobic domain. This causes to induce effective
assistance of surrounding water molecule, resulting in the
efficient elimination of amine from 1.
2.4. Participation of water molecule
It has been reported that a water molecule accelerates the
intramolecular proton transfer in o-hydroxystyrene by
ESIPT mechanism. As mentioned above, however, the
fluorescence spectra of 1 showed the formation of the
zwitter ion (6) in MeCN. In contrast to the case of
o-hydroxystyrene, the proton transfer of 1 proceeds
smoothly even in water-free solvents because of the stronger
basicity of the amino group than the vinyl group. In the case
of 1, therefore, the enhancing effect of water molecule
operates for the elimination step of R2NH rather than the
proton transfer step.
By contrast, the cationic and nonionic surfactants seem
unfavorable to form a micelle with a dense of hydrophobic
domain, because of little stabilizing effect by surrounding
water. Therefore, the hydrophilic OH and NR2 groups of 1
might arrange randomly in the micelle, resulting that the
effect of surrounding water molecule is little. Similar
specific enhancing effects of anionic surfactants have
already been elucidated on tetra-O-acetylriboflavin-photo-
sensitized ring-splitting reaction of pyrimidine cyclo-
butanes11 and dehydrogenation of benzyl alcohols12
in aqueous solution. Thus, the assistance of surrounding
water is favorable for the elimination of the amine from 1.
As a conclusion, the recent research of QM intermediate is
aimed to the utilization for the bio-molecules involving
nucleic acids and peptides.1 Among a variety of methods to
generate QM, therefore, the attention will be focused on the
precursor acting in aqueous solution under mild conditions.
The photochemical generation of QM from 1 in micelle
meets the above requirements.
2.3. Spectroscopic analysis
As has been reported for the formation of QM in the
photochemical and thermal reactions of 1c,3,6 it is suggested
that the QM intermediates, 9-methylene-10-phenanthrone,
were formed by the elimination of R2NH in the cases of the
phenanthrene analogs, 1a–b (Scheme 1). It is well known
that the QMs generated from various precursors undergo
thermally the cycloaddition reaction with C]C double
bonds.1 Figure 4 shows the fluorescence spectra of 1a in
MeCN and aqueous MeCN. The emission was observed at
3. Experimental
9-Bromophenanthrene, 2-naphthol, the amines, and the
surfactants were purchased from Wako Chemicals and were
used. Commercially available ethyl vinyl ether, isobutyl
Scheme 3. Photochemical generation of o-QM.

J. Matsumoto et al. / Tetrahedron 61 (2005) 5735–5740
5739
vinyl ether, and ethylene glycol monovinyl ether were used
after distillation to remove the stabilizer (KOH).
3.1.4. N,N-Diethyl-1-aminomethyl-2-naphthol (1d). Yield
68%. H NMR dZ1.12 (d, JZ7.2 Hz, 6H), 2.65 (q, JZ
1
7.2 Hz, 4H), 4.15 (s, 2H), 7.07 (d, JZ8.8 Hz, 1H), 7.18–
7.26 (m, 1H), 7.35–7.42 (m, 2H), 7.46–7.76 (m, 3H); 13C
NMR dZ11.23, 46.32, 52.21, 111.20, 118.54, 119.32,
120.69, 122.13, 126.16, 128.26, 128.62, 132.53, 157.04.
Exact mass. calcd for C15H19NO: 229.1467. Found
229.1466.
1H and 13C NMR spectra were measured on a Bruker AC
250P spectrometer. MS spectra were obtained on a Hitachi
M2000A spectrometer. Fluorescence spectra were
measured on a Shimadzu RF5300PC fluorometer.
3.1. Preparation of aminomethyl(hydroxy)arenes (1a–e)
3.1.5. N,N-Diisopropyl-1-aminomethyl-2-naphthol (1e).
Yield 21%. 1H NMR dZ1.14 (d, JZ6.6 Hz, 6H), 3.18 (sept,
JZ6.6 Hz, 1H), 4.23 (s, 2H), 7.03 (d, JZ8.8 Hz, 1H), 7.16–
7.25 (m, 1H), 7.35–7.42 (m, 2H), 7.58–7.76 (m, 3H); 13C
NMR dZ21.32, 44.65, 51.11, 111.01, 116.64, 120.72,
120.90, 122.16, 126.16, 126.39, 127.71, 129.60, 157.22.
Exact mass calcd for C17H23NO: 257.1780. Found
257.1788.
Into a flask containing sodium (4.1 g) and pyridine (75 ml)
MeOH (75 ml) was added slowly and then CuI (11.4 g) was
added into the solution under stirring. Then 9-bromo-
phenanthrene (15.45 g) in pyridine (75 ml) was added into
the solution under heating at 80 8C. After heating for 18 h,
the reaction was quenched by 10% aqueous HCl solution
(75 ml). The extraction with Et2O of the solution gave the
crude 9-methoxyphenanthrene which was purified by
column chromatography on SiO2 and recrystallized from
MeOH (yield 86.0%, 10.7 g). The solution of acetic acid
(150 ml) of 9-methoxyphenanthrene (7.5 g) was heated at
60 8C and an aqueous solution of HBr (48%, 11.4 ml) was
added. After heating at 130 8C for 2 h, the water (150 ml)
was added, and the precipitate was obtained by filtration and
washing with water to give 9-phenanthrol in 92% yield
(6.42 g).
3.2. Preparation of BESn
Decanol (3.3 mmol) was heated with maleic anhydride
(1.5 mmol) in the presence of H2SO4 (0.1 ml) in benzene
(50 ml) at 110 8C on Dean-Stark apparatus. After the
neutralization with aqueous NaHCO3 solution, the solution
was extracted with benzene. Evaporation of the benzene
solution left the crude didecyl maleate that was purified by
the recrystallization from hexane. An aqueous solution
(50 ml) containing of NaHSO3 (17.5 g) and didecyl maleate
(1 mmol) was refluxed for 3 h under bubbling with air. After
the neutralization with NaHCO3, the solution was evapor-
ated. The resulting residue was solved into hot methanol,
and filtrated. The filtrate was evaporated to give a crude
BES10 which was purified by recrystallization from hexane.
The preparation of 1 was performed by Mannich reaction.
Into a reaction mixture of 9-phenanthrol (30 mmol, 5.82 g)
and aqueous Me2NH solution (40%, 40 mmol), a formalin
solution (37%, 30 mmol) was slowly added. After stirring at
room temperature for 18 h, the solution was extracted
with CHCl3. The evaporation of the solvent left the crude
N,N-dimethyl-9-aminomethyl-10-phenanthrol (1a) that
was subjected to column chromatography on Al2O3.
Also, N,N-diethyl-9-aminomethyl-10-phenanthrol (1b) and
N,N-dialkyl-1-aminomethyl-2-naphthols (1c–e) were
prepared according to the method to prepare 1a.
1
3.2.1. Didecyl maleate. Yield 78%. H NMR (CDCl3) dZ
0.88 (t, JZ6.9 Hz, 6H), 1.30 (br s, 28H), 1.66 (t, JZ7.0 Hz,
4H), 4.17 (t, JZ6.8 Hz, 4H), 6.23 (s, 2H).
3.2.2. Sodium 1,2-bis(decylcarbonyl)ethanesulfonate
1
(BES10).9,10 Yield 16%. H NMR (CD3OD) dZ0.89 (br t,
6H), 1.26–1.31 (m, 28H), 1.63 (br s, 4H), 3.00–3.20 (m,
2H), 4.15–4.20 (m, 5H).
3.1.1. N,N-Dimethyl-9-aminomethyl-10-phenanthrol
1
(1a). Yield 76%. H NMR dZ2.45 (s, 6H), 4.14 (s, 2H),
7.44–7.53 (m, 3H), 7.83 (d, JZ8.1 Hz, 1H), 8.38–8.42 (m,
2H), 8.61–8.66 (m, 2H); 13C NMR dZ44.73, 58.45, 106.34,
121.17, 122.21, 122.67, 122.91, 123.15, 125.81, 126.29,
126.71, 126.80, 130.81, 131.91, 152.79. Exact mass calcd
for C17H17NO: 251.1310. Found 251.1302.
In a similar manner, BES12 was prepared using dodecanol
instead of decanol.
1
3.2.3. Didodecyl maleate. Yield 18%. H NMR (CDCl3)
dZ0.88 (t, JZ6.9 Hz, 6H), 1.26 (br s, 28H), 1.60–1.75 (m,
4H), 4.17 (t, JZ6.7 Hz, 4H), 6.22 (s, 2H).
3.1.2. N,N-Diethyl-9-aminomethyl-10-phenanthrol (1b).
Yield 68%. H NMR dZ1.15 (d, JZ7.5 Hz, 3H), 2.70 (q,
1
JZ7.5 Hz, 4H), 4.23 (s, 2H), 7.40–7.61 (m, 5H), 8.37–8.41
(m, 1H), 8.61–8.66 (m, 2H); 13C NMR dZ11.23, 47.04,
52.87, 106.14, 120.93, 122.10, 122.19, 122.62, 122.69,
123.03, 125.54, 126.45, 126.63, 126.91, 127.07, 130.34,
131.85, 153.05. Exact mass calcd for C19H21NO: 279.1623.
Found 279.1549.
3.2.4. Sodium 1,2-bis(dedecylcarbonyl)ethanesulfonate
(BES12). Yield 36%. 1H NMR (CD3OD) dZ0.90 (br t, 6H),
1.30 (br s, 36H), 1.64 (br s, 4H), 3.00–3.20 (m, 2H), 4.15–
4.20 (m, 5H).
3.3. General procedure for the reaction of 1 with 2
3.1.3. N,N-Dimethyl-1-aminomethyl-2-naphthol (1c).
MeCN–H2O (6:4), DMF–H2O (6:4), MeOH–H2O (6:4), and
THF–H2O (6:4) solutions (100 ml) of 1 (1 mmol) were
bubbled with argon gas for 15 min and then 2a (15 mmol,
1.08 g) was introduced into the solution. Irradiation was
performed by an Eikosha high-pressure mercury lamp
through a Pyrex filter for 10–20 h at room temperature
1
Yield 63%. H NMR dZ2.36 (s, 6H), 4.04 (s, 2H), 7.06–
7.78 (m, 7H); 13C NMR dZ44.57, 57.79, 111.29, 119.15,
120.84, 122.74, 126.19, 128.35, 128.79, 129.10, 132.47,
156.71. Exact mass calcd for C13H15NO: 202.1154. Found
202.1165.

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J. Matsumoto et al. / Tetrahedron 61 (2005) 5735–5740
(Method A). After the photoreaction, the solvent was
evaporated from the photolysate. The crude products were
purified by a column chromatography on silica-gel to give 3.
5.45 (dd, JZ3.5, 2.6 Hz, 1H) 7.49–7.64 (m, 4H), 7.86–7.90
(m, 1H), 8.29–8.33 (m, 1H), 8.59–8.64 (m, 2H); 13C NMR
dZ17.56, 21.03, 28.88, 42.28, 70.80, 109.57, 117.31,
123.38, 123.55, 128.71, 129.92, 131.03, 133.42, 156.74.
Exact MS calcd for C21H22O2: 306.1620. Found 306.1584.
1
The structure was assigned by H NMR and MS spectra.
The 2a was purified by distillation since commercially
available 2a was stabilized by 0.1% NaOH. Under
irradiation without the remove of NaOH, 1a was turned to
9,10-phenanthrenequinone that underwent the formation of
the cycloadduct (5a) with 2a.
3.3.3. 2-(2-Hydroxyethoxy)dibenzo[f,h]chroman (3c). 1H
NMR dZ1.70 (br s, 1H), 2.20–2.35 (m, 4H), 3.10–3.20 (m,
2H), 3.65–3.74 (m, 1H), 3.80–3.92 (m, 1H), 3.96–4.08 (m,
1H), 5.54 (t, JZ3.1 Hz, 1H), 7.15–7.60 (m, 4H), 7.73–7.85
(m, 1H), 8.30–8.46 (m, 1H), 8.53–8.59 (m, 2H); 13C NMR
dZ17.96, 26.43, 61.68, 69.96, 97.64, 121.64, 122.41,
122.80, 124.23, 126.53, 126.93. Exact MS calcd for
C19H18O3: 294.1283. Found 294.1281.
In the cases of aqueous surfactant solutions, aqueous
solution (100 ml) containing 1a (1 mmol, 251 mg) and the
surfactant (SDS 30 mM, 864 mg; PED 30 mM, 1.747 g;
CTAC: 30 mM, 960 mg) was bubbled with argon gas for
30 min under cooling with ice and then 2 (15 mmol) was
introduced into the solution. Irradiation was performed, as
described above (Method A). After the irradiation, the
photolysates were extracted with CHCl3. The CHCl3
solution was washed with saturated aqueous NaCl solution
to remove the surfactant and was subjected to a column
chromatography on silica-gel to give 3a.
1
3.3.4. 2-Ethoxybenzo[f]chroman (3d). H NMR dZ1.18
(t, JZ7.5 Hz, 3H), 2.07–2.21 (m, 2H), 3.05–3.13 (m, 2H),
3.61–3.70 (m, 1H), 3.87–3.96 (m, 1H), 5.31 (t, JZ2.5 Hz,
1H), 7.06 (d, JZ8.9 Hz, 1H), 7.33 (dd, JZ6.8, 1.0 Hz, 1H),
7.48 (dd, JZ6.8, 1.3 Hz, 1H), 7.63 (d, JZ8.9 Hz, 1H), 7.82
(d, JZ5.2 Hz, 1H), 7.85 (d, JZ5.2 Hz, 1H); 13C NMR dZ
15.10, 17.43, 26.37, 29.23, 30.85, 63.75, 96.81, 114.37,
119.04, 121.95, 123.27, 126.20, 127.66, 128.33, 129.25.
Exact mass calcd for C15H16O2: 228.1150. Found 228.1148.
For the case of BESn, BESn (0.1–10 mmol, 0.05–5 g for
BES10, 0.056–5.6 g for BES12) was solved in MeOH and
heated at 40 8C and then cooled to room temperature. After
the addition of 1 (0.1 mmol), MeOH was removed by a
rotary evaporator to produce a thin film of BESn and then
the film was dried in vacuo. The BESn film containing 1 was
suspended in water (10 ml) and the solution was sonicated at
30 8C for 10 min, giving clear (w1 mM for BESn) to
slightly turbid (O 5 mM for BESn) solutions. The obtained
solution was bubbled with argon gas for 30 min. After 2a
(1.5 mmol) was introduced into the solution, irradiation was
performed. The follow-up process was similar to the method
described above.
References and notes
1. Van De Water, R. W.; Petus, T. R. R. Tetrahedron 2002, 58,
5367.
2. Diao, L.; Yang, C.; Wan, P. J. Am. Chem. Soc. 1995, 117,
5369.
3. Foster, L. L.; Baker, S.; Brousmiche, D. W.; Wan, P.
J. Photochem. Photobiol. A Chem. 1999, 129, 157.
4. Kalanderopoulos, P.; Yates, K. J. Am. Chem. Soc. 1986, 108,
6290.
The thermal reactions of 1 with 2a were performed for a
solution (50 ml) containing 1 (0.2 mmol) and 2a (3.0 mmol)
at bath temperature at 50 8C for 3 h (Method B).
5. Yasuda, M.; Sone, T.; Tanabe, K.; Shima, K. J. Chem. Soc.,
Perkin Trans. 1 1995, 459.
1
3.3.1. 2-Ethoxydibenzo[f,h]chroman (3a). H NMR dZ
6. Nakatani, K.; Higashida, N.; Saito, I. Tetrahedron Lett. 1997,
38, 5005.
1.14 (t, JZ7.2 Hz, 3H), 2.12–2.26 (m, 4H), 2.90–3.18 (m,
2H), 3.60–3.78 (m, 1H), 3.88–4.00 (m, 1H), 5.41 (t, JZ
2.6 Hz, 1H), 7.15–7.60 (m, 4H), 7.73–7.85 (m, 1H), 8.30–
8.46 (m, 1H), 8.53–8.59 (m, 2H). 13C NMR dZ15.15,
18.13, 26.56, 63.94. 97.09, 121.79, 122.37, 122.37, 122.72,
124.00, 126.38, 126.38, 126.84, 130.51, 130.82, 131.53,
131.84, 144.80, 152.50. Exact MS calcd for C19H18O2:
278.1307. Found 278.1304.
7. Modica, E.; Zanaletti, R.; Freddero, M.; Mella, M. J. Org.
Chem. 2001, 66, 41.
8. von Strandtmann, M.; Cohen, M. P.; Shavel, J., Jr. J. Org.
Chem. 1965, 30, 3240.
9. Kunitake, T.; Okahata, Y. Bull. Chem. Soc. Jpn. 1978, 51,
1877.
10. Ueno, M.; Kishimoto, H.; Kyogoku, Y. Chem. Lett. 1977, 599.
11. Yasuda, M.; Nishinaka, Y.; Nakazono, T.; Hamasuna, T.;
Nakamura, N.; Shiragami, T.; Pac, C.; Shima, K. Photochem.
Photobiol. 1998, 67, 192.
3.3.2. 2-Isobutoxydibenzo[f,h]chroman (3b). 1H NMR
dZ0.78 (d, JZ6.7 Hz, 3H), 0.83 (d, JZ6.7 Hz, 3H), 1.83
(d, JZ6.7 Hz, 1H), 2.13–2.31 (m, 2H), 2.99–3.16 (m, 2H),
3.43 (dd, JZ9.4, 6.7 Hz, 1H), 3.67 (dd, JZ9.5, 6.7 Hz, 1H),
12. Yasuda, M.; Nakai, T.; Kawahito, Y.; Shiragami, T. Bull.
Chem. Soc. Jpn. 2003, 76, 601.