Chloroformamidinium chlorides, reaction

Acylation reaction which affords chloroformamidinium chloride is of great interest for the commercial synthesis of carbodiimides, especially dicyclohexylcarbodiimide (see volume 2). 

The reaction of phosgene with substituted ureas is well known. Phosgene reacts with tetrasubstituted ureas as a chlorinating agent to afford chloroformamidinium chlorides in high yields. This topic will be discussed in volume 2. 

Since the cyclic ureas can be obtained from 1,2-diaminoalkanes and CO 2. this reaction represents a potentially useful method for the industrial production of diisocyanates. In contrast, a cyclic chloroformamidinium chloride is obtained from 1,3-dimethyl-... 

Owing to the greater nucleophilic character of sulfur relative to oxygen, reaction of 1,3-disubstituted thioureas with phosgene usually occurs at the sulfur atom, to give high yields of chloroformamidinium chlorides [2083a, 2087] ... 

Reaction of thioureas with phosgene is usually performed at room temperature in an inert solvent (such as benzene, chlorobenzene or 1,2-dichloroethane) in which the thiourea is soluble. By-products, if formed, are readily separated with ethoxyethane in which the chloroformamidinium chloride salts are insoluble. 

In the reaction of dialkyl cyanamides with carbonyl chloride 2 1 adducts XXV are initially formed, as evidenced by the isolated oligomeric chloroformamidinium chloride (XXVI), which is obtained in high yield ( ). 

The reaction of chloroformamidinium chlorides with alkoxide ion yields urea acetals XLV however, free alcohol has to be avoided, because solvolysis of the urea acetals to the ortho esters XLVI occurs ( ). 

The reaction of the chloroformamidinium chloride XLVIII with three moles of alcohol at 0°C produces the oligopseudo urea XLIX, which upon subsequent reaction with aqueous ammonium hydroxide at room temperature yields the triazine derivative L ( ). 

The reaction of the chloroformamidinium chloride LVII with ammonia produces, depending upon the reaction conditions, the triazine derivatives LVIII and LIX ( ). 

The cyclic analogs of chloroformamidines are virtually unknown. Suzuki mentioned the synthesis of 2-chloroimidazolidine but reported no physical constants. The cyclic chloroformamidinium chloride XXV can be obtained from l,3-dimethylimidazolidine-2-one (XXVI) and carbonyl chloride, but this reaction is considerably slower than the phosgenation of the tetrasubstituted linear urea C ). 

Reaction of chloroformamidinium chloride (XXXVII) (cyanamide dihydrochloride) with diethyl iminocarbonate yields diethyl N-cyano-imidocarbonate (XXXVIII) ( ). 

Chloroformamidinium chloride also undergoes rapid reaction with (SbCl4N3)2 to produce the azide XXXIX... 

An analogous methodology can be seen in the proposal to use chloroformamidinium salts as dehydrating agents. A A A /V -Tetramethylchloroformamidinium chloride, used as the condensation agent, is easily available by the reaction of A A A A -tetramethylurea and oxalyl dichloiide. The reaction of carboxylic acids (equation 33) can be achieved at -30 C in the presence of tiiethylamine. Thus, for instance, 2-furoic acid, cinnamic acid and crotonic acid yield e anhydrides in 84%, 83% and 83%, respectively. 

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