[F:1][C:2]1([F:14])[CH2:6][NH:5][C@H:4]([CH2:7][C:8](=[O:13])[CH:9]=[C:10]([CH3:12])[CH3:11])[CH2:3]1.C([O-])([O-])=O.[K+].[K+]>CO>[F:14][C:2]1([F:1])[CH2:6][N:5]2[C@H:4]([CH2:7][C:8](=[O:13])[CH2:9][C:10]2([CH3:11])[CH3:12])[CH2:3]1A MeOH (350 ml) solution of 1-((R)-4,4-difluoropyrrolidin-2-yl)-4-methylpent-3-en-2-one and K2CO3 (2.5 g, 18 mmol) was stirred at 40° C. for 15 hours, the reaction went to completion as monitored by LC-MS. Solvent was removed in vacuo, remaining material was suspended in CH2Cl2, solid was filtered off, filtrate was collected and solvent was removed in vacuo. Product was purified by silica gel chromatography (Hexane/EtOAc, linear gradient from 100:0 to 80:20). Compound (R)-2,2-difluoro-hexahydro-5,5-dimethylindolizin-7(1H)-one was obtained as a light yellow solid: 637.4 mg (69% yield over 3 steps).
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