[I:1][C:2]1[CH:3]=[CH:4][C:5]([CH3:11])=[C:6]([CH:10]=1)[C:7](O)=[O:8].O1CCCC1.B.ClCCl>O1CCCC1.O=[Mn]=O>[I:1][C:2]1[CH:3]=[CH:4][C:5]([CH3:11])=[C:6]([CH:10]=1)[CH:7]=[O:8]To a solution of 5-iodo-2-methyl benzoic acid (24 g, 91 mmol) (AKSCI) in anhydrous tetrahydrofuran (100 mL) at 0° C. was added borane tetrahydrofuran (1 M, 250 mL, 250 mmol) dropwise. The reaction mixture was then stirred at room temperature for 2 h. The mixture was concentrated and residue was partitioned between ethyl acetate and water. Organic layer was separated, washed with brine, dried over MgSO4, and concentrated to give an off-white solid. The solid was dissolved into dichloromethane (300 mL), and activated MnO2 (20 g) was added. The mixture was then heated at reflux for 4 h, cooled to room temperature, and filtered through a short pad of celite. The filtrated was concentrated and purified by chromatography (EtOAc:hexanes=1;8) to give 5-Iodo-2-methyl-benzaldehyde as an off-white solid (Yield 5.5 g, 25%).
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