[C:1]([N:4]1[C:12]2[CH:11]=[C:10]([Cl:13])[CH:9]=[C:8]([C:14]([O:16][CH3:17])=[O:15])[C:7]=2[CH:6]=[N:5]1)(=O)[CH3:2].C(=O)([O-])[O-].[Cs+].[Cs+].Br[CH:25]1[CH2:29]CC[CH2:26]1>C(#N)C>[Cl:13][C:10]1[CH:9]=[C:8]([C:14]([O:16][CH3:17])=[O:15])[C:7]2[CH:6]=[N:5][N:4]([CH:1]3[CH2:29][CH2:25][CH2:26][CH2:2]3)[C:12]=2[CH:11]=1To a stirred solution of methyl 1-acetyl-6-chloro-1H-indazole-4-carboxylate (1 equiv.) in acetonitrile (3 mL per 1 mmol), cesium carbonate (1.5 equiv.) was added followed by bromocyclopentane (2 equiv.). The reaction mixture was stirred at 90° C. for 3-4 h. On completion of reaction, acetonitrile was removed under reduced pressure and water was added. Extraction was carried out using ethyl acetate and the combined organic layers were washed with water, brine and dried over anhydrous Na2SO4. The solvent was then removed under reduced pressure and residue was purified by silica gel column chromatography to obtain methyl 6-chloro-1-cyclopentyl-1H-indazole-4-carboxylate (yield 30-35%). The structure was confirmed as the desired regioisomer by NOE.
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