Benzoxazines with thioamide linkages were successfully prepared. For this purpose, initially, thioamide containing phenolic reagents were synthesized by the Willgerodt–Kindler route using elemental sulfur, aromatic aldehydes and anilines. The obtained phenolic thioamides were then converted to benzoxazines by reacting with primary amines and formaldehyde. Moreover, the thioamide functional polymeric benzoxazine precursor was prepared with difunctional phenolic thioamide and bisaminopropyl end-functional poly(propylene glycol-block-ethylene glycol) by classical Mannich type polycondensation. The resulting precursor was solvent cast on glass plates and flexible films could be obtained after curing. All the synthesized compounds and polymers were characterized by spectral analyses. The curing behavior and thermal stabilities of benzoxazines and related polybenzoxazines were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Interestingly, DSC analyses revealed that the thioamide groups reduce the curing temperatures of benzoxazines by promoting ring opening polymerization, possibly generating thiols during heating.

中文翻译：

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Willgerodt–Kindler反应合成含硫酰胺的聚苯并恶嗪

具有硫酰胺键的苯并恶嗪已成功制备。为此，最初，使用单质硫，芳香醛和苯胺通过Willgerodt–Kindler路线合成了含硫酰胺的酚类试剂。然后通过与伯胺和甲醛反应将获得的酚硫代酰胺转化为苯并恶嗪。此外，用双官能的酚硫酰胺和双氨基丙基末端官能的聚丙二醇嵌段制备了硫酰胺官能的聚合苯并恶嗪前体。-乙二醇）通过经典的曼尼希型缩聚反应。将所得的前体溶剂浇铸在玻璃板上，固化后可获得柔性膜。所有合成的化合物和聚合物都通过光谱分析进行了表征。通过差示扫描量热法（DSC）和热重分析（TGA）研究了苯并恶嗪和相关聚苯并恶嗪的固化行为和热稳定性。有趣的是，DSC分析表明，硫酰胺基团通过促进开环聚合反应而降低了苯并恶嗪的固化温度，在加热过程中可能生成硫醇。