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Pyrazolo[4′,3′:5,6]pyrano[2,3-b]quinoxalin-4(1H)-one: Synthesis and characterization of a novel tetracyclic ring system

✍ Scribed by Gernot A. Eller; Barbara Datterl; Wolfgang Holzer

Publisher
Journal of Heterocyclic Chemistry
Year
2007
Tongue
English
Weight
331 KB
Volume
44
Category
Article
ISSN
0022-152X

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✦ Synopsis

Abstract

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Derivatives of the hitherto unknown ring system, pyrazolo[4′,3′:5,6]pyrano[2,3‐b]quinoxalin‐4(1__H__)‐one, are synthesized in one step from the corresponding 1‐substuituted or 1,3‐disubstituted 2‐pyrazolin‐5‐ones and 3‐chloroquinoxaline‐2‐carbonyl chloride using calcium hydroxide in boiling 1,4‐dioxane. The parent system carrying no substituent in positions 1 and 3 is obtained upon treatment of the 1‐PMB (p‐methoxybenzyl) protected congener with trifluoroacetic acid. Detailed NMR spectroscopic investigations including unambiguous chemical shift assignments of all ^1^H, ^13^C, and ^15^N resonances of the obtained tetracycles are reported.

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