On the purity of 2‐[ ortho ‐anilinyl]‐1,3‐benzoxazole derived from 2 H ‐3,1‐benzoxazine‐2,4(1 H )dione ( isatoic anhydride ) [1,2]

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 P 2 1 2 1 2 1 with four molecules in the unit cell (α = β = γ = 90°; a = 6.715 (2) Å, b = 12.100 (4) Å, c = 13.321 (4) Å; V = 1082.2 (6) Å 3 ). Pure 2 is characterized as a colorless, high‐melting solid; unlike the dark colored oil that is isolated if 2 contains traces of 3 . J. Heterocyclic Chem., (2010).