the mixture was stirred at 55 u00b0 c for 4 h the hot mixture was diluted with water 12 ml and cooled to 0 u00b0 c a white solid that precipitated was filtered off and dried under high vacuum the yield of 3 carboxymethylsulfinyl 7 fluoro 1 methyl 4 quinolone was 185 mg 72 7 5 in this example flosequinan is prepared according to the following protocol in a clean and dry 12 l glass reactor equipped with a back suction trap plus a naoh 25 trap at the outlet and a back suction trap in the inlet 3 840 l of toluene were charged and cooled to u2212 45 u00b0 c using a dry ice acetone bath using appropriate safety precautions 832 g of phosgene were then passed through the cold toluene while stirring to prepare a 20 wt wt solution the addition of the phosgene took approximately 3 5 hours separately into a clean and dry 22 l glass reactor equipped with the above described types of back suction traps 399 g of starting material formula i was added with stirring to 4 37 l of deionized water a separate 6 8 solution of sodium carbonate in water was also prepared by adding 297 g of sodium carbonate to 4 37 l of deionized water using a clean addition funnel.