Triethyl phosphite → 2-Benzothiazolecarboxylic acid, 7-nitro-5-(trifluoromethyl)-, ethyl ester

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Reaction Steps

A suspension of 20 g (59.48 mmol) of ethyl 7-nitro-5-(trifluoromethyl)-1,3-benzothiazole-2-carboxylate-3-oxide, the synthesis of which is carried out according to a process already described in the literature (K. Wagner et al.; Chem. Ber. 106, 640-654, 1973), in 300 ml of ethanol is stirred at AT. After the addition, dropwise, of 11.22 ml (65.43 mmol) of triethyl phosphite, the reaction mixture is stirred at 70° C. for 2 hours, during which time it becomes homogeneous and yellow. Silica is then added thereto and the solvent is evaporated off under reduced pressure. The powder obtained is loaded onto a silica column. The purification is carried out using a cyclohexane/ethyl acetate mixture. The fractions of pure product are evaporated and the residue is taken up with petroleum ether, filtered, and then rinsed with a minimum amount of ethyl ether. After drying at 40° C., under reduced pressure, 16.98 g of expected compound are obtained.

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