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Synthesis 2002(18): 2687-2690
DOI: 10.1055/s-2002-35980
DOI: 10.1055/s-2002-35980
PAPER
© Georg Thieme Verlag Stuttgart · New York
An Efficient Synthesis of 2,3-Dihydro-1H-pyrimido[1,2-a]quinoxaline 6-Oxides
Further Information
Received
15 July 2002
Publication Date:
06 December 2002 (online)
Publication History
Publication Date:
06 December 2002 (online)
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
- 1
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References
Due to its aprotic character, PPSE is less prone to promote deacylation reactions and led to better yields than PPE.