Carbonimidoyl dichlorides synthesis

The addncts derived from carbodiimides and nncleophiles also undergo thermal elimination reactions to regenerate the carbodiimide, and they are therefore of limited preparative value. For example, the elimination of hydrogen chloride from carbonimidoyl dichlorides is used in the synthesis of arenesulfonylcarbodiimides (see Section 9.2.2). Of course, isoureas and isothioureas also undergo elimination reactions. When the elimination of isothioureas is conducted in the presence of heavy metal ions, the insoluble metal mercaptides are precipitated to facilitate the in situ generation of the carbodiimides. 

In addition to the two classical methods of synthesis of carbonimidoyl dichlorides, several new methods were developed more recently. Thus, chlorination of imidoyl chlorides, generated from monosubstituted formamides and thionyl chloride, provides a useful new method to produce a great variety of carbonimidoyl dichlorides Likewise,... 

The synthesis of carbonimidoyl dihalides is not limited to compounds having the N=CX2 group attached to aliphatic and aromatic hydrocarbyl and heterocyclic moieties. Acyl ( 11 125 aroyl (4.55,56,114,125 fonyl (5.7,32,37,1 1 1,1 15 phosphoryl carbonimidoyl dichloridesC " ) have been synthesized, and a variety of other combinations can certainly be visualized. A recent survey of syntheses of carbonimidoyl dichlorides has been published by Kiihle and his co-workers... 

The chlorination of isothiocyanates is the classical synthesis of carbonimidoyl dichlorides. Sell and Zierold in 1874 obtained phenyl-carbonimidoyl dichloride (IX) upon chlorination of phenyl isothiocyanate in chloroform at 0°C, and Nef ( ° ) observed that under the conditions... 

An interesting new method of synthesis of carbonimidoyl dichlorides involves the addition of dichlorocarbene to aliphatic carbodiimides. Thus, reaction of phenyl(bromodichloromethyl)mercury (LXV) (the dichlorocarbene precursor) with diisopropylcarbodiimide produces isopropyl-carbonimidoyl dichloride (LXVI) in 63% yield... 

The addition of cyanogen chloride to carboxylic acid chlorides is another useful method of synthesis for acyl and aroylcarbonimidoyl dichlorides. For example, trichloroacetyl chloride reacts readily with cyanogen chloride at 50°C in an autoclave to yield the corresponding carbonimidoyl dichloride (LXVII) However, on standing, gradual dissociation into the starting materials was observed... 

Another useful synthesis of aromatic carbonimidoyl difluorides involves the reaction of the corresponding carbonimidoyl dichlorides with hydrogen fluoride. The intermediate trifluoromethyl amine (LXXX) eliminates hydrogen fluoride upon heating in the presence of potassium fluoride (66.67,128)... 

A special synthesis of carbonimidoyl dichlorides involves the addition of the sulfenyl chloride CXL to an olefin. For example, CXL adds to cyclohexene to produce the carbonimidoyl dichloride CXLI in 80% yield ( ). 

The displacement of one chloro group in carbonimidoyl dichlorides by alkoxide, phenoxide, or thiolate ion is the best general method of synthesis of 1-haloformimidates or 1-halothioformimidates. However, several other methods of synthesis are available and since nucleophilic displacement of the halo group is easily accomplished, further utilization of these reactive intermediates in organic chemistry is anticipated. 

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