On the Purity of 2-[ortho-Anilinyl]-1,3-benzoxazole Derived from 2H-3,1-Benzoxazine-2,4(1H)dione (Isatoic Anhydride)

The Lewis acid catalyzed synthesis and chromatographic purification of isatoic anhydride-derived 2-(2'-anilinyl)-1,3-benzoxazole (2) can result in the co-isolation of 2 and a light pink colored impurity (<5%). This latter species has been identified (NMR, single crystal X-ray diffraction, mp) as 2'-hydroxy-2-aminobenzanilide (3), which represents a predictable intermediate in the formation of 2. Compound 3 crystallizes in an orthorhombic crystal system of space group P2(1)2(1)2(1) with four molecules in the unit cell (alpha = beta = gamma = 90 degrees; a = 6.715 (2) angstrom, 6 = 12.100 (4) angstrom, c = 13.321 (4) angstrom; V = 1082.2 (6) angstrom(3)). Pure 2 is characterized as a colorless, high-melting solid; unlike the dark colored oil that isolated if 2 contains traces of 3.