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0 °C

To a solution of 4-hydroxyamino-1-methoxy-piperidine-4-carbonitrile (preparation example 11, step 2) (4.0 g, 23.4 mmol) and sodium hydrogen carbonate (3.0 g, 35.7 mmol) in ethyl acetate (35 ml) and water (25 ml) at 0° C. was added a solution of (2,5-dimethyl-phenyl)-acetyl chloride (4.2 g, 23.0 mmol) in ethyl acetate (35 ml) dropwise over one hour. The reaction mixture was stirred at 0° C. for one hour and at room temperature for two hours. The layers of the biphasic system were separated, the aqueous phase extracted with ethyl acetate (3×), the combined organic layers washed with brine, dried over sodium sulfate and concentrated. The oily residue was purified by chromatography on silica gel (gradient ethyl acetate/hexane 1:2→1:1→2:1). Yield: 1.55 g of N-(4-cyano-1-methoxy-piperidin-4-yl)-2-(2,5-dimethyl-phenyl)-N-hydroxy-acetamide (compound P3ii.2) as a white solid, mp 153-156° C.

1. customThe layers of the biphasic system were separated
2. extractionthe aqueous phase extracted with ethyl acetate (3×)
3. washthe combined organic layers washed with brine
4. dry with materialdried over sodium sulfate
5. concentrationconcentrated
6. customThe oily residue was purified by chromatography on silica gel (gradient ethyl acetate/hexane 1:2→1:1→2:1)