Intramolecular 10,10a-[2+2] photocycloaddition reactions of phenanthrenes with linked styrene

Article abstract of DOI:10.1016/j.jphotochem.2016.07.001

Intramolecular photocycloaddition reactions of styrene linked 9-cyanophenanthrenes led to formation of C-9 C-10 [2+2] cycloadducts which underwent cycloreversion under the prolonged irradiation conditions to regenerate the starting substrates. Unusual 8-membered ring products were irreversibly formed in these processes. Product distributions were governed by substituent controlled, donor-acceptor interactions that direct generation of two intramolecular singlet exciplexes, which serve as intermediates in the pathways to formation of 9,10- and 10,10a-[2+2] adducts.

Full text of DOI:10.1016/j.jphotochem.2016.07.001

Journal of Photochemistry and Photobiology A: Chemistry 329 (2016) 232–237
Contents lists available at ScienceDirect
Journal of Photochemistry and Photobiology A:
Chemistry
journal homepage: www.elsevier.com/locate/jphotochem
Intramolecular 10,10a-[2+2] photocycloaddition reactions of
phenanthrenes with linked styrene
1
Hajime Maeda*, Ryota Nakashima, Akira Sugimoto , Kazuhiko Mizuno**
Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
A R T I C L E I N F O
A B S T R A C T
Article history:
Received 30 May 2016
Received in revised form 29 June 2016
Accepted 1 July 2016
Intramolecular photocycloaddition reactions of styrene linked 9-cyanophenanthrenes led to formation of
C-9 C-10 [2+2] cycloadducts which underwent cycloreversion under the prolonged irradiation conditions
to regenerate the starting substrates. Unusual 8-membered ring products were irreversibly formed in
these processes. Product distributions were governed by substituent controlled, donor-acceptor
interactions that direct generation of two intramolecular singlet exciplexes, which serve as intermediates
in the pathways to formation of 9,10- and 10,10a-[2+2] adducts.
Available online 2 July 2016
Keywords:
Photocycloaddition
Phenanthrene
Styrene
ã 2016 Elsevier B.V. All rights reserved.
Exciplex
Eight membered ring product
1. Introduction
cycloadducts [41]. However, until now no photocycloaddition
reactions of alkenes taking place at the 10,10a-position of
Photocycloaddition reactions between arenes and unsaturated
compounds represent powerful methods for the construction of
polycyclic compounds [1–3]. Although many stereo- and regio-
specific photocycloaddition reactions of alkenes with phenan-
threnes and naphthalenes have been described, the sites at which
reactions have been observed to take place are limited to the 9,10-
positions of phenanthrenes [4–22], and the 1,2- and 1,4-positions
of naphthalenes [23–38]. The ability to alter the arene sites at
which photocycloaddition reactions occur should greatly benefit
the synthetic potential of these processes and enhance the
understanding of the structures and reactivities of exciplexes that
are intermediates in these reactions.
phenanthrene have been observed, although the corresponding
1.8a-addition of naphthalene has been observed [42–44]. Based on
the fact that intramolecular photochemical reactions are often
both highly efficient and stereoselective, we have recently
designed linked alkene-naphthalene substances that undergo
intramolecular photocycloaddition at the 1,3-position of the
naphthalene ring [45], and also observed that efficient, site-
selective photocycloaddition reactions occur in alkene-pyrene
linked systems [46]. In the effort described below, we have
uncovered an unprecedented intramolecular photocycloaddition
process that transforms tethered phenanthrene-styrene substrates
to unexpected eight-membered ring products along with normal
9,10-[2+2] cycloadducts. The former process takes place via an
initial and unusual 10,10a-[2+2] photocycloaddition reaction
which produces a cycloadduct that undergoes thermal electro-
cyclic ring opening to generate the observed eight membered ring
product.
Earlier, Kubo et al. uncovered an unusual intermolecular [3+2]
photocycloaddition reaction of alkenes to naphthalene that result
in the formation of 1,8-adducts [39,40], and later discovered
photoprocesses that lead to generation of 8,9-phenanthrene
2
. Results and discussion
*
Corresponding author. Present address: Division of Material Chemistry,
Graduate School of Natural Science and Technology, Kanazawa University,
Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan.
Irradiation of a benzene solution containing 9-cyano-10-
phenanthrylmethyl cinnamyl ether (trans-1a) in a Pyrex vessel
(>280 nm light) under an argon atmosphere by using a high-
pressure mercury lamp gave rise to efficient formation of two
cycloadducts 2a and 3a (Scheme 1). These products were isolated
by using silica gel column chromatography. The structures of the
photoproducts were first assigned by using spectroscopic methods
** Corresponding author. Present address: Graduate School of Materials Science,
Nara Institute of Science and Technology (NAIST), 8916-5, Takayama-cho, Ikoma,
Nara 630-0192, Japan.
E-mail addresses: maeda-h@se.kanazawa-u.ac.jp (H. Maeda),
kmizuno@ms.naist.jp (K. Mizuno).
1
Present address: The Institute of Scientific and Industrial Research (SANKEN),
Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
http://dx.doi.org/10.1016/j.jphotochem.2016.07.001
1010-6030/ã 2016 Elsevier B.V. All rights reserved.

H. Maeda et al. / Journal of Photochemistry and Photobiology A: Chemistry 329 (2016) 232–237
233
Scheme 1. Intramolecular Photocycloaddition of 9-Cyano-10-phenanthrylmethyl
Cinnamyl Ether (trans-1a).
and then unambiguously determined by using X-ray crystallo-
graphic analysis (Figs. 1 and 2). The cyclobutane ring containing
product 2a is an expected result of intramolecular [2+2] photo-
cycloaddition of the styrene moiety at the reactive 9,10-positions
of the phenanthrene group. In contrast, product 3a is unusual in
that it contains an eight-membered ring whose origin is
interesting.
Substituents on the styrene and phenanthrene groups were
found to govern the distribution of products produced in this
process (Scheme 2, Table 1). Intramolecular [2+2] photocycload-
dition proceeded when a solution of the 6-cyano derivative trans-
1b was photoirradiated, but the eight-membered ring product 3b
was not generated (entries 5 and 6). Photoreaction of trans-1c, a
substance that does not have a 9-cyano substituent on the
phenanthrene ring, did not react to yield 3c, but it slowly was
transformed to 2c along with the isomerized reactant cis-1c
Fig. 2. ORTEP drawing of 3a. C25
b = 12.740(4) Å, c = 14.430(7) Å,
R = 0.040, R = 0.041, GOF = 1.827.
H
19NO, monoclinic, P2
1
/n (#14), Z = 4, a = 9.934(4) Å,
(
entries 7 and 8). In addition, the p-methoxy- and 9-cyano
ꢀ
3
b
= 96.18(4) ,
Dcalcd = 1.278 g/cm ,
m= 0.773,
substituted substrate trans-1d photoreacted to afford 2d exclu-
sively (entries 9 and 10). Moreover, the substrate trans-1e,
w
possessing cyano groups at both the para and 9-positions
underwent efficient reaction to produce the eight-membered ring
product 3e (entries 11–13). Finally, the p-cyano, 9-cyano, and 3-
methoxy substituted derivative trans-1f participated in high
yielding photoreaction to form the eight-membered ring adduct
3
f exclusively (entry 14).
The results of a study of product distributions as a function of
reactant conversion showed that 2a was formed at the initial stage
of the photoreaction (10 min) of trans-1a to the total exclusion of
Fig. 1. ORTEP drawing of 2a. C25
2) Å, b = 15.428(3) Å, c = 16.707(2) Å,
R = 0.045, R = 0.049, GOF = 1.883.
1
H19NO, monoclinic, P2 /c (#14), Z = 8, a = 15.526
b= 113.092(7) , Dcalcd = 1.261 g/cm , m= 0.763,
ꢀ
3
(
Scheme 2. Intramolecular Photocycloaddition Reactions of Linked Styrene-
Phenathrenes.
w

2
34
H. Maeda et al. / Journal of Photochemistry and Photobiology A: Chemistry 329 (2016) 232–237
Table 1
The relative intensities of the fluorescence bands of trans-1a
and trans-1c in cyclohexane were smaller than those of phenan-
threne and 9-cyanophenanthrene (Fig. 4). This observation is a
consequence of intramolecular quenching of the singlet phenan-
threne excited state by the cinnamyl group. In the fluorescence
spectra of trans-1a and trans-1c, weak intramolecular exciplex
emissions were observed. Fluorescence lifetime measurements
with trans-1a in cyclohexane, by using single photon counting,
showed that a major short-lived, transient (<2 ns) was produced,
which assigned to the 9-cyanophenanthrene singlet, and a minor
long-lived (15 ns) transient corresponding to the singlet exciplex
was also formed.
The observations described above have led to the plausible
mechanism for these photoreactions given in Scheme 3. Two
sandwich-type intramolecular singlet exciplexes, 4 and 5, pro-
duced via phenanthrene excited singlet states, are postulated to
serve as reactive intermediates in these photoreactions. The
normal [2+2] photocycloadducts 2 are produced by cycloaddition
in the exciplexes 4 whereas exciplexes 5 react to generate the
strained 10,10a-[2+2] photocycloadducts 6. Thermal electrocyclic
ring opening of 6 then affords the 8-membered ring products 3. Cis/
trans isomerization of the styrene moiety in the reactants might
take place by way of reversible formation and cycloreversion of 2.
The donor-acceptor effects caused by substituents on the nature
of this process are interesting. Compared to the phenyl group in
trans-1a, that of trans-1b should more favor overlap with the
phenanthrene A ring owing to the presence of the 6-cyano group.
In the unsubstituted substrate, trans-1c, the formation of a singlet
exciplex is less advantageous because of donor-acceptor inter-
actions, a proposal that is supported by the observation that this
substance displays a lower degree of intramolecular fluorescence
quenching than that of its analogs. The importance of the donor-
acceptor interactions between the styrene aryl group and the
phenanthrene A or C rings is also demonstrated by the results of
photoreactions of trans-1d and trans-1e. Specifically, the obser-
vations are consistent with the proposal that the electron-rich aryl
group in trans-1d tends to interact more strongly with the
electron-poor A ring in phenanthrene, whereas the electron poor
aryl group in trans-1e in contrast interacts more favorably with the
C ring.
Effects of Substituents and Irradiation Time on the Intramolecular Photocycloaddi-
tion Reactions of Linked Styrene-Phenathrenes.a
Entry
1
Irradiation time Yields (%)
R1 R2 R3
R4
2
3
cis-1b
78 trc
89
1
2
3
4
5
6
7
8
9
trans-1a CN
trans-1a CN
trans-1a CN
trans-1a CN
trans-1b
trans-1b
trans-1c
trans-1c
trans-1d CN
trans-1d CN
trans-1e CN
trans-1e CN
trans-1e CN
trans-1f CN
H
H
H
H
CN
CN
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
10 min
1 h
0
0
0
0
0
0
11
20
0
0
0
0
0
3
12 h
24 h
83 10
47 46
H
H
H
H
10 min
12 h
10 min
1 h
66
80
13
21
79
0
0
0
0
0
OMe 10 min
OMe 12 h
c
1
0
90 tr
79
1
1
CN
CN
CN
10 min
1 h
12 h
3 h
3
1
2
74 21
c
1
3
tr >98
14
H
OMe CN
0
>98
0
a
The photoreaction of trans-1 (0.03 mmol) (> 280 nm light using Pyrex vessel)
was carried out in benzene-d (0.6 mL) under argon atmosphere. The yields were
6
1
determined by H NMR spectra.
b
cis-isomer of trans-1.
Trace.
c
3a, but at longer irradiation times its yield decreased and that of 3a
increased (Table 1, entries 1–4). Monitoring the course of this
reaction by using UV absorption spectroscopy showed that a
simultaneous decrease and increase in the respective bands of
trans-1a and 2a took place associated with the appearance of
isosbestic points (Fig. 3). Importantly, 2a was found to undergo
cycloreversion to form trans-1a under the reaction conditions, but
the eight membered ring product 3a did not, thus explaining
observations made in exploring the irradiation time course of this
process.
Cycloadducts 2a and 3a were not produced when 0.1 mol/dm3
of Michler’s ketone (E
sensitizer in the photoreaction mixture (E
threne) = 243 kJ/mol [48]) and the cycloaddition reaction was
not quenched by addition of 0.5 mol/dm of the triplet quenchers
T
= 275 kJ/mol [47]) was included as a triplet
(9-cyanophenan-
T
3
T
2-methyl-1,3-butadiene (E = 251 kJ/mol [47]) and dioxygen.
The proposals offered above have prompted the design of a
substrate that would be more likely to undergo the 10,10a- rather
than 9,10-[2+2] photocycloaddtion. This substance, trans-1f,
contains electron withdrawing cyano groups at C-9 of the
phenanthrene and the para position of the benzene ring and an
electron donating methoxy group in the phenanthrene C-ring. As
Fig. 3. Time-dependent UV absorption spectra in the intramolecular photocy-
cloaddition of trans-1a in cyclohexane.
Fig. 4. Fluorescence spectra of (a) 9-cyanophenanthrene and trans-1a, (b)
phenanthrene and trans-1c, in cyclohexane (1 ꢁ10 M).
ꢂ5

H. Maeda et al. / Journal of Photochemistry and Photobiology A: Chemistry 329 (2016) 232–237
235
Scheme 3. Proposed Mechanism for Intramolecular Photocycloadditions in Linked Phenanthrene-Styrene Systems.
described above, photoreaction of this substance yields the eight-
membered ring product 3f exclusively (Table 1, entry 14).
and expanded by using Fourier techniques. Calculations were
performed using the Texsan or Crystal Structure crystallographic
software packages.
3
. Conclusion
0
4
.2. Preparation of 9-cyano-10-phenanthrylmethyl trans-3 -phenyl-
0
Although many intermolecular [4–18] and intramolecular
2 -propenyl ether (trans-1a)
[
19–22] photocycloaddition reactions of alkenes taking place at
the 9,10-position of phenanthrenes have been reported, those
that take place at the 10,10a-position have not been described
previously. Thus, the photochemical processes described above
are unique in that they demonstrate the operation of a new type
of excited state reaction that invloves cycloaddition across the
To a THF (100 mL) solution of 9-bromophenanthrene (7.72 g,
30.03 mmol) was slowly added n-BuLi (1.6 M hexane solution,
ꢀ
20 mL) at ꢂ70 C under argon atmosphere and stirred for 1 h. MeI
(21.318 g, 150.13 mmol) was slowly added and warmed to room
temperature. H
layer was dried over Na
Recrystallization from CH
threne (5.049 g, 88% yield). Colorless solid; H NMR (CDCl
270 MHz) 2.72 (s, 3H), 7.52–7.66 (m, 5H), 7.80 (m, 1H), 8.05 (m,
H), 8.71 (m, 2H) ppm. To CCl (40 mL) solution of 9-
2
O and Et
SO
Cl
2
O were added and shaken. The organic
, filtered, and concentrated in vacuo.
–n-hexane gave 9-methylphenan-
10,10a-positions of phenanthrene. Moreover, the results of this
2
4
effort show that the direction of the reaction pathway to the 9,10
or 10,10a position can be controlled by the substituent effects in
singlet intramolecular exciplexes.
2
2
1
3
,
d
1
a
4
4
. Experimental
methylphenanthrene (13.00 g, 67.6 mmol) was slowly added
ꢀ
CCl
stirred for 2 h. H
organic layer was dried over Na
vacuo. Recrystallization from CH
methylphenanthrene (15.03 g, 82% yield).
4
(20 mL) solution of Br
2
(11.88 g, 74.4 mmol) at 0 C and
4.1. Materials and equipment
2
O then 10% NaOH aq were added and shaken. The
SO , filtered, and concentrated in
Cl –n-hexane gave 9-bromo-10-
2
4
CH
3
CN was distilled from CaH
and then from Na. THF was distilled from
and then from Na/benzophenone. CH Cl was distilled from
. N-Bromosuccinimide was recrystallized from hot H O. CCl
2
and then from P
2
O
5
. Benzene
2
2
1
was distilled from P
CaH
CaH
2
O
5
H
NMR (CDCl
2.95 (s, 3H), 7.61–8.69 (m, 8H) ppm. A CCl (60 mL)
of 9-bromo-10-methylphenanthrene (16.469 g,
3
,
2
2
2
2
270 MHz)
solution
d
4
2
4
,
1
hexane, and N-methylpyrrolidone were used as purchased. H and
59.634 mmol), N-bromosuccinimide (11.147 g, 60.4 mmol), benzoyl
peroxide (catalytic amount) was stirred under reflux for 1 h. Float
colorless solid was removed by filtration. 10% NaOH aq was added
13
C NMR spectra were recorded using a JEOL JNM-GX270 (270 MHz
and 68 MHz, respectively) or a Varian MERCURY-300 (300 MHz and
5 MHz, respectively) spectrometers with Me Si as an internal
7
4
to the filtrate and shaken. The organic layer was dried over Na
filtered, and concentrated in vacuo. Recrystallization from CH
2
SO
4
,
–
standard. IR spectra were determined using a Jasco FT/IR-230
2
Cl
2
spectrometer. UV–vis spectra were recorded using a Shimadzu UV-
n-hexane
gave
9-bromo-10-(bromomethyl)phenanthrene
1
160A spectrophotometer. Fluorescence spectra were recorded
(17.645 g, 83% yield). Yellow solid; H NMR (CDCl , 270 MHz) d
3
using a Jasco FP-770 spectrophotometer. Mass spectra (EI) were
taken on a SHIMADZU GCMS-QP5050 operating in the electron
impact mode (70 eV) equipped with GC-17A and DB-5MS column
5.31 (s, 2H), 7.66-8.74 (m, 8H) ppm. 60% NaH (1.53 g, 38.4 mmol) in
oil was washed with distilled hexane and THF (10 mL) was added.
To the suspension, THF (50 mL) solution of cinnamyl alcohol
(3.43 g, 25.58 mmol) was slowly added under argon atmosphere.
The solution was refluxed for 1 h, then cooled to room tempera-
ture. THF (60 mL) solution of 9-bromo-10-(bromomethyl)phenan-
threne (4.48 g, 12.8 mmol) was slowly added. The solution was
(
J&W Scientific Inc., Serial: 8696181). HPLC separations were
performed on a recycling preparative HPLC equipped with Jasco
PU-986 pump, Shodex RI-72 differential refractometer, Megapak
GEL 201Cp and 201CP columns (GPC) using CHCl
Column chromatography was conducted by using Wako-gel C-70-
30 and C-300. X-ray crystallographic data for a single crystals
were obtained using a Rigaku AFC5 R or Rigaku RAXIS RAPID
imaging plate area detector with graphite monochromated Mo-K
radiation. The structures were solved by direct methods (SIR92)
3
as an eluent.
refluxed for 2 h, then cooled to room temperature. H
were added and shaken. The organic layer was dried over Na
filtered, and concentrated in vacuo. Separation of the residue by
column chromatography on silica gel (eluent; n-hexane : CH Cl
1 : 1) followed by recrystallization from CH Cl –n-hexane gave
2
O and Et
2
O
2
2
4
SO ,
a
2
2
=
2
2

2
36
H. Maeda et al. / Journal of Photochemistry and Photobiology A: Chemistry 329 (2016) 232–237
0
0
9
-bromo-10-phenanthrylmethyl
trans-3 -phenyl-2 -propenyl
(m, 2H), 7.39–7.42 (m, 2H), 7.64–7.73 (m, 4H), 8.33–8.36 (m, 1H),
1
13
ether (2.73 g, 53% yield). Colorless solid;
H
NMR (CDCl
3
,
8.52–8.55 (m, 1H), 8.67–8.71 (m, 2H) ppm; C NMR (CDCl
3
,
2
1
8
70 MHz)
d
4.35 (d, J = 6.0 Hz, 2H), 5.42 (s, 2H), 6.34–6.40 (m,
75 MHz) 70.4, 70.5, 121.3, 122.5, 122.7, 122.8, 125.8, 126.5, 126.8,
d
H), 6.66 (d, J = 16.5 Hz, 1H), 7.22–7.40 (m, 5H), 7.66-7.74 (m, 4H),
.34–8.37 (m, 1H), 8.52–8.56 (m, 1H), 8.67–8.72 (m, 2H) ppm. A
126.9, 127.4, 127.5, 127.9, 129.4, 129.8, 130.2, 131.2, 131.4, 131.5,
131.9, 135.6 ppm. Reaction of this compound with CuCN (15 equiv)
was carried out under similar conditions described above.
0
0
mixture of 9-bromo-10-phenanthrylmethyl trans-3 -phenyl-2 -
propenyl ether (3.09 g, 7.64 mmol), N-methylpyrrolidone (9 mL),
CuCN (2.05 g, 23.1 mmol) was stirred at 180 C for 20 min to give
black suspension. NH
temperature and the mixture was filtered by suction filtration
with CH Cl . H O was added and shaken. The organic layer was
dried over Na SO , filtered, and concentrated in vacuo. N-
methylpyrrolidone was removed by distillation under reduced
pressure. Separation of the black residue by column chromatog-
Purification by column chromatography on silica gel (eluent; n-
ꢀ
0
hexane–CH
2
Cl
2
0
) gave 9-cyano-10-phenanthrylmethyl trans-3 -p-
1
3
aq (231 mmol) was added at room
cyanophenyl-2 -propenyl ether (trans-1e) in 26% yield. H NMR
3
(CDCl , 300 MHz) d 4.37 (dd, J = 5.8, 1.4 Hz, 2H), 5.38 (s, 2H), 6.42
2
2
2
(dt, J = 15.9, 5.8 Hz, 1H), 6.69 (d, J = 15.9 Hz, 1H), 7.42 (d, J = 8.3 Hz,
2H), 7.57 (d, J = 8.3 Hz, 2H), 7.75–7.86 (m, 4H), 8.34–8.38 (m, 1H),
8.42–8.46 (m, 1H), 8.70–8.77 (m, 2H) ppm.
2
4
raphy on silica gel (eluent; n-hexane : CH
2
Cl
2
= 1 : 1) followed by
4.4. Preparation of 9-cyano-6-methoxy-10-phenanthrylmethyl trans-
3 -p-cyanophenyl-2 -propenyl ether (trans-1f)
0
0
recrystallization from CH
thrylmethyl trans-3 -phenyl-2 -propenyl ether (trans-1a, 1.87 g,
2
Cl
2
–n-hexane gave 9-cyano-10-phenan-
0
0
ꢀ
1
70% yield). Yellow solid; mp 107–108 C; H NMR (CDCl
3
, 270 MHz)
To a mixture of Mg (3.65 g, 150 mmol) in THF (10 mL) was
d
4.34 (dd, J = 6.1, 1.2 Hz, 2H), 6.34 (dt, J = 15.9, 6.1 Hz, 1H), 6.68 (d,
added THF (50 mL) solution of PhCH
2
Cl (12.66 g, 100 mmol)
ꢀ
J = 15.9 Hz, 1H), 7.22–7.40 (m, 5H), 7.73–7.82 (m, 4H), 8.33–8.38 (m,
1
dropwisely for 2 h at 0 C under argon atmosphere. The solution
was warmed to room temperature and stirred for 1.5 h. THF
(10 mL) solution of p-methoxyacetophenone (11.25 g, 75 mmol)
H), 8.41–8.45 (m, 1H), 8.67–8.74 (m, 2H) ppm; IR (KBr)
n
968,
ꢂ1
1114, 1449, 1685, 2221, 2878, 3026 cm ; MS (EI) m/z 105, 115, 133,
+
189, 217, 305, 349 (M ).
was dropwisely added for 30 min, and the solution was stirred for
ꢀ
additional 1 h. Sat NH
The organic layer was washed with H
dried over Na SO , filtered, and concentrated in vacuo. To the
4
Cl aq was poured into the solution at 0 C.
0
4
.3. Preparation of 9-cyano-10-phenanthrylmethyl trans-3 -p-
2
O then brine, separated,
0
cyanophenyl-2 -propenyl ether (trans-1e)
2
4
yellow residue was added benzene and p-TsOH (catalytic amount),
and the solution was refluxed by a Dean-Stark apparatus until the
3
To a benzene (100 mL) solution of PPh (5.24 g, 20.0 mmol) was
slowly added methyl bromoacetate (3.06 g, 20.0 mmol), and
stirred for 10 min. The white suspension was stirred for additional
production of H
2
O ceased. Purification by column chromatography
on silica gel gave (E)-1-methyl-1-p-methoxyphenyl-2-phenyl-
ethene (6.36 g, 38% yield). H NMR (CDCl , 300 MHz) d 2.26 (s,
3
1
2
h. The white solid was collected by suction filtration, and
washed with benzene (20 mL) twice. The solid was dried under
reduced pressure, and then dissolved in deionized water in
saturated concentration. Phenolphthalein solution (1 drop) was
added and 2 M NaOH aq was slowly added to give white solid until
the color turned to pale pink. The solid was collected by suction
filtration and washed with deionized water (30 mL) twice. The
white solid was dried under reduced pressure for 2 days to give
3H), 3.84 (s, 3H), 6.78 (s, 1H), 6.93 (dd, J = 6.9, 2.3 Hz, 2H), 7.19–7.26
(m, 2H), 7.35–7.37 (m, 3H), 7.46–7.49 (m, 2H) ppm. A benzene
(200 mL) solution of (E)-1-methyl-1-p-methoxyphenyl-2-phenyl-
ethene (2.5 g, 11.2 mmol) and I
with O . The vessel was sealed, and irradiated by 300 W high
pressure mercury lamp for 3 days. 10% Na aq (100 mL) was
added and shaken. The organic layer was washed with H O,
separated, dried over Na SO , filtered, and concentrated in vacuo.
Purification by column chromatography on silica gel (eluent; n-
hexane benzene = 3 1, Rf = 0.72) followed by recycling
preparative HPLC (GPC, eluent; CHCl gave 3-methoxy-10-
methylphenanthrene (1.45 g, 59% yield). Mp 55.5–56.5 C;
NMR (CDCl , 300 MHz) 2.71 (s, 3H), 4.03 (s, 3H), 7.30 (dd, J = 9.0,
2
(catalytic amount) was bubbled
2
2 2 3
S O
2
Ph
solution of p-bromobenzaldehyde (2.78 g, 15.0 mmol) was slowly
added CH Cl (30 mL) solution of Ph P=CHCO Me (5.51 g,
6.5 mmol) under argon atmosphere at 0 C, and stirred for 1 h.
The solvent was removed in vacuo. Small amount of CH Cl was
added to the oily residue. Et O was added to the stirred solution,
and the precipitate was removed. The Et O solution was washed
with H O. The organic layer was dried over Na SO , filtered, and
3
P=CHCO
2
Me (5.51 g, 83% yield). To a dry CH
2
Cl
2
(20 mL)
2
4
2
2
3
ꢀ
2
:
:
1
3
)
ꢀ
1
2
2
H
2
3
d
2
2.5 Hz, 1H), 7.45 (s, 1H), 7.54–7.57 (m, 2H), 7.77–7.80 (m, 1H), 8.00
(d, J = 9.1 Hz, 1H), 8.10 (d, J = 2.7 Hz, 1H), 8.55–8.60 (m, 1H) ppm. A
2
2
4
concentrated in vacuo. Purification by column chromatography on
silica gel (eluent; n-hexane : EtOAc = 4 : 1, Rf = 0.65) gave methyl
trans-3-(p-bromophenyl)acrylate (3.60 g, 94% yield). H NMR
CCl
4
(5 mL) solution of 3-methoxy-10-methylphenanthrene
(36.5 mg, 0.164 mmol) was added CCl
4
(10 mL) solution of Br
2
1
ꢀ
(23.6 mg, 0.148 mmol) at ꢂ10 C, and stirred for 30 min. After the
(
2
(
CDCl
H), 7.42 (m, 2H), 7.57 (d, J = 15.9 Hz, 1H) ppm. To a dry toluene
25 mL) solution of trans-3-(p-bromophenyl)acrylate (6.82 g,
3
, 270 MHz)
d
3.75 (s, 3H), 6.45 (d, J = 15.9 Hz, 1H), 7.31 (m,
solution was warmed to room temperature, 10% NaOH aq (5 mL)
was added. The organic layer was washed with H
dried over Na SO , filtered, and concentrated in vacuo to give 9-
2
O, separated,
2
4
2
8.2 mmol) was slowly added i-Bu
2
AlH (1.5 M toluene solution,
bromo-3-methoxy-10-methylphenanthrene (40.1 mg, 90% yield).
ꢀ
ꢀ
3
7.6 mL) at ꢂ78 C. The solution was warmed to room temperature
Notice! When this reaction was carried out at 0 C, bromination
1
and stirred for 3 h. 2 N HCl aq (15 mL) was added. The mixture was
shaken, and organic layer was extracted. The aqueous phase was
occurred at 2-position. H NMR (CDCl
3
, 300 MHz)
d
2.91 (s, 3H),
4.00 (s, 3H), 7.22–7.26 (m, 2H), 7.55–7.67 (m, 2H), 8.00–8.04 (m,
2H), 8.41–8.45 (m, 1H), 8.53–8.56 (m, 1H) ppm. A CCl (10 mL)
washed with CH
2
Cl
2
. The combined organic phase was dried over
4
Na SO , filtered, and concentrated in vacuo. Purification by column
2
4
solution of 9-bromo-3-methoxy-10-methylphenanthrene (0.05 g,
0.166 mmol), N-bromosuccinimide (0.0295 g, 0.166 mmol), benzo-
yl peroxide (catalytic amount) was stirred under reflux for 40 min.
Float colorless solid was removed by filtration. 10% NaOH aq was
added to the filtrate and shaken. The organic layer was dried over
chromatography on silica gel (eluent; n-hexane : EtOAc = 4 : 1, then
MeOH) gave trans-3-p-bromophenyl-2-propen-1-ol (5.89 g, 98%
yield). Reaction of the alcohol with NaH and 9-bromo-10-
(
bromomethyl)phenanthrene was carried out under similar
conditions described above to give 9-bromo-10-phenanthryl-
Na
CH
phenanthrene (57 mg, 89% yield). Colorless solid; H NMR (CDCl
300 MHz) 4.03 (s, 3H), 5.26 (s, 2H), 7.32–7.36 (m, 1H), 7.66–7.70
2
SO
4
, filtered, and concentrated in vacuo. Recrystallization from
0
0
methyl trans-3 -p-bromophenyl-2 -propenyl ether in 45% yield.
2
Cl
2
–n-hexane gave 9-bromo-10-bromomethyl-3-methoxy-
1
1
H NMR (CDCl
3
, 300 MHz)
d
4.33 (dd, J = 5.8, 1.3 Hz, 2H), 5.42 (s,
3
,
2H), 6.37 (dt, J = 15.9, 5.8 Hz, 1H), 6.62 (d, J = 15.9 Hz, 1H), 7.20–7.26
d

H. Maeda et al. / Journal of Photochemistry and Photobiology A: Chemistry 329 (2016) 232–237
237
(
m, 2H), 8.05–8.06 (m, 1H), 8.13 (d, J = 9.1 Hz, 1H), 8.45–8.49 (m,
128.0, 128.6, 129.2, 130.9, 131.7, 133.4, 133.6, 138.4, 140.6, 142.3,
ꢂ1
1
2
5
H), 8.55–8.58 (m, 1H) ppm. Reaction of this compound (0.90 g,
.37 mmol) with trans-3-p-bromophenyl-2-propen-1-ol (1.26 g,
.92 mmol) was carried out under similar conditions described
143.6, 165.1 ppm; IR (KBr)
n
1064, 1438, 1483, 2213, 2875 cm
.
Acknowledgements
above, by using 60% NaH (0.24 g, 5.92 mmol) and dry THF (40 mL).
Purification by column chromatography on silica gel (eluent;
benzene : n-hexane = 1 : 1, Rf = 0.5) gave 9-bromo-3-methoxy-10-
This study was partially supported financially by Grants-in-Aid
for Scientific Research (B) (10044091 to K. M.), Scientific Research
(C) (23550058 to K. M., 20550049, 23550047, 26410040 to H. M.),
Grant-in-Aid for Young Scientists (13750791 to H. M.) from the
Ministry of Education, Culture, Sports, Science, and Technology
(MEXT) of Japan. H. M. is grateful for financial support from
Mitsubishi Chemical Corporation Fund, The Mazda Foundation,
and Kanazawa University SAKIGAKE Project.
0
0
phenanthrylmethyl trans-3 -p-bromophenyl-2 -propenyl ether
1
(
4
6
0.78 g, 64% yield). H NMR (CDCl
3
, 300 MHz)
.30 (dd, J = 6.1,1.4 Hz, 2H), 5.38 (s, 2H), 6.36 (dt, J = 15.9, 6.1 Hz,1H),
.61 (d, J = 15.9 Hz, 1H), 7.19–7.42 (m, 5H), 7.66–7.70 (m, 2H), 8.04
d 4.02 (s, 3H),
(
1
m, 1H), 8.27 (d, J = 9.0 Hz, 1H), 8.49–8.52 (m, 1H), 8.57–8.60 (m,
H) ppm. Reaction of this compound with CuCN was carried out
under similar conditions described above to give 9-cyano-6-
0
0
methoxy-10-phenanthrylmethyl trans-3 -p-cyanophenyl-2 -pro-
penyl ether (trans-1f). 1H NMR (CDCl
, 300 MHz) 4.06 (s, 3H),
.35 (dd, J = 5.6, 1.5 Hz, 2H), 5.34 (s, 2H), 6.41 (dt, J = 15.9, 5.8 Hz,
H), 6.68 (d, J = 15.9 Hz, 1H), 7.36 (dd, J = 9.1, 2.5 Hz, 1H), 7.41 (d,
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1
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2
f
[
(
6
5
tube (f
[
[
[
1
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[
(
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0
3
,3a,4,4a-tetrahydro-1H-phenanthro[9 ,10 :1,4]cyclobuta[1,2-c]fu-
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1
1
(
[
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13
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d
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d
50.6, 55.0, 70.8, 73.2, 105.7, 116.2, 126.5, 126.5, 126.6, 127.5, 127.6,
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