An Easy Access to Hydrazinocarbonyl Carbamic Acid Ethyl Esters

Article abstract of DOI:10.1007/PL00010213

The reaction of carboisocyanatidic acid ethyl ester with hydrazines and 3,5-dioxo-1,2,4-triazolidine is reported. The thermal cyclization of the products to 1-substituted 3,5-dioxo-1,2,4-triazolidines and to [1,2,4]triazolo[1,2-a][1,2,4]triazole-1,3,5,7-tetraone was investigated.

Full text of DOI:10.1007/PL00010213

Monatshefte fuÈr Chemie 130, 327±331 (1999)
An Easy Access to Hydrazinocarbonyl
Carbamic Acid Ethyl Esters
Gottfried Faleschini
È
Institut fuÈr Anorganische Chemie, Karl-Franzens-Universitat Graz, A-8010 Graz, Austria
Summary. The reaction of carboisocyanatidic acid ethyl ester with hydrazines and 3,5-dioxo-1,2,4-
triazolidine is reported. The thermal cyclization of the products to 1-substituted 3,5-dioxo-1,2,4-
triazolidines and to [1,2,4]triazolo[1,2-a][1,2,4]triazole-1,3,5,7-tetraone was investigated.
Keywords. Hydrazinocarbonyl carbamic acid ethyl esters; 3,5-Dioxo-1,2,4-triazolidine; [1,2,4]Tria-
zolo[1,2-a][1,2,4]triazole-1,3,5,7-tetraone.
È
Eine einfache Darstellung von Hydrazinocarbonyl-carbaminsaureethylestern
Zusammenfassung. Die Reaktion von Ethoxycarbonylisocyanat mit Hydrazinen und 3,5-Dioxo-
1,2,4-triazolidin und die thermische Zyklisierung dieser Produkte unter Bildung von 1-substituierten
3,5-Dioxo-1,2,4-triazolidinen und [1,2,4-]Triazolo[1,2-a][1,2,4]triazolo-1,3,5,7-tetraon wurde unter-
sucht.
Introduction
The thermal cyclization of 1-phenyl-4-carbethoxysemicarbazide has been shown to
result in the formation of 1-phenyl-1,2,4-triazolidine-3,5-dione [1]. The nucleo-
philic addition of Lewis bases with carboisocyanatidic acid ethyl ester (1) is well
known since 1908 [2]. However, the reaction of 1 with hydrazines has not been
investigated until now. Comparable reactions of hydrazine carboxylic acid ethyl
ester with 1 [3] and of carboisocyanatidic acid phenyl ester with hydrazine
compounds [4] have already been described. In this paper, the preparation of
substituted semicarbazides from carboisocyanatidic acid ethyl ester and hydrazine
compounds as well as the thermal reactions of these compounds are described.
Ã
Corresponding author

328
G. Faleschini
Results and Discussion
We found that treatment of 1 with substituted hydrazines 2a±c leads to the
corresponding hydrazinocabonyl carbamic acid ethyl esters 3a±c in high yields.
The thermal cyclization of 3a and 3b affords the triazolidines 4a,b which could
be obtained by direct reaction of 1 and the corresponding hydrazines. The 1H NMR
spectra of 3b and comparison of the IR spectra of 3a and 3b con®rm the structure
of 3b. Attempts to cyclize 3c to 3,5-dioxo-1,2-dimethyl-1,2,4-triazolidine failed.
Thermal analysis of 3c indicates complete decomposition starting at 121ꢀC without
formation of 3,5-dioxo-1,2-dimethyl-1,2,4-triazolidine.
In the reaction of 1 with hydrazine hydrochloride, the formation of hy-
drazine-N,N0-di-(carboxylic acid carbamic acid ethyl ester) (5) is observed.
Therefore, the addition of 1 to the intermediate hydrazinocarbonyl carbamic acid
ethyl ester is preferred over the addition of the almost insoluble hydrazine
hydrochloride.
In former work we have described the multistage preparation of [1,2,4]tria-
zolo[1,2-a][1,2,4]triazole-1,3,5,7-tetraone 8 [5]. In the reaction of 1,2,4-triazole-
3,5-dione (6) with 1, a quantitative yield of (3,5-dioxo[1,2,4]triazolidine-1-
carbonyl)-carbamic acid ethyl ester (7) is obtained. Cyclization of 7 at 160ꢀC
affords 8 with 35% yield only. In the starting period of the reaction, a precipitation
of 6 could be observed at 140ꢀC. This can be explained by the reverse reaction of 7
to 6 and 1 at temperatures above 140ꢀC, followed by the reaction of ethanol and 1
to imidodicarbonic acid diethyl ester (9) [1]. Due to this behaviour, 8 could be
prepared in 85% yield if the resulting ethanol was trapped with tetrachlorosilane to
prevent the formation of 9. In an analogous manner, 3,5-dioxo-1,2,4-triazolidine
(6) was be prepared in 75% yield by treatment of equimolar amounts of 1 and

Synthesis of Hydrazinocarbonyl Carbamic Acid Ethyl Esters
329
hydrazine hydrochloride in the presence of tetrachlorosilane.
Experimental
1
IR: Perkin-Elmer 882; H and 13C NMR (DMSO-d6, TMS): Bruker MSL 300; MS: Carlo-Erba
QDM-1000 (70 eV); melting points: Mettler FP61 (capillary); decomposition point onset: Perkin-
Elmer TGA7 (scan rate: 2ꢀC/min, purge gas: N2(2 l/h), sample weight; 10 mg). The elemental
analyses (C,H,N) compared with the calculated values. Carboisocyanatidic acid ethyl ester (1) was
prepared according to Ref. [6].
(3-Phenyl-hydrazinocarbonyl)-carbamic acid ethyl ester (3a; C10H13N3O3)
To a stirred solution of 8.0 g (74 mmol) phenylhydrazine in 40 ml THF, a solution of 8.5 g (74 mmol)
1 in 30 ml THF was added dropwise at 20ꢀC. The mixture was re¯uxed for 2 h. The solvent was
removed under reduced pressure, and the residue was recrystallized from ethanol to yield 14.1 g
(85%) white crystals.
Decomp. (loss of EtOH): 172ꢀC (Ref. [1]: 176ꢀC); IR (KBr): ꢀ(N±H) ˆ 3274, 3244 cmꢁ1
,
ꢀ(C=O) ˆ 1718, 1696 cmꢁ1; 1H NMR: ꢁ ˆ 10.25 (s, 1H, NH), 9.18 (s, NH), 7.81 (s, 1H, NH), 7.22±
6.73 (m, 5H, phenyl), 4.19 (q, 2H, CH2), 1.27 (t, 3H, CH3) ppm; 13C NMR: ꢁ ˆ 153.8, 149.5, 129.1,
‡
119.06, 112.36, 61.81, 14.5 ppm; MS: m/z (%) ˆ 223 (12, M ), 177(23), 134(13), 105(35), 91(19),
17(100), 70(56), 51(35), 44(32), 29(93).
(3-Methyl-hydrazinocarbonyl)-carbamic acid ethyl ester (3b; C5H11N3O3)
To a stirred solution of 3.7 g (80 mmol) methylhydrazine in 50 ml THF, a solution of 9.2 g (80 mmol)
1 in 100 ml THF was added dropwise at 0ꢀC. The mixture was re¯uxed for 2 h and ®ltered hot to
remove approx. 4 g of 4b. The THF solution was concentrated to 40 ml, cooled, and ®ltered. The
white product was recrystallized from ethanol to yield 6.4 g (49%) white crystals.
Decomp. (loss of EtOH): 139ꢀC; IR (KBr): ꢀ(N±H) ˆ 3288, 3241 cmꢁ1, ꢀ(C=O) ˆ 1718,
1696 cmꢁ1
;
1H NMR: ꢁ ˆ 10.1 (s, 1H, NH), 8.77 (s, 1H, NH), 4.8 (s, 1H, NH), 4.13 (q, 2H,
CH2-ethyl), 2.49 (s, 3H, N±CH3), 1.23 (t, 3H, CH3-ethyl) ppm; 13C NMR: ꢁ ˆ 155.33, 154.63, 61.62,
‡
38.7, 14.49 ppm; MS: m/z (%) ˆ 161 (13, M ), 115(46), 90(40), 72(26), 62(68), 46(92), 29(100).

330
G. Faleschini
(2,3-Dimethyl-hydrazinocarbonyl)-carbamic acid ethyl ester (3b; C6H13N3O3)
To a stirred solution of 4.3 g (72 mmol) N,N0-dimethylhydrazine in 80 ml THF, a solution of 8.25 g
(72 mmol) 1 in 50 ml THF was added dropwise at 0ꢀC. The mixture was stirred for 2 h at 20ꢀC. The
solvent was removed under reduced pressure, and the residue was recrystallized from heptane to
yield 11.2 g (89%) white crystals.
M.p.: 76.1ꢀC; decomp.: 121ꢀC; IR (KBr): ꢀ(N±H) ˆ 3287 cmꢁ1, ꢀ(C=O) ˆ 1719, 1707 cmꢁ1; 1H
NMR: ꢁ ˆ 9.95 (s, 1H, NH), 8.54 (s, 1H, NH), 4.13 (q, 2H, CH2-ethyl), 2.45 (s, 6H, 2xN±CH3), 1.23
(t, 3H, CH3-ethyl) ppm; 13C NMR: ꢁ ˆ 151.51, 151.3, 61.54, 47.6, 47.0, 14.46 ppm; MS: m/z
‡
(%) ˆ 175 (25, M ), 133(48), 105(17), 86(28), 59(100), 43(64), 29(68).
3,5-Dioxo-1-phenyl-1,2,4-triazolidine (4a, C8H7N3O2)
To a stirred solution of 6.6 g (61 mmol) phenylhydrazine in 30 ml diglyme, 7.0 g 1 (61 mmol) in
20 ml diglyme were added dropwise, and the mixture was re¯uxed for 2 h. To the cooled solution,
100 ml heptane was added. The precipitate was ®ltered and recrystallized from ethanol to yield 8.2 g
(76%) white ¯akes; m.p.: 269ꢀC (Ref. [7]: 269ꢀC).
3,5-Dioxo-1-methyl-1,2,4-triazolidine (4b, C3H5N3O2)
To a stirred solution of 2.0 g (43.5 mmol) methylhydrazine in 30 ml diglyme, a solution of 5.0 g
(43.5 mmol) 1 in 20 ml diglyme was added dropwise at 0ꢀC. The mixture was re¯uxed for 4 h,
cooled, ®ltered, and recrystallized from water to yield 3.9 g (78%) white crystals; m.p.: 242ꢀC (Ref.
[4]: 243ꢀC).
3,5-Dioxo-[1,2,4]triazolidine-1-carbonyl-carbamic acid ethyl ester (7; C6H8N4O5)
To a stirred solution of 5.05 g (50 mmol) 6 in 40 ml THF, a solution of 5.75 g (50 mmol) 1 in 50 ml
THF was added dropwise at 20ꢀC. The mixture was re¯uxed for 4 h, the solvent was removed under
reduced pressure, and the residue was recrystallized from ethanol to yield 10.2 g (94%) white
crystals.
1
Decomp.: 156ꢀC; IR (KBr): ꢀ(N±H) ˆ 3220 cmꢁ1, ꢀ(C=O) ˆ 1800, 1755, 1700 cmꢁ1; H NMR:
ꢁ ˆ 10.05 (s, 1H, NH), 8.54 (s, 1H, NH), 4.20 (q, 2H, CH2-ethyl), 1.27 (t, 3H, CH3-ethyl) ppm; 13
NMR: ꢁ ˆ 151.57, 151.45, 149.90, 143.25, 62.26, 14.32 ppm.
C
Hydrazine-N,N0-di(carboxylic acid carbamic acid ethyl ester) (5; C8H14N4O6)
7.0 g (0.103 mol) hydrazine hydrochloride and 11.5 g (0.1 mol) 1 in 50 ml toluene were re¯uxed for
5 h. The mixture was cooled and ®ltered. The white precipitate was washed with acetone to remove
toluene and twice with 50 ml water to yield 12.5 g (95%) white powder.
1
Decomp.: 203ꢀC; IR (KBr): ꢀ(N±H) ˆ 3322 cmꢁ1, ꢀ(C=O) ˆ 1722 (sh) 1714, 1698 cmꢁ1; H
NMR: ꢁ ˆ 10.39 (s, 2H, 2xNH), 9.21 (s, 2H, 2xNH), 4.18 (q, 4H, 2xCH2), 1.26 (t, 6H, 2xCH3) ppm;
13C NMR: ꢁ ˆ 154.2, 153.17, 61.93, 14.49 ppm.
[1,2,4]Triazolo[1,2-a][1,2,4]triazole-1,3,5,7-tetraone (8)
6.1 g (60 mmol) 3,5-dioxo-1,2,4-triazolidine, 6.95 g (60 mmol) 1, and 4 g (23.5 mmol) SiCl4 were
re¯uxed in 50 ml diglyme for 6 h. The solution was cooled to 0ꢀC, and the precipitate was
®ltered and washed with dichloromethane to yield 8.5 g (85%) white crystals; m.p.: 341ꢀC (Ref. [5]:
340ꢀC).

Synthesis of Hydrazinocarbonyl Carbamic Acid Ethyl Esters
331
3,5-Dioxo-1,2,4-triazolidine (6)
A mixture of 9.5 g 1 (82 mmol), 6 g (87.6 mmol) hydrazine hydrochlorid, and 5 g (29 mmol) SiCl4 in
90 ml diglyme was re¯uxed for 20 h. The solvent was removed under reduced pressure, and the
residue was recrystallized from water to yield 6.1 g (75.5%) white needles; m.p.: 251ꢀC (Ref. [8]:
250ꢀC).
References
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[3] Bycroft BW, Chhabra SR, Grout RJ, Crowley PG (1984) J Chem Soc Chem Commun 17: 1156
[4] Hagemann H (1977) Angew Chem 89: 789
[5] Nachbaur E, Faleschini G, Belaj F, Janoschek R (1988) Angew Chem 100: 703
[6] Speziale AJ, Smith LR, Fedder JE (1965) J Org Chem 30: 4306
[7] Gordon AA, Katritzky AR, Popp FD (1966) Tetrahedron Suppl 7: 213
[8] Gordon PG, Audrieth LF (1957) Inorg Synth 5: 52
Received April 8, 1998. Accepted (revised) September 21, 1998