Nonacid nitration of benzenedicarboxylic and naphthalenecarboxylic acid esters

Article abstract of DOI:10.1021/jo015619d

When treated with nitrogen dioxide in the presence of ozone and a catalytic amount of iron(III) chloride in inert organic solvent at -10 to +5 °C, benzenedicarboxylic acid diesters 1, 4, and 6 underwent smooth nitration to give the corresponding mononitro derivatives 2/3, 5, and 7, respectively, in good yield (kyodai nitration). Naphthalenecarboxylic acid esters 8 and 11 and naphthalene-1,8-dicarboxylic acid diester 16 were similarly nitrated in the absence of catalyst to give the expected nitro compounds 9/10, 12-15, and 17-22, respectively. Different from conventional nitration based on the combined use of concentrated nitric and sulfuric acids, no hydrolytic cleavage of the ester function was observed under these conditions. The isomer distribution has been determined for the nitration of naphthalenecarboxylic acid esters 8, 11, and 16, and spectral data were collected for less common nitro derivatives. A unique changeover of the orientation mode observed in the kyodai nitration of diester 16, from the initial exclusive meta to the final meta/para, has been discussed in terms of the competition between the electrophilic substitution process involving the nitronium ion (NO₂⁺) and the addition-elimination sequence involving the nitrogen trioxide radical (NO₃).

Full text of DOI:10.1021/jo015619d

4356
J . Org. Chem. 2001, 66, 4356-4360
Non a cid Nitr a tion of Ben zen ed ica r boxylic a n d
Na p h th a len eca r boxylic Acid Ester s
Masatoshi Nose,† Hitomi Suzuki,*,† and Hideo Suzuki‡
Department of Chemistry, School of Science, Kwansei Gakuin University, Uegahara,
Nishinomiya 662-8501, J apan, and Central Research Institute, Nissan Chemical Co. Ltd.,
Tsuboi-cho, Funabashi 274-0062, J apan
hsuzuki@kwansei.ac.jp
Received March 7, 2001
When treated with nitrogen dioxide in the presence of ozone and a catalytic amount of iron(III)
chloride in inert organic solvent at -10 to +5 °C, benzenedicarboxylic acid diesters 1, 4, and 6
underwent smooth nitration to give the corresponding mononitro derivatives 2/3, 5, and 7,
respectively, in good yield (kyodai nitration). Naphthalenecarboxylic acid esters 8 and 11 and
naphthalene-1,8-dicarboxylic acid diester 16 were similarly nitrated in the absence of catalyst to
give the expected nitro compounds 9/10, 12-15, and 17-22, respectively. Different from
conventional nitration based on the combined use of concentrated nitric and sulfuric acids, no
hydrolytic cleavage of the ester function was observed under these conditions. The isomer
distribution has been determined for the nitration of naphthalenecarboxylic acid esters 8, 11, and
16, and spectral data were collected for less common nitro derivatives. A unique changeover of the
orientation mode observed in the kyodai nitration of diester 16, from the initial exclusive meta to
the final meta/para, has been discussed in terms of the competition between the electrophilic
substitution process involving the nitronium ion (NO2+) and the addition-elimination sequence
involving the nitrogen trioxide radical (•NO3).
In tr od u ction
nitration).1 As part of our continuing program to develop
this new nitration methodology, we have herein extended
it to isomeric benzenedicarboxylic acid diesters, i.e,
phthalate, isophthalate, and terephthalate (1, 4 and 6),
and naphthalenecarboxylic acid esters, i.e., R- and â-naph-
thoic acid esters (8 and 11) and naphthalic acid ester (16).
Nitro derivatives of benzenedicarboxylic acid diesters
are important starting materials for a variety of fine
chemical products including pharmaceuticals and agro-
chemical drugs. They are usually prepared by nitration
followed by esterification of benzenedicarboxylic acids or
by direct nitration of the corresponding diesters. Because
of the poor miscibility of benzenedicarboxylic acids and
their nitro derivatives with nitrating agent and/or organic
solvent, the esters are generally preferred to free acids
for synthetic purposes. Due to the combined electron-
withdrawing effect of two ester functions, the aromatic
ring is so deactivated that the nitration of diesters is
usually carried out by heating gently with fuming nitric
acid, preferably in concentrated sulfuric acid in which
the substrates are protonated to go into solution. After
the reaction, the mixture is diluted with water to collect
the nitration product, which usually separates as a
crystalline solid. This classical methodology is simple and
easy to perform, but the major drawback is that it needs
disposal of large amounts of acid drainage resulting from
workup process. Additionally, the esters are in part
hydrolyzed during the reaction and need a reesterifica-
tion process to improve the quality and yield of the
nitration products.
Resu lts a n d Discu ssion
On treatment with nitrogen dioxide in the presence of
ozone, methyl benzoate readily underwent nitration to
give an isomeric mixture of methyl nitrobenzoates in good
yield.2 The meta and ortho isomers were predominant
(para/meta/ortho ) 3:66:31) and relative importance of
the latter isomer increased as compared to conventional
nitration based on nitric acid and sulfuric acid (meta, 81-
85%).3 When attempts were made to extend this nonacid
methodology to dimethyl benzenedicarboxylates, the
results were unsatisfactory. The reaction was quite slow
and incomplete even by the use of excess reagent.
However, the addition of small amounts of a Lewis acid
catalyst, especially iron(III) chloride, was found to facili-
tate the reaction remarkably and the expected nitro
compounds were obtained in good yield (Scheme 1; Table
1). Of three isomeric dimethyl benzenedicarboxylates,
isophthalate (4a ) was most reactive, followed by tereph-
Previously, we have reported that nitrogen dioxide is
activated in the presence of ozone to react readily with
methyl benzoate under mild conditions to give the
corresponding nitro derivatives in good yield (kyodai
(1) (a) For a survey of the kyodai nitration, see: Matsunaga, M.
Chimica Oggi 1994, 58-61. (b) Mori, T.; Suzuki, H. Synlett 1995, 383-
392. (c) Suzuki, T.; Noyori, R. Chemtracts 1997, 10, 813-817. (d) Ridd,
J . H. Acta Chem. Scand. 1998, 52, 11-22. (e) Nonoyama, N.; Mori, T.;
Suzuki, H. Zh. Org. Khim. 1998, 34, 1591-1601.
(2) Suzuki, H.; Tomaru, J .; Murashima, T. J . Chem. Soc., Perkin
Trans. 1 1994, 2413-2416.
(3) Kamm, O.; Segur, J . B. Organic Syntheses; Wiley: New York,
1941; Collect. Vol. I, pp 372-374.
* To whom correspondence should be addressed. Fax: + 81 798 51
0914.
† Kwansei Gakuin University.
‡ Nissan Chemical Co. Ltd.
10.1021/jo015619d CCC: $20.00 © 2001 American Chemical Society
Published on Web 05/23/2001

Nonacid Nitration of Arenecarboxylic Acid Esters
J . Org. Chem., Vol. 66, No. 12, 2001 4357
Sch em e 1
Sch em e 2
Ta ble 1. Kyod a i Nitr a tion of Ben zen ed ica r boxylic Acid
Ester s 1a ,b, 4a ,c, a n d 6a a
NO2
O3
catalyst
(mol %)
reaction product
time (h) yield (%)
entry substrate (equiv) (equiv)
1
2
1a b
1bb
4a
3.3
6.0
3.0
2.0
FeCl3, 2.2
3.0
3
2a , 52
3a , 42
2b, 39
3b, 38
5b, 84
92
1.5
3
4
5
6
7
4.0
4.0
4.0
4.0
4.0
4.0
4.0
4.0
4.0
4.0
4.0
2.0
3.0
2.4
3.0
2.0
2.0
2.0
2.0
3.0
2.0
3.4
2.0
4.0
2.0
2.0
1.0
1.0
2.4
1.2
1.5
1.5
1.5
1.5
1.5
1.5
1.0
1.7
1.0
2.0
2.0
2.0
45c
PTA,d 50
MeSO3H, 50
97% H2SO4, 50
FeCl3, 0.4
1.0
87
7
10
5c, 71
48
85
67
85
7a , 88
100
8
9
4c
10
11
12
13
14
15
1.0
PTA,d 50
50
6a b
FeCl3, 0.3
0.3
a
All reactions were carried out using substrate (10 mmol), N2O4
(20-40 mmol) and O3 (20-40 mmol) in 1,2-dichloroethane (30 mL)
at 5 °C, unless otherwise noted. Yields refer to isolated compounds
precedents for the kyodai nitration.4 In contrast, methyl
naphthalene-2-carboxylate (11) underwent nitration at
both substituted and unsubstituted rings (Scheme 2).
Compared to the conventional nitration using mixed acid,
the isomer 13 was favored at the expense of the isomer
15 in the kyodai nitration (Table 2; entry 2).
Naphthalene-1,8-dicarboxylic acid diester 16 under-
went facile kyodai nitration under similar conditions to
give a mixture of 3- and 4-nitro derivatives 17 and 18,
the former being predominant. As the reaction ap-
proached near 80% conversion, the second nitration
began to start in the opposite ring, leading to three
isomeric dinitro derivatives 19-21 and a phenolic prod-
uct 22. Almost similar ease in nitration observed for
naphthalenemonocarboxylates 8 and 11 and naphtha-
lenedicarboxylate 16 under the present conditions may
be attributed to the diminished electron-withdrawing
nature of the ester function in 16 due to the steric
repulsion between two ester groups at the peri position,
which thwarts the ester carbonyl function from copla-
narity with the naphthalene ring.
b
and were not optimized. The solvent used was 25 mL. c Ni-
d
tromethane was used as the solvent. p-Toluenesulfonic acid
monohydrate.
thalate (6a ) and phthalate (1a ), in that order. Protonic
acids worked as catalyst also, but considerable amounts
of acid catalyst were necessary to attain satisfactory
conversion. Of the several protonic acids examined,
p-toluenesulfonic acid proved to be the best. Methane-
sulfonic acid and sulfuric acid were not so effective. In a
small-scale experiment, dichloromethane, acetonitrile,
hexane, and nitromethane were the solvents of choice,
but 1,2-dichloroethane was preferred in a preparative-
scale experiment for reasons of low cost and lower
volatility. Multiple nitration could not be observed even
after prolonged reaction time.
Methyl naphthalene-1-carboxylate (8) readily reacted
with nitrogen dioxide in the presence of ozone at -10 °C,
giving the nitro derivatives 9 and 10 in good yield
(Scheme 2; Table 2). Different from the above benzene-
dicarboxylates, no catalyst was necessary to attain
satisfactory conversion. As expected, the nuclear substi-
tution took place at unsubstituted ring, where the 8-nitro
isomer (10) was formed in preference to the 5-isomer (9).
The preferential attack at a position next to the electron-
withdrawing substituent is in accordance with many
In the kyodai nitration of diester 16, the 3-nitro isomer
17 was formed as the only major substitution product at
(4) (a) Suzuki, H.; Murashima, T.; Tatsumi, A.; Kozai, I. Chem. Lett.
1993, 1421-1424. (b) Suzuki, H.; Murashima, T. J . Chem. Soc., Perkin
Trans. 1 1994, 903-908. (c) Suzuki, H.; Takeuchi, T.; Mori, T. J . Org.
Chem. 1996, 61, 5944-5947.

4358 J . Org. Chem., Vol. 66, No. 12, 2001
Ta ble 2. Nitr a tion of Na p h th a len eca r boxylic Acid Ester s 8 a n d 11a
product compositionc (%)
Nose et al.
entry
substrate
reagent
reaction time (min)
T (°C)
yieldb (%)
9
10
12
13
14
15
1
2
3
8
11
NO2-O3
60
50
20
-10
-10
rt
76
80
84
23
77
NO2-O3
4
3
20
14
43
45
33
38
HNO3 (1 equiv)-H2SO4
a
b
All reactions were performed using substrate (5 mmol), N2O4 (30 mmol), O3 (10 mmol/h), and dichloromethane (30 mL). Yields refer
to isolated nitration products and were not optimized. c Determined by GC analysis.
Sch em e 3
Sch em e 4
Initially, this addition-elimination sequence would be
predominant, but as the reaction goes further, the
reaction system will gradually become acidic due to the
accumulation of nitric acid arising from the decomposi-
tion of 26 to 23. Under these conditions, the heterolytic
cleavage of dinitrogen pentaoxide (N2O5), another oxida-
tion product from nitrogen dioxide, becomes facilitated
to generate nitronium ion (Scheme 4), which adds to both
3- and 4-positions of diester 16 to give intermediate ions
23 and 24, leading to the appearance of 18 as the
increasingly important product. Thus, the kyodai nitra-
tion of diester 16 may reasonably be considered to
proceed as the competition between two different elec-
+
trophilic processes involving the nitronium ion (NO2
)
and the nitrogen trioxide radical (•NO3), respectively, both
generated in situ from nitrogen dioxide and ozone ac-
cording to Scheme 4.
Conventional nitration of diester 16 with mixed acid
gave the nitro diesters 17 and 18 nearly in a 1:1 ratio
(Table 3, entry 6). This result means that nitronium ion
attacks both 3- and 4-positions of 16 with similar ease.
Especially noteworthy is the nitration of 16 with dini-
trogen pentaoxide, where the isomer ratio of mononitra-
tion product 18/17 was found to decrease with the
progress of the reaction (Figure 1). At the initial stage,
the 4-nitro isomer 18 was predominant (18/17 ) 2.3), but
the 3-nitro isomer 17 became increasingly important as
the reaction proceeded, eventually the ratio reaching the
value near 1.0. This tendency is opposite to that observed
for the kyodai nitration, where the 3-nitro isomer 17 was
formed as the sole initial product. This intriguing phe-
nomenon may be interpreted as follows: under neutral
conditions, diester 16 would first combine with dinitrogen
pentaoxide to form a π-complex 29, which then collapses
to the 4-nitro diester 18 via an ionic intermediate 30
(Scheme 5). As the reaction proceeds, however, the
substrate 16 would increasingly be protonated by the
resulting nitric acid to form 28, in which the electron-
withdrawing ability of the ester function is strengthened
and consequently the attack by nitronium ion would
become more favored at 3-position rather than 4-position.
Thus, with the progress of the reaction, the route 16 to
28 to 23 to 17 becomes increasingly favored over the
alternative one 16 to 29 to 30 to 18, resulting in the
gradual decrease of the ratio 18/17. The final isomer ratio
was close to the value observed for the nitration of 16
with nitric acid-sulfuric acid (Table 3, entry 6). A marked
difference in the composition of the initial products
between the kyodai nitration and the nitration with
dinitrogen pentaoxide strongly suggests a possible role
the initial stage, accompanied by small amounts of a
phenolic product 22. As the reaction approached near
50% conversion, the 4-nitro isomer 18 began to appear
and became increasingly important as the reaction
proceeded. This interesting observation may be inter-
preted as follows: nitrogen dioxide (•NO2) reacts with
ozone (O3) to generate nitrogen trioxide (•NO3) as an
electron-deficient neutral radical species, which adds to
the naphthalene ring to form a radical intermediate 25
and subsequently trapped by nitrogen dioxide present in
large excess to give an adduct 26 as the sole initial
product (Scheme 3). Expulsion of nitrous acid from 26
leads to a nitrate ester 27, which readily undergoes
migration of the nitro group to give a phenolic product
22 via intramolecular nitration. The formation of phenolic
byproducts during nitration has many precedents in the
literature.5 Protonation of adduct 26 by adventitious
proton source will result in the formation of an arenium
ion 23, eventually leading to the 3-nitro isomer 17.
(5) (a) Suzuki, H.; Mori, T. J . Chem. Soc., Perkin Trans. 2 1995,
41-44. (b) Suzuki, H.; Mori, T. J . Chem. Soc., Perkin Trans. 2 1996,
677-683. Also see: (c) Suzuki, H. Synthesis 1977, 217-238. (d)
Schofield, K. Aromatic Nitration; Cambridge University Press: London,
1980.

Nonacid Nitration of Arenecarboxylic Acid Esters
Ta ble 3. Nitr a tion of Na p h th a len e-1,8-d ica r boxylic Acid Diester 16a
product compositionc (%)
J . Org. Chem., Vol. 66, No. 12, 2001 4359
entry
reagent
solvent
T (°C)
reaction time (min)
yieldb (%)
17
18
19
20
21
22
1
2
3
4
5
6
7
NO2-O3
CH2Cl2
CCl4
-10
-10
-10
-10
-10
rt
60
30
30
30
60
30
30
66
68
69
68
64
84
78
73
72
64
70
37
47
27
9
12
18
13
42
46
37
7
2
5
8
7
2
9
12
10
9
NO2-O3
NO2-O3
MeCN
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
3
NO2-O3, MeSO3H
N2O5
3
2
13
5
2
7
6
HNO3 (1 equiv)-H2SO4
HNO3 (excess)-H2SO4
3
16
rt
a
b
All reactions were performed using diester 16 (5 mmol), N2O4 (30 mmol), O3 (10 mmol/h), and dichloromethane (30 mL). Yields are
calculated by assuming all products are mononitro derivatives. c Determined by GC analysis.
films, and only prominent peaks were recorded. EI mass
spectra were determined at 70 eV and CI mass spectra were
obtained using isobutane as an ionizing gas. GC analyses were
performed on a Shimadzu GC-14A gas chromatograph, using
a CBP1-M25-025 column (25 m × 0.2 mm i.d.). Cyclododecane
was used as an internal standard, except for the case of
naphthalic acid diester 16, where 1,3,5-trinitrobenzene was
employed. Column chromatography was performed on silica
gel (silica gel 60, Merck) using hexanes-ethyl acetate as the
eluent. Elementary analyses were performed at the Micro-
analysis Laboratory, Institute of Chemical Research, Kyoto
University.
Dichloromethane and 1,2-dichloroethane were distilled from
CaH2 prior to use. All substrate esters were obtained by boiling
the corresponding carboxylic acids in an appropriate alcohol
in the presence of an acid catalyst. Nitrogen dioxide (99%
purity; impurities involve nitrogen monoxide and small amounts
of nitrogen) was used from commercial cylinders, purchased
F igu r e 1. Time course variation of the 18/17 ratios in the
nitration of diester 16 with N2O5. Reaction conditions: com-
pound 16 (3 mmol), N2O5 (10 mmol), O3 (10 mmol), CH2Cl2,
-10 °C.
from the Sumitomo Seika Co. Ltd. Dinitrogen pentaoxide was
prepared by the literature procedure.6 An apparatus (Nippon
Ozone Co Ltd., type ON-1-2) was used for the generation of
Sch em e 5
ozone at a rate of 10 mmol h-1, with an oxygen flow of 10 dm3
h-1 and an applied voltage of 80 V.
Kyod a i Nitr a tion of Ben zen ed ica r boxylic Acid Ester s
1, 4, a n d 6. Typ ica l P r oced u r e. A solution of methyl
isophthalate 4a (1.94 g; 10 mmol) in 1,2-dichloroethane (30
mL) was placed in a two-necked 50 mL flask fitted with a gas
inlet tube and a vent and cooled to 5 °C by ice bath. Liquid
nitrogen dioxide (3.0 g, 32 mmol) followed by iron(III) chloride
(0.01 g) was quickly introduced with stirring, and a stream of
ozonized oxygen was slowly passed through the gas inlet tube,
submerged just below the surface of liquid. Throughout the
reaction, ozonized oxygen was fed continuously at a low flow
rate, and the progress of the reaction was monitored by TLC.
After 1.5 h, the reaction was almost complete and excess
nitrogen dioxide was expelled by blowing air into the solution
and recovered in a cold trap for reuse. The reaction mixture
was diluted with aqueous sodium hydrogen carbonate. The
organic phase was separated, washed with water, dried
(MgSO4), and evaporated under reduced pressure to leave a
crystalline solid, which was crystallized from methanol to give
methyl 5-nitroisophthalate 5 (2.23 g, 86%), mp 123-125 °C
(lit.7 mp 123 °C).
Nitr a tion of Na p h th a len eca r boxylic Acid Ester s 8, 11,
a n d 16. Typ ica l P r oced u r e. With Nitr ogen Dioxid e-
Ozon e. A solution of methyl naphthalene-1-carboxylate 8 (0.93
g; 5 mmol) in freshly distilled dichloromethane (30 mL) was
placed in a two-necked 50 mL flask fitted with a gas inlet tube
and a vent and cooled externally to -10 °C by an ethylene
glycol bath. Liquid nitrogen dioxide (1.84 g; 20 mmol) was
quickly introduced through a pipet, and then a stream of
ozonized oxygen was slowly introduced through the gas inlet
tube, submerged just below the surface of liquid. After 1 h,
the reaction was almost complete and the mixture was diluted
with aqueous sodium hydrogen carbonate. The organic phase
was separated, washed with water, dried (MgSO4), and
of the nitrogen trioxide as the initial attacking species
in the former reaction.
Exp er im en ta l Section
Melting points were determined on a Yanagimoto hot-plate
apparatus and are uncorrected. 1H NMR spectra were recorded
in CDCl3 and/or DMSO-d6 using TMS as an internal reference,
unless otherwise mentioned. Coupling constants J are given
in Hz. Infrared spectra were measured as KBr pellets or liquid
(6) Gruenhut, N. S.; Goldfrank, M.; Cushing, M. L.; Caesar, G. V.
Inorg. Synth. 1950, 3, 78-81.
(7) Dictionary of Organic Compounds, 5th ed.; Chapman and Hall:
London, 1988.

4360 J . Org. Chem., Vol. 66, No. 12, 2001
Nose et al.
evaporated under reduced pressure to leave the crude product
as an oily residue. The product was chromatographed on silica
gel using hexanes-ethyl acetate (100:0-50:50) as the eluent
to give nitro esters 9 and 10 both as light yellow crystalline
solid.
d, J ) 8.0), 8.24 (1H, dd, J ) 1.6 8.8), 8.29 (1H, dd, J ) 1.2
7.6), 9.29 (1H, s); IR νmax (KBr)/cm-1 1730 (CdO), 1522 (NO2),
1342 (NO2), 1283, 1190, 1109, 758; MS m/z (CI) 232 (30, M+
+
1), 203 (19), 202 (100), 149 (35), 123 (23), 112 (43).
Dim eth yl 3-n itr on a p h th a len e-1,8-d ica r boxyla te (17):
white needles; mp 146-148 °C (lit.11 mp 145-146 °C); NMR
δH (CDCl3) 3.95 (3H, s, CH3), 3.99 (3H, s, CH3), 7.74 (1H, t, J
) 8.0), 8.21 (2H, m), 8.75 (1H, d, J ) 2.4), 8.94 (1H, d, J )
2.4); IR νmax (KBr)/cm-1 1728 (CdO), 1541 (NO2), 1341 (NO2),
1277, 1208; MS m/z (CI) 289 (19, M+ + 1), 258 (23), 230 (25),
212 (33), 167 (39), 149 (100), 129 (27), 101 (59).
Dim eth yl 4-n itr on a p h th a len e-1,8-d ica r boxyla te (18):
pale yellow needles; mp 126-127 °C (lit.12 mp 125-126 °C);
NMR δH (CDCl3) 3.95 (3H, s, CH3), 3.96 (3H, s, CH3), 7.77 (1H,
dd, J ) 7.2 8.8), 8.06 (1H, d, J ) 7.6), 8.12 (1H, d, J ) 8.4),
8.15 (1H, dd, J ) 1.2 6.8), 8.51 (1H, dd, J ) 1.2 8.8); IR νmax
(KBr)/cm-1 1723 (CdO), 1528 (NO2), 1439, 1348 (NO2), 1292,
1215, 1161, 1061, 1015, 866, 818, 766; MS m/z (CI) 289 (21,
M+ + 1), 258 (72), 230 (73), 212 (100), 184 (32), 169 (67), 149
(52), 126 (42), 113 (73).
Dim et h yl 3,6-n in it r on a p h t h a len e-1,8-d ica r b oxyla t e
(19): light yellow crystals; mp 202-204 °C; NMR δH (CDCl3)
4.02 (6H, s, CH3), 8.91 (2H, d, J ) 2.0), 9.12 (2H, d, J ) 2.4);
IR νmax (KBr)/cm-1 1721 (CdO), 1618, 1530 (NO2), 1337 (NO2),
1267, 1024, 903; MS m/z (CI) 334 (37, M+ + 1), 303 (100), 275
(61), 257 (88), 211 (33), 198 (38), 149 (78), 125 (33). Anal. Calcd
for C14H10N2O8: C, 50.31; H, 3.02; N, 8.38. Found: C, 50.58;
H, 3.22; N, 7.82.
Dim et h yl 3,5-d in it r on a p h t h a len e-1,8-d ica r b oxyla t e
(20): light yellow crystals; mp 189-191 °C; NMR δH (CDCl3)
3.99 (3H, s, CH3), 4.01 (3H, s, CH3), 8.27 (1H, d, J ) 8.0), 8.35
(1H, d, J ) 8.4), 8.87 (1H, d, J ) 2.4), 9.54 (1H, d, J ) 2.0); IR
νmax (KBr)/cm-1 1721 (CdO), 1537 (NO2), 1439, 1348 (NO2),
1285, 1208, 752; MS m/z (CI) 334 (29, M+ + 1), 303 (65), 275
(100), 257 (40), 211 (62), 198 (24), 184 (25), 168 (34), 140 (20),
113 (27). Anal. Calcd for C14H10N2O8: C, 50.31; H, 3.02; N,
8.38. Found: C, 50.06; H, 3.14; N, 8.36.
Dim eth yl 4,5-din itr on aph th alen e-1,8-dicar boxylate (21):
light yellow crystals; mp 243-245 °C (lit.12 mp 247-249 °C);
NMR δH (CDCl3) 3.98 (6H, s, CH3), 8.20 (2H, d, J ) 8.0), 8.32
(2H, d, J ) 8.0); IR νmax (KBr)/cm-1 1721 (CdO), 1543 (NO2),
1437, 1354 (NO2), 1287, 1206, 1044, 849, 725, 664, 511; MS
m/z (CI) 334 (5, M+ + 1), 288 (71), 260 (61), 230 (100), 199
(41), 184 (61), 169 (32), 156 (41), 149 (29), 141 (37), 115 (44),
113 (50).
Dim eth yl 4-h yd r oxy-3-n itr on a p h th a len e-1,8-d ica r box-
yla te (22): yellow crystals; mp 131-133 °C; NMR δH (CDCl3)
3.92 (3H, s, CH3), 3.94 (3H, s, CH3), 7.72 (1H, dd, J ) 7.2 8.0),
8.21 (1H, dd, J ) 1.2 7.2), 8.63 (1H, s), 8.73 (1H, dd, J ) 1.2
8.0), 12.40 (1H, s); IR νmax (KBr)/cm-1 1719 (CdO), 1545 (NO2),
1443, 1306 (NO2), 1256, 1019, 772, 748; MS m/z (CI) 305.5 (99,
M+ + 1), 274 (93), 258 (50), 230 (59), 228 (60), 185 (100), 169
(49), 149 (67), 129 (92), 127 (78), 125 (45), 115 (61), 113 (88).
Anal. Calcd for C14H11NO7: C, 55.09; H, 3.63; N, 4.59. Found:
C, 55.33; H, 3.68; N, 4.55.
With F u m in g Nitr ic Acid a n d Con cen tr a ted Su lfu r ic
Acid . To a stirred solution of naphthalene-1-carboxylic acid
ester 8 (0.465 g; 2.5 mmol) in dry dichloromethane (30 mL)
was added a mixture of fuming HNO3 (0.7 g; 11 mmol) and
concentrated H2SO4 (0.7 g) and the resulting mixture was
stirred at room temperature. After 30 min the reaction was
complete and the mixture was worked up as usual. The isomer
1
ratio was estimated by H NMR integration and the product
was isolated by chromatography on silica gel using hexanes-
ethyl acetate as eluent.
With Din itr ogen P en ta oxid e. To a stirred solution of
dinitrogen pentaoxide (1.1 g; 10 mmol) in dry dichloromethane
(30 mL) cooled to -10 °C was added naphthalene-1-carboxylic
acid ester 8 (0.23 g; 1.2 mmol), and the resulting mixture was
stirred at this temperature for 80 min. At 10 min intervals,
an aliquot was withdrawn and its composition was estimated
1
by H NMR integration.
All nitrobenzenedicarboxylic acid esters 2a ,b, 3a ,b, 5a ,c,
and 7a are known, and some are commercial products.
Spectroscopic and analytical data for less common nitro
compounds 9, 10, 12-15, and 17-22 are shown below.
Meth yl 5-n itr on a p h th a len e-1-ca r boxyla te (9): light
yellow crystals; mp 107-108 °C (lit.8 mp 107-109 °C); NMR
δH (CDCl3) 4.04 (3H, s, CH3), 7.67-7.77 (2H, m), 8.21 (1H, d,
J ) ) 7.6), 8.31 (1H, d, J ) 7.6), 8.68 (1H, d, J ) 9.2), 9.27
(1H, d, J ) 9.2); IR νmax (KBr)/cm-1 1721 (CdO), 1516 (NO2),
1339 (NO2), 1277, 1154, 1059, 791, 768; MS m/z (CI) 232 (38,
M+ + 1), 202 (100).
Meth yl 8-n itr on a p h th a len e-1-ca r boxyla te (10): light
yellow crystals; mp 96.5-97.5 °C (lit.8 mp 97-98 °C); NMR
δH (CDCl3) 3.90 (3H, s, CH3), 7.61 (1H, t, J ) 8.0), 7.67 (1H,
dd, J ) 7.2 8.0), 8.08 (1H, dd, J ) 1.2 8.0), 8.11-8.16 (3H, m);
ΙR νmax (KBr)/cm-1 1723 (CdO), 1524 (NO2), 1343 (NO2), 1277,
1209, 762; MS m/z (CI) 232 (62, M+ + 1), 200 (100), 170 (88).
Anal. Calcd for C12H9NO4: C, 62.34; H, 3.92; N, 6.06. Found:
C, 62.28; H, 3.94; N, 5.75.
Meth yl 3-n itr on a p h th a len e-2-ca r boxyla te (12): color-
less crystals; mp 195.5-196.5 °C; NMR δH (CDCl3) 4.03 (3H,
s, CH3), 8.02 (2H, dd, J ) 6.4, 8.4), 8.28 (1H, dd, J ) 1.6 8.8),
8.36 (1H, dd, J ) 1.6 8.8), 8.80 (1H, s), 8.92 (1H, d J ) 1.2); IR
νmax (KBr)/cm-1 1725 (CdO), 1528 (NO2), 1346 (NO2), 1279,
1233; MS m/z (CI) 232 (14, M+ + 1), 202 (100), 113 (29).
Meth yl 4-n itr on a p h th a len e-2-ca r boxyla te (13): light
yellow crystals; mp 93-95 °C (lit.9 mp 94-95 °C); NMR δH
(CDCl3) 4.04 (3H, s, CH3), 7.72 (1H, t, J ) 8.0), 7.85 (1H, t, J
) 8.8), 8.10 (1H, d, J ) 8.4), 8.59 (1H, d, J ) 8.8), 8.80 (1H, d,
J ) 1.6), 8.86 (1H, s); IR νmax (KBr)/cm-1 1721 (CdO), 1528
(NO2), 1298 (NO2), 770; MS m/z (CI) 233 (14), 232 (100, M+
1), 202 (23).
+
Meth yl 5-n itr on a p h th a len e-2-ca r boxyla te (14): light
yellow crystals; mp 109-110 °C (lit.9 mp 112-112.5 °C); NMR
δH (CDCl3) 4.02 (3H, s, CH3), 7.65 (1H, t, J ) 8.0), 8.26 (1H, d,
8.0), 8.30 (1H, dd, J ) 1.6 9.2), 8.36 (1H, dd, J ) 1.2 8.0), 8.66
(1H, d, J ) 9.6), 8.72 (1H, d, J ) 1.2); IR νmax (KBr)/cm-1 1732
(CdO), 1522 (NO2), 1327 (NO2), 1298, 1265, 1208, 1107, 772;
MS m/z (CI) 232 (8, M+ + 1), 202 (100), 113 (15).
Meth yl 8-n itr on a p h th a len e-2-ca r boxyla te (15): light
yellow crystals; mp 131-132 °C;10 NMR δH (CDCl3) 4.02 (3H,
s, CH3), 7.68 (1H, t, J ) 8.0), 8.03 (1H, d, J ) 8.4), 8.18 (1H,
Ack n ow led gm en t. Financial support of this work
from the Grant-in-Aid for Scientific Research (No.
08101003) of the Ministry of Education, Science, Sports
and Culture of J apan is gratefully acknowledged.
J O015619D
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