Reaction of N,N,N′,N ′-tetramethyloxamide with bromine

Article abstract of DOI:10.1023/A:1012314609647

Reaction of bromine with N,N,N′,N′-tetramethyloxamide results in dibromobromate of 3-methyl-5-dimethylimmoniooxazolidin-4-one (in an open system) and in dibromobromate of 4,5,-dibromo-1,3-dimethylimidazolium (in a closed system).

Full text of DOI:10.1023/A:1012314609647

Russian Journal of Organic Chemistry, Vol. 37, No. 2, 2001, pp. 198 201. Translated from Zhurnal Organicheskoi Khimii, Vol. 37, No. 2, 2001,
pp. 211 214.
Original Russian Text Copyright
2001 by Kanibolotskii, Mikhailov, Savelova.
Reaction of N,N,N ,N -Tetramethyloxamide with Bromine
A. L. Kanibolotskii, V. A. Mikhailov, and V. A. Savelova
Litvinenko Institute of Physical Organic and Coal Chemistry, Ukrainian Academy of Sciences, Donetsk, 83114 Ukraine
Received April 30, 1999
Abstract Reaction of bromine with N,N,N ,N -tetramethyloxamide results in dibromobromate of
3-methyl-5-dimethylimmoniooxazolidin-4-one (in an open system) and in dibromobromate of 4,5,-dibromo-
1,3-dimethylimidazolium (in a closed system).
In the reaction of bromine and tertiary amides (A)
the corresponding immonium salt (B) is assumed to
be one among the first intermediates [1 3].
X = C, PN(Me)2.
The high reactivity of the immonium cation due to
the presence of a strong electrophilic center in
compounds B arising in particular from dialkylacet-
amide [1], hexamethylphosphoramide [2], and di-
methylcarbamoyl chloride [3] precludes the isolation
of the immonium salt (B) from the reaction mixture
Due to high electrophilicity of the carbon atom in
and its characterization as an individual compound.
position 5 the hydrolysis of salt II occurs even at its
At most only the products of immonium cation trans-
formations are obtained [1 3].
1
dissolution in dimethyl sulfoxide. In the H and 13C
NMR spectra of compound II in this solvent are
observed signals of the hydrolysis products. As an
example an H NMR spectrum in DMSO-d6 is shown
on Fig. 2. In the more thoroughly dried dimethyl
sulfoxide and at reducing time between the sample
preparation and the spectrum recording the cor-
responding signals were less intensive but we failed
to eliminate them completely.
We found an unusual stabilization mode of the
above immonium salt. It consists in a cyclization of
the immonium cation by an intramolecular nucleo-
philic attack of the amide carbonyl at the carbenium
carbon.
1
Reaction of N,N,N ,N -tetramethyloxamide (I)
with bromine in an open system (boiling of a mixture
amide I bromine at reflux with gradual addition of
bromine throughout the process) afforded 3-methyl-5-
N,N-dimethylimmoniooxazolidin-4-one (II). The
latter was isolated and characterized by elemental
The detected stabilization mode of the immonium
salt by intramolecular attack on electrophilic center
of the adjacent nucleophilic atom opens up wide
opportunities for new synthesis of heterocyclic com-
pounds.
1
1
analysis, H and 13C NMR spectra. In the H NMR
spectrum of the reaction mixture appeared only
signals of the reaction product II and the initial amide
(Fig. 1). The attempt to obtain from salt II the cor-
responding bromide by halogen elimination with
ethylene in methanol afforded hydrolysis products that
were characterized as dimethylammonium bromide
(III) and 3-methyloxazolidine-4,5-dione (IV).
In a sealed ampule at long heating the reaction
takes a more complicated course and affords 4,5-di-
bromo-1,3-dimethylimidazolium dibromobromate (V).
The different outcome of the process in an open
system and in sealed ampule may be understood as
more severe halogenation conditions in the closed
1070-4280/01/3702-0198$25.00 2001 MAIK Nauka/Interperiodica

REACTION OF N,N,N ,N -TETRAMETHYLOXAMIDE
199
Fig. 1. 1H NMR spectrum of the reaction mixture N,N,N ,N -tetramethyloxamide bromine for an experiment carried out in
an open system.
Fig. 2. 1H NMR spectrum of dibromobromate of 3-methyl-5-N,N-dimethylimmoniooxazolidin-4-one (II) in DMSO-d6 [in
the spectrum appear the signals from hydrolysis products: dimethylammonium bromide (III) and 3-methyloxazolidine-4,5-dione
(IV)].
system. The transformations resulting in compound
V may occur as follows: The excess bromine at high
temperature favors dication VI formation; the latter
suffers nucleophilic attack by bromide ion with
rupture of C(O) C(O) bond to yield immonium cation
VII and ylide VIII. The possibility of imidazole cycle
formation is due to the interaction between the above
intermediates. The further transformations are similar
to the known reaction between N,N-dimethylcarb-
amoyl chloride with bromine [3]. The composition
and structure of salt V was confirmed by elemental
C6H12N2O2 + 5 Br2
C5H7N2Br5 + CO2 + 5 HBr
The maximum yield of compound V was obtained
just at the ratio amide (I) : halogen equal to 1: 5.
EXPERIMENTAL
1H NMR spectra were registered on spectrometers
Gemini-200 (operating frequency 200 MHz) and
Tesla BS-467 (60 MHz);
recorded on Gemini-200 instrument at 50.3 MHz,
internal reference TMS. UV spectra were measured
on a spectrophotometer Specord UV-Vis. The content
of the active halogen was determined by iodometric
13
C NMR spectra were
1
analysis, H and 13C NMR spectra.
The overall stoichiometry of the process cor-
responds to the following equation:
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 2 2001

200
KANIBOLOTSKII et al.
titration with 0.01 N sodium thiosulfate water
solution.
Reaction between bromine and N,N,N ,N -tetra-
methyloxamide in an open system. Amide I (1.8 g)
was heated to 120 C (the temperature within reaction
mixture) at atmospheric pressure and under protection
from air moisture, and 3.3 ml of bromine was added
dropwise thereto. The rate of halogen addition was so
controlled that the reaction mixture remained at 110
120 C. When the mixture could the excess bromine
N,N,N ,N -Tetramethyloxamide (I) was obtained
by a known procedure [4], recrystallized from ether,
mp 81 82 C (mp 77 79 C [4]). Just before the
experiment amide I was dried in a vacuum of an oil
pump at 40 60 C.
was distilled off. On completing bromine addition
the reaction mixture was heated to 120 C for 10
12 h. To the end of the process the weight of the
reaction mixture amounted to 7.8 g, bromine
content to 52 58%, hydrogen bromide 5 6%. The
mixture was maintained in a vacuum at room
temperature till it solidified. At this point the
overall weight was 5.2 g, bromine content 37%,
hydrogen bromine amount 10%. The residue was
filtered off and washed with methanol. Yield of
3-methyl-5-N,N-dimethylimmoniooxazolidin-4-one
dibromobromide (II) 1.95 g (43%), mp 108 110 C.
1H NMR spectrum (DMSO-d6, , ppm): 3.03 s (3H,
NMe), 3.36 s (3H, = N + Me), 3.74 s (3H, = N + Me),
5.74 s (2H, CH2). In the spectrum appear signals
from hydrolysis products (Fig. 2): salt III [2.54 t
3
(6H, J 5.58 Hz) and 8.2 br.s] and compound IV.
13C NMR spectrum (DMSO-d6, C, ppm): 28.085
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 2 2001

REACTION OF N,N,N ,N -TETRAMETHYLOXAMIDE
201
(NMe); 37.195 (=N+ Me), 40.882 (3H, = N + Me),
151.400 (C=O), 161.179 (C=N+ ). In the 13C NMR
spectrum as well as in the H NMR spectrum appear
the signals of hydrolysis products: dimethylammon-
ium cation (34.52 ppm) and compound IV. UV
Reaction between bromine and N,N,N ,N -tetra-
methyloxamide in a closed system. A sealed ampule
containing 0.55 g of amide (I) and 0.98 ml of
bromine was heated to 120 C for 280 h. Then the
ampule was cooled in liquid nitrogen and opened, the
volatiles were distilled off in a vacuum of water-jet
pump. The weight of volatiles was 0.7 g. To the
residue was added 1.5 ml of methanol, and the
separated yellow precipitate was filtered off, washed
with methanol (1 ml), and dried on the filter. Yield
0.46 g (27% according to the presumed stoichio-
metry). Characteristics of the compound are in
agreement with the previously reported ones [3].
1
spectrum II in acetonitrile:
absorption of anion Br3 [5, 6]). Found, %: C 19.09;
2.73; Br 62.30; Br2act 41.80; 7.29.
270 nm ( 55000,
max
H
N
C6H11Br3N2O2. Calculated, %: C 18.82; H 2.90; Br
62.61; Br2act 41.74; N 7.32.
1
The H NMR spectrum of the reaction mixture
obtained by bromine addition at 120 C for 205 min
and keeping it at the same temperature for 320 min is
presented on Fig. 1 (the reaction mixture contains
53.83% of bromine and 5.78% of HBr).
REFERENCES
1. Mikhailov, V.A., Yufit, D.S., and Struchkov, Yu.T.,
Zh. Obshch. Khim., 1992, vol. 62, no. 2,
pp. 399 405.
2. Kanibolotskii, A.L., Yufit, D.S., Mikhailov, V.A.,
Struchkov, Yu.T., and Savelova, V.A., Zh. Org.
Khim., 1993, vol. 29, no. 6, pp. 1105 1110.
3. Kanibolotskii A.L., Mikhailov V.A., and Savelo-
va V.A., Zh. Org. Khim., 1996, vol. 32, no. 10,
pp. 1589 1592.
4. Campaigne, E., Skowronski, G., and Rogers, R.B.,
Synth. Commun., 1973, vol. 3, no. 5, pp. 325 332.
5. Popov, A.I. and Swensen, R.F., J. Am. Chem. Soc.,
1955, vol. 77, no. 14, pp. 3724 3726.
6. Gabes, W. and Stufcens, D.J., Spectr. Acta, 1974,
vol. 30A, no. 9, pp. 1835 1841.
Debromination of 3-methyl-5-N,N-dimethyl-
immoniooxazolidin-4-one dibromobromate (II).
Through a mixture of 1.35 g of compound II and
3 ml of methanol was passed a flow of ethylene till
the particular color from tribromide ion disappeared.
On distilling off the solvent we obtained 0.9 g of oily
residue that slowly crystallized. The recrystallization
from methanol afforded colorless crystalline com-
1
pound, mp 106 C. H NMR spectrum (DMSO-d6, ,
ppm): 2.95 s (3H, NMe), 5.34 (2H, CH2). 13C NMR
spectrum (DMSO-d6, C, ppm): 28.059 (NMe),
77.612 (CH2), 152.288 (C=O), 160.260 [C(O)O ].
Found, %: C 41.49; H 4.26; N 11.97. C4H5NO3.
Calculated, %: C 41.75; H 4.38; N 12.17.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 2 2001