Trimethyl phosphite → (4-methylsulfanyl-benzyl)-phosphonic acid dimethyl ester

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Reaction Steps

First, dimethyl (4-methylthiobenzyl)phosphonate was synthesized, as follows: Trimethylphosphite (206 g, 1.66 mol) was stirred at reflux, and 245 g (1.42 mol) of 4-methylmercaptobenzyl chloride (prepared as described in Ulman, et al. U.S. Pat. No. 4,792,208, Example 1) was added dropwise over 30 min. The mixture was kept at reflux for 4 hours, and then cooled to room temperature. Dimethyl (4-methylthiobenzyl)phosphonate was obtained by fractional distillation at reduced pressure. The yield was 263 grams, which is 75% of theoretical.

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