Boron trifluoride etherate → 2-(5-iodo-1H-indol-3-yl)-N,N-dimethyl-acetamide

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To a suspension of 2-(5-iodo-3-hydroxy-2-oxo-2,3-dihydro-1H-indol-3-yl)-N,N-dimethyl-acetamide (Example 6) (36.0 g, 0.1 mol) in DME (250 mL), at 20° C. boron trifluoride etherate (28.3 g, 0.2 mol) is added. Under cooling with an ice bath, borane dimethyl sulfide complex (12.0 g, 0.15 mol) is added during 10 minutes, and then the cooling bath is removed. The temperature rises slowly to 55° C., and a suspension forms at about 50° C. When the exothermic reaction has subsided, the mixture is stirred at 75° C. for another 30 minutes, and then quenched by adding 4 N NaOH (100 mL). The mixture is heated under reflux for another 30 minutes, and then filtered while still hot. Removal of the solvent on the rotavapor leads to crystallization of the product, which goes to completion on standing in the refrigerator for 12 hours. The product is filtered off, washed with cold acetone (50 mL, −20° C.) and pentane, and dried to give the title product (24.8 g, 75%) as crystals, mp.=195-200° C. 1H-NMR (DMSO-D6, 300 MHz) δ 2.80, 2.99 (2 s, 3H each, N(CH3)2); 3.69 (s, 2H, CH2); 7.19 (d, 1H, 3J=2.4 Hz, H-2); 7.21 (d, 1H, 3J=8.5 Hz, H-7); 7.32 (dd, 1H, 4J=1.7 Hz, H-6); 7.92 (d, 1H, H-4); 11.04 (br s, 1H, NH). 13C-NMR (DMSO-D6, 75 MHz) δ 31.11 (CH2); 35.70, 37.91 (N(CH3)3); 82.82 (C-5); 108.54 (C-3); 114.51 (C-7); 125.46 (C-2); 128.16 (C-4); 129.54 (C-6); 130.85 (C-9); 135.91 (C-8).

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