Sulfuric acid magnesium salt (1:1) → 2-(Butyl-hydrazono)-3-methyl-butyric acid ethyl ester

To a solution of 3-Methyl-2-oxo-butyric acid ethyl ester (1c) (1.88 g, 13.04 mmol) in 45 mL of CHCl3, butyl-hydrazine oxalate salt (2.11 g, 11.85 mmol) was added followed by NaOAc (1.94 g, 23.4 mmol) and MgSO4 (1.43 g, 11.88 mmol). The mixture was heated to reflux for 3.5 hours under N2 atmosphere with stirring. After cooling, the solid was filtered off and the filtrate was concentrated under reduced vacuum. The residue was first cleaned by an extraction between EtOAc (50 mL×3) and H2O (20 mL). The organic layer was concentrated under reduced pressure and dried under high vacuum overnight to give 2.17 g of the crude product (3b) in 85.4% yield as a mixture of the E- and Z-isomers. This crude product was directly used in the next step without further purification. LC-MS (ESI+): m/e=215.4 [M+1]+, 237.1 [M+Na]+ (exact ms: 214.17).

1. temperatureThe mixture was heated
2. temperatureto reflux for 3.5 hours under N2 atmosphere
3. temperatureAfter cooling
4. filtrationthe solid was filtered off
5. concentrationthe filtrate was concentrated under reduced vacuum
6. extractionThe residue was first cleaned by an extraction between EtOAc (50 mL×3) and H2O (20 mL)
7. concentrationThe organic layer was concentrated under reduced pressure
8. customdried under high vacuum overnight

ORD record

ord-70c49ef884364b058510702980cfeff3

Source dataset

uspto-grants-2008_09

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07425552B2