Cyanamides, preparation

By the hydrolysis of dialkyl cyanamides with dilute sulphuric acid this method gives pure secondary amines. The appropriate dialkyl cyanamide is prepared by treating sodium cyanamide (itself obtained in solution from... 

It is prepared commercially by treating cyanamide (from calcium cyanamide) with ammonium sulphide ... 

The selenoureas needed for condensation can usually be prepared by addition of hydrogen selenide to a solution of the corresponding cyanamides or carbodiimides. They can be less dangerously and quite... 

The advantage of this method is that it avoids the use of hydrogen selenide, necessary for the preparation of selenourea from cyanamide (14). Benzoylselenourea is synthesized by the method of Douglass (24) by the action of potassium selenocyanate On benzoyl chloride in acetone solution. 

In 1880, R. Andreasch (52) confirmed the new formula (37) by preparing thiohydantoine through condensation of thioglycolic acid with cyanamide (the reverse reaction of the basic hydrolysis of thiohydantoin). 

The synthesis of these disubstituied thioureas takes place in three steps. First the alkyl bromide is prepared by the action of hydrobromic acid on the corresponding alcohol (518). Then the dialkylcyanamide is obtained by treatment at 25°C with calcium cyanamide. The yields are of the order of 30 to 60%. Thioureas are obtained in a third step from the cyanamide by reaction at 40 C with HjS in the presence of pyridine. Yields ranged from 57 to 90% (518),... 

DiaminO 4,4-dimethyl-l,3,5-thiadiazine hydrobromide was isolated as by-product (418). Benzene sulfonates of cyanohydrin prepared from sodium cyanide and an halobenzoaldehyde, when treated with thiourea or its derivatives, afford 2,4-diamino-5-(p-halogenophenyl)-thiazole benzene sulfonates (447). Similarly, cyanoamido thiocarbamates obtained from cyanamide and isothiocyanates yield substituted 2,4-diaminothiazoles (598). 

Aminothiazole derivatives (243) can be prepared by treatment of enamines of type 240 with sulfur and cyanamide at room temperature in ethanol (701) yields range from 30 to 70%, and no catalyst is required. Initial formation of the thiolated intermediate (241) is probably followed by addition of cyanamide, yielding 242 (Scheme 124). 

Urea is also used as feed supplement for mminants, where it assists in the utilization of protein. Urea is one of the raw materials for urea—formaldehyde resins. Urea (with ammonia) pyrolyzes at high temperature and pressure to form melamine plastics (see also Cyanamides). Urea is used in the preparation of lysine, an amino acid widely used in poultry feed (see Amino acids Feeds and feed additives, petfoods). It also is used in some pesticides. 

Dormex. Dormex [156-62-7] (Alzodep, hydrogen cyanamide) (26) should not be confused with the same term used for calcium cyanamide. Its other names include carbamide, cyanogenamide, and amidocyanogen. The compound is easily prepared by the continuous carbonation of calcium cyanamide in water (see Cyanamides). 

U.S.A., in lactating dairy cattie to increase milk production. EH Lilly and Company, The Upjohn Company, and American Cyanamid Company also have interests in the commercial appHcation of recombinant bovine GH. Recombinant porcine GH [9061-23-8] preparations from several companies, eg. The Upjohn Company, Smith Kline Beecham Animal Health, Pitman-Moore, Inc., Monsanto Company, and American Cyanamid Company, are being evaluated for commercial use. Recombinant human GH for clinical use is marketed under such names as Protropin (Genentech), Umatrope (EH Lilly), Genotropin (Sumitomo), and Somatonorm (Kabi-Vitmm) by a variety of pharmaceutical companies. A listing of additional suppHers is available (2). 

More recently, other nonphosgene routes for the preparation of aUphatic isocyanates have been reported. For example, American Cyanamid has disclosed the reaction of diisopropenylben2ene with HCl and isocyanic acid [75-13-8] to yield tetramethyixylylene diisocyanates (57). 

Preparation. Hexagonal boron nitride can be prepared by heating boric oxide with ammonia, or by heating boric oxide, boric acid, or its salts with ammonium chloride, alkaU cyanides, or calcium cyanamide at atmospheric pressure. Elemental nitrogen does not react with boric oxide even in the presence of carbon, though it does react with elemental boron at high temperatures. Boron nitride obtained from the reaction of boron trichloride or boron trifluoride with ammonia is easily purified. 

Numerous references for the preparation of aminoguanidine bicarbonate and other salts can be found in the excellent review article, The Chemistry of Aminoguanidine and Related Substances by Lieber and Smith. More recently, it has been prepared by treating a cyanamide solution at 20-50° with hydrazine and carbon dioxide, ... 

Of these methods the first named was for many years the most important commercially. Dicyanodiamide ( dicy ) is prepared by heating cyanamide solution at 70-80°C. The cyanamide itself is prepared from calcium cyanamide Figure 24.5). 

The checkers used 16.8 g. of Eastman Kodak Company cyanamide (P1995) without further purification. A convenient method of preparing cyanamide from commercial calcium cyan-amide has been described. According to the submitters, an aqueous solution of crude cyanamide is satisfactory in the present synthesis and is obtained by adapting this published procedure as follows. 

I-Cyano-3-phenylurea, first obtained by the alkaline hydrolysis of 5-anilino-3- -toluyl-l,2,4-oxadiazole, has been prepared by tlic condensation of phenyl isocyanate and the sodium salt of cyanamide. However, in these publications an incorrect structural assignment for the product was made. 1-Cyano-3-phenyl-urea is obtained also, together with other products, by warming gently l-cyano-3-phenylthiourea with caustic soda in the presence of ethylene chlorohydrin, or by gradually adding caustic )otash to a boiling solution of 1-phenyldithiobiuret and ethylene clilorohydrin in ethanol. ... 

An interesting method of preparing 2-iminotetrahydro-l,3-oxazine derivatives (30) consists in cyclizing A -butyl-A -(y-bromopropyl)-cyanamide. ... 

Dihydrostreptomycin sulfate may be prepared from streptomycin sulfate by catalytic hydrogenation (Merck, Pfizer, Cyanamid), electrolytic reduction (Schenley, Olin Mathieson), or by sodium boro hydride reduction (Bristol), or by isolation from a fermentation process (Takeda). 

Amino resins are condensation thermosetting polymers of formaldehyde with either urea or melamine. Melamine is a condensation product of three urea molecules. It is also prepared from cyanamide at high pressures and temperatures ... 

Dichloropyridazine-4-carbonyl chloride (1) reacts with hydroxyguanidines 2, prepared in situ from tertiary cyanamides R R2NC = N and hydroxylamine (see Houben-Weyl, Vol. E4, p618ff), to give 3-substituted 7-chloropyridazino[4,3-/]-l,2,4-oxadiazepin-5(2/f)-ones 3.3 2... 

Cyanamide can be stannylated under various conditions to give bis(stannyl)carbodiimides (224-227), and bis(stannyl)sulfurdiimides have been prepared from the reaction between S4N4 and trimethyldi-methylaminotin (228). 

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