O=P(Cl)(Cl)[Cl:3].[CH3:6][N:7]1[C:11](O)=[CH:10][C:9]([C:13]2[CH:18]=[CH:17][CH:16]=[CH:15][N:14]=2)=[N:8]1.[C:19]([O-:22])([O-])=O.[Na+].[Na+]>CN(C=O)C>[Cl:3][C:11]1[N:7]([CH3:6])[N:8]=[C:9]([C:13]2[CH:18]=[CH:17][CH:16]=[CH:15][N:14]=2)[C:10]=1[CH:19]=[O:22]DMF (35 mL) was cooled to 0° C. in an ice bath. POCl3 (99 mL, 1059 mmol) was added dropwise followed by addition of 1-methyl-3-(pyridin-2-yl)-1H-pyrazol-5-ol (26.5 g, 151 mmol). The resulting suspension was heated at about 80° C. for about 18 h. The mixture was allowed to cool to rt then added to ice-water (2000 mL). Saturated aqueous Na2CO3 was slowly added until the solution reached a pH>7. The resulting suspension was filtered and the solids washed with H2O (200 mL). The filter cake was dissolved in DCM (500 mL), dried over Na2SO4, filtered and concentrated in vacuo to give 5-chloro-1-methyl-3-(pyridin-2-yl)-1H-pyrazole-4-carbaldehyde (21.38 g, 64%) as a yellow solid: LC-MS (Table 1, Method g) Rt=1.72 min, m/z 222 (M+H)+; 1H-NMR (DMSO, Bruker 400 MHz) δ 10.58 (s, 1H), 8.68-8.64 (m, 1H), 8.01-7.87 (m, 2H), 7.49-7.40 (m, 1H), 3.91 (s, 3H).
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