Photocyclization reactions. Part 8 [1]. Synthesis of 2-quinolone, quinoline and coumarin derivatives using trans-cis isomerization by photoreaction

Article abstract of DOI:10.1002/jhet.5570390108

2-Quinolone 2, quinoline 3, coumarin (2H-1-benzopyran-2-one) 5, and 2H-1-benzopyran hemiacetal 6 were synthesized by photocyclization reaction of trans-o-aminocinnamoyl derivatives trans-1 and trans-o-hydroxycinnamoyl derivatives trans-4. The reaction proceeds through trans-cis isomerization followed by intramolecular cyclization.

Full text of DOI:10.1002/jhet.5570390108

Jan-Feb 2002
Photocyclization Reactions. Part 8 [1]. Synthesis of
2-Quinolone, Quinoline and Coumarin Derivatives Using
Trans-Cis Isomerization by Photoreaction
61
Takaaki Horaguchi* and Nobuyuki Hosokawa
Department of Chemistry, Faculty of Science, Niigata Univeristy, Ikarashi, Niigata 950-2181, Japan
Kiyoshi Tanemura and Tsuneo Suzuki
School of Dentistry at Niigata, The Nippon Dental University, Hamaura-cho 1-8, Niigata 951-8151, Japan
Received April 30, 2001
2-Quinolone 2, quinoline 3, coumarin (2H-1-benzopyran-2-one) 5, and 2H-1-benzopyran hemiacetal 6
were synthesized by photocyclization reaction of trans-o-aminocinnamoyl derivatives trans-1 and trans-o-
hydroxycinnamoyl derivatives trans-4. The reaction proceeds through trans-cis isomerization followed by
intramolecular cyclization.
J. Heterocyclic Chem., 39, 61 (2002).
Introduction.
Results and Discussion.
Starting materials trans-1a, trans-1b, trans-1d, trans-
1e, and trans-4a for photoreactions were prepared as
shown in Scheme 2 (see Experimental). Compounds trans-
4b [10], trans-4d [11], and trans-4e [12] were synthesized
according to the literature. Compound trans-4c is commer-
cially available.
First, photoreactions of ethyl trans-o-aminocinnnamate
trans-1a were examined in acetonitrile, benzene, and
methanol using a 400W high-pressure mercury lamp (Riko
UVL-400 HA) with a Pyrex filter (see Figure 1). The
results are summarized in Table 1.
When trans-1a was irradiated in acetonitrile and moni-
tored by hplc, the amount of trans-1a was found to decrease
rapidly. After 10 minutes the reaction stopped and conver-
sion did not change anymore even after 60 minutes irradia-
tion (Entry 1, 2). The solution was evaporated and the
residue was chromatographed on silica gel to give 2-
quinolone 2 in excellent yield (Method A). Similarly, pho-
toreactions of trans-1a in benzene or methanol gave almost
It is known that cis-o-hydroxycinnnamic acid
(o-coumarinic acid) [2], its ester [3], and amide [4] undergo
lactonization to give coumarin. Cis-2-hydroxychalcone also
cyclizes to 2H-1-benzopyran hemiacetal [5]. Similarly, esters
[6] and amides [7] of trans-o-hydroxycinnnamic acid are
transformed to their cis-isomers on irradiation of ultraviolet
light and cyclize to give coumarin. Irradiation of trans-o-
hydroxychalcone affords 2H-1-benzopyran hemiacetal via
trans-cis isomerization followed by intramolecular cycliza-
tion [8]. Thus, when the distance between the hydroxyl group
and carbonyl group becomes close to each other in the cis-iso-
mers, intramolecular cyclization occurs. This method allows
for the syntheses of heterocyclic compounds. Irradiation is an
useful method to convert trans-isomers to cis-isomers [9].
We planned to synthesize six-membered ring hetero-
cyclic compounds 2, 3, 5, and 6 through photoinduced
trans-cis isomerization of trans-o-aminocinnnamoyl
derivatives trans-1 and trans-o-hydroxycinnnamoyl deriv-
atives trans-4.

62
T. Horaguchi, N. Hosokawa, K. Tanemura and T. Suzuki
Vol. 39
Figure 1
the same results though reaction time was longer in
methanol (Entry 3-6). To examine the reaction progress,
trans-1a was dissolved in deuterioacetonitrile and irradiated
1
in an nmr tube (external irradiation) monitored by H nmr
(Method B, see Figure 2). The results are shown in Table 2.
Figure 2
On irradiation of trans-1a the conversion increased
gradually with reaction time. However, 2-quinolone was
not detected even after 180 minutes irradiation. After
warming (60 °C, 15 minutes) the reaction solution in an
1
nmr tube, the H nmr spectrum showed disappearance of
cis-1a and formation of 2-quinoline. These results show
that irradiation of trans-1a induces only trans-cis equilib-
rium and the following operation (heating during evapora-
tion of the solution) gives intramolecular cyclization of
cis-1a to 2-quinolone.
To accelerate cyclization of cis-1a to 2-quinolone, pyri-
dine or acetic acid [7,2a] was added as a catalyst to the ace-
tonitrile solution and then irradiation was carried out
(Table 1, Entry 7-10). Addition of pyridine (1 ml) had no
Table 1
Photoreactions of ethyl trans-o-aminocinnamate trans-1a and trans-N,N-diethyl-o-aminocinnamamide trans-1b [a]
Entry
Starting
material [b]
R
Solvent
Irradiation time
(minutes)
Conversion
(%)
Product
yield [c] (%)
2
cis-1
1
2
3
4
5
6
7
8
trans-1a
trans-1a
trans-1a
trans-1a
trans-1a
trans-1a
trans-1a
trans-1a
trans-1a
trans-1a
trans-1b
trans-1b
trans-1b
OEt
OEt
OEt
OEt
OEt
OEt
OEt
OEt
OEt
OEt
CH CN
10
60
10
75
10
60
20
60
60
60
60
75
90
45
44
46
48
29
50
38
37
100
95
67
85
71
88
93
90
88
84
68
76
83
7
0
0
0
0
0
0
0
0
3
CH CN
3
C H
6
6
C H
6
6
CH OH
3
CH OH
3
CH CN/P y [d]
3
CH CN/P y [d]
3
9
CH CN/HOAc [e]
0
0
3
10
11
12
13
CH CN/HOAc [f]
79
0
0
3
NEt
NEt
NEt
CH CN
100 [g]
100 [g]
100 [g]
2
2
2
3
C H
6
6
CH OH
0
3

Jan-Feb 2002
Photocyclization Reactions. Part 8
63
Table 1 (continued)
[a] Method A for entry 1-13; [b] 2 Mmoles in 500 ml solvent; [c] Yield based on reacted starting material; [d] 1 Ml of pyridine in 500 ml of acetonitrile;
[e] 1 Ml of acetic acid in 500 ml of acetonitrile; [f] 0.1 Ml of acetic acid in 500 ml of acetonitrile; [g] Isolation of trans-1b and cis-1b was difficult by
1
chromatography and the cis-1b yield were determined from the H nmr spectrum of the mixture.
Table 2
When trans-1d was irradiated in acetonitrile, the con-
Photoreactions of ethyl trans-o-aminocinnamate trans-1a in a nmr tube [a]
version was complete within 25 minutes to give 2-
phenylquinoline in 88% yield (Entry 1). Similarly, on irra-
Entry Starting
material
R
Solvent Irradiation Conversion Product yield
diation of trans-1d in benzene and methanol, complete
conversion gave 3d in good yield (Entry 2-4). When trans-
o-aminobenzalacetone was irradiated in acetonitrile, ben-
zene, and methanol, 2-methylquinoline was produced
smoothly (Entry 5-8). Photoreactions of trans-1d and 1e in
methanol took a longer reaction time than that in acetoni-
trile or benzene. The results show that the cyclization of
cis-1d and cis-1e to quinolines 3d and 3e is fast and com-
pleted within minutes.
time
(minutes)
[b] (%)
[b] (%)
cis-1a
2
1
2
3
trans-1a OEt CD CN
trans-1a OEt CD CN
trans-1a OEt CD CN
20
60
180
13
28
38
0
0
0
100
100
100
3
3
3
[a] Method B for entry 1-3. [b] Conversion and product yield were deter-
mined from the H nmr spectrum of the mixture.
1
effect on cyclization of cis-1a to 2-quinolone (Entry 7-8).
In contrast, addition of acetic acid (0.1 ml) accelerated
cyclization of cis-1a to 2-quinolone (Entry 10). However,
excess of acetic acid (1 ml) induced decomposition (Entry
9). When trans-o-aminocinnamamide was irradiated in
acetonitrile, benzene, or methanol only a mixture of trans-
1b and cis-1b isomers was obtained (Entry 11-13). In this
case, cyclization of cis-1b to 2-quinolone did not occur
during the isolation procedure. Isolation of trans-1b and
cis-1b was difficult by chromatography and the ratio was
Photoreactions of trans-o-hydroxycinnamic acid and its
derivatives were examined (see Figure 4). The results are
summarized in Table 4.
1
determined by the H nmr spectrum of the mixture.
Photoreactions of trans-o-aminochalcone and trans-o-
aminobenzalacetone were examined (see Figure 3). The
results are summarized in Table 3.
Figure 4
When ethyl trans-o-hydroxycinnamate was irradiated in
acetonitrile for 15 minutes (69% conversion), coumarin 5
(94% based on percent conversion) was produced (Entry
1). Further irradiation (180 minutes) did not change the
conversion nor the product yield of 5 (Entry 2). The results
show that photoequilibrium between trans-4a and cis-4a
was attained during the irradiation, and cis-4a was con-
verted to coumarin during isolation procedure. Irradiation
of trans-4a in benzene and methanol afforded similar
Figure 3
Table 3
Photoreactions of trans-o-aminochalcone trans-1d and trans-o-aminobenzalacetone trans-1e [a]
Entry
Starting
material [b]
R
Solvent
Irradiation time
(minutes)
Conversion
(%)
Product
Yield
[c] (%)
1
2
3
4
5
6
7
8
trans-1d
trans-1d
trans-1d
trans-1d
trans-1e
trans-1e
trans-1e
trans-1e
Ph
Ph
Ph
CH CN
25
20
30
140
15
22
100
100
27
100
100
100
33
3d
3d
3d
3d
3e
3e
3e
3e
88
69
79
87
71
74
59
62
3
C H
6
6
CH OH
3
Ph
CH OH
3
Me
Me
Me
Me
CH CN
3
C H
6
6
CH OH
20
75
3
CH OH
100
3
[a] Method A for entry 1-8. [b] 2 Mmoles in 500 ml solvent. [c] Yield based on reacted starting material.

64
T. Horaguchi, N. Hosokawa, K. Tanemura and T. Suzuki
Vol. 39
Table 4
Photoreactions of ethyl trans-o-hydroxycinnamate trans-4a and trans-N,N-diethyl-o-hydroxycinnamamide trans-4b and trans-o-hydroxy-
cinnnamic acid trans-4c [a]
Entry
Starting
Material [b]
R
Solvent
Irradiation time
(minutes)
Conversion
(%)
Product
yield [c] (%)
5
cis-4
1
2
3
4
5
6
7
8
trans-4a
trans-4a
trans-4a
trans-4a
trans-4a
trans-4a
trans-4b
trans-4b
trans-4b
trans-4b
trans-4c
trans-4c
trans-4c
trans-4c
OEt
OEt
OEt
OEt
OEt
OEt
CH CN
15
180
16
60
15
60
60
180
15
180
20
69
74
68
81
65
68
67
62
97
96
71
72
69
69
94
93
95
95
92
94
68
40
47
0
0
0
0
0
3
CH CN
3
C H
6 6
C H
6 6
CH OH
3
CH OH
0
3
NEt
NEt
NEt
NEt
CH CN
25 [d]
53 [d]
44 [d]
41 [d]
5 [e]
7 [e]
0 [e]
0 [e]
2
2
2
2
3
CH CN
3
9
CH OH
3
10
11
12
13
14
CH OH
49
3
OH
OH
OH
OH
CH CN
95 [e]
93 [e]
100 [e]
100 [e]
3
CH CN
60
20
60
3
CH OH
3
CH OH
3
[a] Method A for entry 1-10, Method C for entry 11-14; [b] 2 Mmoles in 500 ml solvent; [c] Yield based on reacted starting material; [d] Isolation
1
of cis-4 and trans-4 was difficult by chromatography and the cis-4 yield and conversion were determined from the H nmr spectrum of the mix-
1
ture; [e] Yield was determined from the H nmr spectrum of the product mixture which was obtained by evaporation of the reaction solution.
results (Entry 3-6). Irradiation of trans-N,N-diethyl-o-
hydroxycinnamamide in acetonitrile gave coumarin 5 and
cis-4b (Entry 7-8). In this case, a considerable amount of
cis-4b was obtained, indicating slow cyclization reaction
between the hydroxyl group and the amide group.
However, when trans-4b was irradiated in methanol, con-
version was near 100% (Entry 9-10). Benzene was not
studied as a solvent because of poor solubility of trans-4b.
Irradiation of trans-o-hydroxycinnamic acid in acetonitrile
or methanol afforded mainly coumarin 5 (Entry 11-14). In
this case, conversion and yield were determined from the
Figure 5
of 2H-1-benzopyran hemiacetal 6d [8c]. Cyclization of
trans-o-hydroxychalcone to 2H-1-benzopyran hemiacetal
on irradiation is well-known [8]. Similarly, irradiation of
trans-o-hydroxybenzalacetone trans-4e gave 2H-1-ben-
1
H nmr spectrum of the product mixture which was
obtained after evaporation of the reaction solution
(Method C). Method C was used to avoid changing the
product ratio of the photoreaction by chromatography.
Finally, photoreactions of trans-o-hydroxychalcone and
1
zopyran hemiacetal 6e from the H nmr spectrum.
General mechanisms of photocyclization reactions on
trans-o-aminocinnamoyl compounds trans-1 and trans-o-
hydroxycinnamoyl compounds trans-4 are shown in
Scheme 3.
Irradiation of trans-1 induces an equilibrium mixture of
trans-1 and cis-1. In the case of R=OEt, cyclization of cis-
1 occurrs thermally during concentration to give
2-quinolone 2 through 12. However, in the case of
1
trans-o-hydroxybenzalacetone were examined using H
nmr (see Figure 5). The results are summarized in Table 5.
Compound trans-4d dissolved in deuterioacetonitrile in
a nmr tube was irradiated by high-pressure mercury lamp
(external irradiation). After 90 minutes irradiation, conver-
1
sion was 100%. The H nmr spectrum showed production
Table 5
Photoreactions of trans-o-hydroxychalcone trans-4d and trans-o-hydroxybenzalacetone trans-4e in a nmr tube [a]
Entry
Starting
Material
R
Solvent
Irradiation
time
Conversion
Product
[b] (%)
Yield
[b] (%)
(minutes)
1
2
trans-4d
trans-4e
Ph
Me
CD CN
CD CN
3
90
90
100
100
6d
6e
100
100
3
1
[a] Method B for entry 1-2. [b] Conversion and product yield were determined from the H nmr specrum of the mixture.

Jan-Feb 2002
Photocyclization Reactions. Part 8
65
Trans-o-hydroxycinnamamide [10], trans-o-hydroxychalcone
[11], and trans-o-hydroxybenzalacetone [12] were prepared
according to literature.
Ethyl trans-o-Aminocinnamate.
Ethyl trans-o-nitrocinnamate (1.00 g, 4.52 mmol) [13] and
hydrazine monohaydrate (0.44 ml, 9.06 mmol) were dissolved in
ethanol (100 ml). After 7% palladium-charcoal (0.10 g) was
added, the solution was refluxed for 30 minutes. After removal of
the palladium-charcoal by filtration, the ethanol was evaporated.
The residue was extracted with ether. The extract was washed
with water, dried, and evaporated. The residue was chro-
matographed and eluted with benzene-ether (9:1) to give trans-
1a (0.66 g, 76%) as pale yellow crystals, mp 74-75 °C from ben-
zene-hexane; ir (potassium bromide): 3472 (NH ), 3380 (NH ),
2
2
-1
1
1690 cm (CO CH CH ); H nmr (deuteriochloroform): δ 1.33
2
2
3
(t, J=7.0 Hz, 3H, CH CH ), 3.46 (broad s, 2H, NH ), 4.26 (q,
2
3
2
J=7.0 Hz, 2H, CH CH ), 6.36 (d, J=16.0 Hz, 1H, CH=CHCO),
2
3
6.73 (d, J=8.0 Hz, 1H, Ar-H), 6.80 (dd, J=8.0 and 8.0 Hz, 1H, Ar-
H), 7.17 (dd, J=8.0 and 8.0 Hz, Ar-H), 7.39 (d, J=8.0 Hz, 1H, Ar-
13
H), 7.83 (d, J=16.0 Hz, 1H, CH=CHO); C nmr (deuteriochloro-
form): δ 14.2 (q), 60.3 (t), 116.6 (d), 117.9 (d), 118.7 (d), 119.7
(s), 127.9 (d), 131.1 (d), 140.0 (d), 145.6 (s), 167.2 (s).
Anal. Calcd. for C H NO : C, 69.09, H, 6.85, N, 7.33.
11 13
2
Found: C, 69.24; H, 6.83; N, 7.20.
trans-N,N-Diethyl-o-nitrocinnamamide.
A mixture of trans-o-nitrocinnamic acid (5.00 g, 25.9 mmol),
thionyl chloride (20 ml), and benzene (10 ml) was refluxed for
2.5 hours. The benzene and unreacted thionyl chloride were
removed by distillation under reduced pressure. The residue was
dissolved in diethylamine (40 ml) and allowed to stand for 20
hours at room temperature. The solution was extracted with
ether. The extract was washed, dried, and evaporated. The
residue was chromatographed and eluted with benzene-ethyl
acetate (1:1) to give trans-9 (4.89 g, 76%) as pale yellow crystals,
mp 56-57 °C from hexane-benzene-ether; ir (potassium bro-
R=NEt , cyclization does not occur because of low reac-
2
tivity of the amide group. In contrast, when R is Ph or Me,
cyclization of cis-1 occurrs spontaneously during irradia-
tion to give quinolines 3, consistent with the reactivity of
amines with ketones.
Similarly, irradiation of trans-o-hydroxycinnamoyl
derivatives produces trans-cis equilibrium between trans-
-1
1
mide): 1662 cm (CON(CH CH ) ); H nmr (deuteriochloro-
2
3 2
form): δ 1.21 (broad s, 3H, CH CH ), 1.26 (broad s, 3H,
2
3
4 and cis-4. When R is OEt, NEt , or OH, elimination of
2
CH CH ), 3.49 (broad s, 4H, CH CH and CH CH ), 6.71 (d,
2
3
2
3
2
3
ethanol, diethylamine or water from 6 affords coumarin 5.
In the case of R=Ph and Me, 2H-1-benzopyran hemiacetals
6 are produced because further reaction is not possible.
In conclusion, photoinduced trans-cis isomerization fol-
lowed by intramolecular cyclization is a useful synthetic
method for six-membered heterocyclic compounds which
contain a nitrogen or oxygen atom.
J=15.0 Hz, 1H, CH=CHCO), 7.51 (dd, J=7.5 and 7.5 Hz, 1H, Ar-
H), 7.61-7.64 (m, 2H, Ar-H ), 8.00 (d, J=15.0 Hz, 1H,
2
13
CH=CHCO), 8.01 (d, J=7.5 Hz, 1H, Ar-H); C nmr (deuteri-
ochloroform): δ 13.1 (q), 15.0 (q), 41.0 (t), 42.4 (t), 123.5 (d),
124.7 (d), 129.3 (d), 129.5 (d), 131.8 (s), 133.2 (d), 137.2 (d),
148.3 (s), 164.8 (s).
Anal. Calcd. for C H N O : C, 62.89; H, 6.50; N, 11.28.
13 16
2 3
Found: C, 62.81; H, 6.65; N, 11.35.
trans-N,N-Diethyl-o-aminocinnamamide.
EXPERIMENTAL
trans-N,N-Diethyl-o-nitrocinnamamide (1.00 g, 4.03 mmol)
and hydrazine monohydrate (0.45 ml, 9.27 mmol) were dissolved
in ethanol (30 ml). After 7% palladium-charcoal (0.05 g) was
added, the solution was refluxed for 1 hour. During reflux,
hydrazine monohydrate (0.35 ml, 7.21 mmol) and 7% palladium-
charcoal (0.05 g) were added to complete the reaction. After
removal of the palladium-charcoal by filtration, the ethanol was
evaporated. The residue was extracted with ether. The extract
was washed, dried, and evaporated. The residue was chro-
matographed and eluted with benzene-acetone (1:1) to give
trans-1b (0.49 g, 55%) as pale yellow crystals, mp 64-66 °C from
The melting points are uncorrected. Column chromatography
was performed on silica gel (Wakogel C-200). Unless otherwise
stated, anhydrous sodium sulfate was employed as the drying
agent. Ether refers to diethyl ether. The ir spectra were deter-
1
mined on a Hitachi Model 270-30 IR spectrometer. The H and
13
C nmr spectra were determined at 500 MHz and 125 MHz on a
Varian Unity plus-500W NMR spectrometer, using tetramethylsi-
lane as the internal standard.
Synthesis of trans-4b, trans-4d, and trans-4e.

66
T. Horaguchi, N. Hosokawa, K. Tanemura and T. Suzuki
Vol. 39
ether-hexane; ir (potassium bromide): 3320 (NH ), 3216 (NH ),
dried, and evaporated. The residue was chromatographed and
eluted with benzene-ether (9:1) to give trans-4a (4.68 g, 80 %)
as colorless crystals, mp 86-87 °C from ether-hexane; ir (potas-
2
2
-1
1
1642 cm (CON(CH CH ) ); H nmr (deuteriochloroform): δ
2
3 2
1.19 (t, J=7.0 Hz, 3H, CON(CH CH ) ), 1.26 (t, J=7.0 Hz, 3H,
2
3 2
-1
1
CON(CH CH ) ), 3.1-4.3 (broad s, 2H, NH ), 3.46-3.50 (m, 4H,
sium bromide): 3420 (OH), 1685 cm (CO ); H nmr (deuteri-
2
3 2
2
2
CON(CH CH ) and CON(CH CH ) ), 6.72-6.78 (m, 3H, Ar-H
ochloroform): δ 1.35 (t, J=7.0 Hz, 3H, CH CH ), 4.29 (q, J=7.0
2 3
2
3 2
2
3 2
2
and CH=CHCO), 7.15 (dd, J=7.5 and 7.5 Hz, 1H, Ar-H), 7.37 (d,
Hz, 2H, CH CH ), 6.63 (d, J=16.5 Hz, 1H, CH=CHO), 6.73 (s,
1H, OH), 6.85 (d, J=7.5 Hz, 1H, Ar-H), 6.91 (dd, J=7.5 and 7.5
2 3
13
J=7.5 Hz, 1H, Ar-H), 7.85 (d, J=15.5 Hz, 1H, CH=CHCON);
C
nmr (deuteriochloroform): δ 13.6 (q), 15.5 (q), 41.3 (t), 42.5 (t),
117.0 (d), 117.9 (d), 118.2 (d), 121.0 (s), 128.1 (d), 130.9 (d),
138.1 (d), 148.0 (s), 165.9 (s).
Hz, 1H, Ar-H), 7.23 (dd, J=7.5 and 7.5 Hz, 1H, Ar-H), 7.47 (d,
13
J=7.5 Hz, 1H, Ar-H), 8.04 (d, J=16.5 Hz, 1H, CH=CHCO);
C
nmr (deuteriochloroform): δ 14.2 (q), 60.9 (t), 116.4 (d), 117.8
(d), 120.3 (d), 121.5 (s), 129.1 (d), 131.5 (d), 141.3 (d), 155.9
(s), 169.1 (s).
Anal. Calcd. for C H N O: C, 71.53; H, 8.31; N, 12.83.
13 18
2
Found: C, 71.48; H, 8.30; N, 12.71.
Anal. Calcd. for C H O : C, 68.74; H, 6.29. Found: C,
68.56; H, 6.40.
11 12
3
trans-o-Aminochalcone.
trans-o-Nitrochalcone (2.00 g, 7.90 mmol) [14] in ethanol
(100 ml) was catalytically hydrogenated at 0 °C in the presence
of 7% palladium-charcoal (1.00 g) until 600 ml (3 equivalents) of
hydrogen was absorbed. During the reduction the reaction flask
was covered with aluminum foil to protect from the side reaction
by light. After removal of the catalyst by filtration, the ethanol
was evaporated. The residue was chromatographed and eluted
with benzene-ether (8:2) to give trans-1d (0.95 g, 54%) as yellow
crystals, mp 114-116 °C (lit. [14] mp 115 °C) from ethanol-water;
General Procedure for Photocyclization Reactions of trans-1 and
trans-4.
Method A.
In acetonitrile, benzene, or methanol solvent (500 ml), 2.00
mmol of the starting materials 1, or 4 were dissolved. In some
case, pyridine or acetic acid was added. The solution was deoxy-
genated by bubbling nitrogen gas for 1 hour and then irradiated
with high-pressure mercury lamp (Riko UVL-400HA, Pyrex fil-
ter) while monitoring by high performance liquid chromatogra-
phy (hplc). The irradiation was stopped when reaction did not
proceed. After irradiation, the solvent was evaporated under
reduced pressure below 40 °C. The residue was chromatographed
and eluted with solvent to give products.
-1
1
ir (potassium bromide) : 3232 (NH ), 1658 cm (C=O); H nmr
2
(deuteriochloroform): δ 4.08 (broad s, 2H, NH ), 6.73 (d, J=7.5
2
Hz, 1H, Ar-H), 6.80 (dd, J=7.5 and 7.5 Hz, 1H, Ar-H), 7.21 (dd,
J=7.5 and 7.5 Hz, 1H, Ar-H), 7.48-7.54 (m, 4H, Ar-H and
3
CH=CHCO), 7.58 (dd, J=7.5 and 7.5 Hz, 1H, Ar-H), 8.00 (d,
13
J=15.5 Hz, 1H, CH=CHCO), 8.03 (d, J=7.5 Hz, 2H, Ar-H );
C
2
Method B.
nmr (deuteriochloroform): δ 116.8 (d), 118.8 (d), 120.1 (s), 121.6
(d), 128.0 (d), 128.4 (d), 128.5 (d), 131.6 (d), 132.7 (d), 138.2 (s),
140.1 (d), 146.3 (s), 190.2 (s).
Starting materials trans-1a, trans-4d, or trans-4e (0.05 mmol)
was dissolved in deuterioacetonitrile (2 ml) in an nmr tube. The
solution was deoxygenated by bubbling nitrogen gas for 1 hour
and then irradiated (external irradiation) with high-pressure mer-
cury lamp (Riko UVL-400HA, Pyrex filter) while monitoring
Anal. Calcd. for C H NO: C, 80.69; H, 5.87; N, 6.27. Found:
15 13
C, 80.74; H, 6.09; N, 6.36.
trans-o-Aminobenzalacetone.
1
with H nmr spectra. Conversion and product yield were deter-
1
trans-o-Nitrobenzalacetone (1.00 g, 5.23 mmol) [15] in
ethanol (100 ml) was catalytically hydrogenated at 0 °C in the
presence of 7% palladium-charcoal (0.50 g) until 450 ml (3
equivalents) of hydrogen was absorbed. During the reduction the
reaction flask was covered with aluminum foil to protect from the
side reaction by light. After removal of the catalyst by filtration,
the ethanol was evaporated. The residue was chromatographed
and eluted with benzene-ether (8:2) to give trans-1e (0.47 g,
55%) as yellow crystals, mp 48-50 °C from ether-hexane; ir
mined from the H nmr spectra.
Method C.
In acetonitrile, benzene, or methanol solvent (500 ml), 2.00
mmol of the starting materials 1 or 4 were dissolved. The solution
was deoxygenated by bubbling nitrogen gas for 1 hour and then
irradiated with high-pressure mercury lamp (Riko UVL-400HA,
Pyrex filter) while monitoring by high performance liquid chro-
matography (hplc). The irradiation was stopped when the reac-
tion did not proceed. After irradiation the solvent was evaporated
under reduced pressure below 40 °C. The residue was dissolved
in deuteriochloroform and the products and product yield were
-1
(potassium bromide): 3452 (NH ), 3352 (NH ), 1668 cm
2
2
1
(C=O); ); H nmr (deuteriochloroform): δ 2.37 (s, 3H, CH ), 3.97
3
(broad s, 2H, NH ), 6.68 (d, J=16.0 Hz, 1H, CH=CHCO), 6.71
2
1
(d, J=7.5 Hz, 1H, Ar-H), 6.79 (dd, J=7.5 and 7.5 Hz, 1H, Ar-H),
7.19 (dd, 7.5 and 7.5 Hz, 1H, Ar-H), 7.40 (d, J=7.5 Hz, 1H, Ar-
determined from the H nmr spectra. This method was used to
prevent change of the product ratio by chromatography.
13
H), 7.68 (d, J=16.0 Hz, 1H, CH=CHCO); C nmr (deuteriochlo-
2-Quinolone.
roform): δ 28.0 (q), 116.8 (d), 119.0 (d), 119.8 (s), 126.7 (d),
128.1 (d), 131.5 (d), 138.6 (d), 145.9 (s), 198.2 (s).
1
13
H and C nmr spectra of 2 were identical with those of a
Anal. Calcd. for C H NO: C, 74.51; H, 6.88; N, 8.69. Found:
C, 74.62; H, 6.81; N, 8.76.
commercially available sample. Recrystallization gave colorless
crystals from benzene, mp 198-200 °C (Commercially available
sample, mp 198-201 °C); ir (potassium bromide): 3000 (broad,
10 11
Ethyl trans-o-Hydroxycinnamate.
-1
1
NH), 1656 cm (CONH); H nmr (deuteriochloroform): δ 6.73
(d, J=10.0 Hz, 1H, CH=CHCO), 7.23 (dd, J=8.0 and 8.0 Hz, 1H,
Ar-H), 7.46 (d, J=8.0 Hz, 1H, Ar-H), 7.52 (dd, J=8.0 and 8.0 Hz,
1H, Ar-H), 7.57 (d, J=8.0 Hz, 1H, Ar-H), 7.82 (d, J=10.0 Hz, 1H,
A mixture of trans-o-hydroxycinnamic acid (5.00 g, 30.5
mmol), ethanol (50 ml), and concentrated sulfuric acid (1.0 ml)
was refluxed for 3 hours. The solution was poured into water
(200 ml) and extracted with ether. The extract was washed,
13
CH=CHCO), 12.55 (broad s, 1H, NH); C nmr (deuteriochloro-

Jan-Feb 2002
Photocyclization Reactions. Part 8
67
form): δ 116.3 (d), 119.9 (s), 121.3 (d), 122.7 (d), 127.7 (d), 130.7
(d), 138.5 (s), 141.1 (d), 164.8 (s).
J=10.0 Hz, 1H, CH=CH-C-OH), 6.86 (d, J=8.0 Hz, 1H, Ar-H),
6.94 (dd, J=8.0 and 8.0 Hz, 1H, Ar-H), 7.18 (d, J=8.0 Hz, 1H, Ar-
H), 7.20 (dd, J=8.0 and 8.0 Hz, 1H, Ar-H).
2-Phenylquinoline.
1
13
Acknowledgement.
H and C nmr spectra of 3d were identical with those of a
commercially available sample. Recrystallization gave colorless
crystals from ether, mp 84-85 °C (Commercially available sam-
ple, mp 84-85 °C); H nmr (deuteriochloroform): δ 7.49 (dd,
We thank Mr. Yoshiaki Matsuda for the elemental analyses.
1
REFERENCES AND NOTES
J=8.5 and 8.5 Hz, 1H, Ar-H), 7.54-7.57 (m, 3H, Ar-H ), 7.75 (dd,
3
J=8.5 and 8.5 Hz, 1H, Ar-H), 7.86 (d, J=8.5 Hz, 1H, Ar-H), 7.90
[1] Part 7, E. M. Sharshira and T. Horaguchi, J. Heterocyclic
Chem., 34, 1837 (1997).
[2a] R. Hershfield and G. L. Schmir, J. Am. Chem. Soc., 95, 7359
(1973); [b] R. Hershfield and G. L. Schmir, J. Am. Chem. Soc., 95, 8032
(1973).
(d, J=8.5 Hz, 1H, Ar-H), 8.18-8.21 (m, 3H, Ar-H ), 8.25 (d, J=8.5
3
13
Hz, 1H, Ar-H); C nmr (deuteriochloroform): δ 119.0 (d), 126.3
(d), 127.2 (s), 127.4 (d), 127.6 (d), 128.8 (d), 129.3 (d), 129.7 (d),
136.8 (d), 139.6 (s), 148.2 (s), 157.3 (s).
[3] R. A. McClelland, R. Somani, and A. J. Kresge, Can. J.
Chem., 57, 2260 (1979).
[4] B. Bang, H. Zhang, and W. Wang, Bioorg. Med. Chem. Lett.,
6, 945 (1996).
2-Methylquinoline.
1
13
H and C nmr spectra of 3e were identical with those of a
1
commercially available sample. Colorless oil; H nmr (deuteri-
ochloroform): δ 2.75 (s, 3H, CH ), 7.27 (d, J=6.0 Hz, 1H, Ar-H),
[5a] R. A. McClelland and S. Gedge, J. Am. Chem. Soc., 102, 5838
(1980); [b] D. B. Devine and R. A. McClelland, J. Org. Chem., 50, 5656
(1985); [c] F. Pina, M. J. Melo, M. Maestri, R. Ballardini, and V.
Balzami, J. Am. Chem. Soc., 119, 5556 (1997): [d] F. Pina, M. Maestri,
and V. Balzami, J. Chem. Soc., Chem. Commun., 107 (1999).
[6a] R. S. Mali, S. N. Yeola, and B. K. Kulkarmi, Indian J. Chem.,
22B, 352 (1983); [b] A. D. Turner, S. V. Pizzo, G. W. Rozakis, and N. A.
Porter, J. Am. Chem. Soc., 109, 1274 (1987); [c] A. D. Turner, S. V. Pizzo,
G. Rozakis, and N. A. Porter, J. Am. Chem. Soc., 110, 244 (1988); [d] N. A.
Porter and J. D. Bruhnke, Photochem. Photobiol., 51, 37 (1990); [e] P. M.
Koenigs, B. C. Faust, and N. A. Porter, J. Am. Chem. Soc., 115, 9371 (1993);
[f] D. N. Nicolaides, K. C. Fylaktakidou, K. E. Litinas, and S. G.
Adamopoulos, J. Heterocyclic Chem., 35, 91 (1998).
[7] B. Wang and A. Zheng, Chem. Pharm. Bull., 45, 715 (1997).
[8a] D. Dewar and R. G. Sutherland, J. Chem. Soc., Chem. Commun.,
272 (1970); [b] R. Matsushima and M. Suzuki, Bull. Chem. Soc. Jpn., 65,
39 (1992); [c] H. Horiuchi, A. Yokawa, T. Okutsu, and H. Hiratsuka, Bull.
Chem. Soc. Jpn., 72, 2429 (1999); [d] H. Horiuchi, H. Shirase, T. Okutsu, R.
Matsushima, and H. Hiratsuka, Chemistry Lett., 96 (2000).
[9] V. R. Gopal, A. M. Reddy, and V. J. Rao, J. Org. Chem., 60,
7966 (1995).
[10] D. Papa, E. Schwenk, F. Villani, and E. Klingsberg, J. Am.
Chem. Soc., 72, 3885 (1950).
[11] H. Bablich and S. V. Kostanecki, Ber. Dtsch. Chem. Ges., 29,
233 (1896); [b] C. Harries and G. Busse, Ber. Dtsch. Chem. Ges., 29, 375
(1896).
[12a] C. D. Harries, Ber. Dtsch. Chem. Ges., 24, 3180 (1891); [b]
M. Winter, Helv. Chim. Acta, 44, 2110 (1961).
[13] D. Sicker, A. Rabe, A. Zakrzewski, and G. Mann, J. Prak.
Chem., 329, 1063 (1987).
3
7.48 (dd, J=6.0 and 6.0 Hz, 1H, Ar-H), 7.68 (dd, J=6.0 and 6.0
Hz, 1H, Ar-H), 7.76 (d, J=6.0 Hz, 1H, Ar-H), 8.03 (d, J=6.0 Hz,
13
1H, Ar-H), 8.03 (d, J=6.0 Hz, 1H, Ar-H); C nmr (deuteriochlo-
roform): δ 25.3 (q), 122.0 (d), 125.7 (d), 126.5 (s), 127.5 (d),
128.5 (d), 129.5 (d), 136.3 (d), 147.8 (s), 158.9 (s).
Coumarin.
1
13
H and C nmr spectra of 5 were identical with those of a
commercially available sample. Recrystallization gave colorless
crystals from ethanol, mp 69-72 °C (Comercially available sam-
-1
1
ple, mp 68-72 °C), ir (potassium bromide): 1706 cm (C=O); H
nmr (deuteriochloroform): δ 6.44 (d, J=9.5 Hz, 1H, CH=CHCO),
7.30 (dd, J=7.5 and 7.5 Hz, 1H, Ar-H), 7.35 (d, J=7.5 Hz, 1H, Ar-
H), 7.50 (d, J=7.5 Hz, 1H, Ar-H), 7.53 (dd, J=7.5 and 7.5 Hz, 1H,
13
Ar-H), 7.72 (d, J=9.5 Hz, 1H, CH=CHCO); C nmr (deuteri-
ochloroform): δ 116.7 (d), 116.9 (d), 118.8 (s), 124.4 (d), 127.9
(d), 131.8 (d), 143.4 (d), 154.1 (s), 160.8 (s).
2-Phenyl-2H-1-benzopyran-2-ol.
1
The H nmr spectrum of 6d was identical with that of literature
1
[8c]. H nmr (deuterioacetonitrile): δ 5.23 (broad s, 1H, OH),
5.87 (d, J=10.5 Hz, 1H, CH=CHC-OH), 6.72 (d, J=10.5 Hz, 1H,
CH=CH-OH), 6.96 (d, J=8.0 Hz, 1H, Ar-H), 7.00 (dd, J=8.0 and
8.0 Hz, 1H, Ar-H), 7.24-7.28 (m, 2H, Ar-H ), 7.35-7.60 (m, 3H,
2
Ar-H ), 7.61 (d, J=8.0 Hz, 2H, Ar-H ).
3
2
2-Methyl-2H-1-benzopyran-2-ol.
[14] W. Davey and J. R. Gwilt, J. Chem. Soc., 1008 (1957).
[15] J. H. Burckhalter and S. H. Johnson, Jr., J. Am. Chem. Soc.,
73, 4835 (1951).
1
H nmr (deuterioacetonitrile): δ 1.64 (s, 3H, CH ), 4.52 (broad
3
s, 1H, OH), 5.86 (d, J=10.0 Hz, 1H, CH=CH-C-OH), 6.62 (d,