Dioxane

The benzoxazine monomer, 3-[(furan-2-yl)methyl]-6-methyl-3,4-dihydro-2H-1, 3-benzoxazine, was prepared by a one-pot Mannich reaction like the syntheses of other derivatives reported in the literature [33, (link)46, (link)47] (link). Herein, furfurylamine (Alfa Aesar, Haverhill, MA, USA, 2.43 g, 25 mmol), paraformaldehyde (Merck, Kenilworth, NJ, USA, 1.50 g, 50 mmol), and para-cresol (Merck, 2.71 g, 25 mmol) were dissolved in dioxane (RCI Labscan, Bangkok, Thailand, 25 mL). The mixture was refluxed for 6 h to obtain a clear dark yellow solution. The solvent was removed by a rotary evaporator to obtain a brown liquid. To remove impurities, 25 mL of dichloromethane was added to the brown liquid; the obtained solution was extracted by 3 N NaOH (25 mL) for three times and subsequently by 25 mL of deionized water for three times. The extracted product of the benzoxazine (I) was dried using anhydrous sodium sulfate (Ajax Finechem, Wollongong, Australia). The anhydrous sodium sulfate was removed by decantation. Then, the dichloromethane solvent was removed by a rotary evaporator and consequently, the viscous brown liquid of the benzoxazine (I) was obtained.