The Dearrangement of Nitrourea and Its Application in Synthesis

Abstract

Nitrourea might be expected to dearrange1 in two modes to form on the one hand (1) nitroamide and cyanic acid, and on the other (2) ammonia and nitrocyanic acid. The nitro group would promote the dearrangement and the molecule would fall apart more readily than does the molecule of urea.We have found abundant proof of dearrangement of the first sort, but only meager evidence for that of the second. We have isolated nitroamide and cyanic acid from solutions of nitrourea and have prepared nitrourea by the combination of nitroamide with cyanic acid. Since nitrourea dissolved in water dearranges in part into nitroamide and cyanic acid, and since nitroamide decomposes into nitrous oxide and water, it follows that an aqueous solution of one equivalent of nitrourea may be used, with great advantage, for purposes of synthesis as if it were a solution of one equivalent of cyanic acid itself.Nitrourea decomposes on melting with the evolution of gas and yields a sublimate and a solid residue. The gases consist of water, nitrous oxide, cyanic acid, carbon dioxide and ammonia, and the solid materials of monoammonium cyanurate along with small quantities of ammelide, urea and biuret. These are the products which would be expected from the predicted dearrangements. The nitroamide breaks down into water and nitrous oxide. The cyanic acid in part escapes as such, in part combines with ammonia to form urea and in part polymerizes to form cyanuric acid, which combines with a portion of the ammonia to form ammonium cyanurate-and the latter substance by loss of water yields ammelide. Although nitrocyanic acid, OjN-NCO, is not a known substance, it would, from analogy with known nitramines, be expected to decompose into nitrous oxide and carbon dioxide. The presence of ammonia and of carbon dioxide in the products of the decomposition of nitrourea by heat suggests strongly that this substance does dearrange into nitrocyanic acid and ammonia, but constitutes the only real evidence which we have found on that point. The presence of biuret might perhaps be explained by supposing that it is formed, as Werner2 supposes it to be formed in aqueous solution, by the combination of cyanic acid with urea.We have found that 1 Cf. (a) Davis and Underwood,

Microwave Assisted, Solvent- and Ligand-Free Copper Catalyzed N-Arylation of Phenylurea with Aryl Halides

“…As shown in Table 2, the desired amination products of aryl bromides and iodides were obtained in good to excellent yields ( Table 2, entries 1-6 and 7-14), while the coupling reactions for aryl chlorides provided low yields (Table 2, entries [15][16][17][18][19][20][21][22]. Aryl iodides showed a higher reactivity than aryl bromides and aryl chlorides in the coupling reactions.…”

Ureas

“…The reaction is thought to involve the steps shown in Eqs. The process [13] is repeated two or three times, and in each case the phenylurea is collected by chilling the filtrate. To a flask equipped with a reflux condenser and mechanical stirrer are added 39.0 gm (0.30 mole) of aniline hydrochloride, 19.0 gm (0.32 mole) of urea, and 150 ml of water.…”

“…Amines also react with cyanic acid produced in the decomposition of nitrourea to give 70-95% yields of alkylureas [13][14][15][16][17][18] reaction is also possible with the aid of cyanic acid produced from sodium or potassium cyanate and an acid.…”

“…(12) Reaction of urea with halogens [93]. (13) Reaction of urea with nitrous acid [94]. (14) Preparation of 7V-ethylene-7V'-phenylthiourea from phenyl isothiocyanate and ethylenimine [95].…”

Zum Mechanismus der Hydrazinbildung aus Harnstoffen

“…Die farblosen, hygroskopischen Kristalle lassen sich nicht a m Wasser umkristallisieren und schmelzen ab 55" unter Zersetzung. 8,5 g (46,2 mMol) 11 b wurden in 100 ml 2n NaOH bei 50-60' eingetragen, nach20 Min. mit konz.…”