Masatsugu Higuchi

A new synthesis of purines

Treatment of 6-aminopyrimidines with 4-phenyl-1,2,4-triazoline-3,5-dione gave the Michael-type adducts, 6-amino-5-(4-phenylurazol-1-yl)pyrimidines; fusion of these adducts with several aryl aldehydes gave the corresponding 8-arylpurines.

Unequivocal synthesis of 6-arylpteridines by intramolecular cycloaddition of azahexatrienes

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.

Synthesis of xanthines by cyclization of the Michael-type adducts from 6-aminouracils and diethyl azodiformate

Treatment of the Michael-type adducts from 6-alkylamino-1,3-dimethyluracils and diethyl azodiformate (DAD) with oxidizing agents such as nitrobenzene, lead tetra-acetate, and lead dioxide as well as DAD itself caused dehydrogenation, followed by thermal cyclization, to give the corresponding theophyllines. Treatment of 6-alkyl-aminouracils with an excess of DAD gave directly the corresponding xanthine derivatives. Reactions of 6-amino-5-(1,2-bisethoxycarbonylhydrazino)-1,3-dimethyluracil with aromatic aldehydes and with dimethylformamide diethyl acetal gave the corresponding 8-aryltheophyllines and 8-dimethylaminotheophylline, respectively.

Synthesis of purines by cyclization of the Michael-type adducts from 6-aminopyrimidines and 4-phenyl-1,2,4-triazoline-3,5-dione

Treatment of 6-amino-and 6-alkylamino-uracils with 4-phenyl-1,2,4-triazoline-3,5-dione(PTAD)gave Michael-type adducts, viz. 6-amino-(1) and 6-alkylamino-5-(3,5-dioxo-4-phenyl-1,2,4-triazolin-1-yl)uracils (2). The oxidative cyclization of (2) with nitrobenzene gave the corresponding xanthine derivatives, which were also obtained by the condensation of (1) with the aromatic aldehydes. The Michael-type adducts from 2-methyl- and 2-phenyl-6-alkylamino-4-hydroxypyrimidinies and PTAD gave the corresponding 9-alkylpurine-6,8(1H,7H)-diones, by direct cyclization upon treatment with nitrobenzene.

New synthesis of purines by the reaction of diethyl azodicarboxylate with 6-alkylaminouracils

Treatment of 6-alkylamino-uracils with excess of diethyl azodicarboxylate gave the respective xanthine derivatives; reaction of 6-amino-5-(1,2-diethoxycarbonyl-hydrazino)-1,3-dimethyluracil with aryl aldehydes also gave the corresponding xanthine derivatives.