4-Fluoro-3-nitrobenzotrifluoride → Methyl (5-chloro-2-methoxyphenyl)(fluoro)[2-nitro-4-(trifluoromethyl)phenyl]acetate

Participants

Reaction Conditions

Reaction Steps

A four-necked 12-L round-bottomed flask, equipped with a septa, mechanical stirrer, argon inlet, thermocouple and 2-L addition funnel capped with a septa, was argon purged. The 5-chloro-2-methoxyphenylacetic acid, methyl ester from Example 1 (309.15 g, 1.44 mol) and 4-fluoro-3-nitro-benzotrifluoride (207.5 mL, 310.0 g, 1.48 mol) were transferred into the flask via a cannula and dissolved in anhydrous THF (750 mL). The clear light yellow solution was cooled in an acetone/dry ice bath to approximately -20° C. A solution of lithium hexamethyldisilazane in THF (1.0 N, 3.16 L, 3.16 mol; dark orange-yellow in color) was transferred to the addition funnel and then added to the reaction mixture over a total of 1.5 hours. The internal temperature of the reaction mixture was maintained between -26° and -16° C. HPLC analysis after 10 minutes showed the reaction was complete. After a total of 40 minutes from the time of complete addition of lithium hexamethyldisilazane, a solution of N-fluoro-bis (phenylsulfonyl) amine (NFSi) (Accufluor198) (467.1 g, 1.48 mol, pink in color, Allied Signal, Buffalo Research Lab, 20 Peabody Street, Buffalo, N.Y.) in anhydrous THF (1.25 L) was cannulated into the reaction mixture over 20 minutes. The temperature of the reaction mixture was maintained at about -10° C. during the exothermic addition of the N-fluoro-bis(phenylsulfonyl)amine (Accufluor198) solution. The cooling bath was removed and the reaction mixture was allowed to warm to about 0° C. over about 1 hour, and HPLC analysis showed the reaction was complete. The reaction mixture was quenched with acetic acid (200 mL) resulting in an exotherm to 40° C., precipitation of the N-fluorobenzenesulfonide (Accufluor198) by-product and a color change from dark reddish-brown to orange. The mixture was diluted with water (4 L) and extracted with ethyl acetate (2×4 L). The combined organic layer was washed with 10% sodium carbonate (4×4 L), 50% saturated sodium chloride solution (1×4 L), 0.5 N HCI (1×4 L) and saturated sodium chloride solution (1×4 L). The first two base washes, the 50% saturated sodium chloride solution wash and the HCI wash were back-extracted with ethyl acetate (2 L) and this organic layer was washed with saturated sodium chloride solution (1 L). The combined organic layers were then concentrated under vacuum at about 35° C. on a rotary evaporator to afford a semi-solid black residue (87% by HPLC). The residual oil was azeotropically dried with ethanol (2×500 mL) to remove water and ethyl acetate before crystallization. A 5-L flask equipped with a mechanical stirrer was charged with this residue and dissolved in ethanol (1.5 L) while stirring and heating in a boiling water bath. Heptane (2.6 L) was slowly added and the hot water bath was removed. The solution was allowed to slowly cool to room temperature (over 2 hours) to crystallize the product. After stirring for 16 hours, the suspension was cooled to 0° C. and stirred for 2.5 hours. The cold suspension was filtered, washed with cold 1:1 ethanol/heptane (1 L). The solid was air dried for about 2 h and then vacuum dried to afford 478.2 g of the title compound (78.8% yield, 99.3% by HPLC) as an off-white-peach colored solid.

Provenance & Evidence