Unequivocal synthesis of 6-arylpteridines by intramolecular cycloaddition of azahexatrienes

Abstract

Treatment of 6-amino- 5- benzylideneaminopyrimidines, readily prepared by condensation of 5,6-diaminopyrimidines with aromatic aldehydes, with an excess of triethyl orthoformate in dimethylformamide afforded the corresponding 6-ethoxymethyleneamino-derivatives, which underwent thermal cyclization through valence isomerization and subsequent aromatization by elimination of ethanol to give 6-arylpteridines. Treatment of 6-amino-5-benzylidene-aminopyrimidines with dimethylformarnide diethyl acetal gave the corresponding 6-dimethylaminomethyleneamino-derivatives, which on heating in tetramethylene sulphone also yielded 6-arylpteridines.