Nitration of ethyl carbamates of phenylenediamines and aniline

Article abstract of DOI:10.1080/00397910701357296

The methyl and ethyl carbamates of aniline and the diethyl dicarbamates of 1,2-, 1,3-, and 1,4-phenylenediamine were prepared. Nitration of the carbamates gave ring mono-, di-, or trinitro-derivatives in good yield. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910701357296

This article was downloaded by: [North Dakota State University]
On: 24 October 2014, At: 21:37
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office:
Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Synthetic Communications: An International
Journal for Rapid Communication of
Synthetic Organic Chemistry
Publication details, including instructions for authors and subscription
information:
http://www.tandfonline.com/loi/lsyc20
Nitration of Ethyl Carbamates of
Phenylenediamines and Aniline
Matthew C. Davis a
a Chemistry and Materials Division, Michelson Laboratory , Naval Air Warfare
Center , China Lake, California, USA
Published online: 22 Jun 2007.
To cite this article: Matthew C. Davis (2007) Nitration of Ethyl Carbamates of Phenylenediamines and Aniline,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
37:12, 2079-2089
To link to this article: http://dx.doi.org/10.1080/00397910701357296
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”)
contained in the publications on our platform. However, Taylor & Francis, our agents, and our
licensors make no representations or warranties whatsoever as to the accuracy, completeness, or
suitability for any purpose of the Content. Any opinions and views expressed in this publication
are the opinions and views of the authors, and are not the views of or endorsed by Taylor &
Francis. The accuracy of the Content should not be relied upon and should be independently
verified with primary sources of information. Taylor and Francis shall not be liable for any
losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities
whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or
arising out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any substantial
or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or
distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use
can be found at http://www.tandfonline.com/page/terms-and-conditions

Synthetic Communicationsw, 37: 2079–2089, 2007
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910701357296
Nitration of Ethyl Carbamates of
Phenylenediamines and Aniline
Matthew C. Davis
Chemistry and Materials Division, Michelson Laboratory, Naval Air
Warfare Center, China Lake, California, USA
Abstract:: The methyl and ethyl carbamates of aniline and the diethyl dicarbamates of
1,2-, 1,3-, and 1,4-phenylenediamine were prepared. Nitration of the carbamates gave
ring mono-, di-, or trinitro-derivatives in good yield.
Keywords: aniline, carbamates, nitration, phenylenediamines, urethanes
It was recently shown that a trialkyl 1,3,5-triaminobenzene tricarbamate
readily underwent nitration to give the corresponding 2,4,6-trinitro analog
in excellent yield.[1] Therefore, an investigation into the nitration of carba-
mates of aniline and the phenylenediamines seemed worthwhile.
The alkyl carbamates of aniline were prepared by two routes. The methyl
carbamate 1 was prepared by reacting aniline with methyl chloroformate
(Scheme 1).[2] The ethyl carbamate 2 was prepared by Curtius rearrangement
of benzoyl azide in good yield (Scheme 2).[3,4]
The literature contained some discrepancies regarding the nitration of
alkyl N-phenylcarbamates. Curry and Mason alleged that the nitration of 2
had not been studied previously.[5] They added, without detail, that nitration
of 2 (acetic anhydride/fuming nitric acid) gave only ethyl 2,4-dinitrophenyl-
carbamate. A thorough literature search found that the nitration of alkyl N-
phenylcarbamates had been investigated as far back as 1877 by
Losanitch,[6] 1886 by Hentschel,[7] and 1891 by van Romburgh.[8] By
Received in the USA October 27, 2006
Address correspondence to Matthew C. Davis, Chemistry and Materials Division,
(Code 498220D), Michelson Laboratory, Naval Air Warfare Center, China Lake,
CA 93555, USA. E-mail: matthew.davis@navy.mil
2079

2080
M. C. Davis
Scheme 1. a) ClCO2Me, pyridine, CHCl3; b) ClCO2Et, pyridine, CHCl3.
treating 1 with nitric/sulfuric acids, Hentschel isolated a solid melting at
1898C that he believed was tetranitrodiphenylurea[9,10] based upon combus-
tion analysis. Hentschel’s procedure was repeated by van Romburgh, who
isolated a product melting at 1928C and identified it as methyl 2,4,6-trinitro-
phenylcarbamate (6). Later, Crocker and Lowe obtained a similar substance
melting at 1928C by reacting potassium cyanate with 1-chloro-2,4,6-trinitro-
benzene (picryl chloride) in methanol.[11]
Therefore, the research of Hentschel and van Romburgh on the nitration
of alkyl N-phenylcarbamates was repeated using a mixture of concentrated
sulfuric acid and a slight excess of 100% nitric acid. When 1 was treated
under these conditions, a solid melting at 1958C was obtained in high yield.
Nuclear magnetic resonance (NMR) spectroscopy (1H, 13C) support the
trinitro derivative with the structural assignment of 6 (Scheme 3). Similar
nitration of the ethyl analog 2 gave 7 in high yield as well.
The bis-Curtius rearrangement of isophthaloyl diazide was carried out to
obtain the diethyl dicarbamate of 1,3-phenylenediamine (3) uneventfully
(Scheme 2).[12] Nitration of 3 in concentrated sulfuric acid/100% nitric acid
gave what was thought to be the unreported diethyl 1,3-diamino-2,4,6-trinitro-
phenyldicarbamate (8) (Scheme 3). At the time of this writing, the recent
patent of O’Keefe was discovered that described this reaction using a
slightly different acid mixture.[13] It was found that nitration of 3 in concen-
trated nitric acid gave the mono-nitrated product 9 with the nitro group at
the 4-position. Several attempts were made to prepare a dinitro derivative
of 3, but mixtures were obtained by thin-layer chromatography (TLC).
Scheme 2. a) NaN3, H2O, THF; b) EtOH, reflux.

The Methyl and Ethyl Carbamates of Aniline
2081
Scheme 3. a) Conc. H2SO4, 3 equiv 100% HNO3, 08C to rt; b) Conc. HNO3, 08C to rt.
The dicarbamates of 1,2- and 1,4-phenylenediamines (4 and 5) were also
prepared by reaction with ethyl chloroformate in the presence of pyridine
(Scheme 1).[14,15] It appeared from the literature that nitration of 4 and 5
had not been studied. Nitration of 4 in concentrated nitric acid at room temp-
erature gave clean mononitration at the 4-position to give 10 (Scheme 4). This
is in keeping with previous reports regarding nitration of bis-N,N0-acetamides
of phenylenediamines.[16,17] Dinitration of 4 occurred when treated with con-
centrated sulfuric acid/100% nitric acid or 100% nitric acid/acetic acid. The
product was a 1:1 mixture of the unreported 4,5- and 4,6-dinitro isomers, 11
1
and 12, based on H NMR Spectroscopy. Further nitration of 10 also gave
the same 1:1 mixture of 11 and 12. In both cases, the yield of the dinitration
products 11 and 12 was good, and no attempt was made to separate the
mixture. Curiously, the nitration of disulfonamides of 1,2-phenylenediamine
give the 4,5-dinitro isomer in good yield.[18,19]
Nitrating 5 with concentrated sulfuric acid/100% nitric acid caused con-
siderable hydrolysis of the carbamate groups (Scheme 5). TLC analysis of the
reaction showed a large amount of an orange-colored polar spot at the origin.
The product from nitration at the 2-position (13) could be isolated under these
conditions by brief treatment at 08C. A better method to prepare 13 was to treat
a solution of 5 in acetic acid with 1 equivalent of concentrated nitric acid at
room temperature. This result parallels the studies on bis-N,N0-acetamides
of phenylenediamines.[16,17] Dinitration of 5 to give the unreported 14 could
be achieved simply by stirring in concentrated nitric acid at room temperature.
NMR spectroscopy (13C) proved that the nitro groups of 14 are in the 2,5-
positions. Reaction of 13 with concentrated nitric acid also gave 14.

2082
M. C. Davis
Scheme 4. a) Conc. HNO3; b) Conc. H2SO4, 100% HNO3.
In conclusion, the diethyl carbamates of the phenylenediamines and
aniline were prepared. The carbamates generally gave clean reactions under
nitration conditions. The carbamates of aniline and 1,3-phenylenediamine
readily underwent nitration to give trinitro products. Nitration of 1,4-phenyle-
nediamine dicarbamate gave the 2,5-dinitro isomer selectively. Initial
nitration of 1,2-phenylenediamine dicarbamate gave the 4-nitro isomer, and
subsequent nitration produced a mixture of 4,5- and 4,6-dinitro isomers.
Scheme 5. a) HOAc, 1 equiv conc. HNO3; b) Conc. HNO3.

The Methyl and Ethyl Carbamates of Aniline
EXPERIMENTAL
2083
Melting points were collected on an electrothermal capillary melting-point
apparatus and are not corrected. All NMR spectra were obtained on a
Bruker AC-200 spectrometer (1H at 200 MHz, 13C at 50 MHz) and are refer-
enced to solvent or tetramethylsilane. Benzoyl chloride, isophthaloyl dichlo-
ride, and 1,2-, 1,3-, and 1,4-phenylenediamines, and all other reagents, were
purchased from Aldrich Chemical Co. (Milwaukee) and used as received.
Elemental analysis was performed by Atlantic Microlab, Inc. (Norcross, GA).
Methyl N-Phenylcarbamate (1)
A 1-L Erlenmeyer flask equipped with magnetic stirbar was charged with
200 mL of CHCl3, 9.3 g of aniline (0.1 mol), and 10.27 g of pyridine
(0.13 mol, 1.3 equiv). The mixture was stirred in an ice bath while 11.28 g
of methyl chloroformate (9.2 mL, 0.12 mol, 1.2 equiv) was added dropwise
over 1 h. The internal temperature remained at ꢀ128C. After checking the
reaction by TLC (SiO2; hexanes/Et2O) for completion, the mixture was
poured onto 300 g of crushed ice and H2O. The organic phase was washed
three times with 200-mL portions of H2O. The organic layer was washed
with brine and then dried with anhydrous MgSO4. The filtrate was rotary evap-
orated, leaving 13.96 g of an oil that slowly crystallized under vacuum. The
crude was recrystallized from hexanes to give 12.7 g of the title compound
as colorless plates (84%). Mp 43–458C (lit.[2] 478C). dH (CDCl3): 7.39 (d,
J ¼ 8.0 Hz, 2H), 7.26 (t, J ¼ 7.6 Hz, 2H), 7.08 (bs, 1H), 7.03 (t,
J ¼ 7.0 Hz, 2H), 3.73 (s, 3H); dC (CDCl3): 154.42, 138.07, 129.04, 123.46,
118.96, 52.33.
Ethyl N-Phenylcarbamate (2)
A 250-mL round-bottomed flask equipped with magnetic stirbar was charged
with 19 g of NaN3 (0.29 mol, 5 equiv) and 50 mL of H2O. The mixture was
allowed to stir until all the solids dissolved. The mixture was cooled in an
ice bath, and a solution of 8 g of benzoyl chloride (0.057 mol) in 20 mL of
THF was added over 15 min. After stirring in the ice bath for 1 h, the
mixture was extracted twice with 100-mL portions of Et2O. The organic
phases were collected and washed with 50 mL of H2O, washed with 50 mL
of saturated aqueous Na2CO3, and finally 50 mL of brine. After drying over
MgSO4, the filtrate was transferred to a 500-mL of round-bottomed flask,
and the solvent was rotary evaporated (10 Torr, rt), leaving a light yellow
semicrystalline mass of benzoyl azide [dH (CDCl3): 8.07–7.97 (m, 2H),
7.61 (tt, J ¼ 7.5 and 1.4 Hz, 1H), 7.44 (tt, J ¼ 7.2 and 1.7 Hz, 2H); dC
(CDCl3): 172.48, 134.37, 130.74, 129.52, 128.71]. Ethanol (200 mL) and a

2084
M. C. Davis
stirbar were added to the flask, and the solution was refluxed for 12 h.
Evaporation of the solvent left a pale green oil that slowly crystallized. The
product was sufficiently pure (8.1 g, 86%). Mp 45–478C (lit.[3] 528C). dH
(CDCl3): 7.45–7.24 (m, 4H), 7.05 (t, J ¼ 7.5 Hz, 1H), 6.76 (bs, 1H), 4.23
(q, J ¼ 7.1 Hz, 2H), 1.31 (t, J ¼ 7.5 Hz, 3H); dC (CDCl3): 153.88, 138.19,
129.19, 129.15, 123.51, 118.91, 61.35, 14.70.
Diethyl 1,3-Phenylenediamine Dicarbamate (3)
A 500-mL round-bottomed flask equipped with magnetic stirbar was charged
with 70 mL of H2O, followed by 25.7 g of NaN3 (0.396 mol, 10 equiv). The
mixture was stirred in an ice bath until complete dissolution. An addition
funnel was attached and charged with a solution of 8 g of isophthaloyl dichlo-
ride (0.039 mol) in 30 mL of THF. The addition was made over 15 min.
Copious white solids began to form, and the mixture was stirred for 1 h in
the ice bath. Ether (200 mL) was added, and the solids slowly dissolved. The
aqueous phase was extracted twice more with 100-mL portions of Et2O. The
organic phases were collected and washed twice with 200-mL portions of
H2O. The organic phase was washed with 100 mL of saturated aqueous
Na2CO3 and then 200 mL of brine and dried over anhydrous MgSO4. The
Et2O was rotary evaporated (10 Torr, rt) leaving 8.45 g of isophthaloyl
diazide (98% of theory) [dH (CDCl3): 8.65 (t, J ¼ 1.7 Hz, 1H), 8.27 (dd,
J ¼ 7.8 and 1.7 Hz, 2H), 7.59 (td, J ¼ 7.9 and 0.7 Hz, 1H); dC (CDCl3):
171.64, 134.87, 131.58, 130.55, 129.47] as a white solid. Absolute EtOH
(500 mL) and a stirbar were added to the flask, and the mixture was refluxed
for 18 h. The mixture was rotary evaporated, leaving 8.6 g of an off-white
solid. Recrystallization from MeCN gave the title compound as a white
powder (6.7 g, 67%). Mp 140–1428C (lit.[12] 143–1458C). dH (CDCl3): 7.59
(t, J ¼ 1.8 Hz, 1H), 7.33–7.09 (m, 3H), 6.93 (bs, 2H), 4.26 (q, J ¼ 7.1 Hz,
4H), 1.33 (t, J ¼ 7.4 Hz, 6H); dH (DMSO): 9.54 (s, 2H), 7.69 (s, 1H), 7.20–
7.01 (m, 3H), 4.11 (q, J ¼ 6.5 Hz, 4H), 1.23 (t, J ¼ 7.2 Hz, 6H); dC
(CDCl3): 153.86, 138.98, 129.72, 113.62, 109.10, 61.42, 14.69; dC (DMSO):
153.51, 139.62, 128.73, 112.65, 108.71, 60.03, 14.52.
Diethyl N,N0-1,2-Phenylenediamine Dicarbamate (4)
A 500-mL Erlenmeyer flask equipped with magnetic stirbar was charged
with 20 g of 1,4-phenylenediamine (0.185 mol), 44 g of pyridine (44.98 mL,
0.55 mol, 3 equiv), and 200 mL of CHCl3. The mixture was stirred in an ice
bath while 39 mL of ethyl chloroformate (43.9 g, 0.41 mol, 2.2 equiv) was
added over 30 min. The mixture was stirred at rt for 1 h. The mixture was
washed twice with 200-mL portions of H2O and 200 mL of brine and then
dried over anhydrous MgSO4. The solvent was rotary evaporated, leaving a

The Methyl and Ethyl Carbamates of Aniline
2085
crude solid (44.3 g, 95%). Recrystallization from EtOH gave the title compound
as white needles. Mp 79–818C (lit.[14] 888C). dH (CDCl3): 7.52–7.41 (m, 2H),
7.21 (bs, 2H), 7.16–7.04 (m, 2H), 4.21 (q, J ¼ 7.2 Hz, 4H), 1.29
(t, J ¼ 7.0 Hz, 6H); dC (CDCl3): 155.03, 130.13, 125.65, 124.42, 61.75, 14.62.
Diethyl N,N0-1,4-Phenylenediamine Dicarbamate (5)
A procedure similar to 4 was used. 1,4-Phenylenediamine (20 g, 0.185 mol),
44 g of pyridine (44.98 mL, 0.55 mol, 3 equiv), 39 mL of ethyl chloroformate
(43.9 g, 0.41 mol, 2.2 equiv), and 200 mL of CHCl3 gave 42 g of crude solid
(90%). Recrystallization from EtOH gave the title compound as chunky, clear
crystals. Mp 196–1998C (lit.[15] 1968C). dH (DMSO): 9.45 (s, 2H), 7.36
(s, 4H), 4.12 (q, J ¼ 6.9 Hz, 4H), 1.25 (t, J ¼ 7.3 Hz, 6H); dC (DMSO):
153.63, 133.97, 59.98, 14.54.
Methyl N-2,4,6-Trinitrophenylcarbamate (6)
A 500-mL round-bottomed flask equipped with magnetic stirbar was charged
with 50 mL of conc. H2SO4. The flask was cooled in an ice bath before adding
12.7 g of 1 (0.084 mol) in one portion. The cooling bath was removed to allow
the solids to dissolve. The cooling bath was replaced, and 11.3 mL of 100%
HNO3 (17 g, 0.27 mol, 3.2 equiv) was added dropwise by addition funnel
over 30 min. The color of the mixture became dark brown. Shortly after all
the HNO3 was added, a solid precipitated and the mixture solidified. The
cooling bath was removed, and the mixture was stirred at rt for 8 h. The
mixture was poured onto 1 L of vigorously stirred crushed ice and H2O.
The tan solid was collected on a coarse-porosity glass frit and washed with
copious H2O. The crude solid (24 g, quant.) was air dried on the frit and
then recrystallized from 1,4-dioxane/EtOH to give the title compound as
tan-colored needles. Mp 195–1978C (lit.[8] 1928C). dH (DMSO): 10.68
(s, 1H), 8.96 (s, 1H), 3.71 (s, 3H); dH (CDCl3): 9.55 (bs, 1H), 9.15 (s, 2H),
3.88 (s, 3H); dC (DMSO): 153.78, 144.25, 143.08, 130.82, 124.95, 53.65.
Elemental analysis calculated for C8H6N408: C, 33.58; H, 2.11; N, 19.58.
Found: C, 33.88; H, 2.11; N, 19.52.
Ethyl N-2,4,6-Trinitrophenylcarbamate (7)
A 500-mL round-bottomed flask equipped with magnetic stirbar was charged
with 30 mL of conc. H2SO4, and the flask was cooled in an ice bath. In one
portion, 6.08 g of 2 (0.037 mol) were added, and the mixture was stirred
until all solids dissolved. Over 30 min, 5 mL of 100% HNO3 (0.12 mol,
3.2 equiv) were added dropwise, keeping the internal temperature at or

2086
M. C. Davis
colder than 108C. The mixture became dark brown, and the cooling bath was
removed. After stirring at rt for 8 h, the mixture was poured onto 500 g of
crushed ice. After the ice had melted, the light yellow precipitate was
filtered on a medium-porosity glass frit, washed several times with H2O,
and air-dried on the frit (11 g, quant.). The crude product was recrystallized
from EtOH to give the title compound as pale yellow, glistening plates
(9.2 g, 83%). Mp 141–1438C (lit.[8] 1448C). dH (CDCl3): 9.49 (bs, 1H),
9.11 (s, 2H), 4.29 (q, J ¼ 7.2 Hz, 2H), 1.36 (t, J ¼ 3H); dC (CDCl3):
152.11, 142.35, 141.32, 133.24, 125.54, 64.50, 14.37. Elemental analysis
calculated for C9H8N408: C, 36.01; H, 2.69; N, 18.66. Found: C, 36.13; H,
2.71; N, 18.58.
Diethyl N,N0-1,3-Diamino-2,4,6-trinitrophenyl Dicarbamate (8)
A 50-mL round-bottomed flask equipped with magnetic stirbar was charged
with 5 mL of conc. H2SO4. The flask was placed in an ice bath to stir until
cold. In a single portion, 3 g of 3 (3.9 mmol) were added, and the solids
were allowed to dissolve. Nitric acid (100%, 1.5 mL, 3.2 equiv) was added
dropwise over 5 min. The color immediately became dark red. The cooling
bath was removed, and the mixture was stirred at rt for 30 min. After
becoming warm, the color changed to light brown. The mixture was poured
onto 100 g of crushed ice and H2O. The pale yellow precipitate was
collected on a coarse-porosity glass frit, washed well with H2O, and air-
dried (4.6 g, quant.). Recrystallization of the crude solid from EtOH gave
2.6 g of the title compound as an off-white powder (56%). Mp 227–2308C
(dec., lit. 225–2288C[13], 2268C[20]). dH (DMSO): 10.62 (s, 2H), 8.86
(s, 1H), 4.13 (q, J ¼ 7.1 Hz, 4H), 1.21 (t, J ¼ 7.0 Hz, 6H); dC (DMSO):
153.46, 143.53, 141.35, 129.54, 125.09, 62.23, 14.18. Elemental analysis
calculated for C12H15N5O10: C, 37.22; H, 3.38; N, 18.08. Found: C, 36.93;
H, 3.41; N, 1786.
Diethyl N,N0-1,3-Diamino-4-nitrophenyl Dicarbamate (9)
A 1g sample of 3 was added to 10 mL of conc. nitric acid. After stirring 1h,
the solution was poured onto crushed ice and water. The pale yellow solid was
collected on a medium porosity glass frit. This was recrystallized from
EtOH, yielding pale yellow crystals. Mp 120–1228C. dH (CDCl3): 10.11
(s, 1H), 8.51 (s, 1H), 8.22 (d, J ¼ 9.3 Hz, 1H), 7.53 (s, 1H), 7.47 (dd,
J ¼ 9.3 and 2.2 Hz, 1H), 4.29 (q, J ¼ 6.7 Hz, 2H), 4.26 (q, J ¼ 7.1 Hz, 2H),
1.35 (t, J ¼ 7.5 Hz, 3H), 1.33 (t, J ¼ 7.1 Hz, 3H); dC (CDCl3): 153.57,
153.14, 145.83, 137.21, 130.88, 128.17, 111.77, 107.90, 62.29, 62.20,
14.58, 14.55.

The Methyl and Ethyl Carbamates of Aniline
2087
Diethyl N,N0-4-Nitro-1,2-diaminobenzene Dicarbamate (10)
A 100-mL Erlenmeyer flask equipped with a magnetic stirbar was charged
with 10 mL of conc. HNO3. The mixture was stirred in an ice bath, and 1 g
of 4 (3.9 mmol) was added in one portion. The cooling bath was removed,
and the mixture was stirred at rt for 4 h. After this time, a tan solid had pre-
cipitated. The mixture was poured onto 100 g of crushed ice and H2O, and
a tan solid precipitated (850 mg, 74%). The solid was recrystallized from
EtOH to give the title compound as soft white needles. Mp 173–1758C. dH
(CDCl3): 8.32 (d, J ¼ 2.7 Hz, 1H), 8.10 (dd, J ¼ 9.2 and 2.4 Hz, 1H), 7.99
(d, J ¼ 9.0 Hz, 1H), 7.39 (bs, 1H), 6.78 (bs, 1H), 4.3 (q, J ¼ 7.0 Hz, 2H),
4.29 (q, J ¼ 7.2 Hz, 2H), 1.36 (t, J ¼ 7.2 Hz, 3H); dH (DMSO): 9.29
(s, 1H), 9.18 (s, 1H), 8.44 (d, J ¼ 2.2 Hz, 1H), 7.99–7.84 (m, 2H), 4.15
(q, J ¼ 7.1 Hz, 2H), 4.14 (q, J ¼ 7.1 Hz, 2H), 1.24 (t, J ¼ 7.0 Hz, 6H); dC
(DMSO): 154.09, 153.61, 142.52, 136.36, 129.21, 121.92, 119.49, 118.40,
61.19, 61.03, 14.39, 14.36.
Diethyl 4,5-Dinitro-1,2-diaminobenzenedicarbamate (11) and
Diethyl 4,6-Dinitro-1,2-diaminobenzenedicarbamate (12)
A 50-mL Erlenmeyer flask equipped with magentic stirbar was charged with
10 mL of conc. H2SO4 and cooled in an ice bath. In one portion, 1 g of 4
(3.9 mmol) was to the flask, and the cooling bath was removed. After most
of the solids had dissolved, the cooling bath was replaced. Nitric acid
(100%, 0.4 mL, 9.8 mmol, 2.5 equiv) was added dropwise over 2 min. The
cooling bath was removed, and the mixture was stirred at rt for 1 h. The
mixture was poured onto 100 g of cracked ice, and the tan solid was
1
collected on a coarse frit and air-dried (1.3 g, 96%). H NMR showed the
product was a 1:1 mixture of the title compounds: diethyl 4,5-dinitro-1,2-dia-
minobenzenedicarbamate (11) dH (DMSO): 9.73 (s, 2H), 8.52 (s, 2H), 4.21
(q, J ¼ 7.4 Hz, 4H), 1.29 (t, J ¼ 7.0 Hz, 6H); and diethyl 4,6-dinitro-1,2-dia-
minobenzenedicarbamate (12) dH (DMSO): 9.78 (bs, 1H), 9.6 (bs, 1H), 8.85
(d, J ¼ 2.6 Hz, 1H), 8.39 (d, J ¼ 2.6 Hz, 1H), 4.11 (q, J ¼ 7.4 Hz, 4H), 1.23
(t, J ¼ 7.4 Hz, 6H).
Diethyl N,N0-2-Nitro-1,4-diaminobenzene Dicarbamate (13)
A 100-mL Erlenmeyer flask equipped with magnetic stirbar was charged with
20 mL of glacial HOAc, 1 g of 5 (3.9 mmol), and 387 mL of conc. HNO3
(270 mg, 4.3 mmol, 1.1 equiv). The mixture was stirred at rt for 3 h. A bright
yellow solid had precipitated during the reaction. The mixture was poured
onto 100 g of crushed ice and H2O. The bright yellow solid was collected on a
coarse-porosity glass frit, washed with H2O, and air dried (1.15 g, 97%). The

2088
M. C. Davis
crude product was recrystallized from EtOH to give the title compound as fine
yellow needles. Mp 143–1458C. dH (CDCl3): 9.65 (s, 1H), 8.51
(d, J ¼ 9.3 Hz, 1H), 8.35 (d, J ¼ 2.9 Hz, 1H), 7.64 (dd, J ¼ 9.6 and 2.6 Hz,
1H), 6.78 (s, 1H), 4.28 (q, J ¼ 7.1 Hz, 2H), 4.27 (q, J ¼ 7.4 Hz, 2H), 1.36 (t,
J ¼ 7.1 Hz, 3H), 1.34 (t, J ¼ 7.1 Hz, 3H); dC (CDCl3): 153.68, 153.52,
136.39, 133.10, 131.06, 126.58, 121.81, 115.27, 62.15, 61.95, 14.68, 14.61.
Diethyl N,N0-2,5-Dinitro-1,4-diaminobenzene Dicarbamate (14)
A 250-mL Erlenmeyer flask equipped with magnetic stirbar was charged with
50 mL of conc. HNO3 and stirred in an ice bath. After cooling down, 5 g of 5
(0.0198 mol) were added in one portion. The color immediately became
yellow, and the cooling bath was removed. The solids dissolved within
15 min, making an orange solution. Then, suddenly, a bright yellow solid pre-
cipitated. The mixture was warmed and stirred in a 558C bath for 30 min
before pouring onto 500 g of crushed ice and H2O. The light yellow precipitate
was harvested on a coarse-porosity glass frit and washed with copious H2O.
The solid was air dried on the frit (6.5 g, 96%) and recrystallized from
EtOH to give the title compound as fine yellow needles. Mp 204–2068C.
dH (CDCl3): 8.45 (s, 2H), 8.12 (s, 2H), 4.27 (q, J ¼ 7.2 Hz, 4H), 1.35
(t, J ¼ 7.0 Hz, 6H); dH (DMSO): 9.99 (s, 2H), 7.78 (s, 2H), 4.12
(q, J ¼ 7.1 Hz, 4H), 1.22 (t, J ¼ 6.9 Hz, 6H); dC (DMSO): 153.89, 137.43,
129.89, 128.35, 61.47, 14.26.
ACKNOWLEDGMENTS
Financial support from the Office of Naval Research is gratefully acknow-
ledged. Support from the librarians of the Technical Library (NAWCWD)
in collecting Ref. 7 and 12 is gratefully acknowledged.
REFERENCES
1. Davis, M. C. Tricarbamate of 1,3,5-triaminobenzene via Curtius rearrangement of
trimesic acid and subsequent nitration. Synth. Commun. 2007, 37, 1457–1462.
¨ ¨ ¨ ¨
2. Hentschel, W. Ueberfu¨hrung von carbanilsaureather in amidobenzoesauer. Chem.
Ber. 1885, 18, 977–981.
3. Curtius, Th. Hydrazide und azide organischer sauren, VII: Abhandlung, XXXI: Ueber
¨
benzazid und einige saureazide der fettreihe. J. Prakt. Chem. 1895, 52, 210–226.
¨
4. Curtius, Th. Umlagerung von saureaziden, R.CON3, in derivate alkylirter amine
¨
(ersatz von carboxyl durch amide). Chem. Ber. 1894, 27, 778–781.
5. Curry, H. M.; Mason, J. P. Carbamates and N-nitrocarbamates. J. Amer. Chem.
Soc. 1951, 73, 5043–5046.

The Methyl and Ethyl Carbamates of Aniline
2089
¨
6. Losanitch, S. M. Ueber die einwirkung von saltpetersaure auf zusammengesetzte
harnstoffe, guanidine und urethane. Chem. Ber. 1877, 10, 690–691.
¨
7. Hentschel, W. Ueber einige abkommlinge des carbanilsauren methyls. J. Prakt.
Chem. 1886, 34, 423–427.
8. Romburgh, M. P. van. Sur l’acide azotique sur les ethers de l’acide phenylamido-
´
formique. Recl. Trav. Chim. Pays-Bas 1891, 10, 135–143.
´
9. The melting point of 2,20,4,40-tetranitrodiphenylurea is 2188C: Reudler, J. F. L.
´ ´
L’ action de l’acide azotique sur les phenylurees. Recl. Trav. Chim. Pays-Bas
1914, 33, 35–84.
10. Kogan, I. M.; Kutepov, D. F. The nitration of diphenylurea (carbanilide). J. Gen.
Chem. USSR (Engl. Transl.) 1951, 21, 1419–1424.
11. Crocker, J. C.; Lowe, F. H. Picryl derivatives of urethanes and thiourethanes.
J. Chem. Soc. 1904, 35, 646–654.
¨
12. Curtius, Th.; Davidis, E. Hydrazide und azide organischer sauren, part XIII: Die
¨
hydrazide und azide der phtalsauren. J. Prakt. Chem. 1896, 54, 66–87.
13. O’Keefe, D. M. DATB and its bis-urethane. U.S. Patent 4,833,265, May 23, 1989.
14. Snape, H. L. Certain aromatic cyanates and carbamates. J. Chem. Soc. 1886, 49,
254–260.
¨
15. Schiff, H.; Ostrogovich, A. Uramide, urethane und oxamathane der p- und m-phe-
nylendiamine. Liebigs Ann. Chem. 1896, 293, 371–388.
¨
16. Ladenburg, A. Ueber das verhalten der diamine gegen salpetrige saure. Chem. Ber.
1884, 17, 147–150.
17. Phillips, M. A. The formation of 2-methylbenzimidazoles. J. Chem. Soc. 1928,
172–177.
18. Cheeseman, G. W. H. Quinoxalines and related compounds, part VI. Substitution
of 2,3-dihydroquinoxaline and its 1,4-dimethyl derivative. J. Chem. Soc. 1962,
1170–1176.
19. Siri, O.; Braunstein, P. Tuning the synthesis of a dinitroaromatic towards a new
trinitroaromatic stabilized energetic material. New J. Chem. 2005, 29, 75–79.
20. Lorang, H. F. J. Nitration of a-4-methoxy- and a-4-ethoxy-phenyl-b-ethylurea.
Recl. Trav. Chim. Pays-Bas 1927, 46, 635–652.