2-[2-(5-nitro-2-thienyl)ethenyl]-4H-3,1-benzoxazine-4-one, 2-[2-(4-nitro-phenyl)ethenyl]-4H-3,1-benzoxazine-4-one and 6,7-dimethoxy-2-[2-(4-nitrophenyl)ethenyl]-4H-3,1-benz-oxazine-4-one

The three title compounds, i.e. C14H8N2O4S, (I), C16H10N2O4, (II), and C18H 14N2O6, (III), respectively, are almost planar. The benzoxazinone and nitro aryl moieties are in a trans configuration with respect to the ethylene gro up. The nitro group in all three molecules is almost coplanar with the aryl substituent and shows quite strong conjugation with the rest of the pi-sys tem of the molecules. The molecules of (I) form layers along the crystallog raphic b axis, with a distance between adjacent layers of about 3.5 Angstro m. However, the molecules of (II) and (III) form stacks, with distances bet ween adjacent molecules of about 6.0 and 3.6 Angstrom, respectively. [GRAPHICS]