Lawesson's reagent → N-[[6-Methoxy-2-(2,2,2-trifluoroethoxy)-5-(trifluoromethyl)-1-naphthalenyl]thioxomethyl]-N-methylglycine, Methyl Ester

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Reaction Steps

Lawesson's reagent (3.20 g, 0.6 eq) was added to a stirred solution of N-[[6-methoxy-2-(2,2,2-trifluoroethoxy)-5-(trifluoromethyl)-1-naphthalenyl]carbonyl]-N-methylglycine, methyl ester, prepared by the process of Example 3, Step 1 (6.00 g, 13.2 mmol) in toluene (60 mL) at room temperature under argon. The reaction was heated to reflux for 111/2 hours, with more Lawesson's reagent (4.8 g, 0.9 eq) added in two portions after 21/4 and 83/4 hours. The reaction was cooled to room temperature and diluted with methylene chloride (300 mL). The crude reaction mixture was preabsorbed onto silica gel and flash chromatographed (petroleum ether→7:3 petroleum ether:ethyl acetate eluent gradient, silica) to provide the product as a yellow foam (3.94 g, 64%). A small sample was washed with petroleum. The filtrate was evaporated to dryness to provide a yellow solid for analysis, m.p. 104°-105° C.

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