Formaldehyde → 7-(4-Bromo-2-chlorophenylamino)-8-chloro-3-piperidin-1-ylmethylimidazo[1,2-a]pyridine-6-carboxylic acid (2-hydroxyethoxy) amide

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Compound 39 was prepared by a modification of the procedure of T. Kercher et al. (manuscript in preparation). Piperidine (4 μL, 0.043 mmol) and 37% aqueous formaldehyde (5 μL, 0.065 mmol) were dissolved in 6:1 MeCN:water (0.5 ml), and stirred 30 minutes. 7-(4-bromo-2-chlorophenylamino)-8-chloroimidazo[1,2-a]pyridine-6-carboxylic acid (2-hydroxyethoxy)amide (33a) (10 mg, 0.022 mmol) was added followed by scandium triflate (1 mg, 0.002 mmol). After stirring 16 hours, additional scandium triflate (1 mg), piperidine (3.8 μL) and aqueous formaldehyde (3.8 μL) were added. After about 60 hours, the reaction mixture was diluted with EtOAc and washed with water, 10% K2CO3, and brine. The organic layer was dried (Na2SO4) and concentrated. Purification by flash column chromatography using the Biotage system (40:1 CH2Cl2/MeOH to 20:1 CH2Cl2:MeOH to 9:1 CH2Cl2/MeOH) provided the desired product (39) as a white solid (6 mg, 50%). MS APCI (+) m/z 556, 558, 560 (M+, Cl, Br pattern) detected. 1H NMR (400 MHz, CD3OD) δ 8.83 (s, 1H), 7.56 (s, 1H), 7.54 (s, 1H), 7.27 (dd, 1H), 6.56 (d, 1H), 3.91 (m, 4H), 3.70 (m, 2H), 2.51 (broad s, 4H), 1.60 (broad s, 4H), 1.50 (broad s, 2H).

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