A novel manganese(iii) acetate mediated reaction between 2-benzoyl-1,4-naphthoquinones and 1,3-dicarbonyl compounds

Article abstract of DOI:10.1039/b516285h

A manganese(iii)-mediated reaction between 2-benzoyl-1,4-naphthoquinones and 1,3-dicarbonyl compounds is described. This reaction provides an effective method for the synthesis of naphtho[2,3-c]furan-4,9-diones and naphthacene-5,12-diones, and it shows fa

Full text of DOI:10.1039/b516285h

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
A novel manganese(III) acetate mediated reaction between
2-benzoyl-1,4-naphthoquinones and 1,3-dicarbonyl compounds
Chien-Yu Lin, Yu-Chih Cheng, An.-I. Tsai and Che-Ping Chuang*
Received 16th November 2005, Accepted 25th January 2006
First published as an Advance Article on the web 8th February 2006
DOI: 10.1039/b516285h
A manganese(III)-mediated reaction between 2-benzoyl-1,4-naphthoquinones and 1,3-dicarbonyl
compounds is described. This reaction provides an effective method for the synthesis of
naphtho[2,3-c]furan-4,9-diones and naphthacene-5,12-diones, and it shows fair to high
chemoselectivity depending on the electronic effect of the benzoyl group substituent on the reactants.
With ethyl benzoylacetate and 1,3-diketones, the novel naphtho[2,3-c]furan-4,9-diones were produced
effectively with high selectivity.
Table 1 Reaction with b-ketoesters
Introduction
Entry Quinone
b-Ketoester
Products (yield (%))
Carbon–carbon bond-forming reactions mediated by radicals
have received considerable attention in organic synthesis during
the last two decades.1,2 Compounds containing the quinone group
represent an important class of biologically active molecules that
are widespread in nature.3 Oxidative free-radical reaction mediated
by metal salts 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.2,4–6 The free-radical reaction of 1,4-
naphthoquinones has been reported.6,7 Previously, we found that
the manganese(III) acetate mediated oxidative free-radical reac-
tion of 2-benzyl-(3-ethoxycarbonylmethyl)-1,4-naphthoquinones
produced naphthacene-5,12-diones effectively. In contrast, with 2-
benzoyl-(3-ethoxycarbonylmethyl)-1,4-naphthoquinones, in addi-
tion to the expected 6-hydroxynaphthacene-5,12-diones, the novel
naphtho[2,3-c]furan-4,9-diones were also produced as the major
products. This is presumably due to the electron deficiency of the
benzoyl group, which disfavours the intramolecular cyclization
of the electrophilic radical intermediate onto the C–C double
bond of the benzoyl group.6g These naphthacene-5,12-diones
can also be generated directly from the intermolecular oxidative
free-radical reaction of 2-benzyl-1,4-naphthoquinones with 1,3-
dicarbonyl compounds.6d This report describes our results of the
manganese(III) acetate mediated reactions between 2-benzoyl-1,4-
naphthoquinones and 1,3-dicarbonyl compounds.
n
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
1a: R1 = H, R2 = H
2a: R3 = PrCO 3a (46), 4a (20)
1b: R1 = H, R2 = Me 2a: R3 = PrCO 3b (41), 4b (22)
n
1c: R1 = H, R2 = Br
1d: R1 = H, R2 = Cl
1e: R1 = Me, R2 = H
2a: R3 = PrCO 3c (48), 4c (3)
n
n
2a: R3 = PrCO 3d (54), 4d (3)
n
2a: R3 = PrCO 3e (51), 4e (15)
1f: R1 = Me, R2 = Me 2a: R3 = PrCO 3f (53), 4f (16)
n
1g: R1 = Br, R2 = H
1h: R1 = Cl, R2 = H
1i: R1 = Cl, R2 = Cl
1a: R1 = H, R2 = H
1b: R1 = H, R2 = Cl
1a: R1 = H, R2 = H
2a: R3 = PrCO 3g (50), 4g (5)
n
n
2a: R3 = PrCO 3h (45), 4h (6)
n
2a: R3 = PrCO 3i (46), 4i (6)
i
2b: R3 = PrCO 3a (50), 4a (12)
i
2b: R3 = PrCO 3d (50), 4d (2)
2c: R3 = PhCO 3a (54), 4a (3)
1b: R1 = H, R2 = Me 2c: R3 = PhCO 3b (48), 4b (3)
1c: R1 = H, R2 = Br
1d: R1 = H, R2 = Cl
1e: R1 = Me, R2 = H
2c: R3 = PhCO 3c (48), 4c (2)
2c: R3 = PhCO 3d (52), 4d (2)
2c: R3 = PhCO 3e (68), 4e (6)
2c: R3 = PhCO 3g (42), 4g (3)
2c: R3 = PhCO 3h (45), 4h (5)
2c: R3 = PhCO 3i (44), 4i (2)
1f: R1 = Me, R2 = Me 2c: R3 = PhCO 3f (65), 4f (5)
1g: R1 = Br, R2 = H
1h: R1 = Cl, R2 = H
1i: R1 = Cl, R2 = Cl
the mechanistic details of this reaction are unclear, 3a and 4a
may be formed by the reaction route presented in Scheme 1.
Manganese(III) acetate oxidation of 2a produces radical 5a. This
radical intermediate 5a undergoes intermolecular addition to
the quinone ring followed by oxidation to give 6a,8 which was
then oxidized by manganese(III) acetate to generate 7a. Radical
7a undergoes either a six-membered-ring free-radical cyclization
and subsequent aromatization to give 8a, which undergoes a
further retro-Claisen condensation to produce 4a (path a)9 or
oxidation to give 9a (path b). This cation intermediate 9a
undergoes a five-membered-ring cyclization followed by retro-
Claisen condensation to generate 3a.10 Analogous results were
obtained with other 2-benzoyl-1,4-naphthoquinones 1, and the
results are summarized in Table 1 (entries 1–9). In all cases,
naphtho[2,3-c]furan-4,9-dione 3 and naphthacene-5,12-dione 4
were obtained in fair yields. Contrary to the reactions of 2-benzyl-
1,4-naphthoquinones with b-ketoesters,6d 3 is the major product.
It indicates that the electron deficiency of the benzoyl group
disfavours the intramolecular cyclization of electrophilic radical 7
onto the C–C double bond of benzoyl group (path a). Interestingly,
Results and discussion
We first tried the manganese(III)-mediated reaction of 2-benzoyl-
1,4-naphthoquinones 1 with b-ketoesters 2 (Scheme 1). When
2-benzoyl-1,4-naphthoquinone (1a) was treated with ethyl bu-
tyrylacetate (2a, R3
=
nPrCO) and manganese(III) acetate in
acetic acid at 70 ◦C, in addition to the expected naphthacene
5,12-dione 4a (20%), the novel naphtho[2,3-c]furan-4,9-dione 3a
was also obtained in 46% yield (Table 1, entry 1). Although
Department of Chemistry, National Cheng Kung University, Tainan, Taiwan,
70101, Republic of China. E-mail: cpchuang@mail.ncku.edu.tw; Fax: +886-
6-2740552
This journal is
The Royal Society of Chemistry 2006
Org. Biomol. Chem., 2006, 4, 1097–1103 | 1097
©

View Article Online
Scheme 1
the reaction of 1 bearing an additional electron-withdrawing
halogeno group gave the corresponding products 3 and 4 with
an excellent 3/4 ratio (entries 3, 4, 7–9). These results can be
rationalized by considering that the electron deficiency of radical
intermediate 7 makes the rate of six-membered-ring cyclization
to the benzene ring bearing an electron-withdrawing halogeno
group much slower (path a), making the competitive oxidation of
7 the major route (path b). The formation of naphtho[2,3-c]furan-
4,9-diones is interesting, because they are one of the subsets of
natural products containing a c-fused furan ring.3c To improve
the chemoselectivity, reaction of 2-benzoyl-1,4-naphthoquinone
1a with other b-ketoesters was next investigated. Reaction of 2-
benzoyl-1,4 naphthoquinone 1a with ethyl isobutyrylacetate (2b,
naphthoquinone (1a) with 2d and manganese(III) acetate under
the above conditions led to the formation of 3a and 4a in 19%
and 38% yields, respectively (Table 2, entry 1). These two products
3a and 4a were presumably generated by the decarboxylation of
8d and 10d, respectively. Compounds 8d and 10d were formed by
a route similar to that for 8a and 10a (Scheme 1). The scope
of this reaction is shown in Table 2 (entries 1–9). In contrast
to the reaction between 2-benzoyl-1,4-naphthoquinones 1 and b-
ketoesters, this reaction is less selective, particularly for 2-benzoyl-
1,4-naphthoquinones 1a and 1b, for which naphthacene-5,12-
diones 4a and 4b are the major products (entries 1 and 2). It can
be rationalized that the radical intermediate 7d bearing a weaker
electron-withdrawing CO2H group is less electron-deficient, and
this makes the intramolecular cyclization of 7d (path a) faster than
that of 7a. Similar to the results shown above for ethyl butyry-
lacetate (2a), the presence of an additional electron-withdrawing
halogeno group on the benzoyl group appears to increase the ratio
of 3/4, producing naphtho[2,3-c]furan-4,9-dione 3 as the major
product. In particular, naphtho[2,3-c]furan-4,9-diones 3g–i were
produced with high selectivities from the corresponding quinone
1 bearing an ortho-halogeno group (entries 7–9).
i
R3 = PrCO) and manganese(III) acetate in acetic acid afforded 3a
and 4a in 50% and 12% yields, respectively (entry 10). The 3a/4a
ratio rose to 54 : 3 when ethyl benzoylacetate (2c, R3 = PhCO)
was employed (entry 12). The selectivity of this reaction increases
as the size of substituents (R3) increases. This can be attributed to
the steric effect exerted by R3 group – the cyclization of 7 (path a)
is retarded by the larger R3 group and the oxidation of 7 becomes
the major route (path b). On the basis of this finding, by choosing
ethyl benzoylacetate (2c) as the radical precursor, the generalities
of this reaction were examined with a variety of 2-benzoyl-
1,4-naphthoquinones 1. The results are summarized in Table 1
(entries 12–20). In all cases, 2-benzoyl-1,4-naphthoquinone 1 was
converted to the corresponding product 3 with high selectivity.
Next, we investigated this manganese(III)-mediated reaction
with ethyl hydrogen malonate (2d). Treatment of 2-benzoyl-1,4-
We have continued to study this manganese(III) mediated
reaction with 1,3-diketones 11 (Eq. 1). When 2-benzoyl-1,4-
naphthoquinone 1a was treated with pentanedione (11a) and
manganese(III) acetate, 12a and 13a were obtained in 41%
and 8% yields, respectively (Table 3, entry 1). Other examples
were also summarized in Table 3. In most cases, 2-benzoyl-1,4-
naphthoquinone 1 was converted to the corresponding furan
1098 | Org. Biomol. Chem., 2006, 4, 1097–1103
This journal is
The Royal Society of Chemistry 2006
©

View Article Online
Table 2 Reaction with ethyl hydrogen malonate
Entry Quinone Malonate
from readily available 2-benzoyl-1,4-naphthoquinones and 1,3-
dicarbonyl compounds. The product distributions are highly
dependent on the 1,3-dicarbonyl compounds used and the elec-
tronic effect of the substituents on benzoyl groups. With ethyl
benzoylacetate and 1,3-diketones, the novel naphtho[2,3-c]furan-
4,9-diones were produced effectively in high selectivities.
Products (yield (%))
1
2
3
4
5
6
7
8
9
1a: R1 = H, R2 = H
2d: R3 = CO2H 3a (19), 4a (38)
2d: R3 = CO2H 3c (26), 4c (16)
2d: R3 = CO2H 3d (32), 4d (16)
2d: R3 = CO2H 3e (30), 4e (14)
2d: R3 = CO2H 3g (50), 4g (5)
2d: R3 = CO2H 3h (51), 4h (4)
2d: R3 = CO2H 3i (57), 4i (2)
1b: R1 = H, R2 = Me 2d: R3 = CO2H 3b (12), 4b (39)
1c: R1 = H, R2 = Br
1d: R1 = H, R2 = Cl
1e: R1 = Me, R2 = H
1f: R1 = Me, R2 = Me 2d: R3 = CO2H 3f (34), 4f (19)
Experimental
1g: R1 = Br, R2 = H
1h: R1 = Cl, R2 = H
1i: R1 = Cl, R2 = Cl
General considerations
Melting points are uncorrected. Infrared spectra were taken with
1
a Hitachi 260-30 spectrometer. H and 13C NMR spectra were
Table 3 Reaction with 1,3-diketones
Entry Quinone 1,3-Diketone
recorded on a Bruker AVANCE-300, AMX-400 or AVANCE-
500 spectrometer. Chemical shifts are reported in ppm relative to
TMS as internal reference. Elemental analyses were performed
with Heraeus CHN-Rapid Analyzer. Mass spectra were recorded
on a Jeol JMS-SX 102 A 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 silica gel (70–230 mesh) from EM Laboratories. The starting
2-benzoyl-1,4-naphthoquinones 1 were synthesized by the CAN
oxidative demethylation11 of the corresponding 2-benzoyl-1,4-
dimethoxynaphthalenes.12 The spectral data of 3a–h and 4a–f have
been reported.6g
Products (yield (%))
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
1a: R1 = H, R2 = H
11a: R3 = MeCO 12a (41), 13a (8)
11a: R3 = MeCO 12c (43)
11a: R3 = MeCO 12d (47)
11a: R3 = MeCO 12e (40), 13c (9)
1b: R1 = H, R2 = Me 11a: R3 = MeCO 12b (42), 13b (9)
1c: R1 = H, R2 = Br
1d: R1 = H, R2 = Cl
1e: R1 = Me, R2 = H
1f: R1 = Me, R2 = Me 11a: R3 = MeCO 12f (47), 13d (7)
1g: R1 = Br, R2 = H
1h: R1 = Cl, R2 = H
1i: R1 = Cl, R2 = Cl
1a: R1 = H, R2 = H
11a: R3 = MeCO 12g (52)
11a: R3 = MeCO 12h (56)
11a: R3 = MeCO 12i (65)
i
11b: R3 = PrCO 12j (47)
1b: R1 = H, R2 = Me 11b: R3 = PrCO 12k (38)
i
1c: R1 = H, R2 = Br
11b: R3 = PrCO 12l (38)
i
1a: R1 = H, R2 = H
11c: R3 = PhCO 12m (70)
1b: R1 = H, R2 = Me 11c: R3 = PhCO 12n (71)
1c: R1 = H, R2 = Br
1d: R1 = H, R2 = Cl
1e: R1 = Me, R2 = H
11c: R3 = PhCO 12o (65)
11c: R3 = PhCO 12p (70)
11c: R3 = PhCO 12q (74)
11a: R3 = PhCO 12s (82)
11a: R3 = PhCO 12t (74)
11a: R3 = PhCO 12u (76)
Typical experimental procedure for the reaction between
2-benzoyl-1,4-naphthoquinones and b-ketoesters
1f: R1 = Me, R2 = Me 11c: R3 = PhCO 12r (70)
1g: R1 = Br, R2 = H
1h: R1 = Cl, R2 = H
1i: R1 = Cl, R2 = Cl
A mixture of 2-benzoyl-1,4-naphthoquinone (1a) (162 mg, 0.62
mmol), ethyl butyrylacetate (2a) (385 mg, 2.43 mmol) and man-
ganese(III) acetate (654 g, 2.44 mmol) in acetic acid (10 cm3) was
heated at 70 ◦C for 30 min. The reaction mixture was diluted with
ethyl acetate (100 cm3), washed with saturated aqueous sodium
bisulfite (50 cm3), water (3 × 50 cm3), aqueous saturated sodium
bicarbonate (3 × 50 cm3), dried (Na2SO4), and concentrated in
vacuo. The crude product was purified by column chromatography
over silica gel (20 g) (eluting with 2 : 1 dichloromethane–hexane)
followed by recrystallization (CHCl3–hexane) to give 3a (98 mg,
46%) and 4a (42 mg, 20%).
product 12 in high selectivity. Again, the selectivity of this reaction
increases as the size of 1,3-diketone increases.
Typical experimental procedure for the reaction between
2-benzoyl-1,4-naphthoquinones and ethyl hydrogen malonate
A mixture of 2-benzoyl-1,4-naphthoquinone (1a) (153 mg, 0.57
mmol), ethyl hydrogen malonate (2d) (307 mg, 2.32 mmol) and
manganese(III) acetate (614 mg, 2.29 mmol) in acetic acid (10 cm3)
◦
was heated at 70 C for 1 h, and more ethyl hydrogen malonate
(2d) (153 mg, 1.15 mmol) and manganese(III) acetate (309 mg,
1.15 mmol) was then added. After being stirred for 1 h, the
reaction mixture was worked up as described above and the crude
product was purified by column chromatography over silica gel
(20 g) (eluting with 2 : 1 dichloromethane–hexane) followed by
recrystallization (CHCl3–hexane) to give 3a (39 mg, 19%) and 4a
(76 mg, 38%).
(1)
Conclusions
1,4-Naphthquinone 6, generated by the free-radical addition of
radical intermediate 5 to the C–C double bond of the quinone
ring, undergoes efficient manganese(III)-mediated cyclization re-
actions. This reaction provides a method for the synthesis
of naphtho[2,3-c]furan-4,9-diones and naphthacene-5,12-diones
3-(2,4-Dichlorophenyl)-4,9-dioxo-4,9-dihydronaphtho[2,3-c]-
furan-1-carboxylic acid ethyl ester 3i. Yellow needles; mp 179–
180 ◦C (from CHCl3–hexane); (Found: C, 60.78; H, 2.96.
This journal is
The Royal Society of Chemistry 2006
Org. Biomol. Chem., 2006, 4, 1097–1103 | 1099
©

View Article Online
C21H12Cl2O5 requires C, 60.74; H, 2.91%); mmax(CHCl3)/cm−1 3020,
1730, 1685, 1585 and 1285; dH(400 MHz; CDCl3; Me4Si) 1.49 (3 H,
t, J 7.1, CH3), 4.54 (2 H, q, J 7.1, OCH2), 7.43 (1 H, dd, J 8.3 and
1.9, ArH), 7.60 (1 H, d, J 1.9, ArH), 7.65 (1 H, d, J 8.3, ArH),
7.77–7.85 (2 H, m, ArH), 8.20–8.26 (1 H, m, ArH) and 8.31–8.37
(1 H, m, ArH); dC(100.6 MHz; CDCl3; Me4Si) 14.2 (q), 62.6 (t),
120.9 (s), 124.7 (s), 125.6 (s), 127.11 (d), 127.16 (d), 128.0 (d), 130.2
(d), 133.0 (d), 134.2 (d), 134.4 (d), 134.6 (s), 135.5 (s), 135.6 (s),
138.0 (s), 144.0 (s), 154.5 (s), 157.2 (s), 177.5 (s) and 178.6 (s).
by recrystallization (CHCl3–hexane) to give 12a (80 mg, 41%) and
13a (16 mg, 8%).
1-Acetyl-4,9-dioxo-3-phenyl-4,9-dihydronaphtho[2,3-c]furan 12a.
Pale yellow needles; mp 159–160 ◦C (from CHCl3–hexane);
(Found: C, 75.82; H, 3.83. C20H12O4 requires C, 75.94; H,
3.82%); mmax(CHCl3)/cm−1 3010, 1675, 1530, 1490, 1390 and 1250;
dH(400 MHz; CDCl3; Me4Si) 2.89 (3 H, s, CH3), 7.49–7.58 (3 H,
m, ArH), 7.74–7.84 (2 H, m, ArH), 8.24–8.33 (2 H, m, ArH) and
8.41–8.49 (2 H, m, ArH); dC(100.6 MHz; CDCl3; Me4Si) 29.5 (q),
118.3 (s), 124.7 (s), 127.4 (d), 127.5 (d), 128.6 (2 × d), 128.9 (2 ×
d), 132.0 (d), 134.0 (d), 134.4 (d), 134.8 (s), 135.1 (s), 148.9 (s),
158.7 (s), 178.9 (s), 179.2 (s) and 187.3 (s).
1-Bromo-12-hydroxy-6,11-dioxo-6,11-dihydronaphthacene-5-
◦
carboxylic acid ethyl ester 4g. Orange crystals; mp 246–247 C
(from CHCl3–hexane); mmax(CHCl3)/cm−1 3420, 1715, 1670, 1560,
1250 cm−1; dH (400 MHz; CDCl3; Me4Si) 1.49 (3 H, t, J 7.1, CH3),
4.66 (2 H, q, J 7.1, OCH2), 7.54 (1 H, t, J 7.8, ArH), 7.81–7.89
(3 H, m, ArH), 8.03 (1 H, d, J 7.8, ArH), 8.30–8.35 (1 H, m, ArH),
8.40–8.45 (1 H, m, ArH) and 16.05 (1 H, s, OH); dC(100.6 MHz;
CDCl3; Me4Si) 14.1 (q), 62.4 (t), 109.0 (s), 120.9 (s), 125.3 (s), 125.5
(s), 127.0 (d), 127.20 (d), 127.27 (s), 127.8 (d), 131.7 (d), 133.5 (s),
133.8 (s), 134.6 (d), 134.8 (d), 136.0 (s), 137.0 (d), 166.0 (s), 169.0
(s), 181.5 (s) and 187.8 (s); m/z (EI) 423.9950 (M+. C21H13BrO5
requires 423.9946), 381 (100%), 379 (99), 354 (36), 352 (38), 346
(16), 325 (21) and 323 (19).
1-Acetyl-3-(4-methylphenyl)-4,9-dioxo-4,9-dihydronaphtho[2,3-c]-
furan 12b. Yellow needles; mp 183–184 ◦C (from CHCl3–
hexane); (Found: C, 76.08; H, 4.26. C21H14O4 requires C, 76.35; H,
4.27%); mmax(CHCl3)/cm−1 3015, 1680, 1495, 1390, 1270 and 1250;
dH(400 MHz; CDCl3; Me4Si) 2.45 (3 H, s, CH3), 2.89 (3 H, s, CH3),
7.34 (2 H, d, J 8.2, ArH), 7.75–7.84 (2 H, m, ArH), 8.26–8.34
(2 H, m, ArH) and 8.37 (2 H, d, J 8.2, ArH); dC(100.6 MHz;
CDCl3; Me4Si) 21.8 (q), 29.5 (q), 117.9 (s), 124.75 (s), 124.82 (s),
127.44 (d), 127.52 (d), 128.9 (2 × d), 129.3 (2 × d), 134.0 (d),
134.4 (d), 134.8 (s), 135.2 (s), 142.9 (s), 148.6 (s), 159.2 (s), 178.9
(s), 179.3 (s) and 187.4 (s).
1-Chloro-12-hydroxy-6,11-dioxo-6,11-dihydronaphthacene-5-
◦
carboxylic acid ethyl ester 4h. Orange crystals; mp 250–251 C
(from CHCl3–hexane); mmax(CHCl3)/cm−1 2980, 1715, 1665, 1390,
1280 and 1250; dH(400 MHz; CDCl3; Me4Si) 1.49 (3 H, t, J 7.2,
CH3), 4.66 (2 H, q, J 7.2, OCH2), 7.64 (1 H, t, J 8.0, ArH), 7.75
(1 H, d, J 8.0, ArH), 7.79 (1 H, d, J 8.0, ArH), 7.80–7.89 (2 H,
m, ArH), 8.27–8.34 (1 H, m, ArH), 8.37–8.44 (1 H, m, ArH) and
16.01 (1 H, s, OH); dC(100.6 MHz; CDCl3; Me4Si) 14.1 (q), 62.4
(t), 109.1 (s), 124.6 (s), 125.3 (s), 126.4 (d), 127.17 (d), 127.25 (s),
127.8 (d), 131.5 (d), 132.9 (d), 133.4 (s), 133.8 (s), 134.2 (s), 134.6
(d), 134.8 (d), 135.9 (s), 166.3 (s), 169.0 (s), 181.4 (s) and 187.8
(s); m/z (EI) 380.0453 (M+. C21H13ClO5 requires 380.0452), 345
(16%), 335 (100), 308 (16), 223 (18) and 187 (26).
1-Acetyl-3-(4-bromophenyl)-4,9-dioxo-4,9-dihydronaphtho[2,3-c]-
furan 12c. Pale orange powder; mp 200–201 C (from CHCl3–
◦
hexane); (Found: C, 60.49; H, 2.81. C20H11BrO4 requires C, 60.78;
H, 2.81%); mmax(CHCl3)/cm−1 2925, 1675, 1595, 1480 and 1265;
dH(400 MHz; CDCl3; Me4Si) 2.91 (3 H, s, CH3), 7.69 (2 H, d, J
8.7, ArH), 7.80–7.87 (2 H, m, ArH), 8.28–8.35 (2 H, m, ArH) and
8.39 (2 H, d, J 8.7, ArH); dC(100.6 MHz; CDCl3; Me4Si) 29.6 (q),
118.7 (s), 124.8 (s), 126.4 (s), 126.9 (s), 127.6 (d), 127.7 (d), 130.3
(2 × d), 132.0 (2 × d), 134.3 (d), 134.6 (d), 134.8 (s), 135.0 (s),
149.0 (s), 157.6 (s), 179.0 (s), 179.1 (s) and 187.4 (s).
1-Acetyl-3-(4-chlorophenyl)-4,9-dioxo-4,9-dihydronaphtho[2,3-c]-
furan 12d. Yellow needles; mp 207–208 ◦C (from CHCl3–
hexane); (Found: C, 68.31; H, 3.22. C20H11ClO4 requires C, 68.49;
H, 3.16%); mmax(CHCl3)/cm−1 3030, 1680, 1485, 1270 and 1250;
dH(400 MHz; CDCl3; Me4Si) 2.90 (3 H, s, CH3), 7.52 (2 H, d, J
8.6, ArH), 7.78–7.86 (2 H, m, ArH), 8.27–8.33 (2 H, m, ArH) and
8.46 (2 H, d, J 8.6, ArH); dC(100.6 MHz; CDCl3; Me4Si) 29.6 (q),
118.6 (s), 124.7 (s), 125.9 (s), 127.5 (d), 127.6 (d), 129.0 (2 × d),
130.2 (2 × d), 134.2 (d), 134.5 (d), 134.8 (s), 135.0 (s), 138.3 (s),
148.9 (s), 157.5 (s), 179.0 (s), 179.1 (s) and 187.3 (s).
1,3-Dichloro-12-hydroxy-6,11-dioxo-6,11-dihydronaphthacene-
5-carboxylic acid ethyl ester 4i. Orange crystals; mp 214–215 ◦C
(from CHCl3–hexane); mmax(CHCl3)/cm−1 3015, 1730, 1595, 1565
and 1250; dH(400 MHz; CDCl3; Me4Si) 1.49 (3 H, t, J 7.2, CH3),
4.67 (2 H, q, J 7.2, OCH2), 7.72 (1 H, d, J 2.0, ArH), 7.74 (1 H, d,
J 2.0, ArH), 7.81–7.90 (2 H, m, ArH), 8.28–8.34 (1 H, m, ArH),
8.38–8.44 (1 H, m, ArH) and 15.96 (1 H, s, OH); dC(100.6 MHz;
CDCl3; Me4Si) 14.0 (q), 62.6 (t), 109.3 (s), 122.9 (s), 125.4 (d), 126.1
(s), 126.4 (s), 127.2 (d), 127.8 (d), 132.8 (d), 133.3 (s), 133.7 (s),
134.8 (d), 135.0 (d), 135.3 (s), 136.3 (s), 137.6 (s), 166.1 (s), 168.5
(s), 181.3 (s) and 187.8 (s); m/z (EI) 414.0062 (M+. C21H12Cl2O5
requires 414.0062), 369 (62%), 344 (26), 335 (10), 315 (24) and 285
(100).
1-Acetyl-3-(2-methylphenyl)-4,9-dioxo-4,9-dihydronaphtho[2,3-c]-
furan 12e. Pale yellow needles; mp 179–180 ◦C (from CHCl3–
hexane); (Found: C, 76.30; H, 4.27. C21H14O4 requires C, 76.35;
H, 4.27%); mmax(CHCl3)/cm−1 3020, 1680, 1595, 1540, 1400 and
1250; dH(400 MHz; CDCl3; Me4Si) 2.41 (3 H, s, CH3), 2.88 (3 H,
s, CH3), 7.31–7.39 (2 H, m, ArH), 7.47 (1 H, t, J 7.5, ArH), 7.68
(1 H, d, J 7.5, ArH), 7.76–7.86 (2 H, m, ArH), 8.21–8.28 (1 H,
m, ArH) and 8.30–8.37 (1 H, m, ArH); dC(100.6 MHz; CDCl3;
Me4Si) 20.3 (q), 29.4 (q), 119.6 (s), 123.8 (s), 125.6 (d), 127.11 (s),
127.18 (d), 127.8 (d), 130.8 (d), 130.9 (d), 131.3 (d), 134.2 (d),
134.4 (d), 134.8 (s), 135.3 (s), 138.5 (s), 149.5 (s), 159.7 (s), 178.8
(s), 179.1 (s) and 187.3 (s).
Typical experimental procedure for the reaction between
2-benzoyl-1,4-naphthoquinones and 1,3-diketones
A mixture of 2-benzoyl-1,4-naphthoquinone (1a) (162 mg, 0.62
mmol), 2,4-pentanedione (11a) (251 mg, 2.51 mmol) and man-
ganese(III) acetate (664 mg, 2.48 mmol) in acetic acid (10 cm3) was
heated at 70 ◦C for 30 min. After work-up as described above, the
crude product was purified by column chromatography over silica
gel (20 g) (eluting with 2 : 1 dichloromethane–hexane) followed
1100 | Org. Biomol. Chem., 2006, 4, 1097–1103
This journal is
The Royal Society of Chemistry 2006
©

View Article Online
1-Acetyl-3-(2,4-dimethylphenyl)-4,9-dioxo-4,9-dihydronaphtho-
[2,3-c]furan 12f. Yellow needles; mp 204–205 C (from CHCl3–
1-Isobutyryl-3-(4-methylphenyl)-4,9-dioxo-4,9-dihydronaphtho-
[2,3-c]furan 12k. Orange needles; mp 140–141 ◦C (from CHCl3–
hexane); (Found: C, 77.15; H, 5.09. C23H18O4 requires 77.08;
H, 5.06); mmax(CHCl3)/cm−1 2980, 1660, 1540, 1495 and 1315;
dH(300 MHz; CDCl3; Me4Si) 1.30 (6 H, d, J 6.8, 2 × CH3), 2.46
(3 H, s, CH3), 3.97 (1 H, septet, J 6.8, CH), 7.36 (2 H, d, J 8.1,
ArH), 7.74–7.86 (2 H, m, ArH), 8.27–8.35 (2 H, m, ArH) and 8.38
(2 H, d, J 8.1, ArH); dC(75.5 MHz; CDCl3; Me4Si) 18.5 (2 × q),
21.7 (q), 38.3 (d), 117.9 (s), 124.6 (s), 124.9 (s), 127.4 (d), 127.6(d),
128.8 (2 × d), 129.4 (2 × d), 134.0 (d), 134.3 (d), 135.0 (s), 135.2
(s), 142.7 (s), 148.6 (s), 159.0 (s), 179.1 (s), 179.2 (s) and 194.5 (s).
◦
hexane); (Found: C, 76.68; H, 4.68. C22H16O4 requires C, 76.73;
H, 4.68%); mmax(CHCl3)/cm−1 3010, 1680, 1595, 1540 and 1250;
dH(400 MHz; CDCl3; Me4Si) 2.38 (3 H, s, CH3), 2.42 (3 H, s,
CH3), 2.87 (3 H, s, CH3), 7.16 (1 H, d, J 7.9, ArH), 7.18 (1 H, s,
ArH), 7.60 (1 H, d, J 7.9, ArH), 7.76–7.85 (2 H, m, ArH), 8.22–
8.28 (1 H, m, ArH) and 8.31–8.36 (1 H, m, ArH); dC(100.6 MHz;
CDCl3; Me4Si) 20.3 (q), 21.5 (q), 29.4 (q), 119.3 (s), 123.9 (s), 124.2
(s), 126.4 (d), 127.2 (d), 127.8 (d), 130.9 (d), 131.6 (d), 134.1 (d),
134.4 (d), 134.9 (s), 135.4 (s), 138.4 (s), 141.8 (s), 149.3 (s), 160.1
(s), 178.8 (s), 179.2 (s) and 187.3 (s).
1-(4-bromophenyl)-3-isobutyryl-4,9-dioxo-4,9-dihydronaphtho-
[2,3-c]furan 12l. Orange needles; mp 177–178 ◦C (from CHCl3–
hexane); (Found: C, 62.40; H, 3.59. C22H15BrO4 requires C,
62.43; H, 3.57); mmax(CHCl3)/cm−1 1660, 1595, 1480 and 1385;
dH(300 MHz; CDCl3; Me4Si) 1.30 (6 H, d, J 6.8, 2 × CH3), 3.99
(1 H, septet, J 6.8, CH), 7.69 (2 H, d, J 8.4, ArH), 7.77–7.88 (2 H,
m, ArH), 8.28–8.34 (2 H, m, ArH) and 8.39 (2 H, d, J 8.4, ArH);
dC(100.6 MHz; CDCl3; Me4Si) 18.4 (2 × q), 38.4 (d), 118.7 (s),
124.5 (s), 126.5 (s), 126.7 (s), 127.5 (d), 127.7 (d), 130.2 (2 × d),
132.0 (2 × d), 134.2 (d), 134.5 (d), 134.9 (s), 135.0 (s), 149.1 (s),
157.4 (s), 179.0 (s), 179.1 (s) and 194.6 (s).
1-Acetyl-3-(2-bromophenyl)-4,9-dioxo-4,9-dihydronaphtho[2,3-c]-
furan 12g. Pale orange powder; mp 194–195 C (from CHCl3–
◦
hexane); (Found: C, 60.64; H, 2.78. C20H11BrO4 requires C, 60.78;
H, 2.81%); mmax(CHCl3)/cm−1 3010, 1680, 1595, 1400 and 1250;
dH(400 MHz; CDCl3; Me4Si) 2.89 (3 H, s, CH3), 7.44 (1 H, td,
J 7.4 and 1.6, ArH), 7.50 (1 H, td, J 7.4 and 1.6, ArH), 7.67
(1 H, dd, J 7.4 and 1.6, ArH), 7.76 (1 H, dd, J 7.4 and 1.6, ArH),
7.78–7.87 (2 H, m, ArH), 8.21–8.26 (1 H, m, ArH) and 8.32–8.37
(m, 1H, ArH); dC(125.6 MHz; CDCl3; Me4Si) 29.3 (q), 120.4 (s),
123.5 (s), 127.1 (2 × d), 127.9 (d), 129.1 (s), 132.4 (2 × d), 133.4
(d), 134.31 (d), 134.37 (d), 134.6 (s), 135.5 (s), 149.8 (s), 157.0 (s),
178.61 (s), 178.66 (s) and 187.2 (s).
1-Benzoyl-3-phenyl-4,9-dioxo-4,9-dihydronaphtho[2,3-c]furan
12m. Yellow needles; mp 196–197 ◦C (from CHCl3–hexane);
(Found: C, 79.08; H, 3.71. C25H14O4 requires C, 79.36; H, 3.73%);
mmax(CHCl3)/cm−1 3015, 1675, 1595, 1270 and 1250; dH(400 MHz;
CDCl3; Me4Si) 7.47–7.58 (5 H, m, ArH), 7.68 (1 H, t, J 7.6, ArH),
7.77 (1 H, td, J 7.4 and 1.3, ArH), 7.82 (1 H, td, J 7.4 and 1.3,
ArH), 8.01 (2 H, d, J 7.6, ArH), 8.22 (1 H, d, J 7.4, ArH), 8.36
(1 H, d, J 7.4, ArH) and 8.42–8.52 (2 H, m, ArH); dC(100.6 MHz;
CDCl3; Me4Si) 117.7 (s), 125.1 (s), 127.4 (d), 127.7 (d), 128.6 (2 ×
d), 128.7 (4 × d), 129.9 (2 × d), 131.8 (d), 134.0 (d), 134.2 (d),
134.3 (d), 134.7 (s), 135.6 (s), 136.1 (s), 149.4 (s), 158.5 (s), 178.5
(s), 179.0 (s) and 184.0 (s).
1-Acetyl-3-(2-chlorophenyl)-4,9-dioxo-4,9-dihydronaphtho[2,3-c]-
furan 12h. Pale yellow needles; mp 236–237 ◦C (from CHCl3–
hexane); (Found: C, 68.37; H, 3.12. C20H11ClO4 requires C, 68.49;
H, 3.16%); mmax(CHCl3)/cm−1 3030, 1685, 1580, 1540, 1400 and
1250; dH(400 MHz; CDCl3; Me4Si) 2.90 (3 H, s, CH3), 7.45 (1 H,
t, J 7.5, ArH), 7.48–7.61 (2 H, m, ArH), 7.71 (1 H, d, J 7.5, ArH),
7.76–7.87 (2 H, m, ArH), 8.25 (1 H, dd, J 6.5 and 1.8, ArH) and
8.35 (1 H, dd, J 6.5 and 1.8, ArH); dC(100.6 MHz; CDCl3; Me4Si)
29.3 (q), 120.6 (s), 123.6 (s), 126.6 (d), 127.0 (s), 127.2 (d), 127.9
(d), 130.2 (d), 132.2 (d), 132.4 (d), 134.33 (d), 134.42 (d), 134.44
(s), 134.6 (s), 135.4 (s), 149.9 (s), 155.9 (s), 178.6 (s), 178.7 (s) and
187.3 (s).
1-Benzoyl-3-(4-methylphenyl)-4,9-dioxo-4,9-dihydronaphtho-
[2,3-c]furan 12n. Yellow needles; mp 225–226 ◦C (from CHCl3–
hexane); (Found: C, 79.52; H, 4.19. C26H16O4 requires C, 79.58;
H, 4.11%); mmax(CHCl3)/cm−1 3015, 1680, 1595, 1500 and 1270;
dH(400 MHz, CDCl3; Me4Si) 2.45 (3 H, s, CH3), 7.35 (2 H, d, J
8.2, ArH), 7.53 (2 H, t, J 7.6, ArH), 7.68 (1 H, t, J 7.6, ArH),
7.76 (1 H, t, J 7.4, ArH), 7.81 (1 H, t, J 7.4, ArH), 8.01 (2 H, d,
J 7.6, ArH), 8.21 (1 H, d, J 7.4, ArH), 8.36 (1 H, d, J 7.4, ArH)
and 8.40 (2 H, d, J 8.2, ArH); dC(100.6 MHz, CDCl3; Me4Si) 21.7
(q), 117.2 (s), 125.0 (s), 125.2 (s), 127.4 (d), 127.6 (d), 128.6 (2 ×
d), 128.7 (2 × d), 129.4(2 × d), 129.9 (2 × d), 133.9 (d), 134.1 (d),
134.3 (d), 134.8 (s), 135.7 (s), 136.2 (s), 142.6 (s), 149.1 (s), 159.0
(s), 178.6 (s), 179.0 (s) and 184.0 (s).
1-Acetyl-3-(2,4-dichlorophenyl)-4,9-dioxo-4,9-dihydronaphtho-
◦
[2,3-c]furan 12i. Yellow needles; mp 191–192 C (from CHCl3–
hexane); (Found: C, 62.26; H, 2.56. C20H10Cl2O4 requires C,
62.36; H, 2.62%); mmax(CHCl3)/cm−1 3020, 1685, 1470, 1410, 1250;
dH(400 MHz; CDCl3; Me4Si) 2.89 (3 H, s, CH3), 7.44 (1 H, dd, J
8.5 and 1.6, ArH), 7.60 (1 H, d, J 1.6, ArH), 7.67 (1 H, d, J 8.5,
ArH), 7.77–7.89 (2 H, m, ArH), 8.24 (1H, dd, J 7.2 and 2.2, ArH)
and 8.35 (1 H, dd, J 7.2 and 2.2, ArH); dC(100.6 MHz; CDCl3;
Me4Si) 29.4 (q), 120.9 (s), 123.6 (s), 125.5 (s), 127.14 (d), 127.19
(d), 128.0 (d), 130.3 (d), 133.1 (d), 134.46 (d), 134.48 (d), 135.34 (s),
135.36 (s), 138.1 (s), 150.1 (s), 154.7 (s), 178.6 (2 × s) and 187.2 (s).
1-Isobutyryl-3-phenyl-4,9-dioxo-4,9-dihydronaphtho[2,3-c]furan
12j. Orange needles; mp 156–157 ◦C (from CHCl3–hexane);
(Found: C, 76.66; H, 4.67. C22H16O4 requires C, 76.73; H, 4.68%);
mmax(CHCl3)/cm−1 2980, 1660, 1530, 1485 and 1315; dH(300 MHz;
CDCl3; Me4Si) 1.31 (6 H, d, J 6.8, 2 × CH3), 3.98 (1 H, septet, J
6.8, CH), 7.53–7.61 (3 H, m, ArH), 7.78–7.86 (2 H, m, ArH), 8.29–
8.37 (2 H, m, ArH) and 8.43–8.51 (2 H, m, ArH); dC(125.7 MHz;
CDCl3; Me4Si) 18.4 (2 × q), 38.3 (d), 118.3 (s), 124.6 (s), 127.4 (d),
127.6 (d), 128.6 (2 × d), 128.8 (2 × d), 131.9 (d), 134.1 (d), 134.3 (d),
135.0 (s), 135.1 (s), 149.0 (s), 158.6 (s), 179.1 (2 × s) and 194.5 (s).
1-Benzoyl-3-(4-bromophenyl)-4,9-dioxo-4,9-dihydronaphtho-
[2,3-c]furan 12o. Yellow powder; mp 215–216 ◦C (from CHCl3–
hexane); (Found: C, 65.55; H, 2.81. C25H13BrO4 requires C, 65.66;
H, 2.87%); mmax(CHCl3)/cm−1 3015, 1675, 1595, 1270 and 1250;
dH(400 MHz; CDCl3; Me4Si) 7.54 (2 H, t, J 7.7, ArH), 7.64–7.71
(3 H, m, ArH), 7.74–7.85 (2 H, m, ArH), 7.99 (2 H, d, J 7.7, ArH),
8.21 (1 H, d, J 7.6, ArH), 8.35 (1 H, d, J 7.6, ArH) and 8.40 (2 H,
d, J 8.2, ArH); dC(125.6 MHz; CDCl3; Me4Si) 118.0 (s), 125.1 (s),
126.6 (2 × s), 127.5 (d), 127.7 (d), 128.7 (2 × d), 129.87 (2 × d),
129.93 (2 × d), 132.0 (2 × d), 134.1 (d), 134.3 (d), 134.4 (d), 134.7
This journal is
The Royal Society of Chemistry 2006
Org. Biomol. Chem., 2006, 4, 1097–1103 | 1101
©

View Article Online
(s), 135.5 (s), 136.0 (s), 149.5 (s), 157.3 (s), 178.4 (s), 179.0 (s) and
183.9 (s).
H, 3.17%); mmax(CHCl3)/cm−1 3015, 1680, 1595, 1270 and 1250;
dH(400 MHz; CDCl3; Me4Si) 7.44 (1 H, td, J 7.6 and 1.4, ArH),
7.47–7.60 (4 H, m, ArH), 7.67 (1 H, t, J 7.6, ArH), 7.75 (1 H, dd,
J 7.6 and 1.4, ArH), 7.76–7.83 (2 H, m, ArH), 8.04 (2 H, dd, J
7.6 and 1.4, ArH) and 8.21–8.30 (2 H, m, ArH); dC(100.6 MHz;
CDCl3; Me4Si) 120.0 (s), 124.2 (s), 126.6 (d), 127.1 (s), 127.3 (d),
127.8 (d), 128.6 (2 × d), 130.0 (2 × d), 130.3 (d), 132.3 (d), 132.5
(d), 134.19 (d), 134.21 (d), 134.25 (d), 134.31 (s), 135.0 (s), 135.3
(s), 135.8 (s), 150.6 (s), 155.4 (s), 178.1 (s), 178.7 (s) and 183.5 (s).
1-Benzoyl-3-(4-chlorophenyl)-4,9-dioxo-4,9-dihydr naphtho[2,3-c]-
furan 12p. Yellow needles; mp 208–209 ◦C (from CHCl3–
hexane); (Found: C, 72.71; H, 3.27. C25H13ClO4 requires C, 72.74;
H, 3.17%); mmax(CHCl3)/cm−1 3015, 1680, 1595, 1490, 1270 and
1250; dH(400 MHz; CDCl3; Me4Si) 7.50 (2 H, d, J 8.7, ArH), 7.54
(2 H, t, J 7.6, ArH), 7.69 (1 H, t, J 7.6, ArH), 7.76 (1 H, t, J 7.4,
ArH), 7.81 (1 H, t, J 7.4, ArH), 8.00 (2 H, d, J 7.6, ArH), 8.20
(1 H, d, J 7.4, ArH), 8.34 (1 H, d, J 7.4, ArH) and 8.47 (2 H, d,
J 8.7, ArH); dC(100.6 MHz; CDCl3; Me4Si) 117.9 (s), 125.0 (s),
126.1 (s), 127.4 (d), 127.7 (d), 128.7 (2 × d), 129.0 (2 × d), 129.81
(2 × d), 129.85 (2 × d), 134.1 (d), 134.3 (d), 134.4 (d), 134.6 (s),
135.4 (s), 136.0 (s), 138.0 (s), 149.4 (s), 157.3 (s), 178.4 (s), 179.0
(s) and 183.9 (s).
1-Benzoyl-3-(2,4-dichlorophenyl)-4,9-dihydro-4,9-dioxonaphtho-
[2,3-c]furan 12u. Yellow crystals; mp 179–180 ◦C (from CHCl3–
hexane); (Found: C, 66.98; H, 2.63. C25H12Cl2O4 requires C,
67.13; H, 2.70%); mmax(CHCl3)/cm−1 3015, 1680, 1585, 1270 and
1250; dH(400 MHz; CDCl3; Me4Si) 7.43 (1 H, dd, J 8.4 and 2.1,
ArH), 7.53 (2 H, t, J 7.7, ArH), 7.59 (1 H, d, J 2.1, ArH), 7.68
(1 H, t, J 7.7, ArH), 7.71 (1 H, d, J 8.4, ArH), 7.73–7.83 (2 H,
m, ArH), 8.02 (2 H, d, J 7.7, ArH) and 8.21–8.28 (2 H, m, ArH);
dC(100.6 MHz; CDCl3; Me4Si) 120.2 (s), 124.1 (s), 125.5 (s), 127.2
(d), 127.3 (d), 127.8 (d), 128.7 (2 × d), 130.0 (2 × d), 130.3 (d),
133.3 (d), 134.30 (d), 134.34 (2 × d), 134.9 (s), 135.2 (s), 135.3
(s), 135.8 (s), 138.0 (s), 150.7 (s), 154.2 (s), 177.9 (s), 178.7 (s) and
183.5 (s).
1-Benzoyl-3-(2-methylphenyl)-4,9-dioxo-4,9-dihydronaphtho-
[2,3-c]furan 12q. Yellow crystals; mp 175–176 ◦C (from CHCl3–
hexane); (Found: C, 79.50; H, 4.15. C26H16O4 requires C, 79.58;
H, 4.11%); mmax(CHCl3)/cm−1 3035, 1675, 1590, 1270 and 1250;
dH(400 MHz; CDCl3; Me4Si) 2.42 (3 H, s, CH3), 7.34 (1 H, t, J 6.5,
ArH), 7.35 (1 H, d, J 6.5, ArH), 7.45 (1 H, t, J 7.6, ArH), 7.51
(2 H, t, J 7.6, ArH), 7.65 (1 H, td, J 6.5 and 1.0, ArH), 7.70–7.79
(3 H, m, ArH), 7.99 (2 H, dd, J 7.6 and 1.1, ArH) and 8.19–8.28
(2 H, m, ArH); dC(100.6 MHz; CDCl3; Me4Si) 20.4 (q), 118.8 (s),
124.2 (s), 125.5 (d), 127.1 (s), 127.2 (d), 127.5 (d), 128.5 (2 × d),
129.8 (2 × d), 130.7 (d), 130.9 (d), 131.2 (d), 133.98 (d), 134.02
(d), 134.2 (d), 135.09 (s), 135.11 (s), 136.0 (s), 138.4 (s), 149.9 (s),
159.2 (s), 178.3 (s), 178.7 (s) and 183.8 (s).
6-Acetyl-11-hydroxy-5,12-dioxo-5,12-dihydronaphthacene 13a.
◦
Orange needles; mp 249–250 C (from CHCl3–hexane); (Found:
C, 75.79; H, 3.77. C20H12O4 requires C, 75.94; H, 3.82%);
mmax(CHCl3)/cm−1 3010, 1670, 1595, 1430, 1295 and 1260;
dH(400 MHz; CDCl3; Me4Si) 2.70 (3 H, s, CH3), 7.71–7.89 (5 H,
m, ArH), 8.27–8.34 (1 H, m, ArH), 8.35–8.43 (1 H, m, ArH),
8.61 (1 H, dd, J 7.1 and 1.7, ArH) and 14.82 (1 H, s, OH);
dC(75.5 MHz; CDCl3; Me4Si) 31.9 (q), 108.4 (s), 124.1 (s), 125.3
(d), 126.8 (d), 127.1 (d), 127.8 (d), 129.4 (d), 132.0 (d), 132.4 (s),
133.6 (s), 133.9 (s), 134.6 (d), 134.7 (d), 136.5 (s), 164.0 (s), 182.7
(s), 187.9 (s) and 205.2 (s).
1-Benzoyl-3-(2,4-dimethylphenyl)-4,9-dioxo-4,9-dihydronaphtho-
[2,3-c]furan 12r. Yellow crystals; mp 167–168 ◦C (from CHCl3–
hexane); (Found: C, 79.67; H, 4.52. C27H18O4 requires C, 79.79;
H, 4.46%); mmax(CHCl3)/cm−1 3015, 1660, 1585, 1490 and 1270;
dH(400 MHz; CDCl3; Me4Si) 2.39 (3 H, s, CH3), 2.41 (3 H, s,
CH3), 7.165 (1 H, d, J 6.2, ArH), 7.173 (1 H, s, ArH), 7.51 (2 H, t,
J 7.8, ArH), 7.60–7.69 (2 H, m, ArH), 7.71–7.81 (2 H, m, ArH),
8.00 (2 H, dd, J 7.8 and 1.1, ArH) and 8.20–8.29 (2 H, m, ArH);
dC(100.6 MHz; CDCl3; Me4Si) 20.4 (q), 21.5 (q), 118.6 (s), 124.3
(s), 124.4 (s), 126.4 (d), 127.3 (d), 127.6 (d), 128.6 (2 × d), 129.9
(2 × d), 131.0 (d), 131.6 (d), 133.97 (d), 134.03 (d), 134.2 (d),
135.2 (s), 135.3 (s), 136.1 (s), 138.3 (s), 141.7 (s), 149.7 (s), 159.7
(s), 178.4 (s), 178.8 (s) and 183.9 (s).
6-Acetyl-11-hydroxy-8-methyl-5,12-dioxo-5,12-dihydronaphtha-
cene 13b. Orange needles; mp 294–295 ◦C (from CHCl3–hexane);
(Found: C, 76.23; H, 4.27. C21H14O4 requires C, 76.35; H,
4.27%) mmax(KBr)/cm−1 3405, 2915, 1700, 1660, 1590 and 1255;
dH(400 MHz; CDCl3; Me4Si) 2.56 (3 H, s, CH3), 2.69 (3 H, s,
CH3), 7.54–7.59 (2 H, m, ArH), 7.79–7.88 (2 H, m, ArH), 8.28–
8.33 (1 H, m, ArH), 8.36–8.41 (1 H, m, ArH), 8.49 (1 H, d, J
8.9, ArH) and 14.81 (1 H, s, OH); dC(100.6 MHz; CDCl3; Me4Si)
22.2 (q), 32.0 (q), 107.9 (s), 125.2 (d), 125.8 (s), 126.1 (d), 127.0
(d), 127.8 (d), 131.4 (d), 132.7 (s), 133.7 (s), 133.9 (s), 134.55 (d),
134.59 (d), 136.1 (s), 143.1 (s), 164.1 (s), 182.8 (s), 187.7 (s) and
205.6 (s).
1-Benzoyl-3-(2-bromophenyl)-4,9-dioxo-4,9-dihydronaphtho-
[2,3-c]furan 12s. Yellow crystals; mp 208–209 ◦C; (from CHCl3–
hexane); (Found: C, 65.60; H, 2.81. C25H13BrO4 requires C, 65.66;
H, 2.87%); mmax(CHCl3)/cm−1 3015, 1680, 1600, 1270 and 1250;
dH(400 MHz; CDCl3; Me4Si) 7.43 (1 H, td, J 7.6 and 1.6, ArH),
7.29–7.51 (3 H, m, ArH), 7.67 (1 H, t, J 7.3, ArH), 7.69 (1 H,
dd, J 7.6 and 1.6, ArH), 7.54–7.77 (3 H, m, ArH), 8.05 (2 H, d,
J 7.3, ArH) and 8.20–8.31 (2 H, m, ArH); dC(100.6 MHz; CDCl3;
Me4Si) 119.8 (s), 123.4 (s), 124.1 (s), 127.21 (d), 127.26 (d), 127.8
(d), 128.6 (2 × d), 129.2 (s), 130.0 (2 × d), 132.4 (d), 132.6 (d),
133.4 (d), 134.18 (d), 134.24 (2 × d), 135.0 (s), 135.3 (s), 135.8 (s),
150.4 (s), 156.5 (s), 178.0 (s), 178.7 (s) and 183.5 (s).
11-Acetyl-6-hydroxy-7-methyl-5,12-dioxo-5,12-dihydronaphtha-
cene 13c. Orange needles; mp 233–234 ◦C (from CHCl3–
hexane); (Found: C, 76.35; H, 4.25.C21H14O4 requires C, 76.35; H,
4.27); mmax(CHCl3)/cm−1 3395, 2930, 1700, 1670, 1595 and 1580;
dH(400 MHz; CDCl3; Me4Si) 2.68 (3 H, s, CH3), 3.05 (3 H, s, CH3),
7.43–7.50 (1 H, m, ArH), 7.57–7.65 (2 H, m, ArH), 7.77–7.87
(2 H, m, ArH), 8.28 (1 H, dd, J 7.0 and 1.7, ArH), 8.39 (1 H, dd, J
7.3 and 1.7, ArH) and 15.83 (1 H, s, OH); dC(100.6 MHz; CDCl3;
Me4Si) 25.3 (q), 31.9 (q), 108.5 (s), 123.7 (s), 125.2 (d), 127.0 (d),
127.2 (s), 127.6 (d), 131.6 (d), 132.8 (d), 133.7 (s), 133.8 (s), 134.1
(s), 134.49 (d), 134.54 (d), 137.0 (s), 140.9 (s), 168.3 (s), 182.6 (s),
187.6 (s) and 205.8 (s).
1-Benzoyl-3-(2-chlorophenyl)-4,9-dioxo-4,9-dihydronaphtho-
[2,3-c]furan 12t. Yellow crystals; mp 201–202 ◦C (from CHCl3–
hexane); (Found: C, 72.70; H, 3.13. C25H13ClO4 requires C, 72.74;
1102 | Org. Biomol. Chem., 2006, 4, 1097–1103
This journal is
The Royal Society of Chemistry 2006
©

View Article Online
11-Acetyl-6-hydroxy-7,9-dimethyl-5,12-dioxo-5,12-dihydro-
naphthacene 13d. Orange needles; mp 276–277 ◦C (from CHCl3–
hexane); mmax(CHCl3)/cm−1 3425, 2925, 1695, 1595, 1580 and 1270;
dH(400 MHz; CDCl3; Me4Si) 2.48 (3 H, s, CH3), 2.67 (3 H, s, CH3),
3.01 (3 H, s, CH3), 7.31 (1 H, s, ArH), 7.39 (1 H, s, ArH), 7.76–7.87
(2 H, m, ArH), 8.28 (1 H, dd, J 7.5 and 1.6, ArH), 8.39 (1 H, dd, J
7.5 and 1.6, ArH) and 15.83 (1 H, s, OH); dC (100.6 MHz; CDCl3;
Me4Si) 21.9 (q), 25.1 (q), 32.0 (q), 108.1 (s), 123.8 (s), 124.7 (d),
125.1 (s), 127.0 (d), 127.6 (d), 133.7 (s), 133.9 (s), 134.3 (d), 134.45
(s), 134.49 (d), 134.8 (d), 136.6 (s), 140.6 (s), 142.5 (s), 168.3 (s),
182.7 (s), 187.3 (s) and 206.1 (s); m/z (EI) 344.1053 (M+. C22H16O4
requires 344.1048), 329 (100%), 318 (4), 245 (5), 215 (16) and 202
(18).
Wan, B. O. Buckman and B. M. Foxman, J. Org. Chem., 1991, 56,
328–334.
5 (a) A. Citterio, R. Sebastiano and A. Marion, J. Org. Chem., 1991, 56,
5328–5335; (b) A. Citterio, R. Sebastiano and M. Nicolini, Tetrahedron,
1993, 49, 7743–7760; (c) Y.-L. Wu, C.-P. Chuang and P.-Y. Lin,
Tetrahedron, 2000, 56, 6209–6217; (d) Y.-J. Liao, Y.-L. Wu and C.-P.
Chuang, Tetrahedron, 2003, 59, 3511–3520; (e) Y.-L. Wu and C.-P.
Chuang, Tetrahedron, 2004, 60, 1841–1847.
6 (a) M.-C. Jiang and C.-P. Chuang, J. Org. Chem., 2000, 65, 5409–5412;
(b) Y.-L. Wu and C.-P. Chuang, Tetrahedron Lett., 2001, 42, 1717–1719;
(c) Y.-L. Wu, C.-P. Chuang and P.-Y. Lin, Tetrahedron, 2001, 57, 5543–
5549; (d) A.-I. Tsai, Y.-L. Wu and C.-P. Chuang, Tetrahedron, 2001, 57,
7829–7837; (e) C.-C. Tseng, Y.-L. Wu and C.-P. Chuang, Tetrahedron,
2002, 58, 7625–7633; (f) C.-M. Tseng, Y.-L. Wu and C.-P. Chuang,
Tetrahedron, 2004, 60, 12249–12260; (g) H.-L. Chen, C.-Y. Lin, Y.-C.
Cheng, A.-I. Tsai and C.-P. Chuang, Synthesis, 2005, 977–985.
7 (a) N. Jacobsen and K. Torsell, Acta Chem. Scand., 1973, 27, 3211–
3216; (b) P. M. Brown and R. H. Thomson, J. Chem. Soc., Perkin Trans.
1, 1976, 997–1000; (c) A. Citterio, A. Arnoldi and F. Minisci, J. Org.
Chem., 1979, 44, 2674; (d) A. Citterio, E. Vismara and R. Bernardi,
J. Chem. Res., Synop., 1983, 88–89; (e) G. A. Kraus and A. Melekhov,
Tetrahedron Lett., 1998, 39, 3957–3960; (f) D. R. Williams and M. P.
Clark, Tetrahedron Lett., 1998, 39, 7629–7632; (g) T. Ling, E. Poupon,
E. J. Rueden, S. H. Kim and E. A. Theodorakis, J. Am. Chem. Soc.,
2002, 124, 12261–12267.
8 Considering the electron-withdrawing effect of the benzoyl group,
6a may also be produced by the nucleophilic addition of ethyl
butyrylacetate (2a) to the quinone ring of 1a followed by manganese(III)
acetate oxidation.
9 Similar retro-Claisen condensation reactions have been reported. See:
(a) E. F. Pratt, R. G. Rice and R. W. Luckenbaugh, J. Am. Chem. Soc.,
1957, 79, 1212–1217; (b) A. Citterio, M. Fochi, A. Marion, A. Mele, R.
Sebastiano and M. Delcanale, Heterocycles, 1998, 48, 1993–2002. See
also ref. 6a,d,f .
10 The formation of dihydrofurans by oxidative cycloaddition of 1,3-
dicarbonyl compounds to alkenes mediated by metal salts has been
reported. See: (a) E. I. Heiba and R. M. Dessau, J. Org. Chem., 1974,
39, 3456–3457; (b) E. Baciocchi and R. Ruzziconi, Synth. Commun.,
1988, 18, 1841–1846; (c) V. Nair, J. Mathew and K. V. Radhakrishnan,
J. Chem. Soc., Perkin Trans. 1, 1996, 1487–1492; (d) V. Nair, J. Mathew
and L. G. Nair, Synth. Commun., 1996, 26, 4531–4538; (e) S. C. Roy
and P. K. Mandal, Tetrahedron, 1996, 52, 2193–2198; (f) Y. R. Lee, B. S.
Kim and D. H. Kim, Tetrahedron, 2000, 56, 8845–8853; (g) Y. Zhang,
A. J. Raines and R. A. Flowers, II, Org. Lett., 2003, 5, 2363–2365.
11 (a) P. Jacob, III, P. S. Callery, A. T. Shulgin and N. Castagnoli, Jr,
J. Org. Chem., 1976, 41, 3627–3629; (b) W. Williams, X. Sun and D.
Jebaratnam, J. Org. Chem., 1997, 62, 4364–4369.
Acknowledgements
We are grateful to the National Science Council of the ROC for
financial support (Grant No. NSC-93-2113-M-006-004).
References
1 (a) W. P. Neumann, Synthesis, 1987, 665–682; (b) D. P. Curran,
Synthesis, 1988, 417–439 and 489-513; (c) B. Giese, B. Kopping,
T. Gobel, J. Dickhaut, G. Thoma, K. J. Kulicke and F. Trach, in
Organic Reactions, John Wiley & Sons, New York, 1996, vol. 48, ch. 2,
pp. 301–855; (d) W. R. Bowman, C. F. Bridge and P. Brookes, J. Chem.
Soc., Perkin Trans. 1, 2000, 1–14; (e) W. Zheng, Tetrahedron, 2001, 57,
7237–7262.
2 (a) G. G. Melikyan, Synthesis, 1993, 833–850; (b) J. Iqbal, B. Bhatia
and N. K. Nayyar, Chem. Rev., 1994, 94, 519–564; (c) B. B. Snider,
Chem. Rev., 1996, 96, 339–363; (d) V. Nair, S. B. Panicker, L. G. Nair,
T. G. George and A. Augustine, Synlett, 2003, 156–165; (e) V. Nair, L.
Balagopal, R. Rajan and J. Mathew, Acc. Chem. Res., 2004, 37, 21–
30.
3 (a) H. Ulrich and R. Richter, in Methods of Organic Chemistry
(Houben–Weyl), ed. E. Muller, Georg Thieme Verlag, Stuttgart,
Germany, 1977, vol. VII/3a, part 1; (b) The Chemistry of Functional
Groups: The Chemistry of The Quinoid Compounds, ed. S. Patai
and Z. Rappoport, Wiley, New York, 1988; (c) R. H. Thomson,
Naturally Occurring Quinones IV: Recent Advances, Chapman and
Hall, London, 1997; (d) M. J. Piggott, Tetrahedron, 2005, 61, 9929–
9954.
12 (a) B. S. Joshi, Q. Jiang, T. Rho and S. W. Pettetier, J. Org. Chem., 1994,
59, 8220–8232.
4 (a) H. Oumar-Mahamat, C. Moustrou, J.-M. Surzur and M. P.
Berstrand, J. Org. Chem., 1989, 54, 5684–5688; (b) B. B. Snider, B. Y. F.
This journal is
The Royal Society of Chemistry 2006
Org. Biomol. Chem., 2006, 4, 1097–1103 | 1103
©