4-Methylbenzaldehyde → Methyl 2-(4-methylbenzylidene)-3-oxobutanoate

Participants

Reaction Steps

A solution of 4-methylbenzaldehyde (0.981 ml, 8.32 mmol), methyl acetoacetate (0.898 ml, 8.32 mmol), piperidine (0.041 ml, 0.416 mmol), and acetic acid (0.024 ml, 0.416 mmol) in benzene (12.5 ml) was refluxed with a Dean Stark apparatus for 1 day. The reaction was concentrated; the residue was dissolved in EtOAc, washed with water, sat. NaHCO3, Brine, dried with Na2SO4, filtered, and concentrated. Purification with column chromatography afforded a 2:3 mixture of E/Z isomers of methyl 2-(4-methylbenzylidene)-3-oxobutanoate (1539.1 mg, 7.05 mmol, 84.7% yield) as yellow oil: E=1H NMR (400 MHz, CHLOROFORM-d) d=7.67 (s, 1 H), 7.29 (d, J=8.2 Hz, 2 H), 7.18 (d, J=8.1 Hz, 2 H), 3.83 (s, 3 H), 2.37 (s, 3 H), 2.36 (s, 3 H) LCMS (m/z) ES+=219 (M+1). Z=1H NMR (400 MHz, CHLOROFORM-d) d=7.55 (s, 1 H), 7.33 (d, J=8.2 Hz, 2 H), 7.20 (d, J=8.1 Hz, 2 H), 3.86 (s, 3 H), 2.42 (s, 3 H), 2.38 (s, 3 H); LCMS (m/z) ES+=219 (M+1).

Provenance & Evidence