Yield:-

Reaction Conditions:

in ethanol; for 2 h;

Steps:

General procedure for the preparation of compounds 7

General procedure: Take compound 7a (R3CH3, R4Ph) for example and the othersof 7 were synthesized in the sameway. Phenylhydrazine (38 mmol)was added slowly into ethyl 2,4-dioxovalerate (45.6 mmol) inanhydrous ethanol below 5 C. Then the solution was stirredacutely for 2 h. The solvent was removed under reduced pressureand the aqueous phase was extracted with ethyl acetate. Theorganic layer was washed twice with 30 mL water and dried overanhydrous sodium sulfate, filtered and evaporated to dryness forthe next step without further purification (column chromatographywas also used when compounds 7-isomers were present).

References:

Yan, Zhongzhong;Liu, Aiping;Huang, Mingzhi;Liu, Minhua;Pei, Hui;Huang, Lu;Yi, Haibo;Liu, Weidong;Hu, Aixi [European Journal of Medicinal Chemistry,2018,vol. 149,p. 170 - 181]