Nitrilium salts amidinium salt synthesis

The great versatility of DAMN in imidazole synthesis has already been discussed (see Section 2.1.1). It also has applications under the present heading because the reagent can be converted into amidinium salts (20) by nitrilium triflates. In the presence of varying strength bases and temperatures (20) are transformed into S-aminoimidazolcs, substituted in the 4-position by nitrile (21), cyanoformimidoyl (22) or carboxamido (23) (Scheme 2.2.8), The amidinium salts (20) are isolated as mixtures of cis and trans isomers. The yields quoted for (21)-(23) have not been optimized, and their low recoveries reflect poor solubility in the usual solvents used for extraction [26, 27]. Since nitrilium salts with R = H arc unstable, it is not possible to prepare similar imidazoles which have no 2-substituent by this method. 

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