US Patent 8008478 Process for the preparation of cefixime

The present invention provides an improved process for the preparation of Cefixime of formula (I), a cephalosporine antibiotic with an improved quality in regard to color and solubility. This process includes: (i) reaction of 7-β-(4-chloro-2-alkoxycarbonyl methoxyimino-3-oxobutyromido)-3-cephem-4-carboxylic acid (V) with thiourea at pH 5.0 to 6.0 at temperature 25-40° C. in water, (ii) carbon treatment to the reaction mixture in presence of sodium dithionite or ethylenediaminetetraacetic acid (EDTA) followed by filtration, (iii) acidification of the filtrate obtained in step (ii) to pH 2.0 to 3.0 with acid at 50-80° C. to give cefixime ester (IV) (iv) alkaline hydrolysis of cefixime ester of formula (IV) in water followed by acidification to pH 5.0 to 6.0, (v) precipitation of cefixime (I) by adding ketone solvent followed by acidification to pH 2.0 to 3 and (vi) isolation of solid.