C(Cl)(=O)[C:2](Cl)=[O:3].CN(C=O)C.[CH2:12]([O:14][C:15](=[O:19])[CH:16]=[N+:17]=[N-:18])[CH3:13].CCOCC>C(Cl)(Cl)Cl>[CH2:12]([O:14][C:15](=[O:19])[C:16](=[N+:17]=[N-:18])[CH:2]=[O:3])[CH3:13]Oxalyl chloride (4.7 g, 3.1 mL, 37.0 mmol) was added to a cold (0-4° C.) solution of DMF (2.25 g, 2.4 mL, 30.8 mmol) in CHCl3 (20 mL) and stirring was continued for 10 minutes. The reaction mixture was heated at 40° C. for 10 minutes and cooled to −10° C. Diazo-acetic acid ethyl ester (3.5 g, 3.5 mL, 30.6 mmol) was then added and stirred at room temperature for 1 hr. Reaction mixture was concentrated to get the residue. Ether was then added, filtered the solid precipitated and dissolved in 10% aq HAc (10 mL) and stirring was continued for 1 hr. The reaction mixture was extracted with ether, washed with saturated sodium bicarbonate solution and brine. The organic phase was dried over Na2SO4 and concentrated under reduced pressure to afford 590 mg (21% Yield) of 2-diazo-3-oxo-propionic acid ethyl ester. 1H NMR (CDCl3): δ 9.7 (s, 1H), 4.4 (q, 2H), 1.4 (t, 3H).
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