ethyl phosphonothioic dichloride, anhydrous → O,O-bis(6-fluoro-2-pyridinyl) ethylphosphonothioate

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Reaction Steps

Into a 500 milliliter (ml) flask were placed 22 grams (g) (0.15 mole (m)) of the sodium salt of 6-fluoro-2-pyridinol, 1 gram HgCl2 and 200 milliliters of acetonitrile. The mixture was stirred while 9.5 grams (0.075 mole) of ethylphosphonothioic dichloride was added. An exotherm from 24° C. to 38° C. was obtained. The mixture was stirred at 40°-45° C. for five hours and allowed to cool. The insolubles were filtered off and the liquid phase distilled under reduced pressure until all the solvent was removed. The resulting oil was taken up in 300 milliliters of methylene chloride and washed once with 200 milliliters of water, once with 200 milliliters of aqueous 2% NaOH and twice with 200 milliliters portions of water. The product layer was dried over sodium sulfate, filtered and distilled under reduced pressure at 45° C. until the solvent was removed. The resulting oil was mixed in 150 mls of n-hexane and cooled to dry ice/acetone bath temperatures. The resulting solids were filtered off and dried to give a 60% yield of O,O-bis(6-fluoro-2-pyridinyl) ethylphosphonothioate, a solid, m.p. 47°-49° C. Product was confirmed by N.M.R. and I.R. spectra (compound No. 1).

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