Synthesis of 1,4-diphenyl-3-phenylimino-1,2-dihydro-1,2,4-triazolium hydroxide (nitron)

Article abstract of DOI:10.1134/S1070427206030396

1,4-Diphenyl-3-phenylimino-1,2-dihydro-1,2,4-triazolium hydroxide (Nitron) is prepared by the reaction of Pb₃O₄ with diphenylthiourea, followed by the reaction of the obtained diphenylcarbodiimide with phenylhydrazine to form triphenylaminoguanidine, whose heterocyclization yields 1,4-diphenyl-3-phenyl-imino-1,2-dihydro-1,2,4-triazole, which is subsequently oxidized. Pleiades Publishing, Inc., 2006.

Full text of DOI:10.1134/S1070427206030396

ISSN 1070-4272. Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 3, pp. 506 507. Pleiades Publishing, Inc., 2006.
Original Russian Text A.P. Kriven’ko, N.A. Morozova, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 3, pp. 515 516.
BRIEF
COMMUNICATIONS
Synthesis of 1,4-Diphenyl-3-phenylimino-1,2-dihydro-
1,2,4-triazolium Hydroxide (Nitron)
A. P. Kriven’ko and N. A. Morozova
Chernyshevskii Saratov State University, Saratov, Russia
Institute of Natural Sciences, Saratov State University, Saratov, Russia
Received July 15, 2005; in final form, January 2006
Abstract 1,4-Diphenyl-3-phenylimino-1,2-dihydro-1,2,4-triazolium hydroxide (Nitron) is prepared by the
reaction of Pb3O4 with diphenylthiourea, followed by the reaction of the obtained diphenylcarbodiimide with
phenylhydrazine to form triphenylaminoguanidine, whose heterocyclization yields 1,4-diphenyl-3-phenyl-
imino-1,2-dihydro-1,2,4-triazole, which is subsequently oxidized.
DOI: 10.1134/S1070427206030396
1,4-Diphenyl-3-phenylimino-1,2-dihydro-1,2,4-tri-
NPh
NHPh
azolium hydroxide (Nitron) is a well-known reagent
for analysis of nitrate, perchlorate, tungstate, rhuthe-
nate, and iodide anions [1], as well as silicon, germa-
nium, arsenic, and phosphorus [2, 3]. Nitron was used
for preparing lithium iodide power sources utilized
in manufacture of electrocardiostimulators [4].
II + H2NNHPh
C
NNHPh
CHNNHPh.
NHPh
IIIb
NHPh
IIIa
Condensation of guanidine IIIa with formaldehyde
in isopropanol at 55 60 C yields 1,4-diphenyl-3-
phenylimino-1,2-dihydro-1,2,4-triazole IV in 87 89%
yield:
The published method of preparation of Nitron [5]
allows its synthesis in a yield of 20% based on di-
phenylthiourea I because of incomplete conversion
in the step of the reaction of phenylhydrazine with
diphenylcarbodiimide and formation of a tautomer
decreasing the yield and purity of the final product.
NPh
HN
IIIa + CH2O
PhN
NPh
In this study we developed the conditions for syn-
thesis of purer Nitron reagent in higher yields.
IV
This is followed by oxidation of triazole IV into
Nitron by the reaction with sodium nitrite; the final
product is isolated by reprecipitation from a mixture
of acetic acid and 25% ammonia solution:
EXPERIMENTAL
The synthesis includes four steps. First, thiourea is
NPh
_ N
desulfurized with Pb O into N,N-diphenylcarbodi-
3
4
NaNO
2
imide II:
IV
+Ph
PhN
N
.
NHPh
C=S
NPh
C
C
H
Ph O
3
4
PbS + H2O.
+
V
NHPh
I
NPh
II
The resulting Nitron V is 98 wt % pure, which cor-
responds to the analytically pure grade.
Addition of phenylhydrazine to diimide II at 29
31 C yields the desired triphenylaminoguanidine tau-
tomer IIIa in 80% yield, which is virtually free of
impurity tautomer IIIb transforming under the reac-
tion conditions into the ballast pseudonitron :
The yield of Nitron based on diphenylthiourea was
43%, which is virtually 2 times that reported in [5].
The IR spectra were recorded on an FSM-1201
Fourier spectrometer in Nujol, and the H NMR spec-
1
506

SYNTHESIS OF 1,4-DIPHENYL-3-PHENYLIMINO-1,2-DIHYDRO-1,2,4-TRIAZOLIUM HYDROXIDE 507
tra, on a Varian FT 80A (80 MHz) spectrometer in
from light green to red. The reaction mass was cooled
to room temperature and poured into a 25% aqueous
ammonia solution with ice. The resulting finely
divided yellow precipitate of Nitron V was filtered off
and reprecipitated from a mixture of glacial acetic acid
and ammonia solution (1 : 3 by volume). The reaction
product was dried in a vacuum oven at 50 60 C and
a pressure of 0.2 kg cm . The yield of Nitron reagent
was 176 g (74%), mp 186 188 C (dec.). Published
data: mp 189 C (dec.).
CDCl (with TMS as internal reference).
3
N,N-Diphenylcarbodiimide II. Thiourea I (300 g)
in 700 ml of benzene was refluxed with vigorous stir-
ring until water ceased to liberate (Dean Stark trap),
and 300 g of Pb O was added in portions. Desulfuri-
3
4
zation was regarded as complete when water ceased to
liberate. The sludge was separated, and diphenylcar-
bodiimide II was taken to the next step without isola-
tion.
2
Ttriphenylaminoguanidine IIIa. To the solution
of diimide II (see above), cooled to 10 C, 136 ml of
phenylhydrazine was added dropwise so that the tem-
perature in the reaction mixture was about 30 C. Then
100 ml of benzene was distilled off at atmospheric
pressure; 300 ml of isopropanol was added to the re-
maining solution, and the resulting mixture was kept
at 0 C for 8 10 h. The crystalline reaction product
was filtered off and dried in air; yield 350 g (88%),
mp 156 158 C.
Found (%): C 76.89, H 5.20, N 18.01.
C20H16N4.
Calculated (%): C 76.92, H 5.13, N 17.95.
1
IR spectrum (cm ): 3052 [ (CH
)], 2924
arom
1
[ (CH)], 572 [ (CH
)].
H NMR spectrum
arom
(CDCl ),
(ppm): 6.64 7.64 m (16H, Ph, CH).
3
CONCLUSION
1,4-Diphenyl-3-phenylimino-1,2-dihydro-1,2,4-
triazole IV. To 200 g of compound IIIa, 200 ml
of 40% aqueous solution of formaldehyde and 1.0 l of
isopropanol were added. The reaction mixture was
heated at 55 60 C for 0.5 h and cooled to 22 C.
The reaction product was filtered off, washed with
150 ml of isopropanol, and dried in air, which yielded
184 g (89%) of triazole IV; mp 126 128 C.
Conditions were developed for synthesis of high-
purity (98 wt %) Nitron reagent in the preparative
yield of 43% with the use of Pb O instead of lead
3
4
oxide (PbO ) and 2-propanol instead of ethanol.
2
REFERENCES
1. Babenko, A.S., Tolmachev, V.N., and Dzizin, A.N.,
1,4-Diphenyl-3-phenylimino-1,2-dihydro-1,2,4-
triazolium hydroxide V. To a solution of 240 g of
triazole IV in 1 l of isopropanol, glacial acetic acid
was added at 65 67 C until complete dissolution of
crystalline substance IV, which required 200 ml of
the acid. Then a solution of 88 g of sodium nitrite in
200 ml of water was added. The reaction was regarded
as complete when the color of the solution changed
Ukr. Khim. Zh., 1963, vol. 29, no. 7, pp. 702 708.
2. Hahn, H. and Wapen, K., Z. Anal. Chem., 1961,
vol. 182, no. 5, pp. 343 357.
3. Canteher, N. and Athanassova, D., Talanta, 1973,
vol. 20, no. 1, p. 125.
4. USSR Inventor’s Certificate 1556486.
5. Buch, M., Ber., 1905, vol. 38, no. 1, pp. 856 866.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 79 No. 3 2006