1,3-benzoxazine 1, bearing 4-pyridyl moiety on the nitrogen atom, was synthesized from p-cresol, 4-aminopyridine, and paraformaldehyde. The efficient synthesis was achieved by adding acetic acid to suppress the strong basicity caused by the presence of 4-aminopyridine derivatives. Upon heating 1 at 180 degrees C, it underwent the thermally induced ring-opening polymerization. The resulting polymer was composed of two types of repeating unit, i.e., (1) Mannich-type one (-phenol-CH2-NR-CH2-) that can be expected from the general ring-opening polymerization of conventional benzoxazines and (2) a typical phenolic resin-type one (-phenol-CH2-phenol-) induced by release of 4-aminopyridine and paraformaldehyde (unit B). Another structural feature of the polymer was that it possessed a benzoxazine moiety at the chain end. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 410-416