ChemInform Abstract: Small and Medium Rings. Part 59. Diazepinones from Sydnones and Isopropylidenecyclobutenone. Extension of the Frontier Molecular Orbital Model for Sydnone Cycloadditions.

Abstract

210ChemInform Abstract The N-phenyl and dialkyl sydnones (I) react with the cyclobutenone (II) on heating in toluene to give the dihydrodiazepin-5-ones (III) whereas the analogues (V) together with their isomeric 4-ones (VI) are obtained from the reaction of the N-alkyl C-hydrogen sydnones (IV). The frontier MO model, as applied to sydnones, is critically examined. Extension of the simple model to the calculation of selected encounter complexes is presented. In this way, not only the preferred formation of diazepin-5-ones (III) is correctly predicted but the ratio of (V):(VI) is also satisfactorily reproduced. -The structure of (VIa) is determined by X-ray analysis (P21/c; Z=4).