1: acetoacetic acid tert-butyl ester With acetic acid; sodium nitrite in water T=5 - 20°C; 16.33 h; 2: ethyl acetoacetate With sodium acetate; acetic acid; zinc T=60 - 85°C; 2.75 h;

1: 2-hydroxyimino-3-oxobutyric acid tert-butyl ester With zinc T=60 - 80°C; 1 h; 2: ethyl acetoacetate T=85°C; 4 h; Heating / reflux;

1: (Z)-2-hydroxyimino-3-oxo-butyric acid tert-butyl ester With zinc in water T=60 - 80°C; 1 h; 2: ethyl acetoacetate in water T=60 - 85°C; 4 h;

acetic acid; zinc

1: ethyl acetoacetate With acetic acid; zinc T=60 - 80°C; 2: t-butyl-2-hydroximino-3-oxobutyrate T=65 - 80°C; 1 h;

acetic acid; sodium nitrite Erwaermen des Reaktionsgemisches mit Acetessigsaeure-aethylester, Zink-Pulver und Essigsaeure;

1.1: hydrogenchloride / isopropyl alcohol / 25 - 50 °C 2.1: trichlorophosphate / 2 - 3 h / 0 - 50 °C 2.2: 25 - 30 °C / pH 12 - 13 3.1: potassium hydroxide; water / methanol / 4 - 6 h / 60 - 70 °C 4.1: dicyclohexyl-carbodiimide; benzotriazol-1-ol / tetrahydrofuran / 0.5 h 4.2: 16 h / 25 - 30 °C 5.1: pyrrolidine / methanol / 5 - 7 h / Reflux 6.1: ethanol / 2 - 4 h / Reflux View Scheme

1: 64 percent / TFA 2: 93 percent / aq. KOH / methanol 3: piperidine / ethanol / 60 °C View Scheme

1: 64 percent / TFA 2: 93 percent / aq. KOH / methanol 3: piperidine / ethanol / 60 °C 4: HOBt; EDC / dimethylformamide / 20 °C View Scheme

trifluoroacetic acid 2 h;