[Synthesis]
Under nitrogen protection, tert-butyl 3-methylpyridin-2-ylcarbamate (5.07 g, 23.6 mmol) was dissolved in 100 mL of tetrahydrofuran and the mixture was cooled to -10 °C. Under stirring, n-butyllithium (2.5 M hexane solution, 28 mL, 70 mmol) was slowly added over 15 min and the reaction solution turned dark red, and stirring was continued at -10 °C for 1 hr. Subsequently, N-methoxy-N-methylacetamide (3.80 g, 35.7 mmol) was added and the mixture was warmed to room temperature and stirred for 1 hour. Upon completion of the reaction, the mixture was cooled again to -10 °C, the reaction was quenched with 13 mL of concentrated hydrochloric acid, and then stirred at 50 °C for 90 min. After the two-phase mixture was cooled, the organic phase was separated and extracted twice with 2N hydrochloric acid. The aqueous phases were combined, alkalized to the proper pH with 32% sodium hydroxide solution and subsequently extracted three times with ethyl acetate. The organic phases were combined, washed with saturated saline, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The crude product was purified by Isolera purification system (ethyl acetate-hexane gradient, 0:100 ascending to 50:50) to afford 2-methyl-7-azaindole (2.5 g, 18.9 mmol, 80% yield) as a light yellow solid with 100% purity.1H NMR (400 MHz, CDCl3) δ ppm 2.55 (s, 3H, Me) 6.17 (s, 1H, H-3), 7.03 (dd, J = 4.9, 7.6 Hz, 1H, H-5), 7.82 (d, J = 7.4 Hz, 1H, H-4), 8.21 (d, J = 4.7 Hz, 1H, H-6), 11.96 (br.s, 1H, NH).UPLC/MS (3 min) retention time 0.68 min. LRMS: m/z 133 (M + 1). |