In a 200 mL pear flask was added (R)-4-(1,2-dihydroxypropan-2-yl)-N-(1-ethyl-1H-pyrrolo[3,2-c]pyridin-6-yl)benzamide (13, 3.2 g, 7.1 mmol) in anhydrous DMF (45 ml) to give a brown suspension. At room temperature, N-chlorosuccinimide (0.94 g, 7.1 mmol) was added, and the mixture was heated to 60° C. for 4 hours. An additional 0.2 equivalent of N-chlorosuccinimide was added at room temperature. After an additional 1.5 hours of heating at 60° C., the mixture was cooled to room temperature. Brine was added, and the mixture was extracted with ethyl acetate twice. Combined organic layers were washed with brine, dried over MgSO4, filtered and concentrated until a precipitate was formed. Ether was added and the red solid was collected on a fritted filter, while the filtrate was concentrated. The oil was then purified by column chromatography (SiO2, 75-100% EtOAc/hexanes+0.25% MeOH). The product-containing fractions were combined and concentrated. The residue was combined with the red solid collected earlier and the mixture was resuspended in hot EtOAc/methanol mixture. After cooling, the much lighter-colored solid was collected on a fritted-glass filter under nitrogen, and washed with Et2O to remove most of the colored impurities to give the title compound (R)-N-(3-chloro-1-ethyl-1H-pyrrolo[3,2-c]pyridin-6-yl)-4-(1,2-dihydroxypropan-2-yl)benzamide (14, 1.7 g, 64% yield) as a light-pink solid. 1H NMR (DMSO-d6) d: 10.68 (s, 1 H), 8.60 (s, 1 H), 8.38 (s, 1 H), 8.01 (d, J=8.3 Hz, 2 H), 7.69 (s, 1 H), 7.58 (d, J=8.6 Hz, 2 H), 5.05 (s, 1 H), 4.76 (t, J=5.8 Hz, 1 H), 4.19 (q, J=7.2 Hz, 2 H), 3.40-3.50 (m, 2 H), 1.42 (s, 3 H), 1.38 (t, J=7.3 Hz, 3 H); ESI-MS: m/z 374 (M+H)+; m.p. 224.4-225.1° C.
