O-17 NMR-STUDIES OF ELECTRONIC AND STERIC INTERACTIONS OF SUBSTITUTEDQUINOXALINE-2(1H),3(4H)-DIONES

O-17 nmr studies, at natural abundance, of substituted quinoxarine-2(1 H),3(4H)-diones demonstrate that the O-17 chemical shift data can prov ide new insights into steric and electronic interactions due to long r ange substituent effects on the aromatic ring. The role of considerabl e ''keto'' character and torsion angle deformation of the diamide grou p in solution is emphasized.