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Paper | Regular issue | Vol 26, No. 3, 1987, pp.699-711
Published online, 1st January, 1970
DOI: 10.3987/R-1987-03-0699
Synthesis and Spectroscopic Studies on Some New Substituted 2-Quinoxalinecarboxamides and Their N-Oxides

Salim S. Sabri, Mustafa M. El-Abadelah, and Bassam A. Al-Bitar

*Chemistry Department, Faculty of Science, University of Jordan, Amman 11942, Jordan

Abstract

Series of new 2-(N-phenylcsrbamoyl)-3-methylquinoxaline 1,4-dioxides (I), monoxides (II,III) and their nonoxygenated analogues (IV), as well as the corresponding series lacking the C3 methyl(V-VIII) have been prepared, and their 1H-nmr spectral data analyzed. The C3-Me protons in the di-N-oxides (I) resonate at higher field (δ2.45-2.80) than in the corresponding non-oxygenated analogucs(IV) (δ=3.0). The observed upfield shift for the C3-Me protons in the di-N-oxides (I) is maximum when two methylene carbons would separate to the “interacting” phenyl and quinoxaline rings. A comparable trend is observed for the quinoxaline-1-oxides (II), whereas the isomeric 4-oxides (III) closely resemble the parent quinoxalines (IV). This behavior might be due to the predominance of the intramolecular H-bonded conformation (A) in the di-N-oxides (I) and the N-1-oxides (II). Comparative nmr study of compounds (V-VIII) is also noted.