Nitrophenol derivatives oxidized by cerium(IV) ammonium nitrate (CAN) and their cytotoxicity

Article abstract of DOI:10.1002/jccs.200500086

Oxidation of a series of phenols with cerium(IV) ammonium nitrate (CAN) in acetonitrile undermild conditions yields the mixture of corresponding nitrophenols. In the cases of methylphenols and hydroxy-carboxylic acids, the steric effect may reduce the nitration reaction. Compounds 3 a and 4b showed selective activities to Hep 3B and Hep G2 cancer cell lines, respectively. Compound 2c showed selective activities to Hep G2 and MDA-MB-231 cancer cell lines. Further more, com pound 10b showed selective activities to Hep G2, Hep 3B, MCF-7 and MDA-MB-231 cancer cell lines.

Full text of DOI:10.1002/jccs.200500086

Journal of the Chinese Chemical Society, 2005, 52, 581-588
581
Nitrophenol Derivatives Oxidized by Cerium(IV) Ammonium Nitrate (CAN)
and their Cytotoxicity
Wen-Bin Pana (
Chin-Chung Wub (
), Li-Mei Weia (
), Li-Lan Weia (
) and Yang-Chang Wub* (
),
), Fang-Rong Changb (
)
aFooyin University, Kaohsiung County 831, Taiwan, R.O.C.
bGraduate Institute of Natural Products, Kaohsiung Medical University, Kaohsiung 807, Taiwan, R.O.C.
Oxidation of a series of phenols with cerium(IV) ammonium nitrate (CAN) in acetonitrile under mild
conditions yields the mixture of corresponding nitrophenols. In the cases of methylphenols and hydroxy-
carboxylic acids, the steric effect may reduce the nitration reaction. Compounds 3a and 4b showed selective
activities to Hep 3B and Hep G2 cancer cell lines, respectively. Compound 2c showed selective activities to
Hep G2 and MDA-MB-231 cancer cell lines. Furthermore, compound 10b showed selective activities to Hep
G2, Hep 3B, MCF-7 and MDA-MB-231 cancer cell lines.
Keywords: Cerium(IV) ammonium nitrate; Nitrophenols; Oxidative addition; Cytotoxicity.
INTRODUCTION
For decades, the strong oxidizing properties of CAN
Grenier et al. have reported the ring nitration of electron-rich
methoxyphenyl derivatives with CAN/SiO2 in 1999.12 Moridani
et al. have reported the quantitative structure toxicity rela-
tionships for phenols in isolated rat hepatocytes in 2003.13
Now we report, herein, the ring nitration of several phenol
derivatives with CAN. An important purpose of this paper is
to clarify the reaction conditions and to refocus attention on
the ability of CAN to both ring nitration and oxidative addi-
tion of phenol derivatives. The cytotoxicities toward Hep G2,
Hep 3B, MCF-7, and MDA-MB-231 cells, and the structure-
activity relationship of the isolated products are also revealed
for the first time.
have been shown to be extremely useful in synthetic organic
chemistry.1 It has also been employed adsorbed on silica gel
for oxidative nitration of polynuclear arenas.2 Nitration of
phenols as a special case has been studied using various ni-
trating agents under different conditions.3 CAN has proved to
be an ideal reagent because the mild conditions involved.
CAN in protic solvent (acetonitrile, water/acetonitrile or
methanol) has been widely employed for the oxidative addi-
tion of 2-hydroxynaphthoquinone to dienes,4 oxidative de-
methylation of 1,4-dimethoxyphenyl derivatives,5 and oxida-
tion of benzylamines or benzylalcohols into benzaldehydes.6
Oxidative addition of soft anions to alkenes mediated by
CAN in protic solvent has also been shown to offer a practical
method carbon-heteroatom (C-O, C-S, and C-Br) bond for-
mation.7,8 In our previous investigation, we have reported the
use of CAN for the esterification of aliphatic carboxylic acids
with simple primary and secondary alcohols9 and esterifica-
tion-nitration of ortho-hydroxyphenyl carboxylic acids and
benzoic acids with CAN.10 Seeking milder conditions, we fo-
cused on the use of CAN, which has been employed for nitra-
tion purposes. In 1994, Chakrebarty and Batabyal have re-
ported the nitration of carbazols by CAN in acetonitrile in the
presence of (not adsorbed on) silica gel at 70-75 °C.11 Unfor-
tunately the reaction did not take place without silica gel.
RESULTS AND DISCUSSION
We reacted several phenol derivatives with CAN in
acetonitrile from 20 min to 24 h (in the case of no reaction or
low yield after 20 min) at room temperature. Results are re-
ported in Table 1. Furthermore, the cytotoxicities of the iso-
lated products toward various cancer cells were evaluated.
Under these conditions, phenol 1 gave 2-nitrophenol 1a
and 4-nitrophenol 1b in 41% and 28% yields, respectively
(entry 1, Table 1). Methylphenols 2-4 gave nitrophenols. In
addition, 2-methylphenol 2 and 4-methylphenol 4 gave oxi-
dative addition derivatives as minor products. In the reaction
of 2, the products were 6-methyl-2-nitrophenol 2a, 2-meth-
* Corresponding author. Tel: +886-7-3121101 ext 2197; Fax: +886-7-3114773; E-mail: yachwu@kmu.edu.tw

582 J. Chin. Chem. Soc., Vol. 52, No. 3, 2005
Pan et al.

Nitrophenol Derivatives and Cytotoxicity
OH
J. Chin. Chem. Soc., Vol. 52, No. 3, 2005 583
NO2
OH
OH
OH
O2N
NO2
O2N
COOH
COOH
COOH
8b (18%)
8
COOH
8c (14%)
8a (50%)
8
12 h
NO2
OH
O2N
COOH
8d (10%)
OH
OH
OH
9
20 min
HOOC
HOOC
NO2
O2N
1b (10%)
9a (84%)
9
OH
O
OH
NO2
10
20 min
NO2
O
10
10b (31%)
10a (42%)
NO2
OH
OH
11
2 h
11
11a (41%)
* Yields refer to the isolated yields. All of the compounds were assigned in view of 1H NMR, 13C NMR and MS spectra data.
yl-4-nitrophenol 2b, and the oxidative addition product, 2-
(4-hydroxy-3-methylphenyl)-6-methylcyclohexa-2,5-diene-
1,4-dione 2c in 36, 27, 13% yields, respectively after 24 h
(entry 2, Table 1). 3-Methylphenol 3 led to the 3-methyl-4-
nitrophenol 3a, 3-methyl-2-nitrophenol 3b, and 5-methyl-2-
nitrophenol 3c in 40%, 21% and 22% yields, respectively af-
ter 24 h (entry 3, Table 1). Compound 4 led to the 4-methyl-
2-nitrophenol 4a as major products, along with the oxidative
addition products, 2-(2-hydroxy-5-methyl-3-nitrophenyl)-
4-methyl-6-nitrophenol 4b and 1,4-dimethyl-8-oxatricyclo-
[7.3.1.0<2,7>]trideca-2(7),3,5,11-tetraen-10-one 4c as mi-
nor products in 77%, 12% and 10% yields, respectively after
12 h (entry 4, Table 1). The structure of 4c was established by
spectroscopic data. The 1H NMR signal at d 4.69 (1H, m) was
assigned to the oxymethine proton attached to the ring junc-
tion carbon C-9. The methylene protons at d 3.04 (1H, ddd, J
= 19.6, 4.0, 1.0 Hz) and d 2.79 (1H, dd, J = 19.6, 4.0 Hz) were
assigned to H-13. The reaction of 4 is apparently faster than
those of 2 and 3, indicating that the steric hindrance affects
the rate of nitration of methylphenols. Interestingly, from the
reactions of iodophenols 5 and 6 for 2 h, 4,6-diiodo-2-nitro-
phenol 5a and 4-iodo-2-nitrophenol 5b were isolated as the
major products (entries 5, 6, Table 1). Iodonation, mono-
nitration, and nitrodeiodonation reactions occur in these two

584 J. Chin. Chem. Soc., Vol. 52, No. 3, 2005
Pan et al.
Table 2. Cytotoxicity of phenol derivatives against various
cases. Moreover, the reaction rates of iodophenols are appar-
ently faster than those of methyl phenols or hydroxyl benzoic
acids by the comparison of their reaction time.
cancer cell lines
Cytotoxicity IC50 (mg/mL)
In another series of reactions, we reacted some hydroxy-
benzoic acids 7-9 which possess an additional electron-
withdrawing group under the same reaction conditions. 2-
Hydroxybenzoic acid 7 underwent simultaneous nitrodecar-
boxylation and mononitraton reactions to give in high yield a
mixture of 2,4-dinitrophenol 7a and 2,6-dinitrophenol 7b in
95% and 3% yields, respectively, whereas 3-hydroxybenzoic
acid 8 gave mononitrophenols, 8a (50%) and 8b (18%), as
well as dinitrophenols, 8c (14%) and 8d (10%) after 12 h.
4-Hydroxybenzoic acid 9 gave mononitrophenol, 9a (84%)
along with nitrodecarboxylation product 1b (10%) as minor
product after 20 min. The reaction of 9 is faster than those of
7 and 8, indicating the steric hindrance also affects the rate of
nitration reaction of hydroxybenzoic acids. In the reactions
of naphthols, 1-naphthol 10 afforded dinitronaphthol 10a
(42%) and the oxidized product, naphthalene-1,4-dione 10b
(31%) after 20 min, whereas 2-naphthol 11 gave mononitro-
naphthol 11a (41%) after 2 h.
Compounds Hep G2
Hep 3B
MCF-7 MDA-MB-231
1a
1b
2a
2b
2c
> 30.00
27.21
> 30.00
18.96
> 30.00
22.28
> 30.00
19.40
18.10
1.22
> 30.00
> 30.00
> 30.00
> 30.00
21.79
> 30.00
> 30.00
> 30.00
> 30.00
> 30.00
18.59
> 30.00
> 30.00
> 30.00
26.67
> 30.00
> 30.00
> 30.00
23.59
5.75
18.52
5.43
3a
3b
3c
4a
4b
4c
18.30
> 30.00
> 30.00
> 30.00
> 30.00
> 30.00
> 30.00
> 30.00
> 30.00
> 30.00
> 30.00
> 30.00
> 30.00
2.14
> 30.00
> 30.00
> 30.00
> 30.00
> 30.00
29.09
> 30.00
> 30.00
> 30.00
> 30.00
13.72
> 30.00
> 30.00
> 30.00
3.92
17.91
5a
5b
6a
7a
9a
10a
10b
11a
> 30.00
> 30.00
> 30.00
> 30.00
> 30.00
18.54
> 30.00
0.85
1.79
> 30.00
6.47
> 30.00
> 30.00
> 30.00
The cytotoxicities of compounds 1a, 1b, 2a-2c, 3a-3c,
4a-4c, 5a-5b, 6a, 7a, 9a, 10a, 10b, 11a were evaluated
against the cell lines of human hepatocellular carcinoma Hep
G2 and Hep 3B, human breast carcinoma MCF-7 and MDA-
MB-231. The results are presented in Table 2. Compound 2c
showed selective activities to Hep G2 and MDA-MB-231
cancer cell lines with IC50 values 5.75 and 5.43 mg/mL, re-
spectively. Compound 3a showed selective activity to a Hep
3B cancer cell line with IC50 value 1.22 mg/mL. Compound
4b showed selective activity to a Hep G2 cancer cell line with
IC50 value 3.92 mg/mL. Compound 10b showed selective ac-
tivities to Hep G2, Hep 3B, MCF-7 and MDA-MB-231 can-
cer cell lines with IC50 values 1.79, 6.47, 2.14, and 0.85
mg/mL, respectively. However, the other compounds exhib-
ited weak or no effect to the growth inhibition of Hep G2, Hep
3B, MCF-7, and MDA-MB-231 cell lines.
pounds 3a and 4b showed selective activities to Hep 3B and
Hep G2 cancer cell lines, respectively. Compound 2c showed
selective activities to Hep G2 and MDA-MB-231 cancer cell
lines. Compound 10b showed selective activities to Hep G2,
Hep 3B, MCF-7 and MDA-MB-231 cancer cell lines. Three
main points are apparent from these results. Firstly, the p-
nitrophenol functionality in such nitrophenol compounds 1b,
2b, and 3a seems to play an important role in cytotoxicities to
Hep G2 and Hep 3B cancer cell lines. Secondly, the o-nitro-
phenols does not show the activity due to hydrogen bond
while compound 4b shows activity that may be driven by in-
tercalation. Thirdly, the para-quinone moiety in compounds
2c and 10b has a large influence on cytotoxicities to Hep G2,
Hep 3B, MCF-7 and MDA-MB-231 cancer cell lines.
In conclusion, we have shown that CAN in acetonitrile
is an efficient and mild nitrating agent of phenols. Numerous
functionalities (e.g.; -CH3, -I, -CO2H) were tolerated in the
reaction conditions. In the cases of methylphenols and hy-
droxycarboxylic acids, the steric effect may reduce the nitra-
tion reaction. The limitations are due to (1) low regioselec-
tivity of most substrates; (2) the strong oxidizing power of
CAN often leads to over-oxidized products; and (3) competi-
tion with the oxidative addition reaction in the cases of
4-methylphenols and 2-methylphenols. Furthermore, com-
EXPERIMENTAL SECTION
General
1H and 13C NMR spectra were acquired on a Varian
Germini 200 MHz FT-NMR running at 200 Mz (1H) or 50
MHz (13C), respectively. Chemical shifts (d) were reported in
ppm relative to residual solvent signals. The multiplicities of
1H signals are designated by the following abbreviations: s =
singlet; d = doublet; t =triplet; q = quartet; br = broad; m =

Nitrophenol Derivatives and Cytotoxicity
J. Chin. Chem. Soc., Vol. 52, No. 3, 2005 585
multiplet. All coupling constants, J, are reported in Hertz. 13
C
4-Nitrophenol (1b)
NMR spectra were acquired on a broad band decoupled mode
and the multiplicities were obtained using DEPT sequences.
Melting points were determined using a Fargo MP-1D melt-
ing point apparatus and are uncorrected. Mass spectra were
recorded on a JEOL TMSD-100 Mass spectrometer. Flash
column chromatography was carried out using silica gel 60
(Merck, 230-400 mesh). Analytical thin layer chromatogra-
phy (TLC) was performed using precoated aluminium-
backed plates (Merck Kieselgel 60 F254) and visualized by
ultraviolet irradiation. Analytical grade solvents were used as
received. The CAN used for the reactions was purchased
from Lancaster Co. and was used without purification.
Compound 1b was prepared according to general pro-
cedure and after 24 h the product was isolated as white nee-
1
dles. mp 115-116 °C (lit.15 114 °C). H NMR (CDCl3, 200
MHz): d 8.16 (dd, 2H, J = 9.2, 2.4 Hz), 6.93 (dd, 2H, J = 9.2,
2.4 Hz), 6.41 (br s, 1H). 13C NMR (CDCl3, 50 MHz): d 161.9,
141.3, 126.3, 126.3, 115.7, 115.7. EI-MS m/z (rel. int. %):
139 (M+, 100), 109 (47), 65 (72), 43 (72).
6-Methyl-2-nitrophenol (2a)
Compound 2a was prepared according to general pro-
cedure and after 24 h the product was isolated as a yellow
1
solid. mp 70-71 °C (lit.16 71 °C). H NMR (CDCl3, 200
MHz): d 10.90 (s, 1H, -OH), 7.94 (d, 2H, J = 8.6 Hz), 7.43 (d,
2H, J = 7.4 Hz), 6.86 (dd, 2H, J = 8.6, 7.4 Hz), 2.32 (s, 6H).
13C NMR (CDCl3, 50 MHz): d 153.5, 137.9, 132.0, 129.2,
122.3, 119.0, 15.5. EI-MS m/z (rel. int. %): 153 (64), 107
(19), 105 (17), 77 (100), 52 (51).
General procedure for CAN mediated nitration of phe-
nols
To a solution of phenols (1.6 mmol) in acetonitrilel was
added a solution of CAN (1.26 g, 2.3 mmol) in acetonitrile at
room temperature. The mixture was stirred for 20 min or
more. The solvent was removed on a rotary evaporator and
the residue was diluted with saturated aqueous NaCl solution
and extracted with EtOAc (3 ´ 15 mL). The extracts were
dried over anhydrous MgSO4. After the removal of the sol-
vent, the residue was subjected to column chromatography on
silica gel to afford the corresponding products.
2-Methyl-4-nitrophenol (2b)
Compound 2b was prepared according to general pro-
cedure and after 24 h the product was isolated as a white
1
solid. mp 95-96 °C (lit.17 94 °C). H NMR (CDCl3, 200
MHz): d 8.05 (d, 1H, J = 2.8 Hz), 8.00 (dd, 1H, J = 8.8, 2.8
Hz), 6.87 (d, 1H, J = 8.8 Hz), 6.71 (br s, 1H, -OH). 13C NMR
(CDCl3, 50 MHz): d 160.2, 141.0, 126.9, 125.4, 123.7, 114.8,
15.80. EI-MS m/z (rel. int. %): 153 (22), 123 (14), 77 (100),
67 (25), 51 (30), 43 (64).
Cytotoxicity Assays
Compounds were assayed for cytotoxicity against Hep
G2, Hep 3B, MCF-7, and MDA-MB-231 cells using the MTT
method. Freshly trypsinized cell suspensions were seeded in
96-well microtitre plates at densities of 5,000-10,000 cells
per well with tested compounds added from DMSO-diluted
stock. After 3 days in culture, attached cells were incubated
with MTT (0.5 mg/mL, 1 hr) and subsequently solubilized in
DMSO. The absorbency at 550 nm was then measured using a
microplate reader. The IC50 is the concentration of agent that
reduced cell growth by 50% under the experimental condi-
tions.
2-(4-Hydroxy-3-methylphenyl)-6-methylcyclohexa-2,5-
diene-1,4-dione (2c)
Compound 2c was prepared according to general proce-
dure and after 24 h the product was isolated as a red solid. mp
148-149 °C (lit.18 149-150 °C). 1H NMR (CDCl3, 200 MHz):
d 7.28 (d, 1H, J = 1.6 Hz), 7.25 (dd, 1H, J = 8.0, 2.4 Hz), 6.82
(d, 1H, J = 8.0 Hz), 6.74 (d, 1H, J = 2.4 Hz), 6.65 (qd, 1H, J =
1.6, 1.6 Hz), 5.24 (br s, 1H, -OH), 2.28 (s, 3H), 2.12 (d, 1H, J
= 1.6 Hz). EI-MS m/z (rel. int. %): 228 (100), 213 (13), 200
(27), 185 (26), 157 (15), 132 (27), 68 (21).
2-Nitrophenol (1a)
Compound 1a was prepared according to general pro-
cedure and after 24 h the product was isolated as yellow nee-
dles. mp 44-45 °C (lit.14 46 °C). 1H NMR (CDCl3, 200 MHz):
d 10.59 (s, 1H), 8.11 (dd, 1H, J = 8.4, 1.8 Hz), 7.59 (td, 1H, J
= 7.8, 1.6 Hz), 7.16 (dd, 1H, J = 8.4, 1.2 Hz), 6.99 (td, 1H, J =
8.0, 1.2 Hz). 13C NMR (CDCl3, 50 MHz): d 165.5, 155.3,
137.7, 125.2, 120.4, 120.1.
3-Methyl-4-nitrophenol (3a)
Compound 3a was prepared according to general pro-
cedure and after 24 h the product was isolated as an orange
red solid. mp 129-130 °C (lit.19 129 °C). H NMR (CDCl3,
1
400 MHz): d 8.05 (d, 1H, J = 9.6 Hz), 6.76 (dd, 1H, J = 9.6,
3.2 Hz), 6.75 (d, 1H, J = 3.2 Hz). 13C NMR (CDCl3, 50 MHz):
d 159.8, 137.5, 127.9, 118.9, 113.6, 113.2, 21.5. EI-MS m/z

586 J. Chin. Chem. Soc., Vol. 52, No. 3, 2005
Pan et al.
(rel. int. %): 153 (M+, 48), 136 (100), 77 (54).
4.0 Hz, H-13), 2.32 (s, 3H), 1.57 (s, 3H). 13C NMR (CDCl3,
50 MHz): d 195.1, 156.7, 149.6, 132.2, 131.1, 129.7, 125.8,
123.2, 110.1, 86.5, 45.1, 37.5, 21.4, 20.9. EI-MS m/z (rel. int.
%): 214 (100), 199 (87), 171 (55), 128 (41), 115 (41). HREIMS
m/z Found 214.0995 (Calcd for C14H14O2 214.0993).
3-Methyl-2-nitrophenol (3b)
Compound 3b was prepared according to general pro-
cedure and after 24 h the product was isolated as yellow green
liquid. 1H NMR (CDCl3, 200 MHz): d 10.36 (br s, 1H, -OH),
7.38 (t, 1H, J = 8.0 Hz), 7.01 (dt, 1H, J = 8.0, 0.8 Hz), 6.84 (dt,
1H, J = 8.0, 0.8 Hz), 2.63 (s, 3H). 13C NMR (CDCl3, 50
MHz): d 155.4, 136.8, 135.2, 130.0, 124.0, 117.6, 22.4.
4,6-Diiodo-2-nitrophenol (5a)
Compound 5a was prepared according to general pro-
cedure and after 2 h the product was isolated as yellow liquid.
1H NMR (CDCl3, 200 MHz): d 11.27 (br s, 1H, -OH), 8.41 (d,
1H, J = 2.2 Hz), 8.34 (d, 1H, J = 2.2 Hz). 13C NMR (CDCl3, 50
MHz): 154.1, 153.8, 133.6. EI-MS m/z (rel. int. %): 391 (13),
218 (14), 189 (15), 91 (45), 61 (100).
5-Methyl-2-nitrophenol (3c)
Compound 3c was prepared according to general proce-
dure and after 24 h the product was isolated as yellow nee-
1
dles. mp 127-128 °C (lit.20 128 °C). H NMR (CDCl3, 200
MHz): d 10.61 (s, 1H, -OH), 7.97 (d, 1H, J = 8.6 Hz), 6.93 (d,
1H, J = 2.0 Hz), 6.78 (dd, 1H, J = 8.6, 2.0 Hz), 2.39 (s, 3H).
13C NMR (CDCl3, 50 MHz): d 155.1, 149.8, 131.8, 124.9,
121.6, 119.6, 21.8.
4-Iodo-2-nitrophenol (5b)
Compound 5b was prepared according to general pro-
cedure and after 2 h the product was isolated as yellow nee-
dles. mp 81-82 °C (lit.22 81 °C). 1H NMR (CDCl3, 200 MHz):
d 10.51 (br s, -OH), 8.41 (d, 1H, J = 2.2 Hz), 7.82 (dd, 1H, J =
8.8, 2.2 Hz), 6.95 (d, 1H, J = 8.8 Hz). 13C NMR (CDCl3, 50
MHz): 154.8, 145.9, 134.5, 133.2, 124.0, 122.0. EI-MS m/z
(rel. int. %): 265 (73), 219 (12), 207 (15), 191 (12), 127 (15),
92 (68), 63 (100).
4-Methyl-2-nitrophenol (4a)
Compound 4a was prepared according to general pro-
cedure and after 12 h the product was isolated as yellow liq-
uid. 1H NMR (CDCl3, 200 MHz): d 10.40 (s, 1H, -OH), 7.84
(d, 1H, J = 2.2 Hz), 7.37 (dd, 1H, J = 8.6, 2.2 Hz), 7.02 (d, 1H,
J = 8.6 Hz), 2.32 (s, 3H). 13C NMR (CDCl3, 50 MHz): d
153.0, 138.7, 133.0, 130.1, 124.3, 119.5, 20.1. EI-MS m/z
(rel. int. %): 153 (100), 136 (18), 123 (15), 107 (13), 77 (32).
2-Iodo-4-nitrophenol (6a)
Compound 6a was prepared according to general pro-
cedure and after 2 h the product was isolated as brown oil. 1H
NMR (CDCl3, 400 MHz): d 8.60 (d, 1H, J = 1.6 Hz), 8.17 (dd,
1H, J = 8.8, 1.6 Hz), 7.07 (d, 1H, J = 8.8 Hz), 6.27 (br s, 1H,
-OH). 13C NMR (CDCl3, 100 MHz): d 160.3, 134.4, 133.8,
127.2, 126.1, 114.6. EI-MS m/z (rel. int. %): 265 (70), 235
(26), 92 (100), 63 (76).
2-(2-Hydroxy-5-methyl-3-nitrophenyl)-4-methyl-6-nitro-
phenol (4b)
Compound 4b was prepared according to general pro-
cedure and after 12 h the product was isolated as a yellow
1
solid. mp 211-212 °C (lit.21 210-212 °C). H NMR (CDCl3,
400 MHz): d 10.82 (s, 2H, -OH), 8.00 (d, 2H, J = 2.0 Hz),
7.43 (d, 2H, J = 2.0 Hz), 2.40 (s, 6H). 13C NMR (CDCl3, 100
MHz): d 151.0, 151.0, 140.3, 140.3, 133.6, 133.6, 129.4,
129.4, 127.1, 127.1, 124.8, 124.8, 20.4, 20.4. EI-MS m/z (rel.
int. %): 304 (88), 286 (21), 269 (100), 182 (21), 152 (26).
2,4-Dinitrophenol (7a)
Compound 7a was prepared according to general pro-
cedure and after 12 h the product was isolated as colorless
needles. mp 143-144 °C (lit.23 144 °C). H NMR (CD3OD,
1
200 MHz): d 8.83 (d, 1H, J = 2.8 Hz), 8.23 (dd, 1H, J = 9.4,
2.8 Hz), 7.02 (d, 1H, J = 9.4 Hz). 13C NMR (CD3OD, 50
MHz): d 164.7, 138.0, 136.9, 130.5, 123.9, 123.8. EI-MS m/z
(rel. int. %): 184 (M+, 94), 154 (100), 98 (36).
1,4-Dimethyl-8-oxatricyclo[7.3.1.0<2,7>]trideca-2(7),3,5,11-
tetraen-10-one (4c)
Compound 4c was prepared according to general proce-
dure and after 12 h the product was isolated as a yellow solid.
mp 123-124 °C. 1H NMR (CDCl3, 200 MHz): d 7.01 (d, 1H, J
= 1.6 Hz, H-3), 6.99 (dd, 1H, J = 7.8, 1.6 Hz, H-5), 6.71 (d,
1H, J = 7.8 Hz, H-6), 6.46 (dd, 1H, J = 10.0, 2.0 Hz, H-12),
5.92 (dd, 1H, J = 10.0, 1.0 Hz, H-11), 4.69 (m, 1H, H-9), 3.04
(ddd, 1H, J = 19.6, 4.0, 1.0 Hz, H-13), 2.79 (dd, 1H, J = 19.6,
2,6-Dinitrophenol (7b)
Compound 7b was prepared according to general pro-
cedure and after 12 h the product was isolated as colorless
needles. mp 61-62 °C (lit.24 63.5 °C). 1H NMR (CD3OD, 200
MHz): d 8.07 (d, 2H, J = 8.0 Hz), 6.66 (d, 1H, J = 8.0 Hz). 13
NMR (CD3OD, 50 MHz): d 160.9, 160.9, 145.2, 145.2, 131.7,
C

Nitrophenol Derivatives and Cytotoxicity
J. Chin. Chem. Soc., Vol. 52, No. 3, 2005 587
108.1. EI-MS m/z (rel. int. %): 184 (M+, 59), 139 (100), 109
2,4-Dinitronaphthol (10a)
(60), 81 (64), 69 (63).
Compound 10a was prepared according to general pro-
cedure and after 20 min the product was isolated as a brown
solid. mp 129-130 °C (lit.30 139.5 °C). 1H NMR (CDCl3, 200
MHz): d 9.03 (s, 1H), 8.75 (d, 1H, J = 8.6 Hz), 8.66 (d, 1H, J =
3-Hydroxy-4-nitrobenzoic acid (8a)
Compound 8a was prepared according to general pro-
cedure and after 12 h the product was isolated as a pale yel-
low solid. mp 232-233 °C (lit.25 231-237 °C). H NMR
8.6 Hz), 7.99 (t, 1H, J = 8.6 Hz), 7.80 (t, 1H, J = 8.6 Hz). 13
C
1
NMR (CD3OD, 50 MHz): d 167.9, 151.5, 144.7, 133.1,
130.6, 127.6, 127.2, 127.1, 124.9. EI-MS m/z (rel. int. %):
234 (26), 129 (36), 113 (42), 69 (85), 55 (100).
(CD3OD, 400 MHz): d 8.09 (d, 1H, J = 8.8 Hz), 7.72 (d, 1H, J
= 1.6 Hz), 7.58 (dd, 1H, J = 8.8, 1.6 Hz). 13C NMR (CD3OD,
50 MHz): d 167.5, 154.5, 138.9, 129.9, 126,4, 122.0, 121.4.
EI-MS m/z (rel. int. %): 183 (24, M+), 153 (11), 119 (26), 97
(43), 81 (45), 63 (100).
Naphthalene-1,4-dione (10b)
Compound 10b was prepared according to general pro-
cedure and after 20 min the product was isolated as a yellow
solid. mp 122-123 °C (lit.31 124.3-125.3 °C). 1H NMR (CD3OD,
200 MHz): d 8.05 (m, 2H), 7.81 (m, 2H), 7.00 (s, 2H). 13C
NMR (CD3OD, 50 MHz): d 186.3, 139.8, 135.1, 133.3,
127.2. EI-MS m/z (rel. int. %): 158 (100), 130 (67), 102 (98),
76 (38).
5-Hydroxy-2-nitrobenzoic acid (8b)
Compound 8b was prepared according to general pro-
cedure and after 12 h the product was isolated as an orange
red solid. mp 128-129 °C (lit.26 128-130 °C). H NMR
1
(CD3OD, 200 MHz): d 7.93 (d, 1H, J = 8.8 Hz), 6.67 (d, 1H, J
= 3.6 Hz), 6.65 (dd, 1H, J = 8.8, 3.6 Hz). 13C NMR (CD3OD,
50 MHz): d 166.0, 159.0, 133.0, 126.5, 118.3, 106.9, 106.2.
1-Nitronaphthalen-2-ol (11a)
Compound 11a was prepared according to general pro-
cedure and after 2 h the product was isolated as a yellow
3-Hydroxy-2,6-dinitrobenzoic acid (8c)
1
Compound 8c was prepared according to general proce-
dure and after 12 h the product was isolated as an orange red
solid. mp 181-182 °C (lit.27 180.5-181.5 °C). 1H NMR (CD3OD,
200 MHz): d 7.84 (d, 1H, J = 8.6 Hz), 6.46 (d, 1H, J = 8.6 Hz).
13C NMR (CD3OD, 50 MHz): d 157.9, 138.5, 126.4, 115.7,
114.8, 107.1.
solid. mp 106-107 °C (lit.32 104 °C). H NMR (CDCl3, 200
MHz): d 12.18 (s, 1H, -OH), 8.89 (d, 1H, J = 8.8 Hz), 7.98 (d,
1H, J = 9.2 Hz), 7.80 (dd, 1H, J = 8.0, 1.0 Hz), 7.71 (td, 1H, J
= 8.0, 2.0 Hz), 7.49 (td, 1H, J = 8.0, 1.0 Hz), 7.23 (d, 1H, J =
9.0 Hz). 13C NMR (CDCl3, 50 MHz): d 158.8, 139.1, 130.9,
129.3, 128.6, 128.2, 126.8, 125.6, 123.2, 119.3. EI-MS m/z
(rel. int. %): 189 (78), 131 (35), 115 (100), 103 (46), 89 (62).
5-Hydroxy-2,4-dinitrobenzoic acid (8d)
Compound 8d was prepared according to general pro-
cedure and after 12 h the product was isolated as a yellow
solid. mp 189-190 °C (lit.28 188-188.5 °C). 1H NMR (CD3OD,
200 Mhz): d 8.74 (s, 1H), 6.64 (s, 1H). 13C NMR (CD3OD, 50
MHz): d 169.7, 144.6, 128.0, 127.6, 126.0, 123.5, 115.4.
EI-MS m/z (rel. int. %): 228 (25), 198 (15), 154 (14), 135
(19), 107 (28), 79 (59), 63 (88), 53 (100).
ACKNOWLEDGEMENTS
We thank the National Science Council of the Republic
of China for financial support of this program.
Received November 8, 2004.
4-Hydroxy-3-nitrobenzoic acid (9a)
Compound 9a was prepared according to general pro-
cedure and after 20 min the product was isolated as a white
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