Phenylurea cyanate method

Salts of primary aromatic amines react with solutions of alkali cyanates to yield first the amine cyanate, which then undergoes molecular rearrangement to the arylurea, for example  

The monoarylurea may be prepared directly from the amine by heating it in aqueous solution with an equivalent quantity of alkali cyanate and excess of acetic acid, for example  

Method 1 (from the amine hydrochloride). Dissolve 13-0 g. of aniline hydrochloride in 200 ml. of water and filter, if necessary, from any insoluble matter into a 350 ml. beaker or conical flask. Add a solution of 6-5 g. of pure sodium cyanate in 50 ml. of warm water. Allow to stand for a few hours until crystallisation is complete. Filter with suction on a Buchner funnel, and wash with a little cold water. Dry in the steam 

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Of the various published methods of preparing phenylurea, such as treatment of aniline salts with potassium cyanate in water solution,1 heating aniline with urea,2 with cyanic acid,3 or with cyanogen chloride,4 and the interaction of phenyl isocyanate or phenylcarbamine chloride with ammonia,5 the only ones to be considered as practical methods for preparation are the first two. The first suffers from the disadvantage that potassium cyanate is not easily prepared in the laboratory and rapidly undergoes spontaneous decomposition in storage while by the action of urea on aniline alone, carbanilide is formed in rather larger proportion than phenylurea. 

Preparation of Af-Cyano-4-Methyl-A -Phenyl-Benzene-sulfonamide (1). Dehydrative tosylation of iV-phenylurea 2 with p-toluenesulfonyl chloride in pyridine at room temperature gave iV-cyano-4-methyl-iY-phenyl-benzenesulfonamide in 76% yield (eq 1). Notably, title compound 1 is synthesized in a user-friendly and environmentally benign fashion, eliminating the use of toxic cyanation reagents such as BrCN and HCN. Alternative methods of preparation involve the direct tosylation of phenyl cyanamide in pyridine. Structural analogs, such as ben-zenesulfonyl IV-phenyl cyanamide 3 and p-nitrobenzenesulfonyl //-phenyl cyanamide 4, are accessible in a similar manner. ... 

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