Butanal → 2-Propyl-1,3-cyclopentanedione

To a solution of BF3.OEt2 (1.30 g, 9.2 mmol) and butyraldehyde (0.40 g, 5.5 mmol) in DCM (5 ml) under N2 at −78° was added a solution of 1,2-bis trimethylsilyloxycyclobutene (1.4 g, 6.1 mmol) in DCM (3 ml) maintaining a temperature of less than −70°. After 2 h at −78° the solution was poured into saturated NaHCO3, extracted into EtOAc, washed (brine), dried (MgSO4) and the solution concentrated in vacuo to yield a clear liquid. To this liquid was added TFA (20 ml) and the solution heated at reflux for 24 h. The solution was concentrated in vacuo and the residue purified by chromatography (SiO2, 50:50 EtOAc/hexane) to yield the title compound as an off-white solid (140 mg, 18%). δH (CD3OD) 2.46 (4H, s), 2.07 (2H, t, J 7.5 Hz), 1.40 (2H, m), 0.86 (3H, t, J 7.4 Hz). m/z (ESI, 70V) 141 (MH+).

1. temperaturemaintaining a temperature of less than −70°
2. extractionextracted into EtOAc
3. washwashed (brine)
4. dry with materialdried (MgSO4)
5. concentrationthe solution concentrated in vacuo
6. customto yield a clear liquid
7. temperaturethe solution heated
8. temperatureat reflux for 24 h
9. concentrationThe solution was concentrated in vacuo
10. customthe residue purified by chromatography (SiO2, 50:50 EtOAc/hexane)

ORD record

ord-fe864621c41f4d7eb678672b20a2110c

Source dataset

uspto-grants-2003_08

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06610700B2