Amines 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. 

Ammonia is used in the fibers and plastic industry as the source of nitrogen for the production of caprolactam, the monomer for nylon 6. Oxidation of propylene with ammonia gives acrylonitrile (qv), used for the manufacture of acryHc fibers, resins, and elastomers. Hexamethylenetetramine (HMTA), produced from ammonia and formaldehyde, is used in the manufacture of phenoHc thermosetting resins (see Phenolic resins). Toluene 2,4-cHisocyanate (TDI), employed in the production of polyurethane foam, indirectly consumes ammonia because nitric acid is a raw material in the TDI manufacturing process (see Amines Isocyanates). Urea, which is produced from ammonia, is used in the manufacture of urea—formaldehyde synthetic resins (see Amino resins). Melamine is produced by polymerization of dicyanodiamine and high pressure, high temperature pyrolysis of urea, both in the presence of ammonia (see Cyanamides). 

The nitrogen of aHphatic and aromatic amines is alkylated rapidly by alkyl sulfates yielding the usual mixtures. Most tertiary amines and nitrogen heterocycles are converted to quaternary ammonium salts, unless the nitrogen is of very low basicity, eg, ia tn phenylamine. The position of dimethyl sulfate-produced methylation of several heterocycles with more than one heteroatom has been examined (22). Acyl cyanamides can be methylated (23). Metal cyanates are converted to methyl isocyanate or ethyl isocyanate ia high yields by heating the mixtures (24,25). 

Although in the dry state carbon tetrachloride may be stored indefinitely in contact with some metal surfaces, its decomposition upon contact with water or on heating in air makes it desirable, if not always necessary, to add a smaH quantity of stabHizer to the commercial product. A number of compounds have been claimed to be effective stabHizers for carbon tetrachloride, eg, alkyl cyanamides such as diethyl cyanamide (39), 0.34—1% diphenylamine (40), ethyl acetate to protect copper (41), up to 1% ethyl cyanide (42), fatty acid derivatives to protect aluminum (43), hexamethylenetetramine (44), resins and amines (45), thiocarbamide (46), and a ureide, ie, guanidine (47). 

Additions. The addition reactions of ammonia and amines to the cyanamide nitrile group have been thoroughly studied (15). For optimum conditions, the reaction should be carried out ia an aqueous medium at about 140°C. Gradual addition of the cyanamide to the amine salt minimises dimerization. 

Diese Methode dient zur Oberfiihrung heterocyclischer tertiarer Amine iiber die mit der von Braun-Reaktion erhaltlichen Cyanamide in die sekundaren Amine, besonders in der Alkaloidchemie zur Herstellung von Nor-Verbindungen2 3 und zur Aufspaltung des Spi-ran-Geriistes in Erythrina-Alkaloiden4 z. B. ... 

A convenient way of obtaining secondary amines without contamination by primary or tertiary amines involves treatment of alkyl halides with the sodium or calcium salt of cyanamide NH2—CN to give disubstituted cyanamides, which are then hydrolyzed and decarboxylated to secondary amines. Good yields are obtained when the reaction is carried out under phase-transfer conditions. The R group may be primary, secondary, allylic, or benzylic. 1, co-Dihalides give cyclic secondary amines. 

Conversion of Tertiary Amines to Cyanamides The von Braun Reaction... 

Selenoureas are prepared by reaction of isoselenocyanates with amines, or by reaction of carbodiimides with a mixture of LiAlH4/Se and by reaction of cyanamides with LiAlH4/Se.267 272 The tyrosinase inhibitory activity and superoxide radical scavenger effect of selenoamides and selenoureas have been investigated (Scheme 84).273 275... 

A second method is due to J. von Braun and consists in the addition of cyanogen bromide to tertiary cyclic bases.1 In the unstable addition product a C—N-linkage is broken and at the same time the bromine wanders to a new position. A brominated derivative of cyanamide is produced and this, on hydrolysis, yields a secondary amine which can be broken down further, e.g. 

The strongly acidic character of cyanamide, compared with simple amines, results in its facile dialkylation by a range of reagents [24], Reaction with a,(o-dihalogeno compounds leads to cyclic products (Table 5.4). 

Amarthol fast orange R base, see 3-Nitroaniline Amatin, see Hexachlorobenzene Ameisenatod, see Lindane Ameisenmittel merck, see Lindane American Cyanamid 3422, see Parathion American Cyanamid 4049, see Malathion Amerstat 274, see Ethylenediamine Amfol, see Ammonia Amidox, see 2,4-D Amine 2,4,5-T for rice, see 2,4,5-T Aminic acid, see Formic acid 2-Aminoacetylfluorene, see 2-Acetylaminofluorene 4-Aminoaniline, see / Phenylenediamine p-Aminoaniline, see / Phenylenediamine 2-Aminoanisole, see oAnisidine 4-Aminoanisole, see p-Anisidine oAminoanisole, see oAnisidine joAminoanisole, see p-Anisidine Aminobenzene, see Aniline p-Aminobiphenyl, see 4-Aminobiphenyl 1-Aminobutane, see Butylamine l-Amino-4-chloroaniline, see 4-Chloroaniline l-Amino-4-chlorobenzene, see 4-Chloroaniline 1-Amino-p-chlorobenzene, see 4-Chloroaniline 4-Aminochlorobenzene, see 4-Chloroaniline p-Aminochlorobenzene, see 4-Chloroaniline 4-Aminodiphenyl, see 4-Aminobiphenyl... 

The formation of a biguanide as a by-product in a condensation of a cyanamide and amine (225) (which would normally be expected to yield a guanidine) and as main product in the reaction of glucosamine and cyanamide (437) has been noted. In the former example, the small amount of biguanide probably arose by further reaction of the primary guanidine (which formed the main product) with C5 namide. In the second example the biguanide may be the result of the interaction of the amine and intermediate cyanoguanidine. 

Guanidines have been prepared by a wide variety of methods, of which two are of much greater importance than the others. These two methods, (a) the addition of amines to cyanamides and (b) the displacement of an alkylmercaptan by an amine from an alkylisothiouronium salt, together with close variants, are discussed first, and this discussion is followed by a survey of less frequently used procedures. 

Reaction between an amine salt and cyanamide has been used successfully for the synthesis of many mono- and poly-alkylguanidines [84-95], and also of alkoxyguanidines [96, 97] and aryloxyguanidines [98]. The reaction is usually carried out in boiling water or ethanol for from 1 to 24 hours. Higher temperatures have been employed using sealed tubes [99,100] or butanol as a solvent [82,101]. 

Very dilute acetic acid [102] and ethyl acetate [103] have also been used as solvents. The fusion of amine salts with cyanamide or a substituted cyanamide is often more satisfactory than using a solvent [107—109, 228], particularly for sterically hindered guanidines such as t-butyiguanidine [228]. 

Odo studied the formation of methylguanidine from cyanamide and aqueous mixtures of methylamine and methylamine hydrochloride in various proportions [ 110]. He concluded that the reaction occurred by a reversible nucleophilic attack of the free amine on cyanamide, and that an acid was required to shift the equilibrium in the direction of the guanidine. 

Guanidines have been prepared by the reaction between an amine, or an amine salt, and a host of other reagents, such as a thiourea in the presence of lead or mercuric oxide [83, 157, 158], carbodi-imides [140, 174, 175],calcium cyanamide [176, 177], isonitrile dichlorides [178—180], chloroformamidines [181], dialkyl imidocarbonates [182], orthocarbonate esters [183], trichloro-methanesulphenyl chloride [184], and nitro- or nitroso-guanidines [185-188]. Substituted ureas can furnish guanidines, either by treatment with amines and phosphorus oxychloride [189], or by reaction with phenylisocyanate [190] or phosgene [191]. 

A useful method for the synthesis of 5-chloro-l,2,4-thiadiazoles (206) is the reaction of amidines with trichloromethylsulfenyl chloride (see Equation (30)). 3-Halo derivatives (349) (X = Cl, Br, I) (Equation (57)) have been obtained in moderate yields from the corresponding amines (348) via the Sandmeyer-Gatterman reaction <84CHEC-I(6)463>. 3-Chloro-l,2,4-thiadiazolin-5-ones (350) and (351) can be prepared by reacting chlorocarbonylsulfenyl chloride with carbodiimides or cyanamides respectively (Scheme 79) <84CHEC-I(6)463>. 

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