Preparation of Nontautomeric Pyrazinones

Most such pyrazinones have been made by primary synthesis (Chapters 1 and 2) or N-alkylation of tautomeric pyrazinones (Section 5.1.2.2). The minor route by rearrangement of alkoxypyrazines (H 184) appears to be unpresented in recent literature, but there are examples of the hydrolysis of nontautomeric iminopyrazines to corresponding pyrazinones. Thus 3-imino-4-methyl-3, 4-dihy-dro-2-pyrazinamine hydriodide (191, R = H) (i.e., 2,3-diamino-l-methyl-pyrazinium iodide) underwent hydrolysis in 2 M sodium hydroxide during 1 h at 100°C to afford 3-amino-1 -methyl-2(l//)-pyrazinonc (192, R = H) ( 40%) without any evidence of Dimroth rearrangement to 3-methylamino-2-pyrazinamine 1008 l-methyl-3-methylamino-2(l//)-pyrazinimine (191, R = Me) likewise gave 1-methyl-3-methylamino-2(l//)-pyrazinone (192, R = Me) ( 50%) 1008 and other examples have been reported.598 

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