Benzoxazines derived from aniline and 4-hydroxybenzoic acid and from phenol and 4-aminobenzoic acid were prepared with two different synthetic approaches. When the carboxylic group reacted with epichlorohydrin, glycidylic derivatives M-1 and M-2, respectively, were obtained. The ring opening of benzoxazine and epoxy took place simultaneously with no catalyst for both monomers. Likewise, both ring-opening polymerizations took place when boron trifluoride monoethylamine (BF(3)center dot MEA) or 4-(NN-dimethylamino)pyridine was used as a catalyst for M-1. However, for M-2, when BF3-MEA was used as a catalyst, the epoxy and benzoxazine ling openings could be distinguished, and a polyether intermediate containing benzoxazine side chains could be obtained. (c) 2006 Wiley Periodicals, Inc.