Construction of polyaromatics via photocyclization of 2-(fur-3-yl) ethenylarenes, using a 3-furyl group as an isopropenyl equivalent synthon

Article abstract of DOI:10.1016/j.tet.2014.01.035

The construction of different types of substituted arenes was demonstrated through the photocyclization of 2-(fur-3-yl)ethenylarenes using a 3-furyl group as an isopropenyl equivalent synthon in the photocyclization reaction. The furan portion of the photocyclization intermediate could be fragmented via a base-induced elimination reaction to yield a series of substituted polyaromatics, including naphthalene, benzofuran, benzothiophene, phenanthrene, phenalene, acenaphthene, and triphenylene. Using different reagents, this method made it possible to introduce methyl or 2-hydroxyethyl groups as substituents at specific positions in these arenes.

Full text of DOI:10.1016/j.tet.2014.01.035

Tetrahedron 70 (2014) 1748e1762
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Construction of polyaromatics via photocyclization of 2-(fur-3-yl)
ethenylarenes, using a 3-furyl group as an isopropenyl equivalent
synthon
Ying-Zhe Chen, Ching-Wen Ni, Fu-Lin Teng, Yi-Shun Ding, Tunng-Hsien Lee,
*
Jinn-Hsuan Ho
Department of Chemical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Road, Taipei 10607, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history:
The construction of different types of substituted arenes was demonstrated through the photocyclization
of 2-(fur-3-yl)ethenylarenes using a 3-furyl group as an isopropenyl equivalent synthon in the photo-
cyclization reaction. The furan portion of the photocyclization intermediate could be fragmented via
a base-induced elimination reaction to yield a series of substituted polyaromatics, including naphtha-
lene, benzofuran, benzothiophene, phenanthrene, phenalene, acenaphthene, and triphenylene. Using
different reagents, this method made it possible to introduce methyl or 2-hydroxyethyl groups as sub-
stituents at specific positions in these arenes.
Received 8 September 2013
Received in revised form 4 January 2014
Accepted 20 January 2014
Available online 25 January 2014
Keywords:
3-Furyl
Furan
Ó 2014 Elsevier Ltd. All rights reserved.
Synthon
Photorearrangement
Polyaromatics
1. Introduction
Oxidative photocyclization:
hv
Compounds with polyaromatic skeletons are widely used in
optoelectronic materials, and the development of methodologies
for the synthesis of derivatives from these compounds has received
considerable attention for the past several decades. Although direct
functionalization of arenes appears to be a straightforward method
for synthesizing substituted arenes, it is only feasible for certain
specific substituted arenes because of regioselectivity. Instead,
many different synthetic methodologies have been designed for
individual polyaromatics, including naphthalenes,1 benzofurans,2
benzothiophenes,3 phenanthrenes,4 phenalenes,5 acenaph-
thenes,6 and triphenylenes.7
Ar
Ar'
Ar
Ar'
[O]
Some limits:
1. Photolysis of 1-phenyl-1,3-butadiene does not lead to naphthalene.
hv
X
2. Photocyclization of m-methylstilbene yields isomers.
hv
+
[O]
Among the methodologies for the synthesis of polyaromatics,
oxidative photocyclization of stilbene-type compounds8 is a well-
known technique for synthesizing different kinds of arenes
(Scheme 1), including phenanthrenes, naphthoheterocycles, and
arenes containing multiple fused benzene or heterocyclic rings.
Additionally, oxidative photocyclization remains a popular way to
synthesize some aromatic compounds for optoelectronic mate-
rials.9 However, oxidative photocyclization shows some limitations.
3. 4H-Cyclopenta[def]phenanthrene is hard to revert.
Scheme 1. Oxidative photocyclization of stilbene-type compounds and its limits.
First, photolysis of 1-phenyl-1,3-butadiene in the presence of oxi-
dants does not lead to oxidative photocyclization,10 instead
resulting in a variety of photoadditions and four-
zation reactions. Second, the photocyclization of substituted
p-electron cycli-
* Corresponding author. Tel.: þ886 2 2737 6642; fax: þ886 2 2737 6644; e-mail
address: jhho@mail.ntust.edu.tw (J.-H. Ho).
0040-4020/$ e see front matter Ó 2014 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2014.01.035

Y.-Z. Chen et al. / Tetrahedron 70 (2014) 1748e1762
1749
stilbene-type compounds sometimes transforms both desired and
undesired regio-isomers; for example, the irradiation of m-meth-
ylstilbene can generate a mixture of 2-methylphenanthrene and 4-
methylphenanthrene. Third, arenes with cycloalkyl chains, such as
4H-cyclopenta[def]phenanthrene, are difficult to revert back to
stilbene-type compounds.11 Therefore, developing a new synthetic
strategy that can overcome these difficulties would represent
a significant improvement.
Furan is a useful synthon that can be converted into different
functional groups,12 such as 1,4-diketones,13 benzene rings,14 and
penta-2,4-dienals.15 Recently, we reported16 a base-induced photo-
rearrangement of 3-styrylfurans to yield 2-methyl-7-substituted
naphthalenes in the presence of DBU/EtOH/C6H6. (Scheme 2). This
photorearrangement led to a new transformation of furan. The furan
portion of the photocyclization intermediate of 3-styrylfurans is
fragmented to generate 2-methylnaphthalenes, which is the theo-
retical result of oxidative photocyclization of 1-ary-3-methyl-1,3-
butadienes. Thus, in six-electron photocyclization, the 3-furyl group
can be regarded as an isopropenyl equivalent synthon to construct
a simple benzene ring. We hypothesized that this base-induced
photorearrangement would not only solve the previous difficulties
inherent in synthesizing substituted polyaromatics, but also provide
a new method for synthesizing several different polyaromatics.
were synthesized, and preparation of 1aem was carried out via the
Wittig Reaction17 using the appropriate 4-substituted benzyl ha-
lide, triphenylphosphine, and furan-3-carboxaldehyde. The applied
synthetic procedures and yields are described in the experimental
section.
Photolysis of 1aem generated 2-methyl-7-substituted naph-
thalenes or 2-(7-substituednaphthalen-2-yl)ethanols as the major
products. The results are shown in Scheme 3. The photoreaction
yields in the presence of 10% KOH(aq)/MeOH are reported in Table 1,
and the yields in the presence of LiBH4/KOH(aq)/MeOH are reported
in Table 2.
R
hv
300 nm
R
OH
R
+
Cond.
O
1a-m
2a-j and 2l
3a, 3g-j, and 3l
R = (a) OMe, (b) OCF3, (c) tBu, (d) iPr, (e) nPr, (f) Et, (g) Me,
(h) H, (i) F, (j) Cl, (k) Br, (l) CN, (m) NO2
O2N
MeO
MeO
OMe
OMe
OMe
O
O
O
4m
4a
4a'
Our previous work16
:
Scheme 3. Photolysis of 3-styrylfurans.
O
O
hv, DBU
in C6H6
Table 1
Photolysis of 3-styrylfurans in the presence of 10% KOH(aq)/MeOH for 3 h
DHNF
This work:
Entry
Reactant
Conversion (%)
Product
Yield (%)
Yield (%)a
from Ref. 16
hv
conditions
R
Ar
b
1
2
3
4
5
6
7
8
1a
1b
1c
1d
1e
1f
1g
1h
1i
95
98
75
81
93
4aþ4a0
2b
2c
2d
2e
2f
2g
2h
40
19
43
48
45
42
40
20
34
21
22
52
24
41 (2a)
d
Ar
O
d
R = CH3 under the condition of KOH/MeOH
R = CH2CH2OH under the condition of LiBH4/KOH/MeOH
61
d
90
93
46
58
42
35
d
R'
R
R
R
100
94
100
100
76
X
9
2i
10
11
12
13
1j
1k
1l
2hþ2jc
X = O, S
B
2h
d
B = -CH2CH2-
R
2l
4m
15
d
-CH2CH2CH2-
1m
97
R
Irradiation was carried out in the presence of DBU/EtOH/C6H6.16
The ratio of 4a and 4a0 was 1:5.
a
b
c
A
The ratio of 2h and 2j was 2:1.
A = no -CH2-
-CH2-
Scheme 2. Photorearrangement with a 3-furyl group as an isopropenyl equivalent
synthon.
Table 2
Photolysis of 3-styrylfurans in the presence of LiBH4/KOH(aq)/MeOH for 3 h
In addition to using benzene as solvent, we determined that this
photorearrangement occurs in the presence of KOH/MeOH, making
it more environmentally friendly. We also discovered that using the
strong reducing agent LiBH4 leads to the formation of the reductive
products and higher yields. Therefore, we report this synthetic
methodology for synthesizing a series of naphthalenes, benzofu-
rans, benzothiophenes, phenanthrenes, phenalenes, acenaph-
thenes, and triphenylenes.
En. React. Conver. (%) Prod. 2 (Yield, %) Prod. 3 (Yield, %) Total yield (%)
1
2
3
4
5
6
1a
1g
1h
1i
1j
1l
100
100
100
100
100
100
2a (27)
2g (31)
2h (30)
2i (28)
3a (43)
3g (41)
3h (7)
70
72
37
40
27
9
3i (12)
2hþ2j (15)a
2l (6)
3hþ3j (12)a
3l (3)
a
The ratio of 2h and 2j was 1:1, and that of 3h and 3j was 1:0.9.
2. Results and discussion
In the presence of 10% KOH(aq)/MeOH (Table 1), the photolysis of
2.1. Synthesis of 2,7-disubstituted naphthalenes
1bei and 1l generated the 2-methyl-7-substituted naphthalenes
2bei and 2l as the major products (19e52% yields) and a small
amount of side products with a complicated structure (examined
via thin-layer-chromatography (TLC) and crude 1H NMR spectrum
As the starting materials for the photochemical synthesis of 2,7-
disubstituted naphthalenes, 3-(4-substituted styryl)furans 1aem

1750
Y.-Z. Chen et al. / Tetrahedron 70 (2014) 1748e1762
analyses). The best photoreaction results (40e52% yields) were
obtained using 3-styrylfurans with alkyl groups (1ceg, entries 3e7)
and a cyano group (1l, entry 12), while 3-stytylfuran (1h, entry 8)
and 3-(4-fluorostyryl)furan (1i, entry 9) generated poor results (20
and 34% yields, respectively). Irradiation of 3-(4-chlorostyryl)furan
(1j, entry 10) and 3-(4-bromostyryl)furan (1k, entry 11) led to
dehalogenated 2h as the major product. The reason for this result is
expected to be the same as the results of photo-debromination of
bromonaphthalene with potassium hydroxide.18 However, this
photorearrangement did not proceed in some cases. Photolysis of
1a only generated the methanol addition products 4a and 4a0 at
a total yield of 40%; this photoaddition of methanol to stilbene-type
compounds has been reported for methoxystilbenes19 and 2-(4-
methoxystyryl)naphthalene.20 Alternative reaction conditions for
the formation of 2-methoxy-2-methylnaphthalene 2a involve the
irradiation of 1a and DBU in benzene.16 Photolysis of 1m also
generated the methanol addition product 4m, as a nitro group
would retard the process of photocyclization to produce a photo-
rearrangement product.21
Compared with the results of photorearrangement in methanol,
photolysis of most 3-styrylfurans (1a, 1d, 1feg, entries 1, 4, 6e8) in
the presence of DBU/EtOH/C6H6 produced higher yields,16 perhaps
due to avoiding the photoaddition of methanol. However, photol-
ysis of 3-(4-cyanostyryl)furan (1l, entry 12) with DBU in benzene
may lead to a charge transfer reaction, resulting in a low yield of the
photorearrangement product 2l. This difficulty was overcome using
the reagents KOH/MeOH, resulting in a significantly higher yield.
In the presence of LiBH4/KOH(aq)/MeOH (Table 2), photolysis of
1a generated the products 2a and 3a, and similar results were
obtained for irradiation of 1gej and 1l. The total yields of 2 and 3 in
these cases were in the range of 9e72%. 3-Styrylfurans with
electron-donating groups, methoxy (1a, entry 1) and methyl groups
(1g, entry 2) underwent photorearrangement to yield the best re-
sults (70e72% yields). 3-Styrylfurans without functional groups
(1h, entry 3) or with halides (1ie1j, entries 4e5) generated the
poorest results (27e40% yields). The extremely low yield obtained
for 1l may be due to the lability of cyano groups in the presence of
LiBH4.
OH
hv
300 nm
+
X
O
X
X
LiBH4,
KOH(aq)
MeOH
3n-o
1n-o
X = (n) O, (o) S
2n-o
O
N
O
O
1q
1p
Scheme 4. Photolysis of 1-heterocyclic-2-(fur-3-yl)ethenes.
Table 3
Photolysis of 1-heterocyclic-2-(fur-3-yl)ethenes in the presence of LiBH4/KOH(aq)
MeOH for 3 h
/
En. React. Conver. (%) Prod. 2 (Yield, %) Prod. 3 (Yield, %) Total yield (%)
1
2
3
4
1n
1o
1p
1q
100
100
100
83
2n (0)
2o (5)
0
0
3n (29)
3o (84)
29
89
0
0
0
0
Photolysis of 1n in the presence of LiBH4/KOH(aq)/MeOH (Table
3) only generated the product 3n at a 29% yield, while photolysis
of 1o generated the products 2o and 3o at a total yield of 89%.
However, irradiation of 1p and 1q did not generate any photo-
rearrangement products. 1,2-Di(fur-3-yl)ethene 1p contains two
unstable 3-furyl groups, which may cause the compound to de-
compose very quickly. The compound cis-1q exhibits a lower
quantum yield from photocyclization because of the presence of
a 2-pyridinyl group (the quantum yield of the photocyclization of
cis-2-styrylpyridine is 0.014,24 while that for cis-stilbene is 0.125), so
that the rate of photorearrangement may be too slow to compete
with the decompositions.
2.3. Synthesis of polyaromatics
Most of these photoreactions showed low yields (Tables 1 and
2). To confirm the causes of these low yields, two individual ex-
periments were performed, in which the trans and cis forms of 3-(4-
methylstyryl)furan (trans and cis-1g) were maintained at 40 ꢀC in
the presence of KOH(aq)/MeOH without irradiation. The results
showed that trans-1g was recovered with a 98% yield, whereas cis-
1g was recovered with only a 78% yield. The low yields may have
resulted from the stability of cis-styryfurans, which contain a more
acidic hydrogen at the C-2 position in the furan ring.22
The 1-aryl-2-(fur-3-yl)ethenes 1rey were synthesized as the
starting materials for the photochemical synthesis of substituted
arenes. The preparation of 1rew was initiated by synthesizing the
appropriate arylmethyl halide via NBS-bromination or SOCl2-
chlorination, followed by the Wittig Reaction. The preparation of
1xey was initiated by preparing 9-methylphenanthrenes via oxi-
dative photocyclization of the appropriate stilbenes, followed by
NBS-bromination and the Wittig Reaction. The synthetic pro-
cedures and yields are described in experimental section.
Photolysis of 1rew in the presence of 10% KOH(aq)/MeOH and
LiBH4/KOH(aq)/MeOH led to the photorearrangement products
2rew and 3rew. However, due to the solubility of 1xey, only
photolysis of 1xey in the presence of DBU/EtOH/C6H6 was able to
generate the photorearrangement products 2xey. The structures of
1rey, 2rey, and 3rew are shown in Scheme 5. The photoreaction
results are reported in Tables 4 and 5.
Photolysis of 1ret and 1v in the presence of 10% KOH(aq)/MeOH
and photolysis of 1r and 1xey in the presence of DBU/EtOH/C6H6
successfully generated the methylarenes 2ret, 2v, and 2xey
(20e38% yields) (Table 4). Photolysis of 1u (entry 5) did not yield
2u, possibly because the methoxy group increases the rate of the
photoaddition of methanol.19 Photolysis of 1w (entry 7) led to
formation of the product 2v, which may have resulted from the
photo-dehalogenation of 2w with potassium hydroxide.18 Photol-
ysis of 1r in benzene (entry 1) resulted in a higher yield than when
carried out in methanol (entry 2) due to avoiding the photoaddition
of methanol.
2.2. Synthesis of benzoheterocycles
The 1-heterocyclic-2-(fur-3-yl)ethenes 1neq were synthesized
as starting materials for the photochemical synthesis of 5-
substitued-benzoheterocycles. The preparation of 1nep was car-
ried out through multiple procedures, including the reduction of
heterocyclic-carboxaldehyde into heterocyclic-methanol, chlori-
nation to synthesize heterocyclic-methyl chloride, and the Wittig
Reaction with triphenylphosphine and furan-3-carboxaldehyde.
The preparation of 1q was carried out via the condensation of 2-
picoline and furan-3-carboxaldehyde in acetic anhydride.23 The
synthetic procedures and yields are described in the experimental
section.
Photolysis of 1neq in the presence of 10% KOH(aq)/MeOH did not
lead to photorearrangement, and most of the starting materials
were decomposed. 5-Substitued-benzoheterocycles can only be
obtained in the presence of LiBH4/KOH(aq)/MeOH following irradi-
ation. The photoreaction results are shown in Scheme 4 and Table 3.

Y.-Z. Chen et al. / Tetrahedron 70 (2014) 1748e1762
1751
phenalenes (2t and 3t), 5,8-disustituted-2,3-dihydro-1H-phena-
lene (3u), and 4-substituted acenaphthenes (2v and 3v); and the
development of a feasible technique for synthesizing a 2-methyl-
10-substitutedtriphenylene, such as the compound 2y.
O
R
R
2r: R = CH3
2s: R = CH3
3s: R = CH2CH2OH
1r
1s
1u
1w
O
3r: R = CH2CH2OH
O
O
2.4. Mechanism
A proposed mechanism for this photoreaction is shown in
Scheme 6. The reaction steps include the transecis isomerization of
trans-1, photocyclization of cis-1, the E1cB (unimolecular elimina-
tion of conjugate base) reaction of DHNF and DHNF0, the pro-
tonation of N1, the tautomerization of N2, the Norrish-type 1
photoreaction26 of N3 to generate compound 2, and the reduction
of the aldehyde group of N3 to yield compound 3. The side reaction
consisting of the photoaddition of methanol, and the possible de-
composition pathways are also included. Based on this proposed
mechanism, we can discuss the following issues: 1. the substitution
effect of the photoaddition of methanol; 2. the fact that the aryle-
thenolate anion of N1 is a leaving group; 3. the increase of yields
using a reducing agent; 4. the E1cB reaction; and 5. the presence of
the intermediate N3.
H3CO
H3CO
R
2t: R = CH3
R
3u: R = CH2CH2OH
1t
3t: R = CH2CH2OH
O
O
Br
R
2v: R = CH3
R
2v: R = CH3
1v
3v: R = CH2CH2OH
3v: R = CH2CH2OH
NC
CH3
NC
CH3
O
O
2y
1y
1x
2x
Scheme 5. Structures of 1-aryl-2-(fur-3-yl)ethenes and their photorearrangement
products.
R
hv
Methanol-Addition Products
MeOH
R=OMe, NO2
trans-1
hv
O
Table 4
2
1O
H
O
1
Photolysis of 1-aryl-2-(fur-3-yl)ethenes in the presence of 10% KOH(aq)/MeOH for 6 h
O
H
H
9
3
R
R
R
hv
KOH
Entry
1a
2
3
4
Reactant
Conversion (%)
Prod. 2 (%)
Yield (%)
9b
9b
8
7
9a
9a
1r
1r
1s
1t
1u
1v
1w
1x
1y
100
100
100
100
100
100
100
100
100
2r
2r
2s
2t
2u
2v
2v
2x
2y
38
29
25
27
0
26
21
32
20
4
5
6
cis-1
DHNF'
DHNF
Side reactions resulted from
anion delocalization
Decomposition of 3-furyl
group
5
6
O
H
HO
O
R
7
R
R
8a
9a
N3
hv
N1
N2
3
LiBH4
a
The reaction was carried out in the presence of DBU/EtOH/C6H6.
R
CH3
R
OH
Table 5
2
Photolysis of 1-aryl-2-(fur-3-yl)ethenes in the presence of LiBH4/KOH(aq)/MeOH for
6 h
Scheme 6. A proposed mechanism.
En. React. Conver. (%) Prod. 2 (Yield, %) Prod. 3 (Yield, %) Total yield (%)
1
2
3
4
5
6
1r
1s
1t
1u
1v
1w
100
100
100
100
100
100
2r (5)
2s (20)
2t (8)
2u (0)
2v (15)
2v (15)
3r (44)
3s (40)
3t (68)
3u (26)
3v (48)
3v (26)
49
60
76
26
63
41
2.4.1. Substitution effect of the photoaddition of methanol. The
photoaddition of methanol to stilbene-type compounds has been
reported for compounds with a methoxy group.16 The key step in
this addition is the formation of a charge separation intermediate
(Scheme 7). This charge separation intermediate can be stabilized
by electron-donating or electron-withdrawing groups to enhance
the rate of photoaddition, resulting in regioselectivity. In the irra-
diation of 1a, we found that a methoxy group stabilized the cation
to enhance the rate of photoaddition and generated the methanol
addition products 4a and 4a0 as the only type of products, with
Photolysis of 1rew in the presence of LiBH4/KOH(aq)/MeOH
generated the products 2ret, 2v, and 3rev; the total yields of 2 and
3 were in the moderate range of 26e76% (Table 5). The poor results
of the irradiation of 1u may have been caused by the methoxy
group enhancing the photoaddition of methanol,19 and the gener-
ation of the products 2v and 3v from the photolysis of 1w may have
resulted from the photo-dehalogenation of 2w and 3w with po-
tassium hydroxide.18
There were some unique results of synthesizing different
substituted arenes using this methodology, including the acquisi-
tion of 2-substituted phenanthrene (2r and 3r) without regio-
isomers via a photochemical reaction; the direct photochemical
formation of 2-substituted-4H-cyclopenta[def]phenanthrene (2s
and 3s); the first synthesis of 5-sustituted-2,3-dihydro-1H-
hv
Photorearrangement
trans-1
hv
R
R
Methanol
Addition
Products
O
O
charge-separation intermediate
Scheme 7. The charge separation intermediate for methanol addition products.

1752
Y.-Z. Chen et al. / Tetrahedron 70 (2014) 1748e1762
good regioselectivity (Table 1, entry 1, 4a:4a0¼1:5). When a tri-
fluoromethoxy substituent (1b, Table 1, entry 2) was used to de-
crease the cation stabilization ability, photorearrangement became
the major reaction pathway. In the irradiation of 1m (Table 1, entry
13), a nitro group not only retarded the process of photocyclization
but also stabilized the charge separation intermediate, such that
irradiation of 1m led to the methanol addition product 4m as the
major product (but with a low yield). In the irradiation of 1g with
a methyl group (weak electron-donating group), photorearrange-
ment was the major reaction pathway, while photoaddition was
a minor reaction. A time-tracking analysis of the photolysis of 1g
showed that the methanol addition products (4g and 4g0 in this
case) were not stable under irradiation and silica gel
chromatography.27
hv
1r
1r
CH3
KOH(aq)
in MeOH
(29%)
2r
CHO
hv
+
CHO
tBuOK
in tBuOH
N3r (24%)
5r (4%)
Scheme 8. Comparison of the photolysis of 1r in the presence of tBuOK/tBuOH and
KOH/MeOH.
Table 7
Photolysis of 3-(4-methylstyryl)furan 1g with different reducing agents in KOH(aq)
MeOH for 3 h
/
2.4.2. The arylethenolate anion of N1 as a good leaving group. The
elimination reaction from DHNF to N1 employs the arylethenolate
anion of N1 as the leaving group. Typically strong bases, such as
alkoxide (pKa of alkanols are 16e17), are inferior leaving groups,
whereas the phenolate anion (the pKa of phenol is approximately
10) is a weaker base than alkoxide and can be used the leaving
group in some photoreactions.28 According to the findings of
Kresge,29 the pKa of phenylethenol is 9.45, which is similar to the
pKa of phenol, and the arylethenolate anion can therefore also be
employed as a leaving group in this photorearrangement. Similar
results have been reported for other heterocycles, including ben-
zofuran and oxadiazole.30
Entry Reagent Conversion (%) Prod. 2g (%) Prod. 3g (%) Total yield (%)
1
2
3
4
None
KBH4
NaBH4
LiBH4
93
100
100
100
40
18
17
31
0
23
31
41
40
41
48
72
reaction yield (entry 4) because the stronger reducing agent could
efficiently trap the unstable aldehyde N3g to prevent the formation
of unstable radical intermediates in the Norrish-type 1 photore-
action. However, the reaction rate of the Norrish-type 1 photore-
action for N3 is expected to be very close to that of the reduction of
the aldehyde group of N3; thus, this photorearrangement only
produced a mixture of 2g and 3g.
2.4.3. Increased yields using a reducing agent. To understand the
effect of the base and reducing agent, different bases (KOH, NaOH,
t
LiOH, and BuOK) and reducing agents (LiBH4, NaBH4, and KBH4)
were used in the photorearrangement procedure. The effects of the
bases were estimated by irradiating 1r with the different bases,
and the photorearrangement results are shown in Table 6 and
Scheme 8. According to the experimental results, the photolysis of
1r without a base in the presence of LiBH4(aq)/MeOH did not lead to
any photorearrangement (Table 6, entry 1). When 1r was irradiated
with the different bases under these conditions, the total yields of
the photorearrangements were not markedly different (Table 6,
entries 2e4). Even when 1r was irradiated in the presence of
tBuOK/tBuOH, the total yields of N3r and 5r were very close to the
2.4.4. E1cB (unimolecular elimination conjugated base) reaction. In
accordance with the theory of six-p-electron cyclization, the pho-
tocyclization of stilbene-type compounds leads to conrotatory ring
closure. This leaves the hydrogens on carbon 9a and 9b of DHNF in
a trans configuration8b and the leaving oxygen-1 and the hydrogen
on carbon 9a in a cis configuration (Scheme 6), such that in the
elimination reaction from DHNF to N1, the E2 reaction cannot occur
directly. A possible reaction pathway was hypothesized to be E1cB
elimination. Hence, the hydrogen on carbon 9a was first deproto-
nated with a base to form an anion on carbon 9a of DHNF0, and the
fragmentation of oxygen-1 from carbon 9b of DHNF0 was then
driven by the negative charge of carbon 9a to generate the naph-
thalene ring of N1. When electron-withdrawing groups on carbon
8, heterocycles or polyaromatics increased the stability of the in-
termediate DHNF0, reducing the rate of the reaction from DHNF0 to
N1,28,32 the photolysis of 1b (trifluoromethoxy), 1i (fluoro), 1j
(chloro), 1k (bromo), 1q (pyridin-2-yl), and 1rey (polyaromatics)
led to poor results. However, when electron-releasing groups on
carbon 8 decreased the stability of DHNF0, the formation rate of N1
was increased, causing the photolysis of 1a (methoxy) and 1g
(methyl) to occur with better results.
yields obtained from the photolysis of 1r in the presence of KOH(aq)
/
MeOH (Scheme 8). These results indicate that the base is necessary
for this photorearrangement to occur, but different bases do not
significantly affect the photorearrangement.
Table 6
Photolysis of 1-(naphthen-1-yl)-2-(fur-3-yl)ethenes 1r with different bases in LiB-
H4(aq)/MeOH for 3 h
Entry Reagent Conversion (%) Prod. 2r (%) Prod. 3r (%) Total yield (%)
1a
2b
3b
4b
None
LiOH
NaOH
KOH
d
0
0
47
42
44
0
47
45
49
100
100
100
Trace
3
5
It is worth mentioning that photorearrangement of 1o leads to
a good result (89% total yield). A possible reason for this finding is
that the thiophene of cis-1o presents a lower resonance energy,
making photocyclization more efficient, and the sulfur atom of
DHNF0 has an electron-releasing effect in the case of 1o, to increase
the transformation from DHNF0 to N1 (Scheme 9).
a
The results were determined based on the 1H NMR spectrum of the crude
sample.
b
Isolated yields.
The effect of the reducing agents was estimated by irradiating
1g with the different reducing agents, and the photorearrangement
results are shown in Table 7. Compared to the results of photo-
rearrangement in the absence of reducing agents, the photolysis of
1g with different reducing agents led to the production of com-
pounds 2g and 3g at better yields31 (Table 7, entries 2e4). Addi-
tionally, the use of a stronger reducing agent, LiBH4, led to the best
2.4.5. The presence of the intermediate N3. To confirm the presence
of the intermediate N3, harsh conditions (potassium tert-butoxide
in tert-butyl alcohol and dried THF) were used to prevent the N1
protonation step. In addition to the isolation of N3r (Scheme 8), the
photolysis of 1h in the presence of tBuOK/dried THF generated
a mixture of N3h, 5h, and some uncharacterized side products

Y.-Z. Chen et al. / Tetrahedron 70 (2014) 1748e1762
1753
gel with a 60e120 mesh via gravity. Tetrahydrofuran was dried
using a liquid chromatography solvent purification system. All
other solvents were employed as received, and all commercial re-
agents were used without purification.
O
O
O
H
H
KOH
LiBH4
H
hv
9b
9b
9a
9a
N1
S
S
S
cis-1o
DHNF of 1o
DHNF' of 1o
4.2. General procedure for the synthesis of 3-styrylfurans
1aem
Scheme 9. Intermediates of the photolysis of 1o.
Preparation of 3-styrylfurans was carried out via the Wittig
Reaction using the appropriate 4-substituted benzyl halide as the
starting material. The general experimental procedures were as
follows. A mixture of triphenylphosphine (42 mmol), 4-substituted
benzyl halide (35 mmol) and benzene (20 mL) was refluxed over-
night. The mixture was then cooled to room temperature, and the
precipitant (triphenylphosphonium salt) was collected via suction
filtration. Next, triphenylphosphonium salt (24 mmol), 3-fural
(22 mmol), and 18-crown-6 (3 mmol) were dissolved in dichloro-
methane (55 mL), and a 50% potassium carbonate aqueous solution
(24 mL) was added to the dichloromethane mixture. The mixture
was stirred vigorously overnight. Then, the reaction was extracted
with ethyl acetate several times, and the organic layers were
combined and subsequently dried using anhydrous MgSO4. The
solvent was removed with a rotary evaporator and the products,
cis- and trans-3-styrylfurans, were purified via gravity chroma-
tography using hexane/ethyl acetate for elution. The total yields of
the cis and trans forms are reported below.
(Scheme 10). Because of the influence of the side products, further
TLC purification was performed to achieve acceptable purity of the
products. The isolation of N3h and N3r confirmed the presence of
the intermediate N3. However, the formation of 5h and 5r was
unexpected. The mechanism of 5h formation probably included the
[2þ2]photocycloaddition of the double bond of N1h and carbonyl
group of N3h to form oxetane, followed by the retro-[2þ2]
photocycloaddition of oxetane to generate 5h.33
CHO
hv
CHO
+
1h
tBuOK in
dried THF
(8%)
(12%)
5h
N3h
retro-
protonation
and tautomerization
[2+2]photo-
[2+2]photocycloaddition
O
cycloaddition
O
O
4.2.1. trans-3-(4-Methoxystyryl)furan trans-1a.34 56
NMR (500 MHz, CDCl3):
%
yield. 1H
7.46 (s,1H), 7.35 (m,1H), 7.33 (d, J¼8.7 Hz,
N1h
O
d
N3h
2H), 6.83 (d, J¼8.7 Hz, 1H), 6.79 (d, J¼16.3 Hz, 1H), 6.72 (d,
J¼16.3 Hz, 1H), 6.60 (d, J¼1.9 Hz, 1H), 3.77 (s, 3H); 13C NMR
Scheme 10. Possible mechanism for the formation of N3h and 5h.
(125 MHz, CDCl3):
d 159.05, 143.58, 140.43, 130.17, 127.94, 127.27,
124.70, 116.32, 114.08, 107.34, 55.27; MS (EI, 70 eV) m/z 200 (Mþ,
100), 171 (73), 169 (4), 128 (28); HRMS (C13H12O2) calcd: 200.0837,
found: 200.0840.
3. Conclusion
A new synthetic methodology for the synthesis of substituted
polyaromatics is reported here. Using a 3-furyl group as an iso-
propenyl equivalent synthon provides an alternative approach for
constructing aromatic rings through photocyclization. We have
successfully demonstrated the synthesis of a series of substituted
naphthalenes, substituted benzofurans, substituted benzothio-
phenes, substituted phenanthrenes, substituted phenalenes,
substituted acenaphthenes, and substituted triphenylenes through
this photorearrangement process under different conditions. In
these photorearrangements, the use of LiBH4/KOH(aq)/MeOH pro-
vides acceptable total yields (2 and 3) from the photolysis of 1a,
1gej, 1l, 1neo, and 1rew. The mechanism is also discussed in this
report. The intermediates N3h and N3r can be obtained by the ir-
4.2.2. trans-3-(4-Trifluoromethoxystyryl)furan trans-1b. 44 % yield.
1H NMR (500 MHz, CDCl3):
d
7.56 (s, 1H), 7.46 (d, J¼8.3 Hz, 2H), 7.44
(s, 1H), 7.20 (d, J¼8.3 Hz, 2H), 6.96 (d, J¼16.3 Hz, 1H), 6.80 (d,
J¼16.3 Hz, 1H), 6.67 (d, J¼1.7 Hz, 1H); 13C NMR (125 MHz, CDCl3):
d
148.27, 148.26, 143.80, 141.23, 136.17, 127.24, 126.80, 124.28,
121.54, 121.12, 119.50, 119.43, 107.27; MS (EI, 70 eV) m/z 255 (Mþþ1,
8), 254 (Mþ, 97), 226 (12), 225 (97), 169 (14), 141 (18), 128 (17);
HRMS (C13H9F3) calcd: 254.0555, found: 254.0560.
4.2.3. trans-3-(4-tert-Butylstyryl)furan trans-1c. 76 % yield. 1H NMR
(500 MHz, CDCl3):
d
7.53 (s, 1H), 7.42 (s, 1H), 7.40 (d, J¼9.2 Hz, 2H),
7.37 (d, J¼8.7 Hz, 2H), 6.94 (d, J¼16.2 Hz, 1H), 6.81 (d, J¼16.2 Hz,
t
1H), 6.67 (d, J¼1.4 Hz, 1H), 1.34 (s, 9H); 13C NMR (125 MHz, CDCl3):
radiation of 1h and 1r, respectively, with a stronger base, BuOK.
This new photochemical synthetic methodology provides several
advantages, including the ability to easily synthesize naphthalenes,
to synthesize some complicated substituted arenes without regio-
isomers, and to synthesize different polyaromatics using a single
method.
d
150.45, 143.62, 140.71, 134.58, 128.22, 125.83, 125.56, 124.68,
117.60, 107.40, 34.60, 31.30; MS (EI, 70 eV) m/z 227 (Mþþ1, 3), 226
(Mþ, 38), 211 (100), 170 (16),141 (8),128 (3); HRMS (C16H18O) calcd:
226.1358, found: 226.1350.
4.2.4. trans-3-(4-Isopropylstyryl)furan trans-1d. 82 % yield. 1H NMR
4. Experimental section
(500 MHz, CDCl3):
d
7.54 (s, 1H), 7.42 (s, 1H), 7.40 (d, J¼8.2 Hz, 2H),
7.22 (d, J¼8.2 Hz, 2H), 6.95 (d, J¼16.2 Hz, 1H), 6.82 (d, J¼16.2 Hz,
1H), 6.67 (s, 1H), 2.93 (heptet, J¼6.9 Hz, 1H), 1.25 (d, J¼6.9 Hz, 6H);
4.1. Materials and methods
13C NMR (125 MHz, CDCl3):
d 148.21, 143.61, 140.69, 134.97, 128.33,
A photochemical reactor produced by a local company was
equipped with a merry-go-round apparatus and 16 monochromic
light tubes (300 nm). The quartz tubes for photolysis were 1.5 cm in
diameter and 20 cm in length. NMR spectra were measured on
a Bruker AVIII-500 MHz FT-NMR spectrometer, with chloroform-d1
as the standard. Mass spectra were recorded on a Finnigan MAT95S
spectrometer. Column chromatography was conducted using silica
126.70, 126.09, 124.66, 117.48, 107.38, 33.86, 23.92; MS (EI, 70 eV)
m/z 213 (Mþþ1, 5), 212 (Mþ, 100), 197 (87), 170 (42), 169 (32), 141
(47), 128 (3); HRMS (C15H16O) calcd: 212.1201, found: 212.1201.
4.2.5. trans-3-(4-Propylstyryl)furan trans-1e. 74 % yield. 1H NMR
(500 MHz, CDCl3):
J¼7.9 Hz, 2H), 7.16 (d, J¼7.9 Hz, 2H), 6.94 (d, J¼16.1 Hz, 1H), 6.81 (d,
d
7.53 (s, 1H), 7.41 (t, J¼1.3 Hz, 1H), 7.38 (d,

1754
Y.-Z. Chen et al. / Tetrahedron 70 (2014) 1748e1762
J¼16.1 Hz, 1H), 6.66 (d, J¼1.9 Hz, 1H), 2.59 (t, J¼7.7 Hz, 2H), 1.66
(sextet, J¼7.5 Hz, 2H), 0.97 (t, J¼7.4 Hz, 3H); 13C NMR (125 MHz,
110.17, 107.14; MS (EI, 70 eV) m/z 196 (Mþþ1, 3), 195 (Mþ, 62), 166
(100), 155 (3), 140 (16); HRMS (C13H9NO) calcd: 195.0684, found:
195.0689.
CDCl3):
d 143.59, 142.02, 140.66, 134.80, 128.73, 128.36, 125.98,
124.65, 117.41, 107.37, 37.76, 24.47, 13.81; MS (EI, 70 eV) m/z 213
(Mþþ1, 4), 212 (Mþ, 70), 183 (100), 169 (17), 155 (17), 141 (13), 128
(3); HRMS (C15H16O) calcd: 212.1201, found: 212.1197.
4.2.13. trans-3-(4-Nitrostyryl)furan trans-1m.34 56 % yield. 1H NMR
(500 MHz, CDCl3):
d
8.18 (d, J¼8.8 Hz, 2H), 7.61 (s, 1H), 7.55 (d,
J¼8.8 Hz, 2H), 7.45 (s, 1H), 7.14 (d, J¼16.1 Hz, 1H), 6.84 (d, J¼16.1 Hz,
4.2.6. trans-3-(4-Ethylstyryl)furan trans-1f. 50 % yield. 1H NMR
1H), 6.68 (d, J¼1.9 Hz, 1H); 13C NMR (125 MHz, CDCl3):
d 146.46,
(500 MHz, CDCl3):
d
7.52 (s, 1H), 7.41 (s, 1H), 7.37 (d, J¼7.9 Hz, 2H),
144.13, 143.91, 142.37, 126.37, 125.94, 124.06, 123.96, 123.08, 107.12;
MS (EI, 70 eV) m/z 216 (Mþþ1, 8), 215 (Mþ, 100), 198 (9), 185 (14),
169 (17), 168 (28), 156 (13), 141 (36), 139 (25), 128 (11); HRMS
(C12H9NO3) calcd: 215.0582, found: 215.0581.
7.17 (d, J¼7.9 Hz, 2H), 6.93 (d, J¼16.4 Hz,1H), 6.80 (d, J¼16.4 Hz,1H),
6.66 (d, J¼1.9 Hz, 1H), 2.65 (q, J¼7.7 Hz, 2H), 1.24 (t, J¼7.6 Hz, 3H);
13C NMR (125 MHz, CDCl3):
d 143.62, 140.69, 134.83, 128.37, 128.15,
126.10, 124.67, 117.46, 107.39, 28.61, 15.51; MS (EI, 70 eV) m/z 199
(Mþþ1, 5), 198 (Mþ, 100), 183 (39), 169 (68), 155 (9), 141 (37), 128
(3); HRMS (C14H14O) calcd: 198.1045, found: 198.1047.
4.3. Synthesis of 1-heterocyclic-2-(fur-3-yl)ethenes 1neq
4.3.1. 1-(Fur-2-yl)-2-(fur-3-yl)ethene 1n. Preparation of 1-(fur-2-
yl)-2-(fur-3-yl)ethene was carried out via multiple procedures,
including the reduction of furan-2-carboxaldehyde to (fur-2-yl)
methanol, the chlorination of (fur-2-yl)methanol to (fur-2-yl)
methyl chloride, and the Wittig Reaction to generate 1n. The ex-
perimental details are described as follows: Reduction of furan-2-
carboxaldehyde: A solution of furan-2-carboxaldehyde (0.02 mol)
and methanol (20 mL) was held in 10 ꢀC water bath, and a solution
of 2 M NaOH(aq) (0.4 mL), NaBH4 (0.28 g) and water (3.6 mL) was
added to the methanol solution with a dropping funnel. The mix-
ture was then stirred for an additional thirty minutes and sub-
sequently neutralized with an acidic aqueous solution. The reaction
mixture was extracted with ethyl acetate several times, after which
the organic layers were combined and dried using anhydrous
MgSO4, and the organic solvent was removed with a rotary evap-
orator, followed by purification of the residue via silica gel chro-
matography. The reduction compound, (fur-2-yl)-methanol, was
obtained at a 92% yield. Chlorination of (fur-2-yl)methanol: A solu-
tion of (fur-2-yl)methanol (0.01 mol), triethylamine (0.01 mol), and
dichloromethane (20 mL) was prepared and transferred to a 50-mL
double-neck flask equipped with a condenser and a dropping
funnel. A solution of thionyl chloride (1 mL) and dichloromethane
(10 mL) was then added to the flask with a dropping funnel while
the flask was held in a 15 ꢀC water bath under a nitrogen atmo-
sphere. Next, the mixture was stirred at 20 ꢀC for thirty minutes and
at 40 ꢀC for another thirty minutes. Subsequently, the reaction was
quenched with crushed ice and water, and the solution was neu-
tralized with NaOH(aq). Next, the reaction mixture was extracted
with ethyl acetate, and the organic layers were collected and dried
using anhydrous MgSO4. After removing the organic solvent with
a rotary evaporator, the product, (fur-2-yl)methyl chloride, was
used for the Wittig Reaction directly, without characterization.
Wittig Reaction: A mixture of triphenylphosphine (24 mmol), (fur-
2-yl)methyl chloride (20 mmol) and benzene (15 mL) was refluxed
overnight. The mixture was cooled to room temperature, and the
precipitate (triphenylphosphonium salt) was collected via suction
filtration. Subsequently, the triphenylphosphonium salt (10 mmol),
3-fural (11 mmol), and 18-crown-6 (1.5 mmol) were dissolved in
25 mL dichloromethane, and a 50% potassium carbonate aqueous
solution (12 mL) was added to the dichloromethane mixture. The
mixture was subsequently stirred vigorously for 2 days, and then
extracted with ethyl acetate several times. The organic layers were
combined and dried with anhydrous magnesium sulfate. The sol-
vent was removed with a rotary evaporator and the product, trans-
1-(fur-2-yl)-2-(fur-3-yl)ethene 1n, was purified via silica gel chro-
matography using hexane for elution. The yield was 31%.
4.2.7. trans-3-(4-Methylstyryl)furan trans-1g.34 81 % yield. 1H NMR
(500 MHz, CDCl3):
d
7.51 (s, 1H), 7.40 (s, 1H), 7.34 (d, J¼8.1 Hz, 2H),
7.14 (d, J¼7.9 Hz, 2H), 6.92 (d, J¼16.2 Hz,1H), 6.79 (d, J¼16.2 Hz,1H),
6.65 (d, J¼1.9 Hz, 1H), 2.34 (s, 3H); 13C NMR (125 MHz, CDCl3):
d
143.61, 140.67, 137.16, 134.58, 129.33,128.37, 126.02, 124.66, 117.41,
107.39, 21.18; MS (EI, 70 eV) m/z 185 (Mþþ1, 4), 184 (Mþ, 78), 155
(100), 141 (22), 70 (16), 61 (17); HRMS (C13H12O) calcd: 184.0888,
found: 184.0887.
4.2.8. trans-3-Styrylfuran trans-1h.34 84
(500 MHz, CDCl3):
%
yield. 1H NMR
d
7.58 (s, 1H), 7.51 (d, J¼8.0 Hz, 2H), 7.47 (s, 1H),
7.40 (t, J¼7.7 Hz, 2H), 7.30 (t, J¼7.8 Hz, 1H), 7.03 (d, J¼16.4 Hz, 1H),
6.88 (d, J¼16.4 Hz, 1H), 6.72 (s, 1H); 13C NMR (125 MHz, CDCl3):
d
143.63, 140.89, 137.30, 128.58, 128.36, 127.27, 126.07, 124.50,
118.34, 107.34; MS (EI, 70 eV) m/z 171 (Mþþ1, 4), 170 (Mþ, 84), 141
(100), 115 (34), 70 (18), 61 (14); HRMS (C12H10O) calcd: 170.0732,
found: 170.0731.
4.2.9. trans-3-(4-Fluorostyryl)furan trans-1i.34 57 % yield. 1H NMR
(500 MHz, CDCl3):
d
7.53 (s, 1H), 7.41 (s, 1H), 7.40 (dd, J¼8.6, 5.5 Hz,
2H), 7.03 (t, J¼8.7 Hz, 2H), 6.88 (d, J¼16.2 Hz,1H), 6.78 (d, J¼16.2 Hz,
1H), 6.65 (d, J¼1.0 Hz, 1H); 13C NMR (125 MHz, CDCl3):
d 162.14 (d,
JCeF¼245.3 Hz), 143.74, 140.91, 133.53 (d, JCeF¼3.1 Hz), 127.58,
127.36 (d, JCeF¼39.9 Hz), 124.39, 118.19 (d, JCeF¼2.5 Hz), 115.55 (d,
JCeF¼21.5 Hz), 107.28; MS (EI, 70 eV) m/z 189 (Mþþ1, 3), 188 (Mþ,
76), 160 (24), 159 (100), 133 (25), 70 (20), 61 (16); HRMS (C12H9FO)
calcd: 188.0637, found: 188.0640.
4.2.10. trans-3-(4-Chlorostyryl)furan trans-1j.34 39 % yield. 1H NMR
(500 MHz, CDCl3):
d
7.55 (s, 1H), 7.43 (s, 1H), 7.38 (d, J¼8.7 Hz, 2H),
7.31 (d, J¼8.7 Hz, 2H), 7.27 (s, 1H), 6.95 (d, J¼16.2 Hz, 1H), 6.77 (d,
J¼16.2 Hz, 1H), 6.66 (d, J¼1.9 Hz, 1H); 13C NMR (125 MHz, CDCl3):
d
143.80,141.15,135.86,130.90,129.45,128.77,127.24,127.07,119.03,
107.27; MS (EI, 70 eV) m/z 206 (Mþþ2, 15), 204 (Mþ, 63), 175 (39),
169 (30), 141 (100), 139 (23), 70 (25); HRMS (C12H9ClO) calcd:
204.0342, found: 204.0344.
4.2.11. trans-3-(4-Bromostyryl)furan trans-1k.34 75 % yield. 1H NMR
(500 MHz, CDCl3):
d
7.55 (s, 1H), 7.46 (d, J¼8.5 Hz, 2H), 7.43 (s, 1H),
7.32 (d, J¼8.5 Hz, 2H), 6.97 (d, J¼16.2 Hz, 1H), 6.75 (d, J¼16.2 Hz,
1H), 6.65 (d, J¼1.9 Hz, 1H); 13C NMR (125 MHz, CDCl3):
d 143.82,
141.20, 136.31, 131.71, 127.58, 127.11, 124.30, 120.94, 119.15, 107.26;
MS (EI, 70 eV) m/z 250 (Mþþ2, 25), 248 (Mþ, 27),169 (24),141 (100),
139 (22); HRMS (C12H9BrO) calcd: 247.9837, found: 247.9843.
4.2.12. trans-3-(4-Cyanostyryl)furan trans-1l.34 64 % yield. 1H NMR
(500 MHz, CDCl3):
d
7.60 (d, J¼8.5 Hz, 2H), 7.59 (s, 1H), 7.50 (d,
4.3.1.1. (Fur-2-yl)-methanol.35 1H NMR (500 MHz, CDCl3):
d 7.40
J¼8.5 Hz, 2H), 7.44 (s, 1H), 7.08 (d, J¼16.1 Hz, 1H), 6.79 (d,
(dd, J¼1.8, 0.7 Hz, 1H), 6.34 (dd, J¼3.2, 1.8 Hz, 1H), 6.29 (d, J¼3.2 Hz,
J¼16.1 Hz, 1H), 6.66 (d, J¼1.9 Hz, 1H); 13C NMR (125 MHz, CDCl3):
1H), 4.60 (s, 1H); 13C NMR (125 MHz, CDCl3):
110.33, 107.73, 57.42.
d 153.96, 142.55,
d
144.04, 142.06, 141.85, 132.39, 126.40, 123.94, 122.13, 119.01,

Y.-Z. Chen et al. / Tetrahedron 70 (2014) 1748e1762
1755
4.3.1.2. trans-1-(Fur-2-yl)-2-(fur-3-yl)ethene trans-1n. 1H NMR
(500 MHz, CDCl3):
anhydrous magnesium sulfate. The solvent was removed with
a rotary evaporator, and the product 1q was purified via silica gel
chromatography using ethyl acetate and hexane for elution. The
yield was 18%.
d
7.51 (s, 1H), 7.40 (s, 1H), 7.37 (d, J¼1.5 Hz, 1H),
6.89 (d, J¼16.3 Hz, 1H), 6.61 (d, J¼16.3 Hz, 1H), 6.60 (s, 1H), 6.40 (dd,
J¼3.4, 1.7 Hz, 1H), 6.27 (d, J¼3.4 Hz,1H); 13C NMR (125 MHz, CDCl3):
d
153.16, 143.69, 141.80, 140.67, 124.26, 117.08, 116.51, 111.46, 107.60,
107.17.
4.3.4.1. trans-1-(Fur-3-yl)-2-(pyridin-2-yl)ethene
NMR (500 MHz, CDCl3):
trans-1q. 1H
8.57 (dq, J¼4.7, 0.8 Hz, 1H), 7.63 (td, J¼7.7,
d
4.3.2. 1-(Fur-3-yl)-2-(thiophen-2-yl)ethene 1o. Preparation of 1-
(fur-3-yl)-2-(thiophen-2-yl)ethene was carried out via procedures
similar to those used for the preparation of 1n, and all of the ex-
perimental procedures are summarized as follows: Reduction of
thiophene-2-carboxaldehyde: 0.02 mol of thiophene-2-carboxal
dehyde was used as the starting material to synthesize (thio-
phen-2-yl)methanol (97% yield). Chlorination of (thiophen-2-yl)
methanol: 0.01 mol of (thiophen-2-yl)methanol was used as the
starting material to synthesize (thiophen-2-yl)methyl chloride,
without characterization. Wittig Reaction: 24 mmol of triphenyl-
phosphine and 20 mmol of (thiophen-2-yl)methyl chloride were
used to synthesize triphenylphosphonium salt. Then, 10 mmol of
the triphenylphosphonium salt, 11 mmol of 3-fural, and all of the
other necessary reagents were used to synthesize cis- and trans-1-
(fur-3-yl)-2-(thiophen-2-yl)ethene 1o, obtaining a total yield 62%.
The cis and trans forms were purified via silica gel chromatography
using hexane for characterization.
1.8 Hz, 1H), 7.59 (s, 1H), 7.50 (d, J¼15.9 Hz, 1H), 7.42 (s, 1H), 7.31 (d,
J¼7.9 Hz, 1H), 7.12 (ddd, J¼7.4, 4.9, 1.0 Hz, 1H), 6.88 (d, J¼15.9 Hz,
1H), 6.68 (d, J¼1.8 Hz, 1H); 13C NMR (125 MHz, CDCl3):
d 155.61,
149.52, 143.86, 142.21, 136.53, 127.63, 124.10, 122.69, 121.80, 121.57,
107.45; MS (EI, 70 eV) m/z 171 (Mþ, 87), 170 (Mþꢁ1, 100), 143 (88),
142 (72), 141 (70); HRMS (C11H9NO) calcd: 171.0679, found:
171.0676.
4.4. Synthesis of 1-aryl-2-(fur-3-yl)ethenes 1rey
4.4.1. 1-(Fur-3-yl)-2-(naphthalen-1-yl)ethene 1r. A mixture of 1-
(chloromethyl)naphthalene (2 g, 11.3 mmol), triphenylphosphine
(3.56 g, 13.6 mmol) and ethyl acetate (23 mL) was refluxed over-
night. Then, the mixture was cooled to room temperature, and
a precipitate (triphenylphosphonium salt) was formed and col-
lected via suction filtration. Subsequently, the triphenylphospho-
nium salt, 3-furaldehyde (1.03 g, 10.7 mmol) and 18-crown-6
(0.42 g) were dissolved in dichloromethane (30 mL), and a 50%
potassium carbonate aqueous solution (15 mL) was added. The
mixture was stirred vigorously overnight, followed by extraction
with ethyl acetate several times. The organic layers were combined
and dried with anhydrous magnesium sulfate. The solvent was
removed with a rotary evaporator, and the residue was purified via
chromatography using hexanes to generate cis- and trans-1-(fur-3-
yl)-2-(naphthalen-1-yl)ethene 1r (2.13 g, 85%).
4.3.2.1. (Thiophen-2-yl)methanol.36 1H NMR (500 MHz, CDCl3):
d
7.33 (d, J¼5.3 Hz, 1H), 7.11 (d, J¼3.3 Hz, 1H), 6.98 (dd, J¼5.3, 3.3 Hz,
1H), 4.83 (s, 2H).
4.3.2.2. trans-1-(Fur-3-yl)-2-(thiophen-2-yl)ethene trans-1o. 1H
NMR (500 MHz, CDCl3):
d 7.51 (s, 1H), 7.41 (s, H), 7.16 (d,
J¼5.0 Hz, 1H), 7.01e6.98 (m, 2H), 6.95 (d, J¼16.0 Hz, 1H), 6.80 (d,
J¼16.0 Hz, 1H), 6.61 (s, 1H); 13C NMR (125 MHz, CDCl3):
d 143.70,
142.79, 140.81, 127.49, 125.32, 124.16, 123.83, 121.58, 118.19,
107.23.
4.4.1.1. cis-1-(Fur-3-yl)-2-(naphthalen-1-yl)ethene
NMR (500 MHz, CDCl3):
cis-1r. 1H
8.01 (dd, J¼8.0, 1.0 Hz, 1H), 7.86 (d,
d
J¼7.8 Hz, 1H), 7,80 (dd, J¼7.1, 2.3 Hz, 1H), 7.51e7.41 (m, 4H), 7.23 (s,
1H), 7.06 (t, J¼1.6 Hz, 1H), 6.90 (d, J¼11.9 Hz, 1H), 6.66 (d, J¼11.9 Hz,
4.3.3. 1,2-Di(Fur-3-yl)ethene 1p. Preparation of 1,2-di(fur-3-yl)
was carried out via procedures similar to those used for the
preparation of 1n, and all of the experimental procedures are
summarized as follows: Reduction of furan-3-carboxaldehyde:
0.02 mol of furan-3-carboxaldehyde was used as the starting
material to synthesize (fur-3-yl)-methanol (92% yield). Chlorina-
tion of (fur-3-yl)methanol: 0.01 mol of (fur-3-yl)methanol was used
as the starting material to synthesize (fur-3-yl)methyl chloride,
without characterization. Wittig Reaction: 24 mmol of triphenyl-
phosphine and 20 mmol of (fur-3-yl)methyl chloride were used to
synthesize triphenylphosphonium salt. Then, 10 mmol of the tri-
phenylphosphonium salt, 11 mmol of 3-fural, and all of the other
necessary reagents were used to synthesize cis- and trans-1,2-
di(fur-3-yl)ethene 1p, obtaining a total yield 32%. The cis and
trans forms were purified via silica gel chromatography using
hexane for characterization.
1H), 5.72 (d, J¼1.9 Hz, 1H); 13C NMR (125 MHz, CDCl3):
d 142.40,
142.19, 135.62, 133.54, 131.41, 128.28, 127.60, 127.07, 126.28, 125.95,
125.90, 125.40, 125.09, 122.46, 121.94, 109.97.
4.4.1.2. trans-1-(Fur-3-yl)-2-(naphthalen-1-yl)ethene
1r. 1H NMR (500 MHz, CDCl3):
trans-
d
8.18 (d, J¼8.4 Hz, 1H), 7.85 (dd,
J¼7.9, 1.6 Hz, 1H), 7.77 (d, J¼8.2 Hz, 1H), 7.67 (d, J¼7.2 Hz, 1H),
7.59e7.44 (m, 6H), 7.00 (d, J¼16.0 Hz 1H), 6.77 (t, J¼0.9 Hz, 1H);
13C NMR (125 MHz, CDCl3):
d 143.78, 141.14, 134.99, 133.71, 131.19,
128.58, 127.78, 126.00, 125.79, 125.67, 125.40, 124.86, 123.72,
123.31, 121.41, 107.50; MS (EI, 70 eV) m/z 220 (Mþ, 100), 219
(Mþꢁ1, 17), 191 (87); HRMS (C16H12O) calcd: 220.0888, found:
220.0886.
4.4.2. 3-(2H-Acenaphthylen-1-ylidenemethyl)furan 1s. The prepa-
ration of 3-(2H-acenaphthylen-1-ylidenemethyl)furan began with
the NBS-bromination of acenaphthene to generate 1-bromo
acenaphthene, which was then subjected to the Wittig Reaction
to synthesize 1s. A carbon tetrachloride solution (45 mL) of ace-
naphthene (1 g, 6.48 mmol), N-bromosuccinimide (1.05 g,
5.90 mmol) and dibenzoylperoxide (0.03 g, 0.12 mmol) was
refluxed for 8 h. The reaction mixture was then cooled to room
temperature, filtered and evaporated to dryness. Next, the crude
product and triphenylphosphine (1.7 g, 6.48 mmol) were dissolved
in ethyl acetate (13 mL), and the ethyl acetate solution was refluxed
overnight. The mixture was subsequently cooled to room temper-
ature, and the precipitate (triphenylphosphonium salt) was col-
lected via suction filtration. This salt, 3-furaldehyde (0.4 g,
4.2 mmol) and 18-crown-6 (0.22 g) were dissolved in
4.3.3.1. (Fur-3-yl)methanol.37 1H NMR (500 MHz, CDCl3):
d 7.31
(s, 2H), 6.34 (s, 1H), 4.40 (s, 2H).
4.3.3.2. trans-1,2-Di(fur-3-yl)ethene
(500 MHz, CDCl3):
(s, 2H).
trans-1p.38 1H
d 7.46 (s, 2H), 7.37 (s, 2H), 6.66 (s, 2H), 6.58
NMR
4.3.4. 1-(Fur-3-yl)-2-(pyridin-2-yl)ethene 1q. A mixture of furan-3-
carbaldehyde (2.0 mL, 0.02 mol), 4-picoline (2.0 mL, 0.02 mol),
and acetic anhydride (30 mL) was refluxed for 24 h. Then, the re-
action was poured into an ice/water mixture and neutralized with
sodium carbonate. The solution was extracted with ethyl acetate
several times. The organic layers were combined and dried with

1756
Y.-Z. Chen et al. / Tetrahedron 70 (2014) 1748e1762
dichloromethane (7 mL), and a 50% potassium carbonate aqueous
solution (3.5 mL) was added. The mixture was stirred vigorously
overnight. Then, the reaction mixture was extracted with ethyl
acetate several times. The organic layers were combined and dried
with anhydrous magnesium sulfate. The solvent was removed with
a rotary evaporator, and the residue was purified via chromatog-
raphy with hexanes to generate 3-(2H-acenaphthylen-1-
ylidenemethyl)furan 1s (0.47 g, 32%).
3-(3,4-dihydro-2H-naphthalen-1-ylidenemethyl)furan 1u (0.26 g,
21%).
4.4.4.1. 3-((6-Methoxy-3,4-dihydronaphthalen-1(2H)-ylidene)
methyl)-furan 1u. 1H NMR (500 MHz, CDCl3):
d
7.60 (d, J¼8.8 Hz,
1H), 7.52 (t, J¼0.8 Hz, 1H), 7.41 (t, J¼1.8 Hz, 1H), 6.76 (dd, J¼8.8,
2.8 Hz, 1H), 6.67 (s, 1H), 6.64 (d, J¼2.8 Hz, 1H), 6.52 (dd, J¼1.8,
0.8 Hz,1H), 3.80 (s, 3H), 2.73 (t, J¼6.5 Hz, 2H), 2.69 (td, J¼6.5, 2.1 Hz,
2H), 1.85 (quintet, J¼6.3 Hz, 2H).
4.4.2.1. 3-(2H-Acenaphthylen-1-ylidenemethyl)furan 1s. 1H NMR
(500 MHz, CDCl3):
d
7.67 (s, 1H), 7.63 (dd, J¼8.0, 3.1 Hz, 2H), 7.58 (d,
4.4.5. 3-Indan-1-ylidenemethylfuran 1v. The preparation of 3-
indan-1-ylidenemethylfuran began with the chlorination of 1-
indanol to generate 1-chloroindane, which was then subjected to
the Wittig Reaction to synthesize 1v. A sealed 250 mL double-neck
flask was charged with 1-indanol (8.28 g, 61.7 mmol) and trie-
thylamine (6.25 g, 61.7 mmol) and filled with nitrogen. Dry
dichloromethane (120 mL) was added with a syringe. A dry
dichloromethane solution (12 mL) of thionyl chloride (8.0 g,
67.2 mmol) was added dropwise to the reaction mixture in a 0 ꢀC
ice water bath over a period of 10 min. Then, the solution was
stirred at 0 ꢀC for 30 min and refluxed at 40 ꢀC for another 40 min.
After cooling to room temperature, ice and a 10% sodium bi-
carbonate aqueous solution were added to the mixture, and the
organic and aqueous layers were separated. The aqueous layer was
extracted with dichloromethane, and the organic layers were col-
lected. The organic layers were dried over magnesium sulfate and
concentrated under vacuum to obtain a yellow residue. The residue
and triphenylphosphine (16.2 g, 61.7 mmol) were dissolved in ethyl
acetate (130 mL), and the resulting solution was refluxed overnight.
Then, the mixture was cooled to room temperature, and the pre-
cipitate (triphenylphosphonium salt) was collected via suction fil-
tration. The obtained salt (1.79 g, 4.3 mmol), 3-furaldehyde (0.4 g,
4.2 mmol) and 18-crown-6 (0.14 g) were dissolved in dichloro-
methane (10 mL), and a 50% potassium carbonate aqueous solution
(5 mL) was added. The reaction mixture was stirred vigorously
overnight, followed by extraction with ethyl acetate several times.
The organic layers were combined and dried with anhydrous
magnesium sulfate. The solvent was removed with a rotary evap-
orator and purified via chromatography with hexanes to generate
cis- and trans-3-indan-1-ylidenemethylfuran 1v (0.52 g, 4%).
J¼7.0 Hz, 1H), 7.52e7.45 (m, 3H), 7.33 (d, J¼6.7 Hz, 1H), 7.07 (s, 1H),
6.69 (s, 1H), 4.11 (s, 2H); MS (EI, 70 eV) m/z 232 (Mþ, 100), 203 (59);
HRMS (C17H12O) calcd: 232.0888, found: 232.0882.
4.4.3. 3-(3,4-Dihydro-2H-naphthalen-1-ylidenemethyl)furan
1t. The preparation of 3-(3,4-dihydro-2H-naphthalen-1-ylidene
methyl)furan began with the NBS-bromination of 1,2,3,4-
tetrahydronaphthalene to generate 1-bromo-1,2,3,4-tetrahydrona
phthalene, which was then subjected to the Wittig Reaction to
synthesize 1t. An ethyl acetate solution (200 mL) of 1,2,3,4-
tetrahydronaphthalene (10 g, 75.6 mmol), N-bromosuccinimide
(12.8 g, 72 mmol) and dibenzoylperoxide (0.37 g, 1.53 mmol) was
refluxed for 4 h. Next, triphenylphosphine (23.8 g, 90.7 mmol) was
added to the mixture, followed by refluxing overnight. Sub-
sequently, the mixture was cooled to room temperature, and the
precipitate (triphenylphosphonium salt)was collected via suction
filtration. This salt, 3-furaldehyde (2.33 g, 24.3 mmol) and 18-
crown-6 (0.83 g) were dissolved in dichloromethane (58 mL),
and a 50% potassium carbonate aqueous solution (28 mL) was
added. The mixture was stirred vigorously overnight and then
extracted with ethyl acetate several times. The organic layers were
combined and dried with anhydrous magnesium sulfate. The sol-
vent was removed with a rotary evaporator, and the residue was
purified via chromatography using hexane for elution to generate
3-(3,4-dihydro-2H-naphthalen-1-ylidenemethyl)furan 1t (0.48 g,
3%).
4.4.3.1. 3-(3,4-Dihydro-2H-naphthalen-1-ylidenemethyl)furan
1t. 1H NMR (500 MHz, CDCl3):
d
7.50 (dd, J¼7.7, 0.9 Hz, 1H), 7.36 (d,
J¼0.6 Hz, 1H), 7.25 (t, J¼1.7 Hz, 1H), 7.16e7.09 (m, 2H), 6.99 (tm,
J¼7.0 Hz, 1H), 6.24 (d, J¼1.8 Hz, 1H), 6.16 (s, 1H), 2.83 (t, J¼6.7 Hz,
2H), 2.47 (td, J¼6.5, 1.4 Hz, 2H), 1.94 (quintet, J¼6.7 Hz, 2H); 13C
4.4.5.1. (Z)-3-Indan-1-ylidenemethylfuran
(500 MHz, CDCl3):
(Z)-1v. 1H
NMR
d
7.58 (d, J¼7.9 Hz, 1H), 7.44e7.41 (m, 2H), 7.25
NMR (125 MHz, CDCl3):
d
142.33, 141.17, 138.74, 137.89, 135.53,
(d, J¼7.6 Hz, 1H), 7.16 (td, J¼7.4, 1.1 Hz, 1H), 7.05 (t, J¼7.4 Hz, 1H),
6.48 (d, J¼1.3 Hz, 1H), 6.28 (s, 1H), 2.97e2.94 (m, 2H), 2.87e2.83 (m,
128.49, 128.47, 127.51, 124.61, 122.94, 113.84, 110.63, 34.71, 29.35,
23.89; MS (EI, 70 eV) m/z 210 (Mþ, 100), 181 (75), 165 (59); HRMS
(C15H14O) calcd: 210.1045, found: 210.1043.
2H); 13C NMR (125 MHz, CDCl3):
d 148.61, 144.29, 142.62, 140.24,
139.71, 128.07, 125.87, 125.24, 124.26, 122.05, 111.14, 110.71, 34.30,
30.11.
4.4.4. 3-((6-Methoxy-3,4-dihydronaphthalen-1(2H)-ylidene)methyl)
furan 1u. Sodium borohydride (0.43 g, 11.37 mmol) was added to
a methanol solution (15 mL) of 6-methoxyl-1-tetralone (1.0 g,
5.68 mmol). The reaction mixture was stirred at room temperature
for 1 h and subsequently diluted with water and extracted with
ethyl acetate. The organic phase was dried over anhydrous mag-
nesium sulfate, and the solvent was evaporated. The resulting al-
cohol and triphenylphosphonium bromide (1.95 g, 5.68 mmol)
were suspended in benzene (10 mL) and refluxed for 12 h. The
precipitate collected through filtration and dried. The obtained salt
(2.32 g, 4.61 mmol), 3-furaldehyde (0.44 g, 4.58 mmol) and 18-
crown-6 (0.15 g) were dissolved in dichloromethane (10 mL), and
a 50% potassium carbonate aqueous solution (5 mL) was added. The
reaction mixture was stirred vigorously overnight and then
extracted with ethyl acetate several times. The organic layers were
combined and dried with anhydrous magnesium sulfate. The sol-
vent was removed with a rotary evaporator, and the residue was
purified via chromatography using hexane for elution to generate
4.4.5.2. (E)-3-Indan-1-ylidenemethylfuran
(500 MHz, CDCl3):
(E)-1v. 1H
NMR
d
7.55 (s, 2H), 7.52 (dd, J¼6.3, 2.0 Hz, 1H), 7.42 (t,
J¼1.6 Hz, 1H), 7.26 (dd, J¼6.3, 2.0 Hz, 1H), 7.22e7.17 (m, 2H), 6.75 (t,
J¼2.6 Hz, 1H), 6.57 (d, J¼1.3 Hz, 1H), 3.11e3.08 (m, 2H), 2.94e2.90
(m, 2H); 13C NMR (125 MHz, CDCl3):
d 145.99,143.03,142.86,141.96,
140.58, 127.78, 126.55, 125.26, 123.98, 119.90, 110.59, 108.47, 30.53,
30.46; MS (EI, 70 eV) m/z 197 (Mþþ1, 40), 196 (Mþ, 79), 167 (100);
HRMS (C14H12O) calcd: 196.0888, found: 196.0885.
4.4.6. 3-(4-Bromo-indan-1-ylidenemethyl)furan 1w. Sodium boro-
hydride (0.36 g, 9.52 mmol) was added to a methanol solution
(15 mL) of 4-bromo-1-indanone (1.0 g, 4.74 mmol). The mixture
was stirred at room temperature for 1 h. The reaction mixture was
diluted with water, and extracted with ethyl acetate. The organic
phase was dried over anhydrous magnesium sulfate, and the sol-
vent was evaporated. The resulting alcohol and triphenylphos-
phonium bromide (1.63 g, 4.74 mmol) were suspended in benzene

Y.-Z. Chen et al. / Tetrahedron 70 (2014) 1748e1762
1757
(10 mL) and refluxed for 12 h. The precipitate was collected by
filtration and dried. The obtained salt (0.68 g, 1.26 mmol), 3-
furaldehyde (0.12 g, 1.25 mmol) and 18-crown-6 (0.04 g) were
dissolved in dichloromethane (3 mL), and a 50% potassium car-
bonate aqueous solution (1.4 mL) was added. The mixture was
stirred vigorously overnight. Then, the reaction was extracted with
ethyl acetate several times. The organic layers were combined and
dried with anhydrous magnesium sulfate. The solvent was removed
with a rotary evaporator, and the residue was purified via chro-
matography using hexane for elution to generate 3-(4-bromo-
indan-1-ylidenemethyl)furan (0.26 g, 20% yield).
triphenylphosphonium salt (0.96 g, 71% yield), was collected via
suction filtration. The obtained salt (1.60 g, 3 mmol), 3-furaldehyde
(0.26 g, 2.73 mmol) and 18-crown-6 (0.10 g, 0.67 mmol) were
dissolved in dichloromethane (7 mL), and a 50% potassium car-
bonate aqueous solution (4 mL) was added. The mixture was stir-
red vigorously at room temperature for 2 days. Then, the reaction
was extracted with ethyl acetate several times. The organic layers
were combined and dried with anhydrous magnesium sulfate. The
solvent was removed with a rotary evaporator, and the residue was
purified via chromatography with hexane and ethyl acetate to
generate a yellow solid, cis- and trans-3-(2-(phenanthren-9-yl)vi-
nyl)furan 1x (0.66 g, 70% yield).
4.4.6.1. (Z)-3-(4-Bromo-indan-1-ylidenemethyl)furan (Z)-1w. 1H
NMR (500 MHz, CDCl3):
d
7.49 (d, J¼7.8 Hz, 1H), 7.42 (t, J¼1.7 Hz,
4.4.7.1. 9-Methylphenanthrene.39 1H NMR (500 MHz, CDCl3):
1H), 7.41 (s, 1H), 7.31 (d, J¼7.8 Hz, 1H), 6.92 (t, J¼7.8 Hz, 1H), 6.42 (d,
J¼1.7 Hz, 1H), 6.28 (d, J¼1.0 Hz, 1H), 2.97e2.93 (m, 2H), 2.88e2.85
d
8.74 (dd, J¼7.3, 2.1 Hz, 1H), 8.67 (d, J¼7.9 Hz, 1H), 8.07 (dd, J¼7.3,
2.1 Hz, 1H), 7.82 (dd, J¼7.3, 1.7 Hz, 1H), 7.69 (td, J¼6.7, 1.7 Hz, 1H),
7.66 (td, J¼7.2, 1.5 Hz, 1H), 7.61 (td, J¼7.2, 1.5 Hz, 1H), 7.60 (s, 1H),
7.58 (td, J¼7.2, 1.4 Hz, 1H), 2.76 (s, 3H); 13C NMR (125 MHz, CDCl3):
(m, 2H); 13C NMR (125 MHz, CDCl3):
d 145.96, 143.97, 143.05,
142.62, 140.98, 130.46, 128.40, 123.60, 120.81, 118.65, 110.49, 110.23,
32.15, 29.75.
d
132.47, 132.08, 132.01, 130.37, 129.66, 127.81, 126.72, 126.56,
126.50, 126.19, 125.79, 124.64, 122.99, 122.44, 20.01.
4.4.6.2. (E)-3-(4-Bromo-indan-1-ylidenemethyl)furan (E)-1w. 1H
NMR (500 MHz, CDCl3):
d
7.55 (s, 1H), 7.44e7.42 (m, 2H), 7.33 (d,
4.4.7.2. trans-3-(2-(Phenanthren-9-yl)vinyl)furan trans-1x. 1H
J¼7.8 Hz, 1H), 7.07 (t, J¼7.8 Hz, 1H), 6.73 (t, J¼2.7 Hz, 1H), 6.56 (d,
NMR (500 MHz, CDCl3):
d
8.75 (dd, J¼7.9, 1.3 Hz, 1H), 8.67 (d,
J¼1.1 Hz, 1H), 3.09e3.05 (m, 2H), 2.94e2.92 (m, 2H); 13C NMR
J¼8.1 Hz, 1H), 8.24 (dd, J¼7.9, 1.3 Hz,1H), 7.92 (s, 1H), 7.90 (dd, J¼7.7,
1.5 Hz, 1H), 7.69 (td, J¼7.4, 1.5 Hz, 1H), 7.66 (td, J¼7.4, 1.5 Hz, 1H),
7.63 (td, J¼7.7, 1.5 Hz, 1H), 7.62 (s, 1H), 7.60 (td, J¼7.3, 1.3 Hz, 1H),
7.58 (d, J¼15.8 Hz, 1H), 7.49 (s, 1H), 7.10 (d, J¼15.8 Hz, 1H), 6.81 (d,
J¼1.7 Hz, 1H).
(125 MHz, CDCl3):
d 148.43, 144.12, 142.82, 141.73, 140.36, 130.92,
127.73, 123.05, 121.62, 120.66, 112.54, 111.01, 33.22, 31.55.
4.4.7. 3-(2-(Phenanthren-9-yl)vinyl)furan 1x. 3-(2-(Phenanthren-
9-yl)vinyl)furan was synthesized through multiple steps, which
included the Wittig Reaction to synthesize 1,2-diphenylpropene,
the oxidative photocyclization of 1,2-diphenylpropene, and the
NBS-bromination of 9-methylphenanthrene, which was then sub-
jected to the Wittig Reaction to synthesize 1x. The experimental
details are described as follows: Synthesis of 1,2-diphenylpropene
via the Wittig Reaction: A mixture of 1-(bromoethyl)benzene
(3.7 g, 20 mmol), triphenylphosphine (6.3 g, 24 mmol) and ethyl
acetate (16 mL) was refluxed for 3 days. Then, the mixture was
cooled to room temperature, and a precipitate (triphenylphos-
phonium salt) was formed and collected via suction filtration.
Subsequently, the triphenylphosphonium salt (4.0 g, 9 mmol) and
potassium tert-butoxide (1.5 g, 13.5 mmol) were transferred to
a 100 mL flask, which was sealed and maintained under a nitrogen
atmosphere. Dry tetrahydrofuran (21 mL) and benzaldehyde
(0.87 g, 8.2 mmol) were then added to the mixture with a syringe,
followed by stirring for 5 h. Next, the reaction was extracted with
ethyl acetate several times. The organic layers were combined and
dried with anhydrous magnesium sulfate. The solvent was re-
moved with a rotary evaporator, and the residue was purified via
chromatography with hexane to produce cis- and trans-1,2-
diphenylpropene (0.94 g, 59%). Oxidative photocyclization: A mix-
ture of 1,2-diphenylpropene (0.1 g), iodine (0.02 g), and hexane
(50 mL) was prepared and divided into five quartz tubes. The tubes
were sealed with septa and irradiated under 300 nm UV light at
ambient temperature (approximately 40 ꢀC). After irradiation, the
reaction was quenched with an aqueous sodium hydroxide solu-
tion, and the mixture was extracted with ethyl acetate. The organic
layers were collected and dried, and the organic solvent was re-
moved. A yellow-brown solid, 9-methylphenanthrene, was ob-
tained at a 98% yield. NBS-bromination and the Wittig Reaction:
An ethyl acetate solution (25 mL) of 9-methylphenanthrene
(0.69 g, 3.57 mmol), N-bromosuccinimide (0.66 g, 3.72 mmol)
and dibenzoylperoxide (0.02 g, 0.076 mmol) was refluxed for 2 h.
The reaction mixture was cooled to room temperature, and tri-
phenylphosphine (0.80 g, 3.05 mmol) was added to the previous
reaction. The reaction was refluxed for 3 days. Then, the mixture
was cooled to room temperature, and the precipitate,
4.4.8. 3-(2-(3-Cyanophenanthren-9-yl)vinyl)furan 1y. The prepara-
tion of (Z)-3-(2-(3-cyanophenanthren-9-yl)vinyl)furan was per-
formed following the same procedures used for the compound 1x.
Synthesis of 1-(4-cyanophenyl)-2-phenylpropene via the Wittig Re-
action: Using 1-(bromoethyl)benzene (3.7 g, 20 mmol), triphenyl-
phosphine (6.3 g, 24 mmol), and ethyl acetate (16 mL), triphenyl
phosphonium salt (8.74 g, 19.5 mmol) was synthesized. Then, using
the triphenylphosphonium salt (4.02 g, 9 mmol), potassium tert-
butoxide (1.5 g, 13.5 mmol), dry tetrahydrofuran (21 mL), and 4-
cyanobenzaldehyde (1.07 g, 8.2 mmol), (Z)- and (E)-1-(4-
cyanophenyl)-2-phenylpropene 1y were synthesized (1.10 g, 60%).
Oxidative photocyclization: Using (Z)- and (E)-1-cyanophenyl-2-
phenylpropene (0.1 g), iodine (0.02 g), and hexane (50 mL), 3-
cyano-9-methylphenanthrene was synthesized (99% yield). NBS-
bromination and the Wittig Reaction: Using 3-cyano-9-methyl
phenanthrene (0.44 g, 2.04 mmol), N-bromosuccinimide (0.38 g,
2.12 mmol), dibenzoylperoxide (0.01 g, 0.043 mmol), and ethyl
acetate (20 mL), 3-cyano-9-(bromomethyl)phenanthrene was
synthesized. Then, triphenylphosphine (0.64 g, 2.44 mmol) was
added to the previous reaction directly to produce triphenylphos-
phonium salt (0.45 g, 40% yield). Subsequently, the triphenyl-
phosphonium salt (0.6 g, 1.0 mmol), 3-furaldehyde (0.09 g,
0.98 mmol), 18-crown-6 (0.03 g, 0.13 mmol), dichloromethane
(3 mL), and a50% potassium carbonate aqueous solution (4 mL)
were employed to synthesize cis- and trans-3-(2-(3-cyano
phenanthren-9-yl)vinyl)furan 1y (0.17 g, 54% yield).
4.4.8.1. 3-Cyano-9-methylphenanthrene. 1H NMR (500 MHz,
CDCl3):
d
8.97 (s, 1H), 8.67 (dd, J¼6.7, 2.5 Hz, 1H), 8.11 (dd, J¼7.3,
1.8 Hz,1H), 7.87 (d, J¼8.5 Hz,1H), 7.76 (td, J¼7.3, 1.2 Hz,1H), 7.74 (td,
J¼7.6, 1.8 Hz, 1H), 7.74 (d, J¼6.7 Hz, 1H), 7.61 (s, 1H), 2.78 (s, 3H); 13
C
NMR (125 MHz, CDCl3):
d 136.69, 134.27, 132.31, 129.37, 129.34,
128.71, 128.04, 127.78, 127.35, 125.97, 124.97, 122.93, 119.76, 108.93,
20.26.
4.4.8.2. trans-3-(2-(3-Cyanophenanthren-9-yl)vinyl)furan trans-
1y. 1H NMR (500 MHz, CDCl3):
d
8.98 (s, 1H), 8.69 (d, J¼8.3 Hz, 1H),

1758
Y.-Z. Chen et al. / Tetrahedron 70 (2014) 1748e1762
8.27 (d, J¼7.7 Hz, 1H), 7.95 (dd, J¼8.3, 2.2 Hz, 1H), 7.91 (d, J¼2.2 Hz,
1H), 7.80e7.72 (m, 3H), 7.65 (s, 1H), 7.55 (d, J¼16.0 Hz, 1H), 7.50 (s,
1H), 7.15 (d, J¼16.0 Hz, 1H), 6.80 (d, J¼1.7 Hz, 1H).
hexane for elution. Following chromatography, 34.3 mg of 2r was
obtained, and the yield was 37.5%.
4.5.4. Spectral data of compound 2aej, 2l, 2o, 2ret, and 2vey. 2-
Methoxy-7-methylnaphthalene 2a: 1H NMR (500 MHz, CDCl3):
4.5. Procedures for photorearrangement of compound 1
d
7.72 (d, J¼8.5 Hz, 1H), 7.69 (d, J¼8.5 Hz, 1H), 7.54 (s, 1H), 7.20 (d,
J¼8.8 Hz, 1H), 7.11 (d, J¼8.8 Hz, 1H), 7.09 (s, 1H), 3.93 (s, 3H), 2.52 (s,
3H); 13C NMR (125 MHz, CDCl3):
157.69, 136.01, 134.79, 129.06,
4.5.1. General procedures for irradiation in the presence of 10% KO-
H(aq)/MeOH. Here, the irradiation of 3-(2-naphthalen-1-ylvinyl)
d
furan 1r is employed as an example to describe the general ex-
perimental procedures, as follows: A total of five identical samples
were prepared, each of which contained 1r (20 mg), methanol
(19 mL), and 10% KOH(aq) (1 mL) in a quartz tube (1.5ꢂ20 cm).
The tubes were sealed with septa and subjected to sonication to
dissolve all of the components. Then, the solution was bubbled
with nitrogen gas for 20 min to remove dissolved oxygen.
The sample was irradiated with 300 nm UV light at ambient
temperature (approximately 40 ꢀC) for 6 h. After irradiation,
the five samples were combined, and 500 mL of water was
added to the solution. The resulting solution was extracted with
ethyl acetate several times, and the organic layers were then
combined and dried with anhydrous magnesium sulfate. The
solvent was removed with a rotary evaporator, and the products
were purified via chromatography using hexane for elution. Fol-
lowing chromatography, 26.5 mg of 2r was obtained, and the yield
was 29%.
127.43, 125.85, 125.81, 117.65, 105.30, 54.23, 21.71; MS (EI, 70 eV) m/
z 173 (Mþþ1, 6), 172 (Mþ, 100), 155 (12), 129 (30); HRMS (C12H12O)
calcd: 172.0883, found: 172.0887.
4.5.4.1. 2-Methyl-7-trifluoromethoxynaphthalene 2b. 1H NMR
(500 MHz, CDCl3):
7.61 (s,1H), 7.59 (s,1H), 7.36 (dd, J¼8.4,1.4 Hz,1H), 7.28 (d, J¼8.9 Hz,
1H), 2.54 (s, 3H); 13C NMR (125 MHz, CDCl3):
146.98, 146.97,
d
7.83 (d, J¼8.9 Hz, 1H), 7.77 (d, J¼8.4 Hz, 1H),
d
136.93, 133.81, 129.99, 129.65, 128.62, 127.55, 126.73, 121.69, 119.64,
119.15, 117.49, 21.67; MS (EI, 70 eV) m/z 227 (Mþþ1, 13), 226 (Mþ,
100), 225 (Mþꢁ1, 42), 141 (40), 129 (17); HRMS (C12H9F3O) calcd:
226.0605, found: 226.0608.
4.5.4.2. 2-tert-Butyl-7-methylnaphthalene 2c. 1H NMR (500
MHz, CDCl3):
1H), 7.61 (s, 1H), 7.52 (dd, J¼8.5, 1.9 Hz, 1H), 7.28 (dd, J¼8.2, 1.3 Hz,
1H), 2.52 (s, 3H), 1.44 (s, 9H); 13C NMR (125 MHz, CDCl3):
148.48,
d
7.76 (d, J¼8.5 Hz, 1H), 7.72 (d, J¼8.2 Hz, 1H), 7.71 (s,
d
135.29, 133.58, 129.85, 127.44, 127.20, 127.11, 126.88, 123.84, 122.21,
4.5.2. General procedures for irradiation in the presence of lithium
borohydride in methanol. Here, the irradiation of 3-(2-naphthalen-
1-ylvinyl)furan 1r is used as an example to describe the general
experimental procedures, as follows: A total of five identical
samples were prepared, each of which contained 1r (20 mg),
methanol (18 mL), 50% KOH(aq) (2 mL), and lithium borohydride
(40 mg) (CAUTION: the addition of lithium borohydride sometimes
causes flames for a short while) in a quartz tube (1.5ꢂ20 cm). The
tubes were sealed with septa and subjected to sonication to dis-
solve all of the components. Then, the solution was bubbled with
nitrogen gas for 20 min to remove dissolved oxygen. The sample
was irradiated with 300 nm UV light at ambient temperature
(approximately 40 ꢀC) for a certain time. After irradiation, the five
samples were combined, and 500 mL of water was added to the
solution. The resulting solution was extracted with ethyl acetate
several times, and the organic layers were combined and dried
with anhydrous magnesium sulfate. The solvent was removed
with a rotary evaporator, and the products were purified via
chromatography using a mixed solvent of hexane and ethyl ace-
tate (4:1) for elution. Following chromatography, 4.5 mg of 2r and
44.6 mg of 3r were obtained, and the yields were 5% and 44%,
respectively.
34.79, 31.25, 21.71; MS (EI, 70 eV) m/z 199 (Mþþ1, 3), 198 (Mþ, 44),
183 (100), 155 (18); HRMS (C15H18
198.1409.
) calcd: 198.1409, found:
4.5.4.3. 2-Isopropyl-7-methylnaphthalene 2d. 1H NMR (500
MHz, CDCl3):
d
7.78 (d, J¼8.5 Hz, 1H), 7.74 (d, J¼8.2 Hz, 1H), 7.61 (s,
2H), 7.37 (dd, J¼8.5, 1.6 Hz, 1H), 7.30 (dd, J¼8.2, 1.3 Hz, 1H), 3.10
(heptet, J¼6.9 Hz, 1H), 2.55 (s, 3H), 1.39 (d, J¼6.9 Hz, 6H); 13C NMR
(125 MHz, CDCl3):
d 146.31, 135.33, 133.85, 130.30, 127.50, 127.33,
127.29, 126.55, 124.82, 123.43, 34.22, 23.94, 21.70; MS (EI, 70 eV) m/
z 185 (Mþþ1, 3), 184 (Mþ, 74), 169 (100), 154 (31); HRMS (C14H16
)
calcd: 184.1252, found: 184.1253.
4.5.4.4. 2-Methyl-7-propylnaphthalene 2e. 1H NMR (500 MHz,
CDCl3):
d
7.75 (d, J¼7.6 Hz, 1H), 7.73 (d, J¼7.6 Hz, 1H), 7.58 (s, 1H),
7.56 (s, 1H), 7.29 (dd, J¼8.5, 1.6 Hz, 1H), 7.28 (dd, J¼8.5, 1.3 Hz, 1H),
2.77 (t, J¼7.5 Hz, 2H), 2.53 (s, 3H), 1.77 (sextet, J¼7.4 Hz, 2H), 1.01 (t,
J¼7.5 Hz, 3H).
4.5.4.5. 2-Ethyl-7-methylnaphthalene 2f. 1H NMR (500 MHz,
CDCl3):
d
7.74 (d, J¼8.8 Hz, 1H), 7.72 (d, J¼8.5 Hz, 1H), 7.57 (s, 1H),
7.56 (s, 1H), 7.30 (dd, J¼8.5, 1.9 Hz, 1H), 7.27 (dd, J¼8.5, 1.6 Hz, 1H),
2.82 (q, J¼7.5 Hz, 2H), 2.52 (s, 3H), 1.34 (t, J¼7.5 Hz, 3H); 13C NMR
4.5.3. General procedures for irradiation in the presence of DBU in
benzene. Here, the irradiation of 3-(2-naphthalen-1-ylvinyl)furan
1r is employed as an example to describe the general experimental
procedures, as follows: A total of five identical samples were pre-
pared, each of which contained 1r (20 mg, 0.37 mmol), 1,8-
diazabicyclo[5.4.0]undec-7-ene (DBU, 70 mg), ethanol (2 drops),
and benzene (20 mL) in a quartz tube (1.5ꢂ20 cm). The tubes were
sealed with septa and subjected to sonication to dissolve all of the
components. Then, the solution was bubbled with nitrogen gas for
20 min to remove dissolved oxygen. The sample was irradiated
with 300 nm UV light at ambient temperature (approximately
40 ꢀC) for a certain time. After irradiation, the five samples were
combined, and 500 mL of water was added to the solution. The
resulting solution was extracted with ethyl acetate several times,
and the organic layers were combined and dried with anhydrous
magnesium sulfate. The solvent was removed with a rotary evap-
orator, and the products were purified via chromatography using
(125 MHz, CDCl3): d 141.76, 135.37, 133.90, 130.14, 127.47, 127.37,
127.25, 126.38, 126.16, 124.89, 29.05, 21.71, 15.54; MS (EI, 70 eV) m/z
171 (Mþþ1, 10), 170 (Mþ, 96), 155 (100); HRMS (C13H14) calcd:
170.1096, found: 170.1097.
4.5.4.6. 2,7-Dimethylnaphthalene 2g. 1H NMR (500 MHz,
CDCl3):
d
7.72 (d, J¼8.3 Hz, 2H), 7.55 (s, 2H), 7.27 (d, J¼8.3 Hz, 2H),
2.53 (s, 6H); 13C NMR (125 MHz, CDCl3):
d 135.41, 133.89, 129.93,
127.38, 127.20, 126.20, 21.70; MS (EI, 70 eV) m/z 157 (Mþþ1, 5), 156
(Mþ, 100), 142 (25), 141 (90); HRMS (C12H12) calcd: 156.0939,
found: 156.0939.
4.5.4.7. 2-Methylnaphthalene 2h. 1H NMR (500 MHz, CDCl3):
d
7.82 (d, J¼8.0 Hz, 1H), 7.78 (d, J¼8.0 Hz, 1H), 7.77 (d, J¼8.2 Hz, 1H),
7.64 (s, 1H), 7.47e7.43 (m, 2H), 7.34 (dd, J¼8.5, 1.3 Hz, 1H), 2.54 (s,
1H); 13C NMR (125 MHz, CDCl3):
135.41, 133.65, 131.69, 128.08,
127.66, 127.57, 127.20, 126.81, 125.83, 124.92, 21.68; MS (EI, 70 eV)
d

Y.-Z. Chen et al. / Tetrahedron 70 (2014) 1748e1762
1759
m/z 142 (Mþ, 100), 141 (Mþꢁ1, 90), 115 (13); HRMS (C12H12) calcd:
(Mþ, 57), 153 (58), 57 (100); HRMS (C13H12) calcd: 168.0939, found:
168.0940.
142.0783, found: 142.0780.
4.5.4.8. 2-Fluoro-7-methylnaphthalene 2i. 1H NMR (500 MHz,
4.5.4.16. 2-Methyltriphenylene 2x.42 1H NMR (500 MHz, CDCl3):
CDCl3):
d
7.78 (dd, J¼9.0, 3.3 Hz, 1H), 7.74 (d, J¼8.4 Hz, 1H), 7.57
d
8.68e8.60 (m, 4H), 8.55 (d, J¼8.6 Hz, 1H), 8.45 (s, 1H), 7.67e7.61
(m, 4H), 7.49 (dd, J¼8.4,1.2 Hz,1H), 2.62 (s, 3H); 13C NMR (125 MHz,
(s, 1H), 7.38 (dd, J¼10.1, 2.6 Hz, 1H), 7.29 (d, J¼8.6, 1.4 Hz, 1H),
7.20 (td, J¼8.7, 2.6 Hz, 1H), 2.53 (s, 1H); 13C NMR (125 MHz, CDCl3):
CDCl3):
d 129.89, 129.75, 129.69, 129.40, 128.68, 127.47, 127.14,
d
160.77 (d, JCeF¼242.5 Hz), 136.67, 134.41 (d, JCeF¼10.0 Hz), 129.91
127.07, 127.06, 126.76, 123.30, 123.28, 123.24, 123.06, 21.83.
(d, JCeF¼8.8 Hz), 128.67, 127.64, 127.38 (d, JCeF¼2.5 Hz), 126.24
(d, JCeF¼5.0 Hz), 115.25 (d, JCeF¼26.3 Hz), 110.21 (d, JCeF¼20.0 Hz),
21.68; MS (EI, 70 eV) m/z 160 (Mþ, 100), 159 (Mþꢁ1, 95), 70 (59), 61
(65); HRMS (C11H9F) calcd: 160.0688, found: 160.0686.
4.5.4.17. 2-Methyl-10-cyanotriphenylene 2y. 1H NMR (500 MHz,
CDCl3):
d
8.94 (s, 1H), 8.70 (d, J¼8.5 Hz, 1H), 8.63 (d, J¼8.3 Hz, 1H),
8.57 (d, J¼8.0 Hz, 1H), 8.56 (d, J¼8.4 Hz, 1H), 8.41 (s, 1H), 7.83 (d,
J¼8.4 Hz, 1H), 7.72 (td, J¼7.8, 1.5 Hz, 1H), 7.69 (td, J¼7.8, 1.4 Hz, 1H),
7.58 (dd, J¼8.4, 1.2 Hz, 1H), 2.63 (s, 3H); 13C NMR (125 MHz, CDCl3):
4.5.4.9. 2-Chloro-7-methylnaphthalene 2j.40 (Record the spec-
tral data from the mixture of 2h and 2j) 1H NMR (500 MHz, CDCl3):
d
137.57, 132.87, 130.39, 130.24, 130.10, 128.84, 128.53, 128.40,
d
7.74 (s, 1H), 7.73 (d, J¼8.5 Hz, 1H), 7.72 (d, J¼8.5 Hz, 1H), 7.53 (s,
128.37, 128.34, 127.84, 127.44, 124.29, 123.91, 123.49, 123.27, 123.24,
119.42, 110.41, 29.69.
1H), 7.38e7.33 (m, 2H), 2.52 (s, 3H); MS (EI, 70 eV) m/z 178 (Mþþ2,
24), 176 (Mþ, 63), 141 (100), 139 (25), 115 (25); HRMS (C11H9Cl)
calcd: 176.0393, found: 176.0395.
4.5.5. Spectral data of compound 3a, 3gej, 3l, 3neo, and 3rew
4.5.5.1. 2-(7-Methoxynaphthalen-2-yl)ethanol
(500 MHz, CDCl3):
3a. 1H
NMR
4.5.4.10. 2-Cyano-7-methylnaphthalene 2l.41 1H NMR (500 MHz,
CDCl3):
7.66 (s,1H), 7.54 (d, J¼8.5 Hz,1H), 7.48 (d, J¼8.5 Hz,1H), 2.55 (s,1H);
MS (EI, 70 eV) m/z 168 (Mþþ1, 8), 167 (Mþ, 100), 166 (Mþꢁ1, 50),
140 (14), 131 (60); HRMS (C12H9N) calcd: 167.0735, found:
167.0734.
d
7.72 (d, J¼8.4 Hz, 1H), 7.71 (d, J¼8.7 Hz, 1H),
d
8.14 (s, 1H), 7.86 (d, J¼8.5 Hz, 1H), 7.79 (d, J¼8.5 Hz, 1H),
7.58 (s, 1H), 7.21 (dd, J¼8.4, 1.0 Hz, 1H), 7.12 (dd, J¼8.9, 2.5 Hz, 1H),
7.10 (d, J¼2.2 Hz, 1H), 3.92 (t, J¼6.5 Hz, 2H), 3.91 (s, 3H), 3.00 (t,
J¼6.5 Hz, 2H); 13C NMR (125 MHz, CDCl3):
d 157.79, 136.51, 134.70,
129.08, 127.93, 127.70, 126.40, 125.05, 118.21, 105.43, 63.46, 55.22,
39.30; MS (EI, 70 eV) m/z 202 (Mþ, 16), 171 (100), 128 (4); HRMS
(C13H14O2) calcd: 202.0994, found: 202.0992.
4.5.4.11. 5-Methylbenzothiophene 2o. 1H NMR (500 MHz,
CDCl3):
d
7.76 (d, J¼8.2 Hz, 1H), 7.63 (s, 1H), 7.41 (d, J¼5.4 Hz, 1H),
4.5.5.2. 2-(7-Methylnaphthalen-2-yl)ethanol
(500 MHz, CDCl3):
3g. 1H
NMR
7.26 (dd, J¼5.4, 0.7 Hz, 1H), 7.18 (dd, J¼8.2, 1.7 Hz, 1H), 2.48 (s, 1H);
d
7.75 (d, J¼8.3 Hz, 1H), 7.71 (d, J¼8.3 Hz, 1H),
13C NMR (125 MHz, CDCl3):
d 139.93, 136.87, 133.83, 126.35, 125.96,
7.59 (s, 1H), 7.56 (s, 1H), 7.28 (dt, J¼8.2, 2.3 Hz, 2H), 3.94 (t, J¼6.5 Hz,
123.50, 123.46, 122.05, 21.34; MS (EI, 70 eV) m/z 148 (Mþ, 71), 147
(Mþꢁ1, 100), 121 (2); HRMS (C9H8S) calcd: 148.0341, found:
148.0341.
2H), 3.02 (t, J¼6.5 Hz, 2H), 2.53 (s, 3H); 13C NMR (125 MHz, CDCl3):
d
135.90, 135.71, 133.77, 130.49, 127.93, 127.72, 127.41, 126.82,
126.45, 126.41, 63.50, 39.33, 21.68.
4.5.4.12. 2-Methylphenanthrene 2r. 1H NMR (500 MHz, CDCl3):
4.5.5.3. 2-(Naphthalen-2-yl)ethanol 3h.43 1H NMR (500 MHz,
d
8.66 (d, J¼8.3 Hz, 1H), 8.58 (d, J¼8.4 Hz, 1H), 7.88 (d, J¼7.9 Hz, 1H),
CDCl3):
d
7.84e7.78 (m, 3H), 7.69 (s, 1H), 7.48 (td, J¼7.5, 1.3 Hz, 1H),
7.72 (d, J¼8.9 Hz, 1H), 7.69e7.72 (m, 3H), 7.60e7.56 (m, 1H), 7.49 (d,
J¼8.4 Hz, 1H), 2.57 (s, 1H); 13C NMR (125 MHz, CDCl3):
d 136.27,
7.45 (td, J¼7.5, 1.3 Hz, 1H), 7.37 (dd, J¼8.6, 1.5 Hz, 1H), 3.96 (t,
J¼6.5 Hz, 2H), 3.04 (t, J¼6.5 Hz, 2H); 13C NMR (125 MHz, CDCl3):
132.18, 131.71, 130,34, 128.49, 128.30, 128.11, 126.88, 126.65, 126.45,
126.08, 122.53, 122.43, 21.43; MS (EI, 70 eV) m/z 192 (Mþ, 79), 105
(46), 57 (100); HRMS (C15H12) calcd: 192.0939, found: 192.0935.
d
135.92, 133.56,132.27, 128.27,127.64, 127.47, 127.37,126.09,125.47,
63.52, 39.32; MS (EI, 70 eV) m/z 173 (Mþþ1, 2), 172 (Mþ, 32), 142
(21), 141 (100), 115 (13); HRMS (C12H12O) calcd: 172.0888, found:
172.0888.
4.5.4.13. 2-Methyl-4H-cyclopenta[def]phenanthrene 2s. 1H NMR
(500 MHz, CDCl3):
7.67 (d, J¼7.0 Hz, 1H), 7.63 (s, 1H), 7.61 (d, J¼7.0 Hz, 1H), 7.54 (s, 1H),
4.30 (s, 2H), 2.67 (s, 3H); 13C NMR (125 MHz, CDCl3):
141.85,
141.68, 138.33, 137.26, 136.48, 127.79, 127.53, 126.74, 125.24, 124.97,
122.99,122.50,122.25,121.12, 37.26, 29.70, 22.76; MS (EI, 70 eV) m/z
205 (Mþþ1, 20), 204 (Mþ, 100), 189 (61); HRMS (C16H12) calcd:
204.0939, found: 204.0938.
d
7.82 (d, J¼8.6 Hz, 2H), 7.77 (d, J¼8.9 Hz, 1H),
4.5.5.4. 2-(7-Fluoronaphthalen-2-yl)ethanol
(500 MHz, CDCl3):
3i. 1H
NMR
d
7.80 (dd, J¼8.9, 5.9 Hz, 1H), 7.79 (d, J¼8.6 Hz,
d
1H), 7.62 (s, 1H), 7.40 (dd, J¼9.9, 2.3 Hz, 1H), 7.32 (dd, J¼8.4, 1.5 Hz,
1H), 7.22 (td, J¼8.8, 2.5 Hz, 1H), 3.95 (t, J¼6.5 Hz, 2H), 3.03 (t,
J¼6.5 Hz, 2H); 13C NMR (125 MHz, CDCl3):
d 160.82 (d,
JCeF¼244.1 Hz), 137.24, 134.33 (d, JCeF¼8.9 Hz), 130.00 (d,
JCeF¼8.7 Hz), 129.23, 128.19, 126.83 (d, JCeF¼5.1 Hz), 126.67 (d,
JCeF¼2.4 Hz), 115.80 (d, JCeF¼25.0 Hz), 110.48 (d, JCeF¼20.4 Hz),
63.41, 39.25; MS (EI, 70 eV) m/z 191 (Mþþ1, 3), 190 (Mþ, 71), 160
(71), 159 (100), 133 (53); HRMS (C12H11FO) calcd: 190.0794, found:
190.0793.
4.5.4.14. 5-Methyl-2,3-dihydro-1H-phenalene
(500 MHz, CDCl3):
2t. 1H
NMR
d
7.56 (d, J¼8.2 Hz, 1H), 7.43 (s, 1H), 7.31 (t,
J¼8.2 Hz, 1H), 7.13 (d, J¼6.9 Hz, 1H), 7.06 (s, 1H), 3.08 (t, J¼6.1 Hz,
2H), 3.06 (t, J¼6.1 Hz, 2H), 2.46 (s, 3H), 2.06 (quintet, J¼6.2 Hz, 2H);
13C NMR (125 MHz, CDCl3):
d 136.25, 136.17, 134.92, 133.97, 128.29,
4.5.5.5. 2-(7-Chloronaphthalen-2-yl)ethanol 3j. (Record the
spectral data from the mixture of 3h and 3j) 1H NMR (500 MHz,
126.03, 125.46, 125.13, 124.79, 122.93, 31.22, 31.19, 23.18, 21.64; MS
(EI, 70 eV) m/z 182 (Mþ, 11), 183 (Mþꢁ1, 12), 134 (68), 57 (100);
HRMS (C14H14) calcd: 182.1096, found: 182.1095.
CDCl3):
d
7.78 (d, J¼8.4 Hz, 1H), 7.77 (d, J¼2.0 Hz, 1H), 7.75 (d,
J¼8.7 Hz, 1H), 7.60 (s, 1H), 7.37 (d, J¼8.2 Hz, 2H), 3.95 (t, J¼6.5 Hz,
2H), 3.03 (t, J¼6.5 Hz, 2H); MS (EI, 70 eV) m/z 208 (Mþþ2, 17), 206
(Mþ, 41), 174 (47), 170 (92), 141 (100).
4.5.4.15. 4-Methylacenaphthene 2v. 1H NMR (500 MHz, CDCl3):
d
7.49 (d, J¼8.2 Hz, 1H), 7.39 (t, J¼7.5 Hz, 1H), 7.36 (s, 1H), 7.20 (d,
J¼6.8 Hz, 1H), 7.12 (s, 1H), 3.40e3.34 (m, 4H), 2.52 (s, 3H); 13C NMR
(125 MHz, CDCl3):
d
145.99, 145.64, 137.75, 131.58, 127.86, 121.52,
4.5.5.6. 2-(7-Cyanonaphthalen-2-yl)ethanol
3l. 1H
NMR
121.37, 121.30, 118.27, 30.49, 30.11, 22.38; MS (EI, 70 eV) m/z 168
(500 MHz, CDCl3):
d
8.18 (s, 1H), 7.89 (d, J¼8.5 Hz, 1H), 7.85 (d,

1760
Y.-Z. Chen et al. / Tetrahedron 70 (2014) 1748e1762
J¼8.4 Hz,1H), 7.74 (s,1H), 7.57 (dd, J¼8.4,1.7 Hz,1H), 7.55 (dd, J¼8.4,
1.7 Hz, 1H), 3.98 (t, J¼6.5 Hz, 2H), 3.07 (t, J¼6.5 Hz, 2H); 13C NMR
128.1, 122.1, 121.8, 120.7, 118.8, 63.8, 40.0, 30.5, 30.2; MS (EI, 70 eV)
m/z 198 (Mþ, 38), 167 (100), 152 (30); HRMS (C14H14O) calcd:
198.1045, found: 198.1047.
(125 MHz, CDCl3):
d 138.43, 133.71, 133.48, 130.69, 128.92, 128.29,
127.84, 127.00, 125.97, 119.27, 109.53, 63.22, 39.11; MS (EI, 70 eV) m/
z 198 (Mþþ1, 2), 197 (Mþ, 11), 167 (48), 166 (100), 140 (18); HRMS
(C13H11NO) calcd: 197.0841, found: 197.0829.
4.5.6. Spectral data of methanol addition compounds
4.5.6.1. 3-(1-Methoxy-2-(4-methoxyphenyl)ethyl)furan
NMR (500 MHz, CDCl3):
4a. 1H
d
7.40 (s, 1H), 7.23 (s, 1H), 7.05 (d, J¼8.7 Hz,
4.5.5.7. 2-Benzofuran-5-ylethanol 3n. 1H NMR (500 MHz,
2H), 6.80 (d, J¼8.7 Hz, 2H), 6.36 (s,1H), 4.29 (t, J¼6.8 Hz,1H), 3.79 (s,
3H), 3.23 (s, 3H), 3.08 (dd, J¼13.8, 6.8 Hz, 1H), 2.73 (dd, J¼13.8,
6.7 Hz, 1H).
CDCl3):
d
7.61 (d, J¼2.2 Hz, 1H), 7.46e7.42 (m, 2H), 7.15 (dd, J¼8.6,
1.7 Hz, 1H), 6.73 (dd, J¼2.2, 1.0 Hz, 1H), 3.88 (t, J¼6.5 Hz, 2H), 2.96 (t,
J¼6.5 Hz, 2H); 13C NMR (125 MHz, CDCl3):
d 153.93, 145.28, 132.82,
4.5.6.2. 3-(2-Methoxy-2-(4-methoxyphenyl)ethyl)furan 4a0. 1H
127.74, 125.28, 111.34, 106.35, 64.02, 39.03; MS (EI, 70 eV) m/z 162
(Mþ, 10), 132 (4), 131 (100), 103 (2), 77 (3); HRMS (C10H10O2) calcd:
162.0675, found: 162.0678.
NMR (500 MHz, CDCl3):
d
7.30 (s, 1H), 7.20 (d, J¼8.6 Hz, 2H), 7.15 (s,
1H), 6.89 (d, J¼8.6 Hz, 2H), 6.17 (s, 1H), 4.22 (t, J¼6.7 Hz, 1H), 3.82 (s,
3H), 3.22 (s, 3H), 2.93 (dd, J¼14.6, 7.3 Hz, 1H), 2.73 (dd, J¼14.6,
4.5.5.8. 2-Benzothiophen-5-ylethanol 3o. 1H NMR (500 MHz,
6.1 Hz, 1H); 13C NMR (125 MHz, CDCl3):
d 159.14, 142.25, 139.95,
CDCl3):
d
7.83 (d, J¼8.2 Hz, 1H), 7.68 (d, J¼0.8 Hz, 1H), 7.44 (dd,
133.52, 127.97, 121.30, 113.66, 111.60, 83.62, 56.37, 55.17, 33.62;
MS(EI, 70 eV) m/z 232 (Mþ, 2), 201 (2), 185 (3), 173 (4), 151 (100);
HRMS (C14H16O3) calcd: 232.1099, found: 232.1101.
J¼5.5, 0.3 Hz, 1H), 7.30 (dd, J¼5.5, 0.7 Hz, 1H), 7.22 (dd, J¼8.2, 1.5 Hz,
1H), 3.89 (t, J¼6.5 Hz,1H), 2.98 (t, J¼6.5 Hz,1H); 13C NMR (125 MHz,
CDCl3):
d 139.91, 137.83, 134.48, 126.67, 125.48, 123.70, 123.49,
122.43, 63.69, 38.96; MS (EI, 70 eV) m/z 178 (Mþ, 10), 148 (4), 147
4.5.6.3. 3-(1-Methoxy-2-(4-nitrophenyl)ethyl)furan 4m. 1H NMR
(100), 131 (3); HRMS (C10H10OS) calcd: 178.0447, found: 178.0453.
(500 MHz, CDCl3):
d
8.19 (d, J¼8.8 Hz, 2H), 7.41 (d, J¼8.8 Hz, 2H),
7.31 (t, J¼1.6 Hz, 1H), 7.12 (dd, J¼1.6, 0.6 Hz, 1H), 6.16 (d, J¼0.9 Hz,
1H), 4.38 (t, J¼6.5 Hz, 1H), 3.27 (s, 3H), 2.92 (dd, J¼14.8, 6.9 Hz, 1H),
2.75 (dd, J¼14.8, 6.0 Hz, 1H).
4.5.5.9. 2-Phenanthren-2-ylethanol 3r. 1H NMR (500 MHz,
CDCl3):
d
8.64 (d, J¼8.3 Hz, 1H), 8.62 (d, J¼8.5 Hz, 1H), 7.87 (dd,
J¼7.8, 1.0 Hz, 1H), 7.74e7.71 (m, 2H), 7.68 (d, J¼8.9 Hz, 1H), 7.63 (t,
J¼8.3 Hz, 1H), 7.57 (t, J¼8.3 Hz, 1H), 7.52 (dd, J¼1.7, 8.4 Hz, 1H), 3.97
(t, J¼6.5 Hz, 2H), 3.07 (t, J¼6.5 Hz, 2H); 13C NMR (125 MHz, CDCl3):
4.6. Synthesis of the N3h and N3r intermediates
d
136.83, 132.24, 131.85, 130.21, 128.95, 128.55, 128.47, 127.78,
t
127.18, 126.64, 126.59, 126.38, 123.04, 122.51, 63.63, 39.11; MS (EI,
70 eV) m/z 223 (Mþþ1, 9), 222 (Mþ, 52), 191 (100), 189 (50); HRMS
(C16H14O) calcd: 222.1045, found: 222.1046.
4.6.1. Photolysis of 1h in the presence of BuOK/dried THF. A total of
five identical samples were prepared, each of which contained 1h
t
(20 mg), BuOK (0.5 g), and dried THF (20 mL) in a quartz tube
(1.5ꢂ20 cm). The tubes were sealed with septa and sonicated and
shaken to suspend the undissolved particles. Then, the solution was
bubbled with nitrogen gas for 20 min to remove dissolved oxygen.
The sample was irradiated with 300 nm UV light at ambient tem-
perature (approximately 40 ꢀC) for 3 h. After irradiation, the five
samples were combined, and 500 mL of water was added to the
solution. The resulting solution was extracted with ethyl acetate
several times, and the organic layers were combined and dried with
anhydrous magnesium sulfate. The solvent was removed with
a rotary evaporator, and the products were purified via chroma-
tography using a mixed solution of ethyl acetate and hexane (1:10)
for elution. Further purification was conducted via thin-layer-
chromatography (TLC) to achieve an acceptable purity, 8.3 mg (8%
yield) of N3h and 10.8 mg (12% yield) of 5h were obtained.
4.5.5.10. 2-(4H-Cyclopenta[def]phenanthren-2-yl)ethanol 3s. 1H
NMR (500 MHz, CDCl3):
d
7.82 (d, J¼8.9 Hz, 1H), 7.80 (d, J¼7.4 Hz,
1H), 7.77 (d, J¼8.9 Hz, 1H), 7.67 (d, J¼7.4 Hz, 1H), 7.66 (s, 1H), 7.61 (t,
J¼7.4 Hz, 1H), 7.57 (s, 1H), 4.32 (s, 2H), 3.98 (t, J¼6.5 Hz, 2H), 3.15 (t,
J¼6.5 Hz, 2H); 13C NMR (125 MHz, CDCl3):
d 143.33, 141.70, 138.20,
137.81, 137.27, 127.83, 127.72, 127.06, 125.56, 124.97, 122.87, 122.64,
122.59, 121.28, 64.26, 40.43, 37.37; MS (EI, 70 eV) m/z 235 (Mþþ1,
13), 234 (Mþ, 64), 203 (100), 202 (92), 189 (18); HRMS (C17H14O)
calcd: 234.1045, found: 234.1043.
4.5.5.11. 2-(5,6-Dihydro-4H-phenalen-2-yl)ethanol 3t. 1H NMR
(500 MHz, CDCl3):
d
7.60 (d, J¼8.2 Hz, 1H), 7.49 (s, 1H), 7.34 (t,
J¼7.0 Hz, 1H), 7.17 (dd, J¼6.9, 0.9 Hz, 1H), 7.09 (s, 1H), 3.92 (t,
J¼6.5 Hz, 2H), 3.08 (t, J¼6.1 Hz, 4H), 2.97 (t, J¼6.5 Hz, 2H), 2.06
(quintet, J¼6.2 Hz, 2H); 13C NMR (125 MHz, CDCl3):
d
136.87,136.33,
4.6.1.1. Naphthalen-2-yl-acetaldehyde
(500 MHz, CDCl3):
(s, 1H), 7.53e7.47 (m, 2H), 7.34 (dd, J¼8.4, 1.8 Hz, 1H), 3.86 (d,
J¼2.4 Hz, 1H).
N3h.44 1H
NMR
135.33, 133.85, 128.92, 125.71, 125.43, 125.38, 125.27, 123.44, 63.52,
39.30, 31.24, 31.17, 23.09; MS (EI, 70 eV) m/z 213 (Mþþ1, 14), 212
(Mþ, 83), 181 (100), 165 (51); HRMS (C15H16O) calcd: 212.1201,
found: 212.1202.
d
9.84 (t, J¼2.4 Hz, 1H), 7.91e7.81 (m, 3H), 7.71
4.6.1.2. Naphthalene-2-carbaldehyde 5h.45 1H NMR (500 MHz,
4.5.5.12. 2-(8-Methoxy-5,6-dihydro-4H-phenalen-2-yl)ethanol
CDCl3):
d
10.18 (s, 1H), 8.02 (d, J¼8.2 Hz, 1H), 7.97 (dd, J¼8.6, 1.5 Hz,
3u. 1H NMR (500 MHz, CDCl3):
d
7.38 (s, 1H), 6.94 (d, J¼1.2 Hz, 1H),
1H), 7.95 (d, J¼8.6 Hz, 2H), 7.92 (d, J¼8.2 Hz, 1H), 7.66 (td, J¼8.2,
1.3 Hz, 1H), 7.60 (td, J¼8.2, 1.2 Hz, 1H).
6.92 (d, J¼2.5 Hz, 1H), 6.85 (dt, J¼2.5, 1.2 Hz, 1H), 3.90 (t, J¼6.5 Hz,
2H), 3.87 (s, 3H), 3.05e3.01 (m, 4H), 2.94 (t, J¼6.5 Hz, 2H), 2.03
(quintet, J¼6.2 Hz, 2H); 13C NMR (125 MHz, CDCl3):
d
157.41, 138.21,
4.6.2. Photolysis of 1r in the presence of tBuOK/tBuOH. A total of five
identical samples were prepared, each of which contained 1r
(20 mg), tert-butyl alcohol (20 mL), and potassium tert-butoxide
(0.1 g) in a quartz tube (1.5ꢂ20 cm). The tubes were sealed with
septa and subjected to sonication to dissolve all of the components.
Then, the solution was bubbled with nitrogen gas for 20 min to
remove dissolved oxygen. The sample was irradiated with 300 nm
UV light at ambient temperature (approximately 40 ꢀC) for 6 h.
After irradiation, the five samples were combined, and 500 mL of
136.89, 136.10, 135.26, 124.55, 124.41, 123.17, 115.68, 103.55, 63.51,
55.12, 39.33, 31.13, 31.05, 23.09; MS (EI, 70 eV) m/z 242 (Mþ, 100),
211 (73), 165 (28).
4.5.5.13. 2-Acenaphthen-4-ylethanol 3v. 1H NMR (500 MHz,
CDCl3):
1H), 7.15 (s, 1H), 3.92 (t, J¼6.5 Hz, 2H), 3.37 (s, 4H), 3.01 (t, J¼6.5 Hz,
1H); 13C NMR (125 MHz, CDCl3):
146.7, 145.8, 138.4, 138.2, 131.5,
d
7.51 (d, J¼8.2 Hz, 1H), 7.42e7.38 (m, 2H), 7.22 (d, J¼6.8 Hz,
d

Y.-Z. Chen et al. / Tetrahedron 70 (2014) 1748e1762
1761
ꢀ
ꢀ
7. Selected papers: (a) Perez, D.; Guitian, E. Chem. Soc. Rev. 2004, 33, 274; (b) Cant,
A. A.; Roberts, L.; Greaney, M. F. Chem. Commun. 2010, 8671; (c) Xu, L.; Yu, R.;
Wang, Y.; Chen, J.; Yang, Z. J. Org. Chem. 2013, 78, 5744; (d) Liu, Z.; Larock, R. C. J.
Org. Chem. 2007, 72, 223.
water was added to the solution. The resulting solution was
extracted with ethyl acetate several times, and the organic layers
were combined and dried with anhydrous magnesium sulfate. The
solvent was removed with a rotary evaporator, and the products
were purified via chromatography using hexane and ethyl acetate
(10:1) for elution. Following chromatography, 3.3 mg (4% yield) of
5r and 24.3 mg (24% yield) of N3r were obtained.
8. (a) Jørgensen, K. B. Molecules 2010, 15, 4334; (b) Mallory, F. B.; Mallory, C. W.
Org. React. 1984, 30, 1; (c) Laarhoven, W. H. Pure Appl. Chem. 1984, 56, 1225.
9. (a) Shi, L.; Liu, Z.; Dong, G.; Duan, L.; Qiu, Y.; Jia, J.; Guo, W.; Zhao, D.; Cui, D.;
Tao, X. Chem.dEur. J. 2012, 18, 8092; (b) Braiek, M. B.; Aloui, F.; Moussa, S.;
Tounsi, M.; Marrot, J.; Hassine, B. B. Tetrahedron Lett. 2013, 54, 5421; (c) Zhao, Z.;
Zhang, Y.; Xiao, Y. J. Org. Chem. 2013, 78, 5544; (d) Lei, T.; Pei, J. J. Mater. Chem.
2012, 22, 785; (e) Toyoshima, T.; Yoshida, S.; Watanabe, S. Tetrahedron 2013, 69,
1904.
4.6.2.1. Phenanthren-2-yl-acetaldehyde N3r. 1H NMR (500 MHz,
CDCl3):
d
9.84 (t, J¼2.4 Hz, 1H), 8.67e8.64 (m, 2H), 7.88 (dd, J¼7.8,
10. (a) Baldry, P. J. J. Chem. Soc., Perkin Trans. 2 1980, 805; (b) Pomerantz, M.; Gruber,
G. W. J. Am. Chem. Soc. 1971, 93, 6615; (c) Baldry, P. J. J. Chem. Soc., Perkin Trans. 1
1975, 1913; (d) Olsen, R. J.; Minniear, J. C.; Overton, W. M.; Sherrick, J. M. J. Org.
Chem. 1991, 56, 989.
1.3 Hz, 1H), 7.76e7.57 (m, 4H), 7.47 (dd, J¼8.5, 1.9 Hz, 1H), 3.87 (d,
J¼2.4 Hz, 2H). 13C NMR (125 MHz, CDCl3):
d 199.25, 132.37, 131.99,
130.03, 130.01, 129.47, 129.26, 128.59, 127.92, 127.54, 126.74, 126.68,
126.45, 123.47, 122.59, 50.43; MS (EI, 70 eV) m/z 221 (Mþþ1, 15),
220 (Mþ, 85), 191 (100); HRMS (C16H12O) calcd: 220.0888, found:
220.0886.
11. According to our survey, there is no literature reporting about synthesizing 4H-
cyclopenta[def]phenanthrene by oxidative photocyclization of a stilbene-type
precursor. Instead, the synthesis of 4H-cyclopenta[def]phenanthrene can be
accomplished by multi-step syntheses from acenaphthene, fluorene derivative
or 1-naphthylacetic acid, or the reduction of cyclopenta[def]-phenanthren-4-
one. (a) Bachmann, W. E.; Sheehan, J. C. J. Am. Chem. Soc. 1941, 63, 204; (b)
Yoshida, M.; Minabe, M.; Suzuki, K. Bull. Chem. Soc. Jpn. 1983, 56, 2179; (c) Kim,
J.; Song, S.; Suh, H.; Jin, Y.; Kim, I. Chem. Lett. 2009, 38, 1008; (d) Medenwald, H.
Chem. Ber. 1953, 86, 287 By contrast, 4,5-dihydropyrene can be synthesized by
oxidative photocyclization of stilbene-type precursor; (e) Blaschke, H.; Ramey,
C. E.; Calder, I.; Boekelheide, V. J. Am. Chem. Soc. 1970, 92, 3675 Other cases of
oxidative photocyclization of macrocyclic stilbene derivatives: (f) Ben, I.; Cas-
4.6.2.2. Phenanthrene-2-carbaldehyde 5r. 1H NMR (500 MHz,
CDCl3):
d
10.21 (s, 1H), 8.79 (d, J¼8.6 Hz, 1H), 8.72 (dd, J¼7.6, 1.5 Hz,
1H), 8.37 (d, J¼1.7 Hz, 1H), 8.13 (dd, J¼8.6, 1.7 Hz, 1H), 7.92 (dd,
J¼7.2, 1.8 Hz, 1H), 7.85 (d, J¼8.9 Hz, 1H), 7.82 (d, J¼8.9 Hz, 1H), 7.71
(td, J¼7.1, 1.6 Hz, 1H), 7.68 (td, J¼7.1, 1.4 Hz, 1H). 13C NMR (125 MHz,
ꢀ
tedo, L.; Saa, J. M.; Seijas, J. A.; Suau, R.; Tojo, G. J. Org. Chem. 1985, 50, 2236; (g)
€
Dyker, G.; Korning, J.; Stirner, W. Eur. J. Org. Chem. 1998, 149.
CDCl3):
d 192.15 (d), 134.48, 134.35, 133.24, 133.00, 131.68, 129.73,
12. (a) Wright, D. L. In Progress in Heterocyclic Chemistry; Gribble, G. W., Joule, J. A.,
Eds.; Elsevier: Oxford, UK, 2005; Vol 17, Chapter 1; (b) Cermola, F.; Temussi, F.;
Iesce, M. R. Tetrahedron Lett. 2011, 52, 7058.
128.81, 128.28, 128.10, 127.20, 127.06, 124.77, 123.72, 123.50; MS (EI,
70 eV) m/z 206 (Mþ, 100), 205 (Mþꢁ1, 59), 176 (54); HRMS
(C15H10O) calcd: 206.0732, found: 206.0730.
ꢀ
13. Pilipenko, A. S.; Melchin, V. V.; Trushkov, I. V.; Cheshkov, D. A.; Butin, A. V.
Tetrahedron 2012, 68, 619.
ꢁ
ꢁ
ꢁ
ꢁ
ꢀ
ꢀ
14. Kikas, I.; Skoric, I.; Marinic, Z.; Sindler-Kulyk, M. Tetrahedron 2010, 66, 9405.
15. Ouairy, C.; Michel, P.; Delpech, B.; Crich, D.; Marazano, C. J. Org. Chem. 2010, 75,
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Acknowledgements
16. Ho, J.-H.; Lee, T.-H.; Lo, C.-K.; Chuang, C.-L. Tetrahedron Lett. 2011, 52, 7199.
17. Maercker, A. Org. React. 1965, 14, 270.
We are grateful to National Science Council of the Republic of
China (Taiwan) for financial support (NSC 98-2113-M-011-004-
MY2).
18. Yoshimi, Y.; Ishise, A.; Oda, H.; Moriguchi, Y.; Kanezaki, H.; Nakaya, Y.; Katsuno,
K.; Itou, T.; Inagaki, S.; Morita, T.; Hatanaka, M. Tetrahedron Lett. 2008, 49, 3400.
19. (a) Woning, J.; Oudenampsen, A.; Laarhoven, W. H. J. Chem. Soc., Perkin Trans. 2
1989, 2147; (b) Roberts, J. C.; Pincock, J. A. J. Org. Chem. 2004, 69, 4279; (c)
Roberts, J. C.; Pincock, J. A. J. Org. Chem. 2006, 71, 7480.
20. Lewis, F. D.; Yang, J.-S. J. Am. Chem. Soc. 1997, 119, 3834.
21. Bent, D. V.; Schulte-Frohlinde, D. J. Phys. Chem. 1974, 78, 446.
22. Tofi, M.; Georgiou, T.; Montagnon, T.; Vassilikogiannakis, G. Org. Lett. 2005, 7,
3347.
Supplementary data
1H and 13C NMR spectra of the compounds are available. Sup-
plementary data related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2014.01.035.
23. Efange, S. M. N.; Michelson, R. H.; Remmel, R. P.; Boudreau, R. J.; Dutta, A. K.;
Freshler, A. J. Med. Chem. 1990, 33, 3133.
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26. Schaffner, K.; Wolf, H.; Rosenfeld, S. M.; Lawler, R. G.; Ward, H. R. J. Am. Chem.
References and notes
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