[NH:1]1[CH2:5][CH2:4][CH2:3][CH:2]1[CH2:6][NH2:7].[N:8]1([C:19]([O:21][C:22]([CH3:25])([CH3:24])[CH3:23])=[O:20])[CH2:13][CH2:12][CH2:11][CH:10]([C:14](OCC)=O)[CH2:9]1.C[Al](C)C.O>C1(C)C=CC=CC=1>[CH2:6]1[N:7]=[C:14]([CH:10]2[CH2:11][CH2:12][CH2:13][N:8]([C:19]([O:21][C:22]([CH3:23])([CH3:25])[CH3:24])=[O:20])[CH2:9]2)[N:1]2[CH2:5][CH2:4][CH2:3][CH:2]12
To a solution of pyrrolidin-2-ylmethanamine (250 mg, 2.5 mmol) in toluene (8.5 mL) was added 1-tert-butyl 3-ethyl piperidine-1,3-dicarboxylate (635 mg, 2.5 mmol) under nitrogen. The solution was cooled with an ice-water bath and trimethylaluminum (2M in toluene, 2.2 mL, 4.4 mmol) was added. The resulting solution was transferred to a pressure tube and heated to 110° C. for 18 h. The reaction mixture was cooled to room temperature and water was added (10 mL). The mixture was extracted with dichloromethane (40 mL×2). The combined organics were dried over sodium sulfate, filtered, and concentrated under reduced pressure. The residue was purified via flash chromatography (0-12% methanol in dichloromethane) to afford tert-butyl 3-(5,6,7,7a-tetrahydro-1H-pyrrolo[1,2-c]imidazol-3-yl)piperidine-1-carboxylate as a colorless oil (317 mg, 43.8%). MS (ES+) (M+H) 294.2; LCMS retention time: 1.03 minutes (Method M).
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