C(Cl)(=O)C(Cl)=O.CS(C)=O.[Br:11][C:12]1[CH:17]=[CH:16][N:15]=[C:14]([CH2:18][OH:19])[C:13]=1[CH3:20].C(N(CC)CC)C>C(Cl)Cl>[Br:11][C:12]1[CH:17]=[CH:16][N:15]=[C:14]([CH:18]=[O:19])[C:13]=1[CH3:20]To a stirred and cooled (−78° C.) solution of oxalyl chloride (2.82 mL, 33.37 mmol) in DCM (70 mL) under nitrogen was added dropwise a solution of dimethyl sulfoxide (5.17 mL, 72.81 mmol) in DCM (10 mL). Stirring was continued for 10 minutes. A solution of (4-bromo-3-methyl-2-pyridyl)methanol (which may be prepared as described in Description 6) (6130 mg, 30.34 mmol) in DCM (35 mL) was then added dropwise over 20 minutes. The reaction was then allowed to stir for 1 hour. Triethylamine (18.98 mL, 136.53 mmol) was then added dropwise and the reaction was allowed to warm to room temperature over 1.5 hours. The reaction was then quenched by addition of water (approximately 100 mL). The organics were separated and washed with additional water (150 mL). The organics were dried using a hydrophobic frit and concentrated in vacuo to give 4-bromo-3-methyl-pyridine-2-carbaldehyde (D7) (5.709 g, 28.541 mmol, 94.1% yield) as a brown oil which crystallised on standing.
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