Chlorine → Ethyl 4-(4-bromophenyl)but-2-enoate

Participants

Reaction Steps

To a cold solution (-78° C.) of 15 g (62 mmol) of ethyl(4-bromophenyl)acetate (Compound A) in 150 ml of CH2Cl2 was added dropwise (over a span of 1 hour) 65 ml (65 mmol) of diisobutylaluminum hydride (DIBAL-H, 1M solution in hexane). After the DIBAL-H addition was complete, the reaction was stirred at -78° C. for an additional hour. The reaction was quenched by the dropwise addition of methanol (10 ml), followed by water (10 ml) and 10% HCl (40 ml). The mixture was then warmed to 0° C., stirred for 10 minutes and then washed with water (15 ml), 10% aqueous NaHCO3 (10 ml) and brine (10 ml). The organic phase was dried over MgSO4 and the solvent distilled off at ambient temperature to give crude (4-bromophenyl)acetaldehyde. To a cold solution (0° C.) of this crude aldehyde in 150 ml of CH2 Cl2 was added a solution of 26 g (74.6 mmol) of (carbethoxymethylene)triphenylphosphorane in 50 ml of CH2Cl2. The mixture was stirred for 16 hours, concentrated in vacuo and purified by flash chromatography (silica, 10% EtOAc-hexane) to give ethyl 4-(4-bromophenyl)but-2-enoate as a mixture of E:Z isomers. This isomeric mixture was dissolved in 150 ml of EtOAc and hydrogenated over 1 g of 10% Pd/C for 6 hours. The catalyst was filtered off and the filtrate concentrated in vacuo to give the title compound as a white solid.

Provenance & Evidence