Synthesis 2002(18): 2687-2690
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

María B. García, Liliana R. Orelli, María L. Magri, Isabel A. Perillo*
Departamento de Química Orgánica, Facultad de Farmacia y Bioquímica, Junín 956 (1113) Buenos Aires, Argentina
Fax: +54(1)149648250; e-Mail: iperillo@ffyb.uba.ar ;
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Publikationsverlauf

Received 15 July 2002
Publikationsdatum:
06. Dezember 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).

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5

Due to its aprotic character, PPSE is less prone to promote deacylation reactions and led to better yields than PPE.