Ammonium Hydroxide → 5-chloro-2-ethyl-7-methyl-3H-Imidazo[4,5-b]pyridine

Participants

Reaction Conditions

Reaction Steps

A solution of 2-ethyl-7-methylimidazo[4,5-b]pyridine (28 g, 174 mmol) and m-chloroperbenzoic acid (80-90%, 44.6 g) in CHCl3 (300 mL) was heated at reflux for 0.5 hours. The mixture was concentrated and purified (SiO2, 100% CH2Cl2 gradient to 30% CH2Cl2 /MeOH) to give 29.8 g of 2-ethyl-7-methylimidazo[4,5-b]pyridine-4-oxide as a solid. 1H NMR (300 MHz, CD3OD) δ8.13 (d, 1H, J=6 Hz), 7.13 (d, 1H, J=6 Hz), 3.01 (q, 2H, J=7.5 Hz), 2.60 (s, 3H), 1.46 (t, 3H, J=7.5 Hz). A mixture of the N-oxide (29.75 g, 0.168 mol), CHCl3 (25 mL) and POCl3 (160 mL) was heated to 80° C. for 1 hours. After pouring over ice, the mixture was neutralized by careful addition of NH4OH and extracted with EtOAc. Concentration gave 23.8 g of 5-chloro-2-ethyl-7-methylimidazo[4,5-b]pyridine as a solid. 1H NMR (250 MHz, CDCl3) δ7.07 (s, 1H) 3.10 (q, 2H, J=7.5 Hz), 2.67 (s, 3H), 1.48 (t, 3H, J=7.5 Hz).

Provenance & Evidence