Reactions of 5,8-dichloro-2,3-dicyanoquinoxaline with amines and hydrazines. A new and efficient synthetic approach to 3-amino-5,8- dichloroflavazoles

摘要

Reactions of 5,8-dichloro-2,3-dicyanoquinoxaline with primary amines and hydrazines under different experimental conditions were investigated. Alkylamines provided novel 3-alkylamino-5,8-dichloro-2-cyanoquinoxalines and N-alkyl-(5,8-dichloro-3-alkylamino-2-quinoxalinyl)carboxamidines in high yields. Alkylhydrazines and lithium arylhydrazinides gave previously unattainable 1-alkyl-3-amino-5,8-dichloroflavazoles and 3-amino-1-aryl-5,8-dichloroflavazoles in good to near quantitative yields whose molecular structure was confirmed by X-ray crystallography of 3-[N,N-bis(4-chlorobenzoyl)amino]-5,8-dichloro-1- phenylflavazole. Reaction with hydrazine gave 5,8-dichloro-3-hydrazino-2- quinoxalinylcarboxamidrazone quantitatively, which was converted to the parent compound of this class of flavazoles, 3-amino-5,8-dichloroflavazole, in high yield by a pyrolytic process involving loss of hydrazine.