Conversion of trans- to cis-N,N-dimethyl-9-{8 3-(4-methyl-1-piperazinyl)propylidene{9 -thioxanthene-2-sulfonamide and recovery of the cis-isomer

摘要

Trans-N,N-dimethyl-9-[3-(4-methyl-1-piperazinyl)propylidene]-thioxanth ene-2-sulfonamide is isomerized to the cis-isomer by contacting the trans-isomer with strong base in a polar organic solvent. By using an organic solvent in which the solubility of the cis-isomer is substantially less than that of the trans-isomer, the cis-isomer can be selectively precipitated from said solvent, thereby favoring additional isomerization to the cis-isomer in the supernatant, and separated.