Heterocyclic imines and pyrazine N-oxides from iminodiacetonitrile.

PART I. HETEROCYCLIC IMINES FROM IMIHODIACETONITRILE. Reaction of N-benzyliminodiacetonitrile with alcoholic ammonia under pressure but best as sodamide in formamide under nitrogen gives the imidine, 4-benzyl-2,6-diiminopiperazine. The imino groups of this compound undergo stepwise displacement reaction with water and hydroxylamine. The hydroxylamine product, 4-benzyl-2,6-dihydroxyiminopiperazine, is also obtained by cyclisation of the bisamidoxime and direct from the dinitrile. The dinitrile with aniline and 2-aminopyridine (as anion) affords 4-benzyl-2-imino-6-phenyliminopiperazine and the 6-(2-pyridyl)-imino analogue, although attempts to prepare these compounds from the imidine were abortive. Iminodiacetonitrile itself with sodamide in formamide gives 2,6-diformyliminopiperazine. Iminodiacetonitrile and its N-acetyl and benzoyl derivatives add hydroxylamine at room temperature giving acyclic bisamidoximes which with aqueous alcoholic hydroxylamine hydrochloride at reflux temperature afford the corresponding 2,6-dihydroxyiminopiperazines which are prepared directly from the dinitriles by refluxing with aqueous alcoholic mixture of hydroxylamine and its hydrochloride. However, tri(cyanomethyl)amine under similar reaction condition yields the acyclic trisamidoxime. Nevertheless, the trinitrile with sodamide in formamide gives the imidine, 2,6-diiminopiperazine-4-acetonitrile, which is hydrolysed by water to 6-imino-2-oxopiperazine-4-acetamide. PART II. PYRAZINE N-OXIDES FROM IMINODIACETONITRILE. Iminodiacetonitrile with hydroxylamine under optimum reaction conditions (which was discovered by experiment) affords 2,6-dihydroxyirninopiperazine with hydroxylamine hydrochloride together with 2-amino-6-hydroxyaminopyrazine l-oxide. The former separates as its insoluble complex and after this has been filtered off, the latter crystallises out from the solution as monohydrate. Catalytic reduction of the latter using Adam's catalyst results in uptake of one molecular equivalent of hydrogen and formation of 2,6-diaminopyrazine 1-oxide. Acetylation at room temperature then gives 2,6-diacetamidopyrazine-1-oxide. Treatment of 2,6-dihydroxyiminopiperazine with 10% palladium-on-charcoal catalyst in boiling o-dichlorobenzene affords 2,6-diaminopyrazine in poor yield, which with acetic-anhydride at room temperature gives 2,6-diacetamidopyrazine and is also obtained by deoxygenation of 2,6-diacetamidopyrazine 1-oxide using sodium dithionite