Triethylamine → [2-Chloro-4-(trifluoromethyl)thiazol-5-yl]methyl methanesulfonate

To a cold (0° C.) solution of 34.7 g (0.161 mol) of the compound of Example 4 in 150 ml of toluene there was added over a 30 minute period, 18.2 g (0.18 mol) of triethylamine. To this mixture was added 20.5 g (0.18 mol) of methanesulfonyl chloride. The reaction mixture was stirred at room temperature for 2 hours and was allowed to stand in the refrigerator for 4 days. The insoluble salt was filtered and the filtrate was concentrated under reduced pressure. The residue was dissolved in ether and the ether solution was washed with water, dried over MgSO4 and concentrated under reduced pressure to give 43.8 g (92%) of crude [2-chloro-4-(trifluoromethyl)thiazol-5-yl]methyl methanesulfonate. A 5.5 g portion of the crude material was dissolved in 50 ml of acetone. To this solution was added 2 g (0.0169 mol) of potassium xanthogenate. The reaction mixture was stirred for 2 hours at room temperature and filtered. The acetone filtrate was concentrated to give 6.9 g of oil which was chromatographed on silica gel using ether petroleum ether (1:9 v/v) as eluant. The earlier fraction was 4.1 g (69.9%) of S-[2-chloro-4-(trifluoromethyl)-5-thiazolyl]methyl O-ethyl carbonodithioate; nD25 1.5497-1.5517.