As shown in step 6-ii of Scheme 6, Compound 2022 (710 mg, 2.36 mmol) was dissolved in CCl4 (20 mL) and K2CO3 (651 mg, 4.71 mmol), NBS (461 mg, 2.59 mmol), and benzoyl peroxide (57 mg, 0.24 mmol) were added. The reaction mixture was heated to reflux for 4 hours. After cooling to room temperature, the reaction mixture was filtered and the solid washed with CCl4. The filtrate was concentrated to an oil under reduced pressure and purified by silica gel chromatography to provide methyl 2-(bromomethyl)-4-(5,6-dimethoxy-3-pyridyl)-6-methyl-benzoate (Compound 2023, 685 mg, about 70% pure). This compound was used in subsequent reactions as is.
