In a 250 mL three-necked round-bottomed flask, N-[6-[4-(5-amino-1,3,4-thiadiazol-2-yl)butyl]-3-pyridazinyl]-3-(trifluoromethoxy)benzeneacetamide (5.5 g, 12.3 mmol, 1.0 eq.) was dissolved in N,N-dimethylacetamide (44 mL, 8.0 v/v). Pyridine-2-acetic acid (2.56 g, 14.8 mmol, 1.2 equiv) was added. Propylphosphonic anhydride (50% ethyl acetate solution, 11.0 g, 17.3 mmol, 1.41 eq.) was added dropwise through the addition funnel at a rate of 5 mL/min. During the dropwise addition, the internal temperature of the reaction solution was increased from 20.1°C to 26.1°C. The reaction was typically completed after 4 h (monitored by LC/MS). Upon completion of the reaction, the reaction solution was cooled to 0°C and diluted with methyl ethyl ketone (50 mL). Water (50 mL) was added and the pH was adjusted to 6 with 2.5 N aqueous sodium hydroxide (28 mL). a yellow precipitate was collected by diafiltration and washed with isopropanol and water (1:1, 50 mL). The solid was transferred to a 100 mL round bottom flask and slurried in isopropanol and water (9:1, 50 mL). The slurry was heated to 65.1 °C and maintained for 8 h, followed by cooling to room temperature over 16 h. The slurry was then removed from the flask. An off-white precipitate was collected by filtration and washed with isopropanol (10 mL). The product was dried under high vacuum to constant weight to afford 2-(pyridin-2-yl)-N-(5-(5-(4-(6-(2-(3-(trifluoromethoxy)phenyl)acetamido)pyridazin-3-yl)butyl)-1,3,4-thiadiazol-2-yl)acetamide (CB-839) in a yield of 5.27 g (76%).1H NMR (300 MHz, DMSO-d6) δ 12.67 (s, 1H), 11.32 (s, 1H), 8.53-8.49 (m, 1H), 8.22-8.19 (d, J=9.12Hz, 1H), 7.78-7.76 (t, 1H), 7.58-7.26 (m, 7H), 4.01 (s, 2H), 3.87 (s, 2H), 3.01 (bs, 2H) , 2.90 (bs, 2H), 1.73 (bs, 4H).The XRD pattern (form B) of the free base of CB-839 is shown in Fig. 2, with characteristic peaks located at 2θ values of 3.64; 7.32; 7.92; 8.53; 9.30; 9.38; 11.02; 11.98; 14.70; 15.54; 15.87; 16.50 16.59; 18.06; 18.39; 19.10; 20.06; 20.12; 20.61; 21.37; 21.89; 22.41; 22.74; 23.72; 24.10; 24.65; 25.14; 25.78; 26.49; 27.32; 27.55; 28.26; 29.88. 31.20; 31.80; 31.52; 32.80; 34.30; 35.20; 36.41; 38.53; 40.08; 40.94; and 43.86.
