In a
dry 500-ml. three-necked flask, equipped with a
reflux condenser, a
mechanical stirrer, and a
dropping funnel and protected from atmospheric moisture with drying tubes, are placed
6.0 g. (0.16 mole) of lithium aluminum hydride and
200 ml. of anhydrous ether. A solution of
43 g. (0.307 mole) of 3-ethoxy-2-cyclohexenone (Note
1) in
50 ml. of anhydrous ether is added, dropwise and with stirring, to the reaction flask at a rate which maintains gentle refluxing of the solvent (Note
2). After the addition is complete, the reaction solution is boiled under reflux for an additional 30 minutes and then allowed to cool. The complex is hydrolyzed and the excess
lithium aluminum hydride is destroyed by the cautious addition, dropwise and with stirring, of 15 ml. of water (Note
3). The resulting reaction mixture is poured into
500 ml. of cold aqueous 10% sulfuric acid. The
ether layer which forms is separated, and the residual aqueous phase is extracted with three
300-ml. portions of ether. The combined
ether solutions are washed successively with one 100-ml. portion of water and one
100-ml. portion of saturated, aqueous sodium bicarbonate solution and then dried over
magnesium sulfate. The
ether is removed by distillation through a
50-cm. Vigreux column, and the residue is distilled under reduced pressure through a
40-cm. spinning-band column (Note
4). The yield of
2-cyclohexenone (Note
5), b.p.
56–57.5°/10 mm. or
96–97°/72 mm.,
nD27 1.4858, is
18.2–22.1 g. (
62–75%).