4-(5-硝基-6-羟基-7-甲基苯并噁唑-2-基)苯甲酸甲酯的合成

针对聚对苯撑苯并二噁唑(PBO)纤维的抗压性能差和成型困难等问题,提出并合成出一种新单体的前体化合物4-(5-硝基-6-羟基-7-甲基苯并噁唑-2-基)苯甲酸甲酯(MMNB),总收率56.42%、纯度97.5%;可用于制备AB型单体和甲基改性PBO纤维,以改善PBO纤维的加工性能及热交联后提高轴向抗压能力。结果表明:对苯二甲酸单甲酯(MTA)先经酰氯化,然后在二氯甲烷溶剂中、三乙胺作缚酸剂与2-甲基-4-氨基-6硝基间苯二酚盐酸盐(MANR·HCl)缩合一锅法制备中间体4-[N-(2,4-二羟基-3-甲基-5-硝基苯基)氨甲酰基]苯甲酸甲酯(MNHB),收率为73.65%;MNHB在二乙二醇二甲醚溶剂中多聚磷酸作用下环合脱水合成MMNB,收率为76.61%;并经IR、MS和 ¹H NMR确认。

Synthesis of methyl 4-(5-nitro-6-hydroxy-7-methylbenzoxazol-2-yl) benzoate

Aiming to change the poor compression performance and processing difficulties of PBO fiber,a novel monomer precursor compound,methyl 4-(5-nitro-6-hydroxy-7-methylbenzoxazol-2-yl) benzoate (MMNB),was proposed,and synthesized with total yield of 56.42%,and a purity of 97.5%. It can be used for the preparation of AB-type monomer and methyl modified PBO fiber,to improve the processability of PBO fibers and increase the axial compressive strength after heat-crosslinking. The results showed that intermediate methyl 4-[N-(2,4-dihydroxy-3-methyl-5-nitrophenyl) carbamoyl] benzoate(MNHB) was one-pot prepared by the chloride of monomethyl terephthalate (MTA),then condensed with 2-methyl-4-amino-6-nitroresorcinol hydrochloride (MANR·HCl) in methylene chloride solvent and triethylamine as acid binding agent,yield reached 73.65%. MMNB was synthesized by cyclization dehydration of MNHB in diglyme solvent with the presence of polyphosphoric acid,and yield reached 76.61%. Their molecular structures were confirmed by IR,MS and ¹H NMR.