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

Abstract

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.