[N+:1]([C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][C:5]=1[CH2:10][C:11](=[O:15])C(O)=O)([O-:3])=[O:2].N1CCOCC1.CC1C=CC(S(O)(=O)=O)=CC=1>O1CCOCC1>[N+:1]([C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][C:5]=1[CH2:10][CH:11]=[O:15])([O-:3])=[O:2]To a solution of 2-Nitrophenylpyruvic acid (1.3 g, 6.22 mmol) in dry dioxane 12 mL was added morpholine (1.5 ml, 17.23 mmol) and a catalytical quantity of p-TSA. Then the resulting mixture was firstly sonicated and then heated in microwave conditions at 120° C. for 30 min. Dioxane was evaporated at reduced pressure and the crude vigourously stirred in 1/1 EtOAc/H2O (10 mL) overnight. The organic layer was separated and the aqueous phase washed with EtOAc (×2). The combined organic layer was dried over Na2SO4 anhydrous and solvent was removed at reduced pressure. Finally, the crude product was purified by flash chromatography on silica (ETP to 1:1 ETP/EtOAc) to obtain the titled compound (3.34 g, yield 64%).
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