(+-)-alpha-Pinene → Carveol, trans-(-)-

Participants

Reaction Steps

A well stirred solution of benzoyl peroxide (24.0 g), cuprous chloride (0.2 g), cupric benzoate (1.5 g) and alpha-pinene (28.0 g) in acetonitrile (150 ml) is heated on an oil bath at 65° ± 5° for 24 hours. The acetonitrile is removed by evaporation under vacuum (water pressure) at 40°. Excess alpha-pinene is recovered by continuing the evaporation at 75° (3 mm). The resulting blue-green slurry is dissolved in 100 ml ether and the solution filtered to remove the cupric benzoate. The filtrate is washed with 2N HCl (2 × 30 ml), distilled water (3 × 30 ml) and then the ether removed by evaporation. This gives a straw colored oil which is dissolved in a solution of methanol (200 ml), water (50 ml), NaOH (10 g), and hydroylzed by refluxing 1 hour. Removal of the methanol affords an aqueous suspension which is diluted with water (100 ml) and steam distilled. The distillate is extracted with ether (4 × 20 ml). This organic solution is dried over magnesium sulphate and evaporated to yield crude trans-carveol (9.2 g). Distillation affords pure material, b.p. 106°-110°C (10 mm).

Provenance & Evidence