To SO3-pyr complex (0.320 g, 2.01 mmol) was added pyridine (0.16 mL, 2.02 mmol) and DMSO (0.36 mL, 5.07 mmol). Slurry was stirred at room temperature 10 min before DCM (2.0 mL) was added and mixture was cooled to 0° C. Then solution of methyl 5-ethyl-6-(2-(hydroxymethyl)imidazo[1,2-a]pyridin-6-yl)-2-methoxynicotinate (0.346 g, 1.01 mmol), Hunig's base (0.60 mL, 3.44 mmol) and DMSO (0.36 mL, 5.07 mmol) in DCM (4.0 mL) was added dropwise. Reaction mixture was stirred at 0° C. 30 min and LC/MS showed complete consumption of starting material. DCM was removed under reduced pressure and residue was treated with H2O (10 mL). Solid which was formed was collected by filtration affording methyl 5-ethyl-6-(2-formylimidazo[1,2-a]pyridin-6-yl)-2-methoxynicotinate (0.270 g) in 79% yield.
