Magnesium → Santalene

Participants

Reaction Steps

10 grams (0.046 moles) of π-bromotricyclene having the structure: ##STR61## prepared according to the process of Corey et al., J. Am. Chem. Soc. 79, 5773 (1957) in 500 ml of absolute diethyl ether is added to 70 g (2.9 moles) of magnesium in 100 ml of ether during 7 hours. The mixture is heated at reflux for an additional 1.5 hours. The Grignard reagent is filtered through a glass-wood plug into γ,γ -dimethylallyl mesitoate (12.8 g., 0.055 mole, b.p. 95°-100° (0.1 mm.)) in 50 ml of ether. The time required for the addition was 2 hours. The excess magnesium is rinsed with 100 ml of ether and the washing is also added to the ester. The mixture is allowed to stand at room temperature for 96 hours. At the end of this time, a fine white percipitate appears in considerable quantity. To the ether solution is added with stirring a saturated ammonium chloride solution, and stirring is continued until both aqueous and ether layers are clear. The ether solution is washed with 10% sodium hydroxide, water and dried over sodium sulfate. The crude oil (12 g) after evaporation of ether is dissolved in pentane and chromatographed on alumina. The product is eluted with pentane and distilled to give two fractions: no. 1, 1.29 g., b.p. 56°-130° (15-20 mm.), N25D 1.4496; no. 2 2.81 g, b.p. 130°-140° (15-20 mm), n25D 1.4820. The residue from the distillation which solidified is largely bi-π-tricyclyl. Fraction 2 is redistilled, dissolved in pentane and chromatographed on alumina. The eluate is distilled and yields 1.7 g of oil, b.p. 116°-120° (8 ± 2 mm.), n25D 1.4822; infrared absorption at 1670, 858 and 840 cm,- 1 ; alpha26D + 18.4° , +17.2° (pure liquid).

Provenance & Evidence