Diaminomaleonitrile , formation from

Figure 8.4 Mechanism of tetramerization of hydrogen cyanide leading to the formation of a stable tetramer diaminomaleonitrile. (Adapted from Orgel and Lohrman [24])...

The synthesis of 1,2,5-thiadiazoles from a-diamines was studied as early as 1897 when Michaelis attempted the preparation of the parent compound by reaction of ethylenediamine with sulfur dioxide. The product, however, was bissulfimic acid (28) which readily lost sulfur dioxide to form the betaine (28a). Later Shew reported that 3,4-dicyano-l,2,5-thiadiazole (30) results from the reaction of cis-diaminomaleonitrile (29, HCN tetramer) with thionyl chloride, a reaction which is analogous to 2,1,3-benzothiadiazole formation from o-phenylenediamines. The synthesis of the parent 1,2,5-thiadiazole and some alkyl analogs (32) was accomplished by reaction of salts of... 

Diaminomaleonitrile (1) is formed as a stable tetramer from hydrogen cyanide. The formation of the tetramer is enhanced in dilute solution and at low temperature. 

Methods of imidazole synthesis based on the use of diaminomaleonitrile (DAMN (13), R = II) have proliferated in recent years. The reagent is now readily available from chemical distributors at a price which makes its use reasonably economical. Some of these methods of synthesis fall under the present heading others involve 1,5 bond formation (see Section 2.2), or 1,2 and 2,3 bond formation (see Section 3.1.1). 

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