2-Methylbenzaldehyde → 5-Bromo-2-methylbenzaldehyde

Participants

Reaction Steps

To a stirred solution of aluminum chloride (57.93 g, 434.46 mmol) in methylene chloride (200 mL) is added at 0° C. over 45 min o-methylbenzaldehyde (30 g, 249.69 mmol). To the resulting brown mixture is further added a methylene chloride solution (200 mL) of bromine (12.71 mL, 249.69 mmol) over 3 h and the reaction mixture is allowed to reach room temperature overnight. The reaction mixture is then poured into ice (600 g) and the aqueous layer is extracted twice with methylene chloride. The combined organic extracts are washed with a saturated aqueous solution of NaHCO3, dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The residue is taken up into hexane and the precipitate is filtered, washed with hexane (this protocol is repeated twice) and dried under high vacuum to afford the title compound as a mixture of two regioisomers: 5-bromo-2-methyl-benzaldehyde and 3-bromo-2-methyl-benzaldehyde in a 80/20 ratio: MS 197.0, 199.0 [M−H]. Rt (HPLC, Nucleosil C18, 10:90-100:0 CH3CN/H2O+0.1% TFA within 5 min, then 100% CH3CN+0.1% TFA): 5.52 min.

Provenance & Evidence