Syntheses and crystal structures of a nitro-anthracene-isoxazole and its oxidation product

The syntheses and structures of an unexpected by-product from an iodination reaction, namely, ethyl 5-methyl-3-(10-nitroanthracen-9-yl)isoxazole-4-carboxylate, C21H16N2O5, (I), and its oxidation product, ethyl 3-(9-hydroxy-10-oxo-9,10-dihydroanthracen-9-yl)-5-methylisoxazole-4-carboxylate, C21H17NO5 (V) are described. Compound (I) crystallizes with two molecules in the asymmetric unit in which the dihedral angles between the anthracene fused-ring systems and isoxazole ring mean planes are 88.67 14;(16) and 85.64 14;(16)°; both molecules feature a disordered nitro group. In (V), which crystallizes with one molecule in the asymmetric unit, the equivalent dihedral angle between the almost planar anthrone ring system (r.m.s. deviation = 0.029 14;Å) and the pendant isoxazole ring is 89.65 14;(5)°. In the crystal of (I), the molecules are linked by weak C-H⋯O interactions into a three-dimensional network and in the extended structure of (V), inversion dimers linked by pairwise O-H⋯O hydrogen bonds generate R 2 2(14) loops.