Nitrourea with alcohols

The nitrile group in 82 has been transformed into other versatile functional groups, and the derivatives so obtained have been used in the synthesis of various naturally occurring C-nucleosides and their analogs. Reduction of 82 with lithium aluminum hydride gave the amine 90 which was, in turn, transformed84 into the ureido and N-ni-troso derivatives (91-93) by treatment with nitrourea, followed by benzylation, and nitrosation.85 The diazo derivative 94, obtained by treatment of 93 with alcoholic potassium hydroxide, was a key intermediate in the synthesis of formycin B and oxoformycin B (see Section III,2,a,b). 

In water and in. hydrophilic solvents nitrourea dearranges rapidly into cyanic acid and nitroamide. Alkalis promote the reaction. If an aqueous solution of nitrourea is warmed, bubbles of nitrous oxide begin to come off at about 60°. If it is allowed to stand over night at room temperature, the nitrourea disappears completely and the liquid is found to be a solution of cyanic acid. Indeed, nitrourea is equivalent to cyanic acid for purposes of synthesis. It reacts with alcohols to form carbamic esters (urethanes) and with primary and second amines to form mono-and unsym-di-substituted ureas. 

Nitrourea forms colorless to whitish plate like crystals that begin to decompose when heated to 158 Celsius. The crystals are soluble in alcohol, acetic acid, and acetone—they are insoluble in cold water. The nitrate and perchlorate salts of nitrourea are prepared by treati ng nitrourea with the correspondi ng acids—the nitrate and perchl orate salts are used i n f i reworks, and a variety of pyrotechnic compositions. Nitrourea has limited use in explosives due to its lack of explosives power, but it can be used in rocket propellants and gunpowders. Nitrourea isalso commonly used in making other explosives. It requiresa... 

Nitrourea is decomposed quantitatively into cyanic acid and nitrous oxide when heated in aqueous solution. If primary or secondary amines are present, the products are alkylureas or N,N-diaIkylureas, respectively.Alcohol is used as a solvent for amines which are only slightly soluble In water. The yields in general are excellent (70-98%), and the reaction is preferred to the exchange with urea described above. Alkanolamines give hydroxyalkylureas in 85-95% yields." Nitrourea is conveniently prepared in 90% yield from urea nitrate."... 

Nitrourea is prepared by adding dry urea nitrate (200 grams) in small portions at a time with gentle stirring to concentrated sulfuric acid (1.84) (300 cc.) while the temperature of the mixture is kept below 0. The milky liquid is poured without delay into a mixture of ice and water (1 liter), the finely divided white precipitate is collected on a filter, sucked as dry as may be, and, without washing, is immediately dissolved while still wet in boiling alcohol. The liquid on cooling deposits pearly leaflets of nitrourea. It is chilli and filtered, and the crystals are rinsed with cold alcohol and dried in the air The product, which melts at 146 to 153 with decomposition, is sufficiently pure for use... 

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