Hydrochloric Acid → 4-[3-(2-Ethoxycarbonyl-2-oxo-ethyl)-4-nitro-phenoxy]-piperidine-1-carboxylic acid tert-butyl ester

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Reaction Conditions

Reaction Steps

A solution of 4-(3-methyl-4-nitro-phenoxy)-piperidine-1-carboxylic acid tert-butyl ester (example 43, step 1, 41.9 g, 1.0 eq.) and diethyloxalate (18.77 mL, 1.1 eq.) in tetrahydrofuran (241.7 mL) was dropped into a cold (0-5° C.) solution of potassium tert-butylate (28.54 g, 2.0 eq.) and ethanol (43.64 mL, 6.0 eq.) in tetrahydrofuran (1.022 L). The mixture was stirred for 3 h at 0-5° C. and for 18.5 h at room temperature, poured into 1M hydrochloric acid solution. The aqueous phase was extracted 3 times with tert-butylmethylether and the combined organic phases were washed with brine, dried over sodium sulfate, filtered, evaporated to dryness in vacuo and crystallized from ethanol to yield 44.09 g (81%) as white crystals. MS (m/e): 436.2 (M, 5%).

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