[CH3:1][C:2]1[CH:3]=[C:4]([CH:15]=[C:16]([CH3:18])[CH:17]=1)[CH2:5][O:6]C(=O)C1C=CC=CC=1.C1C(=O)N([Br:26])C(=O)C1>C(Cl)(Cl)(Cl)Cl.[W]>[Br:26][CH2:1][C:2]1[CH:3]=[C:4]([CH:15]=[C:16]([CH3:18])[CH:17]=1)[CH:5]=[O:6]A mixture of benzoic acid 3,5-dimethyl-benzyl ester (24 g, 0.1M) and NBS (39.16 g, 0.22M) in carbon tetrachloride (200 ml) was refluxed for 3 hr. under a light of 500 W tungsten lamp. After cooling to room temperature, the mixture was filtered and the filtrate was evaporated in vacuo. The residue was dissolved in ether, washed with aqueous saturated sodium bicarbonate solution, dried with anhydrous magnesium sulfate, filtered, and evaporated in vacuo to give 21 g of crude 3-bromomethyl-5-methyl-benzaldehyde.
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