1-Chloro-2-fluorobenzene → 1-Chloro-2-fluoro-3-(methylsulfanyl)benzene

A solution of 10 g (grams) (76 mmol (millimoles)) of 1-chloro-2-fluorobenzene in 75 mL (milliliters) of dry tetrahydrofuran (THF) was cooled with a dry ice/acetone bath and 34 mL (84 mmol) of 2.5M butyllithium was added dropwise under a nitrogen blanket over 45 min with stirring and cooling. The resulting solution was stirred for 2 hours at -78° C. A solution of 8.1 mL (91 mmol) of dimethyl disulfide in 10 mL of dry THF was added with stirring over a 30-min period keeping the temperature below -65° C. The mixture was allowed to warm to ambient temperature for 1 hour. It was then diluted with 75 mL of water. The resulting mixture was extracted with diethyl ether and the ether extract was dried over sodium sulfate and concentrated by evaporation under reduced pressure to obtain a yellow oil. This oil was purified by flash chromatography on 230-400 mesh silica gel eluting with a hexane/ethyl acetate mixture to obtain 9.0 g (69 percent of theory) of the title compound as a light yellow oil.