6-氟-色满-2-羧酸的合成

Synthesis of 6-Fluro-3,4-dihydro-2H-benzopyran-2-carboxylic Acid

对-氟苯酚与硫酸二甲酯进行酚甲醚化得到对-氟苯甲醚,然后在AlCl3催化下与顺丁烯二酸酐进行Friedel-Crafts酰基化,进一步去甲基化得到4-(4-氟-2-苯酚)-4-氧代-2-丁烯酸,在碱性条件下,经自身环化得到6-氟-4-氧代-3,4-二氢-2H-1-苯并吡喃-2-甲酸,关环步骤的收率为81%;最后在乙酸介质中,用5%Pd/C催化加氢得到外消旋的6-氟-3,4-二氢-2H-1-苯并吡喃-2-羧酸。该工艺总收率为51.87%,具有合成路线短、收率高、原料易得、条件温和、操作简单的特点,适宜工业化生产。

4-fluorophenol was firstly etherification with dimethyl sulfate to give 4-fluoroanisole, which was acylation with maleic anhydride with AlCl3 as catalyst, and then demethylation to afford 4-（3-Fluorophenyl）-4-oxo-but-2-enoic acid; The latter was transformed into 6-fluoro-4-oxo-4H-chromene-2-carboxylic acid by treatment with NaHCO3 solution via intramolecular cyclization with a yield of 81%. The object product 6-fluro-3,4-dihydro- 2H-benzopyran-2-carboxylic acid was obtained from the reduction of chromene-2-carboxylic acid by hydrogenation catalyzed by 5% Pd/C in acetic acid. The proposed process has an overall yield of 51.87 % from 4-fluorophenol, perspective to be industrialized due to the short process, high yield, readily available agents, the mild conditions, and easily operations.