Hydrochloric Acid → Ethyl 4-oxo-4-(4-pyridyl)butyrate

Participants

Reaction Steps

Carbonyldiimidazole (7.25 g) was added to a solution of 4-pyridinecarboxylic acid (5.00 g) in tetrahydrofuran (80 ml) at 0° C. After stirring at room temperature for 2 hours, the mixture was added dropwise to a solution of lithiated tert-butyl acetate prepared from tert-butyl acetate (17.5 ml) and lithium diisopropylamide (2N tetrahydrofuran solution, 65 ml) at −78° C. over 1 hour. After stirring for 15 minutes, 1N hydrochloric acid (250 ml) was added and extracted with ethyl acetate. The ethyl acetate layer was washed with an aqueous saturated solution of sodium chloride, dried (MgSO4) and concentrated. The residue was subjected to silica gel chromatography to obtain an oil from an ethyl acetate-hexane (2:3, v/v)-eluted fraction. This oil was dissolved in tetrahydrofuran (100 ml), and sodium hydride (60% in oil, 1.16 g) was added at 0° C., and then the resultant reaction mixture was stirred for 10 minutes. Ethyl bromoacetate (2.88 ml) was added to the mixture, and the resultant mixture was stirred at room temperature for 24 hours, 0.1N hydrochloric acid (300 ml) was added and extracted with ethyl acetate. The ethyl acetate layer was washed with an aqueous saturated solution of sodium chloride, dried (MgSO4) and concentrated. The residue was subjected to silica gel chromatography to obtain an oil from an ethyl acetate-hexane (1:1, v/v)-eluted fraction. This oil was dissolved in toluene (120 ml), and stirred with trifluoroacetic acid (5.64 ml) at 90° C. for 6 hours. An aqueous saturated solution of sodium bicarbonate was added to the reaction mixture and extracted with ethyl acetate. The ethyl acetate layer was washed with an aqueous saturated solution of sodium chloride, dried (MgSO4) and concentrated. The residue was subjected to silica gel chromatography to obtain ethyl 4-oxo-4-(4-pyridyl)butyrate (2.61 g, yield 31%) from an ethyl acetate-hexane (2:1, v/v)-eluted fraction as a pale brown oil.

Provenance & Evidence