Bromine → HCID 86691330, compound

Participants

Reaction Conditions

Reaction Steps

To a stirred suspension of E-2,6-difluorocinnamic acid (2.0 g, 11 mmol) in dichloromethane at 0° C. is added bromine (0.56 mL, 11 mmol) dropwise. The mixture is stirred overnight as it is slowly allowed to reach temperature. Evaporation of the volatiles under reduced pressure affords the crude dibrominated carboxylic acid intermediate that is directly carried to the next step without further purification. To the crude solid is added DMF (20 mL) and a small crystal of BHT. The mixture is cooled to 0° C., and triethylamine (3 mL) is added. The mixture is stirred overnight as it is slowly allowed to reach temperature. Contents are poured in 2N aqueous HCl, extracted with diethyl ether, and the combined organic fractions are washed with saturated aqueous NaCl. Evaporation of the volatiles yields a crude product that is further purified by passing on a SiO2 plug using pentane as an eluent. Evaporation of the solvents under reduced pressure affords bromoalkene 11q as a colorless oil (1.35 g, 57%, ≧20:1 d.r. by 19F-NMR). 1H-NMR (CDCl3, 300 MHz): δ=7.42-7.32 (m, 1H), 7.07 (d, J=7.9 Hz, 1H), 7.05-6.95 (m, 2H), 6.84 (d, J=7.9 Hz, 1H). 13C-NMR (CDCl3, 75 MHz): δ=159.9 (dd, J=250, 7 Hz), 130.0 (t, J=10 Hz), 122.3, 114.8, 130.0 (t, J=20 Hz), 111.5 (dd, J=18, 7 Hz). 19F-NMR (CDCl3, 282 MHz): δ=−108.5. HR-MS (EI): Calcd. for C8H5F2Br [M+]: 217.9543. found 217.9538.

Provenance & Evidence