Diethyl Oxalate → (3-tert-Butoxycarbonylamino-pyridin-4-yl)-oxo-acetic acid ethyl ester

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Reaction Conditions

Reaction Steps

(3-tert-Butoxycarbonylamino-pyridin-4-yl)-oxo-acetic acid ethyl ester was prepared according to a procedure described by Estel, etc (J. Heterocycl. Chem., 1989, 26, 105-): To a solution of pyridin-3-yl-carbamic acid tert-butyl ester (8.50 g, 43.8 mmol) and TMEDA (16.5 mL, 109 mmol) in THF (200 mL) at −78° C. was cannulated tert.-BuLi (64.1 mL, 1.7 M in pentane) over 30 min under nitrogen. The mixture was then stirred for 2 hours between −10° C. and −20° C. After cooling to −60° C. diethyl oxalate (17.8 mL, 131 mmol) was added and the mixture allowed to warm to 0° C. After 3 hours the mixture was poured onto ice/1M HCl (120 mL) and extracted with ethyl acetate (3×150 mL). The combined organic extracts were washed with water (100 mL), brine (75 mL), dried over MgSO4 and concentrated. The residue was purified by flash column chromatography (gradient, hexane/ethyl acetate 5:2, 2:1), to give 3.04 g (24% yield) of compound 146 as a yellow oil.

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