Abstract:

To achieve industrialization of the New AB-type poly (p-phenylene benzobizoxazole) (PBO)’s homogeneous polycondensation. The AB-type monomer precursor──methyl 4-(5-nitro- 6-hydroxybenzoxazol -2-yl)benzoate’s（MNB）synthesis process was studied , and MNB’s synthesis route using 4-amino-6-nitroresorcinol hydrochloride (ANR•HCl) and 4-(methoxycarbonyl)benzoic acid (MTA) as raw materials was developed by acyl chlorination、condensation and cyclization separately or one-pot synthesis. The optimum conditions were as follows: 4-methyl-2-pentanone as solvent, Feed ratio (mol ratio) of ANR•HCl / MTA was 1.00/1.03, condensation reaction at 115 ℃ for 2.5 h. Cyclization reaction at 120 ℃ for 8.5 h after adding PPA as dehydrating agent which the feed ratio (mass ratio) of ANR•HCl / PPA was 1.00/3.25, the product was obtained with a yield of 75.68% and the purity of MNB without further purification was 96.32% by HPLC method. Structures of the products were characterized by 1HNMR and IR.

Key words: homogeneous polycondensation, methyl 4-(5-nitro-6-hydroxybenzoxazol-2-yl)benzoate, acyl-chlorination, condensation reaction, cyclization reaction, one-pot synthesis