A METHOD OF ELIMINATING SULFONE ANALOG IN THE SYNTHESIS OF PYRIDINE-BENZIMIDAZOLE SULFOXIDES

摘要

Process for the preparation of pyridine-benzimidazole sulfinyl compounds such as Omeprazole, Lansoprozole and Pantoprozole of general formula (I), wherein the ring A may optionally be substituted, R1 is hydrogen or an N-protecting group, each of R2, R3 and R4 represent (1) a hydrogen atom, (2) alkyl group which may be substituted with halogen atom(s) or (3) an alkoxy group which may be optionally substituted with halogen atom(s) or alkoxy; or its salt. Sulphone analogs of the corresponding compounds as impurity are formed during oxidation of the precursor thioether of the compèound of formula (I). A process is provided for the elimination of sulphone analogs in contaminated products. The purification process comprises treatment of semi-pure benzimidazole derivatives with solid K2CO3 in alcohol medium at elevated temperatures.