Cyanamides

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... 

Into a 750 ml. round-bottomed flask furnished with a reflux condenser place a solution of 34 g. (18-5 ml.) of concentrated sulphuric acid in 100 ml, of water add 33 g. of di-n-butyl cyanamide and a few fragments of porous porcelain. Reflux gently for 6 hours. Cool the resulting homogeneous solution and pour in a cold solution of 52 g. of sodium hydroxide in 95 ml. of water down the side of the flask so that most of it settles at the bottom without mixing with the solution in the flask. Connect the flask with a condenser for downward distillation and shake it to mix the two layers the free amine separates. Heat the flask when the amine with some water distils continue the distillation until no amine separates from a test portion of the distillate. Estimate the weight of water in the distillate anp add about half this amount of potassium hydroxide in the form of sticks, so that it dissolves slowly. 

Also known as nitrolim and lime nitrogen. The fresh product contains approximately 55 per cent, of calcium cyanamide, 20 p>er cent, of lime, 12 per cent, of graphite and small amounts of other impurities. It should be protected from moisture when stored in order to prevent slow polymerisation to dicyano-diamide. 

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

Supplement (combined with Volume IV) III, 2nd 1929 195-449 Hydroxy-carboxylic acids Carbonic acid, 3. GlycoUic acid, 228. Lactic acid, 261. Tartaric acid, 481. Citric acid, 556. Urea, 42. Cyanamide, 74. Thiocyemic acid, 140. 

The solubility of the carbonate in water containing carbon dioxide causes the formation of caves with stalagtites and stalagmites and is responsible for hardness in water. Other important compounds are the carbide, chloride, cyanamide, hypochlorite, nitrate, and sulfide. 

Another way in which academic chemists keep in touch with industry is through consulting. During the years I consulted at different times for Exxon, Chevron, Cyanamid, ENICHEM (Italy), and Pechiney-Kuhlman (Erance, when a friend, Lucien Sobel, was a research director). I enjoyed these contacts, because they kept me aware of current industrial developments and interests. At the same time, it was also rewarding to be able to suggest to my industrial friends new approaches and directions that on occasion were useful and resulted in practical applications. 

Condensation of 2-phenyl-4-amino-5-benzoylthiazole with cyanamide yields the pyrimidothiazole (Scheme 88) (133) (49) 2-imino-3-aryl-4-amino-5-carbethoxy-4-thiazolines condense similarly with alkyl isothiocyanates (276). 

N-(2-Thiazolyl)cyanamide may be converted into guanidino derivatives by the action of hydrazines (487). /V-Aryl-N -(4-aryl-2-thiazolybguanidines... 

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). 

Another method used less often for these syntheses consists in condensing ketones with cyanamid and sulfur (527) (Method D). 

Aminolhtazoles were synthetized from thiourea by three methods Method A, from a-haloketones or aldehydes designated as (Cl) or (Br) Method B, from ketones and iodine (fj) or bromine (Btj) Method C, from iodomercuriketones. Method D consists in condensing ketones with cyanamid and sulfur. 

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),... 

Cyanamide (227), Rj = NH2, condensed with a-mercaptoketones gives the corresponding 2-aminothiazoles (527). 

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). 

Several 4-amino-2,5-disubstituted thiazoles (257) have been obtained recently (702, 756, 776, 814, 820) by a ring cyclization reaction of halogeno compounds with cyanamide derivatives (263) according to the general Scheme 135. 

Reaction of 1,3-oxathiolium salts (264) with cyanamide in the presence of sodium ethoxide produces also substituted 4-aniinothiazolcs (265) (Scheme 136) (777). 

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