Hydrochloric Acid → 6-Methyl-6-heptenoic acid

Participants

Reaction Steps

n-Butyllithium (10.8 ml of 2.5 M in hexanes, 27 mmol, 1.3 equiv) was added to a solution of methyltriphenylphosphonium bromide (9.7 g, 27 mmol, 1.3 equiv) in dimethyl sulfoxide (50 ml) at 0° C., and the mixture was stirred at room temperature for 1 h. It was added to a solution of 6-oxo-heptanoic acid 6 (3 g, 20.82 mmol, 1 equiv) and n-butyllithium (8.33 ml of 2.5 M in hexanes, 20.82 mmol, 1 equiv) in THF (30 ml). The mixture was stirred at room temperature for 48 hr. Water was added and the mixture was acidified with 2 N HCl and extracted with methylene chloride (3×50 ml). The organic layer was washed with 10% sodium hydroxide solution. The aqueous layer was acidified with 2 N HCl and extracted with ethyl acetate (3×60 ml). The organic extracts were dried over anhydrous sodium sulfate and concentrated in vacuo. Purification by flash column chromatography (10% EtOAc/hexanes) gave pure acid 7 (2.32 g, 78%) as a colorless oil: TLC Rf=0.47 (silica gel, 25% EtOAc/hexanes); 1H NMR (600 MHz, CDCl3) δ 4.69 (s, 1H), 4.65 (s, 1H), 2.34 (t, J=7.8 Hz, 2H), 2.01 (t, J=7.8 Hz, 2H), 1.69 (s, 3H), 1.64-1.58 (m, 2H), 1.50-1.44 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 180.7, 145.6, 110.4; 37.5, 34.2, 27.1, 24.4, 22.5.

Provenance & Evidence