17O NMR studies of electronic and steric interactions of substituted quinoxaline-2(1H),3(4H)-diones

¹⁷O nmr studies, at natural abundance, of substituted quinoxaline-2(1H),3(4H)-diones demonstrate that the ¹⁷O chemical shift data can provide new insights into steric and electronic interactions due to long range substituent effects on the aromatic ring. The role of considerable “keto” character and torsion angle deformation of the diamide group in solution is emphasized.