Ammonium Chloride → 4-[2-(5-Bromo-2-chloro-pyridin-4-yl)-1-hydroxy-1-methyl-ethyl]-piperidine-1-carboxylic acid tert-butyl ester

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Reaction Steps

A solution of 4-[2-(5-bromo-2-chloro-pyridin-4-yl)-acetyl]-piperidine-1-carboxylic acid tert-butyl ester (9.80 g) in tetrahydrofuran (6 mL) is added dropwise to an ice cooled solution of methyl magnesium bromide (1.4 M in toluene/tetrahydrofuran 75:25, 74 mL). The reaction mixture is stirred for 30 min in the cooling bath and then at room temperature for 1 h. The mixture is poured into aqueous NH4Cl solution and extracted with ethyl acetate. The combined extracts are dried over MgSO4 and concentrated in vacuo. Since the residue still contains a considerable amount of starting material, it is azeotropically dried using toluene and resubmitted to the procedure described above. The crude product is purified by preparative HPLC (column: Waters X-Bridge C18; mobile phase: water+0.125% NH4OH/methanol 90:10→100:0) to give the title compound. LC (method 4): tR=1.33 min; Mass spectrum (ESI+): m/z=433, 435 [M+H]+.

Provenance & Evidence