Patent ID: 7825251

Claim:
A process for preparing 6-[4-(1-cyclohexyl-1H-tetrazol-5-yl)butoxy]-3,4-dihydro-2(1H)-quinolinone (cilostazol) being substantially free of N-[4-(1-cyclohexyl-1H-tetrazol-5-yl)butyl]-6-[4-(1-cyclohexyl-1H-tetrazol-5-yl)butoxy]-3,4-dihydro-2(1H)-quinolinone, the process comprising: reacting 6-hydroxy-3,4-dihydroquinoline-2(1H)-one and 5-(4-chlorobutyl)-1-cyclohexyl-1H-tetrazole in an aqueous single phase.