Autoxidation of 3-phenyl-2H-1, 4-benzoxazine 8 gives 2-hydroxy-3-phenyl-2H-1, 4- benzoxazine 13, 3-phenyl-2H-1, 4-benzoxazin-2-one 11, and 2-phenylbenzoxazole 10 according to the conditions. Oxidation of 8 with DDQ in the presence of air gave mainly the bisacetal 17 but in the absence of air the major product was trans-Δ2, 2′-bi-(3-phenyl-2H-1, 4-benzoxazine) 21a. Corresponding dimers were obtained from the 3-p- ...
