Ethyl Bromide → n-Butyl 2-hydroxy-7-methyl-3-octynoate

Participants

Reaction Conditions

Reaction Steps

A Grignard reagent was prepared under dry nitrogen by the addition, over a 1 hour period, of a solution comprising 10.9 grams (g) (0.10 mole) of ethyl bromide is 15 milliliters (ml) of anhydrous ether to a stirred suspension of 2.4 g (0.10 g atom) of clean magnesium metal turnings in 70 ml of dry ether. Stirring at 25° C. was continued for an additional hour and then a solution of 9.6 g (0.10 mole) of 5-methyl-1-hexyne in 15 ml of dry ether was added during 30 minutes with stirring. The resulting greyish solution was then heated at reflux for 2 hours and cooled to room temperature. The solution was transferred under dry nitrogen to a 200 ml addition funnel, followed by flushing with two 15 ml portions of dry ether. This solution was then added over a 45 minute period to a stirred solution of 13.0 g (0.10 mole) of n-butyl glyoxalate in 70 ml of dry ether cooled to -20° C. The mixture was stirred at -20° C. for 2 hours and allowed to warm to room temperature overnight. The resulting yellow-orange solution was cautiously treated with 75 ml of saturated ammonium chloride solution and after stirring for 5 minutes, the two phases which formed were separated. The aqueous phase was extracted twice with 60 ml portions of ether and the combined organic phases were washed with three 75 ml portions of brine and dried over MgSO4. After filtration and concentration at the stripper, the residual reddish-orange oil (18.0 g.), was fractionated through a 15 cm Vigreux column to afford, after a small forerun, a single volatile fraction, boiling point (b.p.) 107.0°-117.0° C./0.20 millimeter (mm). Redistillation of this cut provided 10.3 g (41% yield) of n-butyl 2-hydroxy-7-methyl-3-octynoate as a light yellow, sweet smelling, mobile oil, b.p. 112.0°-115.0° C./0.20 mm.

Provenance & Evidence