[Cl:1][C:2]1[CH:3]=[C:4]([NH:9][C:10]([C:12]2[C:16]([CH:17]=O)=[N:15][O:14][N:13]=2)=[O:11])[CH:5]=[CH:6][C:7]=1[F:8].[NH2:19][C:20]1[NH:24][N:23]=[N:22][N:21]=1.S([O-])([O-])(=O)=O.[Na+].[Na+].[BH4-].[Na+].[BH4-].[Li+]>C1COCC1.[OH-].[Na+].C(O)(=O)C>[Cl:1][C:2]1[CH:3]=[C:4]([NH:9][C:10]([C:12]2[C:16]([CH2:17][NH:19][C:20]3[NH:24][N:23]=[N:22][N:21]=3)=[N:15][O:14][N:13]=2)=[O:11])[CH:5]=[CH:6][C:7]=1[F:8]
To a solution of N-(3-chloro-4-fluorophenyl)-4-formyl-1,2,5-oxadiazole-3-carboxamide (4.5 g, 17 mmol) in THF (75 mL) was added 5-aminotetrazole (4.26 g, 50.1 mmol), sodium sulfate (1.0 g, 8.0 mmol) and acetic acid (50 μL, 0.80 mmol). The resulting mixture was stirred at 40° C. for 36 h, and then an additional 20 mL THF was added followed by sodium tetrahydroborate (947 mg, 25 mmol). After stirring for 3 h, lithium tetrahydroborate (545 mg, 25.0 mol) was added to the reaction solution and stirred overnight. The reaction solution was diluted with 1 N NaOH solution. The aqueous layer was separated and acidified with 6 N HCl to pH 1. A white solid precipitated out of solution and was filtered to afford the desired product (4.82 g, 85%). LCMS for C11H9ClFN8O2(M+H)+: m/z=339.0.
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