Metal salt mediated radical reactions of 2-substituted-1, 4-naphthoquinones

Article abstract of DOI:10.1002/ejoc.201000272

The silver(II)- and manganese(III)-mediated radical reactions of 2-substituted-l, 4-naphthoquinones are described. Acyl radicals generated by the oxidative decarboxylation of αketo acids with silver(I) nitrate and persulfate undergo efficient radical addi

Full text of DOI:10.1002/ejoc.201000272

FULL PAPER
DOI: 10.1002/ejoc.201000272
Metal Salt Mediated Radical Reactions of 2-Substituted-1,4-Naphthoquinones
Zhen-Yu Lin,[a] Yu-Ling Chen,[a] Chih-Shone Lee,[b] and Che-Ping Chuang*[a]
Keywords: Radical reactions / Silver / Manganese / Acylation / Quinones
The silver(II)- and manganese(III)-mediated radical reactions
of 2-substituted-1,4-naphthoquinones are described. Acyl
radicals generated by the oxidative decarboxylation of α-
keto acids with silver(I) nitrate and persulfate undergo ef-
ficient radical addition to the C=C bond of 2-(1-hy-
for the synthesis of naphtho[2,3-c]furan-4,9-diones and
benzo[f]isoindole-4,9-diones. In the presence of O2, manga-
nese(III) acetate oxidation of β-keto esters also generates acyl
radicals, which then undergo radical addition to 2-(1-amido-
alkyl)-1,4-naphthoquinones, and subsequently, benzo[f]iso-
droxyalkyl)-1,4-naphthoquinones and 2-(1-amidoalkyl)-1,4- indole-4,9-diones are produced.
naphthoquinones. This reaction provides an effective method
Diels–Alder reactions and are widely used in the prepara-
Introduction
tion of complex molecules.[12] The benzo[f]isoindole-4,9-di-
one skeleton has also attracted considerable attention in the
literature and several pathways have been developed for its
synthesis.[13] Acyl radicals were produced by the oxidative
decarboxylation of α-keto acids with silver(I) ion and per-
sulfate, and they were then utilized for the acylation of 1,4-
quinones.[14] As part of our study on the development of
new routes to heterocyclic systems proceeding through
metal salt mediated radical reactions,[5,11] we now report a
new method for the synthesis of naphtho[c]furan-4,9-dione
and benzo[f]isoindole-4,9-dione derivatives from 2-substi-
tuted-1,4-naphthoquinones.
There has been a growing interest in the application of
free radical reactions and many new methods proceeding
through radical reactions designed for organic synthesis
have been developed.[1,2] The addition of carbon-centered
radicals produced by metal salt oxidation of 1,3-dicarbonyl
compounds to alkenes has received considerable attention
in organic synthesis for the construction of carbon–carbon
bonds. Among these, manganese(III) acetate and cerium-
(IV) ammonium nitrate have been used most efficiently.[2–5]
Carbon radicals can be produced effectively by silver ion
catalyzed oxidative decarboxylation of carboxylic acids
with persulfate,[6] and they undergo homolytic alkylation
with heteroaromatics[7] and 1,4-quinones.[8] Compounds
containing the quinone group are an important class of bio-
logically active molecules that are widespread in nature.[9,10]
Previously, we found that the manganese(III) acetate me-
diated oxidative free radical reaction of 2-benzoyl-(3-
ethoxycarbonylmethyl)-1,4-naphthoquinones, in addition to
the expected 6-hydroxy-naphthacene-5,12-diones, produced
the novel naphtho[2,3-c]furan-4,9-diones as the major prod-
ucts.[5g] These naphtho[2,3-c]furan-4,9-diones can also be
generated directly from the intermolecular oxidative free
radical reaction of 2-benzoyl-1,4-naphthoquinones with
1,3-dicarbonyl compounds.[5h] Naphtho[2,3-c]furan-4,9-di-
ones form the largest subset of natural products containing
a c-fused furan ring.[10] Methods for their synthesis have
been reviewed.[9c] The corresponding isofuran derivatives
have served as quinodimethane synthetic analogues in
Results and Discussion
We began our studies of the silver(I)-catalyzed reaction
with 2-(1-hydroxyalkyl)-1,4-naphthoquinones 1 and α-keto
acids 2 (Scheme 1). When 2-(1-hydroxybenzyl)-1,4-naph-
thoquinone (1a, R1 = Ph) was treated with 2-oxopropionic
acid (2a, R2 = Me), silver(I) nitrate and potassium persul-
fate in acetonitrile/H2O at 70 °C, naphtho[c]furan-4,9-dione
3a was obtained in 57% yield (Table 1, Entry 1). The struc-
1
ture of 3a is clearly assigned by H NMR and 13C NMR
spectroscopy. Although the mechanistic details of this reac-
tion are unclear, 3a may be formed by the reaction route
presented in Scheme 2. Silver(II)-mediated decarboxylation
of 6a produces acyl radical 4a. Intermolecular addition of
acyl radical intermediate 4a to the quinone ring followed
by oxidation produces 5a. Acylation product 5a is then con-
verted into 3a by an intramolecular condensation reaction.
The generalities of this reaction were examined with other
α-keto acids 2, and the results are summarized in Table 1
(Entries 1–5). In all cases, 1a was converted into the corre-
sponding isofuran products 3 effectively. We also applied
[a] Department of Chemistry, National Cheng Kung University,
Tainan, Taiwan 70101, Republic of China
Fax: +886-6-2740552;
E-mail: cpchuang@mail.ncku.edu.tw
[b] Department of Chemistry, National Sun Yat-Sen University,
Kaohsiung, Taiwan 80424, Republic of China
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201000272.
–2
AgI/S2O8 reaction conditions to 2-(1-hydroxyethyl)-1,4-
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Metal Salt Mediated Radical Reactions of 2-Substituted-1,4-Naphthoquinones
naphthoquinone (1b, R1 = Me). The reaction worked well isoindole products 8 effectively. The reaction yield de-
and isofurans 3f–h were formed in 74–56% yield (Table 1, creased as the size of the substituent (R2) increased. This
Entries 6–8). This reaction provides an efficient method for can be attributed to the steric effect exerted by the R2
the formation of naphtho[2,3-c]furan-4,9-diones.
group – the condensation rate of 9 is retarded by the larger
R2 group. This reaction provides a straightforward method
for the synthesis of benzo[f]isoindole-4,9-diones 8. Other N-
protecting groups were also employed to examine the scope
of this reaction. As shown in Table 2 (Entries 6–13), iso-
indoles 8 were obtained in moderate to good yields. With
R3 = CO2Et, isoindoles 8 were obtained with best results.
This is presumably due to the higher nucleophilicity of the
ethoxycarbonylamino group.
Scheme 1. Reaction between 2-(1-hydroxyalkyl)-1,4-naphthoquin-
ones 1 and α-keto acids 2.
Table 1. Reaction between 2-(1-hydroxyalkyl)-1,4-naphthoquinones
1 and α-keto acids 2.
Entry
Quinone
Acid
Product (% yield)
1
2
3
4
5
6
7
8
1a: R1 = Ph
1a: R1 = Ph
1a: R1 = Ph
1a: R1 = Ph
1a: R1 = Ph
1b: R1 = Me
1b: R1 = Me
1b: R1 = Me
2a: R2 = Me
2b: R2 = Et
2c: R2 = Pr
2d: R2 = iBu
2e: R2 = Ph
2a: R2 = Me
2b: R2 = Et
2e: R2 = Ph
3a (57)
3b (54)
3c (54)
3d (54)
3e (75)
3f (61)
3g (56)
3a (74)
Scheme 3. Reaction between 2-(1-amidoalkyl)-1,4-naphthoquin-
ones 7 and α-keto acids 2.
Table 2. Reaction between 2-(1-amidoalkyl)-1,4-naphthoquinones 7
and α-keto acids 2.
Entry Quinone
Acid
Product
(% yield)
1
2
3
4
5
6
7
8
7a: R1 = Ph, R3 = Ac
2a: R2 = Me
2b: R2 = Et
2c: R2 = Pr
2d: R2 = iBu
2e: R2 = Ph
2a: R2 = Me
2b: R2 = Et
2c: R2 = Pr
2a: R2 = Me
2b: R2 = Et
2c: R2 = Pr
2d: R2 = iBu
2e: R2 = Ph
8a (64)
8b (59)
8c (43)
8d (30)
8e (13)
8f (73)
8g (65)
8h (47)
8i (84)
8j (84)
8k (60)
8l (55)
8m (33)
7a: R1 = Ph, R3 = Ac
7a: R1 = Ph, R3 = Ac
7a: R1 = Ph, R3 = Ac
7a: R1 = Ph, R3 = Ac
7b: R1 = Ph, R3 = Bz
7b: R1 = Ph, R3 = Bz
7b: R1 = Ph, R3 = Bz
7c: R1 = Ph, R3 = CO2Et
7c: R1 = Ph, R3 = CO2Et
7c: R1 = Ph, R3 = CO2Et
7c: R1 = Ph, R3 = CO2Et
7c: R1 = Ph, R3 = CO2Et
9
10
11
12
13
Scheme 2. Probable mechanism for the reaction between 1 and 2.
In view of the good results on the formation of naph-
tho[2,3-c]furan-4,9-diones 3, we reasoned that it might be
possible to produce benzo[f]isoindole-4,9-diones 8 through
Previously, we found that oxidative free radical reactions
the condensation reaction of 9, which was formed by the of 2-alkylamino-1,4-naphthoquinones with β-keto esters
acyl radical addition of 2-(1-amidoalkyl)-1,4-naphtho- produced benzo[f]indole-4,9-diones and benzo[f]indole-
quinones 7. We next investigated the silver(II)-mediated re- 2,4,9-triones.[5a,5f] In acidic solvent, the condensation prod-
action between 2-(1-amidoalkyl)-1,4-naphthoquinones 11 ucts Ϫ benzo[f]indole-4,9-diones Ϫ are the major product.
and α-keto acids 2 for the synthesis of benzo[f]isoindole- Naturally occurring 2-azaanthraquinones are of special
4,9-diones 8 (Scheme 3). Treatment of 2-[N-acetyl-(1-ami- interest due to their important physiological proper-
nobenzyl)]-1,4-naphthoquinone (7a, R1 = Ph, R3 = Ac) ties.[9b,10b,15] We believe that radical reaction between 2-(1-
with 2-oxopropionic acid (2a, R2 = Me), silver(I) nitrate, amidoalkyl)-1,4-naphthoquinones 7 and β-keto esters 10
and potassium persulfate in acetonitrile/H2O at 70 °C gen- would generate 2-azaanthraquinones 11 through intermo-
erated benzo[f]isoindole-4,9-dione 8a in 64% yield (Table 2, lecular addition of radical 12 to the quinone ring followed
1
Entry 1). The structure of 8a was revealed by H and 13C by an intramolecular condensation reaction. We have con-
NMR spectroscopy. The results of the reaction between [N- tinued to examine the manganese(III)-mediated oxidative
acetyl-(1-aminobenzyl)]-1,4-naphthoquinone (7a) and other free radical reaction between 2-(1-amidoalkyl)-1,4-naphtho-
α-keto acids 2 are also summarized in Table 2 (Entries 2– quinones 7 and β-keto esters 10 (Scheme 4). When [N-
5). In all cases, 7a was converted into the corresponding benzoyl-(1-aminobenzyl)-1,4-naphthoquinone] (7b, R1
=
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3877

Z.-Y. Lin, Y.-L. Chen, C.-S. Lee, C.-P. Chuang
FULL PAPER
Ph, R3 = Bz) was treated with ethyl acetoacetate (10a, R2 In all cases, isoindole products 8 were obtained with moder-
= Me) and manganese(III) acetate in acetic acid at 80 °C ate yields (Table 3, Entries 5–10).
for 14 h, desired product 11a was not found, and instead,
Table 3. Reaction between 2-(1-amidoalkyl)-1,4-naphthoquinones 7
benzo[f]isoindole-4,9-dione 8f was obtained in 34% yield
(Table 3, Entry 1).
and β-keto esters 10.
Entry
Quinone
β-Keto ester
Product
(% yield)
1[a]
2[b]
3[b]
4[b]
5[b]
6[b]
7[b]
8[b]
9[b]
10[b]
7b: R1 = Ph, R3 = Bz
7b: R1 = Ph, R3 = Bz
7b: R1 = Ph, R3 = Bz
7b: R1 = Ph, R3 = Bz
10a: R2 = Me 8f (34)
10a: R2 = Me 8f (60)
10b: R2 = Et
10c: R2 = Pr
8g (37)
8h (39)
7c: R1 = Ph, R3 = CO2Et 10a: R2 = Me 8i (56)
7c: R1 = Ph, R3 = CO2Et 10b: R2 = Et
7c: R1 = Ph, R3 = CO2Et 10c: R2 = Pr
8j (43)
8k (41)
7a: R1 = Ph, R3 = Ac
7a: R1 = Ph, R3 = Ac
7a: R1 = Ph, R3 = Ac
10a: R2 = Me 8a (50)
10b: R2 = Et
10c: R2 = Pr
8b (34)
8c (29)
[a] The reaction was performed under an atmosphere of N2 for
14 h. [b] The reaction was performed under an atmosphere of O2
for 30 min.
Scheme 4. Reaction between 2-(1-amidoalkyl)-1,4-naphthoquin-
ones 7 and β-keto esters 10.
Isoindole product 8f was formed by a similar acyl radical
addition mechanism shown in Scheme 2, and acyl radical
4a was presumably formed by the reaction mechanism out- Conclusions
lined in Scheme 5. Manganese(III) acetate oxidation of 10a
The silver-catalyzed decarboxylation of α-keto acids by
produces radical 12a. This radical intermediate 12a un-
dergoes oxygen trapping to give hydroperoxide 14a.[16]
Thermal fragmentation of 14a produces acyl radical 4a.[17]
This unusual acyl radical formation can be attributed to the
steric effect exerted by the 1-amidobenzyl group; the ad-
dition of radical 12a to the quinone ring of 7 is retarded by
this large 1-amidobenzyl group, and the formation of acyl
radical 4a by the oxygen trapping of radical 12a becomes
the major route. Although the expected reaction did not
occur, the formation of 8a prompted us to examine the ap-
plicability of this reaction. With the reasonable assumption
that oxygen takes part in the reaction leading to the forma-
tion of acyl radical 4a, the reaction between 7b and 10a was
repeated under an atmosphere of oxygen. In this case, the
yield of 8f increased to 60% and the reaction time was
shorten to 30 min (Table 3, Entry 2). Other β-keto esters 10
were also subjected to the manganese(III) acetate reaction
with 7b under oxygenated conditions. As shown in Table 3,
isoindole products 8 were obtained effectively, and the reac-
tion yields of 8 decreased as the size of the R2 group in-
creased (Table 3, Entries 2–4). Other N-protecting groups
were also employed to examine the scope of this reaction.
persulfate leads to acyl radicals, which can undergo efficient
radical addition to the C=C bond of 2-(1-hydroxyalkyl)-1,4-
naphthoquinones and 2-(1-amidoalkyl)-1,4-naphthoquin-
ones. This reaction provides an effective method for the syn-
thesis of naphtho[c]furan-4,7-diones and benzo[f]isoindole-
4,9-diones. In the presence of O2, manganese(III) acetate
oxidation of β-keto esters can also generate acyl radicals
from hydroperoxide, which then undergo a similar radical
addition reaction to 2-(1-amidoalkyl)-1,4-naphthoquin-
ones; subsequently, benzo[f]isoindole-4,9-diones are pro-
duced.
Experimental Section
General Considerations: Melting points were measured with a Büchi
melting point apparatus B-540. Infrared spectra were recorded with
1
a Hitachi 260–30 spectrometer. H and 13C NMR spectra were re-
corded with a Bruker Avance-300 or AMX-400 spectrometer.
Chemical shifts are reported in ppm relative to TMS as internal
reference. The multiplicity of the13C NMR signals was determined
by DEPT 135 experiments. Elemental analyses were performed
with a Heraeus CHN-Rapid Analyzer. Mass spectra were recorded
with a Jeol JMS-SX 102A mass spectrometer. Analytical thin-layer
chromatography was performed with precoated silica gel 60 F-254
plates (0.25 mm thick) from EM Laboratories and visualized by
UV. The reaction mixture was purified by column chromatography
over EM Laboratories silica gel (70–230 mesh).
Typical Procedure for the Silver(II)-Catalyzed Reaction between 2-
(1-Hydroxyalkyl)-1,4-naphthoquinones and α-Keto Acids: A mixture
of
2-(1-hydroxybenzyl)-1,4-naphthoquinone
(1a;
131 mg,
0.50 mmol), 2-oxopropionic acid (2a; 133 mg, 1.51 mmol), silver(I)
nitrate (34 mg, 0.20 mmol), and potassium persulfate (484 mg,
1.79 mmol) in acetonitrile (2 mL) and H2O (6 mL) was heated at
70 °C for 3 h. The reaction mixture was diluted with ethyl acetate
(100 mL), washed with water (3ϫ50 mL), dried (Na2SO4), and
concentrated in vacuo. The crude product was purified by column
Scheme 5. Probable mechanism for the formation of acyl radical 4.
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Metal Salt Mediated Radical Reactions of 2-Substituted-1,4-Naphthoquinones
chromatography over silica gel (20 g; ethyl acetate/hexane, 1:15) fol-
lowed by recrystallization (ethyl acetate/hexane) to give 3a (82 mg,
57%).
δ = 2.72 (s, 6 H, 2 CH3), 7.72–7.78 (m, 2 H, ArH), 8.25–8.31 (m,
2 H, ArH) ppm. 13C NMR (75.4 MHz, CDCl3): δ = 13.4 (2 q),
117.1 (2 s), 126.8 (2 d), 133.3 (2 d), 135.7 (2 s), 156.9 (2 s), 180.0
(2 s) ppm. C14H10O3 (226.06): calcd. C 74.33, H 4.46; found C
74.25, H 4.44.
1-Methyl-3-phenylnaphtho[2,3-c]furan-4,9-dione (3a): Yellow need-
les; yield 82 mg, 57%; m.p. 122–123 °C (ethyl acetate/hexane). IR
(KBr): ν = 3070, 1675, 1590, 1400, 1250 cm–1. 1H NMR (400 MHz,
1-Ethyl-3-methylnaphtho[2,3-c]furan-4,9-dione (3g): Light-yellow
powder; yield 87 mg, 56%; m.p. 111–112 °C (ethyl acetate/hexane).
˜
CDCl3): δ = 2.85 (s, 3 H, CH3), 7.45–7.56 (m, 3 H, ArH), 7.73–
7.81 (m, 2 H, ArH), 8.25–8.31 (m, 1 H, ArH), 8.32–8.37 (m, 1 H,
ArH), 8.44–8.51 (m, 2 H, ArH) ppm. 13C NMR (75.4 MHz,
CDCl3): δ = 13.5 (q), 116.7 (s), 118.6 (s), 126.3 (d), 127.32 (2 d),
127.35 (d), 128.1 (s), 128.2 (2 d), 130.5 (d), 133.1 (d), 133.4 (d),
134.7 (s), 136.0 (s), 155.2 (s), 157.8 (s), 178.6 (s), 180.2 (s) ppm.
C19H12O3 (288.08): calcd. C 79.16, H 4.20; found C 78.82, H 4.18.
IR (KBr): ν = 2980, 1670, 1595, 1415, 1245 cm–1. 1H NMR
˜
(400 MHz, CDCl3): δ = 1.34 (t, J = 7.6 Hz, 3 H, CH3), 2.73 (s, 3
H, CH3), 3.15 (q, J = 7.6 Hz, 2 H, CH2), 7.71–7.78 (m, 2 H, ArH),
8.24–8.31 (m, 2 H, ArH) ppm. 13C NMR (75.4 MHz, CDCl3): δ =
11.6 (q), 13.5 (q), 21.0 (t), 116.3 (s), 117.1 (s), 126.78 (d), 126.82
(d), 133.23 (d), 133.25 (d), 135.7 (s), 135.8 (s), 156.9 (s), 162.0 (s),
180.1 (s), 180.2 (s) ppm. C15H12O3 (240.08): calcd. C 74.99, H 5.03;
found C 74.97, H 5.02.
1-Ethyl-3-phenylnaphtho[2,3-c]furan-4,9-dione (3b): Yellow crystals;
yield 80 mg, 54%; m.p. 122–123 °C (ethyl acetate/hexane). IR
(KBr): ν = 2975, 1670, 1590, 1490, 1245 cm–1. 1H NMR (400 MHz,
Typical Procedure for the Synthesis of Benzo[f]isoindole-4,9-diones
12 by the Silver(II)-Catalyzed Reaction between 2-(1-Amidoalkyl)-
1,4-naphthoquinones and α-Keto Acids (Method A): A mixture of 2-
˜
CDCl3): δ = 1.42 (t, J = 7.6 Hz, 3 H, CH3), 3.29 (q, J = 7.6 Hz, 2
H, CH2), 7.46–7.57 (m, 3 H, ArH), 7.72–7.81 (m, 2 H, ArH), 8.26–
8.31 (m, 1 H, ArH), 8.32–8.38 (m, 1 H, ArH), 8.44–8.50 (m, 2 H,
ArH) ppm. 13C NMR (75.4 MHz, CDCl3): δ = 11.5 (q), 21.3 (t),
116.9 (s), 117.9 (s), 126.5 (d), 127.49 (d), 127.54 (2 d), 128.36 (2 d),
128.41 (s), 130.6 (d), 133.3 (d), 133.5 (d), 135.0 (s), 136.2 (s), 155.4
(s), 162.9 (s), 179.1 (s), 180.5 (s) ppm. C20H14O3 (302.09): calcd. C
79.46, H 4.67; found C 79.47, H 4.66.
[N-acetyl-1-(aminobenzyl)]-1,4-naphthoquinone
(7a;
127 mg,
0.42 mmol), 2-oxopropionic acid (2a; 111 mg, 1.25 mmol), silver(I)
nitrate (29 mg, 0.17 mmol), and potassium persulfate (408 mg,
1.51 mmol) in acetonitrile (10 mL) and H2O (5 mL) was heated at
70 °C for 3 h. The reaction mixture was diluted with ethyl acetate
(100 mL), washed with water (3ϫ50 mL), dried (Na2SO4), and
concentrated in vacuo. The crude product was purified by column
chromatography over silica gel (20 g; dichloromethane/hexane, 2:1)
followed by recrystallization (chloroform/hexane) to give 8a
(88 mg, 64%).
1-Phenyl-3-propylnaphtho[2,3-c]furan-4,9-dione 3c: Yellow needles;
yield 85 mg, 54%; m.p. 151–152 °C (ethyl acetate/hexane). IR
(KBr): ν = 2960, 1670, 1275, 1245, 925 cm–1. 1H NMR (400 MHz,
˜
CDCl3): δ = 1.07 (t, J = 7.4 Hz, 3 H, CH3), 1.89 (sext., J = 7.4 Hz,
2 H, CH2), 3.25 (t, J = 7.4 Hz, 2 H, CH2), 7.46–7.57 (m, 3 H,
ArH), 7.73–7.81 (m, 2 H, ArH), 8.26–8.32 (m, 1 H, ArH), 8.32–
8.39 (m, 1 H, ArH), 8.44–8.51 (m, 2 H, ArH) ppm. 13C NMR
(75.4 MHz, CDCl3): δ = 13.8 (q), 21.1 (t), 29.6 (t), 117.0 (s), 118.6
(s), 126.7 (d), 127.63 (d), 127.72 (2 d), 128.50 (2 d), 128.55 (s), 130.7
(d), 133.5 (d), 133.7 (d), 135.2 (s), 136.4 (s), 155.7 (s), 162.2 (s),
179.4 (s), 180.7 (s) ppm. C21H16O3 (316.11): calcd. C 79.73, H 5.10;
found C 79.63, H 4.98.
Typical Procedure for the Synthesis of Benzo[f]isoindole-4,9-Diones
12 by the Manganese(III)-Mediated reaction between 2-(1-Ami-
doalkyl)-1,4-Naphthoquinones and β-Keto Esters (Method B): A
mixture of 2-[N-benzoyl-1-(aminobenzyl)]-1,4-naphthoquinone (7b;
121 mg, 0.33 mmol), ethyl acetoacetate (10a; 871 mg, 6.7 mmol),
and manganese(III) acetate (881 mg, 3.28 mmol) in acetic acid
(10 mL) was heated at 70 °C under an atmosphere of O2 (1 atm)
for 30 min. The reaction mixture was diluted with ethyl acetate
(100 mL), washed with saturated aqueous sodium bisulfite (50 mL),
water (3ϫ50 mL), and aqueous saturated sodium hydrogen car-
bonate (3ϫ50 mL), dried (Na2SO4), and concentrated in vacuo.
The crude product was purified by column chromatography over
silica gel (20 g; dichloromethane/hexane, 2:1) followed by
recrystallization (chloroform/hexane) to give 8f (78 mg, 60%).
1-Isobutyl-3-phenylnaphtho[2,3-c]furan-4,9-dione (3d): Yellow crys-
tals; yield 89 mg, 54%; m.p. 117–118 °C (ethyl acetate/hexane). IR
(KBr): ν = 2950, 1670, 1280, 1245, 720 cm–1. 1H NMR (300 MHz,
˜
CDCl3): δ = 1.06 (d, J = 6.8 Hz, 6 H, 2 CH3), 2.27 (nont., J =
6.8 Hz, 1 H, CH), 3.15 (d, J = 6.8 Hz, 2 H, CH2), 7.43–7.59 (m, 3
H, ArH), 7.70–7.81 (m, 2 H, ArH), 8.22–8.31 (m, 1 H, ArH), 8.31–
8.39 (m, 1 H, ArH), 8.47 (d, J = 7.2 Hz, 2 H, ArH) ppm. 13C NMR
(75.4 MHz, CDCl3): δ = 22.5 (2 q), 28.3 (d), 36.3 (t), 117.0 (s),
119.2 (s), 126.7 (d), 127.6 (d), 127.7 (2 d), 128.50 (2 d), 128.54 (s),
130.7 (d), 133.5 (d), 133.7 (d), 135.3 (s), 136.4 (s), 155.8 (s), 161.7
(s), 179.4 (s), 180.7 (s) ppm. MS (EI, 70 eV): m/z (%) = 330 [M]+,
315 (27), 287 (100), 259 (2), 231 (2). HRMS: calcd. for C22H18O3
330.1256; found 330.1253.
2-Acetyl-1-methyl-3-phenylbenzo[f]isoindole-4,9-dione (8a): Yellow
crystals; yield 88 mg, 64% (method A), 55 mg, 50% (method B);
m.p. 184–185 °C (chloroform/hexane). IR (KBr): ν = 1740, 1670,
˜
1
1540, 1215, 1165 cm–1. H NMR (400 MHz, CDCl3): δ = 2.00 (s,
3 H, CH3), 2.86 (s, 3 H, CH3), 7.50–7.59 (m, 3 H, ArH), 7.59–7.61
(m, 2 H, ArH), 7.69 (td, J = 7.5, 1.6 Hz, 1 H, ArH), 7.72 (td, J =
7.5, 1.6 Hz, 1 H, ArH), 8.17 (dd, J = 7.5, 1.6 Hz, 1 H, ArH), 8.28
(dd, J = 7.5, 1.6 Hz, 1 H, ArH) ppm. 13C NMR (75.4 MHz,
CDCl3): δ = 12.6 (q), 28.2 (q), 118.5 (s), 118.6 (s), 126.66 (d), 126.68
(d), 128.6 (2 d), 129.85 (d), 129.88 (2 d), 130.2 (s), 133.07 (d), 133.11
(d), 135.74 (s), 135.76 (s), 135.82 (s), 138.0 (s), 173.1 (s), 179.9 (s),
181.3 (s) ppm. C21H15NO3 (329.11): calcd. C 76.58, H 4.59, N 4.25;
found C 76.68, H 4.62, N 4.25.
1,3-Diphenylnaphtho[2,3-c]furan-4,9-dione (3e): Yellow needles;
yield 131 mg, 75%; m.p. 229–230 °C (ethyl acetate/hexane). IR
1
(KBr): ν = 1670, 1490, 1270, 905, 715 cm–1. H NMR (400 MHz,
˜
CDCl3): δ = 7.47–7.58 (m, 6 H, ArH), 7.72–7.79 (m, 2 H, ArH),
8.28–8.35 (m, 2 H, ArH), 8.42–8.53 (m, 4 H, ArH) ppm. 13C NMR
(100.6 MHz, CDCl3): δ = 118.7 (2 s), 127.3 (2 d), 128.3 (4 d), 128.4
(2 s), 128.5 (4 d), 131.0 (2 d), 133.7 (2 d), 135.6 (2 s), 156.2 (2 s),
179.6 (2 s) ppm. C24H14O3 (350.09): calcd. C 82.27, H 4.03; found
C 82.23, H 4.02.
2-Acetyl-1-ethyl-3-phenylbenzo[f]isoindole-4,9-dione (8b): Yellow
crystals; yield 133 mg, 59% (method A), 42 mg, 34% (method B);
m.p. 146–147 °C (chloroform/hexane). IR (KBr): ν = 1745, 1665,
˜
1
1540, 1240, 1210 cm–1. H NMR (400 MHz, CDCl3): δ = 1.33 (t,
1,3-Dimethylnaphtho[2,3-c]furan-4,9-dione (3f): White crystals; yield
J = 7.4 Hz, 3 H, CH3), 2.01 (s, 3 H, CH3), 3.31 (q, J = 7.4 Hz, 2
H, CH2), 7.50–7.55 (m, 3 H, ArH), 7.56–7.62 (m, 2 H, ArH), 7.69
89 mg, 61%; m.p. 175–176 °C (ethyl acetate/hexane). IR (KBr): ν
˜
= 1670, 1605, 1415, 1385, 1245 cm–1. 1H NMR (400 MHz, CDCl3): (td, J = 7.4, 1.6 Hz, 1 H, ArH), 7.72 (td, J = 7.4, 1.6 Hz, 1 H,
Eur. J. Org. Chem. 2010, 3876–3882
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3879

Z.-Y. Lin, Y.-L. Chen, C.-S. Lee, C.-P. Chuang
FULL PAPER
ArH), 8.18 (dd, J = 7.4, 1.6 Hz, 1 H, ArH), 8.28 (dd, J = 7.4,
1
1545, 1255, 1000 cm–1. H NMR (400 MHz, CDCl3): δ = 1.27 (t,
1.6 Hz, 1 H, ArH) ppm. 13C NMR (75.4 MHz, CDCl3): δ = 13.8 J = 7.4 Hz, 3 H, CH3), 3.24 (q, J = 7.4 Hz, 2 H, CH2), 7.17–7.25
(q), 19.4 (t), 28.3 (q), 117.8 (s), 118.5 (s), 126.59 (d), 126.65 (d),
(m, 3 H, ArH), 7.29 (t, J = 7.9 Hz, 2 H, ArH), 7.39–7.46 (m, 2 H,
128.6 (2 d), 129.80 (d), 129.84 (2 d), 130.1 (s), 133.0 (d), 133.05 (d), ArH), 7.46–7.52 (m, 3 H, ArH), 7.71 (td, J = 7.3, 1.7 Hz, 1 H,
135.4 (s), 135.7 (s), 135.8 (s), 143.9 (s), 173.2 (s), 179.9 (s), 180.9 (s) ArH), 7.74 (td, J = 7.3, 1.7 Hz, 1 H, ArH), 8.22 (dd, J = 7.3,
ppm. C22H17NO3 (343.12): calcd. C 76.95, H 4.99, N 4.08; found C
76.92, H 4.98, N 4.03.
1.7 Hz, 1 H, ArH), 8.31 (dd, J = 7.3, 1.7 Hz, 1 H, ArH) ppm. 13C
NMR (75.4 MHz, CDCl3): δ = 13.9 (q), 19.4 (t), 117.7 (s), 117.9
(s), 126.7 (d), 126.9 (d), 127.9 (2 d), 128.7 (2 d), 129.2 (d), 129.5
(s), 130.1 (2 d), 130.4 (2 d), 132.6 (s), 133.1 (2 d), 134.9 (d), 135.8
(s), 136.1 (s), 137.3 (s), 144.1 (s), 170.3 (s), 180.2 (s), 181.3 (s) ppm.
C27H19NO3 (405.14): calcd. C 79.98, H 4.72, N 3.45; found C
79.95, H 4.74, N 3.36.
2-Acetyl-1-phenyl-3-propylbenzo[f]isoindole-4,9-dione (8c): Yellow
crystals; yield 100 mg, 43% (method A), 38 mg, 29% (method B);
m.p. 129–130 °C (chloroform/hexane). IR (KBr): ν = 1745, 1660,
˜
1
1540, 1230, 1215 cm–1. H NMR (400 MHz, CDCl3): δ = 1.06 (t,
J = 7.5 Hz, 3 H, CH3), 1.73 (sext., J = 7.5 Hz, 2 H, CH2), 2.00 (s,
3 H, CH3), 3.23–3.31 (m, 2 H, CH2), 7.46–7.56 (m, 3 H, ArH),
7.56–7.63 (m, 2 H, ArH), 7.69 (td, J = 7.4, 1.6 Hz, 1 H, ArH), 7.72
(td, J = 7.4, 1.6 Hz, 1 H, ArH), 8.18 (dd, J = 7.4, 1.6 Hz, 1 H,
ArH), 8.27 (dd, J = 7.4, 1.6 Hz, 1 H, ArH) ppm. 13C NMR
(100.6 MHz, CDCl3): δ = 14.0 (q), 23.0 (t), 27.6 (t), 28.4 (q), 118.3
(s), 118.5 (s), 126.66 (d), 126.73 (d), 128.6 (2 d), 129.86 (d), 129.91
(2 d), 130.2 (s), 133.05 (d), 133.13 (d), 135.6 (s), 135.8 (s), 135.9 (s),
142.6 (s), 173.3 (s), 180.0 (s), 181.0 (s) ppm. C23H19NO3 (357.14):
calcd. C 77.29, H 5.36, N 3.92; found C 77.17, H 5.32, N 3.85.
2-Benzoyl-3-phenyl-1-propylbenzo[f]isoindole-4,9-dione (8h): Yellow
crystals; yield 107 mg, 47% (method A), 54 mg, 39% (method B);
m.p. 119–120 °C (chloroform/hexane). IR (KBr): ν = 1710, 1660,
˜
1
1545, 1240, 1000 cm–1. H NMR (400 MHz, CDCl3): δ = 0.99 (t,
J = 7.5 Hz, 3 H, CH3), 1.68 (sext., J = 7.5 Hz, 2 H, CH2), 3.21 (t,
J = 7.5 Hz, 2 H, CH2), 7.15–7.25 (m, 3 H, ArH), 7.29 (t, J = 7.9 Hz,
2 H, ArH), 7.38–7.56 (m, 5 H, ArH), 7.70 (td, J = 7.3, 1.5 Hz, 1
H, ArH), 7.74 (td, J = 7.3, 1.5 Hz, 1 H, ArH), 8.22 (dd, J = 7.3,
1.5 Hz, 1 H, ArH), 8.30 (dd, J = 7.3, 1.5 Hz, 1 H, ArH) ppm. 13C
NMR (75.4 MHz, CDCl3): δ = 13.9 (q), 23.0 (t), 27.6 (t), 117.6 (s),
118.3 (s), 126.6 (d), 126.8 (d), 127.9 (2 d), 128.7 (2 d), 129.2 (d),
129.5 (s), 130.1 (2 d), 130.3 (2 d), 132.6 (s), 133.1 (2 d), 134.8 (d),
135.8 (s), 136.0 (s), 137.4 (s), 142.8 (s), 170.3 (s), 180.1 (s), 181.2 (s)
ppm. C28H21NO3 (419.15): calcd. C 80.17, H 5.05, N 3.34; found C
80.18, H 5.02, N 3.31.
2-Acetyl-1-isobutyl-3-phenylbenzo[f]isoindole-4,9-dione (8d): Yellow
crystals; yield 76 mg, 30% (method A); m.p. 157–158 °C (chloro-
form/hexane). IR (KBr): ν = 1750, 1660, 1540, 1230, 1215 cm–1.
˜
1H NMR (400 MHz, CDCl3): δ = 1.00 (d, J = 6.9 Hz, 6 H, 2 CH3),
1.99 (s, 3 H, CH3), 2.01 (nont., J = 6.9 Hz, 1 H, CH), 3.26 (d, J =
6.9 Hz, 2 H, CH2), 7.47–7.56 (m, 3 H, ArH), 7.56–7.65 (m, 2 H,
ArH), 7.68 (td, J = 7.4, 1.6 Hz, 1 H, ArH), 7.72 (td, J = 7.4, 1.6 Hz,
1 H, ArH), 8.18 (dd, J = 7.4, 1.6 Hz, 1 H, ArH), 8.27 (dd, J = 7.4,
1.6 Hz, 1 H, ArH) ppm. 13C NMR (100.6 MHz, CDCl3): δ = 22.3
(2 q), 28.6 (q), 29.8 (d), 33.7 (t), 118.6 (s), 118.9 (s), 126.8 (2 d),
128.7 (3 d), 129.9 (d), 130.0 (d), 130.2 (s), 133.10 (d), 133.18 (s +
d), 135.87 (s), 135.91 (s), 141.9 (s), 173.6 (s), 180.1 (s), 181.1 (s)
ppm. C24H21NO3 (371.15): calcd. C 77.61, H 5.70, N 3.77; found
C 77.58, H 5.75, N 3.70.
2-Ethoxycarbonyl-1-methyl-3-phenylbenzo[f]isoindole-4,9-dione (8i):
Yellow crystals; yield 118 mg, 84% (method A), 74 mg, 56%
(method B); m.p. 221–222 °C (chloroform/hexane). IR (KBr): ν =
˜
1765, 1670, 1560, 1240, 1015 cm–1. 1H NMR (400 MHz, CDCl3):
δ = 0.90 (t, J = 7.1 Hz, 3 H, CH3), 2.93 (s, 3 H, CH3), 4.13 (q, J
= 7.1 Hz, 2 H, OCH2), 7.47 (s, 5 H, ArH), 7.67 (td, J = 7.4, 1.5 Hz,
1 H, ArH), 7.70 (td, J = 7.4, 1.5 Hz, 1 H, ArH), 8.15 (dd, J = 7.4,
1.5 Hz, 1 H, ArH), 8.27 (dd, J = 7.4, 1.5 Hz, ArH) ppm. 13C NMR
(100.6 MHz, CDCl3): δ = 12.8 (q), 13.1 (q), 64.9 (t), 118.7 (s), 118.9
(s), 126.75 (d), 126.84 (d), 128.0 (2 d), 129.0 (d), 129.3 (2 d), 131.1
(s), 133.2 (2 d), 135.8 (s), 135.9 (s), 137.3 (s), 138.7 (s), 150.6 (s),
179.9 (s), 181.4 (s) ppm. C22H17NO4 (359.11): calcd. C 73.53, H
4.77, N 3.90; found C 73.31, H 4.75, N 3.84.
1-Acetyl-1,3-diphenylbenzo[f]isoindole-4,9-dione (8e): Yellow crys-
tals; yield 35 mg, 13% (method A); m.p. 203–204 °C (chloroform/
hexane). IR (KBr): ν = 1745, 1665, 1480, 1215, 990 cm–1. 1H NMR
˜
(400 MHz, CDCl3): δ = 1.99 (s, 3 H, CH3), 7.45–7.54 (m, 6 H,
ArH), 7.54–7.62 (m, 4 H, ArH), 7.65–7.73 (m, 2 H, ArH), 8.15–
8.22 (m, 2 H, ArH) ppm. 13C NMR (75.4 MHz, CDCl3): δ = 28.9
(q), 118.9 (2 s), 126.8 (2 d), 128.5 (4 d), 129.6 (2 s), 129.8 (2 d),
130.1 (4 d), 133.3 (2 d), 135.8 (2 s), 137.0 (2 s), 172.6 (s), 180.2 (2
s) ppm. MS (EI, 70 eV): m/z (%) = 391 [M]+, 366 (14), 349 (100),
320 (2), 291 (4), 265 (3). HRMS: calcd. for C26H17NO3 391.1208;
found 391.1204.
2-Ethoxycarbonyl-1-ethyl-3-phenylbenzo[f]isoindole-4,9-dione (8j):
Yellow crystals; yield 117 mg, 84% (method A), 58 mg, 43%
(method B); m.p. 126–127 °C (chloroform/hexane). IR (KBr): ν =
˜
1765, 1665, 1540, 1250, 1230 cm–1. 1H NMR (400 MHz, CDCl3):
δ = 0.92 (t, J = 7.1 Hz, 3 H, CH3), 1.35 (t, J = 7.4 Hz, 3 H, CH3),
3.40 (q, J = 7.4 Hz, 2 H, CH2), 4.14 (q, J = 7.1 Hz, 2 H, OCH2),
7.43–7.55 (m, 5 H, ArH), 7.68 (td, J = 7.3, 1.5 Hz, 1 H, ArH), 7.72
(td, J = 7.3, 1.5 Hz, 1 H, ArH), 8.17 (dd, J = 7.3, 1.5 Hz, 1 H,
ArH), 8.28 (dd, J = 7.3, 1.5 Hz, 1 H, ArH) ppm. 13C NMR
(100.6 MHz, CDCl3): δ = 13.1 (q), 13.7 (q), 19.7 (t), 65.1 (t), 118.0
(s), 118.8 (s), 126.8 (d), 126.9 (d), 128.0 (2 d), 129.1 (d), 129.4 (2
d), 130.9 (s), 133.2 (2 d), 135.9 (s), 136.0 (s), 137.2 (s), 144.4 (s),
150.6 (s), 180.0 (s), 181.2 (s) ppm. C23H19NO4 (373.13): calcd. C
73.98, H 5.13, N 3.75; found C 73.87, H 5.13, N 3.69.
2-Benzoyl-1-methyl-3-phenylbenzo[f]isoindole-4,9-dione (8f): Yellow
crystals; yield 156 mg, 73% (method A), 78 mg, 60% (method B);
m.p. 204–205 °C (chloroform/hexane). IR (KBr): ν = 1715, 1665,
˜
1
1485, 1240, 1050 cm–1. H NMR (400 MHz, CDCl3): δ = 2.76 (s,
3 H, CH3), 7.19–7.26 (m, 3 H, ArH), 7.32 (t, J = 7.9 Hz, 2 H,
ArH), 7.42–7.48 (m, 2 H, ArH), 7.48–7.56 (m, 3 H, ArH), 7.68–
7.77 (m, 2 H, ArH), 8.20–8.24 (m, 1 H, ArH), 8.28–8.34 (m, 1 H,
ArH) ppm. 13C NMR (75.4 MHz, CDCl3): δ = 12.2 (q), 117.7 (s),
118.6 (s), 126.6 (d), 126.8 (d), 127.9 (2 d), 128.8 (2 d), 129.2 (d),
129.4 (s), 130.0 (2 d), 130.4 (2 d), 132.5 (s), 133.08 (d), 133.13 (d),
134.9 (d), 135.7 (s), 136.1 (s), 137.5 (s), 137.7 (s), 170.1 (s), 180.0
(s), 181.5 (s) ppm. C26H17NO3 (391.12): calcd. C 79.78, H 4.38, N
3.58; found C 79.76, H 4.35, N 3.52.
2-Ethoxycarbonyl-1-phenyl-3-propylbenzo[f]isoindole-4,9-dione (8k):
Yellow crystals; yield 92 mg, 60% (method A), 59 mg, 41%
(method B); m.p. 143–144 °C (chloroform/hexane). IR (KBr): ν =
˜
1
1770, 1665, 1540, 1230, 990 cm–1. H NMR (400 MHz, CDCl3): δ
= 0.91 (t, J = 7.1 Hz, 3 H, CH3), 1.07 (t, J = 7.5 Hz, 3 H, CH3),
1.76 (sext., J = 7.5 Hz, 2 H, CH2), 3.36 (t, J = 7.5 Hz, 2 H, CH2),
4.12 (q, J = 7.1 Hz, 2 H, OCH2), 7.42–7.54 (m, 5 H, ArH), 7.68
(td, J = 7.4, 1.6 Hz, 1 H, ArH), 7.72 (td, J = 7.4, 1.6 Hz, 1 H,
2-Benzoyl-1-ethyl-3-phenylbenzo[f]isoindole-4,9-dione (8g): Yellow
crystals; yield 73 mg, 65% (method A), 49 mg, 37% (method B);
m.p. 151–152 °C (chloroform/hexane). IR (KBr): ν = 1710, 1670,
˜
3880
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 3876–3882

Metal Salt Mediated Radical Reactions of 2-Substituted-1,4-Naphthoquinones
[4]
a) A. Citterio, R. Sebastiano, A. Marion, J. Org. Chem. 1991,
56, 5328–5335; b) A. Citterio, R. Sebastiano, M. Nicolini, Tet-
rahedron 1993, 49, 7743–7760; c) Y.-L. Wu, C.-P. Chuang, P.-
Y. Lin, Tetrahedron 2000, 56, 6209–6217; d) Y.-J. Liao, Y.-L.
Wu, C.-P. Chuang, Tetrahedron 2003, 59, 3511–3520.
a) M.-C. Jiang, C.-P. Chuang, J. Org. Chem. 2000, 65, 5409–
5412; b) Y.-L. Wu, C.-P. Chuang, Tetrahedron Lett. 2001, 42,
1717–1719; c) Y.-L. Wu, C.-P. Chuang, P.-Y. Lin, Tetrahedron
2001, 57, 5543–5549; d) A.-I. Tsai, Y.-L. Wu, C.-P. Chuang,
Tetrahedron 2001, 57, 7829–7837; e) C.-C. Tseng, Y.-L. Wu, C.-
P. Chuang, Tetrahedron 2002, 58, 7625–7633; f) C.-M. Tseng,
Y.-L. Wu, C.-P. Chuang, Tetrahedron 2004, 60, 12249–12260; g)
H.-L. Chen, C.-Y. Lin, Y.-C. Cheng, A.-I. Tsai, C.-P. Chuang,
Synthesis 2005, 977–985; h) C.-Y. Lin, Y.-C. Cheng, A.-I. Tsai,
C.-P. Chuang, Org. Biomol. Chem. 2006, 4, 1097–1103.
ArH), 8.17 (dd, J = 7.4, 1.6 Hz, 1 H, ArH), 8.27 (dd, J = 7.4,
1.6 Hz, 1 H, ArH) ppm. 13C NMR (100.6 MHz, CDCl3): δ = 13.1
(q), 14.0 (q), 22.9 (t), 27.8 (t), 65.0 (t), 118.4 (s), 118.7 (s), 126.7
(d), 126.9 (d), 128.0 (2 d), 129.1 (d), 129.3 (2 d), 130.9 (s), 133.13
(d), 133.16 (d), 135.85 (s), 135.92 (s), 137.2 (s), 143.0 (s), 150.7 (s),
180.0 (s), 181.1 (s) ppm. C24H21NO4 (387.15): calcd. C 74.40, H
5.46, N 3.62; found C 74.41, H 5.47, N 3.54.
[5]
2-Ethoxycarbonyl-1-isobutyl-3-phenylbenzo[f]isoindole-4,9-dione (8l):
Yellow powders; yield 89 mg, 55% (method A); m.p. 89–90 °C
(chloroform/hexane). IR (KBr): ν = 1765, 1665, 1545, 1240,
˜
1
990 cm–1. H NMR (400 MHz, CDCl3): δ = 0.90 (t, J = 7.2 Hz, 3
H, CH3), 1.01 (d, J = 6.9 Hz, 6 H, 2 CH3), 2.06 (nont., J = 6.9 Hz,
1 H, CH), 3.34 (d, J = 6.9 Hz, 2 H, CH2), 4.10 (q, J = 7.2 Hz, 2
H, OCH2), 7.43–7.53 (m, 5 H, ArH), 7.68 (td, J = 7.5, 1.7 Hz, 1
H, ArH), 7.71 (td, J = 7.5, 1.7 Hz, 1 H, ArH), 8.17 (dd, J = 7.5,
1.7 Hz, 1 H, ArH), 8.27 (dd, J = 7.5, 1.7 Hz, 1 H, ArH) ppm. 13C
NMR (100.6 MHz, CDCl3): δ = 13.1 (q), 22.3 (2 q), 29.7 (d), 33.9
(t), 65.0 (t), 118.7 (s), 119.0 (s), 126.81 (d), 126.87 (d), 128.0 (2 d),
129.1 (d), 129.4 (2 d), 131.0 (s), 133.15 (d), 133.2 (d), 135.92 (s),
135.94 (s), 137.5 (s), 142.3 (s), 150.9 (s), 180.1 (s), 181.1 (s) ppm.
C25H23NO4 (401.16): calcd. C 74.79, H 5.77, N 3.49; found C
74.76, H 5.67, N 3.48.
[6]
[7]
J. M. Anderson, J. K. Kochi, J. Am. Chem. Soc. 1970, 92, 1651–
1659.
a) N. Kanomata, H. Nagahara, M. Tada, J. Heterocycl. Chem.
1992, 29, 1567–1571; b) R. Jain, L. A. Cohen, N. A. El-Kadi,
M. M. King, Tetrahedron 1997, 53, 2365–2370; c) K. B. Han-
sen, S. A. Springfield, R. Desmond, P. N. Devine, E. J. J. Gra-
bowski, P. J. Reider, Tetrahedron Lett. 2001, 42, 7353–7355.
a) N. Jacobsen, K. Torsell, Acta Chem. Scand. 1973, 27, 3211–
3216; b) P. M. Brown, R. H. Thomson, J. Chem. Soc. Perkin
Trans. 1 1976, 997–1000; c) B. Kesteleyn, N. De Kimpe, L.
Van Puyvelde, J. Org. Chem. 1999, 64, 1173–1179; d) G. A.
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6650.
a) R. H. Thomson, Natural Occurring Quinones IV: Recent Ad-
vances, Chapman and Hall, London, 1997; b) A. P. Krapcho,
D. J. Waterhouse, Heterocycles 1999, 51, 737–750; c) M. J. Pig-
gott, Tetrahedron 2005, 61, 9929–9954.
a) T. Hanumaiah, G. S. R. Rao, C. P. Rao, K. V. J. Rao, H. J.
Cowe, P. J. Cox, R. A. Howie, D. S. Marshall, R. H. Thomson,
Tetrahedron 1985, 41, 635–642; b) A. Miljkovic, P. G. Mantle,
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4109–4112.
[8]
2-Ethoxycarbonyl-1,3-diphenylbenzo[f]isoindole-4,9-dione (8m): Yel-
low crystals; yield 54 mg, 33% (method A); m.p. 146–147 °C (chlo-
roform/hexane). IR (KBr): ν = 1775, 1670, 1240, 1225, 990 cm–1.
˜
[9]
1H NMR (400 MHz, CDCl3): δ = 0.79 (t, J = 7.2 Hz, 3 H, CH3),
3.97 (q, J = 7.2 Hz, 2 H, OCH2), 7.46–7.54 (m, 6 H, ArH), 7.54–
7.62 (m, 4 H, ArH), 7.66–7.73 (m, 2 H, ArH), 8.16–8.22 (m, 2 H,
ArH) ppm. 13C NMR (75.4 MHz, CDCl3): δ = 12.9 (q), 65.3 (t),
118.9 (2 s), 126.9 (2 d), 128.1 (4 d), 129.5 (2 d), 129.7 (4 d), 129.8
(2 s), 133.3 (2 d), 135.8 (2 s), 137.9 (2 s), 150.3 (s), 180.1 (2 s) ppm.
C27H19NO4 (421.13): calcd. C 76.95, H 4.54, N 3.32; found C
76.68, H 4.59, N 3.28.
[10]
Supporting Information (see footnote on the first page of this arti-
cle): Experimental details for the preparation of 2-substituted-1,4-
naphthoquinones 1 and 7; 1H and 13C NMR spectroscopic data
for naphtho[2,3-c]furan-4,9-diones 4 and benzo[f]isoindole-4,9-di-
ones 8.
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We are grateful to the National Science Council of ROC for finan-
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Eur. J. Org. Chem. 2010, 3876–3882
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3881

Z.-Y. Lin, Y.-L. Chen, C.-S. Lee, C.-P. Chuang
FULL PAPER
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Received: February 27, 2010
Published Online: May 27, 2010
3882
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 3876–3882