[CH2:1]([O:3][C:4]([CH:6]1[CH2:11][CH2:10][CH2:9][N:8]([C:12]([O:14][C:15]([CH3:18])([CH3:17])[CH3:16])=[O:13])[CH2:7]1)=[O:5])[CH3:2].C[Si]([N-][Si](C)(C)C)(C)C.[Na+].[Cl:29][C:30]1[CH:35]=[N:34][CH:33]=[C:32](Cl)[N:31]=1>C1COCC1>[CH2:1]([O:3][C:4]([C:6]1([C:32]2[CH:33]=[N:34][CH:35]=[C:30]([Cl:29])[N:31]=2)[CH2:11][CH2:10][CH2:9][N:8]([C:12]([O:14][C:15]([CH3:17])([CH3:16])[CH3:18])=[O:13])[CH2:7]1)=[O:5])[CH3:2]To a solution of piperidine-1,3-dicarboxylic acid 1-tert-butyl ester 3-ethyl ester (90 g, 350.1 mmol) in dry THF (180 mL) at 0° C. was slowly added sodium-bis-(trimethylsilyl)-amide (1 M in THF, 450 mL, 450 mmol). The reaction mixture was stirred at the same temperature for 0.5 hr before it was slowly added to a solution of 2,6-dichloropyrazine (60 g, 401.6 mmol) in dry THF (180 mL) under argon. The resulting reaction mixture was stirred at 0° C. for 1 hr, and then allowed to warm up to room temperature, and quenched by the addition of satd. aq. solution of NH4Cl (360 mL). The organic layer was dried over anhy. Na2SO4, filtered, and concentrated in vacuo to afford a crude title product. It was then used directly in the next step without further purification.
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