Pyrazin-2-amine, 3- -, rearrangement

Strecker aldehyde are generated by rearrangement, decarboxylation and hydrolysis. Thus the Strecker degradation is the oxidative de-amination and de-carboxylation of an a-amino acid in the presence of a dicarbonyl compound. An aldehyde with one fewer carbon atoms than the original amino acid is produced. The other class of product is an a-aminoketone. These are important as they are intermediates in the formation of heterocyclic compounds such as pyrazines, oxazoles and thiazoles, which are important in flavours. 

A unique acyclic C-nucleoside containing the pyrido[2,3-. ]pyrazine nucleus 675 was prepared by the action of AcOH, whereby rearrangement of 3 -keto-2 -deoxypyrazine C-nucleoside derivatives 673 occurs via the intramolecular aminal intermediate 674, followed by furanose ring opening and subsequent aromatization (Equation 56)... 

Amine 32 was obtained on interaction of compound 14 (R = Ph) with hydrazine closure of the pyrazine ring and withdrawing of the phthaloyl protection are simultaneous processes. Photolysis or thermolysis of 1-arylazo-8-azidonaphthalenes gives rise to benzole, J]indazole N-arylim-ines (78JOC2508 [Eq. (8)]. As a result of a complicated photochemical rearrangement, isoxazolo[5,4-fe]pyridine derivative (33) is converted to N-aminopyrazole 34 in 60% yield (88H1899). 

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