PROCESSES FOR PREPARING 8-AMINO-4-OXO-2-(TETRAZOL-5-YL)-4H-1-BENZOPYRAN OR ITS SALT AND SYNTHETIC INTERMEDIATES THEREOF

摘要

Processes for preparing 8-amino-4-oxo-2-(tetrazol-5-yl)-4H-1-benzopyran or its salt and synthetic intermediates thereof are provided to improve preparation yield of the compound by using N,N'-bis{3-[1,3-dioxo-3-(tetrazol-5-yl)]propyl-2-hydroxyphenyl} terephthal amide as intermediates, and reduce the preparation costs by recycling the terephthalic acid obtained together with the final product into a starting material. The process for preparing 8-amino-4-oxo-2-(tetrazol-5-yl)-4H-1-benzopyran or its salt comprises the steps of: (a) cyclizing N,N'-bis{3-[1,3-dioxo-3-(tetrazol-5-yl)]propyl-2-hydroxyphenyl} terephthal amide in the presence of acid to prepare N,N'-bis{4-oxo-2-(tetrazol-5-yl)-4H-1-benzopyran-8-yl} terephthal amide; and (b) hydrolyzing the N,N'-bis{4-oxo-2-(tetrazol-5-yl)-4H-1-benzopyran-8-yl} terephthal amide, wherein the acid is hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, citric acid, oxalic acid, C1-C6 alkylsulfonic acid, benzene sulfonic acid or p-toluene sulfonic acid; and the N,N'-bis{3-[1,3-dioxo-3-(tetrazol-5-yl)]propyl-2-hydroxyphenyl} terephthal amide is prepared by reacting N,N'-bis{3-acetyl-2-hydroxyphenyl} terephthal amide with compounds represented by the formula(5) in which R is C1-C6 alkyl, phenyl or phenyl-C1-C6 alkyl.