The solution of tert-butyl 2-methyl-1H-pyrrolo[2,3-b]pyridine-3-carboxylate (1.0 g, 4.31 mmol), 2-bromopentan-3-one (1.1 g, 6.46 mmol), Cs2CO3 (2.8 g, 8.61 mmol), KI (142.9 mg, 0.86 mmol) in CH3CN (4 ml) were stirred at 70° C. for 2 h. After the reaction completed, the solution was cooled to r.t. and filtered off. The filtration was evaporated under vacuum. The residue was purified by flash column (Eluent: PE:EtOAc=5:1) to get tert-butyl 2-methyl-1-(3-oxopentan-2-yl)-1H-pyrrolo[2,3-b]pyridine-3-carboxylate as a white oil. (100 mg yield 7%)
