[Synthesis]
General procedure for the preparation of 5-methyl-1H-pyrrolo[3,2-b]pyridine: In a microwave reactor, 5-chloro-1H-pyrrolo[3,2-b]pyridine (200 mg, 1.31 mmol), trimethylcyclotriboroxane (0.20 mL, 1.44 mmol) and potassium carbonate (540 mg, 3.93 mmol) were suspended in 5 mL of 1,2-dimethoxyethane. methoxyethane. The mixture was degassed by three vacuum-argon cycles. Subsequently, [1,1'-bis(diphenylphosphino)ferrocene]palladium(II) dichloride complex with dichloromethane (53 mg, 0.07 mmol) was added and again degassed by three vacuum-argon cycles. The reaction mixture was stirred at 120°C for 1 h under microwave radiation. After completion of the reaction, it was cooled to room temperature, diluted with ethyl acetate and water, filtered through Celite and eluted with more ethyl acetate and water. The organic phases were combined, washed with brine, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. Purification of the residue using an Isolera purification system (methanol-dichloromethane gradient, 0:100 ascending to 5:95) afforded 5-methyl-1H-pyrrolo[3,2-b]pyridine (95 mg, 0.72 mmol, 55% yield) as an oil with 96% purity. The product was confirmed by 1H NMR (300 MHz, chloroform-d): δ 8.44 (br.s, 1H), 7.60 (d, J = 8.24 Hz, 1H), 7.41 (t, J = 3.02 Hz, 1H), 7.01 (d, J = 8.24 Hz, 1H), 6.69 (br.s, 1H), 2.67 (s, 3H).UPLC/ MS (3 min) analysis showed a retention time of 0.45 min, LRMS: m/z 133 (M + 1). |