Monatshefte ffir Chemic 124, 783-787 (1993) Monatshefle f/it Chem/e Chemical Monthly © Springer-Verlag 1993 Printed in Austria Carbon-13 Nuclear Magnetic Resonance of Some Derivatives of 3-Methyl-4,1-benzoxazepine-2,5-dione N. Khan 1, M. S. Ansari l'*, and W. Robien 2 1 Department of Chemistry, Quaid-i-Azam University, Islamabad, Pakistan 2 Institut fiir Organische Chemic, Universit/it Wien, Wien, Austria Summary. JaC chemical shift assignment of seven N-derivatives of 3-methyl-4,1-benzoxazepine-2,5- dione is reported. The assignment has been done with the help of J-modulated spectra and by comparison with the values of resembling segments reported in the reference. It has been found that the substituent on nitrogen atom has no significant effect on the l 3C chemical shift of the skeleton. Keywords. Benzoxazepinedione; Seven membered heterocycles; 13C NMR analysis. 13C.NM R einiger Derivative des 3-Methyi-4,l-benzoxazepin-2,5-dions Zusammeufassung. Es werden die laC-NMR-Verschiebungszuordnungen von sieben N-Derivaten yon 3-Methyl-4,1-benzoxazepin-2,5-dionen diskutiert. Die Zuordnungen erfolgten fiber J-modulierte Spektren und Vergleich yon entsprechenden Literaturdaten/ihnlicher Molekfilsegmente. Es zeigte sich, dab die Substitution am Stickstoff keinen signifikanten EinfluB auf die ~ aC-chemischen Verschiebungen der Skelettkohlenstoffatome hat. Benzoxazepinediones are synthetic heterocyclic compounds which may have different positions of nitrogen and oxygen atoms in the ring [-1-8]. Some compounds of this class are reported to have wide ranging medicinal importance [9-13]. Inspite of the fact that these compounds are syntheti c on one hand and have considerable medical significance on the other, only few of their derivatives have been reported in the Ref. [1-13]. Even for the reported compounds detailed study of proton NMR in general and taCNMR in particular is almost lacking. These facts stimulated us to undertake a systematic study of some selected compounds and a series of their derivatives. The scope of our investigation includes synthesis, structure elucidation, observation of biological activity and physico-chemical characterization. However, as a part of the study we report in this paper a comparative 13C chemical shift assignment of seven derivatives of 3-methyl-4,1-benzoxazepine-2,5-dione (MBOAD). 4,1-Benzoxazepine-2,5-diones (BOAD) have a general formula given by the structure I. Although a number of derivatives may be synthesized by different