Facile synthesis of 2-amino-1,4-naphthoquinones catalyzed by molecular iodine under ultrasonic irradiation

Article abstract of DOI:10.1080/00397910701866254

The conjugate addition reactions of amines with 1,4-naphthoquinone were catalyzed efficiently by molecular iodine under ultrasonic irradiation to afford 2-amino-1,4-naphthoquinones in moderate to excellent yields. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910701866254

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Facile Synthesis of
2‐Amino‐1,4‐naphthoquinones catalyzed by
Molecular Iodine under Ultrasonic Irradiation
Bing Liu a & Shun‐Jun Ji a
a Key Laboratory of Organic Synthesis of Jiangsu Province, College of
Chemistry and Chemical Engineering, Suzhou (Soochow) University, Suzhou,
People's Republic of China
Available online: 17 Apr 2008
To cite this article: Bing Liu & Shun‐Jun Ji (2008): Facile Synthesis of 2‐Amino‐1,4‐naphthoquinones catalyzed
by Molecular Iodine under Ultrasonic Irradiation, Synthetic Communications: An International Journal for
Rapid Communication of Synthetic Organic Chemistry, 38:8, 1201-1211
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Synthetic Communicationsw, 38: 1201–1211, 2008
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910701866254
Facile Synthesis of 2-Amino-1,4-
naphthoquinones catalyzed by Molecular
Iodine under Ultrasonic Irradiation
Bing Liu and Shun-Jun Ji
Key Laboratory of Organic Synthesis of Jiangsu Province, College of
Chemistry and Chemical Engineering, Suzhou University,Suzhou, China
Abstract: The conjugate addition reactions of amines with 1,4-naphthoquinone were
catalyzed efficiently by molecular iodine under ultrasonic irradiation to afford
2-amino-1,4-naphthoquinones in moderate to excellent yields.
Keywords: 2-Amino-1,4-naphthoquinones, molecular iodine, ultrasound
INTRODUCTION
During recent years, the synthesis of 2-amino-1,4-naphthoquinones has
attracted considerable attention, because they exhibit a wide spectrum of
pharmaceutical activities including antitumor and antimalarial properties.[1]
In particular, 2-amino-1,4-naphthoquinones have become increasingly
important as building blocks for the synthesis of many natural products and
other biologically active compounds.[2] Furthermore, they have been
reported as important dyes that can be used in industrial applications
widely.[3] Generally, two major synthetic strategies for their preparation
have been used: one approach involves the nucleophilic substitution of
halo-derivatives of naphthoquinones with amines leading to 2-amino-1,4-
naphthoquinones,[4] whereas the other involves the 1,4-type addition of
Received May 10, 2007
Address correspondence to Shun-Jun Ji, Key Laboratory of Organic Synthesis of
Jiangsu Province, College of Chemistry and Chemical Engineering, Suzhou
´
(Soochow) University, Renai Road, Suzhou Industrial Park, Suzhou 215123,
People’s Republic of China. E-mail: chemjsj@suda.edu.cn
1201

1202
B. Liu and S.-J. Ji
amines to naphthoquinones under acidic conditons.[5] However, many of these
procedures involved strong acidic conditions, many by-products, low yields of
products, and complex handling. For this reason, superior catalytic systems,
which are cheap, easy to access, and environmentally friendly, are desirable.
Scheme 1.
The development of efficient processes to construct organic molecules,
using metal-free catalysts, has been drawing much attention over the past
decades.[6] Recently, molecular iodine has attracted more and more attention
from synthetic organic chemists. Citterio’s[7a] group reported the use of
iodine for the reaction of naphthoquinone, and Ko’s[7b] group also reported
the Michael reaction of indole catalyzed by iodine. Recently, Togo and
Iida[7c] reviewed the application of iodine in the organic reaction. Because of
its unique catalytic properties, iodine has been extensively used for many
organic transformations to afford the corresponding products in excellent
yields with high selectivity.[8] However, the use of iodine as a catalyst in the
synthesis of 2-amino-1,4-naphthoquinones has not been reported. In addition,
a survey of literature shows that many organic reactions have recently been
accelerated by ultrasonic irradiation with mild reaction conditions, short
reaction times, and high yields.[9] In continuation of our work in the use of
molecular iodine and ultrasound,[10] herein we describe the remarkable
catalytic activity of iodine as a cheaper catalyst in ultrasound-accelerated 1,4-
type addition of amines to naphthoquinones,[11] which provides one of the
most efficient routes to 2-amino-1,4-naphthoquinones (Scheme 1).
RESULTS AND DISCUSSION
The reactions were first carried out using a 1:2 molar ratio of morpholine 1g
and 1,4-naphthoquinone 2 along with a catalytic amount of different acids
Scheme 2.

2-Amino-1,4-naphthoquinones
1203
Table 1. Lewis acid–mediated reaction of morpholine 1g with
1,4-napthoquinonea
Entry
Lewis acid
Time (min)
Yield (%)b
1
2
3
4
5
6
7
8
I2
30
30
86
65
64
75
73
74
67
0
c
I2
CAN
.
CeCl3 7H2O
.
Bi(NO3)3 5H2O
.
FeCl3 6H2O
30
40
40
60
PTSA
No catalyst
30
180
aAll reactions were carried out using a catalytic amount of Lewis
acid (10 mol%) at room temperature, unless others noted.
bIsolated yields.
cThe reaction was carried out by stirring instead of sonic
irradiation.
under ultrasonic irradiation at room temperature. After the reaction was
complete, the excess 1,4-naphthoquinone could be isolated by column chrom-
atography on silica gel. As shown in Table 1, the reaction proceeded
efficiently in the presence of iodine at room temperature, giving the
2-amino-1,4-naphthoquinones 3g in excellent yield (86%) in 30 min
(Table 1, entry 1). The yields are improved under ultrasound irradiation in
the same reaction time (Table 2, entries 1 and 2). Furthermore, the reaction
could also be carried out using other acids, such as ammonium cerium (IV)
.
.
.
nitrate (CAN), CeCl3 7H2O, Bi(NO3)3 5H2O, FeCl3 6H2O, and p-Tolue-
nesulphonic acid (PTSA) (Table 2, entries 3–7), but the yields swere
decreased (64–75%) and the reaction time was prolonged. Therefore,
iodine was the superior catalyst in this reaction (Scheme 2).
Prompted by this success, we extended the reaction of 1,4-naphthoqui-
none with a wide range of other amines under similar conditions at room temp-
erature (Scheme 1), furnishing the 2-amino-1,4-naphthoquinone compounds
in moderate to excellent yields (Table 2). Our findings reflected the wide
applicability and usefulness of this method. As shown in Table 2, we found
that the reaction of aromatic amines bearing electron-donating groups with
1,4-naphthoquinone can proceed effectively to provide the desired products
in excellent yields (74–84%, Table 2, entries 2–5). Even primary and
secondary aliphatic amines such as morpholine 1g, piperidine 1h, pyrrolidine
1i, and butan-1-amine 1j could also react with 1,4-naphthoquinone to afford
the desired products in moderate to excellent yields (55–86%, Table 2,
entries 7–10). However, the yield of diphenylamine 1k is low, presumably
because diphenylamine is more sterically hindered than other amines
(Table 2, entry 11).

Table 2. Reaction of amines with 1,4-napthoquinonea
Time
(min)
Yield
(%)b
Entry
1
R1R2NH
Product
Mp (8C)
1a
3a
75
68
192–193 (190–191[10a]
)
2
3
1b
1c
3b
3c
15
60
84
81
158–159 (160–161[10b]
)
200–201 (201[10c]
)
4
5
1d
1e
3d
3e
50
20
74
78
146–148 (148–149[10d]
)
156–158 (155–157[10c]
)

6
7
8
1f
1g
1h
3f
3g
3h
150
30
46
86
60
149–151
150–152 (153–154[10e]
30
79–81 (88[10f]
)
9
10
11
1i
1j
3i
3j
30
60
70
55
17
138–140 (158–160[10g]
115–117 (124–125[10h]
)
)
1k
3k
350
160–161 (162–164[10i]
)
aAll reactions were carried out using a catalytic amount of I2 (10 mol%) at room temperature, unless otherwise noted.
bIsolated yields.

1206
B. Liu and S.-J. Ji
Scheme 3.
As previously shown we give the likely mechanism for the reaction. First,
molecular iodine activates the carbonyl group of the 1,4-naphthoquinone to
give intermediate I and is followed by an amine attack to the unsaturated
position of intermediate I to give the initial addition product II. The initial
addition product II tautomerizes to the hydroquinone III, which subsequently
undergoes rapid oxidation with another equivalent of 1,4-naphthoquinone,
resulting in 2-amino-1,4-naphthoquinone IV (Scheme 3).
CONCLUSIONS
In conclusion, we have developed the first iodine-promoted protocol for the
synthesis of 2-amino-1,4-naphthoquinones under ultrasonic irradiation at
room temperature. The method employs cheap, nontoxic molecular iodine
as the catalyst and involves a simple manipulation in comparision with
current available methodologies. Efforts to extend the reaction system to
other amines are currently in progress.
EXPERIMENTAL
General
Melting points were recorded on an Electrothermal digital melting-point
1
apparatus and are uncorrected. H NMR (400 MHz) spectra were recorded
on a Varian Mercury spectrometer in CDCl3 IR spectra were obtained on a
Nicolet FT-IR500 spectrophotometer using KBr pellets. High-resolution
mass spectra (HRMS) were obtained using a GCT-TOF instrument. Ultrasou-
nic irradiation was performed in a KQ-250E ultrasonic cleaner with a
frequency of 40 KHz and a normal power of 250 W. The reaction flask was
located in the water bath of the ultrasonic cleaner.

2-Amino-1,4-naphthoquinones
1207
Representative Experimental Procedure
A mixture of morpholine 1g (0.044 g, 0.5 mmol), 1,4-napthoquinone 2
(0.158 g, 1 mmol), I2 (0.013 g, 0.05 mmol), and anhydrous EtOH (2 mL)
was irradiated under ultrasound in an open vessel at room temperature until
the disappearance of the starting material (30 min, checked by thin-layer
chromatography, TLC). The residue was washed by saturated Na2S2O4 and
extracted with CH2Cl2 (3 ꢀ 10 mL). The combined extracts were dried over
anhydrous Na2SO4 and concentrated in vacuo. The resulting product
was purified by column chromatography on silica gel to afford pure product 3g.
Data
2-(Phenylamino)-1,4-naphthoquinone (3a). Red solid; IR (KBr): n 3319,
1
1667, 1598, 1304, 718 cm21; H NMR (400 MHz, CDCl3): d 6.44 (s, 1H),
7.21–7.30 (m, 3H), 7.43 (t, J ¼ 7.8 Hz, 2H), 7.58 (s, 1H), 7.68 (t, J ¼ 7.4
Hz, 1H), 7.77 (t, J ¼ 7.6 Hz, 1H), 8.13 (t, J ¼ 7.8 Hz, 2H).
2-(Benzylamino)-1,4-naphthoquinone (3b). Yellow needle crystal; IR
1
(KBr): n 3335, 1683, 1598, 1258, 726 cm21; H NMR (400 MHz, CDCl3):
d 4.39 (d, J ¼ 5.2 Hz, 2H), 5.79 (s, 1H), 6.22 (s, 1H), 7.26–7.39 (m, 5H),
7.63 (t, J ¼ 7.4 Hz, 1H), 7.74 (t, J ¼ 7.4 Hz, 1H), 8.05–8.11 (m, 2H).
2-(p-Tolylamino)-1,4-naphthoquinone (3c). Red solid; IR (KBr): n 3326,
1
1667, 1605, 1297, 726 cm21; H NMR (400 MHz, CDCl3): d 2.37 (s, 3H),
6.36 (s, 1H), 7.16–7.24 (m, 4H), 7.51 (s, 1H), 7.67 (t, J ¼ 7.4 Hz, 1H),
7.76 (t, J ¼ 7.4 Hz, 1H), 8.12 (t, J ¼ 6.4 Hz, 2H). HRMS [found: m/z,
263.0970 (Mþ); calcd. for C17H13NO2: M, 263.0946].
2-(o-Tolylamino)naphthalene-1,4-naphthoquinone (3d). Yellow solid; IR
1
(KBr): n 3303, 1683, 1597, 1304, 726 cm21; H NMR (400 MHz, CDCl3):
d 2.30 (s, 3H), 5.98 (s, 1H), 7.19–7.33 (m, 5H), 7.67 (t, J ¼ 7.2 Hz, 1H),
7.76 (t, J ¼ 7.6 Hz, 1H), 8.13 (t, J ¼ 5.6 Hz, 2H).
2-(4-Methoxyphenylamino)-1,4-naphthoquinone (3e). Red needle crystal;
1
IR (KBr): n 3226, 2933, 1683, 1605, 1235, 726 cm21; H NMR (400 MHz,
CDCl3): d 3.84 (s, 3H), 6.24 (s, 1H), 6.95 (d, J ¼ 8.0 Hz, 2H), 7.20–7.27
(m, 2H), 7.45 (s, 1H) 7.67 (t, J ¼ 7.0 Hz, 1H), 7.76 (t, J ¼ 7.2 Hz, 1H),
8.11 (t, J¼ 6.2 Hz, 2H).
2-(2-Chlorophenylamino)-1,4-naphthoquinone (3f). Yellow solid; IR (KBr):
1
n 3311, 1675, 1590, 1297, 741 cm21; H NMR (400 MHz, CDCl3): d 6.40
(s, 1H), 7.17 (t, J ¼ 7.6 Hz, 1H), 7.35 (t, J ¼ 8.0 Hz, 1H), 7.50 (d, J ¼ 8.0

1208
B. Liu and S.-J. Ji
Hz, 2H), 7.70 (t, J ¼ 7.4 Hz, 1H), 7.77–7.82 (m, 2H), 8.11–8.17 (m, 2H);
HRMS [found: m/z, 283.0378 (Mþ); calcd. for C16H10ClNO2: M, 283.0345].
2-Morpholino-1,4-naphthoquinone (3g). Yellow solid; IR (KBr): n 2925,
1
1675, 1567, 1212, 787cm21; H NMR (400 MHz, CDCl3): d 3.50 (s, 4H),
3.88 (s, 4H), 6.03 (s, 1H), 7.65–7.73 (m, 2H), 8.01–8.06 (m, 2H). HRMS
[found: m/z, 243.0869 (Mþ); calcd. for C14H13NO3: M, 243.0895].
2-(Piperidin-1-yl)-1,4-naphthoquinone (3h). Red solid; IR (KBr): n 2964,
1
1675, 1559, 1297, 772 cm21; H NMR (400 MHz, CDCl3): d 1.72 (s, 6H),
3.50 (s, 4H), 6.03 (s, 1H), 7.61–7.74 (m, 2H), 7.98–8.09 (m, 2H). HRMS
[found: m/z, 241.1107 (Mþ); calcd. for C15H15NO2: M, 241.1103].
2-(Pyrrolidin-1-yl)-1,4-naphthoquinone (3i). Red solid; IR (KBr): n 2941,
1
1675, 1559, 1243, 780 cm21; H NMR (400 MHz, CDCl3): d 2.02 (s, 4H),
3.23 (s, 2H), 3.99 (s, 2H), 5.75 (s, 1H), 7.59–7.72 (m, 2H), 8.01–8.08
(m, 2H). HRMS [found: m/z, 227.0940 (Mþ); calcd. for C14H13NO2: M,
227.0946].
2-(Butylamino)-1,4-naphthoquinone (3j). Yellow solid; IR (KBr): n 3342,
1
1675, 1567, 1243, 726 cm21; H NMR (400 MHz, CDCl3): d 0.96–1.00
(m, 3H), 1.42–1.49 (m, 2H), 1.66–1.72 (m, 2H), 3.17–3.21 (m, 2H), 5.74
(s, 1H), 5.90 (s, 1H), 7.62 (t, J ¼ 7.6 Hz, 1H), 7.74 (t, J ¼ 7.4 Hz, 1H),
8.04–8.12 (m, 2H). HRMS [found: m/z, 229.1087 (Mþ); calcd. for
C14H15NO2: M, 229.1103].
2-(Diphenylamino)-1,4-naphthoquinone (3k). Blue solid; IR (KBr): n 2925,
1
1652, 1590, 1250, 756 cm21; H NMR (400 MHz, CDCl3): d 5.99 (s, 1H),
7.06–7.20 (m, 6H), 7.31–7.34 (m, 2H), 7.57 (d, J ¼ 7.6 Hz, 2H), 7.77
(d, J ¼ 8.0 Hz, 2H), 8.10–8.19 (m, 2H). HRMS [found: m/z, 325.1101
(Mþ); calcd. for C22H15NO2: M, 325.1103].
ACKNOWLEDGMENTS
The work was supported by the National Natural Science Foundation of China
(Nos. 20472062 and 20672079), the Natural Science Foundation of Jiangsu
Province (Nos. BK2004038 and BK2006048), the Key Laboratory of
Organic Synthesis of Jiangsu Province (No. S8109108), Nature Science Key
Basic Research of Jiangsu Province for Higher Education (Nos.
06KJA15007 and 05KJB150116), the Key Laboratory of Fine Petroleum
Chemistry of Jiangsu Province (No. KF0402), and a research grant from the
Innovation Project for Graduate Students of Jiangsu Province.

2-Amino-1,4-naphthoquinones
REFERENCES
1209
1. (a) Crosby, A. H.; Lutz, A. H. A study of an oxidative-amination method for the
synthesis of aminoquinones 1. J. Am. Chem. Soc. 1955, 78, 1233–1235;
(b) Lin, T.-S.; Xu, S.-P.; Zhu, L.-Y.; Cosby, L.; Sartonelli, A. Synthesis of 2,3-diazir-
idinyl-1,4-naphthoquinonyl sulfonate derivatives as potential antineoplastic agents.
J. Med. Chem. 1989, 32, 1467–1471; (c) Lin, T.-S.; Xu, S.-P.; Zhu, L.-Y.;
Divo, A.; Sartonelli, A. Synthesis and antimalarial activity of 2-aziridinyl- and 2,3-
bis(aziridinyl)-1,4-naphthoquinonyl sulfonate and acylate derivatives. J. Med.
Chem. 1991, 34, 1634–1639.
2. (a) Kita, Y.; Tohma, H.; Inagaki, M.; Hatanaka, K.; Yakura, T. Total synthesis of
discorhabdin C: a general aza spiro dienone formation from O-silylated phenol
derivatives using a hypervalent iodine reagent. J. Am. Chem. Soc. 1992, 114,
2175–2180; (b) Aristoff, P.; Johnson, P. Synthesis of CBI-PDE-I-dimer, the ben-
zannelated analog of CC-1065. J. Org. Chem. 1992, 57, 6234–6239.
3. Kikuchi, M.; Komatsu, K.; Nakano, M. The alkylamination of naphthazarin. Dyes
Pigments. 1990, 12 (2), 107–118.
4. (a) Nakazumi, H.; Kondo, K.; Kitao, T. Synthesis of 7,10-Disubstituted Benzo[b]-
phenazine-6,11-quinones synthesis. Synthesis 1982, 878; (b) Couladouros, E. A.;
Plyta, A. F.; Papageorgiou, V. P. General procedure for the efficient synthesis of
(Alkylamino)naphthoquinones. J. Org. Chem. 1996, 61, 3031–3033.
5. Akermark, B.; Oslob, J. D.; Heuschert, U. Catalytic oxidative aromatic cycliza-
tions with palladium. Tetrahedron Lett. 1995, 36, 1325–1326.
6. (a) Lu, X.; Zhang, C.; Xu, Z. Reactions of electron-deficient alkynes and allenes
under phosphine catalysis. Acc. Chem. Res. 2001, 34, 535–544; (b) Dalko, P. I.;
Moisan, L. In the golden age of organocatalysis. Angew. Chem., Int. Ed. 2004,
43, 5138–5175; (c) Fu, G.-C. Asymmetric catalysis with “Planar-Chiral” deriva-
tives of 4-(dimethylamino)pyridine. Acc. Chem. Res. 2004, 37, 542–547.
7. (a) Citterio, A.; Fochi, M.; Marion, A.; Mele, A.; Sebastiano, R.; Delcanale, M.
Synthesis of naphtho-2,3-bindolizine-6,11-dione derivatives by iodine oxidation
of 2-alkyl-1,4-naphthoquidones in the presence of substituted pyridines. Hetero-
cycles. 1998, 48 (10), 1993–2002; (b) Ko, S. K.; Lin, C. C.; Tu, Z. J.;
Wang, Y. F.; Wang, C. C.; Yao, C. F. CAN and iodine-catalyzed reaction of
indole or 1-methylindole with a,b-unsaturated ketone or aldehyde. Tetrahedron
Lett. 2006, 47, 487–492; (c) Togo, H.; Iida, S. Synthetic use of molecular
iodine for organic synthesis. Synlett 2006, 14, 2159–2175; (d) Moroda, A.;
Togo, H. Biphenyl- and terphenyl-based recyclable organic trivalent iodine
reagents. Tetrahedron. 2006, 62, 12408–12414; (e) Ishihara, M.; Togo, H. Cam-
pylopin from delphinium campylocentrum, the first hetidane C20-diterpene,
suggests
a new alkaloid biogenetic pathway. Tetrahedron. 2007, 63,
1474–1480; (f) Yamamoto, Y.; Kawano, Y.; Toy, P. H.; Togo, H. PhI- and
polymer-supported PhI-catalyzed oxidative conversion of ketones and alcohols
to a-tosyloxyketones with m-chloroperbenzoic acid and p-toluenesulfonic acid.
Tetrahedron. 2007, 63, 4680–4687; (g) Iida, S.; Togo, H. Direct oxidative conver-
sion of alcohols and amines to nitriles with molecular iodine and DIH in aq NH3.
Tetrahedron. 2007, 63, 8274–8281.
8. (a) Cromwell, N. H.; Mohrbacher, R. J. The stereoisomerism of 1-Cyclohexyl-2-
methyl-3-(p-phenylbenzoyl)-ethylenimine1. J. Am. Chem. Soc. 1953, 75,
6252–6256; (b) Yadav, J. S.; Subba Reddy, B. V.; Sabitha, G.; Reddy, G. S. K.
K. Aromatization of Hantzsch 1,4-dihydropyridines with I2-MeOH. Synthesis
2000, 1532–1534; (c) Fujiki, K.; Tanifuji, N.; Sasaki, Y.; Yokoyama, T. New

1210
B. Liu and S.-J. Ji
and facile synthesis of thiosulfonates from sulfinate/disulfide/I2 system. Synthesis
2002, 343–348; (d) Ramalinga, K.; Vijayalakshmi, P.; Kaimal, T. N. B. A mild
and efficient method for esterification and transesterification catalyzed by
iodine. Tetrahedron Lett. 2002, 43, 879–882; (e) Chavan, S. P.; Kale, R. R.;
Shivasankar, K.; Chandake, S. I.; Benjamin, S. B. A simple and efficient
method for transesterification of b-Ketoesters catalysed by iodine. Synthesis
2003, 2695–2698; (f) Basu, M. K.; Samajdar, S.; Becker, F. F.; Banik, B. K. A
new molecular iodine-catalyzed acetalization of carbonyl compounds. Synlett
2002, 319–321; (g) Samajdar, S.; Basu, M. K.; Becker, F. F.; Chandake, S. I.;
Benjamin, S. B. A new molecular iodine-catalyzed thioketalization of carbonyl
compounds: selectivity and scope. Tetrahedron Lett. 2001, 42, 4425–4427;
(h) Yadav, J. S.; Reddy, B. V. S.; Shubashree, S.; Sadashiv, K. Iodine/MeOH: a
novel and efficient reagent system for thiocyanation of aromatics and heteroaro-
matics. Tetrahedron Lett. 2004, 45, 2951–2954; (i) Minakata, S.; Kano, D.;
Oderaotoshi, Y.; Komatsu, M. Silica-water reaction media: its application to the
formation and ring opening of aziridines. Angew. Chem., Int. Ed. 2004, 43,
79–81; (j) Banik, B. K.; Samajdar, S.; Banik, I. Simple synthesis of substituted
pyrroles. J. Org. Chem. 2004, 69, 213–216; (k) Karimi, B.; Zareyee, D. N-Bromo-
succinimideand iodine catalyzed highly efficient deoxygenation of sulfoxides to
thioethers using 3-mercaptopropionic acid under mild reaction conditions.
Synthesis 2003, 1875–1877.
9. (a) Palacios, M. L. D.; Comdom, R. F. P. Synthesis of 11H-Pyrido[2,1-b]quinazo-
lin-11-one and derivatives using ultrasound irradiation. Synth. Commun. 2003, 33,
1777–1789; (b) Li, J.-T.; Yang, W.-Z.; Wang, S.-X.; Li, S.-H.; Li, T.-S. Improved
synthesis of chalcones under ultrasound irradiation. Ultrason. Sonochem. 2002, 9,
237–241; (c) Li, J.-T.; Yang, W.-Z.; Chen, G.-F.; Li, T.-S. A facile synthesis of,
‘-bis(Substituted Benzylidene) cycloalkanones catalyzed by KF/Al2O3 under
ultrasound irradiation. Synth. Commun. 2003, 33, 2619–2629; (d) Jayasree, J.;
Rao, J. M. Sonochemical acetylation reactions of tertiary alkyl halides. Synth.
Commun. 1996, 26, 3717–3726; (e) Bettadaiah, B. K.; Gurudutt, K. N.;
Srinivas, P. Ultrasound-assisted nucleophilic substitution reaction of t-alkyl
halides with zinc and titanium thiocyanate. Synth. Commun. 2003, 33,
2293–2304; (f) Yang, J.-H.; Li, J.-T.; Zhao, J.-L.; Li, T.-S. Pinacol coupling
reaction of aromatic aldehydes mediated by Zn in acid aqueous media under ultra-
sound irradiation. Synth. Commun. 2004, 34, 993–1002; (g) Chandrasekhar, S.;
Narsihmulu, C.; Jagadeshwar, V. Ultrasound promoted ‘one pot’ conversion of
nitrocompounds to carbamates. Synlett 2002, 5, 771–773; (h) Li, J.-T.;
Lin, Z.-P.; Qi, N.; Li, T.-S. Pinacol coupling of aromatic aldehydes and ketones
using TiCl3-Al-EtOH under ultrasound irradiation. Synth. Commun. 2004, 34,
4339–4346; (i) Comdom, R. F. P.; Palacios, M. L. D. The use of ultrasound in
the synthesis of 2-carboxy substituted diphenylethers using water as solvent.
Synth. Commun. 2003, 33, 921–930; (j) Fernando, C.; Wanda, P. A.;
Demetrius, V.; Cristiano, R. M.; Silva Lopes, E. C.; Rodrigo, C. R.;
Silveira, G. P. C.; Pavam, C. H. Ultrasound in Baylis–Hillman reactions with
aliphatic and aromatic aldehydes: scope and limitations. Tetrahedron. 2002, 58,
7437–7447; (k) Zhang, J.-G.; Duan, W.-H.; Cai, J.-C. Asymmetric synthesis of
3(S),17-dihydroxytanshinone. Tetrahedron. 2004, 60, 1665–1669.
10. (a) Ji, S.-J.; Wang, S.-Y. Ultrasound-accelerated Michael addition of indole to a,b-
unsaturated ketones catalyzed by ceric ammonium nitrate (CAN). Synlett 2003, 13,
2074–2076; (b) Ji, S.-J.; Wang, S.-Y.; Zhang, Y.; Loh, T.-P. Facile synthesis of
bis(indolyl)methanes using catalytic amount of iodine at room temperature

2-Amino-1,4-naphthoquinones
1211
under solvent-free conditions. Tetrahedron 2004, 60, 2051–2055; (c) Zeng, X.-F.;
Ji, S.-J. Novel method for synthesis of unsymmetrical bis(indolyl)alkanes
catalyzed by ceric ammonium nitrate (CAN) under ultrasonic irradiation. Tetrahe-
dron 2005, 61, 10235–10241; (d) Shen, Z.-L.; Ji, S.-J.; Zeng, X.-F. A novel base-
promoted synthesis of ?-indolylketones via a three-component condensation under
ultrasonic irradiation. Tetrahedron 2005, 61, 10552–10558; (e) Wang, S.-Y.;
Ji, S.-J. Facile synthesis of 3,3-di(heteroaryl)indolin-2-one derivatives catalyzed
by ceric ammonium nitrate (CAN) under ultrasound irradiation. Tetrahedron
2006, 62, 1527–1535.
11. (a) Aristoff, P. A.; Johnson, P. D. Synthesis of CBI-PDE-I-dimer, the benzanne-
lated analog of CC-1065. J. Org. Chem. 1992, 57, 6234–6239;
(b) Agarwal, N. L.; Schaefer, W. Quinone chemistry. Reaction of 2,3-dichloro-
1,4-naphthoquinone with arylamines in pyridine. J. Org. Chem. 1980, 45,
5139–5143; (c) Tandon, V. K.; Singh, R. V.; Rai, S.; Chhor, R. B.; Khan, Z. K.
Synthesis and pharmacological studies of some 2-t-amino and 2,3-di-t-amino sub-
stituted 1,4-naphthoquinones and related compounds. Boll. Chim. Farm. 2002,
141, 304–310; (d) Falling, S. N.; Rapoport, H. Routes to mitomycins. Application
of iminium salts to the synthesis of naphthoquinone mitosene analogs. J. Org.
Chem. 1980, 45, 1260–1270; (e) US Rubber Co Chem. Abstr. 1962, 57, 15031c;
(f) Kobayashi, K.; Suzuki, M.; Takeuchi, H.; Konishi, A.; Sakurai, H.;
Suginome, H. Photoinduoed molecular transformations. Part 146. Photoacylation
and photoalkylation of 2-arylamino- and 2-alkylamino-1,4-naphthoquinones.
J. Chem. Soc. Perkin Trans. 1 1994, 8, 1099–1104.