Process for preparing ondansetron

摘要

The invention relates to carbazolone derivatives of the formula <IMAGE> (I) wherein A stands for a group of formula -CH2-R(V), wherein R means a hydroxyl or 2-methyl-1H-imidazol-1-yl group; B represents a group of formula <IMAGE> (VI) wherein R1 means hydrogen or a methyl or ethyl group; or A and B together form a group of formula <IMAGE> (VII) wherein R2 means a methyl or ethyl group; or A and B together form a group of formula <IMAGE> (VIII) The above compounds are useful intermediates in the synthesis of ondansetron of formula <IMAGE> (II) chemically 9-methyl-3-[(2-methyl-1H-imidazol-1-yl)methyl]-1,2,3,9-tetrahydro-4H-c arbazol-4-one. The invention further relates to a novel process for the preparation of compounds of the formula (I) , wherein A and B are the same as in formula (I) but B may be also hydrogen. Thus, this novel process is suitable for the preparation of ondansetron itself.