Isonitriles from alkyl halides

Table 8.1. Preparation of isonitriles from alkyl halides and metal cyanides.

A further method for preparing hydantoins is the N-alkylation of other hydantoins with reactive alkyl halides in the presence of strong bases [154]. Hydantoinimines have been synthesized from polystyrene-bound isonitriles by an Ugi-type multicomponent condensation (Entry 15, Table 15.13). 

Treatment of a-halo ethers with metallic cyanides such as cuprous, mercuric, or silver cyanides gives the corresponding cyano ethers the alkali cyanides are without effect. Very little of the corresponding isonitriles are encountered despite the fact that these compounds often result from the interaction of heavy-metal cyanides and alkyl halides. Generally, cuprous cyanide, the most commonly used reagent, is suspended in dry anhydrous ether or dry benzene and treated with the halo ether under gentle reflux (55-80%). 

A still unresolved problem is the structure of the often used adducts from phosphorus trihalides and carboxylic acid amides, which might be described by the formulae (8) or (9). With the aid of in situ generated adducts of acid amides and PX3 amidines, isonitriles, quinazolinones, alkyl chlorides, aminomethylenediphosphonic acids, carbamoyl halides, triformylaminomethane, 1,3,4-oxadia-zoles, sulfides (from sulfoxides), nitriles (from primary nitro compounds)" and bromoqui-nolines (from methoxyquinolines)" have been prepared. 

When an alkyl halide is treated with silver cyanide, reaction takes place in the usual way a silver halide and an organic compound are formed. The product, however, is not an alkyl cyanide, as is the case when potassium cyanide is used, but an isomeric compound. The substances prepared from silver cyanide are called isocyanides, isonitriles, or carbylamines. The last name is given to them on account of the fact that they unite with acids and thus resemble the amines. The addition-products do not, however, resemble salts in their chemical properties. When hydrogen chloride is passed into an ethereal solution of methyl isocyanide, a compound of the formula 2CH3NC.3HCI is formed, which is decomposed when brought into contact with water. 

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