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, C(21)H(16)N(2)O(5), (I), and its oxidation product, ethyl 3-(9-hy­droxy-10-oxo-9,10-di­hydro­anthracen-9-yl)-5-methyl­isoxazole-4-carboxyl­ate, C(21)H(17)NO(5) (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 (16) and 85.64 (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 Å) and the pendant isoxazole ring is 89.65 (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.