The Crystal Structure of a Bridged 1,2,3-Oxadiazolidin-5-one Derivative
3-(2-Allylphenyl)-4-phenylsydnone (1) undergoes in solution an intramolecular, 1,3-dipolar cycloaddition reaction to give 2-oxo-1-phenyl-1,5-methano-1,2,4,5,6,11-hexahydro[1,2,3]oxadiazolo[3,2-a]cinnoline (2). The unique 1,2,3-oxadiazolidin-5-one structure of this molecule has been proved by X-ray analysis. The crystal structure has been solved by direct methods and refined by full-matrix least squares calculations to R = 0,046. The crystal system is orthorhombic, space group Pbca, with unit cell dimensions a = 10,546,b = 15,482, c = 16,531A.