Boron tribromide → 3-[8-(Cyclopentylamino)-3-[2-(cyclopentylamino)pyrimidin-4-yl]imidazo[1,2-a]pyridin-2-yl]phenol

To a cold (−78° C.) solution of formed N-cyclopentyl-3-[2-(cyclopentylamino)-4-pyrimidinyl]-2-(3-methoxyphenyl)imidazo[1,2-α]pyridin-8-amine (42 mg, 0.09 mmol) in dichloromethane (5 mL) was added boron tribromide (0.5 mL, 1 M in dichloromethane, 0.5 mmol) dropwise. The solution was allowed to warm to room temperature over 4 hours and stirred for an additional 16 hours. The reaction was quenched by the addition of methanol followed by saturated aqueous sodium bicarbonate. Ether was added and the layers separated. The organic layer was washed with brine. The aqueous layer was extracted with ether and the combined organics were dried over magnesium sulfate. Filtration and concentration followed by flash chromatography (1:1 hexanes:ethyl acetate) provided 3-{8-(cyclopentylamino)-3-[2-(cyclopentylamino)-4-pyrimidinyl]imidazo[1,2-α]pyridin-2-yl}phenol (30 mg, 73%) as a yellow solid. 1H NMR (CDCl3): δ 8.90 (broad, 1H), 7.96 (d, 1H), 7.31 (s, 1H), 7.17 (t, 1H), 7.01 (d, 1H), 6.81–6.75 (m, 2H), 6.38 (d, 1H), 6.27 (d, 1H), 5.53 (d, 1H), 5.28 (d, 1H), 4.30 (m, 1H), 3.88 (m, 1H), 2.10–1.93 (m, 4H), 1.78–1.48 (m, 12H); MS m/z 455 (M+1).