Acetic acid, 2-(triphenylphosphoranylidene)-, ethyl ester → (3-Bromophenyl)acetaldehyde

Participants

Reaction Conditions

Reaction Steps

60 g (246 mmol) of ethyl (3-bromophenyl)acetate (Compound B1) was converted into the title compound (oil) using 255 ml (255 mmol) of diisobutyl aluminum hydride (DIBAL-H, 1M in hexane), 85.8 g (250 mmol) of (carbethoxy methylene)triphenylphosphorane and 1.7 g of 10% Pd/C. The procedure was as follows: To a cold solution (−78° C.) of Compound B1 in CH2Cl2 was added dropwise (over a span of 1 hour) the diisobutyl aluminum 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, followed by water and 10% HCl. The mixture was then warmed to 0° C., stirred for 10 minutes and then washed with water, 10% aqueous NaHCO3 and brine. The organic phase was dried over MgSO4 and the solvent distilled off at ambient temperature to give crude (3-bromophenyl)acetaldehyde. To a cold solution (0° C.) of this crude aldehyde in CH2Cl2 was added a solution of the (carbethoxy methylene)triphenylphosphorane reagent in CH2Cl2. The mixture was stirred for 16 hours, concentrated in vacuo and purified by flash chromatography (silica, 10% EtOAc-hexane) to give ethyl 4-(3-bromophenyl)but-2-enoate as a mixture of E:Z isomers. This isomeric mixture was dissolved in EtOAc and hydrogenated over 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. PMR (CDCl3): δ1.26 (3H, t, J=7.1 Hz), 1.89-2.00 (2H, m), 2.31 (2H, t, J=7.5 Hz), 2.63 (2H, t, J=7.2 Hz), 4.15 (2H, q, J=7.1 Hz), 7.10-7.35 (4H, m).

Provenance & Evidence