4-(6-羟基-5-硝基-2-苯并唑基)-2,6-二羟基苯甲酸的合成

研究了以2，6-二羟基对苯二甲酸（2，6-DH-TA）与4-氨基-6-硝基间苯二酚盐酸盐（ANR·HCl）为原料经酰氯化和N-酰化一锅法及环合等一系列反应合成得到中间体4-（2，4-二羟基-5-硝基苯基）氨甲酰基]-2，6-二羟基苯甲酸（2，6-DH-NCA）和2，6-二羟基改性PBO的AB型酸类新单体的关键前体4-（6-羟基-5-硝基-2-苯并唑基）-2，6-二羟基苯甲酸（2，6-DH-NBA），并对其反应条件进行了优化。结果表明：对于酰氯化和N-酰化一锅法反应，以1，4-二氧六环为酰氯化溶剂，SOCl₂为酰氯化试剂，酰氯化时间2h，N-酰化溶剂为4-甲基2-戊酮，N-酰化温度105℃，N-酰化时间4h，N-酰化缚酸剂为三乙胺，n（2，6-DH-TA）：n（ANR·HCl）：n（SOCl₂）：n（三乙胺）=1.0：1.0：2.0：0.5，经乙醇精制，2，6-DH-NCA收率80.31%，HPLC纯度（质量分数）98.57%；环合反应，以二乙二醇二甲醚为溶剂，多聚磷酸（PPA）为脱水剂，PPA中P₂O₅质量含量85%，w（2，6-DH-NCA）：w（PPA）=1：8.6，反应温度135℃，反应时间6h，2，6-DH-NBA收率83.76%，HPLC纯度99.25%。中间体和产物结构经FTIR、¹H NMR和EI-MS表征确认。

Synthesis of 4-(6-hydroxy-5-nitro-2-benzoxazolyl)-2,6-dihydroxybenzoic acid

The intermediate 4-(2,4-dihydroxy-5-nitrophenyl)carbamoyl]-2,6-dihydroxy-benzoic acid (2,6-DH-NCA) and a key precursor of AB-type acid new monomer of 2,6-dihydroxyl modified PBO 4-(6-hydroxy-5-nitro-2-benzoxazolyl)-2,6-dihydroxybenzoic acid (2,6-DH-NBA) were successfully synthesized through a series of reactions, including one pot reaction of the acylchlorination and Nacylation, and the dehydration cyclization reaction by using 2,6-dihydroxyterephthalic acid (2,6-DH-TA) and 4-amino-6-nitroresorcinol hydrochloride (ANR·HCl) as materials. The optimal experimental conditions of one pot reaction of acylchlorination and N-acylation and the dehydration cyclization were obtained. For the one pot reaction of acylchlorination and N-acylation, with the 1, 4-dioxane as acylchlorination solvent and SOCl₂ as acylchlorination reagent, the acylchlorination time was 2h; with the triethylamine as the deacid reagent of N-acylation, the temperature of N-acylation at 105℃ and the reaction time was 4h, n(2,6-DH-TA):n(ANR·HCl):n(SOCl₂):n(triethylamine) was 1.0:1.0:2.0:0.5, the yield of 2,6-DH-NCA was 80.31% and the purity was 98.57% as determined by HPLC. For the dehydration cyclization reaction, with the diethylene glycol dimethyl ether as solvent and the polyphosphoric acid(PPA) as dehydrant, and the content of P₂O₅ in PPA of 85%, the reaction temperature at 135℃, the reaction time was 6h, w(2,6-DH-NCA):w(PPA) was 1:8.6, the yield of 2,6-DH-NBA was 83.76%, and the purity was 99.25% as determined by HPLC.