The reaction pathways on the curing reaction of 3-aryl substituted benzoxazine was investigated from the model reaction of 3, 4-dihydro-6, 8-dimethyl-3-phenyl-2H-1, 3-benzoxazine (1) with 2, 4-xylenol (2). The reaction was carried out at 140 °C for 5 h. N, N-Bis(2-hydroxy-3, 5-dimethylbenzyl)phenylamine (3) and N-(2-hydroxy-3, 5-dimethylbenzyl)phenylamine (4) were isolated as main products at an early stage. The reaction of 3 by the thermal treatment was studied by 1H-NMR spectroscopy. This result indicates that compound 3 produces several inter- and intramolecular rearrangement products. Based on these data, some possible reaction pathways were proposed. In the presence of p-toluenesulfonic acid monohydride, 3,3′-[4,4′-methylenediphenyl]bis(3,4-dihydro-6,8-dimethyl-2H-1,3-benzoxazine) (9) was isolated as one of the intermediates.
