Ethyl 2-oxo-3-(triphenyl-lambda~5~-phosphanylidene)propanoate → (E)-Ethyl 4-[2-(difluoromethoxy)phenyl]-2-oxobut-3-enoate

Participants

Reaction Conditions

Reaction Steps

A suspension of 2-(difluoromethoxy)benzaldehyde (295 g, 1714 mmol) and ethyl (triphenylphosphoranylidene)pyruvate (279.1 g, 742 mmol) was heated at 100° C. The dark red aldehyde immediately decolorized, and a yellow suspension was obtained, which slowly changed to a dark brown solution. 2-(Difluoromethoxy)benzaldehyde (52.5 g, 305 mmol) was added to the reaction mixture. Residual aldehyde was separated from the reaction mixture by distillation. The resulting mixture was stirred in heptane (500 mL) and diethyl ether (500 mL). The brown solid precipitate was filtered off, and washed with a 1:1 mixture of heptane and diethyl ether (3×250 mL). The filtrate was concentrated, yielding a brown oil (218.5 g). Purification by flash column chromatography (1.5 kg silica, 2-20% EtOAc in heptane, 125 mL/minute) gave the title compound (91 g) as a yellow oil. δH (CDCl3, 300 MHz) 1.42 (t, J 7.1 Hz, 3H), 4.40 (q, J 7.1 Hz, 2H), 6.59 (t, J 72.9 Hz, 1H), 7.20 (dd, J 7.3, 1.0 Hz, 1H), 7.28 (br t, J 7.6 Hz, 1H), 7.38 (d, J 16.3 Hz, 1H), 7.46 (dt, J 7.8, 1.7 Hz, 1H), 7.75 (dt, J 7.8, 1.6 Hz, 1H), 8.13 (d, J 16.3 Hz, 1H). MS [ES+] m/z 271 [M+H]+.

Provenance & Evidence