Propargyl containing thermally curable benzoxazine precursors in the main chain have been synthesized from iodo functional bisbenzoxazine and diacetylenes by Sonogashira coupling reaction. For this purpose, 4,4'-isopropylidenediphenol (Bisphenol A) was reacted with formaldehyde and iodoaniline to form diiodobisbenzoxazine (DIBB). Sonogashira coupling reaction between DIBB and diacetylene bisether (DABE) or diacetylene bisbenzoxazine (DABB) catalyzed by palladium tetrakistriphenylphosphine yields the corresponding main-chain polybenzoxazine precursors with the molecular weights around 2300-3500 Da. The structures of the monomers and the resulting polymers are confirmed by FT-IR and H-1 NMR spectral analysis. Curing behaviors of both the monomer and polymers were studied by differential scanning calorimetry (DSC). Thermal properties of the cured polymers were also investigated by thermogravimetric analysis (TGA).