Abstract
5-Substituted 2,3-dihydro-1H -pyrimido[1,2-a ]quinoxaline 6-oxides 1a -f were
synthesized by ring closure of N -acyl-N′- (o- nitroaryl)-1,3-propanediamines 2 with ethyl polyphosphate (PPE) or trimethylsilyl
polyphosphate (PPSE) to the corresponding 2-substituted 1-(o- nitroaryl)-1,4,5,6-tetrahydropyrimidines 3 , followed by spontaneous heterocyclization.
The method was extended to the synthesis of the homologous 6-aryl-1,2,3,4-tetrahydro-1,3-diazepino[1,2-a ]quinoxaline 7-oxide (1g ).
Key words
heterocycles - nitrogen - cyclizations - antibiotics - antitumor agents
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