[Cl:1][C:2]1[C:3]([CH2:8][NH:9][C:10]([CH:12]2[CH2:17][CH2:16][C:15](=O)[CH2:14][CH2:13]2)=[O:11])=[N:4][CH:5]=[CH:6][N:7]=1.[CH3:19][N:20]1[CH2:25][CH2:24][NH:23][CH2:22][CH2:21]1.C([BH3-])#N.[Na+].C(=O)([O-])O.[Na+]>ClCCl.C(O)(=O)C>[Cl:1][C:2]1[C:3]([CH2:8][NH:9][C:10]([C@H:12]2[CH2:17][CH2:16][C@H:15]([N:23]3[CH2:24][CH2:25][N:20]([CH3:19])[CH2:21][CH2:22]3)[CH2:14][CH2:13]2)=[O:11])=[N:4][CH:5]=[CH:6][N:7]=1
To a stirred solution of N-((3-chloropyrazin-2-yl)methyl)-4-oxocyclohexanecarboxamide (40.7 mmol, 10.9 g) in dichloromethane (145 ml) and acetic acid (1.450 ml) at room temperature was added 1-methylpiperazine (52.9 mmol, 5.87 ml, 5.30 g) and sodium cyanoborohydride (81 mmol, 5.12 g). After 16 hours at room temperature dichloromethane and an aqueous saturated sodium hydrogencarbonate solution (15 mL) were added and the organic layer was separated. This organic layer was washed with brine. The aqueous layers were washed with dichloromethane twice and the combined organic extracts dried (sodium sulfate). Concentration in vacuo gave the crude product (mixture of cis and trans), which was purified using column chromatography (silica gel; dichloromethane/methanol gradient (0 to 20% methanol) to afford the cis isomer (275 mg), the trans isomer (2.5 g) and a mixture of cis and trans isomers (5.5 g).
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