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).
5 取代的 2,3-二氢-1H-
嘧啶并[1,2-a]
喹喔啉 6-氧化物 1a-f 是通过 N-酰基-N′-(邻硝基芳基)-1、通过 N-酰基-N′-(邻硝基芳基)-1,4,5,6-四氢
嘧啶 2 与多
磷酸乙酯 (PPE) 或多
磷酸三甲基
硅酯 (PP
SE) 的环闭合,合成相应的 2-取代 1-(邻硝基芳基)-1,4,5,6-四氢
嘧啶 3,然后自发杂环化。 该方法还可用于合成同源的 6-芳基-1,2,3,4-四氢-1,3-二氮杂卓[1,2-a]
喹喔啉 7-氧化物(1g)。