Nitrourea with amines

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). 

Amines also react with cyanic acid produced in the decomposition of nitrourea to give 70-95% yields of alkylureas [13-18] (Eqs. 12 and 13). This... 

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 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."... 

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